The sunn Forum

Sunn Musical Equipment => Q & A => Topic started by: rp on September 18, 2006, 07:45:43 pm

Title: 1200S for a bass rig
Post by: rp on September 18, 2006, 07:45:43 pm
Hi, I was thinking of using a 1200S for a bass head with an Ibanez bass w/active pickups.
For cabs I have a hartke 4x10 400watts and a hartke 1x15 at 150 watts, both at 8 ohms.
Can I do this? Any forseeable problems? Which tubes should I replace with?

thanks.

ps..I'm referring to the vintage (68) 1200S.
Title: Re: 1200S for a bass rig
Post by: EdBass on September 19, 2006, 05:55:23 pm
I sometimes use a Hartke 410 XL with a 200S or 2000S head and they sound much better than I think they should. Impressively loud with the 60 watter, and plenty of stage volume with the 2000S considering the relatively inefficient Hartke drivers. When I use an active bass however I've got to watch the basses output level or it gets kinda nasty sounding fast. I bet it would sound pretty good with both Hartke cabs at an 4 ohm total load on your old beast.
Title: Re: 1200S for a bass rig
Post by: rp on September 19, 2006, 06:07:40 pm
I sometimes use a Hartke 410 XL with a 200S or 2000S head and they sound much better than I think they should. Impressively loud with the 60 watter, and plenty of stage volume with the 2000S considering the relatively inefficient Hartke drivers. When I use an active bass however I've got to watch the basses output level or it gets kinda nasty sounding fast. I bet it would sound pretty good with both Hartke cabs at an 4 ohm total load on your old beast.
Thanks, I wish I could find a 2000S for my bass, but no luck as of yet. I'm guessing I should plug the 410xl into the first jack, or does it matter?
I have a gallien kruger 800rb on them now, but it sounds so wimpy and I can hardy get a good overdrive without using
a bass POD rat channel...or Pi -type channel. That's solid state though I guess.

Guitar cabinet wise I was gonna run the 1200S through a 4x12 marshall cab (8 ohms 120RMS)...is this too small a cab?
I have a 120 watt solid state marshall head on it now, and it has hardly any bottom whatsoever. Should I mix any solid state effects
for guitar or bass with it.  thanks

Title: Re: 1200S for a bass rig
Post by: EdBass on September 20, 2006, 08:18:49 pm
I sometimes use a Hartke 410 XL with a 200S or 2000S head and they sound much better than I think they should. Impressively loud with the 60 watter, and plenty of stage volume with the 2000S considering the relatively inefficient Hartke drivers. When I use an active bass however I've got to watch the basses output level or it gets kinda nasty sounding fast. I bet it would sound pretty good with both Hartke cabs at an 4 ohm total load on your old beast.
Thanks, I wish I could find a 2000S for my bass, but no luck as of yet. I'm guessing I should plug the 410xl into the first jack, or does it matter?
I have a gallien kruger 800rb on them now, but it sounds so wimpy and I can hardy get a good overdrive without using
a bass POD rat channel...or Pi -type channel. That's solid state though I guess.

Guitar cabinet wise I was gonna run the 1200S through a 4x12 marshall cab (8 ohms 120RMS)...is this too small a cab?
I have a 120 watt solid state marshall head on it now, and it has hardly any bottom whatsoever. Should I mix any solid state effects
for guitar or bass with it.  thanks



The 2 speaker jacks in the back of a 1200S are either wired for 8 & 4 ohm, or 8 & 16 ohm respectively. If you don't know and they aren't marked, find a tech who can tell you how the jacks are wired to the output transformer. Tell them what you are doing and they can show you how, or rewire them to the appropriate output transformer taps. Experimenting with speaker loads on tube amps can get expensive, you probably should try to get it right the first time!

The 8 ohm Marshall cab should work fine with the 1200S, assuming you get it wired to the 8 ohm trans tap.(see above)

Title: Re: 1200S for a bass rig
Post by: rp on September 20, 2006, 08:29:56 pm
I sometimes use a Hartke 410 XL with a 200S or 2000S head and they sound much better than I think they should. Impressively loud with the 60 watter, and plenty of stage volume with the 2000S considering the relatively inefficient Hartke drivers. When I use an active bass however I've got to watch the basses output level or it gets kinda nasty sounding fast. I bet it would sound pretty good with both Hartke cabs at an 4 ohm total load on your old beast.
Thanks, I wish I could find a 2000S for my bass, but no luck as of yet. I'm guessing I should plug the 410xl into the first jack, or does it matter?
I have a gallien kruger 800rb on them now, but it sounds so wimpy and I can hardy get a good overdrive without using
a bass POD rat channel...or Pi -type channel. That's solid state though I guess.

Guitar cabinet wise I was gonna run the 1200S through a 4x12 marshall cab (8 ohms 120RMS)...is this too small a cab?
I have a 120 watt solid state marshall head on it now, and it has hardly any bottom whatsoever. Should I mix any solid state effects
for guitar or bass with it.  thanks



The 2 speaker jacks in the back of a 1200S are either wired for 8 & 4 ohm, or 8 & 16 ohm respectively. If you don't know and they aren't marked, find a tech who can tell you how the jacks are wired to the output transformer. Tell them what you are doing and they can show you how, or rewire them to the appropriate output transformer taps. Experimenting with speaker loads on tube amps can get expensive, you probably should try to get it right the first time!

The 8 ohm Marshall cab should work fine with the 1200S, assuming you get it wired to the 8 ohm trans tap.(see above)


I was told that it was 8 & 16...I really don't understand ohms so I guess I'm at a loss.
Title: Re: 1200S for a bass rig
Post by: Isaac on September 21, 2006, 11:04:25 am
First off, this is the old, tube 1200S, right? If it's the newer, Fender-era 1200S with the solid state output, then none of this is applicable.

The output transformers on the old Sunns have three outputs: 4, 8 and 16 ohms. They had only two output jacks, though. the way they were wired, there was one main output, either 8 or 16 ohms, which was determined by the cabinet the amp was sold with. The other jack was wired to the next lower impedance, either 4 or 8 ohms. It was also wired such that, when a plug is inserted, it switches the other jack to the lower impedance. So, if you have one 16 ohm cabinet, you plug it into the 16 ohm jack. If you have an 8 ohm cabinet, you plug it into the 8 ohm jack. If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 12:50:30 pm
First off, this is the old, tube 1200S, right? If it's the newer, Fender-era 1200S with the solid state output, then none of this is applicable.

The output transformers on the old Sunns have three outputs: 4, 8 and 16 ohms. They had only two output jacks, though. the way they were wired, there was one main output, either 8 or 16 ohms, which was determined by the cabinet the amp was sold with. The other jack was wired to the next lower impedance, either 4 or 8 ohms. It was also wired such that, when a plug is inserted, it switches the other jack to the lower impedance. So, if you have one 16 ohm cabinet, you plug it into the 16 ohm jack. If you have an 8 ohm cabinet, you plug it into the 8 ohm jack. If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
It is indeed the classic tube head from 68-69 with 16/8 ohm jacks. Let me clarify....so if I have two 8 ohm cabs, a harkte 410 and 1x15 in this instance, I can only plug in one cabinet into the second (8ohm) jack....or can I plug both 8ohm cabinets into both jacks at once it will run them both at 8 ohms, and thusly be ok?? Sorry about my ignorance, but I'm pretty new to all this. :-D


thanks
Title: Re: 1200S for a bass rig
Post by: EdBass on September 22, 2006, 04:14:45 pm
First off, this is the old, tube 1200S, right? If it's the newer, Fender-era 1200S with the solid state output, then none of this is applicable.

The output transformers on the old Sunns have three outputs: 4, 8 and 16 ohms. They had only two output jacks, though. the way they were wired, there was one main output, either 8 or 16 ohms, which was determined by the cabinet the amp was sold with. The other jack was wired to the next lower impedance, either 4 or 8 ohms. It was also wired such that, when a plug is inserted, it switches the other jack to the lower impedance. So, if you have one 16 ohm cabinet, you plug it into the 16 ohm jack. If you have an 8 ohm cabinet, you plug it into the 8 ohm jack. If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
It is indeed the classic tube head from 68-69 with 16/8 ohm jacks. Let me clarify....so if I have two 8 ohm cabs, a harkte 410 and 1x15 in this instance, I can only plug in one cabinet into the second (8ohm) jack....or can I plug both 8ohm cabinets into both jacks at once it will run them both at 8 ohms, and thusly be ok?? Sorry about my ignorance, but I'm pretty new to all this. :-D


thanks

If you want to run the pair of 8 ohm Hartkes, ideally you would want to get the outputs connected to the 8 & 4 ohm taps on your output transformer, and plug one cab into each output on the 1200S. Or you could rewire the jacks on your 410 from parallel to series (if you have the "XL" series Hartke 410 there are a pair of jacks on the back wired in parallel, I'm not sure what the "Transporter" series 410 has for jacks) and daisy chain the 115 to the 410 and then into your existing 16 ohm output on your 1200S.
Title: Re: 1200S for a bass rig
Post by: Isaac on September 22, 2006, 05:39:55 pm
It is indeed the classic tube head from 68-69 with 16/8 ohm jacks. Let me clarify....so if I have two 8 ohm cabs, a harkte 410 and 1x15 in this instance, I can only plug in one cabinet into the second (8ohm) jack....or can I plug both 8ohm cabinets into both jacks at once it will run them both at 8 ohms, and thusly be ok?? Sorry about my ignorance, but I'm pretty new to all this. :-D


thanks
You might get away with that. Both cabinets will give you a total 4 ohm load, which is a 100% mismatch with the 8 ohm output. Some say that's not going to hurt the amp. With the price of output transformers, I wouldn't take the chance.

The 4 ohm tap is still there, inside your amp. Why not the output to 8/4? You can do it yourself, if you know what you're doing, or any competent tech can do it in a matter of minutes. Or, have the output jacks wired permanently in parallel, and have an impedance selector switch installed.
Title: Re: 1200S for a bass rig
Post by: ryanowens on September 22, 2006, 05:47:28 pm
If you want to run the pair of 8 ohm Hartkes, ideally you would want to get the outputs connected to the 8 & 4 ohm taps on your output transformer, and plug one cab into each output on the 1200S. Or you could rewire the jacks on your 410 from parallel to series (if you have the "XL" series Hartke 410 there are a pair of jacks on the back wired in parallel, I'm not sure what the "Transporter" series 410 has for jacks) and daisy chain the 115 to the 410 and then into your existing 16 ohm output on your 1200S.

I have the Transporter 410 (also a 115) and they just have an insert on the back, no parallel or anything.

As an aside, I dig the Hartke cabs if I'm shaping the bass to have a nasty sound (usually with a Rat in front of the cab) as I don't personally dig the Hartke sound for a more traditional bass sound.
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 06:02:50 pm
It is indeed the classic tube head from 68-69 with 16/8 ohm jacks. Let me clarify....so if I have two 8 ohm cabs, a harkte 410 and 1x15 in this instance, I can only plug in one cabinet into the second (8ohm) jack....or can I plug both 8ohm cabinets into both jacks at once it will run them both at 8 ohms, and thusly be ok?? Sorry about my ignorance, but I'm pretty new to all this. :-D


thanks
You might get away with that. Both cabinets will give you a total 4 ohm load, which is a 100% mismatch with the 8 ohm output. Some say that's not going to hurt the amp. With the price of output transformers, I wouldn't take the chance.

The 4 ohm tap is still there, inside your amp. Why not the output to 8/4? You can do it yourself, if you know what you're doing, or any competent tech can do it in a matter of minutes. Or, have the output jacks wired permanently in parallel, and have an impedance selector switch installed.
I figured that, yeh I'm not going to chance it. Though, I really have no idea how to rewire the head.....
they do have one guy locally that might be able to rewire it to the 8/4 tap, but I have no idea if he's ever done it before.
I also was looking to buy a 16 ohm guitar cab from avatarspeakers.com for it, so rewiring it would only disservice me in that
department....I guess I should just plug the 4x10 xl into the 8 ohm and leave it be.
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 06:12:06 pm
First off, this is the old, tube 1200S, right? If it's the newer, Fender-era 1200S with the solid state output, then none of this is applicable.

The output transformers on the old Sunns have three outputs: 4, 8 and 16 ohms. They had only two output jacks, though. the way they were wired, there was one main output, either 8 or 16 ohms, which was determined by the cabinet the amp was sold with. The other jack was wired to the next lower impedance, either 4 or 8 ohms. It was also wired such that, when a plug is inserted, it switches the other jack to the lower impedance. So, if you have one 16 ohm cabinet, you plug it into the 16 ohm jack. If you have an 8 ohm cabinet, you plug it into the 8 ohm jack. If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
It is indeed the classic tube head from 68-69 with 16/8 ohm jacks. Let me clarify....so if I have two 8 ohm cabs, a harkte 410 and 1x15 in this instance, I can only plug in one cabinet into the second (8ohm) jack....or can I plug both 8ohm cabinets into both jacks at once it will run them both at 8 ohms, and thusly be ok?? Sorry about my ignorance, but I'm pretty new to all this. :-D


thanks

If you want to run the pair of 8 ohm Hartkes, ideally you would want to get the outputs connected to the 8 & 4 ohm taps on your output transformer, and plug one cab into each output on the 1200S. Or you could rewire the jacks on your 410 from parallel to series (if you have the "XL" series Hartke 410 there are a pair of jacks on the back wired in parallel, I'm not sure what the "Transporter" series 410 has for jacks) and daisy chain the 115 to the 410 and then into your existing 16 ohm output on your 1200S.
I do have the 410xl series and it has two jacks on the back, but I wouldn't even know how to start rewiring it to series.
That idea sounds good to me, but I have heard that daisy chaining on a 1200S might blow all the cabs in series.
I would really rather avoid rewiring...especially for lower ohms. I wanted to avoid mods on it and keep it stock as possible.
 Seems I'm in a pickle. :|
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 06:15:56 pm
If you want to run the pair of 8 ohm Hartkes, ideally you would want to get the outputs connected to the 8 & 4 ohm taps on your output transformer, and plug one cab into each output on the 1200S. Or you could rewire the jacks on your 410 from parallel to series (if you have the "XL" series Hartke 410 there are a pair of jacks on the back wired in parallel, I'm not sure what the "Transporter" series 410 has for jacks) and daisy chain the 115 to the 410 and then into your existing 16 ohm output on your 1200S.

I have the Transporter 410 (also a 115) and they just have an insert on the back, no parallel or anything.

As an aside, I dig the Hartke cabs if I'm shaping the bass to have a nasty sound (usually with a Rat in front of the cab) as I don't personally dig the Hartke sound for a more traditional bass sound.
Nasty is what it's all about. :-D I will also use a POD to shape the final output sound....the orange phase
channel is pretty nice for evening out the sound.
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 10:34:34 pm
How about this for a solution?
I don't want to change my head wiring, but I want to use two nice bass cabs....how about I plug
the hartke 4x10xl into the 8 ohm slot....for the 16 ohm slot get me an empty 2x15 cab
and load it with a couple of heavy magnet 16 ohm eminence speakers??
Wouldn't that make it a 16 ohm cabinet?

Thanks guys   robin
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 22, 2006, 11:11:33 pm
as long as you wired them right, yes, they'd be 16 ohms.  If they're two 8 ohm speakers, then 16 ohms in series; if two 16 ohm speakers in parallel, then you've got 8 ohms.  so maybe a nice pair of heavy magnet 8 ohms (if they exist, i dont know bass speakers)?  or one really big-arse 16 ohm speaker.  Get, say, two 21" woofers from this sub (http://catalogs.infocommiq.com/AVCAT/CTL3120/index.cfm?mlc_id=3120&SID=16904268&pin_id=2128&ProdID=344102&T3=137) and put them in series...that'd give you 16 ohms and more thump than anything on earth!


heehee. the whole concept of a 21" speaker is kinda nuts, isn't it?
Title: Re: 1200S for a bass rig
Post by: rp on September 22, 2006, 11:27:13 pm
The only 16 ohm bass replacements I can find are the eminence delta 15 b's. They look good though...
so uh, every time I replaced a speaker I just plug it into the jacks....what's this series parallel stuff? :?

I look so dumb I'm sure. :-(

How would I wire two of those 16 ohm speakers to give a 16 ohm load?? I don't want to wire parallel if it's going
to make an 8 ohm load, because that defeats the purpose...I already have a 1x15 at 8 ohms.
But if wired series, from what I understand, would double the load to ...32 ohm?? :?
Maybe I should get two 8 ohm 15's and wire them series.. for 16? Is that really safe though??
Is having one 16 ohm speaker the only way to get the 16 ohm load from 16 ohm speakers?
Ow, my head hurts. :-D...also if I do get two 8 ohm speakers to wire series for the 16 ohm load..can anyone tell me how to do it...
it would be my first time.


thanks. :-D

Title: Re: 1200S for a bass rig
Post by: Isaac on September 23, 2006, 12:20:49 pm
Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.
Title: Re: 1200S for a bass rig
Post by: rp on September 23, 2006, 02:06:17 pm
Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.
Ok, so one plugged in the 16 ohm jack can only be a 16 ohm cab, and one plugged into the 8 ohm jack has to be an 8 ohm cab, but if I plug two cabs into it they must be 4 ohm cabs?? So...the way I understand it if the tap was changed to 8/4, it would be a 8ohm cab in the left, or a 4ohm on the right, and if you plug in two they only get 2 ohms between the two cabs??
I don't see how that will help as I don't have a 4ohm cab or 2 ohm cab, and would still only be able to use one 8 ohm cab and lose the ability to ever use a 16 ohm cab.

Also this kinda confuses me...
If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
If you can use two 16 ohm cabs together with an 8 ohm load....why can't two 8 ohm cabs be used safely at a 4 ohm load?
Wouldn't those 16 ohms cabs also be operating at 4 ohms together...isn't that alot different than the two 8 ohm cabs??
totally confused now.. :-(
Title: Re: 1200S for a bass rig
Post by: Isaac on September 23, 2006, 05:17:43 pm
Doesn't matter, Robin. Remember what I wrote about how the jacks are wired? Once you plug into the 8 ohm jack, you no longer have a 16 ohm jack. The internal wiring has put it in parallel with the 8 ohm jack, so you now have two 8 ohm jacks, in parallel. That's two jacks  in parallel, which can accept a total load of 8 ohms, not 8 ohms per jack. Even if you could separate out the jacks, it still wouldn't work, because an 8 ohm load on the 8 ohm tap will take the full output of the amp. Same with a 16 ohm load on the 16 ohm tap. There being no magic in this world, the amp would not be able to supply its full output to two different loads. At best, each would get half. At worst, foul smelling smoke would emanate from the amp.

On the plus side, placing an 8 ohm load in parallel with a 16 ohm load results in a total load of 5.3 ohms, which would probably not destroy the amp.
Ok, so one plugged in the 16 ohm jack can only be a 16 ohm cab, and one plugged into the 8 ohm jack has to be an 8 ohm cab, but if I plug two cabs into it they must be 4 ohm cabs??
No. the total load should equal the transformer tap it is connected to. So, if you're connected to the 8 ohm tap, the total load should be 8 ohms. How you get there doesn't matter. One 8 ohm cabinet, two 16 ohm cabinets, four 32 ohm cabinets, whatever.
Quote
So...the way I understand it if the tap was changed to 8/4, it would be a 8ohm cab in the left, or a 4ohm on the right, and if you plug in two they only get 2 ohms between the two cabs??
I have no idea what you're trying to say here.

If the amp was changed to 8/4, then the main output jack, the one currently labeled 16 ohms, would be an 8 ohm jack. The one labeled 8 ohms would be a 4 ohm jack. If you plug into the 4 ohm jack, the 8 ohm jack also becomes a 4 ohm jack, and the total load - not any individual cabinet - should equal 4 ohms.
Quote
I don't see how that will help as I don't have a 4ohm cab or 2 ohm cab, and would still only be able to use one 8 ohm cab and lose the ability to ever use a 16 ohm cab.
I don't think I said anything about 4 or 2 ohm cabinets. Where did you get this? You don't lose the ability to use a 16 ohm cabinet, you just have to make sure that the total impedance load on the amp is compatible with the transformer tap you're using. If you're using the 8 ohm tap, two 16 ohm cabinets are fine.
Quote
Also this kinda confuses me...
If you have two 16 ohm cabinets (total 8 ohm load, in parallel), no problem. You plug one into the 16 ohm jack, and the other into the 8 ohm jack. The internal wiring puts both cabinets in parallel, connected to the 8 ohm tap on the output transformer, and everything is fine.
If you can use two 16 ohm cabs together with an 8 ohm load....why can't two 8 ohm cabs be used safely at a 4 ohm load?
Wouldn't those 16 ohms cabs also be operating at 4 ohms together...isn't that alot different than the two 8 ohm cabs??
totally confused now.. :-(
Now I'm confused. Of course two 8 ohm cabinets can be safely used as a 4 ohm load. Who said otherwise? But two 16 ohm cabinets make an 8 ohm load not a 4 ohm load, as you seem to be saying.

Two 16 ohm cabinets in parallel=8 ohms.
Two 8 ohm cabinets in parallel=4 ohms.
Two 4 ohm cabinets in parallel-2 ohms, which your amp is not designed for.
Title: Re: 1200S for a bass rig
Post by: EdBass on September 23, 2006, 05:54:14 pm
The only 16 ohm bass replacements I can find are the eminence delta 15 b's. They look good though...
so uh, every time I replaced a speaker I just plug it into the jacks....what's this series parallel stuff? :?

I look so dumb I'm sure. :-(

 

You really need to educate yourself on the difference between series and parallel circuits. Do a little internet research (it's all out there) on basic circuits and this whole thread will become a lot clearer. Reading back through this thread, it doesn't seem to me that you are going to get the answer you are looking for unless you get a handle on the series/parallel issue.

For now, get your amp to somebody who knows and have them switch your output taps to 4 & 8 ohms, plug your 410 into one and your 115 into the other and let her rip! Let us know how it sounds.
The tap switch is completely and easily reversable, it won't hack up your classic amp, the hardest part of the operation is pulling and replacing the chassis in the box. It's a 10 minute job for a rookie tech, and a veteran solder jockey could do the work in a coma!

You don't look dumb, you just look "new". Hang in there, it's as clear as mud now but soon you'll be able to look back and laugh about when you "didn't even understand impedance!"
Title: Re: 1200S for a bass rig
Post by: rp on September 23, 2006, 06:36:55 pm
I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedence is 4ohms for the two.
However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

God I hope I'm right. :-D

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.
I'm guessing though if I make the change to the 8/4 output that I won't be able to use two 16ohm cabs because when
you plug in the second cab the output will switch to 4 ohms rather than 8ohms.

The only problem now is finding a tech around where I live...which is nowhere, louisiana. :-D

thanks guys, robin

Title: Re: 1200S for a bass rig
Post by: EdBass on September 23, 2006, 07:42:15 pm
I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedance is 4ohms for the two.

Two 8 ohm cabs wired in parallel make a total load of 4 ohms, the same two cabs in series would have a 16 ohm load.
Sunn amps like yours connect the two output jacks in parallel when both are used, which in effect connects the two cabinets in a parallel circuit for a total of load of 4 ohms.

However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

If you look at the back of your amp, you will see a huge chunk of iron on the far right side. That's the output transformer. It is actually a huge coil (winding) of copper wire wound around an iron core, and it's primary function is to match speaker impedance with the output stage of the amp. On all of the old Sunn amps, there are three wires referred to as "taps" that "tap" into this winding at different places (one is for 4 ohm loads, one for 8 ohm loads, and one for 16 ohm loads) but only two of the three are used for the two output jacks, the third one is still there, but unused.
The "S" series Sunn tube amplifiers were never sold without a matching speaker cabinet, you couldn't buy just the head you had to buy the package, but they always had the option of an additional, or extention, cabinet. If the matching cabinet for the amp was 16 ohms, they used the transformers 16 and 8 ohm taps (like your 1200S) and if the matching cab was 8 ohms they used the 8 and 4 ohm taps so that if and when you used another matching cabinet, the impedance would be correct. Two 16's would be 8, two 8's would be 4 because of the parallel wired jacks in the amp.
As I said above, the third tap is still there, to make your output jacks 8 and 4 ohms you only switch ONE wire. No major surgery, and just as easy to restore back to original.

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.

Absolutely, but not probably louder(fuller); most definitely louder(fuller)!

The only problem now is finding a tech around where I live...which is nowhere, louisiana. :-D

thanks guys, robin

Can't help you much with that one. You don't really need a guitar amp tech, just about any electrical tech (stereo,TV, radio, etc.) should be able to fix you up.
Title: Re: 1200S for a bass rig
Post by: rp on September 23, 2006, 10:30:04 pm
I think I see now...let me know if I'm wrong. I wasn't splitting the load when I was talking about two cabs.
That's why two 8ohm cabs would be at 4ohms rather than 8ohms even though both plugs were used and the 16ohm was cancelled.
Even though the output was 8ohms, since it was two cabs the impedance is 4ohms for the two.

Two 8 ohm cabs wired in parallel make a total load of 4 ohms, the same two cabs in series would have a 16 ohm load.
Sunn amps like yours connect the two output jacks in parallel when both are used, which in effect connects the two cabinets in a parallel circuit for a total of load of 4 ohms.

However since the output is 16/8 ohm split....the 4ohm output is unnatural and that's why you guys suggested
having the tap altered to 8/4....to match the cabs I want to use. I think I was getting what the cabs do and head do confused.

If you look at the back of your amp, you will see a huge chunk of iron on the far right side. That's the output transformer. It is actually a huge coil (winding) of copper wire wound around an iron core, and it's primary function is to match speaker impedance with the output stage of the amp. On all of the old Sunn amps, there are three wires referred to as "taps" that "tap" into this winding at different places (one is for 4 ohm loads, one for 8 ohm loads, and one for 16 ohm loads) but only two of the three are used for the two output jacks, the third one is still there, but unused.
The "S" series Sunn tube amplifiers were never sold without a matching speaker cabinet, you couldn't buy just the head you had to buy the package, but they always had the option of an additional, or extention, cabinet. If the matching cabinet for the amp was 16 ohms, they used the transformers 16 and 8 ohm taps (like your 1200S) and if the matching cab was 8 ohms they used the 8 and 4 ohm taps so that if and when you used another matching cabinet, the impedance would be correct. Two 16's would be 8, two 8's would be 4 because of the parallel wired jacks in the amp.
As I said above, the third tap is still there, to make your output jacks 8 and 4 ohms you only switch ONE wire. No major surgery, and just as easy to restore back to original.

So really with this head you would want two 16ohm cabs running at 8ohms because of the two cab split. Right?
I mean you could run just one 16ohm cab in the 16 output, but it would probably be louder(fuller) with the two cabs at 8ohms.

Absolutely, but not probably louder(fuller); most definitely louder(fuller)!

The only problem now is finding a tech around where I live...which is nowhere, louisiana. :-D

thanks guys, robin

Can't help you much with that one. You don't really need a guitar amp tech, just about any electrical tech (stereo,TV, radio, etc.) should be able to fix you up.
Thank you so much....I think I've got it now. Hmmm now I just need some more cabs...lol
Title: Re: 1200S for a bass rig
Post by: rp on September 25, 2006, 01:19:41 am
How about this? I can't really rewire the 1x15xl because it's a single 8ohm speaker...you can't wire any other way than parallel..right?
But what about the 4x10xl? It has 4, 8 ohm speakers wired for an 8ohm load and 400watts (series/parallel wiring I think). Is there anyway to wire those 4, 8 ohm speakers to 16 0hms??
Title: Re: 1200S for a bass rig
Post by: Isaac on September 25, 2006, 07:17:22 am
No.

Four 8 ohm drivers can be wired as 2, 8, or 32 ohms, but not 4 or 16.

All in series=32ohms.
Series/parallel=8 ohms.
All in parallel=2 ohms.
Title: Re: 1200S for a bass rig
Post by: rp on September 25, 2006, 09:15:49 am
No.

Four 8 ohm drivers can be wired as 2, 8, or 32 ohms, but not 4 or 16.

All in series=32ohms.
Series/parallel=8 ohms.
All in parallel=2 ohms.
Yeh, no weaseling out of it that way, lol. I had figured that as I found a neat little
wiring chart on the net at a replacement speaker website.
If it's ok I can post the link for others who are new to the whole wiring/ohm process.
Title: Re: 1200S for a bass rig
Post by: Isaac on September 27, 2006, 12:15:03 pm
heehee. the whole concept of a 21" speaker is kinda nuts, isn't it?
Why? I mean, 18" isn't nuts, so why would 21" be? As far as I'm concerned, it's all in the execution.

Oh, and EV used to make a 30" driver!

Electro-Voice 30W (http://www.geocities.com/tadgesualdo/EVpictures.html)
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 27, 2006, 12:40:21 pm
holy mother of my lord and saviour, that is CRAZY.   


I've been coveting a 21" for my dorm room stereo setup for a while...maybe I should look into one of these (I'm currently running a pair of Bose 301s with an Alesis RA-100 on one outlet, and my beta lead on the other).
Title: Re: 1200S for a bass rig
Post by: EdBass on September 27, 2006, 06:40:01 pm
heehee. the whole concept of a 21" speaker is kinda nuts, isn't it?
Why? I mean, 18" isn't nuts, so why would 21" be? As far as I'm concerned, it's all in the execution.

Oh, and EV used to make a 30" driver!

Electro-Voice 30W (http://www.geocities.com/tadgesualdo/EVpictures.html)

Bass response is in direct correlation to cone area and excursion. At the LA NAMM show in '77 or '78 Cerwin Vega had a quad amped system set up with 36" woofers in huge scoop enclosures on the bottom. the centers were fixed and spidered to the magnets so there was no transient highs eminating from the dustcones. I think they were x'ed at 60hz or so. The 1812 overature cannons literally knocked the air from your diaphram. Also at that show, Cetec Gauss had one of their 12" drivers sitting on a table, wired with 14 gauge zip cord and plugged into a 117v wall socket all day. It was meant as an example of their durability. It got the point across!
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 27, 2006, 06:57:59 pm
a wall socket?....wow.  That's pretty hard core.  Heh.  I want one of those setups! (As you can tell, I like plenty of bass in a setup).
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 27, 2006, 07:27:40 pm
Here's something for me...this is when I get the money, the friends to help, and the VERY understanding wife....

http://www.royaldevice.com/custom.htm
Title: Re: 1200S for a bass rig
Post by: rp on September 27, 2006, 07:54:58 pm
Anyone think that 2000S on e-bay is too expensive? It's at 500 right now and I really want it. :-D It's really clean too.
Title: Re: 1200S for a bass rig
Post by: EdBass on September 27, 2006, 08:38:17 pm
Anyone think that 2000S on e-bay is too expensive? It's at 500 right now and I really want it. :-D It's really clean too.

You know, of course, that you have essentially the same amp with your 1200S? That said, I'll bet it goes for closer to $1000 than $500, I'll say $750-$825.
Now that I've shot my mouth off, let's see how close I am!
Anybody else want to take a guess?
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 28, 2006, 06:05:26 am
I'm gonna go crazy and say $1200...
Title: Re: 1200S for a bass rig
Post by: Isaac on September 28, 2006, 12:25:22 pm
a wall socket?....wow.  That's pretty hard core.  Heh.  I want one of those setups! (As you can tell, I like plenty of bass in a setup).
It's not necessarily as impressive as you might think. Consider that the driver might well have been designed for that demonstration. How? Give it a 60Hz resonant frequency.  With a high Q, the impedance at resonance might be over 100, but lets call it 60 ohms. Power being equal to voltage squared divided by impedance, we get 120^2/60=240 watts. Pretty good, but not amazingly so. And, with a 60Hz resonance frequiency, it's not going to make a particularly great bass speaker, either.
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 28, 2006, 01:34:47 pm
no, I was coveting one of the electro voice 30Ws....

but now that you say that, you're right - I guess the common instinct they were playing on (that I had) is that wall current would blow up any speaker no matter how good.
Title: Re: 1200S for a bass rig
Post by: Isaac on September 28, 2006, 04:01:48 pm
Good luck with the 30W. I gather that they're as rare as hen's teeth.
Title: Re: 1200S for a bass rig
Post by: rp on September 28, 2006, 04:56:20 pm
Well, after alot of thinking I'm not going to use it as a bass amp...I think I'm going to use it as a guitar cab for now.
In fact I was thinking of having a custom cab built at 16 ohms....couple of g12h greenbacks and a couple of eminence swamp things.
Question is....do I get it at 16 ohm mono or stereo?

I bet mono.
Title: Re: 1200S for a bass rig
Post by: EdBass on September 28, 2006, 05:07:09 pm
a wall socket?....wow.  That's pretty hard core.  Heh.  I want one of those setups! (As you can tell, I like plenty of bass in a setup).
It's not necessarily as impressive as you might think. Consider that the driver might well have been designed for that demonstration. How? Give it a 60Hz resonant frequency.  With a high Q, the impedance at resonance might be over 100, but lets call it 60 ohms. Power being equal to voltage squared divided by impedance, we get 120^2/60=240 watts. Pretty good, but not amazingly so. And, with a 60Hz resonance frequiency, it's not going to make a particularly great bass speaker, either.

I agree with you Isaac, it was a stock 4282, but technically not as impressive as it would first seem. From a marketing aspect however, I thought the effect was genius. I'll bet you would admit that you would stop and look! It sounded like a distant helicopter, very cool. Of course, not as great a marketing tool as I give it credit for, considering the ultimate fate of Cetec a few years after that show!
Title: Re: 1200S for a bass rig
Post by: rick.heil on September 28, 2006, 05:33:59 pm
Quote
Well, after alot of thinking I'm not going to use it as a bass amp...I think I'm going to use it as a guitar cab for now.
In fact I was thinking of having a custom cab built at 16 ohms....couple of g12h greenbacks and a couple of eminence swamp things.
Question is....do I get it at 16 ohm mono or stereo?

I bet mono.

You're right, mono would probably better.
Title: Re: 1200S for a bass rig
Post by: rp on September 28, 2006, 05:39:45 pm
Quote
Well, after alot of thinking I'm not going to use it as a bass amp...I think I'm going to use it as a guitar cab for now.
In fact I was thinking of having a custom cab built at 16 ohms....couple of g12h greenbacks and a couple of eminence swamp things.
Question is....do I get it at 16 ohm mono or stereo?

I bet mono.

You're right, mono would probably better.
I guessed that.... being in 68 I think everything was mono. I should still rock hard as hell...
those heavy magnet greenbacks for that sabbathy creamy tone...and the swamp things for high wattage handling
and rumbling low-end....maybe some celestion neodymium centuries would be better than
greenbacks for de-tune, but everyone raves over those g12h's.
Title: Re: 1200S for a bass rig
Post by: Isaac on September 30, 2006, 08:52:10 pm
Well, after alot of thinking I'm not going to use it as a bass amp...I think I'm going to use it as a guitar cab for now.
In fact I was thinking of having a custom cab built at 16 ohms....couple of g12h greenbacks and a couple of eminence swamp things.
Question is....do I get it at 16 ohm mono or stereo?

I bet mono.
Stereo? What are you talking about now?
Title: Re: 1200S for a bass rig
Post by: rp on September 30, 2006, 09:56:02 pm
I was offered a 4,8 or 16 ohm cabinet in either mono or stereo.

I was thinking that should match up with the head.
Title: Re: 1200S for a bass rig
Post by: EdBass on October 01, 2006, 09:17:40 am
I was offered a 4,8 or 16 ohm cabinet in either mono or stereo.

I was thinking that should match up with the head.

How would you use a stereo cabinet using your 1200S amp?
Title: Re: 1200S for a bass rig
Post by: rp on October 01, 2006, 09:54:01 am
I was offered a 4,8 or 16 ohm cabinet in either mono or stereo.

I was thinking that should match up with the head.

How would you use a stereo cabinet using your 1200S amp?
Well that's just it...I guess I'm not since the head was made in the mono generation.
I'll just get a 16 ohm mono cab...whatever that is. :-D
Title: Re: 1200S for a bass rig
Post by: rp on October 11, 2006, 04:53:03 pm
Well I got my 1200S in today... and it looks good, however, when I plugged it in
it kind of hummed at me and then blew a fuse.

 :cry:


Title: Re: 1200S for a bass rig
Post by: EdBass on October 12, 2006, 06:58:27 pm
Well I got my 1200S in today... and it looks good, however, when I plugged it in
it kind of hummed at me and then blew a fuse.

 :cry:




That's a shame! Oh well, box it up and send it to me and I'll dispose of it for you.
Title: Re: 1200S for a bass rig
Post by: rp on October 13, 2006, 02:16:43 am
Well I got my 1200S in today... and it looks good, however, when I plugged it in
it kind of hummed at me and then blew a fuse.

 :cry:




That's a shame! Oh well, box it up and send it to me and I'll dispose of it for you.

Maybe I should just fix it. :-D
Title: Re: 1200S for a bass rig
Post by: rp on October 14, 2006, 02:29:57 am
Can I run the head with just the 6550 tubes? I think my rect tubes are bad....I pulled them and checked the
rest but am getting no sound through the speakers.
Title: Re: 1200S for a bass rig
Post by: EdBass on October 14, 2006, 08:30:20 am
Can I run the head with just the 6550 tubes? I think my rect tubes are bad....I pulled them and checked the
rest but am getting no sound through the speakers.

No you can't. It would also probably be a good idea to quit trying to make it work as it sits. You really need to find a tech in your area who specializes in, or at least is familiar with tube amps. Don't try to fix it yourself; based on your posts I don't think anything good would come from that. Also, be very careful poking around in that amp, there are potentially LETHAL voltages stored in the capacitors. EVEN WHEN THE AMP IF TURNED OFF AND UNPLUGGED!
One false move could end up being your last.
Conversely, your old Sunn would be child’s play for a good tech; they are pretty basic and straight forward.

Or...Just donate it my personal collection, where it will be refurbished and well treated, and have a great home with a whole bunch of its Sunn siblings.
Title: Re: 1200S for a bass rig
Post by: rick.heil on October 14, 2006, 09:16:54 am
Heehee....you wish it would get donated, Ed.
Title: Re: 1200S for a bass rig
Post by: EdBass on October 14, 2006, 09:59:41 am
I'm not a cheapskate - I'd pay for shipping!
The "buy low, sell high" theory has served me very well, and I have yet to find "lower" than "free"!*

Seriously, if rp wants to get rid of the 1200S, I'd wait for an eBay Sunn upswing and list it. Somebody will pay too much for it, and that's the best way to find them.
 

*DISCLAIMER - This is in jest, I am NOT attempting to coerce rp or anyone else to send me their tube amps free of charge.
Mind you, I will accept them; it's just not coercion!
Title: Re: 1200S for a bass rig
Post by: rp on October 14, 2006, 10:05:17 am
Can I run the head with just the 6550 tubes? I think my rect tubes are bad....I pulled them and checked the
rest but am getting no sound through the speakers.

No you can't. It would also probably be a good idea to quit trying to make it work as it sits. You really need to find a tech in your area who specializes in, or at least is familiar with tube amps. Don't try to fix it yourself; based on your posts I don't think anything good would come from that. Also, be very careful poking around in that amp, there are potentially LETHAL voltages stored in the capacitors. EVEN WHEN THE AMP IF TURNED OFF AND UNPLUGGED!
One false move could end up being your last.
Conversely, your old Sunn would be child’s play for a good tech; they are pretty basic and straight forward.

Or...Just donate it my personal collection, where it will be refurbished and well treated, and have a great home with a whole bunch of its Sunn siblings.


Well a buddy of mine who has a bit of a guitarist, circuitry background said he might take a look at it...though
he admits he knows more about solid state than tube amps...I think he just got one in fact.
I checked ebay for tubes and found some sovteks(?) 3 for thirty dollars so I might next try putting
fresh rect tubes in w/a spare.

No, you can't have my 1200S.

 :-D
Title: Re: 1200S for a bass rig
Post by: rp on October 14, 2006, 10:10:53 am
I'm guessing the capacitors are the silver fixed tubes behind the 6550's??

He asked me for a schematic, but have had no luck in locating one. I wouldn't feel safe messing around in there...
though I have to admit I didn't know it could shock you unplugged.
Title: Re: 1200S for a bass rig
Post by: EdBass on October 14, 2006, 10:34:58 am
I wouldn't mess with rectifier tubes, particularly using the amp for bass. I would go this way;
http://www.webervst.com/ccap.html
Cheaper and less voltage drop - more potential for your power tubes, and they drop right in.
I'm guessing the capacitors are the silver fixed tubes behind the 6550's??
Those are likely the original can caps, maybe replaced, maybe bypassed, who knows? If they are original, they are almost definitely bad (have I mentioned to get a qualified tech?) and need to be replaced - actually they should also be upgraded from the spec on the schematic. (have I mentioned to get a qualified tech?) There are capacitors throughout the chassis, but those big filter caps have the most potential to ruin your day.
He asked me for a schematic, but have had no luck in locating one. I wouldn't feel safe messing around in there...
I have a factory schematic, I can PDF it to you.
I have to admit I didn't know it could shock you unplugged.
Not just shock you, it can freekin' KILL you!
Title: Re: 1200S for a bass rig
Post by: rick.heil on October 14, 2006, 10:40:41 am
Robin - the whole point of capacitors is that they store charge. Filter caps store HUGE amounts of electricity.  Getting shocked by one of those would be the equivalent of licking a live plug that runs to the wall outlet in your house.  It could (and probably would) kill you most quickly. 

BE CAREFUL!  I wouldn't want to see you on the news, in the hospital, or having your fingers shocked off and having to give your amp to Ed   :roll:
Title: Re: 1200S for a bass rig
Post by: rp on October 14, 2006, 12:12:48 pm
I wouldn't mess with rectifier tubes, particularly using the amp for bass. I would go this way;
http://www.webervst.com/ccap.html
Cheaper and less voltage drop - more potential for your power tubes, and they drop right in.
I'm guessing the capacitors are the silver fixed tubes behind the 6550's??
Those are likely the original can caps, maybe replaced, maybe bypassed, who knows? If they are original, they are almost definitely bad (have I mentioned to get a qualified tech?) and need to be replaced - actually they should also be upgraded from the spec on the schematic. (have I mentioned to get a qualified tech?) There are capacitors throughout the chassis, but those big filter caps have the most potential to ruin your day.
He asked me for a schematic, but have had no luck in locating one. I wouldn't feel safe messing around in there...
I have a factory schematic, I can PDF it to you.
I have to admit I didn't know it could shock you unplugged.
Not just shock you, it can freekin' KILL you!
Those are awesome...and not that expensive. Maybe I'll just pick those up, and if they solve the problem
that's that. If not I'll just make the drive to a tech. I never really intended to dig in it too much...just check the tubes
and see kinda what was making the fuse blow out. I was worried it might be a transformer.

Thanks, more than likely whoever I take it to will need that schematic. :-D

The tubes read 6550A RCA that are good....should I swap these out also...or at least get a spare?

Title: Re: 1200S for a bass rig
Post by: EdBass on October 14, 2006, 07:25:55 pm
Robin - the whole point of capacitors is that they store charge. Filter caps store HUGE amounts of electricity.  Getting shocked by one of those would be the equivalent of licking a live plug that runs to the wall outlet in your house.  It could (and probably would) kill you most quickly.
Well, let's not get crazy here. The potential exists, but to actually get offed by a filter cap would take a "perfect storm" kind of scenario that would likely involve using both of your hands to complete a circuit with your heart in the middle. My high school electronics teacher made us put one hand in your pocket while you poke around the guts of a chassis, I mostly still do that to this day.
They will knock you on your ass pretty quick though.
Those are awesome...and not that expensive. Maybe I'll just pick those up, and if they solve the problem that's that.
Maybe that will work, but it could be a number of things. My money's on the filter caps. Regardless, IMO those Copper Caps are superior to tubes in respect to a clean, strong bass application. For guitar some like a little more sag, it's pretty much personal preference.
If not I'll just make the drive to a tech. I never really intended to dig in it too much...just check the tubes and see kinda what was making the fuse blow out.
Good thinking.
I was worried it might be a transformer.
You have just hit on the worst case scenario. If you need a tranny it's gonna cost you some money, maybe half of what the amp is worth in excellent condition.
The tubes read 6550A RCA that are good....should I swap these out also...or at least get a spare?
Have you tested them on a tube tester? If they are matched and test strong, that set of USA RCA 6550's are gold. You don't need a spare, if you blow one or more you should get another matched set of 6550's or KT88's.
I won't even speculate on what brand of new tubes, it's a personal preference. I think that's like telling a player what string gauge that you think they should be using.
Title: Re: 1200S for a bass rig
Post by: rp on October 15, 2006, 10:39:18 am
Should I try a pair of those WZ68's? Or stick with the WZ34? As far as I can tell by using fuses the 6550's are ok.
Is there anything I can do to test if the transformer is bad without going inside? Caps?

Title: Re: 1200S for a bass rig
Post by: EdBass on October 15, 2006, 04:13:36 pm
Should I try a pair of those WZ68's? Or stick with the WZ34?
You got me on that one! I got a bunch of the WZ34's and use them instead of GZ34's wherever I need them in my tube rectified Sunns. You probably only need one of those WZ68's to replace both of your rectifier tubes. You can actually run your amp on just one GZ34, but it will starve for current and break up quickly. You should email Ted and ask him;
ted@webervst.com
he will be glad to help you out.
As far as I can tell by using fuses the 6550's are ok.
I have no idea what that means.
Is there anything I can do to test if the transformer is bad without going inside? Caps?
No you can't. Again, find a tech. Or learn about electrical engineering. A tech will probably be quicker and cheaper than a few years of school or home study.
Title: Re: 1200S for a bass rig
Post by: rp on October 15, 2006, 06:04:41 pm
I e-mailed him, as soon as I get an answer I'll order a couple of whatever he recommends...and
then go from there.
Title: Re: 1200S for a bass rig
Post by: rp on October 16, 2006, 02:16:45 am
Thanks for the pdf file, Ed!  :-D

When I get her going I'll post some pics. This head is way bigger
than the marshall cab it sits on...looks huge. :evil:
Title: Re: 1200S for a bass rig
Post by: rp on October 24, 2006, 05:00:42 pm
Well I'm going to see a tech tommorrow...I e-mailed him the schematic and
told him kinda what I'd like to do. However he did ask me what kind of caps/cans
he would need to order to replace the old ones? Anyone know?
Title: Re: 1200S for a bass rig
Post by: EdBass on October 24, 2006, 07:53:40 pm
Well I'm going to see a tech tommorrow...I e-mailed him the schematic and
told him kinda what I'd like to do. However he did ask me what kind of caps/cans
he would need to order to replace the old ones? Anyone know?

I sent you an email with some ideas. If you or your tech has any questions about it, let me know!
Good luck, and keep us posted!
Title: Re: 1200S for a bass rig
Post by: rp on October 25, 2006, 04:09:30 pm
Well I'm going to see a tech tommorrow...I e-mailed him the schematic and
told him kinda what I'd like to do. However he did ask me what kind of caps/cans
he would need to order to replace the old ones? Anyone know?

I sent you an email with some ideas. If you or your tech has any questions about it, let me know!
Good luck, and keep us posted!

Well we chatted today about it and I think it went pretty well. I had a couple of burnt small tubes....
The rect tubes were actually not burnt, but by the time I left he hadn't checked the 6550's.
The rect tubes were mullards from great britain btw. He reversed himself on the copper caps though but
only because I was considering putting in kt90 tubes with them. He's also going to do the can cap mod
to handle that extra power....by running them together he said their handling can be increased to 800 (watts,volts I forget)
instead of the five something they were before. He thinks it should increase watts up to about 160-180.
A few components had gone bad also, but he said they would be a dollar or two to replace.

 :-D
Title: Re: 1200S for a bass rig
Post by: EdBass on October 25, 2006, 06:04:29 pm
Should be a rockin' rig. Get your tech to switch your output tranny to the 8 & 4 ohm taps while they are in there, it ought to sound great through your Hartke cabs.
Title: Re: 1200S for a bass rig
Post by: rp on October 25, 2006, 06:13:45 pm
Should be a rockin' rig. Get your tech to switch your output tranny to the 8 & 4 ohm taps while they are in there, it ought to sound great through your Hartke cabs.

I can post pics when he's done if guys like. He also builds custom cabs with weber speakers, as well as custom tube heads.
I may try having him build me a 6x12 cab with some high end weber speakers. I need to look around for some specs of the original cab
for ideas. Those 6550's were all good but one, so I'm going to sell them back at him for hi-fi applications towards
a quad of kt-90's. :-D