Author Topic: The tamming of the Solarus  (Read 64 times)

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Offline CBS

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The tamming of the Solarus
« on: August 16, 2017, 07:44:39 am »
                                     Hello everyone! New member here with my first posting.
     First, let me tell you that I have been playing guitar for...well, all my life and have been making a living at it for 38 years. With that said, let it be known that I AM NOT A TECH!!!
     Yesterday, I found and purchased what was said to be an early 70s Sunn Solarus head for a very good price. I tried it out for a short time at the kid's house (I say "kid", he was probably in his early 30s) and brought it home where I immediately removed the chassis for inspection and clean-up. There I found that the power transformer on the right side (by the power cord & fuse) had been replaced and looked new (Fine). Someone had also replaced the A/C cord with a very long, three pronged one (also fine) but the rest of it looked original. I also found on the chassis, a date marked with a red marker and a small round sticker also with a date, both reading 9/8/69. I was very pleased to say the least! It had new looking EL34s (Groove Tubes) and the other tubes had no brand name that I could see.
     Once back together, I tried it with three different cabinets ( A Jet City1x12 w/a V30 16ohm, A Marshall 8ohm 2x12 w/ V30s and a Mesa 2x12 8ohm w/ with Black Shadows )    Everything works! Reverb, Tremolo, mid boost sw, all of the controls work and are quiet! Wonderful!
    I reminds me of my Custom Hiwatt 50 that I purchased new @ 1982 in that it is clean, clean, clean and it doesn't break up until you turn it up to about 8 but, that's when she really starts to sing. Then she'll rip your face off! (Reminds me of an ex girlfriend) That my friends is why I haven't used my cherished Hiwatt in years.   
     I'm thinking about just flipping this amp but I would like to start using it out because it's just so damn cool! I'm playing smaller clubs these days and need to "tone it down a bit" (so I've been told from time to time).
So, with that in mind, here's my question...Is there a lower gain pre-amp tube that I can install to lower the output and make it break up sooner? Something (without using a power soak) to make her sing without turning up to 8? Yes, I use peddles but, the clean is also kind of brittle sounding and could use some softening up. Any suggestions? Thanks!
     
« Last Edit: August 16, 2017, 08:08:06 am by CBS »

Offline Soundmasterg

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Re: The tamming of the Solarus
« Reply #1 on: August 16, 2017, 03:57:13 pm »
So, with that in mind, here's my question...Is there a lower gain pre-amp tube that I can install to lower the output and make it break up sooner? Something (without using a power soak) to make her sing without turning up to 8? Yes, I use peddles but, the clean is also kind of brittle sounding and could use some softening up. Any suggestions? Thanks!
   

Sunn amps are ultralinear (UL) amps, and they also have a lot of negative feedback. That results in an amp that is very clean and detailed, until it breaks up. Once it breaks up, then the character of the overdrive/distortion is somewhat harsh. If you disconnect the negative feedback loop, then the gain of the amp will go up and it will distort at a lower volume, but the noise and hum go up also. It is usable this way however, but it will still be bloody loud and have a harsh character to the distortion.

The output power is determined by the power tubes used, the size and capabilities of the output transformer, and the B+ voltage that the tubes are seeing. The output transformer on a Sunn is large with a wide frequency response; the B+ voltage is on the high side; and the power tubes usually used in a Sunn (6550) are not a great tube for guitar. Your amp is using EL34's, which some of the Sunn's used, but I suspect that your Sunn might be meant for the 6550's given it's vintage. Could tell more from a pic, or identifying the numbers stamped on the end bells of the transformers, and also the B+ voltages, but it will function with those tubes without issue.  The high voltages and the circuit design are what result in the brittleness and harshness of the amp. That is one reason why I personally don't like any Sunn I've ever heard/played for guitar. I love them for bass however. Anyway, the point is that trying to sub in a preamp tube wont get you where you want to go. Adjusting the circuit might get you in the direction you want to go, but it might not also, and since you aren't a tech, you would spend a lot of money to find out. It is possible to add power scaling and a master volume to it and it might become more usable to you. Power scaling allows you to turn the output power down, and you adjust the volume and the master volume to get the same (mostly) loud tone at lower volumes. It works pretty well but it does require a master volume, and it does require some tweaking to get it to work the way you want it to, which again would cost you a fair amount of money to achieve. I would advise you to sell it and get an amp that is more suited to the sounds you want to achieve at the volumes you want to achieve them.

On another note, are you interested in selling your HiWatt?

Greg