Sonic II Information please !!!

[EdBass]

Of course, he later played through multiple coliseum amps with multiple 18"s and 4x12"s!

Let me fix that;

Besides; the "little" amps were good enough for Entwistle for a while! 

[eclectiq]

I've read on an old thread that KT90s work well in this amp for guitar applications. Can anyone confirm or dismiss that? Currently it has RCA 6550s.

Thanks !!!

[eclectiq]

Hello again all. I've been enjoying my recently "freshened up" Sonic II. Restored back from SSR to TR and sounds great with my LP or Strat.

Something has been troubling me though. I got it back from the tech and the invoice reads (have patience with me please):

"Removed SS rectifiers and reinstalled 5AR4 tube, replaced a weak phase inverter tube, traced and repaired a defective ground connection which was causing the majority of the hum problem. Installed an additional filter cap on the preamp voltage tap to further reduce residual hum, cleaned and tightened all, thoroughly tested all functions"....

(this is where I get concerned)

..."FYI replacing the main filter caps on this unit will be arduous, mainly because the voltage of the existing caps is higher than most standard values. This means a redesign of the circuit to accommodate modern cap values will be needed. This, coupled with the original cap being a multi-section cap. All of this adds up to headache and expense. Luckily, your caps look good and will probably hold up for many years."
 

My question: Is this accurate , having to redesign the circuit and will that change the personality of this amp should it ever be needed? Or is that BS?

Thanks for taking the time to read and respond !!!

[mckinnon audio]

   Hi there,you don't have to "re design" the power supply,just replace the caps and add some power sharing resistors on them,worst case scenario.Just my opinion,that's all,Mel.

[Soundmasterg]

The guy has probably been reading my posts here about the subject, but doesn't have an understanding of whats involved. It isn't that hard to go with discrete caps arranged in series instead of the can cap. I just did it last week on a 200S for a guy. To overhaul the whole amp, clean sockets and pots, test all tubes, replace what needed to be replaced, and add the series-connected caps took all of 6 hours, and would have taken less if I didn't have to troubleshoot why a cap exploded. (It happened due to a bad parallel 220k resistor for the series connected caps) If you wanted to do it in a simpler way, you could always go with one of the SDS boards which replace the can cap with a board already wired up with the caps. For guitar, you probably wouldn't want to go with much larger filter cap values than what is stock, but to go with a higher voltage rating is certainly a good idea.

Greg

[HRobert]

Was (is) the Sonic 2 a guitar or bass amp? Or both? I use mine for guitar but was wondering how it was marketed. Late 60's, right?

Joe

Joe,

I have a photocopy of the 67 Sunn brocheur, and from what I can see the Sonic II was the same as a 200S - with the exception of the speakers.  The Sonic II appears to have the same cab as the 200S, but it lists 2 JBL D-130 speakers where as the 200S had 2 D-140's.  It was marketed for keyboards and guitar.  I'll try to scan the picture and post it. But since it'll be a scan of a copy, I'm not sure how it will come out.

[pickinatit]

I have played the same size rooms that you mention.  A friend of mine had the exact same Sonic II so I had both cabs laid over and both heads stacked on top with a Y cord to a Fender Precision.  It rocked hard but my 2000S just blows that away with the one cab with D140's.  EdBass is right that it is double the power but the richness of the sound is what I was looking for and found with the 2000S.  I may have had it up to 4-5  and the whole house feels like it's coming down.....so I am happy now!

For bass I agree whole-heartedly (actually for guitar too although I would miss the reverb and vibrato that my Solarus brings to the table, but then there's the 1200S for that).  My point was just that for guitar,  the 40 watt Sunn tube amps are MORE then adequate for getting the job done.  Can you come up with a "better" rig for guitar?   Of course.  There will always be something better,  especially when you start piggy-backing / mixing-matching/stereo-ing/etc. heads and speaker cabs.  All I'm saying is that the 40 watt Solarus was perfectly capable of getting the job done in even the larger of the venues I mentioned.

[eclectiq]

On side note: I was happy to discover that although the original KT88s were swapped out some time ago what I have instead are two RCA-branded gray panel Tung Sol 6550s from 1971...and they still test strong