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Hi all. I've been out of the loop a lot lately - life's just been busy. But, I've finally solved my one issue with my sIII...and I didn't have to re-wire or re-solder anything to fix it.

As some of you know, I've been wrestling with a strange artifact in my sIII since I first built it, a strange twangy buzz in the top end when overdriving the back end of the amp. I've tried some strange things (on top of all the normal things) to fix it. At one point I had one of the output tube plates grounded (to rave reviews ), and it actually fixed it - but there was no doubt it wasn't a good solution (and I've removed that mod).

I recently bought a new Traynor Custom Special 100, and the first thing I did with that thing was start swapping pre-amp tubes. The stock Sovtek 12AX7-WA's were really sterile in that amp. I scavenged a couple of Tung-Sols from my sIII and they warmed the Traynor up nicely.

For the time being I had to fill the empty V1 & V2 in the sIII, so I dropped the Sovteks in there. Much to my surprise (well, shock really), the amp actually sounds great with these tubes. Not only that, but my old problem is gone. What the hell?

But, I think I know what the answer is now (finally). Most of the tubes I've tried in V1 are higher gain tubes (GT 12AX7-C, Ruby Select ECC83, new stock Tung-Sol 12AX7, some Mesa branded thing, and a few others). I've tried all those tubes in every position with no noticable differece. The 12AX7-WA is a bit lower gain than the others though (which is why Fender likes them I guess). My thought is that the issue wasn't in the PI/mixer or output stage at all, but at the very beginning of the signal chain with the input buffer. There was too much signal from the front end causing something to overload in the back end as a result.

Anyway, the amp now has Sovtek 12AX7-WAs in the input buffer & PI, and a Ruby Select ECC83 for the sIII channel gain stages. The end result is a lot less gain, but the amp sounds fantastic with no strange artifacts. There's a little more clean headroom on both channels, and the normal channel is nice & jangly - even with my SG. The nasty bright/shrill edge is also gone (I had thought from the beginning this was a side-effect of the other issue). The TMB channel sounds much more vintage Marshall-ish than before (that vowelly/boxey overdrive).

So finally the amp is all buttoned up in the shell, hopefully not to be yanked apart again in the forseeable future! Now it's just plug in & enjoy some sonic bliss...

Kirb

emo - great to hear. We have used some higher gain tubes in V1 and always backed off a bit. You tried so many tubes it seemed that that wasnt the problem. Well, all's well that ends well.

What's next?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Yeah - I know what you mean. I never would have thought it was tubes with the variety I tried. At the very least I learned a LOT from doing it, and I certainly had plenty of opportunity to hone my soldering skills!

What's next? Good question. Since I just bought ANOTHER amp (I need a 12-stepper for the GAS...), upgraded the P-U's in my Ibanez, and bought a motorcycle things are tight at the moment. I'd like to do another one over the summer though - maybe a V6 or a Deluxe. I'm sure you'll be hearing from me!

I got this tread from Coco on 18 watt.

Very interesting about higher gain 12ax's in Slll. For some reason my Slll is very biting and kind of ice picking bright. Not real bad but all I did was try a bunch of USA used 12AX's in first and second tubes. I mixed up the ones that were in there before I started experimenting, so I can't go back. I have a bag of about 50 all mixed up....

I was wondering about a 5751 in V1. How are these? I use to use these tubes to tame gain problems before changing caps and resistors. I also have some Sovtek WA's but those had been bright to my ears in Fenders so I never tried them in the Slll...? Interesting how they worked in above post.