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Notice: Some layouts had 1M Grid Stopper (R1) resistor connected to the DC Blocking cap, C1, on the control side. It should be connected to C1 on the Tubes side. The layout and schematics have been updated and posted.

Symptoms:
Some owners have had behavior being described as an intermittent lack of performance. This is [probably] due to this mis-arrangement.
If you turned off the amp when it wasn't behaving, and it worked a day or so later, this could also be a symptom.
In some cases, the amp may not work on start-up even though all else is fine.

Solution:
The easy solution if you built your amp this way, is to clip the 1M off at C1, run a wire from the other side of C1 to the 1M. Or just replace the 1M (email for new part a 1M, 1/2W carbon film/metal film will work fine.).



Explanation:
One purpose of the 1M Grid Stopper is to prevent the grid from 'floating' electrically as it will be referenced to ground. With the capacitor ahead of it, this grounding not as effective and can cause the grid to float causing the issue.

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

Just a tiny point Stephen.....in the resource/tramp section on the schematic where you have revision dates for this change above you have 2010.
Stew

thanks. fixed

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

Stephen and I have reviewed previous revisions of the schematics and layouts and it's something of a mystery how that 1M resistor got moved from the correct position where it used to be, to the wrong position shown on the recent revision of the layout. The correction shown here simply puts the resistor where it was before.

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Great tones come in small glass jars!

Hi Stephen,

This little change has made a significant improvement for the better with how the VRM operates. Before, it was fine at full tilt, however when backed off the volume dropped considerably and the tone was unpleasantly fuzzy.
Now it's superb and works the way it should. Thanks again.

Checked tonight & I had to move this as well. I hadn't really noticed a big problem (I also hadn't played it much, only a little testing) but it does seem better now.

I did a jumper wire - too close to clip it, but I de-soldered it from the board & had just enough to make a nice loop on the end of it.

Good to hear. In what way(s) did it seem better?

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

Well, I didn't have any sputtering but it seemed to get a bit louder after the fix. (In my wholly unscientific opinion! ) The VRM was behaving a little better as well - to be honest I hadn't done a lot of subjective testing, only basic functionality, and the amp was working pretty good to begin with.

I had not been having any issues with the amp but I decided to change the resistor location as rcommended. If I noticed any differences they were fairly subtle. When the volume was in "tude" and around 10 (where I like it) the sound was less "pinched" if that makes sense. Perhaps it had a little less grind and sounded more open. With respect to the VRM it seemed to work fine before although I have to admit I was only using it in the 9-11 range. I find that backing it off just slightly puts a nice little "brown" edge to the overdrive. I also dimed it for the first time. With the combination of tubes and speaker that I have chosen it flat out roars. I can easily gig with it.
Next task is to attach my 1X12 extension cab, when I finally get a 90 degree plug for the speaker cable.

Thanks for the feedback.

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

You're welcome for the feedback. I feel like I should write a full review of this amp.
The combination of the VRM contol with the two push/pull controls is sheer genius. Obviously the circuitry is still the key. I've played every amp I could get my hands on for 30+ years and I've never seen such a simple concept that produces so much variety of good tone. Now it probably doesn't hurt that I'm using an amazing speaker and good tubes as well. Makes me wish that I was a session player. If Fender ever got their hands on a design like this with their marketing and distribution they would sell a ton. The problem is that they would cheap it down and it wouldn't sound as good.

If I can ever figure out how, I'll try to upload some soundclips.

Did you get that bias switch figured out?

Yes I got the bias switch figured out. There was no problem at all, just me being stupid. I tried the 6V6 tube and it sounded fine, but not as fine as the KT66. I have however found significant tonal differences with the choice of 12AX7's.

Mine also got a bit louder after the change. VRM functionality was also improved at lower settings. I would say the VRM almost became more consistent/repeatable.

Thanks for the feedback. Keep us posted. It makes sense.

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