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Variable Voltage Reduction - a Variable B+ control. Who's tried it & what do you think of it;s tone?

Who's interested in getting one going on a Trinity Amp?

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

first post so...Hello!

I ordered your v6 last week and have considered adding VVR to the build. There seem to be some space in the corner behind the transformer for it.

So I'll be interested in a add on kit. The pcb and components included.

Can't wait to get started on this build

We're working on getting something together. Just need to see how well these sort of circuits perform.

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

Stephen, I'll give it a shot if you'd like. My SIIIv6 has been running for a while so I have a baseline.

Let me know.

We're getting close to a decison. Finally got one going. Now, the taste testing begins!

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

Coco,
Check your email. I sent a pic of my V6. I used the tagboard layout from the previous email. I can't remember who drew it up.

LeeMo

So we have two on the go. A third one is going to be installed in lbets amp for field testing but so far - looking good.
Add-On board is only 1-1/4" square!

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

Where di you hook it in. Afer rectifier? after 1st filter cap? did you add any caps/ did you have any problems? especially with noises?

Done two, on to the third now. All have had some issues that needed to be sorted out - mostly noise.

So, what MOSFET did you use as well? Maybe that's the problem.

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

Coco,
I disconnected the standby switch and put it in there. Standby> vvr > cap.
Yes , I did (and still do) have noise. Not so much on the normal channel. Mainly the TMB channel. The noise is D.C. on the input. It seems to vary from day to day. I haven't figured it out as yet. Dana has a fix for it in the SEWatt / building amps thread.
http://www.sewatt.com/node/16172?page=4
"Here is something to try as a fix for the scratchy pot problem. I installed a .1 cap on the input and another .1 cap between the wiper of VR1 (Vol Control) and the grid of the 12ax7 (pin7) for the VJ. This will isolate any dc voltage on the grid from getting back on the Vol control. If someone wants to try it, let me know how it worked for you.

I still don't know WHY it is happening on some amps and not others. I tried 3 different circuits (including KOCs) and was able to reproduce the problem on all of them if you regulate the whole amp. It seems that once the grids of the 12AX7 get down to .6 - .7 volts the scratchyness starts."

I guess the quote worked. It was from UR12 (Dana) on SEwatt.
It,s a great read , even tho it's nine pages long now.
I've been really busy the last few Saturdays, so I haven't had a chance to play with it. I'll try tomorrow and report my findings.

LeeMo

The VVR is very good. We out another one in last night. Still refiing it but lbet said still has amazing chunk even at low volumes and still amazing sustain even at lower volumes. Here's a picture of the implementation.

It does have noise as well and we're looking into how to sort that out most easily. When controlling the voltage of the whole amp, as we did, and not just the power tubes, the reason for the noise is because at low voltages the signal on the grids of the two preamp tubes leaks a little DC voltage onto the guitar pot and volume control when the signal hitting these grids drive them more positive than the bias voltage applied. Extra coupling caps in the signal path will solve the problem.



We hope the next iteration will be extremely compact and available as an add-on module. It should fit just about anywhere in an amp and be about 1.5" square. That's about the same size of the board in the picture. That's the plan. Should know soon.

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

I've always been interested in this technology. Been looking at the London Power Power Scaling and Bias mod kits. This sounds quite similar. Even though I built the Trinity Deluxe kit is this technology still relevant?

Absolutely. This is much simpler, very effective and less cost than KOC for sure. The ones we built so far were based on the basic VVR design but we will probably package it up with additional parts & build it as a much smaller overall module.

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

Ours is working great. Just looking for the best solution for the noise. Any update?

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

I'm excited to hear about this! I've been reading up on several methods of varying B+, and heard some clips of amps using it. This would be a very cool addition to the Trinity amp circuits!

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Monte

Yeah, I was jammin' with lbet and heard the prototype in his rig. Sounded pretty good to me. It's nice to live in T.O.

JP

update:
I played Saturday and yesterday fairly extensively. It also has the DC scratch on the normal channel. There is a bad hum when jumping channels. (may not be related) It seems to lessen after it warms up for 30 minutes or so. I'm really lovin' it.

LeeMo

Well, I broke the module yesterday so it's on the back burner until an order of MOSFETs arrives. At that time, we'll try to go through all the paces.

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

UR12/Dana suggested looking in old computer power supplies for free mosfets. You asked me earlier which one that I used. It's a NTE 2377 like in the schemo. I'm not one to experiment on new ground.

LeeMo

Hmmm, curious to understand why we would be discussing MOSFET'S.
Hey Leemo!
And what switching device are we trying to build.
God, trying to come up with a thought.
Later

They take virtually no space, are easily voltage controlled and can handle the hi voltage/current. They make a great and simple add-on module too.

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