A new power amp design

I am wanting to build a unique rack tube power amplifier to use with various types of tube pre-amps. I want to build dual stereo or triamp amplifier that I could also use for this purpose.
(Think wet dry wet), in a single or 2u rack space

I want to design an amp that is 20-25 watts each stereo or Triamp with the ability to cut down to a lower power mode like 5 watts or even less. (The reason is this will mainly be used in my home studi for recording and Hopefully YouTube

If stereo only I would require another mono amp like the Fryette power station and that wouldn’t really be as elegant of a solution and not really a new design. The current issue with most amps for the need I have identified, is that most are too much power and requires multiple units.)

So far the closest thing I have found to meet the need ai have identified and it doesn’t do want I am proposing is a 3 watt stereo amp with DI from the mid 90’s.

The reason I want to dual is I want one section stereo of the amp to be EL84 to use with British/Marshall, Vox style amps and some high gain stuff like Friedman, Engl, and Bogner would have that British Plexi-jcm 800 break up in the power amp section to give the tube preamps a more true to form sound.

The other section of stereo amp to be 6V6 to be for Fender, Dumble, Soldano, Peavey 5150, and Most Mesa Boogie style amps. Hoping this section is clean with headroom needed for those style of amps, but versatile enough to work with the various style preamps.

I will also be using this power amp with synergy syn 2 and synergy modules.

I would also like to have a very powerful EQ section with presence, depth, and/or resonance controls. To tailor it for each pre-amp and type of tone.

Would also love to have a DI output as well for recording purposes.

So wondering if this can be done with one transformer or how it can be designed to work and switch back and fourth between the two sections. Can it share the EQ section or is this basically two power amps. I would love it to be a more unified design and use less parts and share the parts that can be shared and just use a switch to switch between the two circuits.

As previously stated, I’ll be using this on our YouTube channel to do demos and reviews. I will rareley have regular amps (heads) that I will use as my personal feeling is preamp
Pedals and modules that can be used with or without a power amp are the future of guitar amps along with modelers as well as making for nice hybrid setups with modelers as well.

I get it, this is a lot and probably all impossible, but if you don’t ask, then the answer is always No.

That and I know Steven likes challenges and puzzles, and maybe it would be a great upgrade
To the synergy system making it more versatile.

I also know the Hughes and Kettner Traxis does something like this with the ability to switch between tube type and power modes. I don’t need to switch to higher power tube modes, I honestly am good with lower power as described above for home studio and recording use and this should still be loud enough for many live situations now days.

Thanks in advance for any info,
Anthony Bommarito.

Sent from Anthony Bommarito’s iPhone

Just get a lxii. It has a volume knob, ya know.

Obviously you didn’t read what I wrote because there is a whole lot more to it that I’m asking for.

Thanks anyway!

There’s no real reason to have low power mode in a power amp. The reason is that most “low power” amplifier functions have everything to do with lowering headroom and nothing to do with why little amps behave differently than big amps. They do introduce distortion and compression, but that’s not in any way the same experience as pounding on a little amp with little transformers.

I’ll avoid the long technical explanation here, but just for example, an amp that is capable of 50W has a power supply and an output transformer that must support that power rating. A 10W amp can only do 10W and pushing it past its clean power limit produces those fun characteristics that a 50W amp will only do at in excess of 50W.

Putting a “5W” mode on a 50W power amp does not magically reduce the physical size of the transformers and power supply when activated. IOW - it doesn’t scale, and therefore their sonic and tonal behavior doesn’t scale either.

We get that people see us putting all kinds of functionality into small packages and think: “what if you guys just do X”. And sure, we are always looking for new territories to explore. If we haven’t come up with your ideal version of a new product yet, it’s usually either because we don’t see the potential, or we haven’t yet released the thing that we think addresses the needs of players in a way that really produces the desired result.

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I understand your point and what you are saying, but for mine and many, many modern home players a 50 watt amp doesn’t meet our needs. Turning down the volume to keep it a level we want doesn’t meet our needs or the point of what I’m trying to achieve or use it for.

There is a whole segment of people not being served in any way by any current offerings, so when you say you don’t think there is a market, maybe do some market research. There is a reason the silent stage has gotten so big, not saying it’s the best thing, but it is what it is. That being said for a home and studio player who also doesn’t need or want the output of a 50 watt amp.

I said I wanted to 20 watts each, but in reality a 10 watt or less is fine, the point of the attenuator (low power mode) is to have 20 max if you did use it live, but even less for home and studio.

Yet you are right less is fine to get the sounds and break up I talked about.

I have recently purchased A Lexicon Signature 284 that’s a stereo 3 watt class A Rack amp with stereo efx loop and DI out. This is the amp I will be using for now due to its 3 watts of power and I can run my preamps in to the efx return and get the power up break up at lower volumes!

That being said what I envisioned above is a modern take on this and would be a lot more versatile and as the guitar universe continues to evolve and big amps continue to become less and less and the market co to yes to Shrink as more and more people move
To modelers (and they will and thinking otherwise is short sighted and probably along the lines of what land lines believed with the advent of the call phone).

This is the way to have real analog tube amps that give a person an analog piece of equipment that they can have many different amps in the form of preamps and use the one that meets their needs in each moment, but takes up less space, is more in line with the power needs of modern players and silent stages outside of a monitor etc…

It also meets the needs of the growing home studio market. This has never been as big as it is now! It no longer just people playing/practice at home, but actually small home studios producing good music is where the market is heading!

So, again What I’m wanting is more than just another power amp, but the ultimate flexible analog tube home studio amp that allows you to get the tones of your favorite amps for home playing and studio use, and if it was capable it could still be used on smaller modern venues or silent stages for those that still want analog.

Hope you can see it now,

Thanks, Anthony.

I get what you are saying, and again, we don’t think that’s a power amp, but a self contained unit that authentically behaves like a full blown guitar amp in a small output package.

In fact we’ve demonstrated that to be the case and produced such a product as you describe:

https://www.fryette.com/valvulator-GPDI/

A new version is in production now that expands on this concept and adds the rest of the features you describe with regard to low power, feel, tone and direct recording functionality, plus the ability to feed external preamps, external amplifiers and reamping and IRs all in one package:

Dave

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Unfortunately that is not even close to the same type of product and solution I am asking for.

First of all it does contain preamps and is actually a full amplifier. This is in itself it’s own product and has its own niche, but not remotely the exact same use class or solve the same problem.

I was asking for power amp that would allow us to use different types of power amps with outboards preamps. I want the ability to use a lot of different preamp types and pair the particular preamp with the appropriate power amp stage.

So, if I was using a Plex (Marshall Plexi) preamp pedal with an EL84 (EL34 type) power section to get that more authentic power amp saturation.

Of using a Peace Hill ODS (Dumble) style preamp I would want to pair it with 6v6 (6L6 style) power amp section for the high headroom and smooth power to get the more authentic Dumble oversrive tones.

These examples can go on and on.

Third I was asking for a stereo or even better Triamp power and for Wet dry wet setups. The valvulator os not this at all. It would take 3 to achieve this. It has a preamp feature that will not be needed, and would have three of the same to accomplish what I said.

While it would work with a modeler, it again would take 2 to do stereo, and 3 to do wet/dry/wet and have 3 preamps that aren’t needed, and the power amp sections do nothing of what I was expanding or asking for.

The only part similar to what I envisioned is that it’s low power, albeit maybe a little to low, and that it had the reactive load with Di out for recording. It needs at least enough power to run a monitor is a live situation.

That is why I suggested 20 watts with an attenuator to take it down to 5, 3, or 1 watt along with the reactive load and DI capability.

I hope this clarifies and you can see what I’m explaining more clearly now, and can understand the very clear difference between the two.

Thanks, Anthony.

Hey Anthony,

Thanks for this interesting idea! I love the creativity of the guitar amp nerd community. So you are after low-power amp that can switch from an EL84 (screen grid) to 6V6 (beam tetrode), that is perhaps MIDI switchable depending on the select preamp?

Are you technical at all? This would certainly be in range of a DIY project, why not give it a go? You could start simple by tackling one amp at a time.

Some thoughts that come to mind.

  • Preamp + Power amp sound a bit more tighter than an integrated preamp and power in a single amplifier. Why? Because they do not share the same power supply. Moreover, when you drive an amp to saturation you are stressing the power supply and the voltage will globally sag.
  • Do tubes have a particular sound? I know we like to think so, but think of tubes as one part - a major part - in a bigger system. It’s the interaction of all those parts that gives the feel.

So I would encourage you to give this a go. Get hold of a 6V6 power amp and a EL84 power amp and do some blind A B testing you, might be surprised.

I do get what you are asking for. And as Dan suggests, this is something that is user-specific enough that your best bet is as a DIY project. The alternative might be some local tech who will take this on if offered sufficient remuneration. You may be talking in the range of $6K-8K for a one off.

The reason I am suggesting an alternate path to your end goal is because of the reality of the design requirement and potential expense.

To accomplish what you are suggesting, given your very specific requirements, you will need three independent power amps and a built in attenuator with a reactive load in one box. By independent power amps, I mean three power transformers, three output transformers and three independent preamp/phase inverter circuits with attendant controls and switches in order to accomplish the range of performance and behaviors set out on your wish list.

Add to that, at least one reactive load, which would have to be able to absorb the full output power of the most powerful of the three power amps, or up to three separate ones if you are planning on running more than one amp at any one time.

Again, the variable power level switch idea is only effective to the extent that it really accomplishes what most manufacturers who offer such features will claim. Otherwise, there will be an inherent compromise in what that feature really delivers. And if you’re willing to accept that compromise, then there is no longer a compelling reason to reject compromise everywhere else to meet your end goal within a reasonable range of cost and complexity.

All of this adds up to the reason I say it’s not a project that we would look at here and conclude that there is more than a very limited market for such a beast.

Not meaning to rain on your parade though. You may very well find someone to do this for you and I would not deter you from exploring all options. I think you will find it very instructive.

When will the new version of the GP/DI be available? You said a newer version was going in to production that had the other features I want.

Also is it still just 1 watt? The reason I ask is a 3 watt version would match the stereo rack amp I purchased to use for wet dry wet! So didn’t know if a little more power was part of the newer version possibly or if it can be modded for the extra power?

Although this still doesn’t achieve what I’m ultimately looking for with switching amplifier types to match their preamps it will suffice for now till I look in to it further elsewhere.

Thanks for your time,
Anthony.

Realized that you aren’t showing it on your site, but others are showing it. I see the differences like loading IR’s so that’s interesting. I also see that it’s still 1 watt.

So, I guess my question is can it be modded to get a little more power out of it, like 3 watts?

Thanks again,
Anthony

Hi Tony,

It’s still the same underlying architecture using a “preamp” tube for output so it can’t reach that output level.

What rack gear do you have? It’s 3W per side? Interesting.

Regards,

Dan

It’s part of the reason I wanted the triamp that’s similar to this to do a wet dry wet setup. That was part of my idea. The 3 watt is more than enough in the studio or home, and honestly even some gigs!

I also found an interesting amp maker that does a very unique power scaling architecture from 0-25 watts that also lets you run the power amp in class A push or class AB push pull and let’s you swap tube types easily. So it’s getting closer, but is currently a mono amp. It’s really one of the most
Incredible designs I’ve come across.

It’s a company called London Power out of Canada.

Thanks for the info,
Anthony

Hi Tony,

Gotcha. Well please do post with progress it will be interesting to see how you get on, and post clips!

I have a friend that spend hundreds of dollars on his books! I have to say the method does seem very clever.

Regards

Dan

I just realized my first reply was rejected for being too short. You asked me what the 3 watt amp I have is.

It is a rackmount Lexicon 284 class A stereo amplifier, it’s actually a full amplifier pre and power amp, but has a stereo effects loop, with a load built in and DI output with speaker simulation. Has to be one of the first of its type from the 90’s.

It is not a reactive load I’m sure from the era, but the load is after the power amp for the DI and I believe can be used simultaneously with a cab while going direct.

So I can use the stereo effects loop for preamps and stereo effects and bypass the preamp for other flavors currently.

It really is a unique piece and something like this is what I was proposing originally with 3 channels of power output instead of just stereo and a reactive load with IR loader. Then took it further by suggesting being able to switch between tube type and topology like the London power stuff.

Of course the power scaling makes it so it could be a studio unit and a live unit even in larger louder gigs.

That being said for now it will meet my needs and may add a valvulator to do the center channel, although I wish it was capable of 3 watts to match and used a real output tube like the Lexicon to do so.

Thanks again,
Tony

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