Designing a stereo tube guitar amp

[mooreamps]

I've thought a bit more about your idea and I've had some thoughts.

Are you an experienced amp builder? Have you built a high gain preamp before?

I am a retired Senior US Navy ET. In my day job I do electrical engineering on spacecraft. You could say I am gaining experience as an amp builder with 9 units completed ; using my fixed bias circuit in my high gain preamps. My current project is based on an AB763, but my P/I has a switch that will allow it to do both S.E. and P/P outputs ; hot switchable ; in sort of my "mad scientist" kind of way. :}



-g

[Amp Kat]

Have to agree with a lot of this post and IMO don't see anything wrong with two power transformers since the output is in series with the power supply would make it more of a true stereo and could have an effect on the overall noise and coupling. Also agree on the grounding issues especially with different types of preamps and most of the stereo amps you see are exact replicas with a ground plane seperating the two preamps from side to side. This way if there is a problem you can troubleshoot is much easier than if it's all crammed together and you'll have better isolation from side to side. There is a ton you can do with the preamp and design and depending on how much gain and what voicing you want will determine the topology but using Cathode followers will increase the tube count and make it bigger so I have to part with John also on how fast this thing can grow.

[Chuck H]

Gary

You should just tag the bottom of your page... "I'm a space program engineer (or rocket scientist, whatever you prefere) and I design amps using exclusive and proprietary technology. Don't ask me how I do it because I refuse to validate or share my reinvention of electronic theory."

You could get it printed on business cards too.

It would save a lot of time. When I pick through your posts a theme seems to shape up. You like to tell people that you are a space engineer and you like to tell people you invent never before seen technology. Doing this seems very important to you. OK. But sometimes it's a little out of context.

I'm just trying to figure out the point of this response to Jamie's post to someone else???

[mooreamps]

I've thought a bit more about your idea and I've had some thoughts.

Are you an experienced amp builder? Have you built a high gain preamp before?

I am gaining experience as an amp builder. I have 9 units completed ; currently working on #10..

Back to the subject at hand. . I would still favor doing it with the 2 channel preamp feeding "mono" twin power tube power amp. I think the two signals would mix about as good inside the primary winding of the O/T ; and I would probably do it all in Class A ; regardless if the O/T was S.E. or P/P...

-g

[Chuck H]

OK

[MWJB]

I think this thread is getting a little off tangent, generally...

A stereo amp isn't going to give you chorus, without some kind of delay effect.

It's perfectly feasible to blend 2 preamp voices and put them through one OT, IF both preamp channels are in phase & IF you don't really care about stereo perspective (somewhat moot if a combo with all speakers on the same plane).

If you have true stereo, each OT driving it's own speakers, and channels are out of phase, then you can correct this at the speakers.

Building a true stereo amp is a simpler concept if you just grasp that it's a 2 channel amp with 2 PIs & 2 OTs. Layout will be critical though. Don't try and stuff it in a small chassis.

[mooreamps]

I think this thread is getting a little off tangent, generally...

Yes, I would tend to agree with that..

A stereo amp isn't going to give you chorus, without some kind of delay effect.

I went to the GC here in San Jose to pick up a couple of preamp tubes, and took the time to look at some of these stereo effects pedals.. I would still set it up as a two channel preamp feeding a Class A PA. Sure, it's not true stereo, but the delay created by the effects pedal on the second channel should blend the delayed signal on the second channel with respect to the first channel.. You would need two 1/4 inch input jacks on the chassis ; one for each preamp channel ; and that maybe enough to create the effect. Secondly, I've put two preamp channels inside a modded VJ chassis before ; on one build ; so I already know this is possible...

-g

[R.G.]

I am gaining experience as an amp builder. I have 9 units completed ; currently working on #10..

That explains a lot.

[Chuck H]

Hey now... I've only built seven amps from scratch. I've rebuilt, gutted, modded and repaired too many to remember in almost twenty years at this.. Point is, maybe Gary is accounting for his experiences elsewhere. Did you know he is a rocket scientist?

[mooreamps]

That explains a lot.

Not really. As a young US Navy ET, I've worked on 5 KW and 10 KW HF transmitters, and VHF transceivers ; all tube. Plus the water cooled 5 KW TWT's and 10 KW Klystron SHF power amplifiers. Also High Power Surface to Air Radar.... { heh, heh, heh, }
But, that was a few decades ago... :|

-g

[imaradiostar]

I am a retired Senior US Navy ET. In my day job I do electrical engineering on spacecraft.

I didn't mean to call your skills into question- my question was directed at the original poster.

jamie

[R.G.]

Not really. As a young US Navy ET, I've worked on 5 KW and 10 KW HF transmitters, and VHF transceivers ; all tube. Plus the water cooled 5 KW TWT's and 10 KW Klystron SHF power amplifiers. Also High Power Surface to Air Radar.... { heh, heh, heh, }
But, that was a few decades ago...

OK, so you've worked on maintenance of military RF equipment decades ago, and built nine guitar amps.

As I said, that explains a lot.



Quick question: ever work on fuses?

[imaradiostar]

For the record- the real rocket scientists in our country are in Houston, Huntsville and Cape Canaveral.

John Fisher- are you an experienced builder? I ask because an amp such as you describe is likely to be difficult to build and make operate correctly.

I've built a stereo amp. It amounted to a pair of 50 watt Blackface Fenders in one chassis. It was a large beast of an amp- a little bigger and heavier than a Fender Twin. I used the amp as part of a multi amp rig. It was fun but it was a pain to lug around. It was also something of a disaster to troubleshoot and had a limited sound.

I would build a multichannel stereo amp for myself. I would not build such an amp for someone else- too much to get right, too much that could go wrong.

I would, however, build a simple stereo amp that would work well with pedals. I'd be tempted to build it with some sort of switchable mid boost/EQ such as lifting the tone stack mid control. That would make for a nicer clean sound a la fender and a better dirty sound with pedals with the mids up. It could also serve as a sort of a solo boost.

The real advantage- it would be simple to build and simple to troubleshoot!

Jamie

[mooreamps]

For the record- the real rocket scientists in our country are in Houston, Huntsville and Cape Canaveral.

"For the record" ; there are no "Rocket Scientists" in Cape Canaveral !! We live here in Sunnyvale, and we travel to work at the Cape, and I have a "Cape" badge to prove it.

So, "for the record", put a sock in it. :}


-g

[Chuck H]

Hey Gary, how long have you lived in that area?