Designing a stereo tube guitar amp

[R.G.]

... and I have a "Cape" badge to prove it.

Ooooh, cool!

... er, how does that improve the sound of amplifiers? Just curious. I have an "Austin" badge, but it's never helped my amplifiers much. I think there must be something I'm missing, though. 8-)

[Alex R]

Yeah Jamie the trouble with a lot of people who want you to design and build an amp for them is that they want something more complex and tricky than the manufacturers want to build, and reckon without the R&D you'd have to do to make it work. Yes, it's the sort of thing you might try as a personal project, but for a customer? Too many pitfalls, too much chance that it won't be the dream amp after all, and above all way too many man-hours.

[mooreamps]

Ooooh, cool!

... er, how does that improve the sound of amplifiers? Just curious. I have an "Austin" badge, but it's never helped my amplifiers much. I think there must be something I'm missing, though. 8-)

Yes it does. The ah, "two sisters" who have been clients on mine for a couple years now seem to think so, and since they are like , Well Known, in the recording industry, that's good enough for me.. -sorry :|


-g

[Diablo]

Here's a stereo guitar amp from 1961. You can see that the PT and two OTs are in the bottom chassis on the floor of the amp with two PIs. It has a two channel preamp (A&B) in the top chassis. You can select stereo, A, B, AB. Plugging a guitar into channel A with the selector switch on stereo powers up one OT and one speaker. With the selector switch on A, you get two OTs and two speakers with double power.

[R.G.]

Yes it does.

So, how does that work? How exactly does a Cape badge improve the sound? Tecnically, not fuzzy anecdotes. Sir William Thomson, Lord Kelvin said it this way:

"In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be." [PLA, vol. 1, "Electrical Units of Measurement", 1883-05-03]

We've been here before, haven't we?

So, same question: Howzat work? Link "Cape badge" to "amplifier sound" for me. In numbers, as befits a scientist of your stature.

The ah, "two sisters" who have been clients on mine for a couple years now seem to think so, and since they are like , Well Known, in the recording industry,

... and as we all know, being Well Known [sic] in the recording industry means that anyone who has attained this level of, er, being well known is a paragon of discrimination and lucid exposition of technical matters. I know a guy who is Well Known [sic] that likes ketchup on rice. Does that make ketchup on rice a suitable recipe for a chef to adopt as a signature dish?

that's good enough for me..

That's too bad.

As a self-professed scientist (You're still claiming that for bragging rights, yes?) you surely know that anecdotal evidence is accorded the same level of respect in technical endeavors as, say, used Kleenex, right?

So if someone - anyone! - liking your amps is convincing proof to you that a Cape badge makes amplifier sound better and you can offer no other technical explanation for the effect, you're either effectively resigning your scientist claims or else offering a stinging self-evaluation that would make a good scientist cringe, I think.

Quick question - do they have cleaning crews at the Cape to do janitorial work? Do they have Cape badges, or do "Rocket Scientists" usher them around? Or do the "Rocket Scientists" do cleanup? Plumbing repairs on the restrooms? Howzat work?

And do the cleaning crews do amplifier design?

-sorry :|

I had to edit out my first response to this. I could not stop laughing long enough to finish it.

The question is whether you're sorry personally or professionally. Or both, I guess. Could you clarify that point?

[Enzo]

John's original premise was a customer wanting a stereo amp. What I can't quite get is why then would it be desirable to mix the two channels together into a single output, Class A or otherwise?

The result will be a mono mix, which may sound wonderful, but would not meet the customer's spec.

[mooreamps]

John's original premise was a customer wanting a stereo amp. What I can't quite get is why then would it be desirable to mix the two channels together into a single output, Class A or otherwise?

The result will be a mono mix, which may sound wonderful, but would not meet the customer's spec.

Maybe the same reason why I did one build with a two channel input. He was going to drive it with a stereo chorus effect pedal... I may pick up one myself for a future build, and then just see for myself what it sounds like...

-g

[Chuck H]

Enzo, I think Gary's idea is to process and keep seperate two signals via phase. No, that's not stereo. But it is two different outputs from the same OT. Neat trick, but not stereo. And so not applicable to the OP's cause. Gary just wants us to know he can do it.

[R.G.]

The problem with mixing generated pseudo-stereo from phasers, choruses, flangers and so on is that the almost universal way these are generated is to add and subtract the phase or time-delayed signal to/from the dry signal. If O is the original signal and D is the delayed signal, you get out O+D and O-D, or, done another way, O+D and D-O. When you mix (additively) those two signals, you would theoretically get either O or D, but not both, and certainly not a stereo mix. The cancellation is not perfect, but it's what's behind those "vocal removers" you sometimes see.

This would not be the case for doing further operations to delay/shred/toneshift/bandlimit/band-distort/etc. that is used in some pseudostereo setups, but most of the common effects don't bother.

[mooreamps]

Gary just wants us to know he can do it.

Anyone can do it... :}

-g

[mooreamps]

That's a bit like asking what kind of person most likes to eat pizza- someone from Italy, New York or Chicago. There are wonderful recorded examples of chorus effects in each of the above genres. I don't really understand why you asked.

For example, I would not install an electronic power brake into a build intended for use by a Jazz player. That's not the kind of tone those guys want....

-g

[mooreamps]

Enzo, I think Gary's idea is to process and keep seperate two signals via phase. No, that's not stereo. But it is two different outputs from the same OT. Neat trick, but not stereo. And so not applicable to the OP's cause. Gary just wants us to know he can do it.

Oh, don't even think that's even the half of it... I'll bet Mr. Austin Badge has already started mouthing off to his friends claiming it was all his idea, instead of mine... ..... .... :\



-g

[R.G.]

Oh, don't even think that's even the half of it... I'll bet Mr. Austin Badge has already started mouthing off to his friends claiming it was all his idea, instead of mine... ..... .... :\

Tee-hee!
Say, Gary - two questions:
1. What exactly makes you think that everyone is trying to claim your ideas? Was there some traumatic incident in your technical childhood? It's come up many times from you.
2. What exactly makes you think that messing with phase funnies in stereo signals was new with you?
I refer you to: Classic Stereo Imaging Transforms and especially to the reference to Blumlein's => 1931 <= patent on mixing sum and difference signals. Not to mention the 52,000 results Google comes up with for the search term "multichannel "L+R" "L-R" mixing width".
I guess there's a third question - what makes you think your ideas are good enough for Mr. Austin Badge to claim?

And since we're talking about badges again - you brought it up! - there's some unfinished Cape Badge business. Since you DO claim a "Cape badge", let's go back to the set of questions you decided you'd rather not talk about from a little earlier. I've reproduced them here for your ease in answering. Or would you rather talk about something else?

Originally Posted by mooreamps View Post
Yes it does.

So, how does that work? How exactly does a Cape badge improve the sound? Tecnically, not fuzzy anecdotes. Sir William Thomson, Lord Kelvin said it this way:

"In physical science the first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely in your thoughts advanced to the state of Science, whatever the matter may be." [PLA, vol. 1, "Electrical Units of Measurement", 1883-05-03]
We've been here before, haven't we?

So, same question: Howzat work? Link "Cape badge" to "amplifier sound" for me. In numbers, as befits a scientist of your stature.

The ah, "two sisters" who have been clients on mine for a couple years now seem to think so, and since they are like , Well Known, in the recording industry,

... and as we all know, being Well Known [sic] in the recording industry means that anyone who has attained this level of, er, being well known is a paragon of discrimination and lucid exposition of technical matters. I know a guy who is Well Known [sic] that likes ketchup on rice. Does that make ketchup on rice a suitable recipe for a chef to adopt as a signature dish?

that's good enough for me..

That's too bad.

As a self-professed scientist (You're still claiming that for bragging rights, yes?) you surely know that anecdotal evidence is accorded the same level of respect in technical endeavors as, say, used Kleenex, right?

So if someone - anyone! - liking your amps is convincing proof to you that a Cape badge makes amplifier sound better and you can offer no other technical explanation for the effect, you're either effectively resigning your scientist claims or else offering a stinging self-evaluation that would make a good scientist cringe, I think.

Quick question - do they have cleaning crews at the Cape to do janitorial work? Do they have Cape badges, or do "Rocket Scientists" usher them around? Or do the "Rocket Scientists" do cleanup? Plumbing repairs on the restrooms? Howzat work?

And do the cleaning crews do amplifier design?

-sorry :|

I had to edit out my first response to this. I could not stop laughing long enough to finish it.

The question is whether you're sorry personally or professionally. Or both, I guess. Could you clarify that point?

[Chuck H]

I think Gary's last post was a joke humbly aimed at himself R.G.

It would help if I knew who Austin Badge is...

[Steve Conner]

I think an Austin Badge is what you wear, if Austin is the closest you've got to working at Cape Canaveral.

Anyway, this is classic trolling. Stop rising to the bait, RG.