Let's build an amp! Greg's journey to electrocution

[Greg_L]

It might have an effect when generating blossoming feedback because you would want the string's resonance to be in phase with the speaker to get the best positive feedback. That said, the distance between your guitar and the speaker and the frequency of the played note would be critical too. I suppose that's why changing your position regarding the amp enables you to "tune in" on the feedback, like changing the position of an aerial.

In general, I don't think it matters, as you say. The fact that the signal peaks are perfectly coincident says to me that it's just the result of general flip-flopping of phase through the amp and it doesn't matter which way it ends up.

Right. The phase flipping in a gain stage is not really a "time" thing like we'd normally think about with mics and speakers and all that. The phase-flip in an amp is an instant mirror image determined by which piece of the tube you take the output signal from.

[JD01]

This thread lost me when it started to look like the set from The Day The Earth Stood Still.

[Greg_L]

This thread lost me when it started to look like the set from The Day The Earth Stood Still.

There's a lot more to this shit than just sticking wires together. I'm surprised that I even understand the little bit that I can. Most of it does make sense to me though. I kind of get it.

The scope has been invaluable. It's one thing to hear a problem. That's ultimately what matters. But if you can't see and find where the problem happening, then an amp is basically just a bunch of wires stuck together. And it's been interesting for me to see how our tiny little weak puny guitar signals get massaged and manhandled inside a tube circuit.

There's no telling how long it would have taken me to figure out that loop of wire oscillation on the reverb tube without the scope. It would have basically been guessing and trial-and-error. But the scope led me right to it.

[JD01]

Yeah, that must be really interesting when you've worked it out and you start to work out what little bits do and what effect they have on the ultimate tone of the amp - which I guess is what matters!

I was interested in building myself a TubeScreamer for a bit of fun... I kind of want one but don't want to spent money on what is basically the most ubiquitous green box in music... but then I can't be arsed, 'cos while I could follow a diagram and stick things together easily enough (my crap soldering excepted) I want to know why all the bits know what they do and be able to change things and mess about with things with some idea of what the changes should do and try and kind of design my own pedal to a certain extent.... which I guess is kind of what you're doing with the amp now that you have all this shit sorted.

[Greg_L]

Yeah, that must be really interesting when you've worked it out and you start to work out what little bits do and what effect they have on the ultimate tone of the amp - which I guess is what matters!

I was interested in building myself a TubeScreamer for a bit of fun... I kind of want one but don't want to spent money on what is basically the most ubiquitous green box in music... but then I can't be arsed, 'cos while I could follow a diagram and stick things together easily enough (my crap soldering excepted) I want to know why all the bits know what they do and be able to change things and mess about with things with some idea of what the changes should do and try and kind of design my own pedal to a certain extent.... which I guess is kind of what you're doing with the amp now that you have all this shit sorted.

What you would need is a "breadboard". It's like an exploded version of a circuit on a board with jillions of little holes in it. You build a circuit on that board and just patch things together for testing. It's like a physical, tangible version of a schematic. When you get something that works you figure out how to fit all of that into some kind of enclosure. That's probably how most pedals have been born.

For me, I'm not trying to redesign anything. I'm just trying to make a known ancient design work like it's supposed to.

[SweetDan]

There's a lot more to this shit than just sticking wires together...

...I was interested in building myself a TubeScreamer for a bit of fun... I kind of want one but don't want to spent money on what is basically the most ubiquitous green box in music... but then I can't be arsed, 'cos while I could follow a diagram and stick things together easily enough (my crap soldering excepted) I want to know why all the bits know what they do and be able to change things and mess about with things with some idea of what the changes should do and try and kind of design my own pedal to a certain extent.... which I guess is kind of what you're doing with the amp now that you have all this shit sorted.

Since I built those two pedals a few months back, I've really wanted to grok what's going on under the hood. I'm far from being able to look at a schematic and understand what it will do, but I'm starting to recognize common patterns of arrangement of components that are a subset of the circuit network. I don't know if I'll ever "graduate" to anything big, like an amp, but this has all been very interesting so far.

Anyway, here are a couple links that have helped me understand a bit (in order of simplest to most complex/theoretical):

http://www.generalguitargadgets.com/how ... istortion/

http://lcamtuf.coredump.cx/electronics/

https://wiki.analog.com/university/cour ... /chapter-9

That, plus some of the videos from the guy that runs http://www.diyguitarpedals.com.au/ (https://www.youtube.com/user/chromespherecom), though I always watch the videos at 2x, since he can ramble. Also, getting off into the weeds, some of the discussion at http://tagboardeffects.blogspot.com/ is useful, but usually centered around any one specific circuit.

[JD01]

Cheers, Dan

[Lt. Bob]

Greg's gonna end up being a full-fledged amp guy.

The biggest requirement is being interested enough to put some time into learning it which he is, plus having a mind that can understand math type concepts.

Greg tends to disparage himself but I consider him one of the smartest and most talented guys I know and ask yourself, how often do I say such things about anyone? (never would be the answer)

Greg's a freakin' great drumber ...... a GREAT rhythm guitarist ...... his leads are as good as he cares to be ...... I'm betting he was a great car guy and now he's gonna be a great amp guy.

I feel fortunate to know him ..... someday he'll give me a GREAT eulogy.

[Greg_L]

Greg's gonna end up being a full-fledged amp guy.

The biggest requirement is being interested enough to put some time into learning it which he is, plus having a mind that can understand math type concepts.

Greg tends to disparage himself but I consider him one of the smartest and most talented guys I know and ask yourself, how often do I say such things about anyone? (never would be the answer)

Greg's a freakin' great drumber ...... a GREAT rhythm guitarist ...... his leads are as good as he cares to be ...... I'm betting he was a great car guy and now he's gonna be a great amp guy.

I feel fortunate to know him ..... someday he'll give me a GREAT eulogy.

Haha thanks a lot Boob. I agree with all of that.

Most of this stemmed from the same reason I got into cars - I just wanted to do it myself. The more I learn about amps, the more I realize that it's amazing that they can even work at all. Lol. And I'm only about 125 years behind the curve.

[SweetDan]

...I'm far from being able to look at a schematic and understand what it will do...

Thank goodness there's stuff out there like this: https://www.electrosmash.com/mxr-phase90

[WhiskeyJack]

...I'm far from being able to look at a schematic and understand what it will do...

Thank goodness there's stuff out there like this: https://www.electrosmash.com/mxr-phase90

Which lead me to this and answered my question i had about a week ago as to why that black gunk was all over the board.

Great share SD.

[Greg_L]

Did a pretty serious mod to the amp.



Purple pilot lamp jewel

[rayc]

Tidy. Did Prince use one?

[Greg_L]

Tidy. Did Prince use one?

Lol. I think Prince was a Mesa guy.

[JD01]

Greg, you need a logo. Would fit perfectly to the left it the purple light.

[rayc]

Greg, you need a logo. Would fit perfectly to the left it the purple light.

Gregtronics Rebastard
What was your name for it Greg?
Dualchronic?

[Greg_L]

Lol. I don't know. I call it the bastard or deluxe retard, but since it's spent about two months sprawled all over my wife's nice dining room I'll probably name it after her.

[liv_rong]

That light looks bright as fuck!

[Mr Clean]

That was an excellent, albeit long read. Cheers for all the detailed info Greg. I really enjoyed it.

You should call it "The Babygirl"

[Greg_L]

That was an excellent, albeit long read. Cheers for all the detailed info Greg. I really enjoyed it.

You should call it "The Babygirl"

Ha, thanks.

The amp is sweetening up little by little. Breaking in. It's really pretty awesome. I still can't believe I did this.

I've tried a few minor mods just to try stuff out. A few Silverface mods....none of them stayed. None of them made the amp any better.

One thing I have done and stuck with was I upped the 470 screen grid resistors to 1k just to get a little more spread between the plates and grid voltages. Not really a tone thing, but more a stability/longevity thing. So far so good. I have bashed on this amp pretty hard and it's still going strong.