when making a stompbox version of an amp....

[pinkjimiphoton]

what am i looking for here?

[Gus]

PRS sold a solid state amp

[pinkjimiphoton]

ahh, ok...

ok, getting ready to go play with my breadboard.. this is what i got atm, and am sure some values will be changing as i play with it:



thanks keppy, jon and gus for the insites and advice... i'm goin' in, wish me luck, no doubt i will need it!!

[Keppy]

Good luck! Q2 looks okay to me now.

[pinkjimiphoton]

thanks keppy, i got side tracked, hopefully i can start messing with it soon. life.

[Paul Marossy]

Just an observation:

I'm working on a stompbox version of a tube circuit right now. I've found that in some areas of the circuit I can't do an exact copy of the tube schematic because it just doesn't work quite the same with low voltage solid state devices. I've had to mess with some cap and resistor values to get approximately the same sound as the real deal, but most of the circuit stays more or less the same.

[pinkjimiphoton]

thanks paul that's what i'm thinking, hence why i'm speccing different caps and stuff.

the fetzer at the end is probably unnecessary, it's just there in case it needs a good kick in the ass on the way out.

hopefull to get to this soon...it's killin' me sitting here with my thumbs up my butt doing nothing.

[Paul Marossy]

thanks paul that's what i'm thinking, hence why i'm speccing different caps and stuff.

the fetzer at the end is probably unnecessary, it's just there in case it needs a good kick in the ass on the way out.

hopefull to get to this soon...it's killin' me sitting here with my thumbs up my butt doing nothing.

Theoritically, yours shouldn't be as hard to get as my tube emulation project (it really is a preamp section of a tube amp). Since the original you are "copying" is operating on WAYYYYY less than my 300V, you're almost in the ballpark with just 9V (looks like the total voltage swing is 40V?).

Looking at your schematic of the original, the output section is also part of the overall sound - power transistors and an output transformer that will also add its own thing to the mix. That's the stuff that is not so easy to emulate...

[pinkjimiphoton]

agreed. i think that was gus's point, too...

the one i had way back sounded great cuz it was full blast, effectively becoming a ge fuzz.

i have a couple small output transformers kicking around still, i may try one of them as an interstage deal at some point, as transformer saturation sounds really good... very warm and brown.

i'm looking more to make a fuzzbox. cuz i'm an addict.

[Keppy]

you're almost in the ballpark with just 9V (looks like the total voltage swing is 40V?).

Actually, the portion of the original Jimi is emulating runs on single-ended 15.5v, though the power section runs on 20.

[pinkjimiphoton]

i just heard from the guy i bought the amp from on ebay.
he still hasn't shipped it apparently, and now wants another 10bux to ship...wtf.

i told him to send me a goddamn invoice...   

[Paul Marossy]

you're almost in the ballpark with just 9V (looks like the total voltage swing is 40V?).

Actually, the portion of the original Jimi is emulating runs on single-ended 15.5v, though the power section runs on 20.

Dang it, I need to pay more attention sometimes while I'm visiting the forum while at work. 

Anyway, I was looking at the output section thinking it was like a 20V-0V-20V thing, but now that I looked at it again, yep it's -15.5V. That is a weird power supply & output section... what's with the negative voltages?

[Paul Marossy]

i have a couple small output transformers kicking around still, i may try one of them as an interstage deal at some point, as transformer saturation sounds really good... very warm and brown.

You could try a small audio transformer. Not sure what results you might get with it though. You could maybe try a gyrator tone control to try and simulate a resonance at a certain frequency, if the real amp exhibits any resonance at a certain frequency.

[teemuk]

what's with the negative voltages?

PNP transistors.

[Paul Marossy]

what's with the negative voltages?

PNP transistors.

That's what I thought at first. Looks weird when you're used to primarily working with NPN devices...