OT: practice amp schem

[Joe]

http://www.diystompboxes.com/analogalchemy/amps/guitaramp.html

Just add a preamp...

The goal was an inexpensive amp to build. Most of it was recycled amp parts and other junk. I might be a little early posting this, since I just got it up & running the other day, but I think it's alright. This is a "get-it-done" sort of circuit, so don't expect low THD. It's surprisingly loud and good-sounding, though.

[Fret Wire]

Nice. One question: .47/5w. Do you mean 47ohm/5w? The decimal point threw me off.
Looks like the Jensen Mod 10-50 would be a nice, affordable speaker for it. It's 10", 50w, 4ohm, and about $28. I put one in a SF Champ that I got cheaply because someone hacked the baffle. Sounds great.

Nice project Joe.

[Joe]

It's 0.47 ohms. Yeah, it's a pretty small value.

[Joecool85]

Any sound clips?  Looks like a sweet little circuit.

[jrc4558]

And I happen to have just the chassis for it! Thanks Joe! Bless me on my first solid state guitar amp! Some questions though:
1) why is the rectifier ground not connected to chassis? (curious)
2) in the EMH (electronic math helper, although I loved the Voyager pun), while calculating the tapered potentiometer, what does the taper percentage stand for? what's the graphical representation?
Thank you for your wonderful designs!

[Joe]

Is Voyager the one where the captain lady sounds like she has a clothespin on her nose all the time?

The taper works like this. To emulate a log taper, use about 90%. A reverse-log would use 10%. (or vice versa, don't remember.) But you can specify 75% or whatever. It won't be smooth anyway, since it's only an approximation.

I was mistaken about the grounding. Sorry about that.

[jrc4558]

I was mistaken about the grounding. Sorry about that.

So all the grounding points on the schematic are common to chassis, correct? Just want to make sure before I attempt a layout.

[jrc4558]

and one more question - why a capacitor across the power switch? what's the benefit? reason - curiosity.

[Joe]

Schem fixed, thanks for pointing that out. I would avoid using the chassis as a ground return, and just run a single thick wire from the negative rail to the chassis. I just rewired mine that way. I also left out the switch capacitor, not sure what it's for. (power supply based on design in book.)

There really should be a diode clamp at the input to prevent overloading. The amp is designed for about 1-volt peak-to-peak but not much more. I'll add this feature in the near future.

*Edit: Just simulated the diode clamp and added it to the schematic.

[idlechatterbox]

QUOTE
" None of the part values are critical, so close-enough values will probably work."

Now that's a DIY project that I can support! I'll try the easydrive and then go for the practice amp. 

Thanks Joe

[Marcos - Munky]

Interesting. Soundclips, photos?

[David]

Bump...   
Any build reports on this yet?

Joe:
How much heat did your prototype generate?

[Brymus]

WHere can I get the shematic for this ?
The link keeps giving -error 404 server not found apachee blah blah blah...
Even something close would be appreciated THANX

[sean k]

Is this what you meant? Otherwise just drop the stuff after alchemy/ and paste it into the address bar and you'll see Joes stuff.

[Brymus]

Is this what you meant? Otherwise just drop the stuff after alchemy/ and paste it into the address bar and you'll see Joes stuff.

I cant see the image but when I quoted you I got the address and viewed it.
I think thats what I want.I saw some guys at SSguitaramp.com had succes with this amp.
I trying to find it has been hard.
I still get Ooops link appears broken when I try your suggestion of leaving everything before alchemy/ off.??
Has anyone here built this amp?

[Vitrolin]

the link doesn't seem to work