original EH schematics here...

Johan · October 12, 2005, 09:26:26 AM

http://aronnelson.com/gallery/johan/hot_tubes_78

in my gallery..there is more, among them DOD booster, electric misstress

..I made these copies from a service binder about 10years ago and forgot about them, found them yesterday..might be more somewhere...

johan

Arn C. · October 12, 2005, 10:03:11 AM

Thanks a Bunch Johan!!!

Peace!
Arn C.

Geoff Hunter · October 12, 2005, 10:17:10 AM

Thanks for that!

That Opamp Big muff sch. is saying to me "Go on..... Build me!"

Geoff

Mark Hammer · October 12, 2005, 10:28:28 AM

Thanks. First time I've seen anything for the Full Double-Tracking Effect. A rare bird!

Zero the hero · October 12, 2005, 10:59:20 AM

THANKS A LOT, MAN!!!

RedHouse · October 12, 2005, 11:00:45 AM

I like the "Friends on the couch" pic

mrsage · October 12, 2005, 11:19:36 AM

Quote from: Geoff Hunter on October 12, 2005, 10:17:10 AM
Thanks for that!

That Opamp Big muff sch. is saying to me "Go on..... Build me!"Â

Geoff

That would have saved me some time this past weekend! I brought a friends Op Amp muff back to life, but I was working with a bunch of random different schematics, none of which really quite worked!

So that's for the 1977 version...anyone know if there are differences in the later versions? I know the board changed slightly, but I'm guessing the circuit stayed the same.

Eb7+9 · October 12, 2005, 06:01:26 PM

merci bien ...

no one ever · October 12, 2005, 06:29:19 PM

did puretube design that one?

toneman · October 12, 2005, 09:32:21 PM

good scans!!

thanx!!
T

Jaicen_solo · October 13, 2005, 08:48:00 AM

Some great scans there, i'd be interested in a layout for the slapback echo

Has anybody built that LA Light comp? I'd be interested to read build reports, as i've been looking for a nice opto comp. Any idea how much gain it has??

petemoore · October 16, 2005, 10:41:26 PM

Building the Opamp Big Muff, I'm seeing no cap between the first and second stage, I wonder why no coupling cap wouldn't be there...

Dragonfly · October 17, 2005, 12:10:03 AM

...JUST SAYING THANKS

Johan · October 17, 2005, 12:11:44 AM

Quote from: petemoore on October 16, 2005, 10:41:26 PM
Â Building the Opamp Big Muff, I'm seeing no cap between the first and second stage, I wonder why no coupling cap wouldn't be there...

it uses the first stage to bias the second stage, with a cap in between, it wouldnt work..

johan

petemoore · October 17, 2005, 01:56:25 AM

Ahh..that makes sense then...
Also there's a cap between pin 5 and ground [2nd stage inverting input], I can't make the value out, it looks like 10% is almost readable. I went ahead and just made that one socketed, but I'm just wondering what is 'supposed' to go there.

Johan · October 17, 2005, 02:20:06 AM

Quote from: petemoore on October 17, 2005, 01:56:25 AM
Â Ahh..that makes sense then...
Â Also there's a cap between pin 5 and ground [2nd stage inverting input], I can't make the value out, it looks like 10% is almost readable. I went ahead and just made that one socketed, but I'm just wondering what is 'supposed' to go there.

... 0,01 10%...

johan

petemoore · October 17, 2005, 11:59:17 AM

I'm having alot of trouble biasing the output of the last opamp. Using a 741's, there's not much biasing it, checked everything in that part of the circuit...10 times using DMM Beeping to confirm continuities and R meter to check exact resistantces...the output is 7.55v of 9.04v supply, with the diodes out, 2.55v of 9.04v supply with the diodes in

the inputs sit right around 1/2v...first opamps ins and outs also sitting right around 1/2v.

Johan · October 17, 2005, 12:04:31 PM

the last stage is biased slightly offset with one 820k and one 1M. I dont know what that would result in at the output, but do you get any sound through?..

EDIT.. I just breadboarded that last stage, but using a 5532 ( its what I have here..) and I get 5 volts both at the +input and at the output...so the output follows the dcoffset at the +input...I guess if you accidently swaped the + and - inputs, it would be very different..?..

johan

petemoore · October 17, 2005, 01:54:37 PM

You guessed right, I wired wrong...
Rewired that part now, getting good voltages, and distorted sound.
Tone of the sound is...uh...'messy' sounding...lol, muffy, but just sounds wierd, noisy too. Not gating, only slight movement of input source seems to illicit 'alot of movement' within the circuit....hard to describe other than to say with no more input than a hand muting the strings, the circuit seems to want to output alot more than 'normal'.
Heavy leads sound very thick and muffy...Cool.
All the controls work, and the board seems right, tone goes from deep bass mud to midrangey with some highs, no real high treble, I tried lowering the .0047uf on the clipping stage to .001uf, maybe somewhere in between would be about right for me.
Has good output with 4 of the 6 clipping diodes in it.

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original EH schematics here...