Distressor vs. 1176

[dale116dot7]

Both the Distressor (EL8) and the 1176 appear to use the same topology. I only have an EL8 (not an 1176) - how close do they sound? The EL8 circuit seems really similar to the 'new' 1176 - the one on the Jakob's website - except substituting op-amps where the 1176 uses discretes. The more I stare at the 1176 schematic and the EL8 the more they look the same to me. The biggest differences I see is there is a circuit to unbalance the JFET to introduce the distortion characteristics (as far as I can tell) and the switches in the 1176 are replaced with 4051 mux chips. Even the attack/decay stuff looks the same.

[gyraf]

Do you have a schematic?

Please..?

:-)

Jakob E.

[dale116dot7]

I don't have one yet, though I might be able to scan some of my hand-drawn notes so far. It's almost the weekend so I won't be in to work again until Monday. Also, my vapour deposition supplies came in so I might be setting up a nickel/gold evap system this weekend.

-Dale

[Ol' Betsey]

Originally posted by dale116dot7
Also, my vapour deposition supplies came in so I might be setting up a nickel/gold evap system this weekend.

-Dale

Sounds fun!

R.

[dale116dot7]

I need to get a good vacuum pump, and also run three wires into the vacuum canister. It's pyrex so I guess I'll have some fun figuring out how to do that. I gotta get some machine tools to make the backplates too. Some bits for the mill and a couple tools for the lathe.

Anyways, I stared at the Distressor for a bit of time this morning, and drew out most of the schematic. I'll scan it and post it on Monday. It's literally an 1176 with op-amps. The distortion generator is achieved by deliberately unbalancing the channel modulation distortion compensation circuit. Look at the 1176 schematic, there's a 10k from the JFET to ground. That's driven by a buffered audio signal. They leave that part alone. The other part of the compensation circuit is the high value resistor (500k in the 1176) from the output via a trim pot to the gate of the JFET. The Distressor intentionally throws a resistor in there to make some 2nd harmonic via the JFET. To get distortion 3 mode, they add a bunch of gain before feeding the JFET, and lower the gain at a subsequent stage.

One thing to be cautious of: There are diodes there that look like they should be clipping diodes for distortion generation. They are not there for that purpose. They are there to attenuate the signal on an open switch because the 4051/4053 chips will conduct if overdriven. The switches are driven to virtual ground where they are in the circuit, so the diodes will only conduct with the switch open.

I've seen analog mux feedthrough in my automotive work, and they have a special analog mux chips (74HC4851) for that purpose. GM uses them in their controllers as Delco number 48153 - in case you're into looking at that kind of stuff. They are not suitable for audio but they contain these clamp diodes so one sensor connected to 12 volts (a short circuit) does not disable every sensor. With one bad sensor the car will usually run, though poorly. If you trash more than one it's unlikely that it'll start and run.

[dale116dot7]

Schematic is here:
www.telusplanet.net/public/dulan/distressor1.jpg

[meatballragu]

Hi, I just read this thread to find someone has drawn a schemo of the distresor. The link to it is broken. Can someone share that info again please? that would be VERY appraciated.

Thanks.

[amorris]

to me the distressor is a much more aggressive 1176. if you spank an 1176, thats about what you generally get from the distressor. there is a top end distortion that is very "1176" and that is about medium "distressor". if that makes any sense.