old Geddy "smooth distortion" question

[Hizzoner]

I came across this and was intrigued.
I confirmed that an ashly sc-40 preamp manual has the advice typed in it..here is the post

Re: Geddy:"Now, here's the secret of the overdriven tone: The Ashly SC-40 has an effects loop - simple in/out 1/4" phone jacks. Smooth distortion can be obtained by wiring two 1N914 diodes paralleled in opposite directions between the ring and tip connections of a standard 1/4' phone jack and inserting into the effects loop SEND. All this added to his unique playing technique gave him that mysterious mammoth bass sound. "

Is this likely? Anyone tried it?

Would this work for any amp/preamp with an effects send?

Is there any potential damage that can be done to am amp or preamp by doing this?

I am really interested..I also assume they are talking about modifying a jack not a 1/4" plug...

Anyone able to diagram such a description for an electronics noob?

Thanks everyone for your time

Mark

[Hizzoner]

sorry..this should be a plug not a jack.........

[Hizzoner]

from ashley sc-40 manual:

"smooth distortion may be produced by wiring two 1n914 diodes paralleled in opposite directions between the tip and the sleeve of a phone plug and inserting it into the effects send. A foot switch can be wired in series with the tip of the plug to switch out the distortion"...from the manual..circa early 80's

I still have the same questions although they apply to a modified plug, not a JACK..which mkes this experiment easier IMO...

[Hizzoner]

tried it on an old plug and it silenced the walkabout head..kind of think it is a function of the send jack being plugged in but no return jack..hmmm..maybe unique to just the ashly preamp???????

[Mark Olson]

Well, logically if you're going to send your signal out the send jack and through some diodes, you do eventually want your signal to return to the preamp, don't you?

Diode clipping can be very effective. There is at least one company I know of making a dual diode device that you can simply wire into a passive guitar to obtain an overdriven tone. These kinds of things are very sensitive to the output of your guitar though, you have to have the exact right guitar output to get the right sound, and I've been told simple passive diode clipping circuits, some of them at least do not work well with active instruments. You may or may not do best with a high impedence signal running through them.

[12bass]

The idea above appears to use two diodes in the effects loop. Presumably this would be close to line level, so instrument output variations shouldn't matter much, as they would be accounted for by adjusting input gain. Haven't tried it (yet), but this should work in practically any effects loop.

[tomhanzo]

Interesting. I know Jack Bruce did a trick like this with his EB-3. I've read and researched it all i could.

It seems Dan Armstrong put a diode in place of the normal components of the tone section on the bridge pickup. I have yet to try it myself, but am about to on a junk pbass i have laying around. I asked a friend of mine that builds stuff, and he said it would work.


I have a question now that I've thought about this all. Wouldn't this kill some volume? If not, why not make it in a pedal. I've always wondered why someone couldn't just make a pedal with nothing more than two diodes set this way.

[ZombieSpacebat]

Someone probably could tomhanzo, it would probably have to be custom though because i assume most big companies want to make the latest, greatest, bells and whistles pedals rather than something that simple

[tomhanzo]

Originally Posted by ZombieSpacebat

Someone probably could tomhanzo, it would probably have to be custom though because i assume most big companies want to make the latest, greatest, bells and whistles pedals rather than something that simple

but the big question i have is why isn't the simple two diode clipping popular. Everyone wants simple fuzz circuits and all. why not just make a double diode? What are the cons?

[The Lurker]

Isn't the Stewmac Black Ice circuit something like this?

[Mark Olson]

I'm not certain how one would go about wiring an effects loop on just a preamp. Also I don't know if this loop is post EQ, whether the EQ is passive or active, and what it's changing the impedence of the signal to. I assume if the manual recommends putting diodes in the loop, having the loop operate at parameters that would work with them would have been a design consideration.

People do make passive clipping pedals for bass. But the problems I assume are the reason most people don't pursue building such things are as I've said, they may not be friendly to all basses and could sound very inconsistent from guitar to guitar. It's also hard to explain to bassists if your pedal won't work well after a buffer, which the diode clipping circuits I've seen don't, because people have a hard time understanding the concept. Look on harmony central, even some guitar players look at things like a pedal using PNP germanium transistors and having a reverse ground as a "design flaw"! Bassists are even more likely to view anything that doesn't sound good with their active basses or after their TU-2's and OC-2's as a "design flaw".

[Hizzoner]

update:
I just messed with an old small patch cable..took one of the 1/4" plugs and sloppily soldered 2 diodes(got em at radio shack) in reverse order, plugged it into the effects send and the other end(unaltered) to the effects return.(.just like ashly manual says) of two different amps(mesa and TFunk) AND..........

got a real smooth distorted sound...no pedals or tubes.....there was a difference based on the output of the bass in the distorted tone..I used a passive jazz and a MM classic stingray and both sounded good... wow...has me thinkin'

of course I could be wrong and YMMV

[fokof]

I have one SC-40 , i'll remove the dust and try this trick !

[tsunami1052]

Can you post a picture - Please!

[I<34080]

Very cool, wish I knew how to solder so I could try it out.

[tomhanzo]

Originally Posted by I<34080

Very cool, wish I knew how to solder so I could try it out.

soldering is very easy. You just have to play around with it till you get the hang of it.

Now I have to try this. I assume you just took the normal cable and just connected the diodes across the "hot" wire and "ground" wire where they meet the plug. Right? If so it wouldn't matter which jack the plug was in. I think...

[Hizzoner]

yup...took a short patch cable and unscrewed the plug cover/pulled the thin plastic sleeve off the connector...then soldered the 2 diodes in opposite directions between where the two copper wires connect to the plug..in fact I only used a touch of solder..was able to use the copious amount of solder already on the plug from when the cable was manufactured..

BTW I am a total NOOB at electronics and have only done this kind of thing before when installing new P pickups....I did a sloppy job but it works

[tsunami1052]

Go to Radio Shack buy a pack of 1N914 Switching Diodes ($1.50 for 10) and a Solderless - mono 1/4" Phone Plug ($3.99 for 2). Back-out screws, rap diode wires around screw post on ring and tip connections make sure one diode is opposit direction from the other and tighten screws. No soldering required. Bend diode wires carefully and screw the plasic plug cover back on. Plug into the effects send loop on amp and your done.

Worked good on my Genz Benz Shuttle 3.0 amp and passive Jazz bass.

http://i687.photobucket.com/albums/v...4/IMG_0514.jpg


P.S. Did not work on the effects send on Eden WT400 but did work on the Eden WTX264. It will rob a small amount of volume and low end, but hey its a cheap OD circut for under 10.00 bucks and its fun to mess with as a Saturday project. Second one I did came out looking alot cleaner.

[tomhanzo]

Yeah the shack is the place.

So you didnt have to run the signal from your send plug back to your return jack?

[tsunami1052]

Not on the Genz Benz or the Eden WTX264 - I could not get it to work the same on the WT400 might have to use a patch cable like Hizzoner to complete the circut from send to return on the wt400 effects loop.

Maybe someone with more circut knowledge can explain why.