Pepper Shredder MKII

[dorrisant]

Has anyone built this circuit:

http://www.tube-town.net/diy/lov/lov02-peppershredder-eng.html

NOTICE: This is not version I with a tone knob... it is version II with a tone stack in it. Very similar to the Vanilla Overdrive:

http://www.tube-town.net/diy/lov/lov01-vanillaoverdrive-eng.html

I have been through this circuit too many times and i can't figure out what is wrong. The only website i can find with any build info is the tube town forums and the are all in German. Even with google translator they still don't help much... does anyone know how hard it is to comb through numerous pages of Germans arguing over off topics?
Maybe the answers are there... I'll keep digging... but in the meantime...
I'm beginning to believe that this circuit may not work as presented.
I already have too much time and money involved to just scrap it and start with something new... so I must press on.
The circuit has three "normal" gain stages feeding a cathode follower stage feeding a tone stack. I am having a problem where the signal comes out of the third stage and into the cathode follower. The signal seems fine all the way to V2-2. Then it falls off. I am using the prescribed 12at7 for V1 and a 12au7 for V2. I thought I might have had a bad tube until I swapped them one for the other (12au7 @ V1 and 12at7 @ V2) and get roughly the same result. All components were brand new, including the sockets and pots.
I get my signal through the circuit, but at a fraction of the voltage of the signal straight off the guitar. I have to crank my amp (Oatley K281) just to barley hear it. This amp works just fine with anything else feeding it. Straight guitar signal is much louder than when i put it through the pepper shredder.
I have an o-scope and have traced the signal through. I can see gains in the first two stages but then hit a wall going into the third, (same with tubes swapped one for another with very little signal difference on the scope). The tone stack seems to be functioning properly and not much signal is lost across it (compared to the drop at stage 3).
I did find that by jumping out R14 (to zero ohms) I can get a bit more volume, but nothing like what it is supposed to be. Tomorrow I will continue... cut loose the tone stack and check again...
Please do not respond by telling me where to place some solid state piece of crap or I will tell you where you can place itjavascript:void(0); This circuit is supposed to work without anything else besides the amp. And please don't question my soldering skills, I may be new to this forum but have been mil-spec certified since before the internet... Just sayin'javascript:void(0);
I'm sorry to anyone who feels I am being harsh. I am at my wits end with this and no one else seems to have the answers I'm looking for.
dorrisant

[frequencycentral]

I built the MkI a couple of years ago, using 6111 submini dual triodes, it works very well.



If you are getting issues after the third stage then it seems like the 4th stage or tonestack have some error(s). Check the value you used for R13, that's quite crucial, and also alllllll the values in the tonestack. Did you build this on Tubetown's PCB or point to point? It seems to me that the tonestack done point to point would be almost begging for wiring errors unless you're really paying attention. I'd disconnect the tonestack and get everything up to that point working first. Once you've done that, and are getting a good output from V2b, add the tonestack back in and see what you got.

[dorrisant]

Have you built this version? I am aware of your build from version 1... I don't see anything wrong with the way I have put mine together (according to the schematic). I am getting signal all the way through and have tried it with the tone stack completely disconnected and bypassed... Still signal is smaller out than in. I think some of the component values may be wrong in the schematic, not my build. I had several components to choose from for each position so I selected the closest value to what the schematic called for. Each component was hand selected to be accurate.
I guess I will not know how verified this circuit is until someone with MKII up and running.
Freq C, sorry if you have built this one and I am just not understanding you. Or maybe you would like to try this circuit since you have a good working knowledge of the low voltage kind of thing. I do appreciate your input so far, but I had already tried what you had suggested even before my first post with no success. I usually go through that type of troubleshooting procedure with everything that gets placed on my bench out of habit... I am a two way radio repair tech by trade.
I would also love to plot load lines for these two tubes (and many others) but the charts usually do not drop below 50 volts in most of the cases I've checked. I feel somewhat stranded or on an island... There would be a wealth of help and suggestions if we were using commonly seen voltages. That not being the case, I wait for some insight from those very few like you who have been successful with the low voltage ideas.
Many thanks to you and I hope that maybe I have further swayed you do dive into this project with me.
dorrisant
 

[CLAAS]

Hello dorrisant,
why did´nt you ask your Questions in the TubeTown-Forum??
(You have to be logged in).
There are alot of nice Guys to keep to help you.Specially the Owner,Dirk.
The "Unterforum" is called:"Tech-Talk TT-Projekte".
Feel free to ask in English!
Greets Thilo

[dorrisant]

Having trouble with that... German to Enlish...

[petemoore]

  See if the 4 stages are nearly the same in every way, start by using a stage that particularly passes audio [use audio probe to find a 'block-in-stage' where sound path is stopped].
  At that point in the circuit: choose node 1 of blockinstage and start counting:
  Number of connecitons, Value of each component to node one, polarity of components to node 1 etc., when complete, continue with Node two of the blockinstage.
  What is the supply voltage for 12au7 here ?
  At 12v the supply is probably on the verge of collapsing 12a_7 output signal, perhaps it doesn't work with any 'ol 12au7 even...there'd be starved potential for the tubes to start work with, as the grid needs to be - in relation to cathode by X voltage before anything can happen [X is subtracted from signal swing potential voltage] as far as gain or even passing signal.
  Have had limited luck with 9 and 12v tube plate supplies, but only after they became a 24v or 36vdc or more potential.