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I thought I would give this a try and I am damn glad I did! I used the original Uberschall tube amp schematics that I found by accident while looking for something else... This thing is a beast, butt loads of high gain!!
I made a few changes here and there but for the most part it's true to the schematic. I removed a resistor (470k) going to the volume pot because the volume was a little too low. I added a gain/saturation boost switch and of course the diodes between source and gate on Q2, Q3 and Q4 and that's about it. You may want to experiment with different value pots in the tone stack.. I went so far as to use the same values used on the Dr. Boogie and I may leave it like that, still trying to get it just right... When converting these high gain preamps over to JFET it seems like the tone stack does not make the transition as well as it should. Probably because of the lower voltages? Anyway, the Dr. Boogie values or close variants seem to work pretty well.
And no, I did not create a schematic... If you want the actual amp schematic PM me and I will send it to you.
Biochemist wrote:Nice work! Thanks for sharing this... can't wait to try it out.
Yes, first post and I do appreciate all that I'm learning from all of you guys...gracias!
Thanks man! Just trying to give back a little... I have learned a lot here also! This pedal is still kinda buggy in the tone stack but I have confidence that we will get that ironed out shortly. Even with the funky tone stack you can still dial in a brutal high gain sound that really sounds like the Uberschall!
Very nice, please keep us posted on the improvements you do on your way.
I don't like being a lurker who gives nothing back but for now that's the role that's pretty much imposed on me by my limited skills (I can build pretty much anything as long as guys like you do the dirty work for me). However, I'm a fast learner and definitely not the ungrateful kind so it'll all balance out in the end...
Biochemist wrote:Very nice, please keep us posted on the improvements you do on your way.
I don't like being a lurker who gives nothing back but for now that's the role that's pretty much imposed on me by my limited skills (I can build pretty much anything as long as guys like you do the dirty work for me). However, I'm a fast learner and definitely not the ungrateful kind so it'll all balance out in the end...
Thanks again!
Believe it or not, if you build it you will be giving back! So, get to work and don't be a stranger!
I cannot think well on a layout, so here it is the schematic, hopefully error-free:
black_forest_v1.png
Me likes the switch on the tone stack, it's a clever idea.
Looks like C4 and C5 are in series.That gives around 2nF. I'm quite sure 2nF it's a little too low (making it a little too high pass filter ). Is it a slip or is it intentionally?
Also I'm quite sure that, given the capacitors tolerance, one cannot feel any diference between 22nF and 24.2nF, as in C11+C12. I know that audio-heads (the Hi-Fi kind) are using smaller capacitors in parallel to electrolytic capacitors. Are we talking about something similar here?
ggedamed wrote:I cannot think well on a layout, so here it is the schematic, hopefully error-free:
The attachment black_forest_v1.png is no longer available
Me likes the switch on the tone stack, it's a clever idea.
Looks like C4 and C5 are in series.That gives around 2nF. I'm quite sure 2nF it's a little too low (making it a little too high pass filter ). Is it a slip or is it intentionally?
Also I'm quite sure that, given the capacitors tolerance, one cannot feel any diference between 22nF and 24.2nF, as in C11+C12. I know that audio-heads (the Hi-Fi kind) are using smaller capacitors in parallel to electrolytic capacitors. Are we talking about something similar here?
That's pretty good.. Since you pointed that out I found a mistake on my diagram C4 should be 100nF instead of 22nF. I believe that C4 can be left out and jumpered.
Here is the schematic that I am working from... Should help!
Ok, this is what mensur another forum member sent me in a PM.
"Change source resistor on the buffer with 33K-47K-56K and see what will happen, the buffer cannot track cut-offed signal well and so tone stack becomes buggy."
So, I tried it and it made a BIG difference! Instead of the values he mentioned I tried 10k (Like the Dr.Boogie) and I am fairly happy with it... I may need to try his suggested values as well just to get it dialed in or maybe I will stick a 100k trim pot on there and adjust until I get just the right value
In short: What I did was I changed R16 from 100k to 10k... All the pots are stock value from my diagram.
meffcio wrote:What software did you use? You could attach the whole file, not only the schematic image
I'm using Eagle CAD.
I only made the schematic, so I thought the image is good enough. Anyway, I don't have time to modify it right now, so here it is:
I'd love to... waiting for some parts right now! Many projects at once but this one is on the list...
J0K3RX wrote:
Biochemist wrote:Very nice, please keep us posted on the improvements you do on your way.
I don't like being a lurker who gives nothing back but for now that's the role that's pretty much imposed on me by my limited skills (I can build pretty much anything as long as guys like you do the dirty work for me). However, I'm a fast learner and definitely not the ungrateful kind so it'll all balance out in the end...
Thanks again!
Believe it or not, if you build it you will be giving back! So, get to work and don't be a stranger!
meffcio wrote:What software did you use? You could attach the whole file, not only the schematic image
I'm using Eagle CAD.
I only made the schematic, so I thought the image is good enough. Anyway, I don't have time to modify it right now, so here it is:
black_forest_v1.sch
Nah, it was noble of you to upload the image, but.. why force other users of Eagle CAD to drawing the same thing from scratch? That's why I asked for the file. Thanks!
Ok, here's an idea I use a TS808 in front of everything, preamps, amps etc.. Just gives it that extra "kunk" sound and feel for lack of a better word. It also drives the notes when doing leads etc.. I know many players that use them like this. Even though the preamp has plenty of gain the tubescreamer just seems to add the cherry on top of the sunday! I mainly use it as a clean boost where the level is almost all the way up and the drive is all the way down. So, what I was thinking is maybe add a Mosfet/Jfet boost circuit foot switchable in front of this preamp like on the Wampler Triple Wreck? Not many parts involved and I could get rid of the Presence knob and put a switchable low pass or no switch to accommodate the additional boost knob/pot Thoughts?
I'd also be very curious of just mounting this one with a SHO circuit in front in a larger enclosure... two switches and everything: great boost in series with this one, would be pretty cool (maybe)...
I'd also be very curious of just mounting this one with a SHO circuit in front in a larger enclosure... two switches and everything: great boost in series with this one, would be pretty cool (maybe)...
Yeah that is one of the top choices on my list... may throw one together or bread board tonight and give it a try Never played one so it will be interesting! Silly low parts count
Exactly, very low parts count = small size pcb or veroboard, ideal for inclusion in any twin-pedal setting. It's by far my favorite booster.
J0K3RX wrote:
Biochemist wrote:Good idea me thinks.
I'd also be very curious of just mounting this one with a SHO circuit in front in a larger enclosure... two switches and everything: great boost in series with this one, would be pretty cool (maybe)...
Yeah that is one of the top choices on my list... may throw one together or bread board tonight and give it a try Never played one so it will be interesting! Silly low parts count
On your schematic, the tone stack should be connected to the source, not the drain (talking about Q5 of course). Probably it would help some people to have some transparency for the components on the layout since it takes a little knowledge to guess some of the connections that are obscured by components above them. The source of Q5 being a prime example.
Thanks again Jok3rk for that circuit, I still have to build one of these. I was thinking about socketing most of the components so I could switch between a B1, a S1, a Dr Boogie, etc...
J0K3RX wrote:I thought I would give this a try and I am damn glad I did! I used the original Uberschall tube amp schematics that I found by accident while looking for something else... This thing is a beast, butt loads of high gain!!
I made a few changes here and there but for the most part it's true to the schematic. I removed a resistor (470k) going to the volume pot because the volume was a little too low. I added a gain/saturation boost switch and of course the diodes between source and gate on Q2, Q3 and Q4 and that's about it. You may want to experiment with different value pots in the tone stack.. I went so far as to use the same values used on the Dr. Boogie and I may leave it like that, still trying to get it just right... When converting these high gain preamps over to JFET it seems like the tone stack does not make the transition as well as it should. Probably because of the lower voltages? Anyway, the Dr. Boogie values or close variants seem to work pretty well.
And no, I did not create a schematic... If you want the actual amp schematic PM me and I will send it to you.
tone stack could be changed by a simple formula and modify
according to your needs see this article http://www.aikenamps.com/ToneControlScaling.html
some guys scaled down the tone stack to make it functional with other values.
When converting these high gain preamps over to JFET it seems like the tone stack does not make the transition as well as it should. Probably because of the lower voltages? Anyway, the Dr. Boogie values or close variants seem to work pretty well.
So, get to work and don't be a stranger! 
). Is it a slip or is it intentionally?
or maybe I will stick a 100k trim pot on there and adjust until I get just the right value 
Never played one so it will be interesting! Silly low parts count 
