BLACK FOREST - Based on the Bogner Uberschall

J0K3RX · Post by **J0K3RX** » 27 Oct 2012, 04:59

Ok bigrigg, if yer still around and not totally pissed off I have a fix for ya!! First remove all the mods and put them back to the original values... Then replace R15 and R16 both with 1.8k resistors. You can probably use 2.2k also but I used 1.8k so I know they work. Then remove R2 and replace with jumper and put a 470pF cap across R1. Replace C2 with a 220nF or 470nF cap. For the boost resistors (R22 and R5) I use 10k and 18k. If you replaced C22 with a 220uF cap you can leave that in there, it's fine... If you have 100uF that's fine, I don't notice any real difference between the two... Also, I removed the presence knob because it was causing weird problems with the tone stack mainly in the treble pot. Has plenty of presence anyway. The two main changes are R15 and R16 to 1.8k, all the rest is just fine tuned stuff... Bias all of the transistors at half the voltage, mine are 4.3v for Q1, Q2 and Q3 then 4.5v for Q4 and Q5. That's it, you shouldn't have any hum with the volume rolled all the way down on your guitar and just the expected noise you get with high gain when the volume is turned up.. And btw, I have the noise gate working perfectly which removes almost all of the normal high gain noise without killing the sound, but if you have a Decimator then I see no need for that!

jymaze · Post by **jymaze** » 27 Oct 2012, 14:09

That was R15 and R16 as I expected... Glad it worked. By the way Biggrig already sized up R15 and R16 I think.

My other mods (beside R2 and the power supply mods) are supposed to give you more gain and a little less "wasted noise" in between stages. They were not that bad in theory. The trade-off is more top end, that may have to be filtered out at the output if needed with 2 consecutive low pass filters (14.7k and 2.2n). Overall, if it is quiet enough as-is it makes sense to just keep the "waste" between stages anyway.

I would still try to suppress R10 which is wasting 6 dB of noise for no specific reason, and you will have 6 dB of noise-free gain on the top of you already crazy gain.

In conclusion, I really have to get that thing a try someday.

bigrigg · Post by **bigrigg** » 27 Oct 2012, 14:51

oh you devils......ok you probably have suckered me in, but could I ask one simple request?
At this point, there have been so many mods, suggestions etc I seriously don't know what the hell values are what anymore. LOL Can we list the new, updated and fingers crossed BOM for component values? Then I will go through, double check, swap or remove and replace where necessary and report the uber gain awesomeness when I can. Sound cool? (pun intended) Let me know thanks.

J0K3RX · Post by **J0K3RX** » 27 Oct 2012, 21:11

ok, there is a guy (pakrat) in another forum that has built this also. He also encountered the same hum/noise... He had the original values that I listed on the last layout that I made and the only things he changed were R15 and R16 to 1.8k. He verified it working 100% and said it was dead silent even without the noise gate mod. So, I have verified it working and pakrat has verified it working also.. At this point I don't really want to throw out a new "Rev" until more people verify it working or not.

On another note:
I also have very little spare time. I work 60+ hours a week and have 4 kids one of which is disabled so I can fully relate with anybody who says they are hard pressed for spare time! I started this thinking it would be a "piece of cake" and now I can really appreciate all that goes into making these pedals! For the most part I have done this entire project between the hours of 11:00 PM and 3:00 AM give or take a few hours here and there... I started this post on Sept. 1st and I am sure that by now I have at the very least spent a total of 25 days, 4 hours at a time on this so do the math!

So, the fix for the low level hum/noise going from my build and one other persons build is the replacement of R15 and R16 with 1.8k resistors. Any other changes are up to you and may or may not improve the sound.

BTW - I tested this today back to back against an AMT P1 pedal through a TubeWorks MosValve power amp and running direct with myself and two other guitar players and it was unanimous that we all agreed the BF stomped the living sh!t outa the P1! All I have to say is WOW and good luck!!!

Aharon · Post by **Aharon** » 27 Oct 2012, 23:48

A great big thanks man!
Aharon

J0K3RX · Post by **J0K3RX** » 28 Oct 2012, 02:34

The only difference in this layout is the added jumper above R19 which can be removed along with R19 for attaching the optional noise gate and the addition of C25 - 470pF cap by R1 which if you have already etched the board you can easily solder on the back solder side of the board. You also may consider removing R10 as jymaze pointed out for added reduction in noise but I have not tried it yet...

I am pretty much done with this now and on to the ENGL... BIG THANKS goes to jymaze, mensur, bigrigg and pakrat for all your help!!! And if I forgot anybody thank you as well...!

Post by **The G** » 28 Oct 2012, 11:41

Nice work!

Please, don't forget about my dry sample.

jymaze · Post by **jymaze** » 28 Oct 2012, 14:27

Jok3rx,

You are welcome man!

PS: Where is this Diezel schematic?

J0K3RX · Post by **J0K3RX** » 28 Oct 2012, 17:54

jymaze wrote:Jok3rx,

You are welcome man!

PS: Where is this Diezel schematic?

Not sure how accurate? Missing tone stack..

I love the tone of the Herbert!

jymaze · Post by **jymaze** » 28 Oct 2012, 21:32

Thanks for the schematic,

Some work ahead of us.

I wonder they chose the values for the tonestack of the Diefet, maybe they are accurate. It would be a good start.

J0K3RX · Post by **J0K3RX** » 29 Oct 2012, 00:27

jymaze wrote:Thanks for the schematic,

Some work ahead of us.

I wonder they chose the values for the tonestack of the Diefet, maybe they are accurate. It would be a good start.

Work indeed, but fun...

Yeah, I was thinking the same thing about the tonestack myself..

bigrigg · Post by **bigrigg** » 29 Oct 2012, 02:10

OK guys, I'm partially done swapping etc to get to the latest and hopefully final BF version. I will build without the noise gate to start. I will let you all know when I'm finished. Thanks and good luck with the ENGL.

One more question for JOK3RX.....are you using this BF as a real pre amp just ahead of the power amp or are you using it as a standard pedal and running into the front of the amp?
thanks

J0K3RX · Post by **J0K3RX** » 29 Oct 2012, 05:51

bigrigg wrote:OK guys, I'm partially done swapping etc to get to the latest and hopefully final BF version. I will build without the noise gate to start. I will let you all know when I'm finished. Thanks and good luck with the ENGL.

One more question for JOK3RX.....are you using this BF as a real pre amp just ahead of the power amp or are you using it as a standard pedal and running into the front of the amp?
thanks

I have tried it in front of an amp going into the input like a distortion pedal and I personally don't like it that way. I don't like my Dr.Boogey that way either. If I am going to run through the front input of an amp I will use something like a Riot pedal or a CruchBox or some variant... I have tried it into my MosValve power amp and into the fx-return of my brothers 5150 using just the power tubes and I like it that way! For recording samples and whatever I like to go direct and use impulses...

J0K3RX · Post by **J0K3RX** » 31 Oct 2012, 16:29

Ok, I guess that didn't work?

bigrigg · Post by **bigrigg** » 31 Oct 2012, 19:01

IF you are referring to my attempts?....
I think I got it all swapped late last night. First fire up, massive gain yes. Massive noise, yes. I need more time now to double check, tweak and try a few things. Didn't want to post it was a "failure" too soon if you know what I mean. Tonight is Halloween family time etc so I'm boned for time. I will try to update asap. I have faith!! lol

meffcio · Post by **meffcio** » 29 Nov 2012, 17:50

Anyone with the latest schematic? Also, I was wondering if I could achieve clean sounds if I omit some gain stages with a switch? I'd like to make a simple bedroom head with 2 channels, one eq, and ~15W output power.

J0K3RX · Post by **J0K3RX** » 29 Nov 2012, 18:23

meffcio wrote:Anyone with the latest schematic? Also, I was wondering if I could achieve clean sounds if I omit some gain stages with a switch? I'd like to make a simple bedroom head with 2 channels, one eq, and ~15W output power.

I have the latest schematic and I have gone back to the roots of this project... I have removed all attempts to create "more gain" for example the added gain stage I have removed. I find that it is better to run a tube screamer or some OD pedal in front of the preamp to get more gain and tighten up the low end rather than to try to add gain stages... I takes away from the tone in my opinion and opens up a whole can of worms with hum and noise problems... Yes, you could bypass stages to have a clean or crunch channel/channels... I will try to upload the schematic tonight when I get home from work...

grrrunge · Post by **grrrunge** » 29 Nov 2012, 18:32

J0K3RX wrote:I will try to upload the schematic tonight when I get home from work...

That would be much appreciated amigo!

jymaze · Post by **jymaze** » 30 Nov 2012, 03:06

As we have seen during the development of the BlackForest, sometimes too much gain can create more problems than needed.

Personally, I think 4 jfet stages are plenty: at full gain, it is already getting pretty crazy. Imagine a stage with a gain of 20 (realistic for a jfet stage ), so 4 stages give a gain of 20x20x20x20=160.000 (104dB)!!! It is huge!!

To the point of being too much actually.

I was also thinking of something like an opamp stage (not far from a screamer) into 2 jfet stages. I will work on that. It should be fun: Plenty of gain with the flexibility and quietness of an opamp input stage.

fretzburner · Post by **fretzburner** » 01 Dec 2012, 10:42

jymaze wrote:As we have seen during the development of the BlackForest, sometimes too much gain can create more problems than needed.

Personally, I think 4 jfet stages are plenty: at full gain, it is already getting pretty crazy. Imagine a stage with a gain of 20 (realistic for a jfet stage ), so 4 stages give a gain of 20x20x20x20=160.000 (104dB)!!! It is huge!! To the point of being too much actually.

I was also thinking of something like an opamp stage (not far from a screamer) into 2 jfet stages. I will work on that. It should be fun: Plenty of gain with the flexibility and quietness of an opamp input stage.

Something like brunetti mercury box opamp input and followed by 3 fets?