BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[pakrat]

I think any Schottky diode will work. Read page 39, there's some talk about it.

[J0K3RX]

Is it possible to exchange the BAT85 diode for something else?
Since I'm ordering at one shop, does any of these compare?
    1N5817    
      1N5822    
      BAT41     
      BAT42     
      BAT46     
      SB360     
      SB560

Thanks,!

What pakrat said...

I have used BAT41 and really like them.

[jymaze]

I tried the diodes and I got way less distortion! Did anyone else notice that drastic difference in perceived gain? No need to say I removed them instantly, it sounds just perfect without them anyway.

[J0K3RX]

I tried the diodes and I got way less distortion! Did anyone else notice that drastic difference in perceived gain? No need to say I removed them instantly, it sounds just perfect without them anyway.

Actually there is no need for these diodes in my opinion... They have little to no effect on my builds from what I can hear. I may hear a little difference when they are installed but that may just be my imagination... No gain loss that I can hear but I wouldn't be surprised if they did cause that in other builds given the wide variety of results that have been reported. Try BAV21 if you have any and tell me what you think? Just curious if you get what I am getting?

[Bliss]

Great thanks,
I think I'll order the BAT41 then, and just try if I like them or like it more without diodes. I'll check in with the results

[jymaze]

I tried 1n58, then normal silicon 1N4148. It just killed the gain in both cases. It was not on the Black Forest but on another jfet circuit with similar structure.

[miftah]

hi jim, I've build u'r  BF V.4 gain stage, and I like it very nice sound, this is video http://youtube.com/watch?client=mv-google&gl=ID&hl=en&v=4NPB78t5VZ4
Sorry for my bad playing..

[pakrat]

Sounds great, nice vid miftah!

[Bliss]

Hmmmm, I'd like to bother you with some more questions..

I fixed some problems, it gives a pretty neat sound at the moment, but not right. The boost still doesnt work. Also the sound fades away in a strange way. I've uploaded two clips, in one you can hear me play and then turn on the boost. In the other I play just one note and wait till it fades, sounds strange right? Also notice the lack of low tones (I'm playing a jazz guitar over a bass amp)
https://www.dropbox.com/s/cbdvx4ruh86lh2y/boost.amr
https://www.dropbox.com/s/7v1h7kwmzme1lxb/fade.amr

To give you an idea of the progress so far: one of the things that helped me get from no sound at all to this was to set the trimpots at 5,5V and double check the soldering. I also connected all the optional "Wide Switch" holed trough wires, did seem to help though I'm not sure. is it okay to connect them? (1 connected to 2 and 3 to 4) . Also the Volume potmeter problem is fixed, as stupid as we are we ordered the wrong pot....

I hope you can help us with this information to getting the sound 100% right.

Thanks again for the help so far!

[MyKeul]

Hi Guys,

I'm very intested in the Black Forest project but I can't find any J201, 2N5457 or 2N5458 where i'm used to order on the web.

I've posted my request 2 days ago and some of you answered me but yesterday, it was impossible to access the forum and this evening, i had the "surprise" to see that my account didn't exist any more (and my posts have disappear).

Could you please tell me again what FET to use instead of J201 (someone told me about JOK3RX's preference) ?

Another question : it seems that pots which are called "A" are LOG and "B" are LINEAR in the US while in Europe, "A" stands for LINEAR and "B" are LOG.
I'm lost in my choice; Should I use LOG or LINEAR for Volume, Gain, Bass, Mid, Treble ?

Thanx from France.

MyKeul.

[Jopn]

Hi Guys,

I'm very intested in the Black Forest project but I can't find any J201, 2N5457 or 2N5458 where i'm used to order on the web.

I've posted my request 2 days ago and some of you answered me but yesterday, it was impossible to access the forum and this evening, i had the "surprise" to see that my account didn't exist any more (and my posts have disappear).

Could you please tell me again what FET to use instead of J201 (someone told me about JOK3RX's preference) ?

Another question : it seems that pots which are called "A" are LOG and "B" are LINEAR in the US while in Europe, "A" stands for LINEAR and "B" are LOG.
I'm lost in my choice; Should I use LOG or LINEAR for Volume, Gain, Bass, Mid, Treble ?

Thanx from France.

MyKeul.

Hey MyKeul

The layout has the Log/Linear (ie. taper) letters beside the values found here: http://www.diystompboxes.com/smfforum/index.php?topic=98954.800
You're looking at linear for the gain and mid, and log for vol, bass, treble and voice.

J201s are fairly easy to come by, where do you usually order from?  Tayda and Furturlec both carry them, as well as most of the other "usual suspects".

[pakrat]

Could you please tell me again what FET to use instead of J201 (someone told me about JOK3RX's preference) ?

I think JOK3RX likes 2SK30A-R but they are far more rare here than J201.

[pakrat]

@Bliss  Which version did you build? I had that same decay/gate problem with my 5 stage build. I never got it working after that......

[Bliss]

@Bliss  Which version did you build? I had that same decay/gate problem with my 5 stage build. I never got it working after that......

I built the latest version (I guess) from page 41.

[Bliss]

@MyKeul,

I'm also ordering from Europe (The Netherlands) and had no problem with the Log/Lin.
I think Alpha prints the standard letters on the pots. Though I'm not 100% sure for france.

[J0K3RX]

In my opinion 5.5v is far too high... Try 4.7v or half of whatever voltage you are getting on the source power at that particular stage/jfet. The gate is made to be adjustable that is why there is a 1 meg pot there... you have to find the happy medium or "sweet spot" or you will get note decay and fizzling out sound. Honestly, I only use the gate maybe about 1/3 of the way up on full gain just to cut some of the inevitable high gain hum... If you get the jfet biased around the 4.7v range you can then fine tune them by ear, if you're good.

[MyKeul]

Thanx to all for your answers.

I'm used to order at mouser dot com and they don't have J201 (neither 2N5457 and 2N5458). I like this seler because they're very fast, not expensive and they sell lot of capacitors I really like in HI-FI amps.

I don't know tayda and furturlec; I'll have a look there.

[Maik]

Hey MyKeul, check out UK-Electronics. It´s in the neighbourhood, so it will be fast.
http://uk-electronic.de/onlineshop/product_info.php?products_id=247&osCsid=4ebdb042e640b54c178ff440b3d2d806
J201 for 0,48€

[J0K3RX]

I'm used to order at mouser dot com and they don't have J201 (neither 2N5457 and 2N5458). I like this seler because they're very fast, not expensive and they sell lot of capacitors I really like in HI-FI amps.

Sure they do!
http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/MMBFJ201/?qs=%2fha2pyFadujHCFJwZJmrE7odvBpdRsrrdQ15sn4Bm54%3d

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/MMBF5457/?qs=%2fha2pyFadugLayO0YJePXoBgS3AKmKkcvO%252b1%2fj%2f9%2fiU%3d

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/MMBF5458/?qs=%2fha2pyFaduiQPyCWdWaokQt0OVpBllzsUlcwGhkguWo%3d

We are all gonna have to come to terms with SMD/SMT sooner or later... might as well get on with it!

I have been using the surface mount J201's and 2N7000's for quite a while now and call me nuts but I think they are better!

[ggedamed]

In my opinion 5.5v is far too high... Try 4.7v or half of whatever voltage you are getting on the source power at that particular stage/jfet. The gate is made to be adjustable that is why there is a 1 meg pot there... you have to find the happy medium or "sweet spot" or you will get note decay and fizzling out sound. Honestly, I only use the gate maybe about 1/3 of the way up on full gain just to cut some of the inevitable high gain hum... If you get the jfet biased around the 4.7v range you can then fine tune them by ear, if you're good. icon_wink

I proposed 5.5V as a starting point. Considering a J201 that has Vp = -1V (most of mine have VP around -0.8..-0.9V), the available headroom is at 9 - 1 = 8V, and the middle point is 8/2 + 1 = 5V.
Oops, don't know what was I thinking when I wrote 5.5V. I guess I tried too hard to be smart  .
Your value of 4.7V suits best a transistor with Vp = -0.4V, mine suits best a transistor with Vp = -2V, when they're supplied with 9V. They both work, even if the drain is not at the half-headroom point. In my circuits the trimmers get always replaced with resistors.

So it seems that the easiest way to bias a J201 is to set the drain voltage to half-voltage and then to adjust it a little bit upwards by ear. Of course, one may like it better when biased off-center.