BLACK FOREST High Gain Preamp - Based on the Bogner Uberschall

[jymaze]

Did you ground the case of your gain pot?

I think it comes down to layout since we basically tried everything else possible...

Is it you on the picture?

[J0K3RX]

Did you ground the case of your gain pot? Tried that, did nothing except heat up my pot...

I think it comes down to layout since we basically tried everything else possible... This is possible

Is it you on the picture? It's Captian Morgan - http://www.captainmorgan.com/

[deadastronaut]

if I pick the pedal up and hold it up in the air with my head turned just a certain way and one foot slightly lifted the hum stops...

hmmm weird,.....i guess you've tried everything ....but have you tried it in another room?...some lights can really piss me off with noise!....fridge....dimmer switches....cat.....etc.

[J0K3RX]

if I pick the pedal up and hold it up in the air with my head turned just a certain way and one foot slightly lifted the hum stops...

hmmm weird,.....i guess you've tried everything ....but have you tried it in another room?...some lights can really piss me off with noise!....fridge....dimmer switches....cat.....etc.

Actually I did try a different room and with battery and adapter power still the f%$#ing hum...   Tried different guitars, swapped out all the fets, stood on my head, barked like a dog... the whole bit! HUMMMMMMMMM... The 18k resistor to ground on the input seemed to work the best and kills 100% of the hum and still retains about 90% of the gain and tone but still just killing that amount of the input tone coming from the guitar causes a substantial loss in my opinion... You really want to get the full tone and sustain of the guitar and preserve or enhance it, not pull it down... I think this preamp is just blazing wide open with gain like a screaming chainsaw with the J201 in the V1 spot. The guitar signal comes out of the first stage "balls out" and then hits those high gain mosfets and by the time it reaches the last one it's too much. I tried trim pots on the mosfets to get them tamed down a bit but it still didn't help. I think they are optimized the way they are set with the fixed resistors and any changes causes wild tone and gain loss..

I did audio probe this and most of the noise is on the 4th stage, slight noise on the 3rd and then substantial noise on the 4th... So, if the noise could be progressively reduced on each stage before the 4th stage it would probably get rid of the noise. How to do that? good question?

I have gone over this post since it's almost the same as the ENGL and no reports of this noise... But this guy hasn't posted in a long time or I am sure he would have jumped in by now.. Unfortunately his never made it off the bread board from what I can tell and he didn't make any layouts that I can find...?
http://www.diystompboxes.com/smfforum/index.php?topic=89399.0

What I lack in knowledge I make up for in persistence! I would rather work "smarter" vs. "harder" but that's what I got... If I didn't have to work for a living and I could attack this thing all day long every day I would have whooped it's @ss a long time ago! But, 2 or 3 hours every other night between 11:00PM and 2:00AM ain't cuttin it!

[J0K3RX]

Just looking at the AMT schematics and gut shots for the P1, B1, E1 and S1 noticed they all have 50k/A gain pots
On my "like E1" schematic I changed the gain pot to 100k just because it worked and that was the only close pot I had at the time, so I left it like that.

Not that these 2 preamps are alike but the first stages are very similar... And this E3 has sh!t tons more gain over all than the E1 does!  

[euronymous0001]

hmmmm...

how about a 100n cap between 9v and ground...

to quote MartyMart on post #18 http://www.diystompboxes.com/smfforum/index.php?topic=51863.0

"The extra 100nf filter is an RG tip, if I remember correctly - faster ESR helps to smooth the power faster than the
large 100uf, when used in conjunction with it. I use them often on higher gain circuits - then again, I could be talking absolute rubbish !!"

then again, I also, might be talking rubbish.   

[J0K3RX]

Ok folks, I believe I have FOUND THE PROBLEM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

My own stupidity mainly!

Ok, the shielded wire I thought was good enough, well, it wasn't "good enough"!

I pulled all the wiring out and rewired with "REAL" shielded wire (the kind with the F#^$ing tin foil wrapped around the inner wire) and whadaya know! No more HUM!!!!

Make sure you have it shielded right up to the board and only connect the ground braided wire on one side for best result! Shielding is most important on the input obviously but, I would "SHIELD EVERY F#%#ING THING" if you can! I tested it again and again to make sure I wasn't just imagining things and
NO F#%#ING HUM!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!  
So go to Smallbear and get some SHIELDED WIRE!!!!
http://www.smallbearelec.com/servlet/Detail?no=796

Edit: Oh, and same goes for the Black Forest!!!

[Somicide]

bout damn time, Jim

The suspense was killing me!

[deadastronaut]

WHOOOHOOOOO ....., so the debugging thread should now include waving it about in the air too

surprised you didn't have a bonus radio though...

good on ya man, i admire your persistence...but hey if you want ''that sound'' its worth sweating blood over imo....cool, hope your stress levels are getting back to sub normal...

[jymaze]

I guess it was somehow a layout problem then...

So did you shield the wires to the pots in the Black Forest? Or did you have a pot-on-board version (I lost track).

[J0K3RX]

So did you shield the wires to the pots in the Black Forest? Or did you have a pot-on-board version (I lost track).

Nope... All off-board pots on the Black Forest! Gotta watch that gain pot mainly, and never used shielded wires on it or the input! I have a new version of the Black Forest with all on board pots but haven't posted it, yet...

[euronymous0001]

kudos!

now, when can i have the time to make this 

[pakrat]

Good for you Jim! Now you can finally sleep 

[fretzburner]

Jim, you made me open again my Engl build hahaha thanks for the great discovery.Have to look for good shielded wires.

[J0K3RX]

Jim, you made me open again my Engl build hahaha thanks for the great discovery.Have to look for good shielded wires.

Fretz - SHIELD THE SH!T OUT OF IT!!! 

Well, "sometimes" the CD/DVD-ROM drives in your computer have an audio cable that runs to the sound card on the mother board and sometimes they are shielded really well but, sometimes they are not... Don't ask me how I know this Anyway, got lucky and found a really good one in an old Dell, big thick blue wire with the tin foil... Good stuff!!

I really need to break down and buy a spool of it so I don't have to keep "hit or miss" using these scrap wires... I guess if you are gonna be a serious high gainer this is like a golden rule not to be broken!

[J0K3RX]

Ok, What's next? New Black Forest, Krankenstein, Buzzefall (whatever the hell that is? but it sounds cool!), VHT, Modern Soldano 100, Mesa Triple Rectifier - jfet/mosfet version or what else? Requests?

Ok, I know... Slow down, right? It's just that all of the above schematics are almost the exact same except for values and some small differences so, I can use/modify the same layout!

[jymaze]

What about a Mk IV, a Dark Terror, a JVM 410, a Carvin Legacy, a Laney AOR? I am trying to go off the beaten path here.

[fretzburner]

Installed back the 2SK117 at V1 and still having noise issues even with shielded wires.Maybe my wires are not good enough(gutted from old TEAC 4 track recorder)or my layout because is too compact to fit 1590B enclosure.

[J0K3RX]

Installed back the 2SK117 at V1 and still having noise issues even with shielded wires.Maybe my wires are not good enough(gutted from old TEAC 4 track recorder)or my layout because is too compact to fit 1590B enclosure.

Do they have the tin foil around them?

[fretzburner]

No tin foil,i can't find it here in my location.i have one with tin foil but for mic cable very big in diameter and next to impossible to install.Jim did you replace your gain pot to 50k?I'm still using same as the schematic.