Chunk 2012 noise

[toolguy]

I now have my Chunk Chunk boxed up and "on the road" with me.
I went to use it at practice Sunday (above bedroom levels for the 1st time) and
it's much too noisy at idle. It has so much white noise and a bit of random crackle that it
won't let my noise gate turn on (bumps the threshold). This is also present with the guitar volume
all the way down...so it's coming from the pedal.
This is with volume and gan about 12:00. Loweing the  gain helps a "bit", but
it's still a problem.
It's in a metal enclosure and I am not using shielded cable (runs are very short to the switch though).

Anything I can look at/try?
Thanks.

[madbean]

Random crackle sounds like a spotty transistor to me. Really, you would need an audio probe to track down the source of noise, but a tweaking of the bias pots internally might help.

[toolguy]

Good deal.
I have a bag of 201's I can toss at it.

Should I check q5?
It does not need bias set...so my meter has yet to touch it.
Should there be a range that it needs to be at for proper operation?

[toolguy]

Went through about 20 j201's lastnight. Was still pretty noisy.
Put some shielded on the output from the board and input to the jack and it helped a bit but
its' still cracking some. Went through the vr's and cant find any bad ones.
Looks like without building a probe..I will just need to deal with it for a bit.

One thing I tried was loading up some 2n5457's. DEAD quiet...but gain is about halved and you
loose all the bottom thump (thud or chug?). So...I was thinking I might build a 2n5457 Chunk and
mess around with the caps to try and bring back the low end. I think it can make a great
"rock" pedal if I can get this figured out.

Question...What cap/resistor do I mess with to fatten the bottom end (c16?).
thanks

[marauder]

Try j201s for q1-2 biased at around 5.5-5.6v, and 2n5457 for the others biased around 6.1-6.2v.

Change C16 to 10nf.

Less gain than with all j201s, but retains the low end, and chugs better than all 2n5457.

Read the fetzer valve article on runoffgroove, you'll realise the standard 1/2 supply voltage biasing is not ideal, and different jfets have different requirements.  Make a jfet matcher, it will help get the bias accurate for each jfet, they are incredibly variable.

[toolguy]

Try j201s for q1-2 biased at around 5.5-5.6v, and 2n5457 for the others biased around 6.1-6.2v.

Change C16 to 10nf.

Less gain than with all j201s, but retains the low end, and chugs better than all 2n5457.

Read the fetzer valve article on runoffgroove, you'll realise the standard 1/2 supply voltage biasing is not ideal, and different jfets have different requirements.  Make a jfet matcher, it will help get the bias accurate for each jfet, they are incredibly variable.

Good stuff.
Thanks. 

[madbean]

You can also replace just Q1 with a 2n5457 and leave the other as J201. I did this on my very first Boogie build way back and it helped a lot with noise.