HELP with "microphonic" input wire on BSIAB2

[analog kid]

 I know there's a ton of stuff on the forum about the BSIAB and 2  problems with ocsillation and just hi gain noise (which btw is the only noise issue I am having with mine , just alot of RF pickup close to amp with pedal and guitar.. even with a shielded lace sensor equipped strat) BUT nothing that I've found that address this problem:
While checking wiring layout etc.. to see if I could minimize the "noise/hum" at high gains any at all, I noticed that one wire was microphonic to the touch!!(pecking it with my fingernail,etc..)
Tracing the wire to the pcb a etched , it was theeffect INPUT to switch lead. The wire that is curiously placed directly next to the Drive pot lug 3 wire.  So I tried repacing the wire itself 3 times once with a shielded conductor w/ shield grounded.  No change.  and I can't help but think this isn't normal , and could very likely be culprit to at least some extra RF interference.  (?)
Can anyone help explain this or help me remedy this problem?
JFET prob??Q1?   oh and only thing I can think of that I skimped on is that I used a 500kA pot from on old "paul" style guitar.
        thanks alot for any help!!

[Paul Perry (Frostwave)]

It's like going to the dentist, you have to be sure that the one you are tapping is really the problem. Could the vibration be coupleing to the old pot??  pots are notoriously vibration sensitive. And maybe the tracks the wire goes to need to have solder relaid on them just in case.

[powerplayj]

It's like going to the dentist, you have to be sure that the one you are tapping is really the problem. Could the vibration be coupleing to the old pot??  pots are notoriously vibration sensitive. And maybe the tracks the wire goes to need to have solder relaid on them just in case.

Nah, I think analog kid might be on to something.  My leads going from input jack to switch and switch to board seem to have the same microphonics issue.  Although I think there might be a relation to the gain pot as well because the noise definitely gets worse when the gain is dimed.  I have tried using extra insulation around these wires and moving them away from each other but that doesn't seem to help.  I have also trid resoldering the jack, switch and gain pot but to no avail.  Don't get me wrong, this is my favorite build by far but if I could hash out the hum/noise issue, it would be a perfect build for me.

Is Ed G. or Jack O. around these days?  I'd be curious to hear if they ever encountered this issue.


For what it's worth, I used all 2N5457's in my build.  I also have a well-shielded Strat with Lace Hot Golds (w/ humbucker bridge)

[Paul Perry (Frostwave)]

Well, some wire IS very microphonic, the worst I ever had was some phone cable designed for underfloor work, with a deep blue plastic cover. But you can easily see if it IS the wire, by using wire from another source!

[analog kid]

 

I have also trid resoldering the jack, switch and gain pot but to no avail.  Don't get me wrong, this is my favorite build by far but if I could hash out the hum/noise issue, it would be a perfect
build for me.

Thanks! That's what I wanted to hear ( In a way) I did most of the same stuff trying to remedy it to no avail as well. It really must just be part of the circuit. I did email Ed G about it to get the main man's opinion on it. I'm glad to hear it's not just mine that does this or that has a good amount of hum when gain is 1/2 way up or so.  I tapped around on the crkt pads , which you'll always get noise from but not usually that kind of microphonic pop, and it seems there was the same thing on the Drain of Q2 I believe so I swapped that FET just to be sure. Must be normal?!

Well, some wire IS very microphonic, the worst I ever had was some phone cable designed for underfloor work, with a deep blue plastic cover. But you can easily see if it IS the wire, by using wire from another source!

Well as I said in my post, I DID suspect the actual wire and tried 3 different types (22g stranded , S.Bear 24g pretinned stranded, and shielded 2conductor stranded wire) No Dice!  Maybe a few people should pop open their BSIAB's and tap on the input wire , I'd bet most every one of them do it!
   Also by the by , I have been on the hunt for a way to quiet that slightly excessive hum/RF pickup and came across a very interesting post by RG that stated the way "we" usually mount our crkts (2 metal bushing jacks directly mounted to box ) actually grounds the circuit in two places , which he says doesn't always cause any problems and can usually be gotten away with BUT can usually give lots of trouble with .. get this..." especially with high gain JFET and MOSFET distortion devices where the circuit has high gain right up into the VHF radio band."    Yeah that's a BSIAB2 alright!
So this may be key in solving SOME of the high gain noise. I sure hope so cause like powerplay was saying and I agree.. if it weren't for just that , this would very possibly be the perfect all around distortion in my opinion

[dr]

...I had a microphonic input cap do this same thing to one of my builds-I tried another cap and it took care of the problem....(don't know if this helps you or not)

[analog kid]

Now I should say that I thought it strange that the input wire there is microphonic but NOT the input cap(s), the only cap I hear a microphonic pop on I think is the .068  And also that I DO have a polystyrene 220pf in there rather than the 250pf Ceramic as noted. (surely no problem?)  I did also use a multi-layered 150pf cap in place of the 150pf ceramic and when I changed it out for the ceramic I could swear the noise factor went down. So maybe I should change that polystyrene to ceramic (and the exact value!, hard to find a 250pf )
the 470pf cap does say styrene or ceramic and i went w/ styrene there too. I love those things in wah pedals and usually for input caps. they just impart a clarity I think not unike the difference with Mica, but I don't know much about materials.
ideas

[analog kid]

OHHH MAN!!! I am Friggin JAZZED HERE!   
Who cares about the input wire!? I just got a batch of free samples with some 25packs of FETS (5457, 5458 , and MPF102s  no J201's but who's complaining?) so thought I'd get back the Brown sound to see what improvements I could get ... well I also tried the 'single path' ground idea....well........
DO IT!!! what I suggested in my earlier post to your BSIAB if you have a real problem with noise. I swear It made all the difference in the world. I 'm going to start making sure all my med/high gain effect are only grounded one way.  I haven't A/B 'd it from insulated/non on the output jack but I don't need to ... This thing was a hum machine when I got the volume up even with bypass and amp vol up decent level with even 50% gain , NOW I have the strat leaning against a chair BSIAB STILL on with GAIN at 90%  and there's just a light hum coming from it.  And at around 50% gain sitting right next to the amp wth the box open and upside down right beside me it's almost dead quiet~!
Ol' RG leave it to him to awaken me to something that simple.  Here's the thread I found the idea in:
http://www.diystompboxes.com/smfforum/index.php?topic=3474.0

[powerplayj]

So, did you use a nylon bushing with one of the jacks or did you try another method?  Also,does your pedal have a battery connector as well?  I opted not to use one so, I am wandering if I did anything strange when I took off the battery snap.

[Paul Perry (Frostwave)]

If you have used three different types of wire, and you still get microphonics, it isn't the wire.

[wampcat1]

call me crazy, but if that doesn't work try connecting a 1m resistor at the point between c4 and r6/c5, and the other end where c12 and r14 are connected. Should work much better.

Take care,
Brian

[powerplayj]

call me crazy, but if that doesn't work try connecting a 1m resistor at the point between c4 and r6/c5, and the other end where c12 and r14 are connected. Should work much better.

Take care,
Brian

I'll try that tomorrow as well.  ....just played with the trim pot and although the tone sounds a bit more full at a certain spot, I have the associated hum as well.  Just on the edge of the sweet spot without being too gated the noise seems to be reduced.  Maybe my problem has more to do with Q5 rather than the drive pot itself. 

[analog kid]

 Quote by Paul Ferry : "If you have used three different types of wire, and you still get microphonics, it isn't the wire."
Yeah I said I ruled out a wire problem BY trying different types. I am definitely not concerned at all with the "Live" wire prob now as since I've quieted this beast damn close to a whisper of background noise with Gain pot anywhere below 80% (90to 100 of course still brings on some Stray pick up) and also the fact that for the most part this thing is behaving normally everywhere else.. however I AM very interested in understanding it!  And I haven't heard from anyone else on it but I still am very much wondering if this is just a behavior of the bsiab that everyone may have if they checked it. (?)
Onto the mods and FET selection of the box though....
I do have issues /questions:
I have heard so many say they like all 5457's,  so HOW IN THE HECK do you guys get all '57s to work in there ?? I take it that they SHOULD? Because no matter how many I try out there, Q4 just will NOT function with a 5457 in there!! Only a J201 so far will work> The circuit immediately goes splatty and misbiased.   Is this  not something that anyone else has run into?!!
And also  I'm sure this is standard but there is a MAJOR difference in the Q1 position  switching between J201 (crunchier louder  gainier and a bit more noisy ) and a 5457 ( less volume little less available gain ,rounder and definitely LESS NOISE!!  A worthy tradeoff?  Do others have this effect with Q1???
  In my mind THIS seems to be a perfect place to add in a diversity mod if one could find a way , probably via a little daughter board with a tranny socket and using a switch to let you go back and forth between the two Fets' characteristics WITHOUT having to open up and re-socket one. noone likes to have to do that with a gigging pedal (SPDT,DPDT,or 3PDT for this idea? I'm not good with switches..being 3legs on a tranny would you have to use a 3P toggle to do it ??I have some!) 
Anyone's experience with these??

[powerplayj]

The difference I notice between two J201's and all 2N5457's is more on the clean side of the gain pot.  All 2N5457's seem to keep it a bit cleaner while I think the difference between JFETs at higher gain is somewhat negligible.  I didn't notice if I had to rebias when changing out JFETs but I would readjust regardless.

[analog kid]

I didn't notice if I had to rebias when changing out JFETs but I would readjust regardless.

Also I didn't notice major differences in gain other than slight tonal change between the two (though I'll check the "cleaning up " factor you mentioned) except as I said with the difference swapping for Q1 ONLY. There is definitely an overall boost and more drive with all J201's in there which I like but unfortunately it does add to what noise IS present. And my BIGGEST PROBLEM( which makes me wonder if I may have a problem somewhere )IS that I AM NOT ABLE to use all 5457's to hear what that would sound like!! As i said the Q3 position (not Q4 as I said before ) just will not allow me to put a 5457/8 in there. Just goes completely splatty. I guess I should check resistor values around that stage but the thing sounds sooo good when a J201 IS there. Can anyone tell me if this means I've got a problem. ?? Lots of you say you like all 5457's so I know I should be able to use them.
thanks I hope this thread isn't dead , I don't want to have to post this question as a new thread if I can't figure it out.