Cornish Buffer/G2&SS2 clones signal bleed/noise when bypassed.

[Bandwagonesque]

Hi everyone. I've built a couple of pete cornish clones based off their tagboardeffects vero layouts. I built both the G2 and SS2 with their accompanying cornish buffers ahead of each of their circuits and have them wired up per the direction of the tagboard wiring diagrams they provided.

Now both of them work and sound fantastic and definitely do as advertised, but both suffer from the same rather frustrating issue. When both are off and bypassed, there is a signal bleed that is audible, like a very very faint distortion. Also, when I turn up all the controls, I can hear them take effect on the background hum. Now I remember a long time ago, wiring up a cornish buffer on its lonesome and dont ever remember encountering these issues, but theres definitely something amiss now with the buffer working ahead of the circuit.

Here are some gut shots of each of my builds. I actually had the same enclosures lying around that pete used, so decided to try and wire them up as cornish-esque as possible. I'm not sure if theres a mileage issue in regards to the leads, but maybe that could be an issue? I followed the layouts for the buffers as close as possible, using a bc249C instead of the regular bc249 as instructed, and using a 5401 for the diode. other than that, I haven't substituted anything else. Could the wiring diagram made by tagboard be incorrect? I wouldn't be surprised as theres actually an error in the layout provided below on the main circuit so anything could happen i suppose.

Has anyone ever dealt with this issue with the cornish buffer or any cornish clones using the buffer? I feel like the only one whos had this issue after trawling this forum and elsewhere for a solution so anything helps in getting things normal when its bypassed.

[patrick398]

I don't know any of these circuits particularly well but seem to remember seeing a few gutshots of pete cornish pedals. Doesn't he use shielded input and output cables? Is the drive section very high gain? I wonder if he uses shielded cable to avoid the high gain part bleeding into the bypass signal?
Does the bleed through change if you move wires around?

[r080]

Do you have pictures of the SS2 as well? I remember your thread on the G2 from February. I was wondering about moving wires as well. Pete Cornish does indeed use shielded cable on the insides of his builds. It would be interesting if the reason is simply that he would have signal bleed issues otherwise.

I have built a G2 and an SS3, both with buffered bypass, though on manufactured circuit boards, and have not had any signal bleed issues.

[garcho]

Your problem will most likely be in the buffer layout, either wrong value, or something like that, or because it's vero, and 90% of "why doesn't it work" threads are because vero is a royal PITA.

You don't get signal bleed from using non-shielded wiring. Shielded wire is for RFI, op amp oscillation, motorboating, hum and noise and all that good stuff. The enclosure certainly doesn't matter.

[Bandwagonesque]

Hi everyone. Thanks a bunch for your replies. patrick, you're correct that pete used coax for the in's and out's. And its funny, it DOES change the sound when you move the lead going from the output from the buffer to the 3pdt and then to the main circuit boards input. One thing I forgot to mention in my initial post is that when all the knobs are on 10 and the pedal is on, there is a whine that occurs. when I back off the volume and dirt to say 3 oclock, it goes away. When I moved that lead all the way over towards the left of the enclosure while the knobs where on 10, I could hear it fade until it went away completely once i stuffed the lead under the battery droor. So I then checked if that helped the bypass bleed but unfortunately, its still there. I then decided to coax the inputs and outputs, heres a gutshot.



note the lead from the buffer being drawn and stuffed all the way under the battery. I then checked again and this didn't remedy the bypass bleed either. I wasn't to disappointed i guess after reading garcho's reply as if it wasn't even the single lead wire causing the issue, what would the coax do. but I had to try it out anyway.

I followed the original layout to a T and didn't substitute any parts aside from the bc549 and used a 549C but don't think that would make a difference. I also used a 1n5401 diode that is the largest silicon diode ive seen but i guess it should work. Would replacing this with an 1n4001 maybe help? is there anything else on the circuit I should try coaxing as well? here is a closeup of the buffer circuit, i dont see anything wrong but would love to be stood corrected. all caps are have a minimum voltage of 25V too.



Hi r080, I did run into this very same problem with my g2 i built (sans the oscillating/whining on 10).  Heres a gut shot of that one, im gonna sit down now and start moving wires around to see if maybe that will quite things down but wont count on it as much as maybe seeing an error in my buffers. would posting voltages help?

[r080]

It looks like the ivlark Cornish buffer layout has a 50k resistor at the output, while many schematics have a 50R. If I read that right, you have about a 5k (1% resistor markings really mess with me).

[Bandwagonesque]

ahhh how did i not see that. well, that is indeed a 4.99K 1%. i can't for the life of me remember why I used that value (it has been a long long time since I initially built these buffer daughter boards). Well I went right ahead and replaced it with a 50ohm resistor. Unfortunately, that didn't  alleviate the bleed i was getting. I then went and used a 50K per the original layout and that didn't appear to do anything either.

here is one weird thing to note. while I was testing things out, the bc549C transistor in the buffer fell out of its socket and didn't appear to change anything sonically. Basically the pedal worked with or without it in there. Could someone tell me why or if this is normal?

I may be at the point of giving up and rewiring things to remove the buffer altogether. I had been testing this with a stock strat with ok pickups and didn't really pickup on the differences of the bypassed signals between having the cornish buffer inline vs my guitar right into the amp. I got my go-to guitar back from the tech today which has some high output pickups and it really magnified that the buffer isnt as good as I was hoping and actually preferred it not there after all so this may all be for naught. id love to see if ive been doing something wrong this whole time and be surprised. After r080 pointed out that resistor difference, i found this layout that appears to be closer to the original schematics that i may try.

[Bandwagonesque]

this is incredibly embarrassing if this does happen to be the culprit, but am I needing to hook up the 9V power and ground up from the buffer circuit (if looking at just the buffer layout provided in my 1st post below)? I basically copied the buffer-into-main circuit wiring layout verbatim, and in that layout it only points out using the input and outputs, totally omitting the 9V and ground. I wired it as such without any power or ground and now its making sense my issue with the bc549 transistor in the buffer, falling out of its sockets and not causing any effect. I had always assumed it was a passive buffer 

[PRR]

> passive buffer

Huh??

The transistor works by modulating an interesting but weak signal (guitar etc) onto a boring but strong source (battery) to make a strong interesting signal.

Not feeding the transistor some boring battery misses the point.

[Bandwagonesque]

jeez, well heres to putting it in to practice in the morning and getting things powered up. can't believe i went this long without seeing it. thanks for the confirm prr

[garcho]

^ "did you turn it on?" and "did you plug it in?", two extremely important questions in troubleshooting

[r080]

In school, garcho's two troubleshooting techniques fixed probably 75% of my issues during labs. Taking it apart and putting it back together was the other 25%. It is humbling to see I did not get that ingrained well enough to notice what seems obvious now.

Hopefully your bleed issue will be fixed now. Both those circuits are fun.

[Bandwagonesque]

hi guys, thanks again to all involved. so i did indeed overlooking powering up the buffer circuit and once i got that going, along with using shielded coax for the in's and out's, it got this thing quite and now sounds incredible both on and bypassed. reallllllllly happy with the results and really happy I didn't settle with the bypass bleed as some quirk (alot of old pedals and a couple new ones suffer from this) and got to the bottom of it with most of the thanks going to you guys for the help. probably gonna wire up both of them up in the same box soon, they play very well together especially the g2 going into the ss2.