pop of pedals after bufferbuild

[GeorgeSunset]

Hello everybody

I build a simple buffer for the effektloop of my amp, because the delay I use don't have any and gives a volumeboost of the signal of the loop isn't buffered. I used the schematics from singlecoil.com.

The buffer has no LED, is always on and run's on 15 Volt (all components are raided for over 15V).

My problem is that the delay pop's now when disengaging.

Is there a way to chance the buffer setup so the pop disappears?

Thanks for the help.

[jacobyjd]

Hey, welcome!

We may need a little more info on your setup--what amp are you using? I'm assuming it doesn't already have a buffer in the FX loop.

Do you have any other effects besides your delay placed in the loop? And what delay is it?

Also, where is the buffer placed--before the delay or after the delay?


All I really have to work on is my own experience--with my amp, I need one buffer placed before the effects in the loop as well as one placed after, otherwise I get huge pops when I switch true-bypass pedals on. To do this, I simply placed Boss pedals at the beginning and end of my chain (It's something like: FX Send>Boss Tuner>EHX Holy Grail>Vibrato>Analog Delay> Boss DD-20 delay>FX Return). They have a great buffered bypass, so if you have one sitting around, try putting it on the other end of your fx loop chain to see if 2 buffers fixes your problem

[GeorgeSunset]

Thank you

It's an old vox ad30vt (yes... i know. But it works)
I modified the amp to have the effectloop just before the master VOL pot.
The pedal is a Carl Martin Delayla XL. No other pedal is in the loop ( or before the preamp)

The thing with the buffer was a suggestion from a Carl Martin employee. It works to, but as I said, it pops now.

Hm. I will try to solder the buffer to the return (instead of the send) or will try to build another buffer and solder it in the circuit.

Other suggestions?

I'm thankful for everything

[GeorgeSunset]

Okay. I tried to put the buffer after the delay – no pop's, but got the volumeboost back
I tried to put a buffer in front + behind the delay (identical buffer) – still pop's men turning the delay off.

When I turn it on, there are no pop's. only when turning it off again.

Any suggestions?

[GeorgeSunset]

http://www.muzique.com/images/buff8.gif

I'm using this schematic.
As i said, V+ is 15 Volt. R1/R2 = 2 M

anybody???

[GeorgeSunset]

okay

I tried to use pulldown resistors like here http://www.muzique.com/news/pulldown-resistors/ (last pic)

i think it helped a bit. But i have to try it today with the normal playing volume.

I have a question though. If i hear a pop-reduction, but want more of that reduction - do i have to increase or decrease the pulldown resistor value? (I'm using 2M right now for input and output)

Thank you for helping

[rustypinto]

The pull down resistor at the input should always present a high impedance to the output of whatever it's looking at before it, which is supposed to be low impedance. 2M is great, but if there is any DC voltage at the output of the previous stage, or the input of your stage (the buffer), 2M is too large to bleed off the DC to ground effectively (which is whats causing the pop).

I suggest using 1M at the buffer's input side of the capacitor and then 470k at the buffer's output capacitor (these two capacitors being the light blue colored resistors on the muzique site). The R1/R2 (2M/2M) resistors can stay at that value if you are really using a TL071. This resistor divider should always be kept high in resistance when using JFET op-amps. You can get away with smaller values when using BJT based op-amps.

What are your coupling caps (ceramic, electrolytic, poly, mica)? If they are polarized, make sure you get the "+" side going to the higher voltage, and the "-" side going to the lower voltage. Note the Muzique site again: the 10uF cap at the output of the buffer has it's "+" going to the output of the op-amp because its at 4.5V and the "-" going to the output side because its (ideally) at 0V. Same deal if you're using a polarized cap at the input.

[CynicalMan]

http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ#POPS

[ubersam]

George- where did you put the pulldown resistor? Input of delay pedal or the return of the effects loop?

any chance of seeing a schematic of how you added the effects loop in the amp?

[GeorgeSunset]

Ahm...



I cut the input of the MASTER VOLUME pot, and put the loop in there. So the SEND is the signal that normally goes into the MASTER VOL pot, and the return goes directly to the MATER VOL.
Works great. the master vol works normally, the effectloop is affected by the master vol (or more correctly, the master vol is in control of the complet sound volume) and the line-out works normally.

I build the buffer just like the schematic i postet (with the pulldown resistors before the first and last cap) and yes, the buffer goes before the delay (because it didn't work when buffer was after the delay). So, the pulldown resistors are in the buffer circuit, not the delay circuit 

hope that makes sense.

I don't think i have the schematics anymore. i will look trough my pc later

[GeorgeSunset]

I suggest using 1M at the buffer's input side of the capacitor and then 470k at the buffer's output capacitor (these two capacitors being the light blue colored resistors on the muzique site). The R1/R2 (2M/2M) resistors can stay at that value if you are really using a TL071. This resistor divider should always be kept high in resistance when using JFET op-amps. You can get away with smaller values when using BJT based op-amps.

What are your coupling caps (ceramic, electrolytic, poly, mica)? If they are polarized, make sure you get the "+" side going to the higher voltage, and the "-" side going to the lower voltage. Note the Muzique site again: the 10uF cap at the output of the buffer has it's "+" going to the output of the op-amp because its at 4.5V and the "-" going to the output side because its (ideally) at 0V. Same deal if you're using a polarized cap at the input.

First cap is non-electrolytic (poly something). last cap is an electrolytic. and yes, the polarity is correct.
how do you get those resistor values? (just curiouse )

[ubersam]

try a pulldown resistor at the effects loop's return jack