testing a buffer

[pufferton]

so im about to build my first buffer. i have built a SHO that didnt work at first so i have some experience with troubleshooting the build.

my question is how do i go about testing if my buffer "works"?

testing other pedals are obvious: are you getting unity audio when off and is it producing the desired effect....but a buffer doesn't exactly alter my sound...just help drive my signal through my PT Pro board.

what should i be looking for if i did a good or bad job?

thanks!

[mremic01]

The SHO will give you quite a bit of clean boost and eventually get a little dirty. If you want to test a regular buffer, the bypassed signal should sound exactly like the effected signal. Unless you're losing high end due to cable capacitance, then the buffered signal should preserve your high end. If your buffer isn't on a switch, then as long as you're getting your signal output, you should be fine. I would use a true bypass looper to test it though, just to make sure that your buffer sounds the way you want it to. I like Jack Orman's JFET buffer. I built the IC buffer from General Guitar Gadgets and found that that one sucked more tone than it preserved.

[GibsonGM]

+1 on the JFET.  Very transparent and just what the doc ordered in a buffer! 
J.O's stuff is excellent.

[Digital Larry]

Plug it into a Fuzz Face and make sure it sounds like complete crud (as Fuzz Face type circuits don't like being driven by a low impedance).   

[kingswayguitar]

Plug it into a Fuzz Face and make sure it sounds like complete crud (as Fuzz Face type circuits don't like being driven by a low impedance).   

i tend to agree...i don't put my trusty jfet pedals into fuzz face

[samhay]

If it passes signal at ~ unity gain when powered then you have a buffer. Test it by removing the battery/DC jack...

[darron]

If you can't tell if its working, then you don't need it there

I still put a 3pdt bypass switch on my buffers just so you can know how much difference it is or isn't making in certain points.

[duck_arse]

the buffer is meant to drive low impedances. load down yr output w/ a lowish value resistor, and see if you still get output. not too low, though.

[pufferton]

great thanks everyone!

[pufferton]

testing my build im getting a weird, pulsing noise when powered on. its coming through every jack when i audio probed it. it also pulses my LED so i know its a power issue but don't know what it could be....

any help?

[darron]

testing my build im getting a weird, pulsing noise when powered on. its coming through every jack when i audio probed it. it also pulses my LED so i know its a power issue but don't know what it could be....

any help?

like ON OFF ON OFF ON OFF or fading in out?

maybe it's a short and your power supply's regulator is going into self protection? can you measure a stable voltage at the DC socket?

[pufferton]

on off on off

how do i measure a stable measurement? i have a multimeter...just not a lot of experience

[darron]

yep. if it's a solid on/off then that might be it.

well, if you set your meter to DC and measure at the power supply socket, does it give you a solid reading of roughly 9v? otherwise it could read less of flicker and not read properly at all


that's just my first suspicion for the symptom you're describing... try to find where +9V is shorting to the earth/casing/negative.

[pufferton]

the jack and board both fluctuate from 1-2v

the power supply itself is good. it reads at 9v

[darron]

still the same guess. if you short out a well built power supply then it will go into self protection mode to stop from overheating and blowing and IC. when it's just back on the threshold of survival it will turn back on. so that is the fast pulsation.



so you'd need to look for a short in your circuit between positive and negative. a couple places to look:


anything accidentally touching: is the resistance (multi metre) between the pos wire and neg wire reading a short circuit?

backwards parallel protection diode?

are the positive and negative wires connect to the right socket terminals?

[pufferton]

still the same guess. if you short out a well built power supply then it will go into self protection mode to stop from overheating and blowing and IC. when it's just back on the threshold of survival it will turn back on. so that is the fast pulsation.



so you'd need to look for a short in your circuit between positive and negative. a couple places to look:


anything accidentally touching: is the resistance (multi metre) between the pos wire and neg wire reading a short circuit?

backwards parallel protection diode?

are the positive and negative wires connect to the right socket terminals?

just triple checked everything...had some issues, fixed them but still the same problem....would it do this if i had a bad component? i removed the board from the chain and i get 9v from the dc jack and LED shines steady. no 1/4" jacks are hooked as of right now.  as soon as i wire everything back up its flashes and i get 1-2v reading.

i reflowed every solder point, and sawed down the the lanes to thwart any bridges. i'm using a magnifying glass.
no diodes in this build.
wires are on correct terminal.

ill upload a photo.

[pufferton]

http://postimg.org/gallery/alul4cjk/

so it looks extreamly messy cause i have taken it apart 4-5 times.... 

any idea??

[stallik]

It's late, I'm tired so I may be mistaken but that ic looks to be orientated the wrong way round

[pufferton]

oh....i didnt know there was a wrong way....hmmmm....

this is my second pedal build...first with an op-amp...are there markings on it to determine which is the right orientation?

[pufferton]

It's late, I'm tired so I may be mistaken but that ic looks to be orientated the wrong way round

ah crap...thats what the dot means...so i should put the dot in the top left corner right?