Using the AUDIO PROBE (FF example)

[analog kid]

I just made an audio probe to use on the Multiface I 've been trying to de-bug( see my other posts for those problems) basically just that the Fuzz or the volume can't be turned up all the way (for the Fuzz) or past about 2 (for the volume , If the Fuzz pot is up most of the way....IF they are not kept down enough the effect produces a HORRIBLE 'transistor like" Squeal! Anyone who's ever touched the legs of the Transistors on the underside of the board when effect is on... That's the sound it makes.
My question is.. although I get how to hook the probe up and that you should make your way through the circuit listening to how the sound is affected by the probe. but I don't get WHAT it IS that you listen for> I just hear normal pops and cracks you get from touching components.  SO I assume you need to plug an source in as well and listed to "IT" as you touch the probe to input, transistors, caps, etc... IF THIS IS CORRECT,
I may have located an area of problem!? Every part of the circuit gives me either increases or decreases in volume but the signal is basically the same  EXCEPT... When I touch the probe tip to the INPUT of the crkt.(being the IN wire Pad that goes to the switch, .1uf non-polar cap which I don't have socketed, the BASE of Q1 , and one side of R3 100k ) I get the same STRANGE NOISE produced through the amp that the probe is connected to!!!! So first, IF this is not a normal noise..... Should I just start taking out the components there to check them, check the input cable going to swich, ?? I wouldn't know what to check as far as the Q1 BASE , I mean it's plugged in the socket and the leg isn't grounding out on anything so Not much can be wrong there.
THE ONLY THING I SHOULD POINT OUT different ABOUT THIS INPUT AREA OF THE CIRCUIT IS>>> I have the Mosfet Protectoin LED omitted that connects between the Q1 Base/.1uf Cap And Q1 Emitter.
( I assumed from the article this could be left out w/o a jumper if desired)
http://www.runoffgroove.com/multiface.html

[guitarmonky55]

the audio probe shows you how the signal of the guitar is affected at various points.  i plug my guitar in and set it on the stand  and then strum the strings and poke around with the probe.  when you touch at certain points where the audio signal passes through you should get the guitar's sound through your amp, plus any effect added up to the point of the circuit where you are.

[analog kid]

well you verified something that I figured and hate to admit cause it's pretty stupid!>.... but I guess you WOULD have to be using separate Amplifiers to use an audio probe would'nt you??!!
I had it plugged in to inputs 1 and 2 on my Deluxe, thinking I 'd get at least enough of the signal to hear what's going on from both.
Although , I still wonder.... You say that if you touch the probe where the signal PASSES you will hear the audio OR guitar from the probe amp. WELL, If you probe an area and hear something (strange or different) like I did , does that mean that the part of the crkt you're touching would make the guitar sound that way through the amp normally WHEN IT's Active???
I'm referring to that horrible squeal at certain areas of the pots rotation that I get AND me getting a very similar sound from the probe when touching the INPUT/Capacitor/ (to Q1 Base) part of the circuit

[analog kid]

Here's an update on what I'm getting using the probe and tell me if it's normal:
when I leave the volumes at a level that doesn't bring on the 'squeal'>

(and one more time to clarify THIS IS NOT a Feedback/Gain Squeal! it's a high pitched electrical "sputtering transistor" type noise
I get the effected signal throught the probe amp when touching the OUTPUT cap, Q2 Emitter, Collector and Base , and Q1 ONLY the Collector

NO SIGNAL at all from the INPUT Cap , Q1 Emitter AND Base, 22uf cap + or - OR the +9v area , which may be norm.

When turning the pots up to the point of bringing on the squealing:
 'All points with signal and NO SIGNAL are the same as before EXCEPT... the NO SIG points now pass the JUST the "squeal part" of the audio through the probing amp!!!     Weird?
  HOW DOES ALL THIS SOUND?

[analog kid]

Scratch EVERYTHING concerning the NO SIGNAL with probe points I tested!!!!
I tried again this time turning the volume WAY up past the Squealing and found that all those points.. +9vlt, Input Cap and that side of 100k resistor R3, Q1 Base,  and 22uf cap + side . It's just that the Probing signal volume of all these points are SOOOO LOW  that they can't be heard unless I cranked the volume pot AND the Amp volume to the point where the previous Signal points(Q2 B,C,E, etc...) would blow the speakers if you hit the strings!
Sorry but I hope something here points out the problem , Or if this is normal someone please let me know!   As I said this probing is a new thing to me.

[Johnny Guitar]

I don't know what a MultiFace is  :oops: , but when I built one of my FFs, I tried to use a negative ground and had similar oscillation issues. I have heard that it is VERY common (but not universal by any means) to find oscillations when trying to build a FF with a negative ground.

When I switched my FF to positive ground teh oscillations went away, and when I properly biased the transistors, it acted like a REAL FF.

[analog kid]

is "this" what Ocsillation really sounds like ?? I didn't think that's what I was dealing with since It's only present AT ALL when the pots  are turned up to a certain position. Like I said , touch your underside of the board on your fuzz face... Particuarly the transistor legs and you'll get this wierd 'radio interference/Pac-Man/squealing' sound and that's what I am getting constantly when the fuzz is all up, and or the volume up
 This IS a NPN circuit though as far as I know. Look at the good DIY website Runoffgroove and check out the Mult-Face "many faces of fuzz" articles and you'll see what this is

[petemoore]

NpN Si Neg Ground.
 What is the actual value of your gain pot?
  You started with a 10k ? ... what is it at now >?
 Measure the resistance across lugs 1 and 3 to see.
 Does the gain of the FF circuit increase as resistance of the gain pot to ground increases?
 IF that's the case and you're using a larger than 2k gain pot, or even an 1k5 and the circuit is gainy anyway and gain also depends on the transistors used...Turn the gain knob down to where it stops squealing, or taper it so it cant' squeal, set at max.
 I like a little room 'over the top' so I use a 2k or so linear gain pot, and then either taper it down, [but more often just] turn it down, otherwise the circuit acts up, is way too noisy, may self oscillate and generally be out of control, producing general noise or squealing high end.
 FF's get to actin' up...need to be 'tamed' sometimes...
 What kind of transistors are you using in it, and what are their Hfe gains ?
 Also rollof caps'll tame it down some.

[analog kid]

The pot is at 4.7k now. (down from 10k with a 10k resistor)
Please explain to me how to modify the "taper" of the pot> I have read about that and I've done the previous, changing value , many times but never the taper.
So you think I could mod the taper of it so that the pot even when turned full on , wouldn't be able to reach the point where that squeal come on?

You really do think this is a Normal "out of control" fuzz circuit? I could almost believe it if it weren't for the volume pot being so ungodly loud which also brings on the NOISE/

[dualaud]

i'm not very good at this, but maybe it would help if you could define the squeal.
please check out the demo video here:
h**p://www.zvex.com/fuzz.html

in the last third of the video he explains the boxes oscillation.
listen to it. is this the sound you're hearing?
this box is meant to squeal at certain settings.

did you check the orientation of the transistors?
you did adjust the trimm pot? that would be my first guess.
quoted from h**p://www.runoffgroove.com/multiface.html:

The 10k trimmer will need adjusted when swapping transistors. JFets are very sensitive to adjustment. Just turn the trimmer while playing to get the sound you want. You can get some sick sputtering sounds by intentionally mis-biasing. I found Jimi's Monterey "Wild Thing" sound by tweaking the trimmer.

cheers,
dual

[analog kid]

I have been using the probe on a Sparkle boost that I built recently and I'm getting a guitar signal through the probe everywhere I should be I believe> (exept for the Ground) Before Only the Volume pot was working and the effect signal was very weak in comparison. Now both pots function as they should But the volume is still very low!
SO if the probe shows signal on every component ,that's not going to ground , DOES THAT MEAN there are no problems within the circuit?? I realize that values could be wrong and it would still pass signal possibly and also since this is just a booster pedal You really can't tell how effect is building/forming as you progresss through the circuit.
So would you just check all values And then go to off board wiring IF the probe passes signal everywhere as I said???