There's no Whining in Tonebenders RIGHT?

[Govmnt_Lacky]

So I built myself a Tonebender circuit with a MAX1044 voltage converter. Very thick fuzz    Love it!!!

One problem and I think this will be answered rather quickly but...

When I turn the Fuzz knob past 2 o'clock, I get a low pitched whining 

I can still get fuzz when I play through it but, when the strings are muted I get the constant whine.

Is this just a matter of transistor bias?

Voltages: V+ = -9.16

Q1
C: -9.07
B: -.06
E: 0

Q2
C: -.57
B: -.12
E: 0

Q3
C: -4.14
B: -.56
E: -.41

Thoughts??

[digi2t]

Hmmm, just a thought...

Try going around the 1044, and try it with a battery. Just to make sure that it's not the 1044 that's whining.

[Govmnt_Lacky]

Thanks Dino

I'm 99% sure it's not the MAX chip. I'm not getting the whine at all over the first 70 percent of the fuzz pot travel.

Also, I do get the whine on battery as well.

If its any consequence, I'm using a 1KC pot for the Fuzz.

[John Lyons]

Most likely oscillation if you get it at the extreme of the fuzz pot.
How long are the in.out wires are are they routed together?

[Govmnt_Lacky]

Most likely oscillation if you get it at the extreme of the fuzz pot.
How long are the in.out wires are are they routed together?

Just separated the input and output wires from the PCB to the 3PDT switch to opposite sides of the enclosure.

Still getting the whine.

In/out from jacks to switch are shielded.

[R.G.]

(1) does it have any decoupling on the board?
(2) Are you using stereo-jack ground switching for power?

[Govmnt_Lacky]

(1) does it have any decoupling on the board?
(2) Are you using stereo-jack ground switching for power?

Hey RG

1) YES. there is power decoupling on the board.
2) NO. I am using your switching scheme actually! From GeoFX. You may remember my other thread about it that you were assisting with 

[Govmnt_Lacky]

Could this be caused by a mis-biased transistor?

Do any of the voltages look suspicious?

[LucifersTrip]

Hey G L,

You're referring to a MKII?   Can you please post a link to the schematic you used. There are numerous small variations...

If MKII, then yes...the voltages are way off. Q3 is usually in the 7.5 - 8.5V+ range. Here's one example from an original:

Battery: 9.46
Q1 C: -9.02V
Q2 C: -0.22V
Q3 C: -7.57V

Also, it is actually pretty common to get some oscillation in the final 10-20% of the fuzz. I've experienced that with numerous builds.

...which is why there's an optional 100ohm on the fuzz pot



good luck

[chromesphere]

Hey G L,

I had this same question about 2-3 weeks ago about the mkII.  I was getting the whining / hum noise at the last 10% of the gain turn.  I posted my question here, and our kind friend mr lucifer explained what he said above.  I think i now owe him my soul.

Anyway, I was happy with that conclusion, i didnt add the 100 ohm resistor though because as you said, you can still play and it sounds fine, you can only hear it when you stop playing.

Edit: Sorry dont mean to hi-jack GL, but i just wanted to ask, what does decoupling mean (RG's question?).  I've made a few PCB's with charge pumps, they all work as expected, just wondering what the term decoupling means. Thanks

Paul

[pinkjimiphoton]

greg,
check the wiring. sounds like somewhere you may have an almost invisible short somewhere, maybe a piece of shielding braid.

if it were a high pitched whine, i'd say charge pump...i found grounding i think it was pin 6 or 7 can help on a couple of the centaurs i built.

could it be motorboating from a leaky cap? sometimes motorboating manifests in a long low whining noise once the gain gets to a certain point.

does it change when you turn the knobs on the fuzz or your guitar?

[Govmnt_Lacky]

Thanks ALL for the help!

Turns out.... the Fuzz King (a.k.a. LucifersTrip) was 99% correct. 

All I had to do was solder in a 130 ohm resistor between the Fuzz pot Lug 3 and the PCB and all was well.   

Turns out.... there is NO whining in Tonebenders........ once you add the resistor that is 

[pinkjimiphoton]

yah, dave is the lizard king of fuzz, fo sure!

psyched!! 

[R.G.]

I had this same question about 2-3 weeks ago about the mkII.  I was getting the whining / hum noise at the last 10% of the gain turn.  I posted my question here, and our kind friend mr lucifer explained what he said above.  I think i now owe him my soul.

Anyway, I was happy with that conclusion, i didnt add the 100 ohm resistor though because as you said, you can still play and it sounds fine, you can only hear it when you stop playing.

The 100 (or close) resistor lowers the maximum possible gain inside the feedback loop that the two transistors make. I suspect that this keeps it from picking up enough feedback to oscillate. Good fix.

Edit: Sorry dont mean to hi-jack GL, but i just wanted to ask, what does decoupling mean (RG's question?).  I've made a few PCB's with charge pumps, they all work as expected, just wondering what the term decoupling means.

In the real world, wires are low-value resistors, not true short circuits, and power supplies have internal resistances, not rock-steady supplies of voltage at any current. As a result, drawing current in one part of the circuit can cause the power supply to dip a little bit and that can be picked up in another part of the circuit. They are coupled by the shared resistance/impedance of the wires and power supply internal set up. Adding a capacitor from power to ground very near the part of the circuit that uses the current lets high frequency currents flow in a loop through the circuit and the local capacitor, which acts much like a local battery to keep sudden current pulses from being felt by other parts of the circuit. So circuit sections may be de-coupled by local power-to-ground capacitors.

[Electric Warrior]

Hey G L,

You're referring to a MKII?   Can you please post a link to the schematic you used. There are numerous small variations...

If MKII, then yes...the voltages are way off. Q3 is usually in the 7.5 - 8.5V+ range. Here's one example from an original:

Battery: 9.46
Q1 C: -9.02V
Q2 C: -0.22V
Q3 C: -7.57V

Also, it is actually pretty common to get some oscillation in the final 10-20% of the fuzz. I've experienced that with numerous builds.

...which is why there's an optional 100ohm on the fuzz pot



good luck

Sola Sound got rid of that 100Ω early on. Even in the units that have it's out of circuit rather often (they only had to move a wire to a different hole on the circuit board to move it in or out of circuit). Later units have larger power filter caps or two of the 25µF ones in parallel, which can help with the oscillation, too.

Q3 C sure seems too low while Q2 C measures too high.

Here's a complete set of voltages from my vintage unit:

Battery: -9.67V

Q1 C -9.02 B -0.03 E 0
Q2 C -0.17 B -0.08 E 0
Q3 C -8.44 B -0.17 E -0.11

[Govmnt_Lacky]

Well.. Im quite happy with the sound coming out of this bad boy so I am going to keep the voltages where they are!!!

Nice hammering, thick fuzz at full bore. Smooth OD/fuzz with the pot full CCW and a little turning back on the Volume. 

[Quackzed]

I just built an npn axis face / npn tonebender (added a dpdt to include/omit the extra stage of the tonebender).
and had the same result. well kind of, i have high pitched whine at last 5% of the fuzz pot. i thought it might be the input wires going to/from the dpdt to the board. haven't tried fixing it -doesn't bother me that much- but i'll try a 100ohm b4 the fuzz pot as well as some local caps, maybee then i'll still have to shield the input wires, but this thread is perfect timimg for me!
so a second hand thanks for these suggestions.
btw, sounds nice and thick and great. had a go at my 'open mic' on some zep and love LOVE the nice singing sustain on high notes as well as the thick chewy saggy low notes when you lean into it. axis face mods are great for silicon tonebenders as well as fuzzes!!!

[LucifersTrip]

I just built an npn axis face / npn tonebender (added a dpdt to include/omit the extra stage of the tonebender).
and had the same result. well kind of, i have high pitched whine at last 5% of the fuzz pot. i thought it might be the input wires going to/from the dpdt to the board. haven't tried fixing it -doesn't bother me that much- but i'll try a 100ohm b4 the fuzz pot

remember, the 100ohm is not set in stone. You never (at least I don't) want to remove more fuzz that you have to (sacrilege). Simply place a 500 ohm pot there, start at 0 ohm and turn up until the oscillation stops. I used a 70 ohm and 110 ohm in my last two, respectively...

[LucifersTrip]

Well.. Im quite happy with the sound coming out of this bad boy so I am going to keep the voltages where they are!!!

Nice hammering, thick fuzz at full bore. Smooth OD/fuzz with the pot full CCW and a little turning back on the Volume. 

yes, it can sound excellent even at those voltages, but be aware that it is almost impossible that it will really sound like a Tone Bender.

honestly, among the common Fuzzes, I think this one may be the most difficult to get to sound the way it should, since you have to experiment with leakages of at least two (Q2, Q3) of the transistors....and the leakage of Q1 does also matter, but to a lesser extent. The fact that your leakages are so far off is the reason you aren't close to the classic Tone Bender voltages.

TO make things a bit more difficult, the hfe's of Tone Bender transistors vary heavily from (60, 60, 90) to (40, 40, 200) to (200, 200, 200...my favorite), etc....so, honestly, the best thing to do is to make multiple ones. That circuit can be so killer, it's worth it!

[Arcane Analog]

yes, it can sound excellent even at those voltages, but be aware that it is almost impossible that it will really sound like a Tone Bender.

100% agreed.

honestly, among the common Fuzzes, I think this one may be the most difficult to get to sound the way it should, since you have to experiment with leakages of at least two (Q2, Q3) of the transistors....and the leakage of Q1 does also matter, but to a lesser extent. The fact that your leakages are so far off is the reason you aren't close to the classic Tone Bender voltages.

TO make things a bit more difficult, the hfe's of Tone Bender transistors vary heavily from (60, 60, 90) to (40, 40, 200) to (200, 200, 200...my favorite), etc....so, honestly, the best thing to do is to make multiple ones. That circuit can be so killer, it's worth it!

I made up a test box that really helped me learn my tastes in MKIIs with regards to HFE and Leakage. You can get masssive differences with the same device type (ie OC75, etc) but with different HFE/uA attirbutes. I persoanlly find leakage to be more important than any specific HFE as long as there is enough gain to get the fuzz happening.