UMI Buzz Tone

[Henry89789]

Lucifer: Thanks for the reply. I guess I spoke too soon. It looks like I might have had the expander on all the time (the voltages were very similar on both sides of that switch).  I had the expander switch wired wrong. After fixing that, the voltages changed (but they are still quite different from the voltages you posted);
  Voltages:

Transistors:
Q1: AC 125, hfe: 77; leak: .226
Q2: AC125, hfe: 133; leak: .578

Q2: 
SW1: E: -7.70;  B: -7.37;  C: -8.58
SW2:  E: 0;  B: -.05;  C: -.07

Q1:
SW1:  0;  B: -.10;  C: -5.43
SW2:  0;  B: -.10;  C: -5.42

Rewiring that switch definitely made a difference. Both the expander switch and the contour and buzz pots have an effect now. A lot better.  I am going to put it on the board and take it through its paces as much as I am able to. Thanks. Your suggestions helped me fix it .

[pinkjimiphoton]

glad you got it working!!

i would still try a plethora of transistors until you find what works for you best.

[Henry89789]

Pink jimi:

Thanks. I liked the sound of yours on the you tube video you posted. That's why I built it. You said you liked 120 hfe transistors for both Q1 and Q2. Is that what you had in it when you  made the video? Right now I have typical fuzz face transistor values in the pedal, i.e., 77 and 133 hfe, but I am going to see if I have some in the 120s to put in both.

[pinkjimiphoton]

hi bro,

yah, i had rough-sorted a bunch of pnp ge's by hFe, and arbitrarily grabbed two from a pile that were between 120-125 hfe. they tend to kinda change depending on temperature, so i didn't worry too much about the exact numbers.

i usually socket and experiment. this thing can sound great even with some really high gain transistors, too... try some and see what works!! some silicon ones almost give an octave up effect.

[Roger Martin]

So, what kind of transistors should i use to yield that 60's acid rock buzz tone ?
It can give sometimes a fat creamy one, but on the other occasion it can be a bit screamingly high pitched buzzing. 

[LucifersTrip]

So, what kind of transistors should i use to yield that 60's acid rock buzz tone ?
It can give sometimes a fat creamy one, but on the other occasion it can be a bit screamingly high pitched buzzing. 

In this thread, I gave detailed descriptions of what the different leakages/voltages will give you. If you want something close to the original, choose two with leakages around 300uA +.  I quickly measured the transistors and thought I needed 400 - 500uA, but after really waiting for them to settle and playing in a steady 75 deg temperature, they turned out to have around 320 - 350uA.  Both had hfe's around 150. 

Until I posted this thread, I've never heard anyone ever refer to a Fuzz Rite or variant as creamy, so I wouldn't expect much of that...

[Henry89789]

until I posted this thread, I've never heard anyone ever refer to a Fuzz Rite or variant as creamy, so I wouldn't expect much of that...

Okay after learning some of the fuzz lingo, I  think what I understood by creamy is "smooth decay." I have been playing mine all night and it does not seem to like the Tungsram AC 125s I have, especially if the transistors have leakage over about .300 it can be a bit "screamingly high pitched.." Worse than that is what I think is called having a rough or ragged and uneven decay; the note won't sustain smoothly and evenly. It seems to break up. This thing is obviously very sensitive to the transistors it is fed. A picky eater. It doesn't like Russian GT308bs either. They sound horrible. The best sound I was able to get from the pedal with the transistors I have ( I don't have any 150 hfe transistors) was from Russian MP 15s; Only 50 hfe for both Q1 and Q2 but very low leakage; It has a warmer sound  with a mild  fuzz and  "smooth decay" with the guitar volume down then when you turn up the volume it gets good fuzz and sustain but not as shrill as the tungsrams. I am sure there are transistors out there that would sound even better.

[pinkjimiphoton]

i know it's sacrilege, henry,
but try some silicon. will get ya that over the top fizzy fuzzy goodness.

i'd imagine you could find a complimentary pair of silicons, and put them each on one side of a 3pdt toggle, and the ge's on the other.

maybe even a footswitch. then you can go from smooth to shrill at the stomp of a foot.

[mac]

i'd imagine you could find a complimentary pair of silicons

If you want to experiment with silicons, try BD175/237; they are low gain <100-150>, and low freq <3mhz>.
Q1 does not need bias changes.
At Q2 you need to add a resistor to feed the base. Try 100K to 10M from C to B, 0.7v to 4v resp.

mac

[LucifersTrip]

if you want si, you can just go for the Orpheum with no work. You can sub a pot for the 47K for some tone changes.

http://tonebender.webs.com/orpheum-SILICON.GIF

edit:
but don't use 200 - 300hfe as suggested in the schematic. As Mac noted, lower gains in the 100 range would be better.