War Scythe transistor question

[Kroars]

So, I’m building my 2nd War Scythe. First went great, but I used mostly cheap components from Amazon. Now that I’ve built up a good supply of quality components I want to give it another go to see if I can tell a difference (and because it’s a great pedal).

Question: What am I looking for in gain (hfe) & leakage (ua) in the AC176 and both 2n1308’s? Ive got a multi tester for components and would love to dial in the ideal sound for this pedal.

Probably a question I should’ve asked prior to building the first, better late than never I suppose.

Thank you in advance!

Ryan

 

[Chuck D. Bones]

First of all, don't feel like you need to use those exact part numbers. For the Hoof (Muff) side of the circuit, low leakage is absolutely required. HFE around 100 is fine. High HFE is not beneficial here because EQD screwed up the biasing. As with all Ge transistors, I highly recommend sockets. For the Hoof, you want the collector voltage on Q4 and Q5 to be above 2V. 2.5V to 3.5V is better. Be sure you set SHIFT to zero when measuring Q5's collector voltage. For the Tone Reaper side of the circuit (Q2), a certain amount of leakage is required. Low leakage makes for strong gating. If the leakage is too low, very little sound gets through. A high leakage transistor for Q2 will have a strong fuzz tone with little or no gating. It's a matter of taste. Try different Ge transistors for Q2 and pick the one that sounds good to you. Q2's HFE is not important because at high FUZZ1 settings Q1 drives the shit outta Q2. You didn't ask, but I'll tell you anyway: matching in the Octave part of the circuit makes for a stronger octave tone. R39 - R42 should be 1% resistors. match D6 & D7 for Vf at low current (100uA or lower) if you can. Use 5% film capacitors for C25 & C26.

 

[Kroars]

First of all, don't feel like you need to use those exact part numbers. For the Hoof (Muff) side of the circuit, low leakage is absolutely required. HFE around 100 is fine. High HFE is not beneficial here because EQD screwed up the biasing. As with all Ge transistors, I highly recommend sockets. For the Hoof, you want the collector voltage on Q4 and Q5 to be above 2V. 2.5V to 3.5V is better. Be sure you set SHIFT to zero when measuring Q5's collector voltage. For the Tone Reaper side of the circuit (Q2), a certain amount of leakage is required. Low leakage makes for strong gating. If the leakage is too low, very little sound gets through. A high leakage transistor for Q2 will have a strong fuzz tone with little or no gating. It's a matter of taste. Try different Ge transistors for Q2 and pick the one that sounds good to you. Q2's HFE is not important because at high FUZZ1 settings Q1 drives the shit outta Q2. You didn't ask, but I'll tell you anyway: matching in the Octave part of the circuit makes for a stronger octave tone. R39 - R42 should be 1% resistors. match D6 & D7 for Vf at low current (100uA or lower) if you can. Use 5% film capacitors for C25 & C26.

Great! Thank you very much Mr. Bones! Love this forum!!

 

[nichgriff]

First of all, don't feel like you need to use those exact part numbers. For the Hoof (Muff) side of the circuit, low leakage is absolutely required. HFE around 100 is fine. High HFE is not beneficial here because EQD screwed up the biasing. As with all Ge transistors, I highly recommend sockets. For the Hoof, you want the collector voltage on Q4 and Q5 to be above 2V. 2.5V to 3.5V is better. Be sure you set SHIFT to zero when measuring Q5's collector voltage. For the Tone Reaper side of the circuit (Q2), a certain amount of leakage is required. Low leakage makes for strong gating. If the leakage is too low, very little sound gets through. A high leakage transistor for Q2 will have a strong fuzz tone with little or no gating. It's a matter of taste. Try different Ge transistors for Q2 and pick the one that sounds good to you. Q2's HFE is not important because at high FUZZ1 settings Q1 drives the shit outta Q2. You didn't ask, but I'll tell you anyway: matching in the Octave part of the circuit makes for a stronger octave tone. R39 - R42 should be 1% resistors. match D6 & D7 for Vf at low current (100uA or lower) if you can. Use 5% film capacitors for C25 & C26.

I'm just starting to build the War Scythe. What would you recommend for Ge transistors? I'm having a hard time sourcing any that would seem to work. I've looked at AC128, AC176, 2N404 (I can source these more easily but unsure if they'll work?). Would the MPS13 or MPS18 work in Q2? Sorry - I'm new to all of this!

 

[Chuck D. Bones]

You need NPN Ge transistors for Q2, Q4 & Q5. AC128 & 2N404 are PNP and will definitely not work. Try the AC176 or any other NPN Ge transistor. Buy a few of them. If you can get real 2N1308s (or 2N1306s), those are good for Q4 & Q5. Small Bear is a good source for Ge transistors, but are closed at the moment. Try PedalHacker. Experienced builders have a collection of Ge transistors because various circuits (and tastes) require transistors with different hFE and Iceo. You will need a DMM to check bias. Alternatively, build the Hoof side as a Cloven Hoof and use MPSA13 for Q4 & Q5, in accordance with the Build Docs. Definitely use sockets any place you install Ge transistors. The sound of the Reaper side is very sensitive to Q2's leakage and you will most likely be swapping transistors there.

If this is your first pedal, you're in for a learning experience.

 

[nichgriff]

You need NPN Ge transistors for Q2, Q4 & Q5. AC128 & 2N404 are PNP and will definitely not work. Try the AC176 or any other NPN Ge transistor. Buy a few of them. If you can get real 2N1308s (or 2N1306s), those are good for Q4 & Q5. Small Bear is a good source for Ge transistors, but are closed at the moment. Try PedalHacker. Experienced builders have a collection of Ge transistors because various circuits (and tastes) require transistors with different hFE and Iceo. You will need a DMM to check bias. Alternatively, build the Hoof side as a Cloven Hoof and use MPSA13 for Q4 & Q5, in accordance with the Build Docs. Definitely use sockets any place you install Ge transistors. The sound of the Reaper side is very sensitive to Q2's leakage and you will most likely be swapping transistors there.

If this is your first pedal, you're in for a learning experience.

Okay, great! This isn't my first build but it's the first that doesn't have easily sourced parts. But I just found most of what I needed on Pedalhacker! Thank you!

 

[music6000]

Okay, great! This isn't my first build but it's the first that doesn't have easily sourced parts. But I just found most of what I needed on Pedalhacker! Thank you!

Warning, Be careful of Pedalhacker parts, I have 20 J201's that are all out of Spec by a long shot!
I'm in Australia so it's quite Inconvenient & he doesn't answer Emails!

 

[Chuck D. Bones]

I have personally not done business with PedalHacker, but I know people who have had good experiences. Not good that they're blowing you off. That's what separates the good vendors from the bad: what they do when things go sideways. I have nothing but good things to say about Small Bear.

 

[music6000]

I'm in Australia & have no affiliation with Small Bear Electronics.
I have purchased of Small Bear more than any other company!
Why, He stands by his products & the only issue I've had is a wrong part or broken pot in transit & he sends out another straight away at his expense.
He sells Products that are reliable, I never had one that failed & if it did he would give me the option for a refund or replacement.
He sells CIC Blue 3PDT Footswitch's that are stamped ROHS & I never had a Failure in over 100 + Builds.
I have purchased a few pedals that have Footswitch failure & it is the number 1 component to fail so I wont buy anything else!!!

Cheers music6000

 

[Ratimus]

In mine, on the Hoof side, I've got a 2N1306 for Q5 and a silicon 2N2222A (hFE 120) for Q4. I bought 2 2N1306s from Small Bear to use in it, but one of them leaks so bad that my Peak DCA75 thought it was a low-gain Darlington. I have some other Ge NPNs in my stash, but they're all too leaky for this application.

The lower gain Si sounds fine to me since it's earlier in the signal path and gets colored by the Ge at the end. Honestly, the use of Ge in this circuit at all is arguably a mojo/marketing thing. The clipping diodes have far more influence on the sound than the transistors do. The original BMP was "better designed" (from a textbook point of view) than most fuzz circuits in the sense that inconsistencies between transistors will have much less affect on the tone than will changing things like the tone stack or clipping diodes [things which happen to be more consistent and easier to control].

On the Reaper side, I've got some garbage AC187 with an hFE of 12 and that leaks around 160 uA. Sounds great. Like Mr. Bones mentioned above, the gain is less important here since it's already getting slammed by the previous transistor. It functions more as a wave shaper than it does a gain stage.

 

[Nostradoomus]

I have personally not done business with PedalHacker, but I know people who have had good experiences. Not good that they're blowing you off. That's what separates the good vendors from the bad: what they do when things go sideways. I have nothing but good things to say about Small Bear.

I did not know about this until today but the guy who runs pedalhacker is apparently a notorious scam artist. Owns Nose Pedals as well. Google it and decide for yourself but I’d stay clear.

 

[Ratimus]

I recently bought 10x BC109c from PedalHacker, along with some other mid to high gain Si "jellybeans." No issues and the gains are all within +/- 0.2% of each other for each type. Took a while to ship, but not a huge deal. Sounds like he's nothing if not inconsistent.

Music6000: since you're in Australia, have you tried DiyGuitarPedals.com.au?

 

[music6000]

I have a Good supply of NOS Siliconix & Sprague J201's now that are all in Spec!
Paypal sorted Pedalhacker out !!!
I pointed out to another Member about Pedalhacker & his practices. He lists Jfets that will work as substitutes for J201, there isn't any!