zonk machine sugestions?

[tacobender]

So I've got my heart set on building a zonk machine after watching a YouTube video of someone playing an original, you know the one with the Guy playing the black and white rickenbacher. Anyway I loved the sound so I started digging threw my surplus gathering parts. So my question is what would be the suggested gain and leakage for a zonk? Is it pretty much like an mk2 or is this a different animal all together? ...Also any transistor recommendations would greatly help. Thanks

[duck_arse]

have you searched at geofex? I seem to recall someting there about a zonk.

[tacobender]

Ya, some but not much.I wonder if there is a tagboard layout for the zoning, I'm using pretty big caps and starting to run out of space

[duck_arse]

R.G.'s dissection has some transistor recommendations at the end. it looks a fairly simple sort of thing, surely shirley, it can't get too out of hand.

[Electric Warrior]

They used a number of different transistors and bias resistors for these. I suggest you look up gut shots and schematics...

You can find hfe and leakage readings of the pedal in the demo video you liked here: http://freestompboxes.org/viewtopic.php?f=19&t=16723&p=237346&hilit=zonk+machine#p238873

[Harry]

So my question is what would be the suggested gain and leakage for a zonk? Is it pretty much like an mk2 or is this a different animal all together? ...Also any transistor recommendations would greatly help. Thanks

It's a mki smaller caps and slightly different valued resistors. I just checked my notes and I ended up with q1=180hfe/.142ma q2=176hfe/.177ma q3=195hfe/.124ma on my zonk machine.

[antonis]

my question is what would be the suggested gain and leakage for a zonk?

R.G. said that:



and a schematic:



P.S.
I'm not sure but I think I've read somewhere that R6 should be 33k (not 3k3)...!! 

[Electric Warrior]

P.S.
I'm not sure but I think I've read somewhere that R6 should be 33k (not 3k3)...!! 

It's often hard to see in gut shots, but I've seen plenty of 33ks and no 3k3s there. 

[tacobender]

Thanks for the recommendations, I've been looking at different sites and it seems everyone has something different to say. Some say low leakage is good others say high, as far as hfe its up and down for Q1-3, and normally I would just socket it and tune by ear but I used Nos parts and my board is packed, for real most of my resistors are the big 2w. So Ive only got room to solder in the tranies. I've got some tungstram ac128's on the way, also some ruski mp21a's. So if anyone has built one they really dig I'd appreciate getting your hfe/ua.

[Harry]

Yeah, i went through the same thing with mine. I tried following others hfe and leakage specs, but in the end found it easier to just breadboard it. I found swapping transistors and audio probing each stage to be easiest. For me changing bias resistors just complicated matters. I was able to get it working with various leakages and stock values, but just went with what sounded best to me. Another good reason to breadboard is that it can be quite noisy with certain transistors. Both my zonk and mki's attack controls work more like a tuning control and balance the noise to sustain ratio. Not the type of fuzz you just crank to 10, it sounds best somewhere in the middle.

[Electric Warrior]

The thread on the "other forum" I linked (link got censored, whoops) has hfe and leakage measurements.
But even a quick look at the schematic can tell you a lot. Q1 is a very uncommon type, but Q2 is an OC75 and Q3 an OC44. It's no secret that OC75s are rather leaky (300µA and more is not uncommon), while OC44s usually have very little leakage (often low as 0).

But you really need to use sockets or a breadboard to find a set of transistors that sounds and works great... selecting transistors only by hfe/leakage readings is a bad idea.

[tacobender]

The thread on the "other forum" I linked (link got censored, whoops) has hfe and leakage measurements.
But even a quick look at the schematic can tell you a lot. Q1 is a very uncommon type, but Q2 is an OC75 and Q3 an OC44. It's no secret that OC75s are rather leaky (300µA and more is not uncommon), while OC44s usually have very little leakage (often low as 0).

But you really need to use sockets or a breadboard to find a set of transistors that sounds and works great... selecting transistors only by hfe/leakage readings is a bad idea.

ya I've heard one of the recommendations for I think q3 with zero leakage, I thought it was BS but maybe I'll give it a shot I've got some low leakers I can try. I just thought these circuits basically ran on leakage ( maybe just built to many tbmkII's Anyway thanks for the recommendations, I'll figure it out eventually.

[tacobender]

Yeah, i went through the same thing with mine. I tried following others hfe and leakage specs, but in the end found it easier to just breadboard it. I found swapping transistors and audio probing each stage to be easiest. For me changing bias resistors just complicated matters. I was able to get it working with various leakages and stock values, but just went with what sounded best to me. Another good reason to breadboard is that it can be quite noisy with certain transistors. Both my zonk and mki's attack controls work more like a tuning control and balance the noise to sustain ratio. Not the type of fuzz you just crank to 10, it sounds best somewhere in the middle.

do you happen to remember the nubers you ended up using, hfe and ma?

[Electric Warrior]

The thread on the "other forum" I linked (link got censored, whoops) has hfe and leakage measurements.
But even a quick look at the schematic can tell you a lot. Q1 is a very uncommon type, but Q2 is an OC75 and Q3 an OC44. It's no secret that OC75s are rather leaky (300µA and more is not uncommon), while OC44s usually have very little leakage (often low as 0).

But you really need to use sockets or a breadboard to find a set of transistors that sounds and works great... selecting transistors only by hfe/leakage readings is a bad idea.

ya I've heard one of the recommendations for I think q3 with zero leakage, I thought it was BS but maybe I'll give it a shot I've got some low leakers I can try. I just thought these circuits basically ran on leakage ( maybe just built to many tbmkII's Anyway thanks for the recommendations, I'll figure it out eventually.

Yes, leakage is pretty important for these, but apparently 0 leakage for Q3 can work.
OC71s were also often used for Q3. They usually leak a lot more than OC44s, but HS used the same bias setup - go figure. When they used them for Q2, they mostly came with a 220k between Q2's base and 9V and a 25k fuzz pot.

[tacobender]

So my question is what would be the suggested gain and leakage for a zonk? Is it pretty much like an mk2 or is this a different animal all together? ...Also any transistor recommendations would greatly help. Thanks

It's a mki smaller caps and slightly different valued resistors. I just checked my notes and I ended up with q1=180hfe/.142ma q2=176hfe/.177ma q3=195hfe/.124ma on my zonk machine.

sorry I just read over this thread again. The numbers you listed, were they from an original zonked or form one youve built yourself?

[bms19]

would it be interesting to replace the m and 15K by trimpots?
Cheers
Ben

[bmsiddall]

ya I've heard one of the recommendations for I think q3 with zero leakage, I thought it was BS but maybe I'll give it a shot I've got some low leakers I can try. I just thought these circuits basically ran on leakage ( maybe just built to many tbmkII's Anyway thanks for the recommendations, I'll figure it out eventually.

I've built a couple of mk1s and low leakage russians for q3 get you in the 8v collector ballpark without too much fuss. Q1 on mine gets the highest leakage fwiw.
Cheers, Brett

[iainpunk]

would it be interesting to replace the m and 15K by trimpots?
Cheers
Ben

might be nice, i suggest a 2M trimmer with a 560k series resistor and a 22k trimmer and a 10k series resistor.

cheers

[bms19]

Actually this idea of trimpots there could be use for MK1 and Maestro too, almost indentical PCBs...
I will definitively try that

Ben