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DIY Stompboxes => Building your own stompbox => Topic started by: bmsiddall on June 10, 2021, 04:37:55 AM

Title: Roland AD-50 - GERMANIUM!
Post by: bmsiddall on June 10, 2021, 04:37:55 AM
Umm, not yet.   8)

While I was getting lost playing the silicon version tonight, it popped into my head that maybe this might be worth pursuing?  I have a shit-tonne* of low-medium gain NPN germanium, and I don't think the circuit requires particularly gainy transistors.  So, thought I'd check in here to see if the resident gurus had any suggestions for biasing? 

(https://i.postimg.cc/QVCnWP9z/AD50.png) (https://postimg.cc/QVCnWP9z)

*metric
Title: Re: Roland AD-50 - GERMANIUM!
Post by: iainpunk on June 10, 2021, 12:14:21 PM
i'd say measure the collector voltages you have now and try to match those with Ge's
i kinda doubt Ge's will improve this fuzz because of the character of this beast. (i only played a clone without that tone switch circuit, but it was perfectly gnarly)

cheers, Iain
Title: Re: Roland AD-50 - GERMANIUM!
Post by: bmsiddall on June 10, 2021, 09:59:18 PM
Thx Iain.  I have my doubts it'll make too much difference as well, but what the hell, can't hurt to try! 

I'm assuming i just need to adjust collector resistors, not emitter or B-C feedback resistors?

Cheers,
Brett
Title: Re: Roland AD-50 - GERMANIUM!
Post by: Mark Hammer on June 11, 2021, 07:50:10 AM
i'd say measure the collector voltages you have now and try to match those with Ge's
i kinda doubt Ge's will improve this fuzz because of the character of this beast. (i only played a clone without that tone switch circuit, but it was perfectly gnarly)

cheers, Iain
The tone switch is essentially 3 different filters.  Much of that can be mimicked by sticking an EQ after the basic fuzz circuit.  I've added three more, two of them being additional clipping and crossover distortion.  There's nothing magical about 3 or 6.  I went with 6 because a 2P6DT rotary switch made it easy and possible.
https://www.youtube.com/watch?v=xoZ6v-ZXcuU
Title: Re: Roland AD-50 - GERMANIUM!
Post by: PRR on June 11, 2021, 02:52:27 PM
I think you will have real trouble biasing Q1 Q2 to such low current in Ge. Unless you get the very last USSR military select low-low-leakage. Try it, but don't pour concrete around the transistors; you may in the end decide Silicon is better here.
Title: Re: Roland AD-50 - GERMANIUM!
Post by: bmsiddall on June 11, 2021, 05:09:33 PM
Ok, thanks Paul.  I have some gt311 transistors which measure 0 on the Peak.  Never found a use for them in “classic” circuits so I’ll see how they go.