[sdiy] germanium transistors

[Tom Wiltshire]

On 21 Jan 2009, at 00:08, Antti Huovilainen wrote:

> On Tue, 20 Jan 2009, Tom Wiltshire wrote:
>
>> I wasn't suggesting that you don't test the transistors. I tested  
>> all mine for gain and leakage. Then I built the circuit, with a  
>> socket. Then I took the mostly likely candidates from the testing  
>> and tried them until I found one that had a sound I liked.
>
> Were there significant differences in sound as long as the gains  
> were in range and average gain was close to 100?
> I didn't get enough good germaniums out of the batch to do any kind  
> of real comparison and I don't have the pedal anymore.

For the Rangemaster, the recommended gain is between 75-100  
(R.G.Keen's Austin Treble Blaster clone). From a batch of ten, I  
think I had three good candidates. The asymmetric biasing is also a  
big part of the sound (it's only a single transistor circuit so  
*everything* makes a difference!) and I found I needed to tweak the  
biasing for each different transistor to get the best out of it. I  
was surprised at the time how variable they were - there definitely  
were clear differences. I guess I've got used to modern components  
with 1% tolerances, and that's a million miles from the "3 out of 10"  
world of germanium mojo!

T.