[sdiy] Transistor help

[Kevin Lightner]

>Hi,
>Whats the point of matching transistors (in expo converters and ladders),
>beyond 2mV?
>Is there really a sonic difference? Do we need expensive 0.5mV matched
>arrays or just transistors from the same batch?
>
>Emperors new clothes? Or State of the Art?
>
>An E-mu Systems Resonant Filter I have recreated sounds better with
>unmatched 2N3906's rather than a dual transistor pair (as per the
>original).. any thoughts guys?
>
>Regards
>Rob
>www.emulatorarchive.com
>
>
>One thing I have noted about modern batches of transistors is they sure
>seem to be all very similar...I generally match about 10 pairs at a
>time...out of 20 transistors (generally 2n3906) I always get 10 pairs...and
>all of the transistors are within about 2mV of each other....30 years
>ago...it wasn't like that...as I recall.


I'm curious how the two were A/B'd unless you made duplicate filters. :)

However, transistor matching, in my opinion, is blown out of proportion.
I'm not sure most people can hear a filter and say it sounds like the 
transistors are unmatched or whatever. I've also built Moog filters 
with completely unmatched transistors, even from different makers and 
they sounded great.

It's funny about all the rumors out there in regards to matching too.
For example, there's a rumor that only the early RA and Musonics 
Minis used matched transistors in their ladders.
I have 11 (count 'em!) Minis in and they ALL have a colored dot on 
their transistors, which the other same numbered transistors don't 
have. The reason, often overlooked, about the very early Minis is 
that their electrolytic caps are older and of different values when 
new anyways.
400uf, instead of the later 470. 80uf instead of 100uf and so on.
Their carbon resistors are often *way* off too.
I often measure the 820 ohm resistors at 1K-1.2K.


-- 
Regards,
Kevin Lightner

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