[sdiy] Transistor help

[Tim Parkhurst]

Hi Rob,

In an expo converter for a VCO, a mismatch in the transistors will often
result in a frequency (pitch) error. This will really stand out if you are
trying to get several VCOs to track together. The same errors in the expo
converter for a VCF or VCA will not be as noticeable. 



Tim (mismatched) Servo

"Imagination is more important than knowledge." - Albert Einstein




> -----Original Message-----
> From: Rob Keeble [mailto:rob at emulatorarchive.com]
> Sent: Wednesday, April 27, 2005 2:33 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Transistor help
> 
> 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.
> 
> 
> 
> 
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