[sdiy] TR909 / capacitance values question

[Trevor Page]

Hi all,

A concern I have always had with my TR909 clone project is the availability
of certain capacitor values used in most drum circuits. Examples of these
values are 18nF, 27nF, 56nF, 82nF and so on.

Personally I have no trouble obtaining these capacitor values, and I expect
most people constructing my project wouldn't have difficulty getting hold of
them either. My concern is that many electronics suppliers only carry a
basic range of capacitors, those being the common 10, 15, 22, 33 etc. (E6?)
Here in the UK, suppliers like Rapid don't stock all of the values I need,
but I can get them from Farnell. But I know that not everyone would have
access to such a supplier. So what I would like to know is, would anybody
anywhere experience difficulty in getting the above values? Such as 8.2nF,
12nF, 27nF, 56nF and so on? (I guess we'd call this the E12 range, right?
:o)

I have found that it is relatively easy, by altering resistances, to modify
the drum circuits so that only 'common' capacitance values are used
throughout whilst leaving the overall sound of the drum circuit unchanged.
Anyone bulding the project would have the choice of using the original
values, or using the 'alternative' ones which are easier to get hold of
[for example, the 8.2nF in the hitom can be replaced with a 10nF, and a 47K
resistor replaced with 39K to compensate].

Is it worth me doing this for the entire design? I can't be bothered doing
it if nobody finds it difficult to get these parts, but if it could save
even one person a lot of aggro, then it's worth doing it.

Any feedback is much appreciated - reply privately if you like.

Kind regards,

Trevor.

PS thanks to those who responded re. PCB manufacture costs, and applogies
for not having replied to all of you personally. All I wanted was a vague
idea how manufacturing charges varied etc.




--
trevor at resonance.fsnet.co.uk

---> TR909 clone project  <---
www.resonance.fsnet.co.uk/drummachine.html