2k Tempco advice

[ejr27233]

I'm about to build 2 Buchla 258ish VCO's and need 2k Tempco's.
I've got 1k ones so the options are....

a, Put 2 1k tempco's in series
b. Put a 1k tempco and a 1k 1% metal film resistor in series.

or at a push
c, Order 2k tempco's from USA (not keen to do)

Which is the best option???

Any advice greatfully recieved

[Sebo]

I think that two 1K tempcos in series will work OK. The x0xbox uses two 1K tempcos in series.
1K tempco + 1K metal film will not work for sure, as the temperature coeficient will be a lot lower than needed.

[ejr27233]

Thanks for your help

Regards

John

[L´Andratté]

Funny, I have the same question-
Since those tempcos are not really cheap, wouldn´t it be possible to just lower the input resistors from 100 to 47k (same relation gain 1/50)?
I´ll try it...

[rogerlatur]

[L´Andratté]

Yes and no...

I did build it and it gave exponential response and mediocre scaling was there, but not optimal, maybe due to other things? I don´t know, I guess the problem with the 47k is about the input impedance, maybe there´s some tiny voltage loss?

The difficulty might be the same cv would give different notes from different osc.s! {EDIT: check next post}

Sorry I´m only autodidactic halfwit

Good reading:

*** ELECTRONOTES S019:scroll down here
http://electronotes.netfirms.com/free.htm

***http://www.uni-bonn.de/~uzs159/index.html

***first article under
"Projects and Misc Files"

http://home.comcast.net/~ijfritz/misc_lnk.htm

[L´Andratté]

Check especially the 2nd link halfway down, it´s there!
54k:1k at 1% tolerance!