Home » Audio » Group Build » Cheap source for R3?
Cheap source for R3? [message #30413] Sat, 05 February 2005 22:12 Go to next message
colinhester is currently offline  colinhester
Messages: 1349
Registered: May 2009
Location: NE Arkansas
Illuminati (3rd Degree)
I've looked around for a good, cheap souce for the rheostat, R3. The closest thing I could come up with is part number (RWV) 200-66HS500 Rheostat, 500 Ohm, 1W, multi-turn, wire wound, inductive element at www.surplussales.com for $5 (see link).

This part is just to dial in the voltage, correct? Will this be replaced with a unique resistor once the value is determined?.....Colin



Re: Cheap source for R3? [message #30414 is a reply to message #30413] Sun, 06 February 2005 05:17 Go to previous messageGo to next message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
Hey-Hey!!!,
One of the 10 or 15 turn cermet trim pots from Mouser is what I suggest. They do not need to be very robust, and are perhaps $2 each.

Mike Percey sells a high performance bulk-foil version. I have not tried this yet, but would buy a few when next ordering from him.

For this sort of small signal work, I prefer to stay away from parts with that much stray inductance( wire-wound=inductive coil ). Stray capacitance is also higher with such designs( I suspect, no absolute confirmation, but it does generally follow ).

Stray stuff is begging to contribute to an oscillator circuit. We are trying to avoid creating an oscillator, remember?
regards,
Douglas

Vishay model 70Y [message #30415 is a reply to message #30413] Sun, 06 February 2005 05:26 Go to previous message
PakProtector is currently offline  PakProtector
Messages: 935
Registered: May 2009
Illuminati (2nd Degree)
It's on the first page of Mouser's trimmer section. on page 417.

500R 1W.

PN 594-70Y501

It's a bit on the 'spensive side, and a 0.5 Watt will do, even a 0.25 will be fine.

right below it are the 20 turn model 434P at ~1/3 the price.
regards,
Douglas

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