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Resistor Choice Stereo/Mono Switch?
Resistor Choice Stereo/Mono Switch?
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Old 16th April 2019, 10:46 PM   #11
WntrMute2 is offline WntrMute2  United States
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Thanks to both of you for your help. I have a bunch of what I believe are carbon comp resistors - they have squared off ends on the cylinders. They look similar in form to ones I know are CC. Is that a defining feature of CC resistors? Also I have some carbon film ones in the same value.

The input load for the Cary SLP-98 line stage is 50,000 ohms.

I'll also fire off another email to GlassWare. Thanks for all the help!
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Old 16th April 2019, 11:48 PM   #12
JMFahey is offline JMFahey  Argentina
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Still donīt know the circuit schematic but guessing the MONO position links both Op Amp outputs together and amplifier has 50k input impedance, an excellent compromise is using 2 x 4k7 resistors.

Carbon or metal film wonīt make a huge (or audible) difference here so use what you have or flip a coin.

Edit: forget carbon comp for any Audio use, itīs dated Technology in a bad way.

A carbon or metal film deposited on a ceramic substrate is WAY more stable and precise than ground graphite mixed with bakelite and clay and cooked in an oven.
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Last edited by JMFahey; 16th April 2019 at 11:51 PM.
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Old 17th April 2019, 09:49 AM   #13
DF96 is online now DF96  England
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Yes, don't use carbon comp. When I said that type does not matter too much I meant you could choose any decent resistor type - not CC! A few hundred ohms will be about right; it is only there to avoid damaging a poorly-designed preamp.
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Old 17th April 2019, 11:04 AM   #14
avtech23 is offline avtech23  Australia
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Resistor Choice Stereo/Mono Switch?
The ones installed on the image appear to be Brown-Black-Black-Red-Brown so 10k 1%?

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Quote:
A rotary switch for phono playback that presents three positions: mono, mute, and stereo.
In Mute, the switch is open circuit Lin//Lout & Rin//Rout
In Stereo, the switch is closed Lin=Lout & Rin=Rout
In Mono, the resistors are connected Lin=R1=Lout=Rout=R1=Rin
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Old 18th April 2019, 03:01 AM   #15
PRR is offline PRR  United States
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> so 10k 1%?

I can't read those things.

But assuming 10k, and 50k amps, in Mono the signal level drops 1.6dB. Enough to notice. I would tend to a smaller value.

I've used hundreds of Carbon Composition over the decades (from when there was no choice at the local shop) and with 99% satisfaction. Yes, had a couple go drifty, once very educational. However since Carbon Film arrived I have had NO trouble of any sort.

In this case I don't think Composition would be "wrong". The small increase of hiss is swamped by other impedances, and would only happen in Mono. 20% drift would be small mix-shift, and might not happen for decades (I have seen 90% drift in 20 years but that was a very hot chassis).
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Old 19th April 2019, 12:18 AM   #16
Mark Tillotson is offline Mark Tillotson
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Most opamps can drive 2k without struggling and rising distortion, so two 2k2 resistors sounds about right, and is low enough to keep noise under reasonable control.
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