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-   -   Importance of quality resistors ????? (http://www.diyaudio.com/forums/analog-line-level/132067-importance-quality-resistors.html)

Serratoga 27th October 2008 11:52 AM

Importance of quality resistors ?????
 
Hi Everyone, I need some advice. I will be changing the load impedance of my phono stage.
Presently it is set up for 47K ohm, I think they come like that from the manufacturer. My
phono stage is an Audio Research PH3SE and my cartridge is a Micro benz MC M2 on a Clearaudio Unifty 9 arm. Now my question is how important is it to use
high quality resistors? Does the audio pass through that section of the phono stage?

Thanks

jackinnj 27th October 2008 12:55 PM

The load resistor is in parallel with the preamplifier phono-stage. In your case, Benz recommends (from what I am able to determine) 200 to 47,000 ohms, so the noise of a 200 - 47k ohm resistors itself range from 1.8nV to 27nV per root Hz, but this is shunted by the internal resistance/impedance of the MC itself.

I would use the lowest value possible consistent with the front-end design. You may have to experiment a bit to get it right.

read this nice article by Marshall Leach:
http://users.ece.gatech.edu/~mleach/headamp/

Conrad Hoffman 27th October 2008 12:56 PM

Whether the audio signal "passes through" or is shunted to ground makes no difference. The components are still in the signal path and affect the sound. Now, some claim to hear differences between resistor types, usually preferring the more expensive ones, but once you get to any decent 1% metal film part, I can't tell 'em apart in most applications. I certainly wouldn't use a carbon composition, carbon film, thick film or MOX resistor for a cartridge load.

Serratoga 27th October 2008 02:26 PM

Thanks guys, what is the minimum required wattage , I could use? I was looking at some
Vishay and they're rated at very low wattage.....

Thanks

coloradosound 27th October 2008 02:42 PM

I agree with Conrad. Whether in series or parallel, passives
are carrying the signal either to the next stage or to ground.
When a component is modulated the effect of the modualtion
is carried to the next stage or the inverse of the modualtion
in the case of shunting. i.e. if distortion is created when
a signal is shunted to ground that distortion shows up being
sent to the next stage as inverted distortion.

kevinkr 27th October 2008 04:45 PM

Quote:

Originally posted by Serratoga
Thanks guys, what is the minimum required wattage , I could use? I was looking at some
Vishay and they're rated at very low wattage.....

Thanks

The Vishays would be fine regardless of their low wattage rating. You are probably talking about a few uW of dissipation at most.

Serratoga 27th October 2008 05:04 PM

Thank You,
I had the Vishay metal film resistors in mind and the Caddock MK 132 precision metal film.
Has anyone tested either one? Any preferences?

Thanks

jackinnj 27th October 2008 05:10 PM

Quote:

Originally posted by Serratoga
Thank You,
I had the Vishay metal film resistors in mind and the Caddock MK 132 precision metal film.
Has anyone tested either one? Any preferences?

Thanks

CMF55 or RN55 -- these are readily available from Mouser --

Serratoga 27th October 2008 06:02 PM

Hi Jack,
I checked out the Mouser site, not that I would no the difference, why the CMF 55 and not the higher power rated CMF 60 ?

Thanks

jackinnj 28th October 2008 01:12 PM

They just happen to be what I order -- I think that quite a few people have used them in their F5 amplifiers :)


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