Pitfalls of paralleling different resistor brands? - diyAudio
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Old 5th March 2011, 01:24 AM   #1
phrarod is offline phrarod  United States
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Default Pitfalls of paralleling different resistor brands?

So here's my story. I have naked resistors for cathode bias. Lowest noise, incredibly clear, but can tend to the lean side. My favorites for tone are Roederstein. But those alone don't have the transparency I'm after. So for a while I paralleled them calculating the resistance of the Roederstein so it wouldn't change the overall resistance.

I just finished the project and decided to listen with just the naked resistors. Clearer, cleaner, more transparent. Moved to the leaner side.

So my question is: am I just injecting noise by paralleling these trying for the best of both worlds? I've tried just about every resistor in this position. Since I have an incredibly simple circuit the tube bias is the only place I have R/C in the signal path so the R or the C make a huge shift in the sound.
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Old 5th March 2011, 01:31 AM   #2
RTF671 is offline RTF671  United States
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By paralleling them you can only inject max of half the noise because a split is a current divider (if the resistances are equal). I have heard of people doing that before to add some tone in their signal path.

What kind of amp and how many positions are you thinking of doing it to?
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Old 5th March 2011, 01:38 AM   #3
phrarod is offline phrarod  United States
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They are not equal values. The Naked is 221R and the Roederstein is 91K = 220.46R

This is a pre-amp. Just in the cathode bias.
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Old 5th March 2011, 01:46 AM   #4
RTF671 is offline RTF671  United States
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Give it a whirl? See how it goes, thats the best way to find out.
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Old 5th March 2011, 01:47 AM   #5
phrarod is offline phrarod  United States
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You need to read the post again. I have been running that way. I just pulled it today. Pluses and minuses.
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Old 5th March 2011, 02:27 AM   #6
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By blending multiple types of resistors, you will get a blend of all their best attributes. You will also get a blend of all their worst attributes. That means you will end up with some of the leanness and lack of tone you dislike from the Nakeds, and some of the noise and loss of transparency you've heard in the Roederstein. As you say, pluses and minuses. The choice is up to you.
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Old 5th March 2011, 03:22 AM   #7
RTF671 is offline RTF671  United States
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I'm sorry, I missed that part. But yes each one will color the amount of current running through it.

On the upside, if the only thing you have to worry about is brands and flavors of your resistors your amp must sound great
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Old 5th March 2011, 10:26 AM   #8
DF96 is offline DF96  England
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Having 221R in parallel with 91K means that the 91K only contributes 0.24% of whatever happens i.e. it can only have virtually no effect. It could be very noisy or very non-linear and you probably would not notice. If it was a perfect resistor then it would have almost no effect in 'correcting' the 221R. Maybe I have missed something, but such a combination seems totally pointless.
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Old 5th March 2011, 03:40 PM   #9
phrarod is offline phrarod  United States
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DF96 -- This is the part of theory that meets audio reality. Many things make no sense yet have sonic effects. The 91K definitely adds some body and loses some transparency. The explanations is what I was after. The fact its only contributing .24% makes it not so parasitic in my understanding.


RTF -- thanks also, the preamp does sound amazing to me and I've had many classic and expensive ones (which price doesn't result in quality) come through here by way of others and I've owned some good ones.

Much appreciated to everyone.
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Old 5th March 2011, 03:42 PM   #10
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If it can't be measured or theoretically explained, it is a part of audio fantasy, not audio reality. Better to keep these two apart.

Greetings,
Andreas
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