low noise resistors

pdul · 15th October 2011, 08:44 AM

Hi.
Does anybody know which kind of resistor to choose for setting the input impedance
in a mc stage for the least noise?

AndrewT · 15th October 2011, 09:29 AM

metal resistors.
not metalised.

There is some disagreement on thin film and thick film, could this be down to the metal type?

pdul · 15th October 2011, 03:33 PM

Do you have a specifik example of which brand/type of metal resistors, since i have the impression that all of it is just called metalfilm?

pdul · 15th October 2011, 03:35 PM

What about the MRS25 or Dale RN55/60?

indianajo · 04:55 PM

If you can get Dale RN55 or 65, great. I have some from Radio Shack grab bags of the seventies. Work fine in my Hammond organ amp but not audible since in the central power supply. New ones come in hundreds at a good price, at least at newark.com and mouser.com. I used newark multicomp and vishay metal film resistors to replace the carbon comp high value (100k up) resistors in my PAS2 and ST70 tube equpment. Much less hiss. Versus another brand of metal film, I have no idea. Both brands were made in India. I use 2 or 3 watt resistors in tube equipment, as 1/4 watt and 1/2 watt metal film resistors are too short to hold off 425 V. Look for the voltage rating on the table at newark- or farnell in europe.

asbjbo · 15th October 2011, 05:00 PM

You can find the basics here:
Resistor Types--Does It Matter?
Strategies for minimizing resistor-generated noise

There is also an interesting article in Linear Audio vol. 1 about resistor noise and distortion. The benchmark is Dale RN65E S102 25PPM milspec.

pdul · 15th October 2011, 07:18 PM

I guess that i can conclude from all your information that what i need is
wirewound with the smallest physical size for the least noise at the input
of this mc stage, since the induction of the resistor will be neglectable together with that of the pickup, and at values from 40-100 ohm.
Did i get it right or??

Conrad Hoffman · 15th October 2011, 07:49 PM

Resistor generated noise isn't much of an issue with most audio circuits, but mic preamps are where it may matter. Metal films are usually adequate. Wire-wounds, even the "non-inductive" ones, aren't as non-inductive as one might hope. If the slight inductance and potential pickup from the large size doesn't give a problem, they're a good choice. The best of all worlds is the bulk metal film, having low inductance and small size. IMO, that link has some marketing included, but if you can afford 'em, the bulk metals are the way to go. You can also get them in larger values, whereas the wire-wound resistors are typically available in lower values; the wire gets too fine or the size gets too large to make them in high values.

pdul · 15th October 2011, 08:12 PM

Conclusion est!
I will stick to my Vishay MRS 25 metalfilms of which i have plenty in the right values.
But anyway thanks to all you guys for enlightning me about the obviosly not so simple world of resistors.

mickeymoose · 15th October 2011, 10:31 PM

Generally I am not that slow....but I really can not figure what that circuit in post #7 is supposed to do. So, please enlighten me. Thanks, E

15th October 2011, 08:44 AM	#1
pdul diyAudio Member Join Date: Jan 2009	low noise resistors Hi. Does anybody know which kind of resistor to choose for setting the input impedance in a mc stage for the least noise?

15th October 2011, 09:29 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	metal resistors. not metalised. There is some disagreement on thin film and thick film, could this be down to the metal type? __________________ regards Andrew T.

15th October 2011, 04:41 PM	#5
indianajo diyAudio Member Join Date: Jan 2010 Location: Jeffersonville, Indiana USA	If you can get Dale RN55 or 65, great. I have some from Radio Shack grab bags of the seventies. Work fine in my Hammond organ amp but not audible since in the central power supply. New ones come in hundreds at a good price, at least at newark.com and mouser.com. I used newark multicomp and vishay metal film resistors to replace the carbon comp high value (100k up) resistors in my PAS2 and ST70 tube equpment. Much less hiss. Versus another brand of metal film, I have no idea. Both brands were made in India. I use 2 or 3 watt resistors in tube equipment, as 1/4 watt and 1/2 watt metal film resistors are too short to hold off 425 V. Look for the voltage rating on the table at newark- or farnell in europe. __________________ Dynakit ST70, ST120, PAS2,Hammond H182(2 ea),H112,A100,10-82TC,Peavey CS800S,SP2-XT's, T-300 HF Projs, Steinway console, Herald RA88a mixer, Wurlitzer 4500 Last edited by indianajo; 15th October 2011 at 04:55 PM.

15th October 2011, 07:49 PM	#8
Conrad Hoffman diyAudio Member Join Date: Mar 2007 Location: Canandaigua, NY USA	Resistor generated noise isn't much of an issue with most audio circuits, but mic preamps are where it may matter. Metal films are usually adequate. Wire-wounds, even the "non-inductive" ones, aren't as non-inductive as one might hope. If the slight inductance and potential pickup from the large size doesn't give a problem, they're a good choice. The best of all worlds is the bulk metal film, having low inductance and small size. IMO, that link has some marketing included, but if you can afford 'em, the bulk metals are the way to go. You can also get them in larger values, whereas the wire-wound resistors are typically available in lower values; the wire gets too fine or the size gets too large to make them in high values. __________________ I used to be an audiophool like you but then I took an arrow to the knee.

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15th October 2011, 03:33 PM	#3
pdul diyAudio Member Join Date: Jan 2009	Do you have a specifik example of which brand/type of metal resistors, since i have the impression that all of it is just called metalfilm?

15th October 2011, 03:35 PM	#4
pdul diyAudio Member Join Date: Jan 2009	What about the MRS25 or Dale RN55/60?

15th October 2011, 05:00 PM	#6
asbjbo diyAudio Member Join Date: Dec 2009 Location: Oslo	You can find the basics here: Resistor Types--Does It Matter? Strategies for minimizing resistor-generated noise There is also an interesting article in Linear Audio vol. 1 about resistor noise and distortion. The benchmark is Dale RN65E S102 25PPM milspec.

15th October 2011, 08:12 PM	#9
pdul diyAudio Member Join Date: Jan 2009	Conclusion est! I will stick to my Vishay MRS 25 metalfilms of which i have plenty in the right values. But anyway thanks to all you guys for enlightning me about the obviosly not so simple world of resistors.

15th October 2011, 10:31 PM	#10
mickeymoose diyAudio Member Join Date: Nov 2008	Generally I am not that slow....but I really can not figure what that circuit in post #7 is supposed to do. So, please enlighten me. Thanks, E

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