Hi.
Does anybody know which kind of resistor to choose for setting the input impedance
in a mc stage for the least noise?🙂
Does anybody know which kind of resistor to choose for setting the input impedance
in a mc stage for the least noise?🙂
metal resistors.
not metalised.
There is some disagreement on thin film and thick film, could this be down to the metal type?
not metalised.
There is some disagreement on thin film and thick film, could this be down to the metal type?
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?
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.
Last edited:
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.
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.
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??🙂
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??🙂
Attachments
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.
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.🙂
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
I have to admit I've stared at it a bit and can't convince myself that it can work, nor that it can't!
Conrad: How could you possibly know that it works (or doesn't) if you don't know what it is supposed to do! E
the photodiodes will be supplying a order of magnitude or two too little supply current for good noise performance at the indicated low source Z
🙂It is a mc headamp build on Marshall Leach principle and with optical powersupply.
It works perfectly well by the way, and has been used in several versions since the mid 80s. sounds pretty good too🙂
It works perfectly well by the way, and has been used in several versions since the mid 80s. sounds pretty good too🙂
😀Right now i am planing some experiments of using infrared led`s instead of lightbulbs to avoid the light coming out of all the openings of the cabinet.
If there is no DC current flowing through the resistor, it doesn't matter for the noise floor what resistor type you use. You could use a seventy-year-old carbon composite resistor and get the exact same noise floor as with a brand new wire wound resistor of the same value.
Theoretically the carbon composite resistor could create noise sidebands around the desired signal though, so that might be a reason to go for metal film or wirewound anyway, although I doubt if this effect will be measurable or audible.
Theoretically the carbon composite resistor could create noise sidebands around the desired signal though, so that might be a reason to go for metal film or wirewound anyway, although I doubt if this effect will be measurable or audible.
MarcelvdG, did you read the resistor measurements in Linear Audio #1? They sure have measurably different noise floors with a 1 kHz signal on them.
Not really, they have very different noise skirts around the 1 kHz signal but all noise floors are around -176 dB.
Each resistor under test was subjected to a 7.905 V RMS signal. That is some four decades above the signal level from a moving coil cartridge. I wonder if you still could measure anything with the tiny moving-coil signal levels, even when you use a very low noise moving-coil preamplifier.
- Status
- Not open for further replies.