so I just picked up a used wyred for sound preamp, and the mfg offers an upgrade of 24 Vishay z-foil resistors. so I say to myself, I'm a DIYer, I can do this myself.
but then.... digikey sells them, for something like $20 EACH. $20 for 1 resistor. this is digikey, not some boutique high end audio store.
I've never heard of anything so outrageous. (except prices for boutique cables)
but then.... digikey sells them, for something like $20 EACH. $20 for 1 resistor. this is digikey, not some boutique high end audio store.
I've never heard of anything so outrageous. (except prices for boutique cables)
I stopped using thjem when I found out they have a large voltage coefficient at low frequencies, which drives up LF distortion.
Not worth the price.
Jan
Not worth the price.
Jan
Could you share a bit mode detail please. The published VC<3ppm/V is for HF but not for LF?
Not sure what I am allowed to share. The low specified Tc comes from a substrate that has the same thermal expansion and contraction coefficient as the resistive body. But the masses of the substrate and the resistive body are not the same thermal contraction/expansion gets out of step with the resistive body at some freq range.
I've measured it for a project I consulted on. Can't give any details but it might be worthwhile to look into it.
Jan
I've measured it for a project I consulted on. Can't give any details but it might be worthwhile to look into it.
Jan
You can also buy them from Texas Components. They can make any value. About the same price but they have/make what you want in whatever tolerance.
https://www.texascomponents.com/store/bmfaudioresistors.asp
https://www.texascomponents.com/store/bmfaudioresistors.asp
If precision wirewound is ok you could try the General Resistance GG102, aka Rhopoint. 24 would probably get over the minimum order at the manufacturer Prime Technology primetechnology.com
These seem really solid if you don't need really low tcr. What would be the price? There is only inquiry information.
It depends on what you want, but well under USD20. I did a one-off GB a while ago, Prine was nice to deal with: https://www.diyaudio.com/community/...-gb-general-resistance-rhopoint-gg102.368746/
I had no idea that these existed. I haven't cracked open the preamp yet, so I don't know how accessible they will be or even if they are through hole or smd.
here's what the mfg says about their stage 1 upgrade ($850)
their stage 2 ($1750)
here's what the mfg says about their stage 1 upgrade ($850)
their stage 2 ($1750)
The voltage coefficient issue was brought up in a presentation by Audio Precision some years ago. As I remember, they were a bit vague about it, but it's definitely measurable.
I looked at their website regarding the upgrades, the pictures show through hole parts. If it was my preamp, I'd install the inductors, diodes and "high frequency filter capacitors" and pass on the z-foil.
I would not want to mess with the ladder volume control, it already is better than most of my preamps.
Then again, I'd just listen to it.
You bought a very nice preamp!
You need a high resolving system to get the best out of the foils.audio chain only as good as weakest link.enjoy.
I agree.
They are made for use in test instruments for UHF TV and radio all the way up to satellite frequency.
I have seen there wire wound counterparts in very old RF test instruments. They have a special non inductive wind.
It is all do do with the shape of the resistant element being non inductive at hundreds of megahertz and gigahertz.
For audio it is down to wallet thinning therapy as they do not pay for themselves if used below 500Mhz.
Wait until you find out about the Vishay Precision Group metal foil potentiometers...
https://www.digikey.com/en/products...ishay-precision-group/Y005610K0000K0L/2609880
https://www.digikey.com/en/products...ishay-precision-group/Y005610K0000K0L/2609880