Vishay vt52-55 resistors in a tube amp

[jarthel]

Has anyone used these resistors in their project? feedback please.

thank you

[Johan Potgieter]

Hi Jarthel,

Advice partly. I have never used them; as far as I know they are quite expensive. I have however done a number of amplifiers over decades, and my advice would be that the "extra" quality is not wothwhile in audio amplifiers. The metal film or metal oxide resistors available these days are more than adequite - as are polyester or poly-carbonate capacitors!

There appears to be some snob value in the use of exotic parts, but unless you really want to keep up with the Wavevacs (and then mount your amplifier on a mirror so that "exotic" can at least have some face value), don't waste your money where it does not count. Reports of "sound better"? Not to step on any toes, or at least doing my best to miss them where they sometimes are placed squarely in my way, but almost anything will sound one way or another to many people.

Regards

[Conrad Hoffman]

Haven't looked up that p/n, but if they're bulk metal foil resistors, they're about as good as one can get in terms of linearity and noise. I really question anyone's ability to tell the difference between different manufacturers versions of the same technology resistors. IMO, standard metal film resistors are quite sufficient for my ears, and I'd never waste money on anything better than that for audio work. For lab voltage and frequency standards, yes, as you could measure a difference. My experience with MOX and thick film resistors suggests they aren't a good choice for audio. Too much voltage non-linearity with the MOX- I made the mistake of using them in a HV amps feedback circuit, and performance suffered greatly. I've also used thick film resistors in sensitive low level amplifiers, and had excess noise. Plain old metal films solved both problems, but be sure to observe both the power and *voltage* rating, especially in a tube amp. Many 1/4W 1% MF resistors have a 300V rating, regardless of how little power you happen to be dissipating. I like the larger RN70 series resistors in tube amps.

[Johan Potgieter]

Most interesting, Conrad!

Thanks for the input on mox. I do use then for the first time in a 100W tube amp because of watt rating vs size, but will inspect immediately - they get quite hot, though within rating. Again, down here for over 2W one mainly gets huge ugly 5W wws. With regard to normal metal-film I can agree with you. I have used them in lab equipment as well as in a 150 MHz super-sensitive receiver.

Your experience regarding thick-film is also valuable - thanks for warning. How many modern equipment uses them? I shudder.

Regards