Good Power Resistores ???

[geladk]

Hi.

For the first time I’m going to build a tube preamp (ARC LS7 clone) and a tube power amp (ARC VT60 clone), and I intent to use top quality components.
I have no experience with sound quality and stability of power resistors (>0.5W) suitable for my project.

Can you recommend some types and marks?
Should I use deferent types of resistors depending on application in the circuit?

Thanks.

[Rod Coleman]

For 3W to 14W (more power with parallel pairs), try Vitreous Enamel wirewound. Welwyn W21, W22, W23 & W24 are a good series. These are used by designer Tim de Paravicini, in the EAR professional product range - in anode and cathode circuit positions.

Also, they are not expensive, so you can buy a few and try the sound for yourself! Be sure to run them at only 1/2 or 1/3 of the rated power, to get good sound.

Produktsøgning | Farnell Danmark

[tomchr]

Dav,

I haven't noticed any difference between brands in terms of sound quality. However, note that power resistors are designed to run HOT. As in 250 deg C at max power dissipation. To me, that's too hot for comfort so I tend to run power resistors at somewhere around 1/5~1/3 of their max rating. That keeps them to 65~100 deg C with 20 C ambient.

I tend to default to Vishay-Dale as they're usually the least expensive. I haven't had any issues with drift, but I haven't run an accelerated life-time test either... In my recent power supply design, the voltages were within 0.1 % of their initial value even after a couple of hours of burn-in. The output voltage was linearly dependent on the resistance of a 5 W power resistor (classic LM317-based "Maida regulator").

I'm sure Vejle RC Elektronik and/or Aarhus Radio Lager will be able to help you out with mail order parts if you don't have a local electronic components pusher.

~Tom

[geladk]

Hi.

Thank you both for the information :-)
I will look into Welwyn and Vishay-Dale.