Resistor types

[sbirkenstock]

Hi,

just figured out that the type of a resistor (carbon composition, carbon film, metal oxide, wirewound etc) make a huge impact on sound when you use it in the power supply between the filter caps.
Carbon composition sound by far the best, wirewound really "bold" and "stiff", metal oxide kind of in the middle.
Wirewound sounds kind of like a larger choke. Which seems logical...
So the though is, that difference should be there with power tubes cathode bias resistors as well.
But are there any 5 watt rated carbon comp resistors?
Or is it save to use like three 2 watt in parallel?
Like three 1,5K resulting in 500Ohm?
Or even in series?
Like 4 times 120 Ohm?

Best regards,

Stephan

[Stevem]

How did you figure this by trying these resistors out,or just reading about it?

[sbirkenstock]

I tried quite a bunch, also with different values ohm wise.
So where Fender Blackface amps usually have a 4k7, I also tried like 10K and 2.2K.
For all of those values I tried carbon comp, carbon film, metal oxide and wirewound.

[JMFahey]

just figured out that the type of a resistor (carbon composition, carbon film, metal oxide, wirewound etc) make a huge impact on sound when you use it in the power supply between the filter caps.
Carbon composition sound by far the best, wirewound really "bold" and "stiff", metal oxide kind of in the middle.
Wirewound sounds kind of like a larger choke. Which seems logical...

That's the one point in the amplifier where it would have NO influence on amp sound, since there is no audio going through it, and to boot is audio bypassed to ground through 2 large filter caps, one on each end.

So it would reinforce the idea of wishful thinking.

Even more confirmed by the "discovery" that "a wound resistor sounds like a choke" .

Hey!!! , they are both wound ..... they should sound the same, wouldn't they?

It's easy to hear what one's expecting to hear.

[John_P_WI]

I tried quite a bunch, also with different values ohm wise.
So where Fender Blackface amps usually have a 4k7, I also tried like 10K and 2.2K.
For all of those values I tried carbon comp, carbon film, metal oxide and wirewound.

Using different values over the "standard" will have a much greater effect by varying the voltages than resistor type will.

I would highly recommend using flame proof MOX or MF types in the filter cap string.

[RockinRocket]

I thought CC would drift under b+ just like CC placed as plate resistors? Drifting resistor resistance in the B+ rail would change the voltage feed to valves. I could see dropping resistors having an effect because of how stable they are even if the effect is minimal.

[xtian]

just figured out that the type of a resistor (carbon composition, carbon film, metal oxide, wirewound etc) make a huge impact on sound when you use it in the power supply between the filter caps.

Wow. You seem like you'd really appreciate what Monster cable can do for your sound!

[pdf64]

just figured out that the type of a resistor (carbon composition, carbon film, metal oxide, wirewound etc) make a huge impact on sound when you use it in the power supply between the filter caps

Consider that if a change has a huge impact on the sound, it should be measurable somehow; when viewed on a scope relevant waveforms should reflect such a change.

I thought CC would drift under b+ just like CC placed as plate resistors? Drifting resistor resistance in the B+ rail would change the voltage feed to valves. I could see dropping resistors having an effect because of how stable they are even if the effect is minimal.

I think that the CC effect on plate resistors is that their resistance is modulated by large ac when superimposed on large dc, the effect being to add a tiny amount of even harmonics to large signals.
As a HT dropper, that would mean that the ac ripple across the dropper would have some even harmonics added to it.
However, as both ends of the dropper are decoupled (perhaps imperfectly) to 0V, and HT hum is usually pretty low anyway, how much of an effect could it have?

[David Root]

CC resistors handle surge voltages better than most other construction. That is why some hifi guys like them as screen resistors.

Personally I wouldn't use them as droppers in a power supply. Fender did and usually underrated them too. I had a '62 Deluxe that I bought with the 1k 2W dropper that eventually cracked and then failed because of heatstroke.

As to tonal differences in a power supply, I'd have to see some hard evidence of that....now if you're talking about tube rectifiers, that's a different matter IMO.

[John_P_WI]

CC resistors handle surge voltages better than most other construction. That is why some hifi guys like them as screen resistors.

We frequently use 10k 1 watt CC in the medical field as front end defib protection for that very reason. Hitting them with a 500 joule / 5000 volt pulse will vary the resistance wildly - even after they cool down. Humidity in the lab is a killer makes them pop like a 22 cal rifle. It is getting harder and harder to find quality CC these days.

[TUBEDUDE]

As I recall, most low wattage wirewounds have 2 countervailing wraps to eliminate the Inductive reactance, so they should be mostly resistive and less coil like.