RN65 metal films are they really that much beter ?

[chopstuck]

I ordered a few for my D-lite and noticed some people like them for plate loads. Are they really all that special or is it a taste thing ?

[collinsamps]

Are you asking if a precision RN metal film offers better tone than a standard metal film? If so I vote no. Metal to CC, CF etc is another story for plate load resistors.

[jaysg]

Are they really all that special or is it a taste thing ?

It's always a taste thing. You'll definitely hear the difference...which is remarkable in a way.

[chopstuck]

If that's the only reason, maybe it isn't as important as I thought. I have been using MF for plate loads and input resistors for a while now. I'm even finishing off a couple amps with MF just about everywhere. I don't know what to expect. BTW I tried your idea, ( I think it was you) of building a 5e5 pro with a 5B5 power supply. It was an easy job converting my stock Santa Ana 5e5 to cathode bias and it really helped it. I'm not a big fan of the old P15N's I have. A bit raspy for my liking. I made a reducer ring and put an old 12 in there.

[collinsamps]

I remember that post, it was a 5E5-A using the 5E5 cathode biased power stage that I recommended.

As far as resistors go, I always use metal oxide for power droppers, carbon comps in some signal path areas, and metal film everywhere else.

[Bob-I]

I ordered a few for my D-lite and noticed some people like them for plate loads. Are they really all that special or is it a taste thing ?

The most dramatic improvement I heard in a Dumble like amp was changing the plate loads from carbon film to RN65s.

Of course it's all a matter of taste, try it and see what you think.

[collinsamps]

If you think about signal flow, plate load resistors have little if anything to do with signal developement. The AC component will always take the path of least resistance which is straight through the coupling capacitor. In fact, if you have ever looked for the AC signal component on the junction of two plate load resistors with an O'scope you'll see that none makes it through. Having said that you can always bypass the plate loads to roll off/filter frequencies (bogner shiva for example) to keep certain frequencies from completely going through the coupling cap.

My personal opinion (just an opinion folks) is that there is little if any audible difference between any type of resistor there, much less a 1 or 5 % tolerance metal film, and a precision RN, which is only a tighter tolerance resistance. If you think about what the resistor is supposed to do in the circuit a $.03 metal oxide should work and sound as good as anything else. After all, it is there primarily to drop & develop plate voltage.

Most "holygrail" vintage tone machines had 5% Carbon Comps that had drifted and settled in the ballpark for required resistance. Of course they all need to be changed due to moisture accumulation over the years which causes snap crackle & pop to live in there.

[FUCHSAUDIO]

They are not RoHs...the Mil-Bel stuff (RN series etc) are quiet, consistent, do sound good, and gave good "curb appeal" to customers. Tonal/noise improvement is subjective. I imagine it's additive, if you have enough, you will hear the sum.

[chopstuck]

To get it straight in my head, the general feeling I'm hearing seems to focus on:

Metal films for plate loads, input resistor and 1M input ground
Metal oxide for current drops between nodes
Carbon film for signal path in most instances
Carbon comp in high voltage hi current signal positions outside FB loops.

Is this fairly accurate ? Specifically what are the key double secret positions where the CC's work the supposed magic ?

[Bob-I]

If you think about signal flow, plate load resistors have little if anything to do with signal developement.

I disagree. I can hear the difference clearly between carbon film and quality metal film on plate loads. I know what you mean about not seeing it on the scope, but I can hear it, in fact so could the whole band when I first swapped out CF for RN65's in my Dumble clone.

I agree with Cloudhopper, except that I prefer CF for the input resistor. I'm not sure I can really hear the difference, but since it's in the signal path....

[collinsamps]

To each his own. You can disagree with a subjective audible change if you like as it is in fact subjective. But disagreeing that there's an ac component on the plate load resistor? I'd like o see the scope crt on that one please.

[Bob-I]

To each his own. You can disagree with a subjective audible change if you like as it is in fact subjective. But disagreeing that there's an ac component on the plate load resistor? I'd like o see the scope crt on that one please.

No, I said I agree that you can't see it on the scope. I can't explain what I hear but the tests I did were definitive.

[paddy]

If you think about signal flow, plate load resistors have little if anything to do with signal developement.

I didn't think you could develop a signal without one

The AC component will always take the path of least resistance which is straight through the coupling capacitor.

Wouldn't the plate load resistor be the easiest path to ground seeing
that one end of of it is connected to the supply which is effectively
A/C ground?

In fact, if you have ever looked for the AC signal component on the junction of two plate load resistors with an O'scope you'll see that none makes it through.

Are you talking about looking for a signal at the power supply end of
the plate load resistor?
Again this is A/C ground,I wouldn't expect to see much there.
The signal must pass through the plate resistor in order for a voltage
swing to develop across it.
Just my 2 cents

cheers,
paddy

[jaysg]

When I swapped them in, I felt I could hear more sustain after the initial pluck and a clearer, less grainy tone. The CF graininess was only apparent after the swap to RN65.

Any different perceptions? It's so hard to describe this stuff.

[Chappy]

If anyone is interested in the theoretical explanation of carbon comp "mojo" read the article on Keens site

www.geofex.com

on left side of page at bottom click on "Search GEO"

type in "carbon comp"

open "carboncomp.htm"

This article should answer a lot of questions in this thread.

Enjoy
Chappy