Carbon film vs. metal film? Discuss...

From Google
Metal film produces less thermal noise than carbon. Metal film resistors also typically have a much lower inductance/capacitance than carbon so they(metal film) work better at higher frequencies. Carbon has no real advantage except that they are cheaper.Jul 29, 2012

 

Metal oxide for me. Very heat resistant and always dead on value. Although, other than value accuracy I don't think resistors make much difference.

 

We are stardust
Billion year old carbon
We are golden
Caught in the devil's bargain
And we've got to get ourselves
Back to the garden

Joni Mitchell

Carbon film lets us use modern components and still feel like maintaining sort of vintage mojo!

Metal film let us be super accurate and reliably quiet for those who dare not succumb to pier pressure.

The price is negligible for a hobby builder unless EVERY penny counts.

How do they sound? I won't go there.

 

Which are cheaper? Who has free shipping?

That pretty much drives my decisions on resistors and caps.

 

I went through all this years ago and here is what my experiments and consolidated findings were.

EQ and preamp section please, no metal. Just not harmonically pleasing to the ear.

I did some experiments with this in my vintage vibrolux when it was time to recap a few years ago. I replaced all the caps with orange drops components. The results was it absolutely sounded clearer, more powerful but tonally lifeless. It was just loud and hard sounding. After a couple of months, I replaced everything with as original as I could locate them, capacitors. The result was a more rounded, pleasing tone with richer harmonics and yes, slight distortion characteristics.

One man's experience. If you want a more edgy clean and pushed sound, go metal. Maybe in a loud surf type band. If you are looking for more resonance and rounded traditional rock guitar tone, try to find something like the originals. There are lots of vintage type caps out there today.

One man's experience.

 

I've read where people have said they used all metal film and the amp turned out too bright, or sterile, etc. - warmer sounds from carbon comp & carbon film. If the above is accurate about metal film working better at higher frequencies, I could see the argument being made where MF "working better" at high freq. allows more highs to accurately pass through, thereby CC or CF NOT working as well at those frequencies may filter them out/loose them along the way, and end up with a "warmer" tone. No experience in comparing the two, just taking a guess.

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I don't really, know but I started using them years ago, mostly because the CC I tried buying were dog doo now days. Some new 100k ones were like 140k etc. Way off. But have used oxide in my BF Fenders pretty extensively now for years and I dont hear a detriment.

 

The "...works better at higher frequencies..." description is in reference to stuff way outside the range of human perception. Like RF.

 

Some experts claim carbon film produces less shot noise than metal film, but there are others that claim the opposite.

I've tried both types and while you can see it on a scope, it's all a wash once the sound is out of the speaker and mixing with the bass and drums and vocal caterwauling. To me, it's like changing from Phillips to slotted screws to hold the pickguard on your Tele.

It's not going to matter when you're playing. That's just me. The fact that there's no true consensus after many years is quite telling.

Professional driver on a closed course. Your mileage may vary.

 

Metal film for me. Specifically, Dale RN65D resistors. Super low noise, 1% tolerance. In the power supply I use Dale CPF3 resistors. I am colorblind and appreciate that they both have the values printed on them, rather than having to decode the stripes.

They both also have non-ferrous endcaps (which some say sound better than resistors with magnetic endcaps*), if you're into that sort of thing.

*Morgan Jones, Valve Amplifiers, pg. 125

 

I love this thread. I think everyone who has pitched in so far has more real-world experience in all this than I do, but hey, it's the Internet, so I can still have an opinion, right?

I have used metal film between the inputs and V1 of the amps I've built, and that's it. The rest has been carbon composition or metal oxide in the power-dropping section or as grid stoppers or whatever. I don't mind the extra carbon comp hiss, and to my mind, a quiet amp is largely about the grounding scheme and the solidity of the solder joints, anyway. But again, I don't care that much. 60-cycle hum doesn't bother me; P-90's don't bother me. It's all a part of the harmonics.

But this bit from Ken Fischer did make me shy of using more metal film than I have:

And there are a lot of things I've found that I just don't think work for anything. Like metal-film resistors -- I've never heard an amp with metal-film resistors that didn't sound harsh. A lot of guys will say, "But they make the lowest noise." Oh, absolutely, they're far lower-noise. Carbon film is lower-noise than carbon comp, but metal film is way lower noise than either one of those two. Yeah, you can get less noise, but you won't get as good a guitar tone. (from Dave Hunter, The Guitar Amp Handbook, p. 236).

So, of course, that solves nothing. But it is one guy's opinion.

And since I have no personal experience with carbon film, I'll just eat my popcorn and watch the thread.

 

Oh, and carbon comps are also non-magnetic

Resistors by mabinogeon posted Dec 3, 2019 at 11:25 AM