1 watt Carbon Film or 1/2 watt Carbon Comp?

[Nolatone Ampworks]

Hey good people,

I'm getting ready to order components for my Nolatone Model 1 prototype amp.

I know that 1/2 watt resistors in the audio path are considered by most to be adequate, but for some reason I prefer the idea of using 1 watt resistors.

However, some suppliers have resonable prices on 1/2 watt carbon comp resistors.


What would you rather use?

1 Watt Carbon Film, or
2 Watt Carbon Comp?

Thanks,

Paul

[Blue Strat]

Depends on the circuit. If the resistor isn't dissipating more than 1/4 watt, 1/2 watts are fine.

Also, read this http://www.geofex.com/Article_Folders/carbon_comp/carboncomp.htm

[Trout]

Hey good people,

I'm getting ready to order components for my Nolatone Model 1 prototype amp.

I know that 1/2 watt resistors in the audio path are considered by most to be adequate, but for some reason I prefer the idea of using 1 watt resistors.

However, some suppliers have resonable prices on 1/2 watt carbon comp resistors.


What would you rather use?

1 Watt Carbon Film, or
2 Watt Carbon Comp?

Thanks,

Paul


I always use 1watt carbon film.

Recently I did a quick temp stability test, Carbon comps failed miserably.

I forget the actual temps involved, I lost the paper I wrote it down on.

But it went like this.
I took a carbon comp 1meg and attached it to my meter and heated it with a heat gun and took pyrometer readings and watched for drift.
I then repeated the process with carbon film.

The carbon comp started to drift at extremely low temps, the carbon film held its value at nearly twice the temerature.
Which sounds better is an entirely different topic, but from a tolerance standpoint, The 1W carbon films test far better even under extreme abuse.

YMMV

[Nolatone Ampworks]

I always use 1watt carbon film.

Recently I did a quick temp stability test, Carbon comps failed miserably.

I forget the actual temps involved, I lost the paper I wrote it down on.

But it went like this.
I took a carbon comp 1meg and attached it to my meter and heated it with a heat gun and took pyrometer readings and watched for drift.
I then repeated the process with carbon film.

The carbon comp started to drift at extremely low temps, the carbon film held its value at nearly twice the temerature.
Which sounds better is an entirely different topic, but from a tolerance standpoint, The 1W carbon films test far better even under extreme abuse.

YMMV

Yep, no doubt, accuracy and stability are better for the more "modern" style caps.

Let me share a story I heard about this:

A guy had a vintage Tweed Bassman. took it to a tech to have it overhauled. He wanted all the resistors "updated" to metal oxide (those are the ones that can go do 1% tolerance, right?). He wanted those because they were THE MOST precise, and therefore, "better".

They rebuilt the amp as specified and it sounded sterile. Just didn't have the magic of a Bassman.

So, they replaced all the metal oxide with Carbon Comp and the amp had it's vibe back. He probably would have been fine with carbon film as well in that respect.

I think part of what makes a tube circuit so "vibey" is the way the components "loosely" interact with each other.

That's just a story I heard, though, take it for what it's worth.

Some of the best amps I've played have had carbon comp resistors, and others have had carbon film. I'd like to build one each and see if I can hear a difference.

[Trout]

No Doubt they sound different, Some feel carbon comps sound different brand by brand also. In my test I used Ohmite brand Lil Devils which are basically era correct for 50's 60's gear.

I have built amps with both, I actually prefer the films in most circuits I have built. I notice more difference in SE amps as they seem to respond to changes a bit differently than many PP amps.

My monster Champ 807SE sounded boring with film resistors. After 3 years I have not checked it for drifted values yet, mostly because it works so well and I am to lazy to take it out of the cab.

[rooster]

I think the old Marshalls were all Carbon Film. Could be wrong, but I don't think so.

There's a HUGE difference between Metal Film and Metal Oxide. Metal Film is great for audio, Metal Oxide is good to drop power with great stability. I've used Metal Film in all my amps, and they are quite, and "sterile" is not a word that is ever applied to them.

rooster.

[Wakarusa]

For your Bassman story, some of the "mojo" in the old amps is directly due to the poor temperature stability of the carbon comps. They can also be frequency sensitive in high voltage applications like plate loads.

There are, however, several advantages to the 1W carbon film part.
- a lower noise floor. Shot noise is a function of the resistor's cross sectional area. The 1W part is bigger, so less shot noise.
- most 1/2 watt parts are rated for 350VDC (or less for higher ohm ratings) while the 1W parts tend to be 500VDC rated.
- the carbon film is less susceptible to moisture/humidity and is has better temperature stability. If you want the Bassman to have it's mojo, measure what the hot carbon comps are doing and replicate that effect with more predictable/stable parts so it always does it

I keep flopping back and forth on the 1% metal films. For high ohm values you get a more predictable part, but in a lot of applications (ground references) the 5% tolerance of a carbon film is fine and the part is cheaper.

[Nolatone Ampworks]

Methinks I'm just gonna go with 1W carb/film. If it's good enough for Ken Fischer, it's good enough for me! :-)

[JJman]

Speaking of Ken Fischer, I just finished my build which uses an Express preamp design. Because of the high gain, the hiss from the 1st plate resistor was important to me. I tried the 1w CF and some MFs. I ended on a 3wt MF for minimum hiss. The Dale one is quieter than the VC one.

2nd stage I’m using the 1w CF and it has no hiss. 3rd stage I'm using a 1wt (maybe 2wt) CC and that stage hisses a small amount. I’m using a PPIMV so the 3rd stage hiss is easily dialed out with a short turn.

[trey85stang]

i only use metal film for anything less then 1w. Metal oxide for 2-3-5 watters. Ive never bothered to try carbon comp or film, but I would think the loose tolerances would be good thing to give the amp its own uniqueness.