Carbon Composition verses ?

[Structo]

I was having a friendly debate with a guy over the use of carbon comp resistors when servicing an old amp.

He said that the CC resistors impart 2nd order harmonics and add the mojo that we all love.

I had never heard that one before.

I have read that when subjected to high voltage the CC resistors can induce noise as hiss or rushing noise into the circuit.
And also drift with age, can absorb moisture and become noisy.

I see some builds and kits still using the CC resistors and was wondering what the general consensus is about the use of them in a amp.

This guy claimed that the film type resistors (carbon, metal, metal oxide, tantalum) have inductance because of the spiral construction and that it can hurt tone.

I am aware that there is some inductance, but enough to hear?

He tried to prove his point by referring to this at GeoFex:
http://www.geofex.com/Article_Folders/c ... oncomp.htm

But at the end of the article he states:
Use CC's sparingly - only where your personal ears tell you that they make a difference.

Seems that the more successful amp builders have moved away from CC resistors as technology made the other resistors more reliable and less noisy.

He said he prefers all carbon comp resistors in his amps.

I can see using them in the old classic circuits like a 5E3 Deluxe.
But then again, would you want the problem associated with them?

A friend that just built one is having a big problem with hiss in his amp.
He used all CC resistors......

What say you?

[Zippy]

I was having a friendly debate with a guy over the use of carbon comp resistors when servicing an old amp.

He said that the CC resistors impart 2nd order harmonics and add the mojo that we all love.

Game over. His Mojo card trumps any scientifically-based argument.

Looks like the beer's on you.

If 2nd order harmonics are noise, then he's right. I've heard the noise myself - and removed it with judicious plate resistor exchanges.

Mmmmmmm, Mojo...

[mhuss]

Well, to quote R.G.K.
"Use CC's sparingly - only where your personal ears tell you that they make a difference. "

I have on occasion (e.g. doing a proper 18watt clone) used them as PI plate loads, and perhaps plate load for the stage before, but that's it. As a general rule 1 watt CF everywhere, the exception being I use 2W metal film for the input 1Megs for minimum noise.

My favorite vintage amps all used CFs or MFs anyway...

--mark

[Structo]

I guess what I am looking for is opinions of the more experienced builders here if you use the CC resistors and why.
Thanks for the first two replies.


I've read a lot of material on the web about them, but mostly it is just opinions not really backed up by fact.

The guy with the 5E3 is pulling his hair out about the hiss he has in his 5E3.

He lives on the east coast so I can't pop in and listen to it myself.

He mentioned a hiss and crackling which I have heard from a bad preamp tube before.
He did some tube rolling on it and the noise remains.
I told him to hit all the solder joints again just in case he either missed one or has a cold joint.

[Kregg]

Could it be that the mojo comes when a CC resistor fails prematurely; giving you that dented-Fender sound?

[Alexo]

Fads come and go, cc's seem to be in vogue with the less experienced builders, but passed over by the more experienced.

I've used them on a few builds - though I usually use 1W CF's - the amps sounded good, but without building a dedicated switchbox to swap the CF's with CC's for a direct A/B comparison, I don't feel qualified to give a definitive opinion.

But what I can say is this:

I notice no lack of mojo when I use carbon films instead of carbon comps.

but

I do notice the presence of noise and hiss when I use cc's.

I can't say that using cc's or cf's has ever really correlated with how "good" an amp has sounded.

[Zippy]

I guess what I am looking for is opinions of the more experienced builders here if you use the CC resistors and why.
Thanks for the first two replies.

This guy is saying he has built hundreds of amps, using all CC resistors and hasn't had any issues.

Carbon comp will give you shot noise. You can reduce it by using larger cross-section (ie, higher wattage rating) resistors or choosing an alternative design resistor. When I used to repair truly vintage Fender amps that was a familiar starting place to get the noise out. Carbon comp resistors accumulate damage over lots of years of use. The only way to fix it is to replace the resistors. If you keep the same size (wattage) CC resistor, you stand a good change of still having a little noise and the noise will slowly creep up with time. Go a little larger and you'll improve things. Go CF or MF and you'll eliminate the issue.

[txbluesboy]

I really feel that we as a group should use our collective influence and force our suppliers to list the MOJO factor of different components in their catalogs, right alongside current capacity and temperature coefficient. We would however have to come up with a standard unit of measure, I propose we call it the mjf, as in this resistor/capacitor is rated at .865mjf. Don't you think this one little change could really simplify our lives?

[Cygnus X1]

For Sale:
Handbuilt amp with MJF rating at 2.136!

MOJO features include:
Interleaved paper insulated open ended transformers.

Wax, Dry Caps, canister caps, paper in oil fairly used in "all the right places".

Carbon comp, carbon film resistors used everywhere.

Vintage cloth covered wire. No tone-robbing insulation to rob tone. Just cloth. Sounds even better with dripping humid environments!

Fishpaper eyelet boards. Slighty conductive to distribute MOJO as intended.

Lead dress painstaking placed. Not pretty, but lots of MOJO in there. At least a .5 factor.

Brass grounding plates for the pots and jacks. Not at all necessary, but good for a .075 MOJO factor.

Vintage CTS pots. Open architecture to absorb MOJO that floats throughout the amp.

2 prong unpolarized power cord. Everyone knows 3 prong cords kill MOJO!

Astron .022 Death Cap. They killed a lot of MOJO by removing this along the way.

[ChrisM]

I was having a friendly debate with a guy over the use of carbon comp resistors when servicing an old amp.

He said that the CC resistors impart 2nd order harmonics and add the mojo that we all love.

I had never heard that one before.

I have read that when subjected to high voltage the CC resistors can induce noise as hiss or rushing noise into the circuit.
And also drift with age, can absorb moisture and become noisy.

I see some builds and kits still using the CC resistors and was wondering what the general consensus is about the use of them in a amp.

This guy claimed that the film type resistors (carbon, metal, metal oxide, tantalum) have inductance because of the spiral construction and that it can hurt tone.

I am aware that there is some inductance, but enough to hear?

He tried to prove his point by referring to this at GeoFex:
http://www.geofex.com/Article_Folders/c ... oncomp.htm

Seems that the more successful amp builders moved away from CC resistors as technology made the other resistors more reliable and less noisy.

He said he prefers all carbon comp resistors in his amps.

I can see using them in the old classic circuits like a 5E3 Deluxe.
But then again, would you want the problem associated with them?

A friend that just built one is having a big problem with hiss in his amp.
He used all CC resistors......

What say you?

Sprial construction?

All of those compositions that I have looked into were solid. I could see those high power wire wound resistors having inductance though.

[Zippy]

He tried to prove his point by referring to this at GeoFex:
http://www.geofex.com/Article_Folders/c ... oncomp.htm

OK, I read the whole article. Did your friend? Did you?

R.G. makes a pretty strong case AGAINST CC resistors as I see it. Says about the only place to use CC's is MAYBE, IN LIMITED CASES, in the last stage before the PI and that's it.

[txbluesboy]

[Structo]

He tried to prove his point by referring to this at GeoFex:
http://www.geofex.com/Article_Folders/c ... oncomp.htm

OK, I read the whole article. Did your friend? Did you?

R.G. makes a pretty strong case AGAINST CC resistors as I see it. Says about the only place to use CC's is MAYBE, IN LIMITED CASES, in the last stage before the PI and that's it.

Yes I did, that is why I brought it up.

[Jana]

Structo wrote: "I guess what I am looking for is opinions of the more experienced builders here if you use the CC resistors and why."

I suppose I am an experienced builder, I have lost track of how many amps I have built years ago.

I don't use CC resistors. I like my amps to be quiet, tight, precise. I prefer the Dale RN65's and use them exclusively except where I need higher wattage. I have built amps for some skilled and highly discriminating players and none of them have asked "where's the mojo?" I have built an amp where the customer specifically wanted CC and would not have it any other way. I made him supply them. I heard nothing in that amp that made me want to change my mind or wish that the amp was for me, quite the contrary, I am glad it was not my own amp.

Some things do have mojo, many things are plain hype.

This argument could go on and on. As mentioned, the only way to settle it is to have an amp set up with switches to change from CC to films. This would keep everything else the same, caps, transformers, tubes, lead dress, etc. Then it would have to be a blind test with players and listeners not knowing which resistors are in the circuit. Even at that I don't know if it would be an accurate test since if there was more hiss when the CC's are in, those that are believers of myth will think they hear an improvement in mojo. Likewise for those who are heathens and don't believe in the CC mojo. So, I suppose, introduce an random hiss into the amp to mask any inherent hiss, lol.

[Richie]

then some will say a .02 cap is a .02 cap and will not have a difference in the sound of an amp,or no mojo.. NO ONE can make me believe that.

As for CC resistors, i think it depends on what someone likes and wants to use. As for the noise,if there is noise,then most likely you have a bad one. I have worked on old fender amps over 45+ years old with CC,and they can be quiet as any other amp. I think the CC get a bad reputation.

Yes some can be noisey,and cause problems. They drift etc.. So you may have to do some measureing. Most of the time you'll find problems of noise,say if your repairing an amp that has set a long time, never played,or in a damp basement,trunk of a car overnight etc... This is where you find most problems.

I've seen many times people hear or read they cause all kinds of problems, and remove them, and replace them with CF or MF resisotrs.
Then they will say their amp lost the tone. And put the resistors back in,and the amp sound like it did before the CF were installed.

Its all up to what you want to use. I have no problems using them. And some botique builders still use them. Some are getting very expensive.
Many of the best sounding amps,Marshall, Fenders, Gibsons, etc.. have used CC resisotrs.
Maybe the best way is to try it for yourself, forget what you read or were told, and let your ears judge. I don't think they have a machine to measure what good musical sound is, that is pleasing to the ear. Because everyone has a different opinion of what is good to them.

You may read when measured the CC resistors have a noise to them, what kind of noise? Someone may think jazz is noise or metal.. This noise may not be noise to some. It is something..maybe its good, or bad? Only the person hearing it should judge if they like it or think it is noise.

If you have good resistors, i don't think you'll hear any added noise..If you have bad ones, then you will..

All this is just my opinion.. yes i do think they have a mojo,that no one can measure. I have been a member of many forums, and see this come up all the time, and you'll have alot of nay-sayers..