Opinions on Allen & Bradley Carbon Composite resistors

[rtsang]

Dear all,

Just want to solicit you opinions on using AB Carbon Comp as plate resistor and cathode resistor
Assume I can match them from a big lot.

I read some people think they are musical, but others think they are noisy.
Any precautions when I use them?

They seems to be a bargain when compared to the other boutique resistors.

Regards,

Raymond

 

[scott wurcer]

Just FYI, I am unable to recreate a 1/f noise generator that Walt Jung and I published in 1982 because it seems that AB has improved something in their CC resistors. In the past the excess noise was bad enough that you could make a nice "perfect" pink noise generator without any RC networks!

 

[poobah]

Are you building a guitar amplifier? ... or HiFi?

 

[rtsang]

Audio amp

Does this resistor contribute much to the so called "vintage sound" of those old amps?
My gut feeling would be the caps that were contributing more to this signature sound.

Raymond

 

[poobah]

Many things contribute to the sound in guitar amps... power suppply sag (undersized caps) being one of them.

For HiFi... I would not get near a CC resistor of any sort.

 

[HollowState]

For HiFi... I would not get near a CC resistor of any sort.

A lot of people say and think that. A lot of people swear by (not at) the sonics of the coveted Mercury and RCA recordings of the 60's that were produced with electronics that were filled with carbon resistors and paper/wax capacitors. (called condensers back then) And yes, they were much newer back then when in use.

I think that NOS Allen Bradleys from the 70's and later are good resistors. But only AB's of that vintage. Older parts are not good, because of drift and noise, and other makes like IRC or Stackpole are inferior. A possible exception may be the later Ohmites. I use them in higher level stages and power supplies. (I have thousands) For low level stages, stick with the better films or even wirewounds.

Victor

 

[poobah]

HollowState,

I have read plausible arguments that the voltage coefficients in CC can actually cancel other non-linearities in tube amps... and that does indeed make sense. Keep in mind, conservative design with CC's meant grossly oversizing them... thus minimizing their "gift".

I fiddle with guitar amps and such... and make it a point to put in CC's... running hot as hell. I don't listen much to power and speaker cables... but the "sound" of CC's is a real thing.

 

[Trout]

I fiddle with guitar amps and such... and make it a point to put in CC's... running hot as hell. I don't listen much to power and speaker cables... but the "sound" of CC's is a real thing.

But Which CC's are actually the best in guitar amps?

I used AB's on several builds, and could not detect any difference between those and the latestOhmite Lil Demons

Givin the cost differences, Ohmites seem like a bargain.

 

[fdegrove]

Hi,

AB's CC resistors are a nice recipe against "digitalitis".
Always concert hall sweet and never strident to the ear much like the older copper lead Hoco resistors.

I very much question their neutrality though.

Cheers,

 

[limono]

I've read recommendation (Thorsten I think ) of "baking" them in an oven for short time 150C to stabilize parameters but I don't know specifics. I saw a picture of Shindo gear (WE300 LTD) built exlusively with vintage 2W AB resistors. I did not have a chance to listen to any of Shindos but reviews say they sound anything like vintage .Design around the parts seems to matter more . I could never understand notion of using "bright" component to tame "dull" one (so called synergy in simplified view).
Regards, L

 

[fredex]

Yep, CC do have a sound and if that suits your setup - ears use them.
But asking which is best will get no conclusive answer.

 

[poobah]

Ditto,

I wouldn't offer an opinion as to which brand is best... never paid attention. I would wager the geometries are all very similar anyway.

 

[dsavitsk]

I very much question their neutrality though.

I don't care much about neutrality. I care about having a stereo that sounds good to me. I use ABs as grid stoppers and like them there. I think they are every bit as good as Rikens or whatnot, and they are way cheaper. They are only $0.25 at parts connexion.

Some of the other vintage CCs I think sound dry and flat, but the little demons seem pretty good.

 

[rdf]

I've read recommendation (Thorsten I think ) of "baking" them in an oven for short time 150C to stabilize parameters but I don't know specifics.

By coincidence I was reading that just tonight. Morgan Jones, pg 208 3rd edition. Discusses an experiment in which new CCs baked at 135C for 24 hours showed a 1/2% change in value. The theory is heating relaxes the wound wire's tension. I've baked them for a different reason. NOS CC's are wonderful moister absorbers. They spew endless fluid under heat. Personally I much prefer PRP.

The poob and fdegrove in the same thread!

 

[limono]

Oh, forgot my recent story with crackling intermitent sound on one of my monoblock (717a , 45) I knew that it was from input stage .I replaced all PS caps , than resoldered wires a couple of times , than Kiwame cathode resistor with 50V BG N cap ( I thought that 3V bias is to low for 50V rated cap) than I replaced NOS octal socket , filament dropping resistors and shunt cap , coupling cap to output stage and grid resistor. When there was nothing else to replace but a brand new (well almost ) Vishay/Dale 2 Watt plate resistor I said what a heck and put vintage AB 2W -problem solved . Well I'm just a half witt and couldn't mentally settle that new ,reliable, metal/film could give me a problem with 3 mA current.

 

[athos56]

Another option

I used the Ceramic Comp resistors in my last project. My ears liked them, my Kt-88 amp will use them as well.

 

[rtsang]

How does the effect of resistors compare to caps

Thank you guys for all your input.

Personally I found the sound of caps a magnitude more audible than the sound of resistors.
My worry is these AB would drift with time and heat.

Raymond.

 

[duderduderini]

Carbon for me

Being a Carbon based life form, it is only fitting to use them in ones amp.... Seriously though for me I much prefer Carbons to Metal film and as other posters have pointed out, it comes down to preference. No doubt many classic Tube amps are packing CC resistors and they sounded good.
It is like every other component in this field.. boutique this and boutique that.. I have just built an amp that deploys 2 dollar MKP's made by vishay.. having tried several PIO's and some russian ones as well... couldnt tell much of a difference so I went with the new production mkp's.
So i think it comes down to trying one channell with one component and the other with something different and then judging.
I do believe the older cc's can drift with temp, again I deploy cc's from mouser/rs components.. they are touted as being High stability" Again buy some and compare them.
Welcome to the world of DIY
Nick

 

[exeric]

I don't have direct experience with the sound of CC resistors but from everything I've read, including a blurb about them on Menno Vanderveen's website, its a real thing. He said that he recommended changing to CC resistors on the input stage - don't know which ones specifically. I suspect it wouldn't be the ones having anything to do with controlling balance of current on differential stages due to drift issues. He said he wasn't sure he he was being objective on hearing the decided improvement with CC resistors there so he asked other people to try it on the same amp to see if they agreed. They did.

The issue of the sound of CC brings up another issue. If its a distortion that produces the agreeable sound one might want to try more of it. Naturally the input stage would be the most amenable for that purpose. But if distortion is caused by stresses induced within any component it might be difficult to induce sufficient stress within a CC resistor with the low level signal in the input stage. If one goes the input route it seems like it would be best to use the smallest wattage CC resistors you could get away with, at least as a first approximation. Later amplification stages would have less affect on the sound but would have higher stress induced distortions due to the higher signal level. 6 of one, or a half a dozen - its sort of an arbitrary decision until one has actually tried it. My gut tells me the input stage is the place for CC resistors though.