Carbon Composition verses ?

[Zippy]

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.

I'll buy into most of what you're sellin', Richie, but sometimes "noise" is "noise". It's not about interpretation of "Do I like it and does it make me wanna tap my toes?", it's a fact of physics.

Whether you like a little background hiss is up to you.

[Aurora]

[quote="ChrisM"][Sprial construction?
quote]

Film resistors are made by milling a short spiral in a conductive layer, as opposed to composition resitors, which are - a solid rod of mixed material. This spiral is certainly inductive, but at pH levels - usually associated with microwave frequencies. I do not believe this is audible in aguitar amp!.

Coming from an engineering background, and some decades as a sceptic in the HiFI asylum, I must admit I do find some of this "component tonality" hard to swallow, and more often than not related to some sort of black magic mojo. If it's of any help, it's even a lot worse at the HiFI asylum

Somehow I wonder if a lot of the differences certainly heard are due to component tolerances - a 5% shift of component value is quite audible in a tone stack - whether it's better or worse , or just different, is another story. Common vintage parts were often 20%, and the guitar amps I've been inside so far, does certainly not excel in high quality parts.
I do agree that there are differences in types of capacitors, but I find it hard to believe that one brand of propylenes are " true mojo" whereas another brand is just crap, - their parameter differences hardly being measurable. In terms of quality parameters, some of the real stuff proclaiming "real Mojo" are actually of the worst parameter wise.
Resistor noise was a major thing in HiFi in the 70's, and "everyone" changed to metal film, which actually have lower self noise than other types. Nowadays, it's turned into a real asylum, where carbon comp is better over here and not usable in there, and in the next version it is the other way round! There is also a solid conviction of Trainwrecks being very high gain amps, and Dumbles even more so. Compared to REAL low input signal amps, guitar amps are mid to low gain! - appx 100mV input signal, as compared to e.g. a moving coil pickup amp, with 0.1 mV input, or instrumentation amps with a mere few microvolts! I would of course not use carbon comp resistors in the input section of a guitar amp either, but resistor noise in the PI or power section???? Hm.....

But yes - you're right! I have not built a guitar amp yet! I do have, however, built quite a number of HiFi and PA/ sound distribution amps and gadgets, as well as 30 yrs+ of scientific instrument stuff.
I'm here to learn about guitar amp Mojo! - with the scepticism of science engineering...

< ducking - helmet on - ear plugs in - flamesuit ready >

[billyz]

Well I will be the Devil's Advocate then.
At one time I did quite a bit of vintage amp restoration and I would replace all those Noisy Bad drifted carbon comp resistors with Nice shiny new modern Metal film. Yep , I could tell a difference, the amp was maybe a tiny bit quieter . At first I was really taken with the new and improved sound.
But , after a while I missed something. I think I like the distortion of the carbon comp resistors, at least in older vintage amps. They sound woodier to my ears. And I am relying on my ears, not the myths of the Internet. And , replacing one is so subtle I probably could not hear the difference, But when you do all of them you can hear it.

There is one exception, Some of the really old Carbon comp resistor are really crappy, they look like they came out of a box of crayons, very early 50's.

Yes, carbon comps drift with age and they sometimes do make " snap , crackle , pop" if they get noisy used on the plate of the preamp tubes.

But, I have found just as many noisy Carbon films in that position as well.
I get fender bluse jr's and hot rod devilles, etc. in all the time with noisey plate resistors. all film types resistors.

I have built a few Wrecks and wreck style amps and they are pretty quiet, with carbon comp resistors. I do have to select the tubes for noise though.

If I was restoring or cloning and old Fender or Marshall, etc. I would absolutely use carbon comp, preferably allen bradley or stackpole.

I am not advocating anyone use them in the amps they build or even fix restore what ever. Just that I like and prefer them in my work. My clients know what to expect from my work and they know the sound I get. If they like it and approve they come back over and over and tell their friends.

I think everyone should be true to their convictions , and I like that so many are using Metal film, carbon film, orange drops, solid wire, alpha pots, cliff jacks, all the personal choices they make in their work. And that they can or can't hear a difference, seriously. It's like cooking, everyone cooks differently.

I am not saying to not replace a BAD resistor, what ever the composition is. Or that the resistor is the main component of the sound, just one small ingredient. And we are talking about Guitar player amps, I think most of them like distortion and even some might say noise

My 2 cents, FLAME ON

[Aurora]

Well, there are several things here....

- I have absolutely no objections to choosing parts like pots, switches, jacks plugs etc based on experience of what works in the long run and what does not work. Component reliability should be a major concern for any builder - it certainly is in most professional trades. - Maybe not so any more in consumer electronics, where estimated lifespan is a real factor, in opposition to production cost. More and more of our stuff is now built with a short estimated lifespan and not " to last" as it used to be.

- I also do respect a personal conviction about what works, as long as it is not in direct opposition to known technical facts. Sometimes "highly acclaimed convictions" are......

- Active components, tubes, transistors, diodes etc. are the major producers of non linearities, and thus distortion, be it the kind of disto we do like, in e.g. guitar amps, or those we don't like in e.g. HiFi amps. These components have a full set of rules on their own, and discussions and opinions about these are fully understandable, although conclusions are not always --- understandable

- It's the seemingly endless discussion about resitors and capacitors I sometimes have problems with. Power rating and wattage is obvious, but "what sounds good in which context" is far from obvious, at least to me- so far...
I'll just keep reading - seeking the Mojo!

[Alexo]

... but "what sounds good in which context" is far from obvious, at least to me- so far...
I'll just keep reading - seeking the Mojo!

Yep... I think amp building is both a science and an art. The CC vs film debate veers heavily towards the more subjective, artistic side of the process, which makes the debate interminable, as no logical conclusion can ever settle what is, at heart, a matter of taste.

Personally, I just take my amps to the local shaman, who imbues them with all the mojo they need.

[Aurora]

Personally, I just take my amps to the local shaman, who imbues them with all the mojo they need.

Wel, well- who would have thought..!
And as it happens, there are are usually some of them up here north!
Just a mere days ride away!

[Structo]

Heheheheh, I should have guessed this would be a hot topic.

Kind of like when somebody asks, what is the best pickup or tube.

Very subjective it seems.

Funny that the proponents of using the ultra quiet metal oxide or metal film resistors still use the carbon trace potentiometers.
Do those cause noise?

And although I haven't proven it to myself by experimentation, it seems to be a fact that the resistance of a carbon comp resistor changes with the voltage it is subjected to and the temperature of said component.

In a vintage amp that has as a whole a 20% tolerance in it's components, if they all align with the stars and the moon phase is right, you might get that one amp that is very special indeed.
But if that same amps tolerances to the other way and it sounds like horse manure, then we can blame the carbon comp resistors or those funny looking blue molded coupling caps.

So from the response given so far it seems to be a matter of choice what kind of tone a builder is after or what he thinks contributes to that tone.

Be it the mojo from carbon comp resistors or other components sprinkled with fairy dust.

[Andy Le Blanc]

Here is a quik scan of some resistor data, it from an Audio Express article.
There nothing bad about CC resistors, it the application, if you want a dead silent
phono pre-amp don't use them, but they are another option for the builder
to "feature". As far as adding harmonic distortion, that's a dog pile statement,
but they do add a subjective quality to tone.

[Richie]

billyz.. i'll stand with ya..

I'll buy into most of what you're sellin', Richie, but sometimes "noise" is "noise". It's not about interpretation of "Do I like it and does it make me wanna tap my toes?", it's a fact of physics.

Whether you like a little background hiss is up to you.

If you have hiss, and crackle or pops..that is unwanted "noise"
if you use a good resistors, then you won't hear that noise.. it will be quiet.. a conductive board will cause the same thing or sound.. dirty tube socket can cause the same thing,dirty tube pins can cause the same thing or sound, even tubes themselves can sound like old noisey CC resistors.. so maybe what people are hearing is not the resistor and its something else. But blame it all on the CC resistors..

For example.. some people cringe when they hear someone rake their fingers down a chalkboard..
If you use certian caps, it can have the same effect. A very unmusical sound,unpleasent to the ear..
This amp may have wonderful clean sounds, but when pushed into distortion ,thats when the cringe comes on.. Like a pull boost fender distortion..lol

guitar amps are not hifi amps,and most are loud.. after a few sets of 50 to 100 watt amps, i doubt you'll hear anything but your ears making a shhhhh sound.

Also.. if there is no difference in resistors, why would someone pick a RN65 over another resistor? Or a MF over a CF.. Is there mojo in those too? Mojo in different brands ? Yeah there are probably some bad CC resistors brands, as they are as much when camparing one cap to another.. And yes, the signal goes through the pots.. do different pots have a different sound?
Some of the best amps i have ever heard use CC resistors, and are quiet.
Sometimes you can steralize an amp by buying the most expensive parts.

I'm not trying to talk anyone into useing anything. Use what you like. If you think it sounds good, thats all that matters.. But as people say don't buy into the mojo or hype of CC resistors,the same could be said about Using CF or MF or whatever..

I usually don't answer these posts,as they get into an endless debates with no winner..

[billyz]

I believe most amp builders these days are more artisans than assembly line workers. Every artist develops his favorite colors and technics, signature brush strokes or should.

I don't know anything about " mojo" except what " Austin Powers " had going.

Howard Dumble , Ken Fisher and many others here and elsewhere ,could and do make a great sounding amp with Metal film or Carbon film or even CC resistors. You hear it , you make it sound like what you hear.

Guitar amps users are pretty unique, who else would want so many things wrong. The quirks of vintage technology live on, or else we would all be using and making solid state 000.000% thd amplification devices.

BTW, if i were to make a moving coil stepup amp I would probably use Bulk metal foil or better resistors ,and teflon capacitors ,even in the power supply, and everything would be regulated.

[rfgordon]

I've used a variety of resistors in various locations, and I, like a lot of builders, have my preferences.

On plates for the first two gain stages, I generally prefer PRP 1 watt. I think they sound warm, clear and quiet. RN65s are great, too, depending on the amp topology. Much of the time I put CFs in the PI.

A couple of years ago I got a fistful of 1 watt CCs in 100k at a yardsale. I plunked them in an amp, and it was icky. After putting in/out over a dozen trying to find quiet ones, I gave up. Now, I will admit that the resistors themselves may not have been to blame--these guys had been stored in a jar in a garage for who knows how many years! I venture to say that humidity and the seasons may have taken quite a toll on them.

I keep meaning to try the new CC resistors: the Little Devils. I haven't seen anyone review those. Who knows, maybe they'd make me change my ways?

All I know is that guys dig the amps I make with the PRPs and the RN65s, and that's all I need to know.

I firmly believe that it is the totality of the amp design that really makes the most difference. Of course, just to be safe, I rub each amp chassis with a black cat bone....

[Richie]

just a random search for CC resistors, these are just what popped up, a very small portion of what popped up.. way too many builders to list..

Some of these builders are noted to being or knowing quite a bit about amps.. other links are measurements and good reading for the more technical stuff answered..


http://www.marshamps.com/resistors.html

http://www.geofex.com/Article_Folders/c ... oncomp.htm

http://ballsamps.com/construction.html

http://www.peerlesstone.com/node/72

http://www.guitaramplifierblueprinting.com/jw1.html

http://www.steelbender.com/spotlightgermino.html

http://www.harpamps.com/micKcircuits/Re ... noise.html

http://www.reinhardtamps.com/files/Storm.html

http://www.mercurymagnetics.com/pages/a ... an07-1.htm

quote--
The design of the EZG-50 includes a new 6L6 specific transformer designed for Dr Z Amps by Ken Fischer.

NOS Allen Bradley carbon comp resistors are used throughout the amplifier in all critical tone positions. These classic resistors add a beautiful warmth and depth to the overall tone of the amp.
--quote

http://www.rockandrolldoctor.com/

http://teixeiraamps.com/index.html

http://www.stu-daddyamps.com/servlet/Ca ... egory=Amps

http://www.sdgvintage.com/amplifiers.html

http://www.destroyallguitars.com/straub/

http://kendrick-amplifiers.com/Merchant ... _Code=0103

[Zippy]

billyz.. i'll stand with ya..

I'll buy into most of what you're sellin', Richie, but sometimes "noise" is "noise". It's not about interpretation of "Do I like it and does it make me wanna tap my toes?", it's a fact of physics.

Whether you like a little background hiss is up to you.

If you have hiss, and crackle or pops..that is unwanted "noise"
if you use a good resistors, then you won't hear that noise.. it will be quiet..

Thanks. We are on the same page.

[Aurora]

I certainly don't want to step on anybody's toes, nor hurt any feelings, as I've come to the conclusion several ears ago, related to HiFI, that it is quite difficult to discuss a personal opinion. If someone claims to hear a sonic difference between this and that, who am I - or we - to say otherwise, particularly when we are not there to hear the same thing , - or not.

From an engineers POV, though there are some good contradictions in several of the referenced links, some obviously based on hearsay and some on the typical urban myths among non technical inclined musicians. Quite a lot of this has it's parallell in the HiFI community.

Some of you may not have seen this - but this is the average engineering POV:
First- resistor noise is mostly dominated by thermal noise - aka Nyquist or Johnson noise - all the same. Any resistor - of any type and value- will produce a noise voltage of U=sqr ( 4kTBR ), where k is Boltzmanns constant, B is signal bandwidth and R is your source resitance.
If we set the bandwidth of a typical guitar amp to 10 kHz, an amp with 1 Mohm input resistance will thus produce an equvivalent input noise voltage of appx 13 uV. Lowering the input impedance to 10kohm will lower the input noise to appx 1.3 uV. Given an average 50W guitar amp having a total voltage gain of 500-1000 at full blast, and allowing extra gain for overdrive, a maximum noise voltage of 13 mV should be present at the output - barely audible at close range. But remember - this is the equivalent input noise level. All additional stages in the amp will add their own part, but at a lower and lower level as you approach the output. The general consensus is that your first stage of amplification always sets the signal/noise ratio - unless there's something seriously wrong underway.
This is a theoretical view - It would be quite interesting if some of you would hook a scope at the output and measure the peak noise voltage of a good, quiet amp.
The Audio Express article seems to exaggerate the difference between CCs and metal films. There is a difference, but experiments have shown that the length/diameter ratio plays a role here. CCs seems to have more 1/f noise, but mainly at subaudible frequncies . See links below.
And- resistors don't have shot noise per se. This is a kind of noise usually associated with semiconductors and tubes.

Now- tube amplifiers are usually high impedance devices, which by nature are susceptible to noise problems. Even though, if severe noise is present in a guitar amp, my suggestion is that there's something wrong, - components, layout..... bad layout can be a source of local instabilites by stray capacitance, - enhanced by the inherent high impedance.

As I've already stated, I'm new to guitar amp building and design, but not to electronics. I read the statements and try to evaluate my own opinions. Time will show if I'm wrong, as I'm sorting out parts for an amp for my son... Xicons and Orange drops, I have quite a collection of NOS parts, too. Metal films, CCs, carbon films, wirewounds and oxide resistors...
----------------------------

A few links from non guitar related sources - more of an engineering view to the problems.

http://en.wikipedia.org/wiki/Thermal_noise

http://www.analog.com/en/amplifiers-and ... s/fca.html

http://www.analog-europe.com/howto/2122 ... SCJUNN2JVN


And finally - the Jung and Marsh Capacitor Bible
http://www.reliablecapacitors.com/pickcap.htm


Best regards

[Aurora]

BTW - the prices now paid for CCs is a hyped up price, based on limited availability and dubious popularity. 30 years ago, 1/4 W CCs were 5 c's and metal films were 50 cents. Today it's the opposite, also partly based on modern production technology......