Difference between metal film and carbon comp resistors?

[skiraly017]

Sorry if this has been asked before. Could someone please enlighten me? Thanks in advance.

[The Tone God]

The Search function is your friend.

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http://www.diystompboxes.com/sboxforum/viewtopic.php?t=33539

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Andrew

[Paul Perry (Frostwave)]

carbon comp: less stable, and more noise.

[ninoman123]

And vintage mojo.

[Pedal love]

To me it goes as follows:(I know I'm going to get mail)
Carbon comp-best for sound, worst at reducing noise.
Metal film-best at reducing noise, worst for sound.pl

[R.G.]

To me it goes as follows:(I know I'm going to get mail)
Carbon comp-best for sound, worst at reducing noise.
Metal film-best at reducing noise, worst for sound.pl

No mail necessary. The **measurable** differences in these areas are:
(1) metal film has little or no excess noise beyond the pure thermal noise for a given resistance. Carbon composition has the same thermal noise for the same resistance, plus a variable amount of additional excess noise which depends on the exact composition and thermal/mechancal history of the resistor. No resistor reduces noise. You can only use a resistor with less excess noise. Carbon film is intermediate between metal film and carbon comps in this respect.

(2) carbon composition resistors can, under certain conditions have a soft even harmonic distortion of their own due to the voltage coefficient of resistance. See the carbon composition mojo article at GEO (http://www.geofex.com) for the full explanation. This effect only becomes noticeable at quite high signal voltages - upwards of 50 - 100V of signal - and so it entirely inaudible in 9V pedals. You really need a device with a couple of hundred volts for a power supply to see it at all. So no, carbon comps are not best for sound. They're equal to other resistors at small signal voltages.

[Pedal love]

R.G. I misspoke in regards to reduced resistance, but my main statement for me is true. I and other musicians really have to go by feeling and perceived sound, rather than pure theory, sometimes. So in my opinion metal film resistors are dead musically.pl

[Pedal love]

....and R.G. I have great respect for your electronics ability, but when I say it is my opinion,  it shouldn't be taken, any further than that. You can quantify thermal noise in resistors, but you can't quantify sound, making  this man feel, the way he feels, when he hears it.pl

[Ed G.]

I guess that would put the tan carbon film resistors in between.
I read somewhere that Tom Scholz said the human ear can hear things we can't measure yet with equipment. I believe it.

[Doug_H]

I use carbon comp or carbon film most of the time because that's what's available at the store I frequent. At 9v I don't think you're going to hear much tonal difference, although metal film might help with noise in a real high gain circuit.

I don't do listening tests with resistors. (I may have tried it one time a long time ago and didn't hear much difference.) I figure if a resistor type is going to make or break a circuit, I need to go back and redesign the circuit.

Doug

[R.G.]

Let me pre-apologize for being so hard nosed on this one. It took me a long time to run down a rational reason why carbon comps should have ever acquired a reputation for sounding better.

There is a difference in theory and measurement. A purely theoretical set of comments may be incomplete or one may not understand the theory. But there are few half-century old theories that are dead wrong that are left around these days. We discard wrong theories pretty quickly, as soon as they get proven wrong. It was, after all, Albert Einstein who said "God does not play dice with the universe." about the probability aspects of quantum mechanics. Unfortunately, his (highly educated) disbelief of the theory was wrong and the theory was correct.

Measurement is not theory. If you can repeatably measure something, it definitely exists.

And the human mind - yes, the human mind can hear things that we can't measure yet with equipment.  Notice that I said the human mind, not the human ear. Quite a lot of hearing goes on in the human mind, not the ear.

Take the cello for instance. The cello body cannot couple the lowest string fundamental to the air around it well at all. The body couples the second harmonic and above to the air very well. When humans listen to the cello, their *ear* hears the second and above harmonics. The audio processing inside the head inserts the fundamental that is demonstrably not there in the air, recreating it from the harmonics and inserting what it thinks must be there. The mind is correct - there is a fundamental there, but it is a fundamental that it did not hear. The mind inserted a fundamental based on its expectations.

There is a large body of evidence in the areas of hearing, speech recognition, musicology, and so on that the human mind will hear what it expects to hear if it has any expectations of the sound at all. Psychological testing confirms that it is incredibly easy for a human mind to delude itself about hearing and other things. That's why psychologists developed double blind testing - so that not only did the subjects not know what the "expected" results were, the researchers administering the tests didn't either; the *researchers'* expectations were found to measurably change test results when the researchers knew what to expect the subjects to expect!

If one expects a carbon composition resistor (or solid silver wire, or solid teflon PCBs, or enclosures painted in tincture of wolfbane) to simply sound better in some unmeasurable way, then it will - to them. It might even sound better to other people if it makes the person who believes in carbon composition resistors play better.

But hearing and musicology researchers have found whole arrays of things that can affect sound to make it sound subtly "better". F'rinstance: in the classical music era in Europe, the tuning of instruments gradually crept up from an "A" in the lower 400's to the high 400's, in spite of using tuning fork standards. Modern violinists often play solos sharp by a few percent to stand out from the orchestra. And we guitarists think that "clean" sound is better through a vacuum triode, which tosses in a few percent of distortion.

It's even been found that certain cultures don't hear music the same way. There is research that has shown repeatable tests on different human groups that hear musical intervals differently. That's a much bigger difference that carbon composition resistors.

So IMHO, if you can measure it  repeatably, it exists. If you can't measure it repeatably, it may be real and you don't know how to measure it yet; however, it may also be an artifact of the mind hearing what it wants. It takes a lot of work to sort that last one out.

Which leaves us with opinion. Mine is no better than yours, of course.

[formerMember1]

i am gonna order some carbon comp and trop fish caps for my Vox clyde wah, i alread know that current production metal film and metallized polyester are "better" but i would rather more noise. :lol:

The same with a strat, i would rather have the strat hum in certain pickup combinations then have "noiseless" pickups.  

what is good enough for Jimi, is good enough for me.  

Let me add also that I agree with R.G., but i like to know that there are little fishes swimming around in there and i got some extra noise to fill up some room. Analog recording adds alot more noise than digital, but analog sounds better to me, the extra noise makes the listener not here certain frequencys i think.

with digital recording vs analog,
Tape is warmer and better sounding, digital sucks in my opinion, inless you play bubble gum pop music,(not that i am saying anything bad about pop music :wink: ) I just think digital recording sounds more POP.

I also think that old records sound better than CDs.  I don't know why but i hear it. could be i am using an old record player to play the records and a new player to play the CDs and that has to do with the sound, but whatever it is, in my situation i don't mess with something that already sounds good.


hey R.G. i wanna ask ya something

I have heard from people that they think certain color LEDs sound better in certain fender amps and pedals,  
anyway, i was wondering if there is some truth to that, I'll explain...

Cuz if someone makes two identical pedals(say a fuzzface),  one has a efficient LED and the other has not so efficient LED, and they use the same value current limiting resistor for each pedal.  would one pedal sound different than the other cuz of battery drain.  Maybe this has to do w/ different LEDs sounding different in certain pedals?
I don't know about amps though, it seems a few volts if that wont make a difference in an amp, plus it is not run on battery.

thanks

final thought: I think alot of people try too hard to sound better by using certain gear, becuase they can't do it with there fingers.  There has been many times, when i have seen someone play through a rig and say "how it sucks" and how "there must be  something wrong with that amp", etc.. Then someone picks up the same guitar and it sings.

[Ed G.]

So IMHO, if you can measure it  repeatably, it exists. If you can't measure it repeatably, it may be real and you don't know how to measure it yet; however, it may also be an artifact of the mind hearing what it wants. It takes a lot of work to sort that last one out.

Which leaves us with opinion. Mine is no better than yours, of course.

Well said. I can remember on several occassions 'faking myself out' by thinking I changed the value of a component, expecting to hear a change, hearing it, and then I found out the part value stayed the same. Like you said, if you expect to hear a difference, you probably will.
Scientists depend on measurable data. As they should. Most of us here aren't scientists, although we depend on science to make these things work. So I guess the area in between measurable scientific data, and unmeasurable acoustic and psycho-acoustic phenomena, lie the mystique we call 'mojo'

[Paul Perry (Frostwave)]

It's certainly true that most analog tape systems have more 'noise' than most digiatal recorders. but that isn't why they 'sound better' to many people, it's the saruration effect on the tape (and, for first generation digital systems, possibly aliasing filter problems).
Believe me, anyone who could afford to use metal resistors in old tape system electronics did (and we're talking VERY expensive non-inductove double wound wire resistors).
If just adding 'noise' made stuff better, then we would be making noise injectors & plugging them into our gear!
Still, de gustibus, non disputandum est.. www.harshnoise.com  :wink:

Mind you, there is 'dithering'..but let's not go there tonight....

[Doug_H]

I
If just adding 'noise' made stuff better, then we would be making noise injectors & plugging them into our gear!

Yeah, we would just need the "60 cycle hum boost" and "Intermittent Shorter" and we would have everything we need!  :lol:

http://www.angelfire.com/yt3/redtele/

Doug

[RedHouse]

Well they (carbon anything) didn't pass our "Pepsi Challenge" testing.

(recall the old Pepsi blind taste test commercials)

With a few friends I ran some "Pepsi Challenge" style tests on resistors and capacitors in Amps and Effects a few years ago which I've typed up before on this forum (and AMPAGE and AX84) so I won't bother typing it up again at this time (use search) but suffice to say that when an observer listens to a device which they cannot see, or, have no idea what parts are inside, and then is asked to choose which is the "best sound" in our testing no one chose Carbon Comp, only one in 16 chose Carbon Film, the Metal Film was clearly the UNBIASED winner.

As a note to Pedal Love, these were all musicians, some had electronics experience most did not.

When people put on their "critical listening" hats most agree that HISS is a negative virtue, HISS masks true tone, only those seeking MoJo relish the HISS factor, in fact I'd even go so far to say that HISS allows one to read-into a tone something that's not there which can be good for folks that don't have good tone, but for those that do, it has a detremental effect.

Ed G has a VERY good point which I'd like to confirm and reiterate, that when we build devices we all carry huge expectations into the results and  tend to pre-bias ourselves for many reasons.

Some parts are clearly better than others, but often we get cought up in attributes that get attached to parts socially, some dislike new things and tend to hear MoJo in old devices that are clearly made from inferior parts, some are heavily influenced by cost and are certain a 5¢ capacitor sounds just as good as a 95¢ capacitor and you'll never convince thm oherwise ...unless you do the blind testing where they don't get to know which parts you use untill after they make up their mind which sounds better.

Here is some personal opinion that should rile-up the masses, but speaking of MoJo, I was around back in the 70's when Electro Harmonix stuff was new, I remember clearly going to the music stores and trying out their stuff next to other effects of the day (Electric Mistress -vs- ADA, Small Stone -vs- MXR Phase 90, Muff Fuzz -vs- Fuzz Face) and my impression was they sounded cheap and very noisy, just full of HISS. I can't believe how now after 35 years gone by, everyone thinks EH stuff has MoJo, sheesh!

[formerMember1]

Personally I don't like to be made fun of, I was just stating my opinion.

I don't think one could add noise to a circuit the way you guys say and be able to get a better sound, that is crazy,.
I just thought that there has to be something more than what everybody knows about carbon composite resistors,  Personally i think vintage is way better than modern in most cases,

the common factor that i keep coming back to, is no one could replicate the sound of vintage gear exactly or they would DO IT!   I have yet to hear a botique pedal or amp that is better than a good vintage piece. Remember i say good, because alot of vintage stuff did suck too.

please respect my opinion, because it is not like any big rock players are getting any tone to be proud of nowadays.  nothing compares to Hendrix's, Page's, early Van Halen's, The Who's etc... tone.

Some people just can't do it with there fingers, and try to make excuses why...(this is not directed to anyone here :wink: )

[RedHouse]

Whoa, I wasn't making fun of anyone, I was just relating my experience with the resistor types and human beings.

Appolgies if I came off any other way.

[formerMember1]

oh cool man thanks for clearing it up,
you know how it is when someone says something different than what you think sometimes you take offense and you shouldnt. :wink:

anyway, I was wondering what the inductance and capacitance of carbon composition resistors are vs metal film.
I spoke to some people who are electronic fellows and they said that carbon composition resistors are noiser, more susceptible to temperature,  and have higher tolerances than metal film, but carbon composition resistors have way less inductance and capacitance than metal film and also hold up better to power surges. whether that is true or not i don't know, but everybody in electronic stores tells me the same thing.

Anybody could elaborate on this please do. :wink:

i wonder if the temp changes are enough to notice in carbon comps?  Like does temp changes affect carbon composite the same  as temp affects germanium transistors?

Anybody know why carbon comp are still being made today?  I know they are supposed to do something in a amp with high voltage, but that is music, Is there anywhere that they use carbon comp resistors today for anyreason? They certainly aren't cheap compared to metal film and carbon film.

i am gonna do some research on this. :wink:

[formerMember1]

Composite resistors differ from film resistors in that they consist of a little tube with a composite carbon resistor material inside. This makes the resistance, so you only have a few mm (tenth of an inch) of material in the signal. A film resistor is made by carving a channel into a carbon (or metal) film on a glass or ceramic tube, resulting sometimes in meters (feet) of material in the signal!  so carbon composite resistors have less inductance and capacitance, and when you have alot of them, it starts to affect sound.
I wonder if this has anything to do with  composite resistors sounding better?