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Thread: Carbon Film or Metal film resistors

  1. #1
    Forum Member Toneseeker's Avatar
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    Carbon Film or Metal film resistors

    Hi Guys.

    I need your opinions on resistor choice for new amp builds.
    I know high wattage 1% metal film is probably best for Power supply etc but what about the signal path? Is there really much difference sonically between Carbon Composite, Carbon Film and Metal Film.

    Pete
    Failure is simply the opportunity to begin again, this time more intelligently.

    Henry Ford

  2. #2

    Re: Carbon Film or Metal film resistors

    http://www.aikenamps.com/ResistorNoise.htm

    Short of needing to prevent forest fires, it's all in your head! ;-)

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    Forum Member Toneseeker's Avatar
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    Re: Carbon Film or Metal film resistors

    OK, I found something which pretty much answers my question but feel free to add your comments guys. This is from the maker of Budda amps:

    While 1% metal film resistors may, and I say MAY, be a good thing for hi-end stereophyle equipment, I'm really not a big proponent of them in guitar amplifiers. Sometimes too much of a good thing is bad. Things like polypropylene caps and even silver solder to me make a guitar amplifier sound too sterile. For me, a good guitar amplifier shouldn't sound like a stereo amplifier. If it were me, that was going to go thru the time and expense of changing out the resistors in my amplifier, I would probably go with 1-watt carbon film resistors. 1-watt resistors are far more capable of handling the operating voltages in a tube guitar amplifier than the half watt and even quarter watt resistors that are used in most guitar amplifiers, and in my opinion less likely to generate noise because of this. This is the reason we have always used 1-watt resistors in all of our Budda Amps. As far as the distortion caused by carbon as opposed to metal film, I can't really confirm or deny that thru personal experience, but if carbon resistors are responsible for the tones generated by some of my favorite amplifiers of all time, than "Give me Carbon!"

    Remember... we're ALL carbon-based.

    Pete
    Failure is simply the opportunity to begin again, this time more intelligently.

    Henry Ford

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    Forum Member Kap'n's Avatar
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    Re: Carbon Film or Metal film resistors

    Most builders whose opinions I respect only use carbon comps because their customers believe in the mojo effect.

    They would use carbon or metal film resistors in amps they would build for themselves.

    Carbon comps are noisy and they tend to drift. When other technologies became available, the industry switched. Nobody uses bias-ply tires either. And nobody uses a spark-gap oscillator for their tremolo either.
    Several guitars in different colors
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  5. #5
    Forum Member Toneseeker's Avatar
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    Re: Carbon Film or Metal film resistors

    Yeah, I agree with the comments re carbon comp resistors drifting and being noisier than other types. I think the carbon film types are a compromise but what I want to know is: Is there a significant/noticeable tone difference between carbon film and metal film resistors. I would not hesitate to use metal film resistors in non signal path positions, however if I use metal film resistor for the grid stoppers instead of carbon film would that affect the tone in a negative way?

    Pete
    Failure is simply the opportunity to begin again, this time more intelligently.

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  6. #6
    Forum Member Kap'n's Avatar
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    Re: Carbon Film or Metal film resistors

    There is no reason to use carbon composition resistors anywhere in an amplifier build, unless your customer is willing to pay you more because he believes it's better.

    Carbon comp resistors are the audiophool's world of mojo, transferred to guitar amps.

    Other audiophool stuff for guitarists.

    Linear crystal wire (anybody remember this stuff?)
    Silver wire/solder
    Monster Cable
    Groove Tubes
    Several guitars in different colors
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  7. #7
    Forum Member Toneseeker's Avatar
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    Re: Carbon Film or Metal film resistors

    I guess that answers my question Kapn.
    I'll stop worrying about not being able to source certain values of resistor in Carbon Film for my project.

    Thanks

    Pete
    Failure is simply the opportunity to begin again, this time more intelligently.

    Henry Ford

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    Forum Member ampdan's Avatar
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    Re: Carbon Film or Metal film resistors

    Kapn' I totally agree with you on this...

    "Other audiophool stuff for guitarists.

    Linear crystal wire (anybody remember this stuff?)
    Silver wire/solder
    Monster Cable
    Groove Tubes"

    But I have to disagree with this...

    "There is no reason to use carbon composition resistors anywhere in an amplifier build, unless your customer is willing to pay you more because he believes it's better.

    Carbon comp resistors are the audiophool's world of mojo, transferred to guitar amps."

    I have built dozens of amps, and there is most DEFINITELY a difference in the sound/tone/warmth/definition of amps built with carbon comps, vs carbon film etc. I also hear a difference between PIO, polyester, polystyrene, ceramic capacitors. You can call it "mojo", but I hear the difference.

    But, YMMV blah blah blah...

  9. #9
    Forum Member Don's Avatar
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    Re: Carbon Film or Metal film resistors

    Quote Originally Posted by Kap'n View Post
    Nobody uses bias-ply tires either.
    'course they do! Radials don't look right on a hotrod, plus radials don't have "the tone" when you peal out!

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    Re: Carbon Film or Metal film resistors

    Crank up an amp with a band and no one can hear a difference between capacitor types.
    Last edited by JAM; 02-09-2008 at 07:28 PM.

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    Re: Carbon Film or Metal film resistors

    Toneseeker, you are just down the road from me, hi.

    The proof is in the pudding, right.
    Being an electronics engineer for 10 years and a life long guitarist, I have always been able to have arguements with myself regarding topics like these.

    Logic versus soul.

    What I'm saying is try it and see, but be careful.

    Add your CCs to your amp then try it. Leave it a day or so then try it again. leave it another day, try again. If the results are the same each time and you like then you're right. I find that sometimes when I play my guitar its sound different and I haven't touched a thing.

    Oh and by the way. I changed all my plate loads in my Hot Rod Deluxe to CCs three weeks ago and noticed a significant difference, especially on the drive channel. Gone were all the harsh overtones I disliked and now I'm getting smooth creamy browness.

    Go for it, it isn't difficult to swap them for sterile CFs if you hate the CCs.
    Good luck

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    Forum Member Offshore Angler's Avatar
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    Re: Carbon Film or Metal film resistors

    It's REALLY hard for a linear device to have mojo or much effect on tone.
    "No harmonic knowledge, no sense of time, a ghastly tone, unskilled vibrato, and so on. Chuck is one of the worst guitar players I know" -Gravity Jim

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    Re: Carbon Film or Metal film resistors

    Haven't you heard of voltage coefficient?

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    Re: Carbon Film or Metal film resistors


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    Forum Member NTBluesGuitar's Avatar
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    Re: Carbon Film or Metal film resistors

    Whoa... resistor distortion. Interesting.

    JAM, you always find the good material to read on.
    "...pray do not imagine that those who make the noise are the only inhabitants of the field;
    that, of course, they are many in number; or that, after all, they are other than the little,
    shriveled, meagre, hopping, though loud and troublesome, insects of the hour."

    -Edmund Burke

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    Forum Member boobtube21's Avatar
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    Re: Carbon Film or Metal film resistors

    Quote Originally Posted by bigtuna View Post
    Haven't you heard of voltage coefficient?
    Bigtuna, you just opened a big can of worms.

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    Re: Carbon Film or Metal film resistors

    Well done JAM, I was going to post that link last night but wrongly assumed everyone would know this. LOL.

    Hope this has brought some elightenment and new interest to some.

    Let's face it, if you don't like the sound of CC's, just change them.
    Personally, I think it's the best mod I've done to my HRD yet and the cheapest!

  18. #18
    Forum Member cdw2000's Avatar
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    Re: Carbon Film or Metal film resistors

    For me, personnally, I HATE hiss. Metal Films are much quiter from a noise point, so I use them exclusively in most of my audio circuits, especially in high gain circuits.

    But I also think the geofex article JAM linked to provides a very well reasoned discussion on CC mojo. Hmmm...I may now try one for the plate resistor of my final 12AX7 stage in my scratch-built amp.
    "Time is an illusion, lunchtime doubly so" -- Douglas Adams
    "If something has a 1 in a million chance of occurring, 9 times out of 10 it will happen" -- Terry Pratchett

  19. #19
    Forum Member Toneseeker's Avatar
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    Re: Carbon Film or Metal film resistors

    Hi Bigtuna,

    you have opened a quite old thread here and as Boobtube21 says, a can of worms. My Hot Rod Deluxe has now been reborn as 5F6-A Bassman. I used 1 Watt Carbon films throughout except on the power supply where I used 3 Watt Metal film resistors. I now have the amp I was looking for when I began modifying the HRD.
    Edited:
    Actually you have opened quite a few old threads. (and maybe inadvertently ruffled a few feathers). I take it you are new to the site.
    I was also an electronics engineer (RAF - Flight Simulators). Thought I knew it all till I found this site. The guys here are amazing and I've learned a lot from them. In IT network support now but I still like to dabble. You say I'm just down the road from you ?
    Where you at ?? Cool Website BTW.

    Pete
    Last edited by Toneseeker; 05-20-2008 at 06:13 AM.
    Failure is simply the opportunity to begin again, this time more intelligently.

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  20. #20
    Forum Member ziess's Avatar
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    Re: Carbon Film or Metal film resistors

    I love those GeoFX pages.

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    Re: Carbon Film or Metal film resistors

    Hi Pete

    Been away for a while, just read your post.
    Yes, I must apologise if I have 'ruffled a few feathers'. It certainly wasn't intentional. It's so easy to type away and post without full consideration of the effects. I know all these guys have a lot of experience. I am not new to the site, just to posting, I have followed a lot of threads, without comment, for quite some time. So more apologies to all.

    Thanks for the comments on the site. I am Fife based (that's all I'll say incase I've got a hate mob now - I hope not).

    Regarding the original point in question, all I know is that I changed the resistors and it made it sound better to me and no-one can argue with that really. I guess I was just curious to see how many people knew the fundamental reason behind what I said or even if they had actually tried it themselves?

    BT

  22. #22
    Forum Member NTBluesGuitar's Avatar
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    Re: Carbon Film or Metal film resistors

    If it sounds better to you, then ROCK ON!



    Opinions aside, that's what's most important.
    "...pray do not imagine that those who make the noise are the only inhabitants of the field;
    that, of course, they are many in number; or that, after all, they are other than the little,
    shriveled, meagre, hopping, though loud and troublesome, insects of the hour."

    -Edmund Burke

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    Forum Member boobtube21's Avatar
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    Re: Carbon Film or Metal film resistors

    I don't think any feathers were ruffled, we're an easy-going bunch.

    BTW the "can of worms" I was referring to was the technical debates that sometimes kick into gear around here; add to that the fact that the tonal difference between resistor/cap types may or may not be totally subjective.

  24. #24
    Forum Member boobtube21's Avatar
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    Re: Carbon Film or Metal film resistors

    Ok, reading JAM's link, I suppose if it's measurable then there is a difference, however I must agree with his earlier statement that with a live band it would probably be hard if not impossible to tell the difference with your own ears.

    Some frequencies I think become "lost" once other instruments are playing, whether overpowered by the other instruments, or tuned out by the human mind. I've noticed that some slight icepick-ness in one of my amps goes away when I play along with a recording. I know, that doesn't really make any sense, but it's true.

  25. #25
    Forum Member yankeerob's Avatar
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    Re: Carbon Film or Metal film resistors

    I've read JAM's link which was quite interesting - I join TJ in lauding his uncanny ability to find this stuff!! This is how I've come to view things...

    Mojo - or not - I've always took a more engineered approach to electrical or electronic endeavors and elected for consistency and reliability in selecting components - and that's exactly what I get out of my amps (the few I've made anyway )... in fact I'm amazed at how quiet (insignificant levels of hiss or hum) and consistent they are... for example on my HR5F6A I just set all the tone controls to 12 oclock, crank the normal vol full up and start with the bright vol halfway (the inputs are linked via a mini-toggle as I've just one input for each 'ch') and use it as a variable treble boost of sorts that varies depending on the room - but I never think 'geez, it doesn't quite sound as good as it did last time'... I've used quite a few different set-ups in 34 yrs man and boy - but this is the most consistent - and only varies according to what guitar I've got plugged into it, where the vol is set on the guitar and how hard or soft I play - and if I want more than the crunch it gives me when the guitar's full up the BlackStar HT-Dual DS-2 does a good job of giving me a bit more gain/distortion at two different preset levels (but still based on sound I started with) - it has a 12AX7 running at 300V and behaves like an amp when you roll the guitar vol back - worth every penny of 139 GBP AFAIC...

    I've used 2W MF's all around the power supply, 3W MF's for the grid stoppers and 1 and 2W CF's everywhere else - this may go against what's presented in Joe's link but my concerns were more about the effects of long term thermal cycling than 'tone'...

    At the end of the day it might not sound like it was born in the delta - but it's got enough sauce to warm your cockles and more importantly - to me anyway - I'm not worried about it blowing up anytime soon
    If I could find a road to get away it wouldn't be too soon....... Shipwreck Moon.......

  26. #26
    Forum Member cdw2000's Avatar
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    Re: Carbon Film or Metal film resistors

    Quote Originally Posted by boobtube21 View Post
    Some frequencies I think become "lost" once other instruments are playing, whether overpowered by the other instruments, or tuned out by the human mind. I've noticed that some slight icepick-ness in one of my amps goes away when I play along with a recording. I know, that doesn't really make any sense, but it's true.
    Actually, this is not so farfetched as you think. If you research how MP3 file compression is done, you will find that "frequency masking" is one of the techniques employed - "redundant" frequencies from a lower volume sound source are masked out of the waveform. MP3 compression agorithms rely on alot of psychoacoustic phenomena like this.
    "Time is an illusion, lunchtime doubly so" -- Douglas Adams
    "If something has a 1 in a million chance of occurring, 9 times out of 10 it will happen" -- Terry Pratchett

  27. #27
    Forum Member yankeerob's Avatar
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    Re: Carbon Film or Metal film resistors

    I thought I'd resurrect this thread instead of starting another in the light of a couple amps that have wandered into the workshop - one's a Germino Rockgrinder 55 (ser no 001) and the other's a Roccaforte HG100 - the Germino has CC's throughout and the Roccaforte CF's - the Germino in for repair - the Roccaforte in for a send/return mod... If had to choose which of these amps to tour with it'd be the Roccaforte in no uncertain terms - it has tone in spades and is built like the USS New York - whereas the Germino has CC's in places that are just stupid - like the series resistor feeding the bias HWR from the B+ (the tube rectifier has been replaced with silicone by GG himself) - now replaced with a MF for stability... also the Roccaforte has all of the wires wrapped around the turrets whereas the Germino's are fed through the back of the turrets - I don't know if this practice has changed but it's something I decided never to do again on my first build and an absolute ball-ache - having to remove the wire from the back and clear all the solder out of the turret, restrip/tin the wire, insert the component and reflow the solder - do that a coupla times and you'll be growling about it as the minute hand speeds around the clock... if you're in the market for a good Marshall clone I'm not necessarily knocking Germinos (they may have changed - it is after all - ser no 001) but I can't recommend Doug (Roccaforte)'s work enough - it's top notch - good solid design and build - does Marshall better than anything else I've ever heard
    If I could find a road to get away it wouldn't be too soon....... Shipwreck Moon.......

  28. #28
    Forum Member Cygnus X1's Avatar
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    Re: Carbon Film or Metal film resistors

    I have put in CC's in various places along the signal path on both the 5E3...and the SEL. No difference in tone to my ears. Just a bit more hiss. And one irritating popper/crackler!

  29. #29
    Forum Member yankeerob's Avatar
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    Re: Carbon Film or Metal film resistors

    Well the update on the Germino (basically a JTM45) is that he's used an 50uF/50V electrolytic/1K5 resistor for the cathode on the first half of V1 and then what looks like a (rather cheap looking) .68uF/250V poly cap/820Ω on the second half cathode - both commoned to the same ground... curious - only in that I haven't seen this done before - any comments?
    If I could find a road to get away it wouldn't be too soon....... Shipwreck Moon.......

  30. #30
    Forum Member Cygnus X1's Avatar
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    Re: Carbon Film or Metal film resistors

    I would guess it was a gain/tone mod.

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