What would be the effect of changing plates resistors from..

[leadfootdriver]

Carbon Film to Metal Film?

Would there be an appreciable effect on tone?

[Tom Phillips]

I feel safe to say that there would not be an appreciable tone change.
Probably not a noticeable change either assuming that the changed out resistors were not defective.

[Justin Thomas]

What are you trying to fix? Only differences I've ever noticed from resistor swapping was either removing carbon comps from amps that lived in swamps (noisy as all hell) and old carbon comps that are off by 40% or more (major weak signal). If it ain't broke, don't break it.

Justin

[Chuck H]

There may be a small tonal difference if you swap out an entire preamp. IMHO/E there is. Not a better or worse thing. Just a tad different. Much more noteworthy is noise. CC resistors typically suffer from significant "shot" noise (HISSSSSSSSSSSSSSSSSSS). Some metal films are a little quieter than others. I'm told it also helps to over rate them a bit. In a high gain amp changing the first gain stage triode from CC to a good, over rated metal film is said to improve noise regardless of humidity. Since the gain from the second stage forward is significantly lower you might not notice any difference in those circuits. Some of this is just me regurgitating stuff I've read on the forum here.

[JoeM]

We're not discussing CC vs MF, but CF vs MF. Not a change worth the effort, unless you need the lower noise of MF, maybe in a high gain amp.

[Chuck H]

Ah. Right. It's most often the CC vs. MF question. Had my horse blinders on I suppose. I've never worked with CF. Always seemed like a mediocre choice for a personal build. No CC mojo and not as quiet as MF. I guess Ken Fischer (TrainWreck) liked them. Nearly all guitar amp pots are made with CF and I've never noticed a difference when substituting adjustable circuits as hard wired with MF fixed resistors. That's about all I can report.

[daz]

Really Chuck? That surprises me because i always thought most people use CF for thier builds. I always heard MF was only used by most where noise was a big issue or in PSU's but most seem to use CF for the signal path. I was under the assumption from all I've read that MF wasn't as good sounding in general. Also seems like manufacturers use CF most of the time to. So you use MF for everything?

[Chuck H]

I use to use CC resistors in the signal path and MF for HV circuits. I did this because I didn't know enough about my resistor choices to conclude that CC didn't contribute something but they were known to be noisy in certain circuits. Since then I've taken to using MF entirely and I haven't noticed any objectionable changes for the omission of CC resistors. But what about CF? Well, I have an opinion on that and corrections will be humbly accepted. I think the reason they are common in manufactured amps is simply that they are less expensive than MF and don't exhibit the same degree of problems that CC resistors do. In other words, they're "good enough" so why spend an extra three to five dollars per amp on MF resistors? So, if mediocrity is your goal then CF is your resistor.

[daz]

I tried some CC on my preamp plates a couple years ago and i couldn't rip them out fast enough. So if you didn't notice any difference in CC and MF, i suggest that maybe, probably not but maybe CF actually might sound better to you than MF or CC. In other words, if you feel there was not difference in tone between MF and CC but haven't built an amp with CF, maybe you're missing something? Cuz i gotta tell you, those CC's on my preamp plates sounded very noticeably worse. And i tried them a few times over the course of months or a year for a reality check.

Oh, by the way....you won't believe this. But i bought a modeling amp ! I bought a limited run LP i thought would be awesome but i didn't like it and returned it to guitar center for a refund. But when i tried it in the store it sounded great and i was plugged into this fender digital modeling amp called a mustang. So i thought about how that guitar sounded thru it and i researched it online only to find a lot of people swearing up and down it not only sounded great but FELT like a tube amp. So i figured what the heck....4th of july coupon for $50 off and i had a $20 card the gave me the day before so i bought the 100 watt one for about $280 out the door. Been playing around with it and programming it to get the best tone i can out of it and even in the particle board cabinet with a chinese celestion 100 that i am very familiar with and pales compared to my EV in my home brew's pine cab it feels and sounds far better than any modeler i've ever played. Well, maybe not FAR better sonically, but feel wise it's miles ahead. Even has bias (as in the effect of hot vs cold bias) and sag controls that really do what they say. I'm going to make a cable to hook it up to my EV so i can take that celestion and particle board crap out of the equasion. Later i may put a jack on my amp so i can insert the mustang's signal into my EL34 output section along with the speaker and pine combo cab. I have a feeling it will be amazing. I may eventually begin to hear/feel the digital reality of it in time an tire of it. But i'm really surprised at how far they have come in just the last year or 2. This is the first modeler i ever played thru that feels the same as a tube amp. In fact, better than most IMO. It compares to mine and as i've said in the past, i feel mine is better than any MV marshall i ever owned.

[Chuck H]

I tried some CC on my preamp plates a couple years ago and i couldn't rip them out fast enough. So if you didn't notice any difference in CC and MF, i suggest that maybe, probably not but maybe CF actually might sound better to you than MF or CC. In other words, if you feel there was not difference in tone between MF and CC but haven't built an amp with CF, maybe you're missing something? Cuz i gotta tell you, those CC's on my preamp plates sounded very noticeably worse. And i tried them a few times over the course of months or a year for a reality check.

I use to use CC resistors in the signal path and MF for HV circuits. I did this because I didn't know enough about my resistor choices to conclude that CC didn't contribute something but they were known to be noisy in certain circuits.

I've never used CC on plates (I have had them in vintage amps though). That's why I wouldn't have heard a difference. I didn't compare them in HV circuits where I used MF since CC are known to be noisy there. However... I did replace some CC plate resistors in a vintage Marshall with MF and the tone was awful. Too hard and crisp. I guess those tales of CC's compressing are true, but it only matters in certain circuits and those are the ones that will suffer too much shot noise. I say use the better parts and voice the amps to work with those parts. Mojo free operation.

[Gingertube]

The Carbon Film was/is often used for their voltage rating - you have to use a higher wattage Metal Film to get the same voltage rating.
Most of the lovely 0.6W Metal Films are only rated to 350V, use 2 of those of 1/2 the required value in series, or go to a 2W metal film. This later (the 2W) will help with noise too.
Cheers,
Ian

[Chuck H]

Nice. I did look into typical voltage ratings for resistor types once upon a time. No retention on it though.

R.G. has a geofex on the distortion characteristics of CC resistors: http://www.geofex.com/article_folder...carboncomp.htm

Maybe this explains a bit about the mojo (Or would it be science now that it has been explained?).

I wonder if carbon film resistors possess any of the same characteristics. It's still the resistance of a mass of carbon after all.?. Maybe not. I'll look into the voltage rating of CF resistors and see if THAT may be the reason for their prominent use in production amps.

I've been using 1/5 watt rated MF for plates forever without an issue. Maybe I looked into their voltage rating, and maybe I didn't. Hmmm.?. I'll need to look into that too then. But not tonight. It's 11:30pm here on the west coast US. I need to wind down. If I get all nerdy I'll just wind myself up and I need to sleep soon-ish

[daz]

Do what I'm doing now...closet the tube stuff, forget about resistors and caps and cathode bias vs fixed and all that time wasting stuff and get a fender modeling amp ! I swear, after a few days of learning the settings intimately i have this thing literally FEELING as responsive as mine or any MV amp i ever had, and the tone is equal to about anything i've ever played. I'm shocked, but i swear to you digital modeling has finally arrived. I'm not kidding. They finally figured out the response/feel but good ! And if you question my experience with them, i've played thru many and had several effects units that also had modeling. And till i got this thing on a fluke i'd have just laughed at this post. I'm not the only one by a long shot saying this. A lot of tube snobs have found the same thing and did a 180 after a lifetime of tube fanaticism. I knew nothing of any of this tell i happened upon this amp by accident while trying LP's and was amazed enough to do some research.

[Jazz P Bass]

What is the Fender amp model#?
Daz, this is shocking news!
All of the this & that you have gone through......
A modeling amp.
Huh.

[daz]

What is the Fender amp model#?
Daz, this is shocking news!
All of the this & that you have gone through......
A modeling amp.
Huh.

http://www.sweetwater.com/store/deta...OzeRoCKPLw_wcB

I know, crazy huh? I'm not stupid enough to suggest you all run out and get one and toss your tubes. But this is the first time ever i played a modeler or SS amp when i start playing and within seconds i just forget what i'm playing and think i'm playing thru a tube amp. You can adjust the sag and "bias" and it honestly responds like a good tube amp. I would say as well as mine, maybe better. The feel/dynamics has me getting into the zone more often because it responds so well, and i find myself playing for hours a day.

According to all i've read there are other modelers now that are as good or even better, tho to a subjective degree from what i gather. There are a lot of tube guys discovering that while they slept something changed and the game is now turning. If this thing turns out to be as good as i now feel it is, it would be the no brainer go to amp to gig with. 35 Lbs, more sounds and effects than is sane, seems very well made compared to other SS fenders and reliability seems great from my research. You can get a 4 button footswitch ($59) for all sorts of programmable functions and still use the up/down 2 button that comes with it simultaneously which also is programmable to do other things. The bigger 2x12 150w combo comes with the 4 button and has stereo power amps ! That would be the one to gig with actually. Also comes in a head.

But all that said, you know how it goes.....one day X is awesome, the next X sucks and Z is awesome. So i'll reserve final word on this thing for a later date. At this moment however i have no desire to play my tube "project" anymore and it's going in the closet. Last time i plugged into it i wanted to plug right back into the Mustang. Don't get me wrong, it's got what i feel is the best master volume/cascaded preamp OD i have owned. But the mustang can do that almost as well (i think it does the feel/dynamic thing AS well if not better) and a lot more tones mine can't do at all. You want a vox? Its there. Marshall....fender.....name it, it's there. But the big news as far as i'm concerned is the feel/dynamics. Nothing in the past even approached what i get from my amp or any other good tube amp. They always had that sterile tinny high end with no give at all.