Let's talk resistors!

[Cliff Schecht]

I find myself running back to my other thread on caps for reference, so I figured a thread on resistors would be good as well. This came about after wondering why a build of mine sounded farty and grainy in the studio the other day. I'm wondering if the carbon film Xicon 1/2W resistors that I've been using for a good while are actually decent enough quality to continue using in my builds. You can get them super cheap and so far I think I've had good luck with them, but I haven't auditioned different resistors in the same circuit to form a more solid opinion.

So what are your favorite carbon film resistors? Have you guys noticed an audible difference (noise, frequency response, distortion, brittleness, etc..) from different CF resistor brands?

For metal film the Dale RN65 stuff is hard to beat. Low noise, no audible effects that I can tell and tough as nails. I've used Xicon MF resistors in the past but actually found them to be brittle sounding compared to higher quality brands.

For carbon comp I stick with Allen Bradley and ICR mostly as this is what's in my stock (also some Stackpole in there IIRC). I'm sure we will get to discussing CC eventually but for now I'd like to focus this thread on CF resistor types and opinions.

[Gaz]

Besides noise, they all sound the same to me - Seriously. Maybe i'm not cut out for this I don't like the really thin leads on the 1/2 W Xicon stuff, but the price is hard to beat. Then again, they're nice for wrapping many leads around a turret. I really don't think the Xicon Metal films sound brittle though, and that can always be compensated for without tonal compromise, IMHO. One man's 'brittle' is another man's 'articulate'.

[Lonely Raven]

On the Tweed Champ and Blackface Champ amps I built, I found the thicker 1 watt resistors seemed to have less...."hiss" compared to the same 1/2 watt resistors.

Beyond that, I have no other suggestions. I'm doing some testing of resistors myself in a future Tweed Deluxe build. I bought four or five different types of resistors including some audiophool ones to see what I see.

[billyz]

Cliff,

Here is a little experiment for you . Try using a magnet on each of your resistor types/brands. Then associate those results with what you hear. The Dale resistors are non magnetic, so are the CC allen bradley , stackpole, IRC etc. Those cheap film types are almost always magnetic. In my experiments , I find it does affect the sound quality, and it does add up the more you have. Takeman CF resistors are non magnetic and sound quite nice.

Every time I get a harsh sounding amp in , I find loads of CF and MF resistors all magnetic types. You would think if an amp cost 2-3K it would have a few dollars worth of better quality resistors, most don't.

Many times I have replaced the cheap MF and CF resistors ( in key places) with cheap CC xicon and the amp sounds better and just as quiet .

[Andy Le Blanc]

The things are rated by noise and thermal coefficients and failure rates

the comment about the non inductive types is interesting

A guitar amp isn't usually associated with "critical" applications requiring
special scrutiny for resistor type, that's more a requirement for HI FI .

But sound relies upon the weakest link, where in a guitar amp would it best
to invest a non inductive type, plates?, any resistor directly in the signal path?

[echuta13]

There's a good discussion going on over @ AX84 on the subject: http://ax84.com/bbs/dm.php?thread=443855

I use CF 1watt rated resistors in locations that are not in the signal path. I use MF's on plates & any locations within the signal path though (RN65's).

[billyz]

Since this is a discussion about CF and MF type resistors I don't want to derail Cliff's topic with the merits of CC types. I have found that the inductive, magnetic resistors to be harsher sounding than the premium ones like Takeman, PRP, , Dale, and others. I do think the plates and signal path(grid and screen) locations benefit the most.

Ok, I can't resist ( pun), I just rebuilt and modded a 62 Bassman . The Bass channel got the treatment and a bit of the power amp ,PI too. A high gain mod, I used all CC resistor, even the power supply and screen grids. This amp was the quietest amp I have ever heard or not heard. I thought I had screwed up when I flipped the standby and could not hear a thing. But she is a screamer when you hit a note, it is all there in spades.
Prior to the rebuild it was loaded with MF and Metal oxide on the screens and PS and was very noisy.

I think resistor choice is like your choice of beer. Some people are happy drinking Bud and others prefer a premium German lager( or great homebrew). Maybe it is an acquired taste.

[Zippy]

Ok, I can't resist ( pun), I just rebuilt and modded a 62 Bassman . The Bass channel got the treatment and a bit of the power amp ,PI too. A high gain mod, I used all CC resistor, even the power supply and screen grids. This amp was the quietest amp I have ever heard or not heard. I thought I had screwed up when I flipped the standby and could not hear a thing. But she is a screamer when you hit a note, it is all there in spades.
Prior to the rebuild it was loaded with MF and Metal oxide on the screens and PS and was very noisy.

Is that all that you changed or did you rebuild the power supply (caps) at the same time?

Did you opt for oversize (ie. 1W vs 1/2W) CC's?

I think resistor choice is like your choice of beer. Some people are happy drinking Bud and others prefer a premium German lager( or great homebrew). Maybe it is an acquired taste.

I just had a great Citron IPA at Santa Fe's Second Street Brew Pub - no need to develop a taste for great beer!

[billyz]

Ok, I can't resist ( pun), I just rebuilt and modded a 62 Bassman . The Bass channel got the treatment and a bit of the power amp ,PI too. A high gain mod, I used all CC resistor, even the power supply and screen grids. This amp was the quietest amp I have ever heard or not heard. I thought I had screwed up when I flipped the standby and could not hear a thing. But she is a screamer when you hit a note, it is all there in spades.
Prior to the rebuild it was loaded with MF and Metal oxide on the screens and PS and was very noisy.

Is that all that you changed or did you rebuild the power supply (caps) at the same time?

Did you opt for oversize (ie. 1W vs 1/2W) CC's?

The Power supply had New caps already, Sprague atoms, but several of the power supply Resistors had been changed to Metal Oxide 2W. I changed them to the stock 1W in the power supply. 1W for the Screens and the rest are 1/2w, except for the V1a/b I used 2 ea 1/2 CC for the plate( parallel). So technically it is 1w. I know I may get a queer look for changing the PS from 2w to 1w CC, but I really wanted to see/hear the difference. I have never really had a problem with 1W CC 's in an old fender PS. And I prefer the 1W screens to act as a fuse too. I did add the 1.5k grid resistors to the 6l6's . I changed the NFB to Marshall specs. Also, an adjustable bias supply.

I just talked to the new owner and he loves it with his Les paul.

[tubeswell]

MF are quieter than other types, but also running resistors with higher power ratings of the same type is quieter. In any event, you tend to notice the hiss in the noise floor more with high gain amps. I honestly have not noticed much difference in CC, CF or MF in low powered amps, except that using MF is less hissy overall. And in this regard, getting the signal:noise ratio low is most important in V1.

CC probably have the most effect on harmonic distortion in the PI slot (according to R.G. Keen) - because of their voltage gradient characteristics (impedance rate of change alters the higher the voltage is). If this produces an effect it must be subtle compared to eth other types of distortion going on, because I honestly find it hard to tell the difference. (But I rarely ever run my amps that hard these days, so I guess never hear the subtleties enough).

Smaller resistors also tend to breakdown at lower voltages (Those little 0.6W MF break down at about 360V IIRC).

What does this all mean? I think, in a nutshell, if you use bigger resistors they will tend to be quieter and last longer. JM2CW

[M Fowler]

I've only built one amp a Marshall 18w two channel with all CC resistors, it sounds great I wouldn't change a thing.

Billy when I finally get around to that Princeton project we talked about I plan to go all CC with that as well.

I am looking for long lead CF but they are hard to find or I am looking at the wrong vendors, LOL.

Mark

[billyz]

I've only built one amp a Marshall 18w two channel with all CC resistors, it sounds great I wouldn't change a thing.

Billy when I finally get around to that Princeton project we talked about I plan to go all CC with that as well.

I am looking for long lead CF but they are hard to find or I am looking at the wrong vendors, LOL.

Mark

Did you try Parts Connexion ?

[M Fowler]

I did look there but I thought they were very high priced or I am cheap?

[overtone]

..Smaller resistors also tend to breakdown at lower voltages (Those little 0.6W MF break down at about 360V IIRC)...

Tubeswell, I did not understand: breakdown at lower voltages? I don't use those kind of resistors, but I would like to understand what you mean.

[tubeswell]

..Smaller resistors also tend to breakdown at lower voltages (Those little 0.6W MF break down at about 360V IIRC)...

Tubeswell, I did not understand: breakdown at lower voltages? I don't use those kind of resistors, but I would like to understand what you mean.

Sorry, I should've perhaps said something like 'maximum voltage handling capability', or 'maximum rated working voltage'. (BTW the size generalisation doesn't always hold 'true' in this modern age. I was thinking about 'traditional' (i.e.: CC, CF, MF) types of resistors when I typed that.)