Resistor Question

[jckid649]

I'm sure this has probably been discussed somewhere on this forum, but for my own interest I needed to ask.

In interviews with Ken Fischer he stated that he found that there were some parts that were not useful for anything: one being metal-film resistors. Yet in every gut shot of "supposed" original Trainwrecks I've seen online, you see metal film resistors all around.

Ken talked about the various stabilities or instabilities of metal film, carbon film, and carbon comp. He then followed this with discussing his philosophy on amp design compared to that of building fighter jets and how the instability of the circuit allow it to do what it does. He likens this in guitar amps to saying that building a similar instability in the circuit is what gives the amp the harmonics we love. Seeing that carbon comp is the most unstable of these it would stand to reason that following this philosophy he would have used those exclusively. Yet not a single gut shot shows any more than 3 carbon comps anywhere in the circuit and none of them used anywhere that would actually affect the voicing of the amps tone. More-so the use of "any" metal film resistors in the circuit at all lead me to one of 2 possible conclusions.

Either Ken was FOS and just said these things to throw people off or B he meant what he said and someone has either put false pics out there or are showing circuits of Trainwrecks that have been modified from Ken's original parts. Either way this leaves much confusion.

Any thoughts on this?

[redshark]

All trainwreck pics have carbon film. No carbon comp or metal film.

[jckid649]

All trainwreck pics have carbon film. No carbon comp or metal film.

Every pic I have seen on this forum has a combination of all three.

[redshark]

Ok, all carbon film in the preamp, some carbon comp in the output stages and other types in power supply. When Ken Fischer talked about metal film resistors not being good for anything he was talking preamp stages where he used carbon film as a middle point between the noisy carbon comp and the sterile sounding metal films.

[Reeltarded]

Yes. It's all about the signal path and not using MF.

There is a good reason to use all MF. Precision.

[M Fowler]

I use MF because it matches my initials MF.

[Reeltarded]

Yeah, and your disposition.

MF.

hah

[M Fowler]

Yeah, and your disposition.

MF.

hah

How true

[jckid649]

Thanks guys, this is all very helpful.

[Super_Reverb]

What are upsides downsides of CF and MF resistors? why should one avoid MF in amp builds?


rob

[prspastor]

Don't Dumble designs use a lot of metal film? Yet they are warm amps, IMO. It all depends on the design. Design carries a lot of weight in my mind - a good example is how Mike Zaite can make 6v6s sound like EL34s in his Remedy amp.

I have to admit, I'm not the skilled builder that a lot of these guys are on this forum and my knowledge may be lacking. But I think that metal film and carbon film are quiet, good resistors. Carbon Comps do have a tendency to distort which can add to or take away from the amp's sound. You have to decide if you want to deal with the shot noise that comes with them.

[M Fowler]

Some of my builds using CC resistors sound so good I swear it has to be the CC's.

My TW Rockets are built using MF throughout and I wouldn't change a thing on those amps.

What works for you is how you approach building amps not internet folk lore.

Mark

[Colossal]

What works for you is how you approach building amps not internet folk lore.

+100. This statement should be posted as a sticky.

Don't drink the cool-aid.

[prspastor]

Mark, in his eloquence, said what I was trying to say in an inarticulate way...

[Colossal]

Mark, in his eloquence, said what I was trying to say in an inarticulate way...

Don't Dumble designs use a lot of metal film? Yet they are warm amps, IMO. It all depends on the design. Design carries a lot of weight in my mind - a good example is how Mike Zaite can make 6v6s sound like EL34s in his Remedy amp.

Not at all PRSPastor, I thought your comment was equally important and the point was taken. Yes, Dumbles use DaleRN65 MF resistors for plate loads (and elsewhere, IIRC). I personally have built 100% MF based amps and have had guys who are not biased (having no knowledge of resistor or capacitor substrates and films, nor circuit design etc) tell me that my amp was very warm and in fact beat out originals for which my build happened to replicate. Moreover, I feel that transformers make a far greater impact (for better or worse) on the overall tone, followed by tubes, then the materials in the signal path.

While I have the utmost respect for Ken Fischer, I have often mused how he might have come to hold some of the views he did such as metal films sounding sterile. Perhaps this was due to the parts and their relative tolerances he had access to at the time plus his own personal experiences with circuit design. Sterility and clarity are very different things too and should not be interchanged. It is quite easy to make a hard, glassy, and sterile sounding amp even with Holy Grail NOS parts; again, more of a referendum on design than the parts.

And yes, run 6V6Ss at 440V slightly cold biased and they sure do take on some of the qualities of EL34s. Killer amps 6V6 Plexis...