RN65 metal films are they really that much beter ?

[Phil_S]

The place to use CC's is where there's big signal - plate resistors, and ideally the stage just before the phase inverter. The phase inverter would otherwise be ideal, with plate resistors carrying the highest signal voltage in the amp, but phase inverters are often enclosed in a feedback loop. The feedback minimizes the distortion the resistor generates.

It seems I don't understand what Keen is saying here. What does he mean by "...big signal - plate resistors..."? If he's not talking about plate load resistors, what is he referencing? This seems to run counter to what everyone is saying. Please clarify this. Thanks.

Phil

[dobbhill]

I think he means the plate resitors with the most signal content would be the best place to experiment-latter stages of the amp.

[Chappy]

The place to use CC's is where there's big signal - plate resistors, and ideally the stage just before the phase inverter. The phase inverter would otherwise be ideal, with plate resistors carrying the highest signal voltage in the amp, but phase inverters are often enclosed in a feedback loop. The feedback minimizes the distortion the resistor generates.

It seems I don't understand what Keen is saying here. What does he mean by "...big signal - plate resistors..."? If he's not talking about plate load resistors, what is he referencing? This seems to run counter to what everyone is saying. Please clarify this. Thanks.

Phil

His theory does sort of go against popular opinion of placing the carbon comps on the plates of the long tailed pair. However, the feedback loop doesn't completely remove all of the distortion in the forward path at all frequencies. Presence controls on the bassman/marshall circuits actually let you adjust the amount of feedback for the higher frequencies. As well, once you really start distorting the forward path with the the volume knob up high the feedback is not capable of keeping up and negating the distortion. I've seen this on a scope while experimenting with a JMP 50 and some homebrew amps.


I guess you could put the carbon comps on the long tailed pair plate resistors, and the plate of the second stage in the preamp.
Chappy

[ckpop]

Back to the original question do metal film resistor sound better then CC ? the answer in my opinion is no. Can you build a good sounding amp with them...... Yes. You just won't have the quailitys you get with CC's and it all depends on the final result you are shooting for.

It kind of works both ways because I have seen guys build marshalls with all carbon comps instead of CF and to me it seemed too much. The originals never used all CC. Anyone correct me if I am wrong.

Resistors are like different signal caps and its a matter of the correct overall balance of the design and other parts used in the amp that work together or against each other. I'm not sure if that makes sense to most but here is another example.

Don't judge this by the amp because it's not you thing but My understanding is Soldano built around PVC polyester signal caps and The sovtec 5881's of that time.

Some people build then change out parts to make an amp sound better and others already have certain parts in mind and build around them.

Just a couple of ways to skin a cat

[Structo]

Yeah, it's strange that some of the Metro amp fellas install a carbon comp kit in their builds.
But like you said, I don't believe Marshall ever used them.
They had carbon film which is much more stable.

I don't think metal film resistors sound better, but what you won't hear is noise that can be generated by carbon comp resistors.

Personally, I would rather have an amp that retained the resistor values I installed in it.

Some say metal film resistors are sterile sounding.
Well, I'm not sure about that one either.

I think since the word mojo has started being used in conjunction with guitar amplifier tone, that it is over used and a buzz word to say the least.

If you want a resistor that will impart a buzzy noise and drift in value, absorb moisture from the air and cause other weird things to happen, by all means, include them in your builds.

Of course this is all IMHO
YMMV

[ckpop]

The most important thing to look at with using certains parts is the big picture and the final result.

While there is alot of debate of which resistors sound the best or signal caps sound the best, everyone seems to be looking for the magic bullet and missing the point.

There is no MAGIC BULLET PART, just great recipes of combination of parts and the choices of the builder putting everything together.

Example the parts Ken Fisher used he used for a reason, along with his knowledge and fine tuned ears. He did not follow a trend or a buzz but was interested in something made an improvment. Thats what it was all about.

[Structo]

Interesting, I've heard that many times Ken used what he had on hand rather than making a conscious decision to use a certain part.

I can't point to any examples but it's just something I read.

The skeptical side of me chuckled about when he said the red PVC wire sounded better than the other.

[ckpop]

Think with ken it was a matter of what he had on hand and was available at the time. I think also he was looking for specific specs also. He found his formula and it didn't change very much after that.

Yes I am skeptical somethings mentioned but I never rule anything out or make any quick judgement. Just because you install a new part and it does not sound better, is it the part or whats around the part that are not working to compliment each other.

The best advise I ever got from another well know famous amp guy back in the 80's was. Learn from everyone but never believe everything from just one.

[Richie]

Yeah, it's strange that some of the Metro amp fellas install a carbon comp kit in their builds.
But like you said, I don't believe Marshall ever used them.
They had carbon film which is much more stable.

The early marshall amps had CC resistors, or a mix of them in the amps.
No matter what resistors you use, unless you use some exotic pots,they are a variable resistor with a carbon track.. Some may ask if pots sound different..

I don't think enough tests were tried with cc resistors. And the one thing that is posted, always seems to pop up as being the bible of CC resistors. I do think they do produce a smoothness or have an effect on the sound.

Do they drift in value, yeah,sometimes. Do they make noise or go bad, yeah sometimes. But other times i have seen them in amps from the late 40s that are as quiet as any,and measuered they haven't drifted in value.

Alot of times amps or resistors stored in basements or left in trunks of cars,or even the location,if there is a lot of humidity. These are the amps that you may see have more problems.
And these amps may also have the same issues with tube contacts needing cleaned etc..
I've worked on a lot of old amps, and any others that have worked on old amps, may find the coupling caps going bad or needing changed,more than the resistors.

Many to almost all of the old amps used CC resistors,because thats what was available at the time. And if one clones an early amp,they want to use the same type parts. Not everyone,but some.

yes i have changed bad CC plate resistors in amps,also cathode,or grid stoppers to what ever section. And i've also done the same in amps using other types of resistors.

I think no matter what you hear or see posted,use what you like. Some values of the CC resistors are now getting harder to find,and also the price of them is really going up. And the CF or MF etc.. are not as expensive.
I just always hated to see people give the CC a bad name,and just passing on what they have read or someone told them on the net.

Some may say their isn't any mojo in parts, but knowing what or where to use certian type of parts can and will have mojo effect on the outcome of the sound. Usually a new builder may get 'lucky' and this happen. But its usually knowing what to use,and where to use, by years of experience listening and experimenting.

A scope may not always show or tell you how something sounds to the ear. If its a pleasing sound, or non musical as i call it to the ear..

[briane]

yes.

I am with bob-I, you can definetly hear the difference. yes, an amp is a sum of its parts, but only by using the best in each place can you get the super magic mojo.

Just try and swap out the 2 parts on an amp. Its pretty obvious.

[Richie]

but only by using the best in each place can you get the super magic mojo.

some may think the "best" is the most expensive .. but this may not always be true in guiar amps. Some of the holy grail amps people discuss used very inexpensive parts.

[Chappy]

but only by using the best in each place can you get the super magic mojo.

some may think the "best" is the most expensive .. but this may not always be true in guiar amps. Some of the holy grail amps people discuss used very inexpensive parts.

Like using el cheapo ceramic disc capacitors in certain places to help add dirt to the signal, as in some classic Marshall amps.

Richie - I just stumbled across your website. It looks real nice. Best of luck to you and your brother with your business.

Chappy

[briane]

some may think the "best" is the most expensive

best has nothing to do with price.

It has to do with purpose and place. Those rn65's while essential for plate, are mediocore (or not needed) for cathode.

BTW, a dumble is not a marshall, and should not be designed like one.

[Structo]

I just always hated to see people give the CC a bad name,and just passing on what they have read or someone told them on the net.

Some may say their isn't any mojo in parts, but knowing what or where to use certain type of parts can and will have mojo effect on the outcome of the sound. Usually a new builder may get 'lucky' and this happen. But its usually knowing what to use,and where to use, by years of experience listening and experimenting.

A scope may not always show or tell you how something sounds to the ear. If its a pleasing sound, or non musical as i call it to the ear..

Thanks for the post Richie.
I suppose I have to plead guilty to believing some of what I read.
I can't try everything that has already been done for the last 50 or more years, so I guess I should consider the source before giving it a lot of credence.

But you would have to admit there are quite a few very experienced amp builders that have an opinion about this or that from actual experience on the bench and with their ears.
So it would make sense if some of them are prejudiced against CC resistors because maybe that had a few bad experiences with them.
I would guess it would have something to do with what amps they have serviced over the years and which ones were prone to have problems with the resistors or caps we talk about.

The best amp tech would be one that is also a good guitarist, that way they know first hand what changing this or that does to the feel and tone of an amp.

I think sometimes things cross over from the Hi Fi crowd to the guitar amp crowd and since we all know that most guitar amps violate every rule there is for a clean hi fidelity amp we probably would do well to ignore some of that.

I would like to experiment with carbon comp resistors sometime but probably will never have the chance since the few amps I build are lucky enough to be completed or then sold to make room for others.

But to me, the CC resistors and other vintage components like Mustard caps and NOS tubes may be key in getting some of that old school tone, but one day which is going to be sooner rather than later, we will find ourselves without any of those parts available anymore.

I see some amp builders equip their amps with NOS tubes and they say in their specs that the amp was designed around those tubes or some other obscure component not readily available anywhere.
Well the day is near when those tubes won't be available and the same for the other parts.

So for me, my philosophy is simply to design or tweak an amp with modern components that are readily available and still make it sound good.

I was wondering what amps that Jim Marshall built that had the CC resistors?
Probably the first few JTM 45's or the 36 w amps?
I don't know because I haven't learned that much about Marshall amps yet, but I'm learning more everyday from guys like at this forum.

I really want to build a JTM 45 or Plexi 50 sometime soon because probably 9 out of 10 of my favorite rock songs used those amps to record them with.

[Colossal]

Those rn65's while essential for plate, are mediocore (or not needed) for cathode.

Briane,

Do you actually think them mediocre for cathode use or just unnecessary? I would think the precision and accuracy from a quality metal film would be desirable if cost is not an issue.