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-   -   Metal film resistors or carbon film in a tube amp? (http://www.diyaudio.com/forums/tubes-valves/8425-metal-film-resistors-carbon-film-tube-amp.html)

SHiFTY 8th December 2002 08:55 AM

Weren't resistors before ~1970 carbon composite, NOT carbon film? I thought carbon film was a more recent invention.

Carbon composite resistors are hopeless- they can't handle the heat of a soldering iron, and tend to fail catastrophically after a few years, often to a short!

I use 1W carbon film resistors, never had a problem. 1/4 W metal films are too small and fiddly, I prefer the chunkiness of a 1W resistor, as well as its power handling capacity.

Brett 8th December 2002 09:02 AM

Quote:

Originally posted by peranders
First of all: Consider the voltage rating for metal film! Ordinary metal film are 300 Volts!

Metal film are better in amlost every parameter except for transient power handling. Some types carbon resistors are better in this respect.

Which parameters are better:

Noise
Long term stability
Temp coeff
Resistance tolerance
Power handling (vs. volume)

My advise is to use metal film as much as you can.

Generally agree with what you posted peranders, but the modern carbons such as Kiwame and Riken are very good in these parameters too, and will have a higher voltage rating. Prices aren't too bad, esp for the Kiwames (2W ~ $US1 ea).

Mills NIWW and Vishay, Meggitt and Caddock are also very good but the last two esp can be pricey. Mills 12W are good value IMO for their performance.

Cheers

Brett 8th December 2002 09:06 AM

Quote:

Originally posted by peranders


G, I forgot maybe the reason for changing resistors. Technically, I think no tube amp really needs metal film. Why?

No low noise application (normally)
No demand for low tolerance (5% is enough)
No need for long term stability (tubes aren't very stable)
Heavy colouration from the tubes and transformers itselves.

Whilst this may apply to a 50's Dyna amp, it certainly does not apply to many cutting edge tube amps.

Fred Dieckmann 8th December 2002 09:12 AM

Technically, I think no tube amp really needs metal film
 
ABSOLUTELY CLUELESS! Anybody that thinks that this is advice deserves to follow it. I am embarassed to read such nonsense which flys in the face of common sense and reality. I think that the reply must have been posted as a joke since nobody could be so misinformed. It is post like this make me wish I could put people in the sin bin.

dhaen 8th December 2002 09:58 AM

Tollerance
 
Don't forget that most of the valves we use, were designed at a time when the resistors in service were +-20%. Not exactly cutting edge there:)
Consider also the spread of valve characteristics.
Taking those in mind, it becomes clear that the "tollerance race" is one of sharply diminishing returns.
Of course that doesn't mean there's no point. We all strive for excellence - even under unfavourable conditions.;)

halojoy 8th December 2002 10:28 AM

Carbon composite - Carbon Metalfilm
 
Quote:

Originally posted by ShiFtY
Weren't resistors before ~1970 carbon composite, NOT carbon film? I thought carbon film was a more recent invention.

Carbon composite resistors are hopeless- they can't handle the heat of a soldering iron, and tend to fail catastrophically after a few years, often to a short!

I use 1W carbon film resistors, never had a problem. 1/4 W metal films are too small and fiddly, I prefer the chunkiness of a 1W resistor, as well as its power handling capacity.

Shifty says it.
Carbon Composite and Carbon Metalfilms
are quite different in caracteristics.

Also true that pure metalfilms doesn't often come in sizes that allow much power.
Ceramic Metalfilms (is that what it is called) can take some few watts.
It is also possible to use series or parallell combinations
to increase power tolerance.

Tubes needs some watts in the resistors, not in all places, but in several.
Carbon Film would maybe be the best choice in those places.
Of course development has been done both in Tubes and in "old" components.

Time doesn't stand still in any area.
The change rate can be very different between the areas
for the present time.

jh6you 8th December 2002 10:46 AM

This is a copy from http://westlabs.com/Resistors.HTML

JH

.....................
Q: Why do you recommend metal film resistors, when other boutique manufacturers recommend carbon composition?
A: Because they are the absolute quietest resistors available, with the exception of wirewound, which are not available in the high values used in tube amplifiers. Carbon composition resistors are the noisiest of all the resistor types, and will create a lot of "hiss" and "crackling" noises. They tend to drift in value with temperature, humidity, and time. Some people claim carbon comps "sound" better. I believe the tone of the amplifier should be achieved through the circuit design, not through something as wildly variable as a carbon composition resistor. The use of metal film resistors allows a stable, repeatable, and most importantly, quiet amplifier, which will sound as good and quiet ten years from now as it does today, unlike an amp which uses carbon comps, which will get noisy and drift in value over time, changing the tone of the amplifier and adding unwanted noises. How many old blackface and silverface Fenders have you heard that make hissing and crackling noises? Most of them do, particularly if they have been kept in humid climates, and it is usually the carbon comp plate resistors that are at fault. Precision metal film resistors cost more than other types, but they are worth it, in my opinion. Be sure to use at least a 1W metal film, as the voltage rating on the 1/2W and lower units is usually only 250V - 350V. I use 2W 750V 1% or 1W 500V 1% metal films. The 2W units have the lowest noise, but take up more space. If you can't get a great tone out of an amplifier using metal films, you are doing something wrong. The only thing you have to lose is the noise.
.....................

Elso Kwak 8th December 2002 10:48 AM

Resistors
 
Hi,
Yeah Fred, I got tears in my eyes......
Please guys, read Horowitz Appendix D 1% precision resistors.
You tube addicts should also read pages with fig 6.53: <B><I>carbon composition resistors exhibit a reduction in resistance above 250 volts.</B></I> And in the text: <B><I>Carbon resitors run at higher voltages show astounding voltage coefficients, not to mention permanent changes of resistance.</B></I>
There also excisted a nice Reference Reading from Linear Technology:
Avoiding Passive-Component Pitfalls (Nice title in this context!) and the same paper was also on a Analog Devices CD-rom as Application Note 348. I couldn' t find either of these papers on the websites of these companies.:xeye: :xeye:

halojoy 8th December 2002 11:06 AM

peranders had some little point
 
Quote:

Originally posted by peranders
First of all: Consider the voltage rating for metal film! Ordinary metal film are 300 Volts!
Metal film are better in almost every parameter except for transient power handling. Some types carbon resistors are better in this respect.
---------------------------------
My advise is to use metal film as much as you can.

I think no one can deny this.
Not even :eek: the non swedish people :eek:
there is few of those around also

like Koreans Netherlanders and Paradisers
I have never been to Paradise, yet
--- but we will see - what will come ................

Music that plays extra good an a Tube amplifier (with or without C-atoms)
is:
:cool: "Pastime Paradise"
:cool: from the album "Songs In The Key Of Life"
:cool: Composed by Stevie Wonder 1976, only yesterday
I bought the vinyl but have also the CD
I have to be prepared for to get along both with the analogue and the digital friends
Anyone else who have a digital friend
their minds have no state in between

On the album are songs like:
- Love's In Need Of Love Today (send yours in right way)
- Have A Talk With God
- Sir Duke (we all know the swing of that one)
- Isn't She Lovely (with some autehentic sounds of a little girl)
she is probably over 30 now - but the document will
stay "Forever Young"

Brett 8th December 2002 11:17 AM

Oops.
 
I just noticed in my first post in this thread, that I didn't note that the Kiwame and Riken carbon resistors, are carbon <i>film</i> not composition.

I use Kiwames often when replacing faulty or out of spec parts in older (vintage) tube gear. They are much quieter than the original resistors in some Fisher and Scott gear. I've also tried them in some positions in my newer amps and like the sound (vs MF). Subtle but noticable. In line level and power amps I haven't heard any difference in noise. The tolerance on the Kiwames is 5%, but every single one I've bought has been better than 1%.


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