KOA Speer Carbon resistors versus Kiwame

Hi,

I have found this quite old topic:
Kiwame resistors

comparing the KOA Speer SPR carbon resistors versus the well known KIWAME carbon.

I use very often the Metal KOA Speer resistors, but I mainly have 2 questions:

a-/.how would you define the sonic differences between carbon and metal resistors ?

b-/.what are the conditions were you preferred Carbon resistors over their Metal counterpart ?

Thank you very much,
P.S.: I see that this topic should be moved to the "parts" forum (sorry),..., maybe a moderator can to this... Tks
 
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There are no conditions to prefer carbon composition resistors, they are unstable over time and non-linear.

Carbon film are somewhat better. Metal film are extremely good.


Simple choice.

This is exactly what I have done until now (Metal film are my preferred resistors), but I am surprised that a few persons still prefer Carbon film over Metal film, the reason for which I ask if there are places where you prefer to use Carbon film resistors...
 

llwhtt

Member
2008-06-12 3:43 am
SoCal
I received some Ohmite CC resistors from Mouser not too long ago. They came in a sealed bag with a big caution note on it, "CAUTION This bag contains MOISTURE-SENSITIVE DEVICES" It also had the date the bag was sealed with a 1 year shelf life. Doesn't sound too promising does it?

Craig
 

schiirrn

Member
2018-11-18 9:13 pm
a-/.how would you define the sonic differences between carbon and metal resistors ?


To get back on topic after all the bashing: when you detect a sound difference between resistor types, check if the active components associated with that node are stable. There is a good chance the sonic differences are based on hf oscillation influenced by different parasitics of these resitors.
 
I received some Ohmite CC resistors from Mouser not too long ago. They came in a sealed bag with a big caution note on it, "CAUTION This bag contains MOISTURE-SENSITIVE DEVICES" It also had the date the bag was sealed with a 1 year shelf life. Doesn't sound too promising does it?
Craig
After 1961? the carbon comp resistors from Allen Bradley & Sprague that had mil-spec numbers had a significant improvement in moisture sensitivity. We who repair Hammond organs noticed a considerable improvement of life of the infamous megohm resistors in the AO-28 amp. These were very similar looking resistors to the mil-spec versions. Dynaco and Scott were also using resistors from these vendors according to David an organ/amp repairman in NC posting on organforum. I certainly had no trouble with resistance creep in carbon comp resistors in my 1961 dynakit equipment. I suspect the Navy drove research into moisture resistant paint, which made significant improvement in product life of the civilian parts made on the same production lines. As a datapoint, organs assembled in Holland at the same time were not nearly as reliable near the sea, as the US built models. These RCR07g resistors of course were abandoned by the military, at some point. I specified some RCR07g for a PWB going into Mission Control Center about 1978. AB & Sprague left the carbon comp resistor business. Who knows if Ohmite or any other carbon comp vendor has knowledge of the mil-spec moisture blocking paint. As I get bags from distributors with static warning labels on 20 amp bipolar transistors, I don't take these labels as absolute truth. However since I don't repair vintage AM radios or build clone guitar amps, I am buying metal film resistors. The ones over 100kohm are quite a bit quieter than carbon comp in my 1961 build dynakit equipment.
 
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AE7OO

Member
2019-07-07 1:59 am
I believe their main worry here is about possible moisture invasion, which can a concern for any packaging that is not hermetic. In almost all cases you can prebake the part over 100C for a couple hours to get rid of it.


I've got a toaster oven I use for my re-flow and either the second or third time of having a live board in it(for testing), a chip blew it's top. And I'm fairly sure it was moisture that was the cause, seeing how this part what had in one parts drawer or another for over 10 years(That was about the last time I had bought any CDXXXX parts)
 
Carbon comps' are pretty non-linear and tend to drift in value with age. Their one strength is pulse energy rating since the energy is dissipated throughout the bulk rather than in a thin surface layer. However this is not useful for low voltage audio circuits, more something relevant to high voltage high energy circuitry such as a snubber.

Metal film are very close to perfectly linear, wirewound are for all practical purposes linear. No carbon device can compete with this. Metal usually have much tighter tolerances and much lower tempco's too.
 
I feel kiwame has more of a analogue feeling to how they sound. I easy get somewhat pronounced ”s” and ”t” with metal film and i generally think they’re little too bright. Of all metalfilm ive tested i think KOA, vishay mb0207 pro and Dale rn and cmf are the best. Even Vishay CCF are ok.
But if the bunch i think the pro 0207 (0.6w) is the real steal. And yes Kiwame is Koa SPR. Have both and they sound and measure identical tegarsing tolerance