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Old 19th November 2010, 02:18 PM   #1
drjb is offline drjb  Canada
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Default Resistor Comparisons

Hi, I'm looking to upgrade the resistors in my tube preamp and based on the values, have it down to carbon comp Kamaya's or carbon film Riken's. Can anyone tell me how their sound signatures compare, or, in general, how carbon comp compare to carbon film?

The original resistors are Zicon carbon comp.

After many years of SS, I enjoy the lush, velvety sound that tubes are able to provide and I know these resistors can influence, greatly, that sound quality.

Any and all information appreciated.

thanks,

John
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Old 19th November 2010, 06:01 PM   #2
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Default resistors & tubes

I kept the allen bradley carbon comp resistors in my PAS2 tube preamp for forty years, but when I had to lift all the parts to look for a channel imbalance recently, I replaced the higher value resistors like plate resistors and feedback resistors with generic 5% metal film resistors made in India. Knocked the hiss right down below what the pilot flame on the gas heater makes. What everybody says on here is true! Metal film is better! Be sure ordering modern resistors for tubes to check the voltage rating. Everything is so miniaturized now that 1/4 W resistors are no longer rated for 450 V, they are too short! I'm buying 1w & 2w metal film resistors. Newark.com us and farnell.co.uk have the resistor voltage rating as part of their selector chart, use it.
If you are not an experienced tech with lockout training, read tube forum sticky thread tube basics for newbies. Capacitors store energy, tube plate capacitors can kill you if not discharged safely before touching the connected parts. A speedy tip, wash all the flux off your boards thoroughly after work, and if any crackling occurs, spot it with the lights off as arcing is pretty easy to set off with flux. Probably some of the crackly tubes I replaced over the years were actually 1961 era flux not removed from the PCB by the minister that built the kit.
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Last edited by indianajo; 19th November 2010 at 06:07 PM.
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Old 19th November 2010, 08:45 PM   #3
drjb is offline drjb  Canada
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Indianajo, I've already replaced the higher value resistors with metal film resistors and I concur, they're dead quiet, by comparison to the carbon comp. However, in making the change, I've also lost the velvety, liquid flow provided by the carbon comp resistors and miss this quality, dearly. Maybe the carbon film resistors, like the Riken, are a compromise, a reduction in noise, with more liquidity, I don't know; but, this is why I'm writing to ask if anyone knows how the carbon comp compare with the carbon film, for sound quality?

As for the safety warnings, while I've been around electronics people most of my life, I do consider myself a newbie, as I relied on these friends for this kind of work. Now that they're no longer around, I have only myself to rely on and so, therefore, will heed your warnings and will read the forum for tube basics for newbies. I do realize that caps store energy, however and my pre is all point to point wiring, no circuit board. Warnings much appreciated, though; thank you!

John
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Old 19th November 2010, 10:13 PM   #4
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Plenty of info here: Resistor Sound Quality?
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Old 19th November 2010, 11:25 PM   #5
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Thanks, Rodeodave,

but I read through it and didn't find anything specific. Most posts are positive about Riken, but not all and the same goes for carbon comp, in general (I guess there are more negatives). Hard to draw any conclusions from this, beyond the need for trial and error.

All I really want to know is: would I be giving up any liquidity, any of that velvety flow if I chose Riken over Kamaya or carbon comp, in general?

thanks,

John
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Old 20th November 2010, 01:47 AM   #6
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Don't recognize your adjective velvety, I guess. I changed speakers about the same time as I changed resistors, including getting the speakers up off the carpeted floor onto stands where they can reflect off the plaster walls, so I'm not hearing nearly as much fabric now, and I think that is a good thing. The PAS2 preamp got really bright at the same time as the resistor change, probably excessively so, as I'm running with trebel tone controls down. I blame that on changing the capacitors at the same time, in particular I put in .22 microfarad (uf) 10% polyprophylene caps in place of .20 uf 20% paper caps, so I'm blaming the excessive trebel on that right now. The last paper .20 uf cap I replaced was the one causing the imbalance, the builder had turned the burned spot in the wax case down so I couldn't spot it until I removed it. Then I spent a week or so of evenings chasing popping noises due to flux on the PCB, so I wasn't in a hurry to put the paper caps back. Try the experiment and see what you like, the resistors themselves are very cheap. My current thrust is to get an op amp disco mixer to sound as good as the PAS2, at 1/100 of the power and with parts that are actually available. (I can't buy a correct 250k stereo log volume pot with loudness feature, and two 12AX7 tubes are 49 years old and probably leak a bit too much). Right now the disco mixer's trebel is more what I am used to (it has no tone controls) but the hum is excessive.
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Last edited by indianajo; 20th November 2010 at 01:55 AM.
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Old 20th November 2010, 02:12 AM   #7
drjb is offline drjb  Canada
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Indianajo,

here ye go:

Velvety - Definition and More from the Free Merriam-Webster Dictionary

At least you have treble controls; my pre has no tone adjustments.

When I change the resistors, I'm also planning on changing the caps. It does really seem to be a crap shoot.

I'm just now getting a taste for all this and am really enjoying it. You've taken it a step further, already.

There is an ALPS volume pot available for my pre, but it's definitely not cheap. Not sure how far I want to take it, at this point.

Will do, will toss a coin, buy & try one or the other.

Again, thanks for your response and good luck with your projects.

John
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