[R-390] Resistors

[Roy Morgan]

At 10:39 AM 1/3/2006, Barry Hauser wrote:
>Hi Roy
>
>Thanks for the explanation.  Of course, now I'll be listening for oboes 
>and clarinets ;-).


Tweet!  SkRONK!  Blaaat...
(that's what I sounded like on a clarinet way back then.)

>I think part of the reason for favoring carbon comps is avoidance of 
>inductance or capacitance introduced by metal or carbon film resistors 
>--  whether real or imagined.

I don't remember the details from the tests one fellow did on metal film 
resistors, but my conclusion from the data was: Just Don't Worry About 
It.  The fact is, very very few resistors in the R-390 are actually used 
with RF or IF on them. The rest are bypassed thoroughly.  Does the 
R-390A/URR use IF coil snubber resitors?  I think the R-390/URR does, and 
it was a mistake to snip them out to get narrower passband and higher gain.)


>Some audiophile restorers seem to be looking to preserve whatever 
>component characteristics inherent in the old tube designs -- good, bad or 
>indifferent --

Yes, that makes sense. I have not yet had the chance to compare sounds of 
capacitors, or resistors.  Maybe one day.

>... I suppose if your objective is to retain authentic performance, 
>including distortion and noise, it would make sense to stay with 
>components of identical or similar construction -- providing functional 
>components of the type can be found today.

I have a few period resistors around. I often find they have drifted up in 
value, even if unused.

>As I recall, there was a thread some years ago about whether or not a 
>modern carbon film resistor might cause a problem somewhere in the R-390A 
>if used as a replacement for a carbon comp.

I don't remember that, but then there are a lot of things I don't remember. 
heheh   I think what I'll do is use modern parts and see if they cause any 
trouble. I expect they won't.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
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