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Should I expect much of a break-in with a new hi-quality resistor?

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hukkfinn

A

I have a tubed phono preamp with a volume control. I had the volume pot professionally bypassed with a vishay resistor that "sets" the amp at about half of its maximum gain. (I chose this resistance because the volume pot was linear and I usually set it at 12 or 1 o'clock.)

In my first 5 hours of use, the amp sounds strange - pinched, too bright. Not good. But it should have IMPROVED, since I got the volume pot out of there. (Right?)

Is there maybe an extended break-in associated with hi-quality resistors?

Hukk

Follow Ups:

I would have tried PRP or Caddock. - Al Sekela 15:23:12 01/29/10 (6)
You may not like the performance of the Vishay resistor.

You can't replace a pot with a single resistor. If that is what your pro did, then you need to find one who understands the circuit.
- Hmm THAT'S interesting... can you elaborate please? - hukkfinn 16:10:40 01/29/10 (5)
  Thanks for any additional input.
  
  Hukk
  - A potentiometer has three terminals. A resistor has two. - Al Sekela 14:32:48 01/30/10 (4)
    The way a potentiometer is usually employed as a volume control is with the full range of the potentiometer (end points) connected as a load to the driving section, and the tap connected to the input of the driven section. The driving section design depends on there being the full value of the potentiometer resistance always present, no matter where the tap is placed by the user.
    
    Now, it is possible that the original design only used two terminals of the pot, with a fixed resistor from the input of the driven section to ground. In this case, the mod was correct and maintained the original circuit topology. If so, your sonic observation has to do with the characteristics of the Vishay resistor and is not a fault of the modifier.
    
    However, if the original design followed convention and the modifier changed the topology, then the sonic problems could be a result of the changes.
    
    Tubes have essentially infinite input resistance, and grid-to-cathode resistors are usually of very high value. Their operating behavior depends on the load resistance. Making a significant change in the load resistance of the driving stage could cause problems.
    
    I suggest contacting the manufacturer or designer if you don't get a satisfactory answer from the person who performed the modifications.
    - Thanks very much. Question.... - hukkfinn 18:27:32 01/31/10 (3)
      I always hear in these forums that Vishay resistors are supposed to be great.
      What sonic qualities lead you to suggest those other 2 brands over vishay?
      
      I'm curious if vishay is all hype and no musicality, sort of like the Bose of resistors...
      Hukk
      - All resistors have some sonic character of their own, - Al Sekela 15:16:38 02/01/10 (2)
        
        In Reply to: RE: Thanks very much. Question.... posted by hukkfinn on January 31, 2010 at 18:27:32
        
        depending on how they are used. Vishay is a major manufacturer of electronic parts (see their home page at http://www.vishay.com/) and resistors are only one of many products they make.
        
        Large companies like this concentrate on quality from the manufacturing perspective: that the parts meet specs and perform reliably, not necessarily that they sound good in a particular audiophile application.
        
        In fixed discrete resistors, Vishay has about 350 data sheets (see http://www.vishay.com/resistors-discrete/). There are some resistors with very low temperature coefficient. This could be a factor in how much distortion is produced by self-modulation of the signal, but it depends on how much current the circuit applies to the resistor. My guess is that other things, like the resistor film, insulation, and lead materials, will dominate the sonic character.
        
        You will find some audio manufacturers who like Caddock resistors for stepped volume controls, even though they are more expensive than Vishay. My own experience is not with volume controls, but with damping RF noise. PRP, but only the half-watt size, are the best I've found.
        
        One more thought is to check on how the modifier mounted the resistor. If it is standing by itself and supported only by its leads, it could be vibrating and causing acoustic problems from the vibration.
        
        Thanks, that's really helpful. Sorry to be such a newbie. - hukkfinn 18:58:21 02/01/10 (1)
        
        In Reply to: RE: All resistors have some sonic character of their own, posted by Al Sekela on February 01, 2010 at 15:16:38
        
        Hukk
        
        Everyone is a newbie sometime. - Al Sekela 15:26:27 02/02/10 (0)
        
        In Reply to: RE: Thanks, that's really helpful. Sorry to be such a newbie. posted by hukkfinn on February 01, 2010 at 18:58:21
        
        I've learned a lot from others on these forums.
        
        Did you ever resolve the question of why your mod person replaced a pot with a single resistor?
RE: Should I expect much of a break-in with a new hi-quality resistor? - bacobits 08:35:42 01/29/10 (1)
huk, is this your Art Audio Vinyl One? I wouldn't have messed with it.
My opinion of course and I have not lived with the piece.

D
- Nope, different unit. - hukkfinn 09:03:56 01/29/10 (0)
  Thanks,
  Hukk

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