What are the signs that an amp needs a refresh?

Discussion in 'Power Amps' started by Pancakes, Jul 14, 2021.

  1. Pancakes

    Pancakes Friend

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    I have a close to 20 year old NAD amp that I'm finding incredibly dark. Curious if my tastes have changed over time or the amp needs new caps, re-biasing, etc. Is there a common change in the sound of amps that need to be refreshed or do the changes vary depending design, parts quality, etc. TIA.
     
  2. AllanMarcus

    AllanMarcus Friend

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    The older you get, your ability to hear higher frequencies diminishes. Also, if you been listening to music too loud, your hearing will suffer too, and it will never come back. These situations could easily manifest in something sounding darker. The first thing to do is test your hearing.
     
  3. Biodegraded

    Biodegraded Friend

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    Have you tried cleaning the inputs, interconnects and speaker terminals with Deoxit or similar?
     
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  4. Metro

    Metro Friend

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    Dark compared to what? Do you also listen on headphones?
     
  5. Pancakes

    Pancakes Friend

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    Definitely not the hearing. I plugged my headphones into it (the speaker taps) and it's very dark compared to my headphone amps.
     
  6. Pancakes

    Pancakes Friend

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    I haven't. It didn't even cross my mind. Will give it a shot, thanks.
     
  7. Pancakes

    Pancakes Friend

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    Dark compared to my headphone amps. I've plugged several different cans directly into.
     
  8. Armaegis

    Armaegis Friend

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    I'd be curious to see if even a basic FR sweep shows it falling off at the top end.
     
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  9. Pancakes

    Pancakes Friend

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    I have a clio and mic but that would mainly measure the room and speakers so it's useless.

    Come to think of it, I have an old O scope. I wonder if I could use that in some way?
     
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  10. Armaegis

    Armaegis Friend

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    At the most basic, you can run some sine waves at various frequencies and see if they maintain the same amplitude and shape all the way up.
     
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  11. beemerphile

    beemerphile Friend

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    When an old power amp needs a refresh it makes a sound like a .22 rimfire going off and acrid smoke starts rolling out of the vents. Otherwise it's your ears. TMB. Too many birthdays.
     
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  12. bixby

    bixby Friend

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    I ventured into older "vintage" stereo stuff before and dark is a common trait. Pioneer SX-1980 sounded like doodoo, Yammy tol pre, ditto, HK-730, similar and on. I am sure though once refurbished they can sound great.

    There is a reason my Pioneer SX-1980 fetched over $700 plus freight to Vietnam for what I am surmising is a complete rebuild. When they are done they fetch between $1500 to $2000 rebuilt.

    Today, I just stay far away from vintage, since I have no innate schematic knowledge, test equip, motivation or dollars to "fix" aged audio gear. But that is just me.
     
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    Last edited: Oct 15, 2021
  13. Pancakes

    Pancakes Friend

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    Thanks, this sounds like exactly what I have going on.
     
  14. bilboda

    bilboda Florida boomer

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    You can likely set the bias and check dc offset yourself. Open her up and check for bulging leaking caps, etc. There may be an obvious and easy fix. Search or post on audiokarma and diyaudio for threads on your amp
     
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  15. TommyD

    TommyD Rando

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    LMAO! True!
     
  16. Pancakes

    Pancakes Friend

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    It was doing a lot of things that aren't right actually. After my initial post it started running out of steam when turning the volume up (past a certain relatively quiet point it just didn't get louder), the xformer started buzzing a lot. I've fully recapped it and will try to get it fired up and biased this w/e. May have to replace the rectifiers as well if the xformer buzzing doesn't go away. Surprisingly, my non-golden ears picked up the changes in tone before more obvious signs appeared. There were a several caps that were shot especially on the output boards - I assume this is where the change in tone came from. They weren't leaking or bloated or anything obvious but measurements show a clear loss of capacity - 80% in one case!
     
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