Improve stereo imaging on an NAD 3020?

Discussion in 'Solid State' started by filmis, Sep 12, 2017.

  1. filmis

    filmis Member

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    That'll be one of the later units, possibly an NAD 3020B. The earliest (not necessarily the best) units had 4 caps.
     
  2. ilusndweller

    ilusndweller Super Member

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    On a semi-related note, my 7045 receiver sounds noticeably better than my 7020. I dont know the history of either, but the 7045 is in a noticeably bigger enclosure. The 7020 still is an great sounding receiver(no its not a "insert gear costing >5-10x as much" here). For the price you can get the 7020 or 3020 for, the small size/footprint, and the flexibility (pre out/main in), they are keepers in my book.
     
    Last edited: Sep 13, 2017
  3. Karl vd Berg

    Karl vd Berg Super Member

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    True. Same thing applies to a few Harman Kardon series: good circuit, excellent transistors (2SC1775, etc), but cheap caps, often out of specs...
     
  4. Gazdatronik

    Gazdatronik Super Member

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    I think its important to realize that headphones don't image properly as a rule, unless the recording is done specifically to do so on headphones.

    My guess is that something in the Sherwood allows for a bit of left to right crosstalk, either by design or fault.
     
  5. Gibsonian

    Gibsonian AK Subscriber Subscriber

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    Have you recapped the Sherwood?
     
  6. filmis

    filmis Member

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    I have not, but I do believe it has been professionally serviced and re-capped. Can't say for sure though as I didn't take a good look at the caps while I was in there - I wanted to replace the burnt-out 'stereo' indicator bulb (to no avail, seems like something's wrong with the circuit... but no other issues whatsoever).
     
  7. Gibsonian

    Gibsonian AK Subscriber Subscriber

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    I'd be sure. Seems your looking for a cross between the 2. What if it hasnt been recapped? You might be able to have your cake and eat it too!
     
  8. filmis

    filmis Member

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    It's possible, but at least spec-wise it is a noisier unit, which has more to do with the transistors doesn't it? The NAD was also fairly easy to recap, as I could access both the top and bottom of the PCB at the same time, whereas I'd have to disconnect and screw out the individual boards in the Sherwood...
     
  9. Gibsonian

    Gibsonian AK Subscriber Subscriber

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    Specs are representative of the entire package, design and implementation, plus measurement technique and the honesty of the publisher. Yep, receivers are harder to get to, get apart and recap, but unless you want to buy something else this is an obvious option for you. And if it is a real keeper as it sounds like, you might consider replacing the transistors inside as well. Usually if something has been recapped you would know it as the person you bought it from/obtained it from would have mentioned this, it's really not a common thing to do for most techs. Usually they fix whatever ails it, and get it off the bench.

    I'm guessing it's not (simple probability). But anyhow, there could be quite an improvement in there, similar possibly to what you observed by recapping the NAD.
     
  10. filmis

    filmis Member

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    Sure, but then you'd expect the imaging to be equally 'bad' on both amps. The fact that they sound different suggests there's something more than just the headphones going on. And anyways, I confirmed that this was the case by doing a blind test on all 3 amps (and switching between them) on the same set of speakers.
     
  11. woodj

    woodj Super Member

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    Absolutely correct.
     
  12. Gazdatronik

    Gazdatronik Super Member

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    Not necessarily both would have bad imaging(or good). Most older amps tapped directly off the speaker output with some big resistors. Stands to reason then both speakers and headphone would have the same effect.

    What you should try out is some measuring. Recording both amps into a computer, playing left channel only, then right. See if there is something there that shouldnt be in the opposite channel.

    Maybe the 3020 is playing back badly, mixing the channels together.

    Another trick, which is easier is to play a wave or white noise file with the wave phase inverted in one channel. If you hit the mono button(if the amps have one) you should get no sound at all. If you hear something, that amp has an issue.
     
  13. filmis

    filmis Member

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    I agree that's a good suggestion, I'll take a look. I do remember when I opened up the unit that I was astonished at how clean it was, not a speck of dust on any component or part of the circuit board. For a near-50-year-old unit kept even in the best of conditions, I would suspect the only way to maintain that kind of cleanliness (next to godliness, some say) would be to have recently desoldered all the components, clean the boards, and (if you've already gone through all that trouble), replace the relevant parts.

    And can I take a moment just to pay homage to that gorgeous walnut case. This thing is build like a tank, and it's both functional and beautiful. Best $30 I ever spent.
     
  14. filmis

    filmis Member

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    I just tried the second thing. Both amps are dead quiet when the phase is inverted on one of the channels (mono mode or not). So I guess that helps rule out a problem with either of them.
     
  15. Gazdatronik

    Gazdatronik Super Member

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    Mono or not? That makes no sense. You should be able to hear the sound with the mono button disengaged.
     
  16. filmis

    filmis Member

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    Oh, I just realized I forgot to pan the noise tracks in Audacity... let me try it again.

    EDIT: Doing this properly, now, I can confirm the Sherwood is dead quiet when one of the noise tracks are inverted, panned to opposite channels and the mono button is engaged. Noise heard if set to stereo mode. NAD has no mono button so I can't do that for it...
     
    Last edited: Sep 15, 2017

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