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Anyone compared high end Class D power amps?

Discussion in 'audio' started by Thetiminator, Jan 7, 2020.

  1. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    With 105dB/W efficiency it is a very tall order for any amp to be completely silent even if you are only say a foot away from the speaker and in a completely silent room...
    It has nothing to do with the class of the amp. Most (to all intents and purposes all in fact) hiss comes from the amps input stage/s.

    S/N ratio's have to be compared carefully.. you need to be "comparing apples with apples"! Is it stated as relative to the amps full power or relative to a specified power output?
    With a 200W amp 100dB S/N relative to full power is a lot noisier than a 10W amp being 100dB S/N relative to full power! Are figures in fact relative to power or to voltage? Over what measurement bandwidth?
  2. steveinspain

    steveinspain pfm Member

    Thanks Alex - much appreciated. I will keep my eyes open a used one or may just splash out - I'm just curious about what a different amp might add..
    Out of curiosity, was your power-amp-only a reasonable amount cheaper than the integrated amp?
  3. Thetiminator

    Thetiminator Painfully virile

    Ok I get you. All I went from was manufacturers specs after hearing the amps. The quietest ones had higher S/N ratios as a general rule.
    With even the best valve amps (most expensive) I could hear hiss from the listening seat c.5-6m away. With the Temple Audios I have now you can only hear a little hiss from the mid unit if you’re ear is a few inches away max....
  4. Alex S

    Alex S carbon based lifeform

    Steve, it cost about the same because I asked them to please make me the best power amp they possibly could.
    steveinspain likes this.
  5. Dan K

    Dan K pfm Member

    Sounds to me like you might want a 1st Watt SIT-3.
    Torris12 likes this.
  6. Thetiminator

    Thetiminator Painfully virile

    I’d need the monoblock Sit-1’s...a bit more than I’m happy to spend....
  7. Thetiminator

    Thetiminator Painfully virile

  8. sq225917

    sq225917 Bit of this, bit of that

    MMM, class d doesn't stand for digital it was just the next available letter when the class was introduced. A true digital amp takes a digital input directly.
  9. ToTo Man

    ToTo Man the band not the dog

    @Thetiminator, maybe I've missed it but what preamp are you using, or is your DAC serving as preamp?
  10. Thetiminator

    Thetiminator Painfully virile

    It’s a Boulder pre and dac....balanced outputs only..
  11. Shadders

    Shadders pfm Member

    From the link, the amplifiers are class D.
  12. Grenadier_45

    Grenadier_45 pfm Member

    At the risk of going off-topic, because it's not class D, have you considered the Benchmark AHB2? Not to want to contradict our resident forum amp designer, but the other part of the S/N ratio problem is unnecessary gain. The Benchmark deliberately has a relatively low gain, because modern systems don't need it, and has 130dB S/N as a consequence.
  13. Julf

    Julf Facts are our friends

    And has a digital feedback loop. Very tricky.
  14. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    A few points arising from recent posts...

    There are no real advantages to monoblocks... It's an old wives tale.

    Many of the Pass designs are likely to be unsuitable due to noise. Many of them use mosfets at the input stage which are noisy... Quite possibly not all but most of the ones I'm familiar with.

    Most power amps have a gain of around 30dB. The majority of over sensitive ones are no longer made. Within the small range of differences in gain for a practical unit for home use the noise contribution of the input devices will be the most significant factor. The Benchmark apparently has sensitivities of 2, 4 and 8V for max output!
    Julf likes this.
  15. Julf

    Julf Facts are our friends

    The Hypex nC400 has a gain of 26 dB by default.
  16. Grenadier_45

    Grenadier_45 pfm Member

    Indeed so - hence why the Benchmark's lowest gain setting of 9dB (or so) is quite atypical. Even the 2V sensitivity setting only has 23dB of gain. Stereophile had trouble measuring it - its performance in terms of noise and distortion was on the limit of their Audio Precision test gear:

    It might still not be the OP's cup of tea, but the measurements are impressive, and I doubt he would be troubled by hiss, even with 105dB/W speakers.
  17. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Oh it has impressive measurements and seems a very good amp! It just pushes the noise issue to the pre amp though!
  18. gingermrkettle

    gingermrkettle Deep vein trombonist

    Of the Neurochrome amps referenced previously, the standard through hole Mod86 can be built with 14dB gain and a specified noise/ hum level of 40uV unweighted, 32uV A weighted. The more expensive Mod186 or 286 reduces that to 28.5uV/23uV but with a minimum gain of 20dB.

    My back of a packet calc makes the resulting noise level from the Mod86 c. 25dB at 1m with that sensitivity spec, which should be good enough.
  19. Grenadier_45

    Grenadier_45 pfm Member

    Yebbut! Aren't you always advocating passive preamps, 'cos modern sources have such high outputs? In which case only the noise contributed by Mr Johnson ought to be an issue.
  20. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Not with such an insensitive power amp! That's the point... it needs more gain which must then come from an active pre amp...
    The 2V setting may be usable with a passive but on quietly recorded material it may be necessary to use full volume.

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