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NAP250 passive preamp or Ryan Sound 32.5 preamp conundrum

Discussion in 'd.i.y.' started by diybry, Nov 24, 2020.

  1. diybry

    diybry pfm Member

    My system: CB250, 32.5 (Avondale 821) Hicap (Avondale TPR4) KEF R5s
    Analogue source LP12/Ittock/Troika (Little used these days)
    Digital source NAD D1050, JRiver and Tidal

    I've trialed the Ryan sound boards in my 32.5, and am very impressed with the result. removal of a veil from the music, more depth and detail. Excellent foot tapping stuff. Definitely an improvement over both the Naim and Avondale 821 boards (I've not heard the 821A, which are probably the equivalent, to be fair to Avondale)

    However I've also tried eliminating the 32.5, inputting the DAC output directly into the 250, using Jriver volume control, and here's the issue:
    Sound quality seemed poorer than even the standard Naim board equipped 32.5. it's hard to describe the actual difference, there seemed to be a lack of 'drive' and soundstage. Kind of 'flat'
    The NAD tech blurb says the D1050 output impedance is 'vey low' (although I cannot find an actual figure) whilst the 250 input impedance is 18k. My freshly googled knowledge tells me this should be fine.

    I'd really like to achieve a passive input to the 250, as again, I've read that a reduction in complexity should result in an improvement in quality.

    So what could be the reason for this result?

    I've thought of several, and would appreciate guidance on which one may be correct, and also, what could I do to optimise a passive input to the 250, such as building a DIY passive preamp that wont cost the earth....
    1) The 32.5 actually adds some colouration the music which whilst it may not be accurate, is pleasing to the ear?
    2) I know the 32.5 has some filter (high frequency?) which the 250 requires to operate correctly, but I've also read that it's no longer necessary with modern electronics?
    3) The 250 requires an input buffer. I don't know why this should be, as my very limited understanding is that a buffer 'matches' impedances, which from what I've red, are already compatible?
    4) The JRiver digital volume control is degrading the signal? (Although this seems highly unlikely to me)

    Any solutins, ideas or theories are welcome. I guess I'm I'm rather hoping all this will lead to a simple passive DIY preamp which will outperform the 32.5 by virtue of its lack of electronic complexity, but if not, I'll probably go for Kit's sound boards in the 32.5
     
  2. Gervais Cote

    Gervais Cote Predator

    I never had good success matching different preamp with Naim amps personally. Always sounded wrong.
    I would upgrade the Naim preamp (32.5 or 72) rather than getting uncertain results from multiple trials and errors.
    Avondale items are the best IMO as they keep the Naim signature and improve all the rest.
     
  3. MJS

    MJS Technical Tinkerer

    The Naim pre-amp gain circuit (321 board) was called the 'miracle circuit' at the factory. It is largely responsible for the Naim sound. The 821 and variants don't sound like that at all in my view but all the comments about them being more transparent are entirely valid and justified. The pre-amp is adding a sonic signature that's removed when you go directly into the amp.
     
  4. mega lord

    mega lord Centre tapped

    I used to use 821A in a Nac72 and Avondale amps in Naim cases. I remember removing the Nac72 and using just a pot instead. I could not believe the increase in transparency at the time. If it lost any "drive" then I did not notice it. There will be others however who will have thought the opposite no doubt.

    I often hear people describe how active stages are transparent. IME they are nowhere near transparent, even the 821A with it's minimal component count and low (zero ? can't remember) feedback. I had a similar experience when I bypassed the anologue output stage of my CD3.5 and just used the first order filter on the end of the Dac chip. Veils lifted ? Hell yeah. It highlighted that the complex output stage was responsible for a reduction in detail and added a sheen that for some was the cause of much annoyance.
     
  5. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    A 10K or 20K passive should work fine. switched attenuators are best.
     
  6. diybry

    diybry pfm Member

    Thanks for your advice
    Excuse my lack of knowledge here:
    In addition to providing volume control, is 10k or 20k attenuator likely to improve sound quality vs the direct connection I have experimented with?
    If so, would you recommend this?
    https://www.ebay.co.uk/i/333675480899?chn=ps&mkevt=1&mkcid=28
    To double check : The fixed resistance goes across the DAC output, and the wiper goes to the amp?
    thanks again
     
  7. Arkless Electronics

    Arkless Electronics Trade: Amp design and repairs.

    Impossible to say as to sound quality.
    I would steer clear of that. I would expect a top quality one to have another zero on the price. I couldn't buy just the switch, trade, for that price. There should be no difference in sound quality between this one and a £500 one but reliability is likely to be another matter! It could be OK to see if you like passive I guess.

    Yes that's how it's wired. Ground needed as well of course.
     
  8. diybry

    diybry pfm Member

    Thanks again. Your assistance is most appreciated. I'll give the cheapo switch a go to see if it's worth going in the passive direction
     
    Arkless Electronics likes this.
  9. oldjazzer

    oldjazzer New Member

    I've been running a much modded 32 (6 channel psu) into a CB 250 for around 30 years.
    A house move gave me a larger room and a while later, the urge to improve the system.
    Keeping it relevant to the OP and not going into all my other upgrade activities, I went for a full set of Ryan Labs boards for he 32 - an improvement, but not night and day probably held back by the rest on my somewhat long in the tooth kit.
    Skipping a good few months and taking advantage of the 1st lock down for extended home demo of some expensive ( to me) amps,streamers and speakers, i settled on a pair of active ATC SCM40A.
    Driven by the 32 sounded better to me than direct from the RME DAC (which like my previous audiolab has a volume control).
    Moving onto the 2nd lock down, i thought to myself, i'm running a really ancient preamp, surely that must be a weak link and I took the opportunity (and good support of my trusting dealer the Audiobarn ! ) of a month long home demo of the £1700 ATC preamp.
    Well I was surprised to find the 32 sounded better!
    It was a close comparison, but digital sounding warmer (more analogue) and analogue TT having more depth and separation.
    So lots of the latest 21st century kit all controlled and driven by last century's preamp!
    It held its head up high against prolonged listening against the preamp side of Deviolet, ATC, Primaluna, Naim 202.
    The 32 with Ryan Labs cards is for me, keepers!
    Hope that gives you an idea of just how capable the 32 can prove to be - hope you get to the right sounding solution.
     
  10. Gervais Cote

    Gervais Cote Predator

    Thanks for this very informative report, very interesting.
    I am the proud owner of a NAP 32.5 with Neil Jadman’s cards and this is a real keeper for me, its musicality is hard to beat. Paired with my CB Hicap with Avondale TPR4 and my BD160, this is a real pleasure to listen to.
     
  11. oldjazzer

    oldjazzer New Member

    aah, a fellow guitarist judging by your avatar.
    I used to have 32.5 into a 110 until I moved to the modded 32.
    The 32 / 110 is still running sweetly at my brother in law's place
     
    Gervais Cote likes this.

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