1.     Don't be a dotard!
    Read these "rules" AND introduce
    yourself     before your first post
  2. A healthy approach to understanding measurements
    Being true to what the artists intended
  3. After being asked for the 308th time, Merv lists top 5 headphones
    (opinion / entertainment piece)
    Dismiss Notice
  4. $1000 to the first to design a headamp using discrete components with better measurements than Magni 3+
    Dismiss Notice
IMPORTANT: New Members Read This Don't Be a Measurement Fascist Merv's Top 5 Headphones - 2023 Edition $1000 Challenge

Digital Volume Control & Alternatives

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by direstraitsfan98, Jun 20, 2018.

Page 4 of 4
  1. Armaegis

    Armaegis Friend

    Pyrate BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    7,537
    Trophy Points:
    113
    Location:
    Winnipeg
    Armaegis, Jul 31, 2018
    #61
  2. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    Well, we are discussing pre-amps off all kinds, so might as well.

    Most amplifiers indeed seem to have relatively high input impedance ranging between 5k all the way to maybe even 470k and in most cases the roll off itself may not be a big problem.

    What JA did not explicitly say is that even with a common 10K input impedance, the pre-amp may introduce a bit of phase distortion at the low frequencies, given the roll-off observations using a 600 ohm load. It's also worth to note that the X-30 plays better with amps with relatively high input impedance. Note this is a $16k pre-amp, not a $50 one.

    I also don't know why 120 ohm output impedance plays a role on the roll-off mechanism described by JA (other than maybe offering a not-so-awesome bound on the roll off). Nor how having 5k of output impedance with the SYS would result in even more roll off. Instead, I would be concerned about thermal noise and voltage drop across the output impedance of the passive pre-amp. Did you mean level drop?

    IMO, there is always going to be trade offs. Just make sure you pick the best possible part for your system. Don't just go for > $500 or > $10k as your main benchmark. Sometimes the super affordable no-pre-amp may be the best approach. Throwing $ at a problem is not always going to give you what you want. However, if the $16k solution brings joy, then life is good.
     
    Last edited: Jul 31, 2018
    ultrabike, Jul 31, 2018
    #62
  3. famish99

    famish99 Friend

    Pyrate
    Joined:
    Dec 26, 2017
    Likes Received:
    1,714
    Trophy Points:
    93
    Location:
    Austin, TX
    famish99, Jul 31, 2018
    #63
  4. ultrabike

    ultrabike Measurbator - Admin

    Staff Member Pyrate MZR
    Joined:
    Sep 25, 2015
    Likes Received:
    8,960
    Trophy Points:
    113
    Location:
    Irvine CA
    BTW @trung225, don't get bend out of shape about my opinions on that XP-30 pre-amp or that other Ayre whatevers. Mine are just another set of opinions. Also, I've been known to f**k up often.

    If you have positive experiences with those equipments don't hesitate to share.
     
    ultrabike, Jul 31, 2018
    #64
  5. trung225

    trung225 Facebook Friend

    Joined:
    Oct 22, 2015
    Likes Received:
    123
    Trophy Points:
    43
    Sorry I made a mistake in saying the roll-off with Sys. About the roll-off of the Pass's preamp, it is likely because of the phase shift forms by a output capacitor and the load resistance.

    We can easily predict the output capacitor of Pass preamp from the JA's measurement.
    With 600 Ohm resistive load, the characteristic frequency (-6dB roll-off) is around 25 Hz, so the capacitor will be 1/(2*Pi*25 Hz* 600 Ohm) = 10 uF.

    With 10K Ohm load, so the characteristic frequency will be 1/(2*Pi*10 uF * 10000 Ohm) = 1,6 Hz, so roll-off will begin at 16 Hz.

    In the real situation, the load is not only resistive, so the result will be worse. But I think there will be no problem with 10K Ohm load, if the interconnect cable doesn't have too much capacitance.

    Yes, the price is high, but considering all of discontinued JFET/MOSFET, and the curve tracking and matching process, R&D, testing (both through measurement and hearing), and dealer/distributor cost, plus huge variety of feature (much more than normal preamp), I think it isn't overpriced, and I said it as a starve diyer who can't afford spending one ten of that for preamp.
     
    Last edited: Jul 31, 2018
    trung225, Jul 31, 2018
    #65
  6. trung225

    trung225 Facebook Friend

    Joined:
    Oct 22, 2015
    Likes Received:
    123
    Trophy Points:
    43
    I don't have good experience with passive preamp using resistive volume control. The good thing is they are all pretty transparent, but they also suck the life out of the systems. In my humble destop system, adding the Sys between my Gungnir Multibit and LSR305s results a bit thinner sound with reduced dynamic in comparison to direct connection. In two other systems I have a chance to hear the result is the same.

    Personally, I think resistive volume control really needs a active stage after it to perform, either a buffer or a gain stage.
    For a passive preamp, I think AVC (autoformer volume control) is a better choice, but the good AVC is not cheap, in fact, expensive, especially if you want something like nanocrystalline core or silver wire.
     
    Last edited: Jul 31, 2018
    trung225, Jul 31, 2018
    #66
Page 4 of 4

Share This Page