Passive Volume Control for DACs/Sources

Discussion in 'Digital: DACs, USB converters, decrapifiers' started by Madaboutaudio, Dec 20, 2015.

  1. Ash1412

    Ash1412 Friend

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    Wait is this a universal rule? I was considering 12 db vs 6db passive in-line resistor attenuators for the Liquid Platinum. If 6db is the peak for output impedance then that explains how people thought the 6db changed sound more than the 12db.
     
  2. monacelli

    monacelli Friend

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    This behavior doesn't necessarily explain why a -12 dB attenuator would sound better, or more transparent, than a -6 dB attenuator. With appropriately selected resistances, you could construct the two attenuators so that they had the same output impedance. Playing around with my spreadsheet, I can produce results like that where the total resistance of the divider (pot) is 10k for the -12 dB case, and ~7.5k for the -6 dB case. So it's only true if the two attenuators are designed with the same total resistance in the divider circuit. For the price of a SYS, or OL switcher, I would be really tempted to just use one of those in place of in-line attenuators. But I can see certain applications where you wouldn't want to add another box, etc.
     
  3. GoodEnoughGear

    GoodEnoughGear Evil Dr. Shultz‎

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    I dug up the Steve Hoffman Bespoke vs Baby Reference post:

    "My thoughts on the BESPOKE AUDIO passive. It's big, heavy and beautiful. It has no sound whatsoever, it's accurate to the sound of the amplifier. If you love your amp, this is a good thing. If you want that little something extra, this is not a good thing. At $12,000.00 it is expensive for what it does.

    If one must have a passive, I think the British Music First Baby Reference passive is a better deal at much less money. I like it it for its strengths at its price. It does a few things that demonstrate an advantage to transformers rather than resistors for volume attenuation. By contrast, the Bespoke, IMO does not particularly make a case for any advantage of a TVC. It sounds very accurate, it is impressive in build quality, but the sound is not what I search for, particularly at its price. It can be described as neutral, and therefore an improvement from preamps that take away from a system's sound. But, other preamps I have heard can also be VERY close to neutral, while still either adding or preserving the audiophile nuances that are so important to us. lovers of fine sound

    Like the Audio Note UK equipment that I like so much, the MF Baby Reference helps to preserve (and maybe even emphasize) nuances, like liveliness and subtle detail. This is the "magic" that Warren and I talk about, even though it is subtle. The beautiful Bespoke sounds like it is probably more accurate, but it either has no magic of its own, or does not help the magic of the equipment it is associated with.

    Understand that for most people, the Bespoke with be the last pre they will need to buy. It does the job of raising and lowering the volume very well. It is also beautiful to look at, wonderfully well built and would be an asset to anyone who loves the sound of his amplification and desires nothing else in the system to change that. To this person, I say, go for it.

    More listening to the MF Baby Reference and the Audio Note active preamps will bring more understanding of wanting a preamp to be "neutral" but also wanting it to "make magic". Like Warren J. says, this seems to be a contradiction, which is why we continue to listen, evaluate, and think, while we enjoy the music."

    https://forums.stevehoffman.tv/thre...ie-review-post-35.472408/page-2#post-13750944
     
  4. Ash1412

    Ash1412 Friend

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    That makes sense. Thank you. I forgot to mention they are from the same brand so quite possibly share the same specs (the brand site doesn't post output impedance http://www.hlabs.com/products/attenuators/). And yes, they are quite overpriced for what they do compared to something like SYS, but being in-line, I can hook them up to the amp RCA inputs themselves and make the cable run essentially nonexistent to avoid your typical passive pre rolloff issue, and avoid the price of relay-based steppers.
     
  5. bazelio

    bazelio Friend

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    Yeah whatever. What the f**k is he even talking about. IME, unless a particular TVC is really a huge turd, then the audible delta between one TVC and the next is very small. So far, I haven't heard a huge turd. Just buy one of the lower priced Slagle AVCs, and you're 90%+ there at like 8% of the cost. And don't buy any AVC/TVC if you're looking for it to "help the magic of the equipment it is associated with."
     
  6. bazelio

    bazelio Friend

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    As much as I dig the 1990s cable TV set top box styling, I don't get it. Why would we need this slider resistor system?
     
  7. Forza AudioWorks

    Forza AudioWorks MOT: Forza AudioWorks

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    Once time allows one day I will and the same story is with speakers. I have nothing against luxurious goods though and in case of Bespoke it's quite visible to me where all the money go. Also the idea of updating a customer about assembly progress is cool if someone asks me.

    Over the years I've seen a lot of dressed luxuriously but quite generic sounding hardware with price tag I couldn't justify. Bespoke stands out in this regard and still has me interested. I have no idea if this small fascination of is justified, I'd have to give it a go first. But for now, after all I've seen on the pictures and IRL I'm constantly impressed.
     
  8. lcmusiclover

    lcmusiclover Friend

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    Hattor mini passive preamp has replaced my Emotiva XSP-1. Very well made, with a solid metal case and remote. Exactly 3 weeks from order to receipt through Mockingbirdaudio.com. Phillip at Mockingbird was great to work with.

    I’ve only listened a little, but it seems very transparent — so far I can’t differentiate between my chain with the Hattor and direct connection between DAC and amp.

    The Emotiva is actually very good, but adds a little color. Didn’t really notice it with my SS amps, but didn’t like it with my Liquid Platinum.
     
  9. lcmusiclover

    lcmusiclover Friend

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    Just a quick update:

    Hattor has definitely found a permanent home in my system, Emotiva will go up for sale. Apparently I really want as transparent a preamp as possible, and the Hattor is accomplishing that in my system.

    This is another step in my understanding of my own audio preferences. Emotiva was a little wet -- OK, even desirable, with SS amps and cans like Utopia/Auteur. Undesirable with LP tube/hybrid amp. LP is wetter than SS amps (Bryston and previously, Violectric). Desirable with most of my cans, but not with Empyrean, which I prefer with my Bryston. So I guess I can say that I like my sound damp, not wet :)
     
  10. bazelio

    bazelio Friend

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    Couldn't leave well enough alone. So, inspired by @sfoclt and @Hands favorite big black knob, I built another AVC. Anyhow, this time, I tried the silver Slagle autoformer. It was kind of a what the hell venture as my expectation going in was minor but audible changes versus my previous copper AVC. However, in reality, changes were surprisingly greater than expected. So much so that I eventually realized my tonearm SRA and damping settings were just not right previously. And after adjustments here and there, I'm quite happy with what is to me a definitive upgrade.

    Pics.

    [​IMG]

    [​IMG]

    [​IMG]
     
    Last edited: Mar 25, 2019
  11. Thenewerguy009

    Thenewerguy009 Friend

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    What sonic differences did you hear from that AVC to choose it over TVC & stepped attenuators like Goldpot & Khozmo?
     
  12. bazelio

    bazelio Friend

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    A resistor ladder isn't going to work in all systems. Didn't go there. I haven't tried a TVC either. The AVC is a simpler device that does what I want. The Slagle unit has the 47 step switch prewired to the stereo decks. Super easy to integrate.
     
  13. Armaegis

    Armaegis Friend

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    In theory an AVC would offer more linear performance but doesn't have galvanic isolation witchery which could be a pro or con depending on what gremlins you're fighting.
     
  14. monacelli

    monacelli Friend

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    I suppose the other cool thing about AVCs is that they have a very low output impedance over most of their usable range. So they would be well-suited for amps with a low input impedance (e.g., First Watt F7, at 10k). I found this plot on the [Intact Audio website] that compares the output impedance of an AVC (presumably the Slagle) with a 10k potentiometer-based attenuator (e.g., Schiit SYS). From the plot, it looks like the potentiometer would be more transparent in a bypass configuration (no attenuation), the AVC would be more transparent for medium attenuation levels, and the performance between the two would be really close with a lot of attenuation (-40 dB and beyond). That breakdown presumes that output impedance, and hence damping factor, is the primary factor in sound quality, which might be a bit reductive.

    [​IMG]
     
  15. frenchbat

    frenchbat Almost "Made"

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    Why would you need a pot (or volume control) in a bypass configuration?

    Medium volume control is where it's the most useful anyway. If you need to attenuate that much, it'd be more useful to make changes on the gain rather than brute force it.

    I really don't see the advantages of a pot, in the limits of that graph ofc. And yes I'm aware this is marketing material.
     
  16. monacelli

    monacelli Friend

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    I basically agree with that assessment. That was pretty much the point of the post, in fact. The note about the bypass was just an observation that Zout of the pot approaches zero at 0 dB, whereas for the AVC it doesn't.
     
  17. Cspirou

    Cspirou They call me Sparky

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    Whoa, how did you make those panels? FPE?
     
  18. atomicbob

    atomicbob dScope Yoda

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    The red line applies to any value pot or stepped resistor attenuator. 6 dB attenuation is where the pot is halfway between two ends. The effect a 5K+5K divider, 6 dB attenuation, will have on frequency response may be seen in the blue lines for the 6 dB attenuation graphs found here . Short, low capacitance cables will introduce less than 0.2 dB roll-off at 20KHz, worst case. What is missing from this discussion is the combined effect of LC network formed by the AVC inductance and cable capacitance.
     
  19. rlow

    rlow A happy woofer

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    Does anyone else think that @bazelio is going for a Marty McFly on this?

    ED9FA2A9-2375-44EF-9561-BF1A60E6697B.jpeg


     
    Last edited: Mar 26, 2019
  20. frenchbat

    frenchbat Almost "Made"

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    @atomicbob have you ever (or know a properly measured ref) measured same cable with different make for the plugs (rca or xlr) ?
     

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