Passive Volume Control for DACs/Sources

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

  1. Thenewerguy009

    Thenewerguy009 Friend

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    Simple if you can solder what looks to be dozens & dozens of tiny wires to small connectors.
     
  2. sfoclt

    sfoclt Friend

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    That’s for the cheapest model. Buy the next one up and you only have to know how to install a knob and solder rca connectors. It’s a simpler process than making an interconnect cable.

    Last week I saw two of the mid level Slagle autoformers on audiogon for $250.
     
  3. bazelio

    bazelio Friend

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    Yeah, probably very few folks are building their AVC with a loose autoformer as the starting point when for a couple hundred extra you can get it pre-wired to the switch decks. Then it's just a matter of wiring up inputs and outputs, and is a beginner level project at that point.

    Figure, new from Slagle, $425 for the minimalist pre-wired standard taper AVC.
     
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  4. wormcycle

    wormcycle Friend

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    I know this is why it is so disturbing, although I sent the unit to Goldpoint I doubt very much they will find anything wrong with the wiring. I think the best I can hope for is that they find out what got fried and it will not cost a fortune. When I looked inside it is simple soldering as long as I get parts.
    I was testing the Bryston 2B LP power amp with SAX1, the DAC is BDP-2. The amp was working with Big Knob before, no issues. It happened when I turned on the amp. Thankfully the 2B is gone, working with no issues in my friend's home theater setup. I have no idea what went wrong and how I could have prevented it.
     
  5. ogodei

    ogodei Friend

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    As said above the goldpoint has no power, so if its burnt it took a surge from something else. Betting me says there was a short in the amp somehow, say you directly-coupled a speaker output or two by having the cables crossed by accident. When you turned on the amp the power ramp up combined with the short, power arched inside the amp to the input lines, then smoked the first resistor it came to.

    Would be a pretty random event but makes sense to me.
     
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  6. Argopo

    Argopo Acquaintance

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    "Say hello to my little friend..."

    [​IMG]

    So, this is my DIY autoformer. I wound the AVCs myself at Dave Slagle's place when he still had the loft in New York. This is many many years ago. Winding magnet wire onto bobbins is the most stressful form of DIY. Huge respect for guys like Dave Slagle who make these parts for us DIYers.

    Just look at that rat's nest. Complete disregard for good wiring techniques. Looping wires, un-twisted signals. Kinda of a dumb way to ground the RCA chassis connectors. Good lord what an eyesore.

    This AVC has been sitting on my shelf for years. Since I gave up on speakers for headphones, I had no need for a single-ended preamp since I needed balance for my headphone amp.

    But, in late 2018 I went back to speakers. Been using my Freya as the preamp of choice for both my headphone amp and speaker amp. Recently, because of @rlow 's experience with the Schiit SYS, I decided to swap out my Freya for the SYS for my speaker system.

    But, then for shits and grins, I decided to dust off my DIY AVC to have a listen.

    Shockingly, it actually sounded pretty good. Totally forgot how good magnetic volume control was. Also, no buzz, no hum no noise despite the nasty wiring.

    Now, because of @bazelio and @sfoclt and their DIY efforts with Dave's silver AVC, I am considering ordering Dave's current silver versions. And putting it in a nice box. But, with a cleaner approach to layout and wiring.

    Here are the side views:

    [​IMG]
    [​IMG]
     
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  7. bazelio

    bazelio Friend

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    Haha just as I say most people probably buy the pre-wired switch decks, this guy shows up with autoformers that he wound and then wired up entirely himself.

    Fun project, and impressive job!
     
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  8. randytsuch

    randytsuch Facebook Friend

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    A long time ago, I picked up a pair of the SB tx102's, they were the pair used for the Bent Audio prototypes. Bent used tx102 before changing to Slagles.
    Used it for many years, but traded it a while ago for a tube amp, a trade which I regret lol.

    I've been thinking about picking up the Slagle AVC for a long time.
    I'd skip the lower cost version myself, I'm not sure it has enough steps, and might be hard to get the volume setting you want with headphones. IMO, speakers are a little more forgiving for too much/little volume. I also don't like the idea of dual switches, I want to turn one knob to set the volume. I'm also not going to pay $750 for this, so I'd buy the bare AVC and a switch and wire it myself. I bought the bare tx102's and had to hand wire it, it was kind of a pain but not the worse thing I've built.

    Another thought would be to connect to a bunch of relays, and then you could implement a remote control pretty easily. Might be able to adapt something like a amb delta for this, not sure but seems possible. But that would be a bigger project, and I'm sure I'm too far into diy land already for this thread.

    One parting thought is that Tribute also makes autoformers. He seems to be in semi retirement mode, but I guess he still makes transformers that don't require any design work. Someone here bought some AVC's from Tribute recently. I don't know their cost, but from an ad I found they seem to be more expensive than Slagle.

    In the amp I just built, I used a Dact stepped. I pickup up a few of these a long time ago for a good price, so I had it available. I don't think I would buy them now at the current asking price.
     
  9. OJneg

    OJneg The Most Insufferable

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    Can I contact Dave to order silver AVCs? Anyone else thinking group buy?

    Edit: looks like hes selling them on the site but only the complete units. Might be worth it regardless
     
  10. sfoclt

    sfoclt Friend

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  11. OJneg

    OJneg The Most Insufferable

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    Yea I saw that. I was hoping for a 23 position (which I found sufficient for headphones or speakers) autoformer that I could wire up myself. The standard Cu ones go for $200 a pair... maybe the Ag ones would be $400-600?
     
  12. sfoclt

    sfoclt Friend

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    Gotcha. I'm sure you can email Dave to see what he'll do. It's all handmade to order anyway.
     
  13. randytsuch

    randytsuch Facebook Friend

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    From what I can tell, $200 gets you a 14 position AVC. IMHO, not enough steps.
    $400 will get you a pair of 28 tap AVCs, in copper. And silver seems to more than double the costs.

    But page also shows a 23 tap AVC, mounted with switch for $425
    Seems like a good deal you if can live with two switches to control volume.

    Randy
     
  14. bazelio

    bazelio Friend

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    47 steps is overkill IME. I've probably never adjusted volume by a single 1.25dB step. That said, I think it's difficult to escape the non-trivial price increment. 50 or so feet of silver wire per side probably gets costly. I've also heard that, for some reason, the silver wire is more difficult to work with. One of the other passive pre companies recently said fuck it and stopped offering a silver version of their TVC. Either MFA or Bespoke, I forget which. But whatever the challenge is, that might also be factored in to the asking price.
     
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  15. sfoclt

    sfoclt Friend

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    The smaller increments would be useful on the dual mono version to fine tune balance. I probably would have done that if he’d had that version up before (dual/silver/47 step).
     
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  16. colhd

    colhd Rando

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    I think it was me that you were referring to regarding the Tribute AVC, in my case last year. Cost at that time for a 23-step stereo unit was 435 Euro incluing VAT (sales tax) at 21%. A 4-gang unit for balanced designs was also available at a little less than twice the price. I have not heard from Pieter at Tribute recently so I do not know if these are still available.

    [​IMG]
     
  17. Armaegis

    Armaegis Friend

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    I've got a fancy TVC that's been collecting dust since I'm a schlub who uses digital volume control from his dac. Do I think the TVC sounds better in some voodoo way? Yep. Am I willing to give up my desk real estate for that? Nope. Sigh, I should probably sell it.

    This is mine: https://6moons.com/audioreviews/stereoknight/1.html
    (I know I know, 6moons, bleh, but I can't be bothered to take pictures)
     
  18. ogodei

    ogodei Friend

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    That is absolutely gorgeous. If you actually want to sell that you will have crowd of buyers, calling dibs now.
     
  19. Thenewerguy009

    Thenewerguy009 Friend

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    "the copper version of the balanced Silverstone retails at $1.450 and the silver version at $2.000. Remote control (what we call the Silverstone B&R) adds $400 over the manual version."

    Pricing isn't bad. Seems fair compared to the $3,000+ some are charging that don't look half as nice.
     
  20. Kernel Kurtz

    Kernel Kurtz Friend

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    If you are not using it and would not mind loaning it out I would really appreciate a brief listen......
     

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