Passive Volume Control for DACs/Sources

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

  1. rlow

    rlow A happy woofer

    Friend
    Joined:
    Jul 18, 2017
    Likes Received:
    2,068
    Dislikes Received:
    3
    Trophy Points:
    93
    Location:
    Canada
    I was reading some guy’s forum post on another site the other day, and wasn’t sure whether his opinion could be trusted, so I checked his profile and noticed a link to a gallery of his system. First pic was a fairly nice, neat organized looking home system - Primaluna integrated, generic nice looking tower speakers, etc.

    Next pic was the back of his system, including crazy thick white garden hose speaker cables, complete with speaker cable risers. I threw up in my mouth a bit. The rest of the cabling looked similar. The guy has probably spent as much on what is connecting his system, as what’s actually making the sound.
     
    Last edited: Apr 25, 2019
    ultrabike, Soups, bengo and 3 others like this.
  2. bilboda

    bilboda Wow, I made it this far without being a friend?

    Contributor
    Joined:
    Nov 20, 2016
    Likes Received:
    270
    Dislikes Received:
    1
    Trophy Points:
    63
    Location:
    Miama
    Picked up a nice dual mono Khozmo Akustic from beemerphile in the fs forum.
    Clear Step from the SYS and my chifi passives.

    JBL LS3xx have 10kohm impedance though and I thought I could do better so I did.

    Took a chance on a 90's line stage with 3db gain sold as the Harmonic Recovery System Model 2 by SCE.
    Made at time when the internet was still young, there wasn't a lot of info but what there was , was pretty good.
    Very nice build, so I bought it, opened it up very clean, looks like new and installed it .
    100kohm input, 300 ohm output, IIRC, it sits between the Akustik and the JBL's and their 9 ft cables

    And it sounds great, across the board clearer, drum hits and mishits are more apparent, notes last longer, cleaner base.
    Likely a lot to do with better matching. Easier than building a Pass diy B1, I think any passive pre amps would benefit.

    System

    [​IMG]

    from the web
    [​IMG]
     
    gridmaster likes this.
  3. MrTeaRex

    MrTeaRex His head's not fat, he's my brother!

    Friend
    Joined:
    Apr 26, 2017
    Likes Received:
    805
    Dislikes Received:
    4
    Trophy Points:
    93
    Location:
    Houston, Texas
    bengo, JK47, rlow and 1 other person like this.
  4. wormcycle

    wormcycle Friend

    Friend
    Joined:
    Aug 13, 2016
    Likes Received:
    387
    Dislikes Received:
    14
    Trophy Points:
    63
    Location:
    Toronto, ON, Canada
    My Goldpoint SA1X arrived two days ago to replace BHA-1 as a preamp to Bryston 4B SST.
    I have never been satisfied with Bryston BHA-1 as a preamp. It is a good HA, very good with HEKv2, but the preamp output was just too high, I could only use like 15% of the pot, could not get the center stereo image exactly right. And harsh treble on the top of it.

    I tried Palmer Monicon and Big Knob in the same setup with Bryston stack: BDP-2, BDA-2 and 4BSST
    Big Knob is good, input and output switching is flawless but I still heard some noise in my speakers (Totem Hawks 6 Ohm) that was not present with BHA-1, and I was still not satisfied with the center image and instrument separation.

    In my new setup a custom four feet XLR Y Mogami cable (Take Fife Audio) connects BDA-2 balanced out to BHA-1 and SA1X.
    Plying Nora Jones, Little Room track the vocals were coming right from the center, and instrument separation was better than with BHA-1.
    So far I spent maybe 6-7 hours listening and treble is still prominent but not harsh, improved microdynamics is very noticeable.

    I really like the results. The Y cable on the DAC input does not seem to make any audible difference.

    Still Big Knob works great as an audio input selector next to my TV, and Monicon is more than enough to control LSR305.
    But with the Bryston stack SA1X is clearly better.

    Thanks to @atomicbob for SA1X and SA2X measurements, combined with this thread it was very interesting reading.
     
  5. wormcycle

    wormcycle Friend

    Friend
    Joined:
    Aug 13, 2016
    Likes Received:
    387
    Dislikes Received:
    14
    Trophy Points:
    63
    Location:
    Toronto, ON, Canada
    Update on Goldpoint SA1X, not a good one,maybe you can advice something.
    I turned on the main amp and fumes came out of SA1X, the pot still works, sort off, but speakers make a wild cracking sound whenever I change the volume. I was entirely confused what went wrong, disconnected SA1X and connected everything to my normal preamp. Everything works fine. But SA1X stinks like something was fried inside. The stack is all Bryston so it was not some other weird stuff that failed.
    There is no serial number on the unit, and I bought it second hand on Canuck Audio Mart, it looked like never used before when it arrived.
     
  6. Thenewerguy009

    Thenewerguy009 Friend

    Friend
    Joined:
    Oct 11, 2015
    Likes Received:
    299
    Dislikes Received:
    14
    Trophy Points:
    63
    Can you take a picture of the insides?

    The Goldpoint just passes the signal, it doesn't have any power cord connected to it to power it, right?
     
  7. GoodEnoughGear

    GoodEnoughGear Evil Dr. Shultz‎

    Friend
    Joined:
    Oct 25, 2015
    Likes Received:
    1,746
    Dislikes Received:
    10
    Trophy Points:
    113
    Location:
    Cape Town, South Africa
    No power cord...purely passive.
     
  8. wormcycle

    wormcycle Friend

    Friend
    Joined:
    Aug 13, 2016
    Likes Received:
    387
    Dislikes Received:
    14
    Trophy Points:
    63
    Location:
    Toronto, ON, Canada
    As @GoodEnoughGear said it is a passive volume control, no power
    [​IMG]
    [​IMG]
    That's the picturu from Goldpoint web site. I opened my unit and the red and yellow (right input and left output wires are fried:, isolation is brown, and the chassis paint above those wires is damaged , looks like by flames.

    [​IMG]
     
    Last edited: Jun 4, 2019
  9. bilboda

    bilboda Wow, I made it this far without being a friend?

    Contributor
    Joined:
    Nov 20, 2016
    Likes Received:
    270
    Dislikes Received:
    1
    Trophy Points:
    63
    Location:
    Miama
    You'l have to open it up and look for shorts and broken resistors, loose solder, etc.. The switch itself could be failing which may be hard to see but should be obvious when turning the dial. Solder touch up or resistor replacement may be the answer.
     
  10. rlow

    rlow A happy woofer

    Friend
    Joined:
    Jul 18, 2017
    Likes Received:
    2,068
    Dislikes Received:
    3
    Trophy Points:
    93
    Location:
    Canada
    How long ago did you buy it? Did you get the original receipt? Could you contact the seller to see if he has it? You may be able to get warranty support from Goldpoint.
     
  11. wormcycle

    wormcycle Friend

    Friend
    Joined:
    Aug 13, 2016
    Likes Received:
    387
    Dislikes Received:
    14
    Trophy Points:
    63
    Location:
    Toronto, ON, Canada
    The seller bought it on July 15 2018 directly from Goldpoint, I have the original order and paypal receipt. I bought from him few weeks ago and the unit was new. He is a good guy and is helping me.
    Contacted Goldpoint and waiting for response. The chassis inside looks like this thing was literally on fire for few secs. I a bit disappointed, everything is connected to pretty good power conditioner, grounded etc.. So fingers crossed..
    But I was scared like hell for a moment I did not now where the fumes were coming from. But everything else works when I connected BHA-1 as preamp in place of SA1X.
     
    rlow likes this.
  12. atomicbob

    atomicbob dScope Yoda

    Friend BWC MZR
    Joined:
    Sep 27, 2015
    Likes Received:
    8,904
    Dislikes Received:
    3
    Trophy Points:
    113
    Location:
    On planet
    The Goldpoint is a completely passive device. It has no power supply, stores no energy and is not capable of the damage described. Normal audio line level signals also do not have the energy to cause such damage. The source and output devices to which the SA1X was connected must have developed a significant potential between them for such damage to be possible. If so, this is a dangerous situation and should not be taken lightly.

    Measuring AC and DC voltages on the various pins between source and output devices would be prudent. Do this carefully as if a fault exists, risk of electrocution is possible.

    In my lab, dozens of DACs, Amps, Preamps, and other devices have been interconnected using SA1X, SA2X, SA1 and SA2 with no such damage ever occurring, no sparks, no potential differences (voltage.) No trouble hot patching either, provided downstream equipment is suitably muted or electro-acoustic drivers (headphones, speakers) disconnected.
     
  13. Thenewerguy009

    Thenewerguy009 Friend

    Friend
    Joined:
    Oct 11, 2015
    Likes Received:
    299
    Dislikes Received:
    14
    Trophy Points:
    63
    I have been scouring the internet for different passives & the prices are ridiculous if you want to try something above the Sys or Khozmo/Goldpoint price points with a transformer.

    I did find two Chinese Transformer volume controlled passives, both for around $150-ish.

    https://www.ebay.com/itm/HiFi-10K-4...eamp-Permalloy-Audio-Transformer/254164032876

    https://www.aliexpress.com/item/4-w...mer-converter-passive-preamp/32994541826.html

    Anyone with a good eye on what to look for, to know if they would be decent buy or should I stay away?

    Mind you in my search, every other TVC or AVC is a minimum of $900 (except for Prometheus) & most averaging close to $2,000, all while having the internals look exactly like those two cheap Chinese preamps. Two very small transformers with wires connected to RCA inputs & outputs & a potentiometer. Some with a lot with much more sloppy wiring that the two above as well.
     
  14. Taverius

    Taverius Smells like sausages

    Friend
    Joined:
    Dec 27, 2017
    Likes Received:
    1,818
    Dislikes Received:
    7
    Trophy Points:
    93
    Location:
    Rapallo, Italy
    Tbf that's because good transformers are fucking expensive.

    There's a reason a SET costs so much more than an OTL, and a silver dna stellaris commands a four figure premium over the normal version.

    Not saying all those trafos are good, but good trafos are not cheap.
     
    bengo likes this.
  15. Thenewerguy009

    Thenewerguy009 Friend

    Friend
    Joined:
    Oct 11, 2015
    Likes Received:
    299
    Dislikes Received:
    14
    Trophy Points:
    63
    I think I saw aliexpress selling those small transformers for like $15 or something. None of these TVC/AVC preamps have massive transformers that you see in SET or power amp. They are tiny transformers that can fit in the palm of your hand & they are sold dirt cheap.

    Even the $3,000 TVC I I see, have those small trafos as well. Maybe a bit better quality, but I can't see the price of them alone being hundreds of dollars.
     
  16. Thad E Ginathom

    Thad E Ginathom Friend

    Friend
    Joined:
    Sep 27, 2015
    Likes Received:
    5,261
    Dislikes Received:
    10
    Trophy Points:
    113
    Location:
    India
    Well, pre-amps have always been expensive. My audio antique, currently sitting in the repair man's shop while I decide if I want to spend money on its restoration) was $1,000 two decades ago. Transparent, it seems, was (and still is?) expensive.

    Want a piece of wire with gain? That's going to cost you a lot. Hmmm... looks like a piece of wire with just attenuation might cost at least as much.

    Something cheap from ali-express? Try it. You might get lucky. We all love a giant killer! Or if you really think that the sum is too much for the parts, buy the parts and DIY.
     
    Lyer25 and bengo like this.
  17. Cspirou

    Cspirou They call me Sparky

    Friend
    Joined:
    Sep 27, 2015
    Likes Received:
    4,401
    Dislikes Received:
    5
    Trophy Points:
    113
    Location:
    Northwest France
    Smoke out of a passive preamp is really weird. Usually shorting the input of an amp is not a problem, but shorting the outputs of source gear can be an issue. However output impedance is usually high enough to where you shouldn't get smoke.

    If you really did get smoke you should have some black marks in there somewhere. Open it up and investigate.
     
  18. Thenewerguy009

    Thenewerguy009 Friend

    Friend
    Joined:
    Oct 11, 2015
    Likes Received:
    299
    Dislikes Received:
    14
    Trophy Points:
    63
    Yeah, I'm going to test my luck & buy one of them. Better than spending over a grand on one of the other boutique brands that don't really seem to be built better internally.

    Anyone know which of them would be better from the spec they give? I'm clueless on this stuff. There seems to be two differences between them.

    The eBay one is 100K chip stepped potentiometer.
    The Aliexpress one has a 24-stepped potentiometer.

    The eBay one has the primary and secondary inductances of 1320H to 1380H.
    The Aliexpress one has the primary and secondary inductances of 1000H to 1600H.
     
  19. sfoclt

    sfoclt Friend

    Friend
    Joined:
    Nov 24, 2015
    Likes Received:
    802
    Dislikes Received:
    0
    Trophy Points:
    93
    Location:
    Online
  20. Argopo

    Argopo Acquaintance

    Joined:
    Oct 22, 2015
    Likes Received:
    80
    Dislikes Received:
    0
    Trophy Points:
    18
    Location:
    NYC
    @Thenewerguy009

    Those two passive units are not TVC.

    They are 1:1 or 1:4 isolation transformers coupled to resistor-based pots using SMD resistors. The transformers isolate or provide a step-up in gain, and the resistors attenuate volume.

    TVC units and AVC units attenuate volume using the windings on the bobbins.
     
    Thenewerguy009 likes this.

Share This Page