WTB: passive preamp

Discussion in 'For Sale' started by rhythmdevils, Jan 23, 2023 at 1:44 PM.

  1. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    I've got an Ampandsound Kenzie Ovation that has no volume knob, so until I can find a Rev2 version of the amp, I need to use a pre and I'd like something better than the Sys.

    I don't know much about passive preamp brands or models out there, but I'm looking for something that is:

    Jottenheim size or smaller ( 2 1/4" tall max) plus Jottenheim WxD
    point to point wired, no PCB
    Nice pot that is not a stepped attenuator
    Not too expensive

    Let me know if you have something like that! Thank you!
     
  2. RKML0007

    RKML0007 Friend

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    Have you looked into TVC or AVC passive preamps? I use a SACThailand Minute TVC and Townshend Allegri+. They’re both superb and I love what they do in my 2-channel systems. Promitheus makes TVC’s at different price points. Above the Allegri+ price range Music First TVC and a few other autoformer passives that come up in the various passive preamp threads all over the web that start costing more than some amps.

    -Ron
     
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  3. Souldriver

    Souldriver Almost "Made"

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    When you get the preamp try the EC with the volume maxed. I feel it gets a bit more low level detail. Happy hunting.
     
  4. fallbalance

    fallbalance Rando

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    I second the TVC recommendation, but with a couple caveats -- first, usually these are at least ~$700-ish and up (transformer cost). Second, you said you didn't want a stepped attenuator, which by nature is inherent in the design of a TVC.

    Here's a cool and quirky idea. Grab some quality in-line attenuators (such as "Ultimate Attenuators"), and match them to whatever you consider your max SPL. Then, from there, control your volume digitally... I know, I know, sacrificing true bit-perfect playback is a downer, but it's usually the 'lesser of two evils' between this and even the best pre-amps. I'm of the belief that digital volume control is superior to anything as long as you don't attenuate below about 65%. A TVC is an exception, and usually a superior solution, because it gains in current as you drop in voltage, enhancing lower level listening with clarity and drive. Every other pre-amp design throws the extra voltage away as waste in the form of heat (resistors).

    Of course, this suggestion comes with its own caveat: you would have to be using a streaming / file based source (no analog). If you happen to be using Roon, check out Roodial -- it's a very nice way to control digital playback using a physical dial.

    A note about stepped attenuators -- not sure why you don't like these, but they are almost universally a 'step up' in quality from a standard variable resistor / potentiometer. You just have to learn to dig the 'click click click' as you adjust :).
     
  5. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    I am using this with very sensitive headphones - LCD-X, LCD-4z and my modded S12 ortho iems. So I'm always using the first little bit of the volume range, and with a stepped attenuator there usually isn't enough play between steps and it's either too loud or too quiet. I don't mind the concept, but I think I'd need 200 steps or a preamp set to lower gain.

    I'd love a TVC but they're huge and wouldn't fit in my rack right now. Plus, this is mostly a temporary fix until I can get a version of this amp with a volume knob like it should have been.

    Thanks!
     
  6. RKML0007

    RKML0007 Friend

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    Have you seen this? Not point to point but cheap enough with a pot?

    Edit: nvm doesn’t fit other criteria as well.

    -Ron
     
    Last edited: Jan 24, 2023 at 8:52 AM
  7. fallbalance

    fallbalance Rando

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    Ah, I see.

    If you're at the very bottom range of a potentiometer, you're likely compromising your performance noticeably. Almost all of your voltage coming from upstream is getting thrown away, making for a rather 'delicate' signal being passed downstream, only to once again be amplified... this is a common gain structure issue that most people have to one degree or another. Additionally, most potentiometers don't perform quite as linearly when right at the bottom of their ranges. If you wanted to stick to this configuration, I'd just keep using the Sys -- as far as passive pre-amps with a variable resistor, I don't know if you'd find anything enough of an improvement over the Sys to justify the price paid, especially if this is just a temporary solution.

    I suppose the First Watt B1 might be a step up, but at a much higher price, and I'd rather put the same funds into a TVC personally.

    You could try the in-line attenuators + digital volume, which is economical and you may be able to use the attenuators in future configurations as well. This should give you very fine control, while also slightly limiting the amount of resistance you're applying to the analog signal.

    If you're using Roon, the 64 bit floating point volume leveling can be a great ally for your situation.

    Again, with such sensitive transducers, I think a TVC would be the ultimate solution -- all that voltage converted to current for a more robust signal and better low level performance... In this case, you could just set it at the ideal 'loudest' setting, then fine-tune your adjustments from there digitally. It would be worth making space for one -- the passive versions aren't that large anyways. It's something you might keep for life too...

    To add personal experience -- For years I've loved my OG Schiit Saga (stepped attenuator) with a GE Red Label on buffer duty. When I purchased an Audio Zone Pre-T1 (TVC) last year, and controlled the volume digitally as mentioned above, I found it to be a step up. I also have sensitive transducers in the form of full range drivers, so I'm in a similar situation.
     
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    Last edited: Jan 24, 2023 at 9:49 AM

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