Dared SL2000a Preamp Block Distortion?

zingozingo AudiophilePosts: 11,674
I was listening to music last night and the new Dared SL2000a tube preamp it had a fantastic sound stage and warm detail. However, when I was listening to an a cappella song that hit a big transient (they were stomping), the preamp would distort (almost sounded like clipping) during those points. I tried a pop song with similar transients and it did the same thing, but the distortion disappeared when I ran the source direct to the amp; and the sound quality decreased too.

My first thought was clipping or major microphonics? Since the Hafler amp had volume pots, I tried running it full with low volume on the pre, and low with full volume on the pre with the same results. The music was a bit loud but a reasonable volume that I use for dedicated listening.

I swapped the input tubes this morning, but also tried lowering the output on my source (iPhone which I was using last night as well) and the distortion went away. I found a discussion on "block distortion" online and it seems to be the issue I was hearing. I tried running my Squeezebox as the source and also didn't hear the problem, so I might have been overdriving the preamp, but I'll play around with it more as it doesn't seem like there is an issue with unit.

"Blocking occurs when the output tube grids are driven to the point of conduction. Since the previous stage is a relatively high impedance source, and, to make matters worse, is AC-coupled, it cannot maintain enough drive to the output tube grids to maintain the signal once the output tube goes into grid conduction."

Does anyone have experience with something similar?

Comments

  • ClipdatClipdat Posts: 4,712
    zingo wrote: »
    also tried lowering the output on my source (iPhone which I was using last night as well) and the distortion went away. I found a discussion on "block distortion" online and it seems to be the issue I was hearing. I tried running my Squeezebox as the source and also didn't hear the problem, so I might have been overdriving the preamp

    Input signal was too hot for the preamp to handle at that particular musical transient.
    Got Dayens?
  • heiney9heiney9 Posts: 23,860
    Really, an iPhone as an input? That's your issue right there. You can't run that kind of device and expect it to be high fidelity. It's not designed for that. That being in a hi-fi rig.

    Even if you turn it down, you can't get serious sound from an iPhone. I know we all have different types of rigs for different purposes and the convenience is nice, but don't use a device like that if you expect great sound, IMHO, of course.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • heiney9heiney9 Posts: 23,860
    edited September 10
    Clipdat wrote: »
    zingo wrote: »
    also tried lowering the output on my source (iPhone which I was using last night as well) and the distortion went away. I found a discussion on "block distortion" online and it seems to be the issue I was hearing. I tried running my Squeezebox as the source and also didn't hear the problem, so I might have been overdriving the preamp

    Input signal was too hot for the preamp to handle at that particular musical transient.


    More than likely the issue was the signal being too hot for the iPhone to process and probably overloading the output signal. I doubt it's the pre's fault. A device like an iPhone is not in any way shape or form designed to be a stellar hi-fi unit.

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30 | EE Avant Pre | EE Mini Max Plus DAC | MIT Shotgun S3 | MIT Z P/C's | updated SDA 1C| SQ Box Touch/Welbourne Labs P/S- Tubes add soul!
  • ClipdatClipdat Posts: 4,712
    edited September 10
    heiney9 wrote: »
    A device like an iPhone is not in any way shape or form designed to be a stellar hi-fi unit.

    I agree, Brock. Unless you are somehow bypassing the internal DAC/3.5mm headphone output.

    I guess the point of my post was that the issue lies with the source.
    Got Dayens?
  • zingozingo Audiophile Posts: 11,674
    heiney9 wrote: »
    Really, an iPhone as an input? That's your issue right there. You can't run that kind of device and expect it to be high fidelity. It's not designed for that. That being in a hi-fi rig.

    Even if you turn it down, you can't get serious sound from an iPhone. I know we all have different types of rigs for different purposes and the convenience is nice, but don't use a device like that if you expect great sound, IMHO, of course.

    H9

    I was mostly using my Squeezebox Touch, but wanting to do some testing with tracks on my phone, but had never had that result on any tube equipment before.
  • ClipdatClipdat Posts: 4,712
    Well at least you know there's nothing wrong with the preamp! I'm glad you were enjoying the "fantastic sound stage and warm detail"! Sounds like a real special unit!
    Got Dayens?
  • mlistens03mlistens03 Posts: 2,104
    edited September 10
    Clipdat wrote: »
    heiney9 wrote: »
    A device like an iPhone is not in any way shape or form designed to be a stellar hi-fi unit.

    I agree, Brock. Unless you are somehow bypassing the internal DAC/3.5mm headphone output.

    I guess the point of my post was that the issue lies with the source.

    You can bypass it with a DAC that has a USB input and the lightning cable, or you can buy Apple’s lightning to HDMI adapter. Both of these bypass the internal DAC. I’m sure there are more ways to do it as well.
    Not Tom, or Trey, or Jim
    In a few days, it will be...
    NAD C352
    Monitor Audio Radius R90’s/Polk SDA CRS/Mission Freedom 770 IV
    BJC speaker cables, generic RCA’s
    Technics SL3200 turntable and a Shure M97xE phono cartridge
    Velodyne VA-907 subwoofer
    Lafayette LR-1100 acting as a tuner
    TCC-TC750 phono stage
    I've always thought the goal of high end audio was not to have your neighbors bang on the wall and say, 'Turn that darn music down' but to have your neighbors bang on the wall and say, 'Tell your friends to go home and you can practice later this week'.
  • zingozingo Audiophile Posts: 11,674
    I agree after some more testing that the issue is the iPhone as a source, but I'm most surprised because I've never had that issue before with tube or SS equipment.
  • halohalo Posts: 4,363
    zingo wrote: »
    I agree after some more testing that the issue is the iPhone as a source, but I'm most surprised because I've never had that issue before with tube or SS equipment.

    I guess the Dared is a little more revealing? Maybe you should try it in your main rig?
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