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Discussion in 'High-end Audio Forum' started by magiccabbage, May 14, 2015.
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  1. Drewligarchy
    That's a correct definition - but isn't it incomplete? For instance, if I overdrive the input will it not cause distortion, even if it's not completely audible?

    From this MSB page on Preamps. I don't know why a headphone amp would be any different:

    Active preamps add gain. Signal levels can exceed the preamps capability in two ways. If the output clips, sound is distorted at high volumes. If the input clips, sound is distorted at all listening levels.


    Am I misunderstanding something?
  2. JaZZ Contributor
    Of course the input can be overdriven, but that has nothing to do with the figure for input sensitivity.

    With the max. output set to 2 volts on DAVE you should be safe.
  3. Drewligarchy
    Thanks. I've been having fatigue, so I thought I was creating subtle distortions. I thought that overdriving the input would result in distortion. Truthfully, I am trying to understand the concept as well as possible.
  4. ecwl
    My take on this is that the first thing is to not think about clipping first. Sure, DAVE can clip your headphone amp and cause distortion. But your headphone amp's analog volume control will probably cause quite a bit of distortion compared to the digital volume control. Usually, the analog volume control distortions are directly related to low-level distortions or subtle channel imbalance. For most analog volume control, the volume with the least distortion and most equal left-right channel balance is around the 12 o'clock mark. Unfortunately, for most people, there is no easy way to measure where for each amp the distortion is the lowest on the analog volume control.
    So if I were to play around with things, I would leave the headphone amp volume control set at the 12 o'clock position and then just adjust DAVE volume. Hopefully, you won't need to crank DAVE into a volume setting where it'll digitally clip or it'll clip the headphone amp and it is still loud enough for you to enjoy the music.
  5. Drewligarchy
    I am specifically concerned about overloading the input @JaZZ - said that wouldn't do any damage. I'm reading the MSB (as well as other sources around the web) that says you can clip the input, in the analog domain, by applying to many volts.

    So if my input sensitivity is 1 volt, and dave is in dac mode at 3 volts - and I play something with 0dbfs peaks - would I not be getting square waves and distortion? I am trying to determine causes for the fatigue - and when things sound right, but I get pain, it's usually subtle clipping.

    I'm just confused on this issue exactly.
  6. JaZZ Contributor
    A 1 volt signal from the DAVE suffices to enable maximum undistorted volume from your amp. The 1 volt figure has nothing to do with an input voltage limitation for your amp. It may absolutely tolerate 5 volts or the like without clipping.

    I agree with ecwl that theoretically your best strategy would be using the DAVE as preamp – i.e. the DAVE's digital volume control – and setting your amp to maximum volume. It would automatically prevent input overload, too.
  7. Triode User
    I also think it might be a good suggestion of setting the amp volume to max and then just using Dave to control the volume. If setting the amp volume to max causes background hiss then just back it off (turn down the amp volume) until the amp background hiss (if any) becomes inaudible.
  8. Drewligarchy
    No hiss - good suggestion Nick. I was just trying to maximize SNR at the same time.

    You know my fatigue issues all too well. I noticed the 1 volt input sensitivity so I thought that could be the cause. After initially lowering the input on the Dave - I think things improved. But could be placebo. I need a few more days to determine if that's the issue.

    I actually ran it this way before I got the m scaler. Than at some point I stopped because I could more easily access the volume control.

    I see mixed things on the internet. At least based on most of what I've read, if you exceed input sensitivity you will clip. This is soft clippling and mostly unnoticeable. Others have said the amp could handle more. I need to experiment more.

    I used to have an LDR passive preamp that gave out a lot of distortion. It was audible, but didn't sound like clipping. I used that between amp and dac to have remote control volume. It actually sounded good. Noise floor modulation-esque. It was killing my ears. I took it out of the chain, after like a year, and all was well again.

    These things can drive you crazy, but when things don't sound harsh, and I experience fatigue - something is distorting. It's a bit maddening.
    Last edited: Nov 19, 2019
  9. JaZZ Contributor
    I admire your patience sticking to your misconception.

    Input sensitivity is not input voltage limitation – as explained multiple times, it's the (minimum) voltage required for full undistorted power at the output. So if you exceed 1 volt from the DAVE with the amp's volume turned to max., the amp will begin to distort – note: the output stage, not the input!
    Last edited: Nov 19, 2019
  10. Drewligarchy
    I misread your last comment when you said “you can overdrive the input” as it was ok. I realize now you meant it’s possible. Not that it’s ideal or ok.

    Anyhow, if input sensitivity speaks to max output and distortion on output, how do I know how much input voltage is ok before overdriving the input. That MSB link has me confused.

    This isn’t an audio nervous a question. Rather I am trying to determine the source of fatigue that I’ve experienced with distortion before. It may not be that at all. Just trying to go through the steps.

    I don’t want to monopolize the thread as it’s becoming not “Chord” related, however, if anyone has suggestions please PM.

    Incidentally I always appreciate your help Jazz. You help d me identify the isssue with the LDR but you probably don’t remember.
    Last edited: Nov 19, 2019
    JaZZ likes this.
  11. rkt31
    Even if the input sensitivity is 1v, it is difficult to drive the amp to distortion with higher than 1v because this 1v input is after the volume control. So if you feed say 2v from Dave , it will first attenuated by pot to some voltage well below 1v depending upon volume position in amp. Imho better to use analog volume control at highest possible position ( which gives least noise when no signal fed to amp ) and then adjust Dave's volume. This way you would avoid analog attenuation but there will be highest digital attenuation in Dave. So you can also experiment a bit between analog band digital attenuation.
  12. JaZZ Contributor
    Sorry if I sounded rude! All is good.

    It's impossible to know the maximum voltage for the amp's input without measuring or having manufacturer specs at hand. 2 volts are a common value, so it will be hard to find a component that doesn't accept it. However, if you set the amp's volume to max and have the DAVE control the volume level, you'll never have to worry about it. That's what I would do in your case.

    It's highly unlikely that your fatigue syndrome has its origin in said issue, though. Maybe just too much occupation with listening to music?
  13. rrolls
    This is quite interesting for me. I have been a follower of LDR volume control, but I have just used a cheap one for a short time. Now I would like to buy a Tortuga to complete my analog path. I have recommended one for a friend a year ago, heard his setup for an hour, and since then he has not complained. So I would like to see the evidence of these distortions. Obviously you have records of these and could show them here, so I can think about again. I have not found any charts about distortion or frequency response of Tortuga volume control, and if necessary I will not hesitate to ask them. Thank you for your note.
    Last edited: Nov 20, 2019
  14. rkt31
    Why at all use a pre in between amp and Dave ? Dave direct to a high input sensitivity amp like benchmark ahb2 is a lot better option than having any kind of pre in between.
  15. musickid
    can anyone give me a proper explanation about the reported bnc dropouts when connecting the mscaler? 1 and 2 then 3 and 4 inputs and so on. i'm considering a dave upgrade next year but worried about this.
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