The Audio 101 Thread

Discussion in 'General Audio Gear Discussion' started by sphinxvc, Nov 12, 2016.

  1. Valolilol

    Valolilol Facebook Friend

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    I like the image of the "Third order descriptor".
    @GoodEnoughGear or @Garns can you tell why are you saying :
    I feel that it is true but I cannot put words on it. For me ringing shows you that the headphones has issue to release some energy at some frequencies. But I do not see it as a REAL big deal.
    Behind that here is my problem : the description given here :
    is the one of a very good headphones. I think it will lead to good timbre too, but just because if you respect those criteria you have a good headphones. I would like to narrow down those criteria just in term of timbre. Or at least, justifying (just giving some hint) all those points.
     
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  2. Kunlun

    Kunlun cat-alyzes cat-aclysmic cat-erwauling - Friend

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    [​IMG]
    Now this is the kind of discussion I wanted to read!
     
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  3. Malabargold

    Malabargold Flipper

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    Here's a great video explaining the differences between linear and switching power supplies and how each type work. It was very useful for someone like me who has no background in EE.
     
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  4. GoodEnoughGear

    GoodEnoughGear Friend

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    Hi folks,

    I spent much of this weekend understanding input and output impedance and voltages for sources and loads. I think I finally have a basic grasp on things, but I'm a little unsure of some of the specs I'm seeing on gear.

    I worked through understanding how, for a voltage source (like a DAC), you want low output impedance and high input impedance on the load (like an amp), so the load draws little current and the voltage is affected minimally, allowing the load to receive a solid signal for lack of better term.

    I then went into line-level voltages, and the difference in unbalanced and balanced voltage. This is where I'm getting a bit lost. The following is presented as a general standard (via Wikipedia):

    [​IMG]

    Bifrost has a peak 2V, against a standard of 0.447
    Saga has a peak of >10V against a standard of 0.447 :eek:!
    Schiit Yggy and Gumby have peak 4V, against a standard of 1.736

    If a load, like a power amp, is expecting a line input that's somewhere in this range, why are the Schiit line out voltages exceeding the standard by so much? What am I missing? Is something shifting the ref levels that Schiit gear uses upwards, so we have equivalent VPP, or is something else going on?

    Feeling slightly stupid in anticipation...
     
  5. Garns

    Garns Friend

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    It's basically because analogue and digital are referenced differently. In the digital domain you have 0dbfs which is full volume and everything else is lower than that (-6db, -12db, ...). In analogue the 0dBu reference is purely nominal and is not designed to be a maximum but rather a kind of general baseline to aim for; output levels between different pieces of gear can vary wildly from that baseline. In principle you can keep going up as far as you want above 0 so long as your gear can handle the volts. Old Neve mixing desks can handle over +28dBu (about 20V). Most pro gear is referenced against +4dBu. In these terms Yggy/Gumby output is not far off that at +8dBu.

    That being said, it is true that the output from Yggy/Gumby can be a bit hot for some gear. The output of a lot of pro gear referenced against something close to +4dBu may likewise be too hot for stuff referenced against -10dBV. Or it may not, if the gear has enough headroom.

    EDIT: be sure to distinguish peak, peak-to-peak and rms voltage values. The figures you quote are actually RMS (root mean square) values rather than peak or peak-to-peak values. For an actual signal, the relationship between the three can vary, but in quoted values like this peak is sqrt(2) * RMS and peak-to-peak is 2 * sqrt(2) * RMS value (this is the relationship holding for a sine wave as in your diagram). Here's a calculator for going between all of the various standards: http://www.sengpielaudio.com/calculator-db-volt.htm
     
    Last edited: Nov 28, 2016
  6. GoodEnoughGear

    GoodEnoughGear Friend

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    Thanks, @Garns - let me go back make sure I'm grokking it.

    [Edit] OK, getting there. Thanks for the pointer to the calculator - makes things a bit easier, but it's actually good to work through the logic with a simple calculator first :).

    Thanks for pointing out the Schiit figures are RMS...that makes the balanced peak volts 5.65V from Gumby, it seems. And also noted that these limits aren't a standard but rather a common practice, so from an interoperability standpoint it's what your gear will handle, really.

    The reason I started looking at this is to see if I could take a line directly out of Gumby into a Genelec 8020C monitor. Based The 8020C specs:

    The input Sensitivity of the 8020C with volume wide open is -6dBu for 100dB SPL at 1 meter
    The max sustained output for the 8020C is 95 dB SPL at 1 meter

    Maximum input then (-6dBu -5dB) = -11dBu to generate 95 dB at 1m with the volume wide open.

    If we have a peak 4V RMS output from Gumby, that equates to 14.26 dBu, meaning the input would be 25.26 dB too hot with the volume wide open. I'd need to dial out 25.26 dB using the volume control to allow the maximum possible input from the 4V RMS source to produce the maximum 95 dB output from the 8020C.

    The volume control range on the 8020C is 80dB. That means I need to dial back the volume by 31.575% to compensate for the overshoot and accommodate the dynamic range of the 4V RMS input completely within the output capability of the monitor.
     
    Last edited: Nov 28, 2016
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  7. Marvey

    Marvey Loves sex and records

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    Reopened thread. Not sure why this was locked.
     
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  8. ultrabike

    ultrabike Measurbator - Admin

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    You logic sounds reasonable to me. I would give it a little extra headroom just in case.

    You are planning on controlling the volume digitally through the computer? Or would you want to add external volume control ("pre-amp")?
     
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  9. GoodEnoughGear

    GoodEnoughGear Friend

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    This is more a bit of thinking out loud to understand if it would work. Step one could be Genelecs and then max out on the DAC and get a pre sometime later. I can swing the Genelecs and a Gumby now for example an that would take up the current budget.

    [Edit] So yes, PC/JRiver volume control initially.
     
    Last edited: Dec 1, 2016
  10. Poleepkwa

    Poleepkwa Almost "Made"

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    http://www.genelec.com/studio-monitors/outboard-products/9000a-stereo-volume-controller
    Would this be usefull in your case?
     
  11. GoodEnoughGear

    GoodEnoughGear Friend

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    Meh...it's a simple stereo device so you'd have to go SE out of the DAC to stereo 3.5mm and back to dual XLR and lose the balanced output to put it in the chain. The version for the digital SAM monitors is much better integrated, but I don't want embedded DACs and DSP in the monitors - that would take ALL the fun out of it :).
     
  12. Poleepkwa

    Poleepkwa Almost "Made"

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    Sure, but its cheap and will prevent pretty loud "accidents" untill you get a preamp - which I am not sure you will need, if you do not need any other inputs. In theory the best sound will be as you have it planned - DAC to Genelec. In my experience room eq and DSP has bigger effect than the differences between DACs, ( balanced or SE, etc). Genelec DSP models does limit the FUN of swapping gear though ,but opens up a can of worms with mic positions, cut of freqs and so forth.
    Would be interesting to hear your thoughts of course once you get it up and running.
     
    Last edited: Dec 2, 2016
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  13. GoodEnoughGear

    GoodEnoughGear Friend

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    Plan would be to reduce input sensitivity on the 8020 to a little above my normal max listening level (I don't listen loud) and then use digital volume control for very minor tweaking. There'd be no chance of any loud accidents that way. If I really want to crank it, well, the 8020 controls are on the front and pretty readily accessible. |\/|
     
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  14. Poleepkwa

    Poleepkwa Almost "Made"

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    So true! I totally forgot they have the input volume at the front, unlike the 8040/8050's
    Any reason why the 8020 and not the 8030 - apart from the cost?
     
  15. GoodEnoughGear

    GoodEnoughGear Friend

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    Well, Genelec claims that there is not much difference sonically other than bass extension and SPL between their monitors in the same family. With a sub, even the 8010 should cover down to the 85Hz crossover effectively, but it doesn't have the input sensitivity control (aside from a couple of dipswitch settings on the back) which is something I really do want. The 7050 sub would get me down to 25Hz with the option to go 5.1 at some point, so I'd go that way rather than the 7040.

    Second, I have a small room they'd live in, and I don't know if I might start overpowering the space.

    Lastly the 8020s are a bit more more portable and would be great to be able to take on road trips in a pinch.

    I guess overall then I'm not sure if I'd really get more value out of the 8030s vs the 8020s, given a sub in the mix.
     
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  16. beemerphile

    beemerphile Friend

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    Here is the same type of passive volume control available in balanced. I use one in my workshop system and find it works well since my only input is the computer...

    https://emotiva.com/products/electronics/control-freak
     
  17. GoodEnoughGear

    GoodEnoughGear Friend

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    Yep, the Control Freak would work too. Just kind of wondering if digital in such small amounts would be discernible at all.
     
  18. landroni

    landroni Friend

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    Is this last bit of the conversation (after @Marvey reopened it) in any way relevant to this thread? Perhaps it should be moved elsewhere...
     
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  19. sphinxvc

    sphinxvc Gear Master East

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    Huh. Scratching my head, how do you hook up a stereo amp as a monoblock?

    Is this it?
    1. Use Y-splitters on both output channels of the preamp to both inputs of each amp
    2. Connect the 2 negative outputs to the negative binding post on your speaker, do the same for the positive outputs
     
  20. sphinxvc

    sphinxvc Gear Master East

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    Waiddasecond. I assume the amplifier has to be bridgeable for this to work, and in that case wiring might be clearly labeled?

    [question still stands, btw, curious to know if this is possible with regular non-bridgeable labeled amps]
     
    Last edited: Jan 5, 2017
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