Digital volume values?

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guf

Digital volume values?
« on: 15 Jun 2017, 04:10 pm »
With my 10 watt amp (First Watt) I listen mostly in the low 40s with my DHT pre. As my system gets more refined I'm able to turn it up more and some recordings to the low 50s. Now if this was a standard volume dial on the pre amp it seems like it would be in the 2-3 o'clock position which is almost maxed out. Does this mean I could benefit from a more powerful amp? I have 2 sets of speakers that are around 95db efficient.

Vinnie R.

GAIN and POWER are two different things...
« Reply #1 on: 15 Jun 2017, 07:14 pm »
Hi guf,

First - just for clarification purposes, LIO's volume control (no matter which linestage module you have) attenuates in the analog domain via analog relays that switch different analog attenuation settings (it is not a digital volume control that attenuates in the digital domain, reducing the effective bits of resolution).  Only the "control" of LIO's analog volume control is implemented digitally.  The volume knob is a "rotary encoder" that tells the system to change relay settings (thus changing the analog attenuation setting), and displays the volume setting as a number on the front panel display.  The remote volume up / volume down buttons do the same thing.

Ok - getting to your question:

The "position" of a volume control is not really a good indicator of amplifier power... it is more of an indicator of system gain.

Gain and Power are two different things.

For example.  Amplifier-A is rated at 5wpc.  Amplifier-B is rated at 500wpc.  Using the same Preamplifier-X in front of each amplifier, it is very possible that Amplifier A could sound louder at, say, 10 o'lock on the volume dial compared to Amplifier-B.  "But how is this so?  Isn't Amplifier-B 100x more powerful?"

Simple:  Amplifier-A has a higher voltage gain than Amplifier-B, meaning it's Output Voltage / Input Voltage ratio is higher. 
Output Voltage (to the speakers) = [Gain] x [Input Voltage (from the preamp)].

In my example above, Amplifier-A is louder than Amplifier-B at a given volume control setting on Preamplifier-X.  But this will only be the case until you reach a certain point (a certain amount of signal that you feed to the amplifier's input).  At some point, Amplifier-A will reach "clipping" (distortion) because once its output voltage is such that it is providing 5wpc of power to the speakers, that is all the power it can provide.  If you try to push a larger signal into it (turn the volume up more), you clip the output waveform to the speaker as you are forcing the amp to output a bigger signal (and thus, more power) than it can provide.  If you do this with Amplifier-B, it will continue to provide a larger and larger output signal to the speakers (more power, more SPL), until it reaches its 500wpc channel rating and clips (or if the speaker is not rated for this power level, a speaker driver could blow... meaning the voice coil of the speaker melts and it becomes an open circuit).

The FirstWatt SIT-2 amp has a published gain of 18dB (and power of 10wpc into 8 ohm).  This is fairly low gain.  Even with LIO DHT PRE's approx. 6 - 9dB of gain (depending on tube), you have a total gain of 24dB - 27dB.  If you have very sensitive speakers (yours at 95dB are probably considered high sensitivity, but not very high sensitivity), this 'might' be enough gain... otherwise, you will need turn to turn the volume up louder on the LIO Preamp to get sufficient output level.  This is fine, as long as you don't ask the SIT-2 to output more than 10wpc... otherwise it will clip (distort).

Now, if you run a preamp (or integrated amp) at nearly FULL volume, AND it is not distorting, AND it is still not loud enough... you simply need more gain in the system.  You can achieve this with:

- A source component (e.g. CD player, DAC, Phonostage) that has a higher output voltage. 
- A preamp with higher gain
- An amp with higher gain

Or if you have even more sensitive speakers (i.e., they play louder with a given input voltage), this is sort of like having more system gain.  :wink:

[Aside: Some people have the opposite problem.  Their preamp and/or amp has too much gain (and/or they have very sensitive speakers), so they have a "hair trigger" volume control, meaning even at low volume settings, the output is too loud and they do not get much usable range from their volume control.]

If you find that you can increase the LIO volume even more, AND your amplifier is not clipping, AND it plays loud enough for you (as loud as you need it to), then you are all set.  No issues there.  But if you reach clipping AND it is not loud enough for you, you need more amplifier power (OR even more sensitive speakers if you didn't want to change the amplifier, or you can even try sitting closer to your speakers as this will require less amplifier power to achieve the same SPL level).

Quote
Does this mean I could benefit from a more powerful amp? I have 2 sets of speakers that are around 95db efficient.

Based on what I mention below, you will hopefully see that you might need an amp with more gain (and potentially one with more output power as well).  If you don't understand this, then I probably didn't do a good enough job explaining things, so feel free to ask me questions and I will clarify.

LIO MOSFET AMP module has a gain of 26dB.  So if you try that, you will find that you will have the volume setting approx. 8 clicks lower on the LIO compared to the SIT-2 (which has a gain of 18dB) to get approx. the same volume from your speakers.  It might not be exactly 8 clicks lower, but probably pretty close to that as the LIO volume steps are approx. 1dB.  And LIO MOSFET AMP will also be able to play your speakers a little louder before reaching clipping since it has more output power.

It is also worth noting that if you have an amplifier that is 10wpc and one that is 20wpc, the 20wpc amplifier will NOT be able to play twice as loud.  You will only be able to obtain approx. 3dB more output level.

I hope this is helpful to you and others,

Vinnie
« Last Edit: 21 Jun 2017, 02:54 pm by Vinnie R. »

guf

Re: Digital volume values?
« Reply #2 on: 16 Jun 2017, 12:42 am »
Wow. Awesome informative read. I'll read it a few times before asking you to try and explain it again. :) Thank you so much for taking the time.

LARRY KYOTO

  • Jr. Member
  • Posts: 28
Re: Digital volume values?
« Reply #3 on: 21 Jun 2017, 06:20 am »
Possessing the rare ability to to be at the upper scientific/technical echelon of ones field while being able to clearly articulate/educate/excite the laymen like Carl Sagan & Bill Nye et al, is a true gift...to which I include VR.
どうもありがとう!

jriggy

Re: Digital volume values?
« Reply #4 on: 21 Jun 2017, 12:37 pm »
Totally agree! I have thought the same thing. Vinnie's thorough and understandable posts are always educational for me.

Vinnie R.

Re: Digital volume values?
« Reply #5 on: 21 Jun 2017, 02:50 pm »
Thanks, guys - glad that was helpful!

I just read it over again and found a few typos, so I edited it.  I need to learn to do a better job at
carefully proof reading.  :duh:

If you guys have questions about this, please let me know.  I think it is important to understand certain
concepts such as gain, power, etc.

Vinnie