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# Skeptico Saloon: An Objectivist Joint - Page 30

When an amp has a gain stated in decibels, how is that translated into the more typical gain specification from an engineering standpoint?

i.e. gain = output voltage of amplifier / input voltage of amplifier

Quote:
Originally Posted by miceblue

When an amp has a gain stated in decibels, how is that translated into the more typical gain specification from an engineering standpoint?

i.e. gain = output voltage of amplifier / input voltage of amplifier

I just divide decibels by 20 and then take 10 to the power of that result.

se
Quote:
Originally Posted by Steve Eddy

Quote:
Originally Posted by miceblue

When an amp has a gain stated in decibels, how is that translated into the more typical gain specification from an engineering standpoint?

i.e. gain = output voltage of amplifier / input voltage of amplifier

I just divide decibels by 20 and then take 10 to the power of that result.

se
Ah mmk. Thanks!

Oh wait, that makes sense.

dB = 20 * log_10(V_out / V_in)
Edited by miceblue - 12/2/13 at 7:12pm
Quote:
Originally Posted by miceblue

Ah mmk. Thanks!

Oh wait, that makes sense.

dB = 20 * log_10(V_out / V_in)

Yup.

se

Kind of curious where you guys believe the voltage requirements for a pair of headphones should be for suggesting amps.

Up to now, I've always been basing it off 110dB as a reasonable SPL cap and basing my voltage calcs based on that.

Thinking about it, though, I feel like it isn't a safe estimate for the total voltage headroom required for audiophiles, if only for the ReplayGain with no pre-amp wrinkle. If you've got dynamic classical pieces which get RG of very low or even positive values, pre-amping probably isn't the best idea.

The largest negative track gain in my library is -15.64dB. Let's call -16dB as a reasonable floor.

Doesn't that make it more logical to set the rule of thumb around 120-125dB or so to account for ReplayGain? It seems like where the actual "110dB Rule of Thumb" ends up after accounting for ReplayGain fighting with the loudness war.

Obviously, this isn't accounting for that you shouldn't be listening that loud anyway, but some people do like to listen loud, and I have to take that into consideration when giving amp recommendations to people.

Edited by SanjiWatsuki - 12/2/13 at 11:21pm
Quote:

Originally Posted by SanjiWatsuki

Doesn't that make it more logical to set the rule of thumb around 120-125dB or so to account for ReplayGain? It seems like where the actual "110dB Rule of Thumb" ends up after accounting for ReplayGain fighting with the loudness war.

This problem is at least partly solved by the amp having excess gain, or a gain switch that makes excess gain possible for unusually quiet input. In other words, attenuation by ReplayGain is more of a gain than a power issue.

I am not sure if listening to dynamically compressed music (which is what is attenuated the most by ReplayGain) at 110 dB SPL is a great idea, though. It is generally best not to exceed 85-90 dB average, and that is what gives 110 dB peaks with the most dynamic tracks. However, not all people have the same preferences, and for that reason, there is no single "one size that fits all" power requirement for any headphone. One person's "underpowered" amplifier can in fact be plenty enough for another.

Quote:
Originally Posted by stv014

This problem is at least partly solved by the amp having excess gain, or a gain switch that makes excess gain possible for unusually quiet input. In other words, attenuation by ReplayGain is more of a gain than a power issue.

I am not sure if listening to dynamically compressed music (which is what is attenuated the most by ReplayGain) at 110 dB SPL is a great idea, though. It is generally best not to exceed 85-90 dB average, and that is what gives 110 dB peaks with the most dynamic tracks. However, not all people have the same preferences, and for that reason, there is no single "one size that fits all" power requirement for any headphone. One person's "underpowered" amplifier can in fact be plenty enough for another.

Good point. I hadn't considered excess gain. I suppose with excess gain in mind, it works out.

In http://www.head-fi.org/t/668238/headphones-sensitivity-impedance-required-v-i-p-amplifier-gain, if you scroll to below the table you can see what compression does.

The heavily compressed metal track has an average perceived loudness of about 94 dB SPL which is only 6 dB lower than the peaks. The classical track has an average of about 80 dB, with 20 dB peaks.

Assuming the classical track meets your ReplayGain target (+/- 0 dB), the metal track needs to be attenuated by 14 dB to be equally loud on average (94-14=80 dB).

Since this uses a 110 dB SPL target without excess gain and volume set to -10 dB (about 2 pm) you could increase the volume to max to reach an average of 90 dB SPL with peaks reaching 96 / 110 dB SPL. Not bad considering no excess gain ... and 85 dB SPL being considered "safe" for 8h per day.

Edited by xnor - 12/3/13 at 8:24am
Sorry to butt in.
I've recently been using the Digiziod Zo bass enhancer with good results.
However I looked on their website at Technical info.
Smells like the worst kind of Hi Fi BS to me.
I would be very grateful if someone who knows what they are talking about would have a look at it for me. http://www.digizoid.com/index.php?p=tech
Edited by krismusic - 12/3/13 at 12:10pm
Quote:
Originally Posted by krismusic

Sorry to butt in.
I've recently been using the Digiziod Zo bass enhancer with good results.
However I looked on their website at Technical info.
Smells like the worst kind of Hi Fi BS to me.
I would be very grateful if someone who knows what they are talking about would have a look at it for me. http://www.digizoid.com/index.php?p=tech

I don't worry about all that stuff. If it sounds good to you, then who cares what they are claiming? It's all marketing BS.  I have a Digizoid and I don't always use it, but it is fun to use sometimes. I'm sure the audiophile crowd wouldn't approve

of the ZO, and that's fine...I still like it.

Quote:

I don't worry about all that stuff. If it sounds good to you, then who cares what they are claiming? It's all marketing BS.  I have a Digizoid and I don't always use it, but it is fun to use sometimes. I'm sure the audiophile crowd wouldn't approve
of the ZO, and that's fine...I still like it.
I totally agree but it seems a shame that they come out with that stuff and I would love to know how it really works.
I'm partly interested as I am trying to decide whether the device is a true improvement or a clever cheat. It could be said that it doesn't matter but I haven't come this far in a quest for SQ to be suckered! Thanks for the reply BTW.

Does it really have an expander or is it just an amp with bass boost? Anyway, yes, the stuff on their website is ...

Quote:
Originally Posted by xnor

Does it really have an expander or is it just an amp with bass boost? Anyway, yes, the stuff on their website is ...

I think it is cleverer than just a bass boost. Seems to incrementally increase the frequencies as they go lower or something like that.Does not mask the midrange and treble retains good separation.

Quote:
Originally Posted by krismusic

I think it is cleverer than just a bass boost. Seems to incrementally increase the frequencies as they go lower or something like that.Does not mask the midrange and treble retains good separation.

Yeah that's a normal bass boost with a low center frequency. The rising slope is of course going to counter-act the natural roll-off of your headphones and hearing.

I really doubt that they have an expander in there. Just boosting the sub-bass will make the waveform look "expanded" as shown on their tech page.

edit:

So their "5x" more bass claim is almost true (= +14 dB).

Edited by xnor - 12/3/13 at 4:16pm
Quote:
Originally Posted by xnor

Yeah that's a normal bass boost with a low center frequency. The rising slope is of course going to counter-act the natural roll-off of your headphones and hearing.

I really doubt that they have an expander in there. Just boosting the sub-bass will make the waveform look "expanded" as shown on their tech page.

edit:

So their "5x" more bass claim is almost true (= +14 dB).
Thanks xnor. So that is really all it is doing. The effect makes my ACS T15's much more enjoyable. They are bass light and thin sounding normally. I guess it comes down to whether you like accurate or enjoyable?!
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