XX volume control - something weird going on

[manisandher]

Perhaps my most controversial post ever...

There really is something weird going on, but it's not exclusive to XX - HQPlayer displays exactly the same behaviour. If the volume is attenuated anything below 0dB, the sound changes in the way I described in my first post - it appears to get clearer and more detailed. But I'm now convinced that 0dB (for both XX and HQP) gives the 'correct sound', and that with attenuation >0dB, the sound actually gets 'thinned out', and that other weird effects (such as a very slight 'echo' effect) come into play, giving the sound a 'lively' character. This seems to be counteracted to some extent by using the Custom filter, or indeed the Phisolator, but I think these are band aids to a certain extent.

But there does seem to be a 'fix' for those who refuse to go the preamp route (everyone here?):

Peak Extend OFF:
0dB - thick, full sound
-1.5dB (onwards) - much more sparkle and life, but maybe too thin for some material

Peak Extend ON:
0dB - thick, full sound
-1.5dB (onwards) - thick, full sound (exactly the same as 0dB, but slightly quieter, obviously)

In XX, using PE seems to keep the sound character exactly the same, irrespective of XX's attenuation level. What on earth is going on here, I have no idea.

[Interestingly, I've only started really noticing these effects since moving to single-ended tube amps and horns (in both my systems). Not sure if there's any connection. Perhaps for those with other system setups, this whole thing is simply a non-issue.]

Mani.

[PeterSt]

Mani,

I think with Peak Extension the volume is 3dBFS down internally to begin with. So set the slider at -0dBFS but in reality it is at -3dBFS. So the attenuation already took place. Now going down with -1.5dBFS is not changing from -0dBFS to -1.5dBFS but from -3dBFS to -4.5dBFS.

So I think what you see in the end, is expected.
The thing as a whole is still a mystery of course. But maybe something is happening like a kind of overshoot which crosses the voltage rails (we know that the margin is not all that large, right ?) and which won't happen with a small digital attenuation beforehand. If so, this should be happening at the higher frequencies and not with the lower we test with (1KHz). AND :

... I suppose I dreamt something about you telling that "it is since the SE tube amp and speaker" ...
(but I'd rather think you just removed that text)

It can just as well be caused by that amp etc. Same thing about the voltage rails, BUT you'd need to play at maximum "power". Read : your amp could be clipping.
Not sure !

Peter

[acg]

It can just as well be caused by that amp etc. Same thing about the voltage rails, BUT you'd need to play at maximum "power". Read : your amp could be clipping.
Not sure !

If I remember correctly, Mani was hoping for more output from the B'ass I/V so that he could drive his amplifiers louder.  This would indicate that the amp is not clipping with anything the G3 can throw at it (nominal 1.5vrms I think?).  Of course that is no guarantee that the amp in not clipping, but is an indication that it probably needs more than 1.5vrms to achieve full power, and therefore induce clipping, so 0dB attenuation in XXHE should be no different to -1.5dB.

[acg]

those who refuse to go the preamp route (everyone here?):

I am determined to find an active preamp that does justice to the G3 but that is proving difficult.  My most basic needs are instant muting and source selection...neither of which the G3 can do.  Analogue volume control that does not mess with the sound would also be nice...

[PeterSt]

XXHighEnd 2.08 can mute instantly ...

[acg]

XXHighEnd 2.08 can mute instantly ...

Nice!

[PeterSt]

It can just as well be caused by that amp etc. Same thing about the voltage rails, BUT you'd need to play at maximum "power". Read : your amp could be clipping.
Not sure !

If I remember correctly, Mani was hoping for more output from the B'ass I/V so that he could drive his amplifiers louder.  This would indicate that the amp is not clipping with anything the G3 can throw at it (nominal 1.5vrms I think?).  Of course that is no guarantee that the amp in not clipping, but is an indication that it probably needs more than 1.5vrms to achieve full power, and therefore induce clipping, so 0dB attenuation in XXHE should be no different to -1.5dB.

Hi Anthony,

Hmm ... that makes me think twice. But I think that only for some sense of "logic" you may be right. This does not mean that technically you need to be right per se. So I think the other way around :
With exactly the same thought (there's lack of power in general), you thus feed the amps with full voltage (whatever that is for the moment) and thus for that situation it requires the most power. So of course you can think that a DAC with e.g. 2x the output voltage should be able to work too for any situation (because "an amp is an amp" ?) but it doesn't really work like that. So I think the other way around : we have some amps that suffice for 109dB sensitive speakers (at say 3 Ohms) and that thus siffices the same for 115dB sensitive speakers (at 3 Ohms) ? I don't think so. And thus : if the amp suffices "just" for the 115dB speakers it lacks a factor of two for power on the 109dB speakers.

So all what's required to let the amps clip is :
a. have underpowered amps;
b. feed them with a voltage which is just more than they can handle.

Ad b.
Make that a little less (digital attanuation or by other attenuation means) and they are fine.

Right.
And now I say that all is moot because I said that I have dreamt that I saw a text from Mani telling about "since this tube amp and speakers" but I don't think I dreamt and Mani rather pulled that text (because ... and I didn't look it up - Mani had the problem prior to that already).

I already said "not sure !" and it is far more easy to think that the NOS1a clips. But then "unnoticed" for me and it should be related to a frequency because I coincidentally checked it for exactly this phenomenon (clipping) and it does not (but with 3dB more IIRC it does). It does not at 1KHz.

While this would be some technical explanation from my side, I only present you this information because it is an understandable explanation (I hope). But what I really think and should say is that each NOS1 has its sweet spot for attenuation which is related to the PCM1704 chips which has the sweetspot and which is not equal at al for each chip. But as you can understand in itself, this is not any explanation to bring forward because nobody can deal with it (I wouldn't be able to either). From there, another explanation is more feasible and this is that the MSB (Most Significant Bit) from the chips (or one of them etc.) implies a "not the best" sound. So remember, when we attenuate digitally even the slightest, that bit is turned off and never comes up throughout and piece of music (no matter how loud). Or an even better explanation for those understanding the PCM1704 : that one half of the chip (forming the 24th bit (MSB)) is shut off and which is special (regarding to all of the other bits).

... And of course it is already known that about each person trying to digitally attenuate with a preamp (or analoge volume of other means) present, always comes up with this 6dB. I never tried it, but this may not be a coincidence.
So in the end it is nothing new ?

blablabla ...
Peter

[manisandher]

A very quick post for now, with a few points...

1. I don't think it has anything to do with the amp - the effect is the same in both my systems (totally different amps)

2. I noticed this quite a while ago, when I still had the Orelo speakers (though I may not have posted immediately)

3. The 'character' of the sound at -3dB with PE is very different to that at -6dB without PE - levels identical, so this has nothing to do with the 1704 'sweetspot'

4. The 'character' of the sound at 0dB without PE is similar to that with PE at any attenuation level

More later (gym first!).

Mani.

[acg]

Mani, are you talking about this happening in two different systems with two different NOS1 G3, both systems tubes/horns, regardless of HQPlayer or XXHE doing the digital attenuation?  If so, then I assume that each system has different tube amps which leaves the G3 as the common denominator.

Perhaps what Peter says above regarding the PCM1704K chips is relevant, but you have two G3's and it is probably unlikely that they would display the same behaviour if it was a quirk between different individual 1704's.

A lot of tube amps need 6VRMS or more before clipping, it just depends on the first stage tube and to a lesser degree the circuit, but the winding of the output transformers and the speaker load, as Peter says, can also induce clipping in the amplifier.  That both of your systems display the same trait still leads me to think there is something about the B'ass driving those amps, but even that is unlikely in my view.

Do you have a spec for the input sensitivity of the amplifiers?  What about impedance plots of the speaker load that they are driving?  Probably not to the latter, but it can be measured, and you may even have the gear there to do it.

LATER:  Reading your post above Mani, where you mention the Orelo's, perhaps it is something that others with that "known" system can try to emulate?  Surely you must have some other way of attenuating full power with 20w/30w amps and 118dB/m/v sensitive horns?  How do you even test that?

[acg]

It can just as well be caused by that amp etc. Same thing about the voltage rails, BUT you'd need to play at maximum "power". Read : your amp could be clipping.
Not sure !

If I remember correctly, Mani was hoping for more output from the B'ass I/V so that he could drive his amplifiers louder.  This would indicate that the amp is not clipping with anything the G3 can throw at it (nominal 1.5vrms I think?).  Of course that is no guarantee that the amp in not clipping, but is an indication that it probably needs more than 1.5vrms to achieve full power, and therefore induce clipping, so 0dB attenuation in XXHE should be no different to -1.5dB.

Hi Anthony,

Hmm ... that makes me think twice. But I think that only for some sense of "logic" you may be right. This does not mean that technically you need to be right per se. So I think the other way around :
With exactly the same thought (there's lack of power in general), you thus feed the amps with full voltage (whatever that is for the moment) and thus for that situation it requires the most power. So of course you can think that a DAC with e.g. 2x the output voltage should be able to work too for any situation (because "an amp is an amp" ?) but it doesn't really work like that. So I think the other way around : we have some amps that suffice for 109dB sensitive speakers (at say 3 Ohms) and that thus siffices the same for 115dB sensitive speakers (at 3 Ohms) ? I don't think so. And thus : if the amp suffices "just" for the 115dB speakers it lacks a factor of two for power on the 109dB speakers.

So all what's required to let the amps clip is :
a. have underpowered amps;
b. feed them with a voltage which is just more than they can handle.

Ad b.
Make that a little less (digital attanuation or by other attenuation means) and they are fine.

Right.
And now I say that all is moot because I said that I have dreamt that I saw a text from Mani telling about "since this tube amp and speakers" but I don't think I dreamt and Mani rather pulled that text (because ... and I didn't look it up - Mani had the problem prior to that already).

I already said "not sure !" and it is far more easy to think that the NOS1a clips. But then "unnoticed" for me and it should be related to a frequency because I coincidentally checked it for exactly this phenomenon (clipping) and it does not (but with 3dB more IIRC it does). It does not at 1KHz.

While this would be some technical explanation from my side, I only present you this information because it is an understandable explanation (I hope). But what I really think and should say is that each NOS1 has its sweet spot for attenuation which is related to the PCM1704 chips which has the sweetspot and which is not equal at al for each chip. But as you can understand in itself, this is not any explanation to bring forward because nobody can deal with it (I wouldn't be able to either). From there, another explanation is more feasible and this is that the MSB (Most Significant Bit) from the chips (or one of them etc.) implies a "not the best" sound. So remember, when we attenuate digitally even the slightest, that bit is turned off and never comes up throughout and piece of music (no matter how loud). Or an even better explanation for those understanding the PCM1704 : that one half of the chip (forming the 24th bit (MSB)) is shut off and which is special (regarding to all of the other bits).

... And of course it is already known that about each person trying to digitally attenuate with a preamp (or analoge volume of other means) present, always comes up with this 6dB. I never tried it, but this may not be a coincidence.
So in the end it is nothing new ?

blablabla ...
Peter

Thanks for this post Peter, it is most informative, especially the bit I have made bold.  In the past I have noticed that no attenuation does not sound as good as just a little bit, but I always put it down to the untreated room I was in and thought that the "problem" was a result of  non-optimal acoustics as more sound power was added to the room.

I have not bothered to find the attenuation sweet spot with the preamps I have here but maybe I should one day.  Have been waiting to properly treat the room first before I bothered with such relatively minor tweaking, but I also have other more pressing audio projects on the go...

[PeterSt]

If so, then I assume that each system has different tube amps which leaves the G3 as the common denominator.
[...]
That both of your systems display the same trait still leads me to think there is something about the B'ass driving those amps, but even that is unlikely in my view.

Anthony, by now I think you saw it yourself (reading Mani's post later than you wrote yours) but this was already happening prior to the G3/B'ASS upgrade.

I also dare say that Mani has "visions" (don't want to call it issues) on this from what ? ... 6 years back ? or was it 8 years because even prior to the NOS1 ? I think so ...

Peter

[acg]

If so, then I assume that each system has different tube amps which leaves the G3 as the common denominator.
[...]
That both of your systems display the same trait still leads me to think there is something about the B'ass driving those amps, but even that is unlikely in my view.

Anthony, by now I think you saw it yourself (reading Mani's post later than you wrote yours) but this was already happening prior to the G3/B'ASS upgrade.

I also dare say that Mani has "visions" (don't want to call it issues) on this from what ? ... 6 years back ? or was it 8 years because even prior to the NOS1 ? I think so ...

Peter

Yes, I have read that now.  I am not sure how Mani tested it with the Orelos though...it must have been far to loud to listen with no attenuation.

[manisandher]

I also dare say that Mani has "visions" (don't want to call it issues) on this from what ? ... 6 years back ? or was it 8 years because even prior to the NOS1 ? I think so ...

Oh yeah, I've been playing around with active, passive and digital attenuation for quite a while now. For a long time, I refused to use digital attenuation because it just sounded wrong to me, and used instead an Audio Synthesis balanced discrete resistor passive or a Pass Labs X1 active. I switched to using digital attenuation when I received the Orelos.

I am not sure how Mani tested it with the Orelos though...it must have been far to loud to listen with no attenuation.

With the Orelos, I just compared -21dB_no_PE with -18dB_with_PE - the difference in sound was obvious. I assumed that PE was messing the sound up in some way, but I now wonder if attenuation without PE is the issue...

Mani.

[manisandher]

And of course it is already known that about each person trying to digitally attenuate with a preamp (or analoge volume of other means) present, always comes up with this 6dB.

Yes but -6dB without PE still sounds different to -3dB with PE. You may feel that this is obvious - I mean, PE should be doing something to the sound, right? But I'm interested in why PE at any level sounds similar in 'character' to 0dB.

Any attenuation level without PE now sounds wrong to my ears. There's an edge to the sound. A 'hollowness'. The full-bodiedness of instruments and voices is gone. But if I switch to a Custom filter or put the Phisolator in the chain, PE simply sounds too dull.

Mani.

[PeterSt]

OK Mani, so I must start listening to everything just with PE engaged, right ?
So I will !

Peter

PS: As you may recall I myself am quite confident that something *is* going on, just per your reports about this all so often, combined with the fact that what all happens is complicated so prone to error. But then you may also recall that I can't find any bugs in the code and I looked so often (in the past) ...