DC-1

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Damn, spoke too soon!

Yesterday, I did not test all 3 pairs of speakers connected to the selector. Just selected the garage speakers and the noise is present there, but not on the other 2 pair.

Back to troubleshooting...

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Garbulky, not yet, but I will try that now.

Edit: still have the noise in the garage speakers after unplugging the DC-1, waiting, and replugging.

[garbulky]

Mar 17, 2014 7:01:21 GMT -5 ads said:

Garbulky, not yet, but I will try that now.

Edit: still have the noise in the garage speakers after unplugging the DC-1, waiting, and replugging.

Gotcha. Hmm.....you wouldn't happen to have a power conditioner connected to this circuit by any chance?

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I do use a Panamax, but I don't think that's the problem.

The issue seems to be a combination of the speaker wire run to the selector and the selector itself.

When I use the temporary wiring twisted directly to the garage speaker wires - no noise.

When I use the original wiring twisted directly to the garage speaker wires - noise.

When I use the temporary wiring with the selector box and select garage speakers - noise.

On vacation today, so plan to run up to Parts Express to buy some speaker wire, banana plugs, and a wall plate.  I'll rig this up for manual speaker switching (no selector box), since I never use more than 1 pair of speakers at a time.

I know these noise troubleshooting posts are not really relevant to this thread, but since I originally experienced the noise with the direct connection of the DC-1 to my amps, I want to bring this to resolution in this thread.  Hopefully, the new wiring and no-selector approach will do this.

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Well, the original run of speaker wire to the selector box and selector box itself were not the cause of the noise. New run of wire and direct connection to remote speakers (using binding post wall plate to couple individual pairs of remote speakers, no selector box) still produces noise in the remote speakers.

If I replace the long run of wire with a short one for the R channel amp, connecting a speaker in the main HT room - no noise. If I have the R or L channel amp off - no noise. If I unplug the interconnect to L or R amp - no noise (I tried several interconnects to eliminate an interconnect issue).

So, somehow, I have an issue with noise only with the long, remote speaker wires, but only with with current monobridged amps for the L and R channels. When I connected the long, remote speaker wires to an alternate stereo amp - no noise.

So, ultimately, I have not been able to fix the issue, and still don't know the root cause, but can say that the DC-1 is not the culprit, as the noise is present when the DC-1 is disconnected from power and interconnects.

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I've been thinking more about the DC-1 variable output with no preamp vs. fixed with a preamp.

How does the DC-1's gain and volume circuitry compare from a quality/topology standpoint to the circuitry in a preamp like the XSP-1?

If the DC-1's gain and volume circuitry are similar to what's in a good separate preamp, I can see how running the DC-1 directly to an amplifier "should" sound as good or even better than using a separate preamp.

If one uses the the DC-1 with a volume of less than 0 dB connected to an amp (so far, the loudest I've used is around -8 dB) and compares that to fixed level with a preamp, shouldn't any differences in sound be attributable to the separate preamp adding coloration or distortion to the DC-1's signal?

Ultimately, if one did not need any of the features of a separate preamp vs. using the DC-1 directly, are there any sonic advantages to using a separate preamp?

I would like to hear from Emotiva/Keith on this, specifically on DC-1 direct vs. a DC-1/XSP-1 combo.

[garbulky]

Mar 19, 2014 9:08:11 GMT -5 ads said:

I've been thinking more about the DC-1 variable output with no preamp vs. fixed with a preamp.

How does the DC-1's gain and volume circuitry compare from a quality/topology standpoint to the circuitry in a preamp like the XSP-1?

If the DC-1's gain and volume circuitry are similar to what's in a good separate preamp, I can see how running the DC-1 directly to an amplifier "should" sound as good or even better than using a separate preamp.

If one uses the the DC-1 with a volume of less than 0 dB connected to an amp (so far, the loudest I've used is around -8 dB) and compares that to fixed level with a preamp, shouldn't any differences in sound be attributable to the separate preamp adding coloration or distortion to the DC-1's signal?

Ultimately, if one did not need any of the features of a separate preamp vs. using the DC-1 directly, are there any sonic advantages to using a separate preamp?

I would like to hear from Emotiva/Keith on this, specifically on DC-1 direct vs. a DC-1/XSP-1 combo.

Well it could be adding coloration. Or....the pre-amp you would use it with may have more "robust" circuitry in terms of driving the amps. I auditioned the XDA-1 connected to a USP-1. And the USP-1 produced dynamics that the XDA-1 COULD NOT MANAGE when connected direct to the power amp. Those dynamics were so good ..... even the DC-1 couldn't manage that fast swing from soft to loud with that level of presence when connected direct to the power amp. However the USP-1 was not as clear as either the XDA-1 or the DC-1 connected directly to the amplifier. But it was able to provide those dynamics. I don't know the technical explanation of what I heard. But the difference was reasonably obvious.
I haven't heard the XSP-1 in my system so I can't comment on it.

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Gar, I totally understand what you're getting at, and I'm trying to understand "why?".

The thing I'm struggling with is how a preamp could "add" dynamics to a signal when it is attenuating a source signal. But the more I think about it, I don't think that's what an active preamp does. I could be wrong, but let's assume an active preamp applies its full gain stage to an input, then uses its volume control to attenuate.

Assuming all dynamics in music come from high to low voltage swing, how could a preamp create voltage swing that is greater than what was in the original signal at an output of unity gain or less?

Not being an EE or designer, I can certainly admit that I could be missing something obvious.

[garbulky]

Mar 19, 2014 10:44:02 GMT -5 ads said:

Gar, I totally understand what you're getting at, and I'm trying to understand "why?".

The thing I'm struggling with is how a preamp could "add" dynamics to a signal when it is attenuating a source signal. But the more I think about it, I don't think that's what an active preamp does. I could be wrong, but let's assume an active preamp applies its full gain stage to an input, then uses its volume control to attenuate.

Assuming all dynamics in music come from high to low voltage swing, how could a preamp create voltage swing that is greater than what was in the original signal at an output of unity gain or less?

Not being an EE or designer, I can certainly admit that I'm missing something obvious

I actually thought exactly the same as you until I heard it for myself. BTW, I didn't spend a single penny on the DC-1 or the USP-1, so it wasn't buyers bias. They were from a friend that was kind enough to lend it to me.

I don't know the answer to your question either!
FWIW, I don't think a pre-amp is creating a greater voltage swing than what was in the original signal. Just that the original signal and
the interaction with whatever circuitry downstream is causing the difference and (maybe) hampering the dynamics that should have been there.
I know that pre-amps change the impedance of the signal. So that may be a clue....
But I don't actually have any useful info to provide to you on that subject other than what I've heard.

[northshore]

First post, thanks to Keith and the Emo crew for prompt handling of my DC-1 issue. The replacement unit is coming together very nicely now at about 50 hours.

Everything matters and each additional component can make a positive or negative contribution. Fewer components in the chain is a valid philosophy, and the DC-1 is well suited to go directly to many amps as it not only includes a variable preamp but also balanced and unbalanced outputs.

In my case, the challenge now is to limit components in a bi-amped speaker system.

A 2nd order high pass PLLXO through the rca’s is a good solution for the top end. For the bottom end, a LR 4th order low pass is preferable which doesn’t look possible with a PLLXO. To bad, those DC-1 balanced outputs are an attractive route for a low inline crossover.

The low pass can be done with a mini-dsp, but at the cost of adding another (and poorer quality) AD DA conversion not to mention the two separate clocks.
Many of the newer pro amps with DSP have the same problem.

Adding a pro style eq/crossover in the chain before a straight amp adds another component using either opamps or dsp.

I may be better off just going with plate amps, in the meantime the DC-1 is showing its stuff in my headphone rig.

[hapiper]

Is anybody using the DC-1 as a headphone listening station and if so how is that working? I do have a headphone amp but would like to be able to plug in my phones directly occasionally to avoid carting stuff all over my bedroom.

[GreenKiwi]

I really enjoy it with my HD650s and T70s, but not with IEMs, too much noise for high sensitivity IEM. My ODAC/O2 is far better for them.

[garbulky]

Mar 19, 2014 21:46:28 GMT -5 hapiper said:

Is anybody using the DC-1 as a headphone listening station and if so how is that working? I do have a headphone amp but would like to be able to plug in my phones directly occasionally to avoid carting stuff all over my bedroom.

I've used the DC-1 with sennheiser HD600. The sound is very close to that of my standalone Xenos 3HA headphone amp during listening. At times it's a little clearer. It works well for that type of headphone!

[hapiper]

That is what I was wanting to hear as that is what I have, some HD600 and Hd650.

[KeithL]

I'm not going to "take a side here" - and I don't at all doubt that Garbulky is hearing some audible difference - but no preamp or similar device is designed to "affect dynamics".
In an ideal world, a preamp would not affect dynamics - for better OR worse; it should pass every signal as "a straight wire with gain" - and that gain should be the same for every signal (until you move the knob).
Audiophiles have a habit of discussing "things" which are really more properly "constructs" (ideas).
Dynamic range (and "signal dynamics") are IDEAS; you can measure two signal levels, and calculate the difference between them, and even calculate how fast you can go from one to the other, but there's nothing else there.
There is no magical relationship between those two signals that is somehow OUTSIDE the information from them separately.

"Dynamic range" is simply the difference in level between two signals (typically the loudest and quietest signals a given piece of equipment can deliver).
You can make the distance between them further apart by reducing the quiet signal, or by boosting the loud signal, or you can switch between the two levels more quickly, but you cannot keep both signals the same, yet somehow change some third property called "dynamics".
A preamp could overload, or have poor gain, or be unable to drive a given load, in which case it could "compromise the dynamics" by not allowing the loud signal to be as much louder than the quiet signal as it should be.
(And, yes, this could happen if the one device was unable to sufficiently drive the input impedance of whatever it is connected to.)

It also happens to be an engineering fact that flawed circuits often compress dynamics (if their gain changes with signal level) but rarely accidentally increase dynamic differences.
(It can easily be done deliberately, and could happen accidentally, but isn't common with the sort of circuitry you're likely to find in a preamp.)

Without a ridiculous amount of measurements (which might not tell us anything anyway), I can offer several possible reasons for the difference Garbulky hears:

1) It could be that the USP-1 is more able to drive his particular load than the DC-1 (I doubt this one because the DC-1 shouldn't have trouble with most normal loads)
2) The extra gain provided by the USP-1 could be providing a signal that gets better performance out of the amplifier or the DAC (by adding gain, all the volume controls end up in different places, which could be resulting in lower noise or distortion somewhere)
3) It could be that the USP-1 is actually producing some small amount of distortion or frequency response variation that sounds nice (in his particular system)

Unfortunately "dynamics" is a standard "catch-all" - we humans tend to perceive many sorts of differences as "dynamics", which makes it very difficult to figure out which of those differences is implicated in a particular situation.
However, I would be willing to wager that what's changing isn't really the dynamic relationship between levels, but rather something else that is being perceived as a change in dynamics.
(But, until and unless we ever know precisely what is going on, a descriptive term is a lot better than no information at all. )

The one thing I would warn, though, is that his experience could be very specific to his room, his equipment, and his configuration..... and so may not carry over to someone else.

Mar 19, 2014 11:33:19 GMT -5 garbulky said:

Mar 19, 2014 10:44:02 GMT -5 ads said:

Gar, I totally understand what you're getting at, and I'm trying to understand "why?".

The thing I'm struggling with is how a preamp could "add" dynamics to a signal when it is attenuating a source signal. But the more I think about it, I don't think that's what an active preamp does. I could be wrong, but let's assume an active preamp applies its full gain stage to an input, then uses its volume control to attenuate.

Assuming all dynamics in music come from high to low voltage swing, how could a preamp create voltage swing that is greater than what was in the original signal at an output of unity gain or less?

Not being an EE or designer, I can certainly admit that I'm missing something obvious

I actually thought exactly the same as you until I heard it for myself. BTW, I didn't spend a single penny on the DC-1 or the USP-1, so it wasn't buyers bias. They were from a friend that was kind enough to lend it to me.

I don't know the answer to your question either!
FWIW, I don't think a pre-amp is creating a greater voltage swing than what was in the original signal. Just that the original signal and
the interaction with whatever circuitry downstream is causing the difference and (maybe) hampering the dynamics that should have been there.
I know that pre-amps change the impedance of the signal. So that may be a clue....
But I don't actually have any useful info to provide to you on that subject other than what I've heard.

[garbulky]

Mar 20, 2014 14:14:53 GMT -5 KeithL said:

I'm not going to "take a side here" - and I don't at all doubt that Garbulky is hearing some audible difference - but no preamp or similar device is designed to "affect dynamics".
In an ideal world, a preamp would not affect dynamics - for better OR worse; it should pass every signal as "a straight wire with gain" - and that gain should be the same for every signal (until you move the knob).
Audiophiles have a habit of discussing "things" which are really more properly "constructs" (ideas).
Dynamic range (and "signal dynamics") are IDEAS; you can measure two signal levels, and calculate the difference between them, and even calculate how fast you can go from one to the other, but there's nothing else there.
There is no magical relationship between those two signals that is somehow OUTSIDE the information from them separately.

"Dynamic range" is simply the difference in level between two signals (typically the loudest and quietest signals a given piece of equipment can deliver).
You can make the distance between them further apart by reducing the quiet signal, or by boosting the loud signal, or you can switch between the two levels more quickly, but you cannot keep both signals the same, yet somehow change some third property called "dynamics".
A preamp could overload, or have poor gain, or be unable to drive a given load, in which case it could "compromise the dynamics" by not allowing the loud signal to be as much louder than the quiet signal as it should be.
(And, yes, this could happen if the one device was unable to sufficiently drive the input impedance of whatever it is connected to.)

It also happens to be an engineering fact that flawed circuits often compress dynamics (if their gain changes with signal level) but rarely accidentally increase dynamic differences.
(It can easily be done deliberately, and could happen accidentally, but isn't common with the sort of circuitry you're likely to find in a preamp.)

Without a ridiculous amount of measurements (which might not tell us anything anyway), I can offer several possible reasons for the difference Garbulky hears:

1) It could be that the USP-1 is more able to drive his particular load than the DC-1 (I doubt this one because the DC-1 shouldn't have trouble with most normal loads)
2) The extra gain provided by the USP-1 could be providing a signal that gets better performance out of the amplifier or the DAC (by adding gain, all the volume controls end up in different places, which could be resulting in lower noise or distortion somewhere)
3) It could be that the USP-1 is actually producing some small amount of distortion or frequency response variation that sounds nice (in his particular system)

Unfortunately "dynamics" is a standard "catch-all" - we humans tend to perceive many sorts of differences as "dynamics", which makes it very difficult to figure out which of those differences is implicated in a particular situation.
However, I would be willing to wager that what's changing isn't really the dynamic relationship between levels, but rather something else that is being perceived as a change in dynamics.
(But, until and unless we ever know precisely what is going on, a descriptive term is a lot better than no information at all. )

The one thing I would warn, though, is that his experience could be very specific to his room, his equipment, and his configuration..... and so may not carry over to someone else.

Mar 19, 2014 11:33:19 GMT -5 garbulky said:

I actually thought exactly the same as you until I heard it for myself. BTW, I didn't spend a single penny on the DC-1 or the USP-1, so it wasn't buyers bias. They were from a friend that was kind enough to lend it to me.

I don't know the answer to your question either!
FWIW, I don't think a pre-amp is creating a greater voltage swing than what was in the original signal. Just that the original signal and
the interaction with whatever circuitry downstream is causing the difference and (maybe) hampering the dynamics that should have been there.
I know that pre-amps change the impedance of the signal. So that may be a clue....
But I don't actually have any useful info to provide to you on that subject other than what I've heard.

I don't think a pre-amp could create a greater voltage swing than what was in the original signal either. I.e. increase dynamics over what's actually there. That should be impossible imo.
Nevertheless, the USP-1 has significantly better dynamics driving an XPA-2. It is there too - just slightly less with a UPA-2. Just not as good clarity compared to DAC direct though.

[garbulky]

Mar 20, 2014 14:20:00 GMT -5 garbulky said:

Mar 20, 2014 14:14:53 GMT -5 KeithL said:

I'm not going to "take a side here" - and I don't at all doubt that Garbulky is hearing some audible difference - but no preamp or similar device is designed to "affect dynamics".
In an ideal world, a preamp would not affect dynamics - for better OR worse; it should pass every signal as "a straight wire with gain" - and that gain should be the same for every signal (until you move the knob).
Audiophiles have a habit of discussing "things" which are really more properly "constructs" (ideas).
Dynamic range (and "signal dynamics") are IDEAS; you can measure two signal levels, and calculate the difference between them, and even calculate how fast you can go from one to the other, but there's nothing else there.
There is no magical relationship between those two signals that is somehow OUTSIDE the information from them separately.

"Dynamic range" is simply the difference in level between two signals (typically the loudest and quietest signals a given piece of equipment can deliver).
You can make the distance between them further apart by reducing the quiet signal, or by boosting the loud signal, or you can switch between the two levels more quickly, but you cannot keep both signals the same, yet somehow change some third property called "dynamics".
A preamp could overload, or have poor gain, or be unable to drive a given load, in which case it could "compromise the dynamics" by not allowing the loud signal to be as much louder than the quiet signal as it should be.
(And, yes, this could happen if the one device was unable to sufficiently drive the input impedance of whatever it is connected to.)

It also happens to be an engineering fact that flawed circuits often compress dynamics (if their gain changes with signal level) but rarely accidentally increase dynamic differences.
(It can easily be done deliberately, and could happen accidentally, but isn't common with the sort of circuitry you're likely to find in a preamp.)

Without a ridiculous amount of measurements (which might not tell us anything anyway), I can offer several possible reasons for the difference Garbulky hears:

1) It could be that the USP-1 is more able to drive his particular load than the DC-1 (I doubt this one because the DC-1 shouldn't have trouble with most normal loads)
2) The extra gain provided by the USP-1 could be providing a signal that gets better performance out of the amplifier or the DAC (by adding gain, all the volume controls end up in different places, which could be resulting in lower noise or distortion somewhere)
3) It could be that the USP-1 is actually producing some small amount of distortion or frequency response variation that sounds nice (in his particular system)

Unfortunately "dynamics" is a standard "catch-all" - we humans tend to perceive many sorts of differences as "dynamics", which makes it very difficult to figure out which of those differences is implicated in a particular situation.
However, I would be willing to wager that what's changing isn't really the dynamic relationship between levels, but rather something else that is being perceived as a change in dynamics.
(But, until and unless we ever know precisely what is going on, a descriptive term is a lot better than no information at all. )

The one thing I would warn, though, is that his experience could be very specific to his room, his equipment, and his configuration..... and so may not carry over to someone else.

I don't think a pre-amp could create a greater voltage swing than what was in the original signal either. I.e. increase dynamics over what's actually there. That should be impossible imo.
Nevertheless, the USP-1 has significantly better dynamics driving an XPA-2. It is there too - just slightly less with a UPA-2. Just not as good clarity compared to DAC direct though.

But don't take my word for it. Just use a DC-1 and compare it (not with an XSP-1) but with a USP-1 driving XPA-1's/2's on that sweet B&W setup. I would be interested to get your take on it.

[KeithL]

You may actually have "answered your own question" on this one......

As you perceived it, the USP-1 was "had better dynamics", but was "less clear"..... now, what if those two differences were really one difference?

We humans to a certain degree perceive distortion as loudness (which is how a 0.1 watt table radio can sound painfully loud).

Now, let's assume that I have some signal with two "notes", and the second note is ten times as loud (by measured power) as the first one.
Lets further assume that I am going to play my two notes on several different amplifiers - all set so that the quiet note is at 1 watt and the loud note is at 10 watts.
If I play those notes through a perfect (zero distortion) amplifier, the 1 to 10 relationship will remain as expected.

But what If I play them through my nice new SET triode amplifier (which has 1% THD at 1 watt and 10% THD at 10 watts)?
Now the quiet note is playing at 1 watt - AT 1% THD, and the loud note is playing at 10 watts - AT 10% THD.
Even though the wattage remains the same for each, the 1 watt note will sound slightly louder because of the 1% THD; and the 10 watt note will sound "more louder" because of its 10% THD.
The result will be that the difference in loudness between the two notes will be exaggerated....
In other words, the dynamics will seem to have increased - so the amp will sound "less clean but more dynamic".
You will, in effect, have the psychoacoustic equivalent of a dynamic range expander......
In this case, because the distortion is so extreme, the "audible effect" will also be very obvious.
But similar things, although far more subtle, can occur with even small differences in distortion or frequency response - and almost certainly account for most "differences in sound" between preamps or power amps.

Even though the DC-1 and the USP-1 are both very low in distortion, the DC-1 is probably lower.....
Beyond that, the actual spectra of the distortion for the two will be different.
And, even though both are very flat, they will also differ slightly in frequency response.
(We're talking about the acoustic equivalent of how a slightly foggy windshield will make streetlights look slightly blurred - but often also make them look brighter.)

Mar 19, 2014 9:34:06 GMT -5 garbulky said:

Mar 19, 2014 9:08:11 GMT -5 ads said:

I've been thinking more about the DC-1 variable output with no preamp vs. fixed with a preamp.

How does the DC-1's gain and volume circuitry compare from a quality/topology standpoint to the circuitry in a preamp like the XSP-1?

If the DC-1's gain and volume circuitry are similar to what's in a good separate preamp, I can see how running the DC-1 directly to an amplifier "should" sound as good or even better than using a separate preamp.

If one uses the the DC-1 with a volume of less than 0 dB connected to an amp (so far, the loudest I've used is around -8 dB) and compares that to fixed level with a preamp, shouldn't any differences in sound be attributable to the separate preamp adding coloration or distortion to the DC-1's signal?

Ultimately, if one did not need any of the features of a separate preamp vs. using the DC-1 directly, are there any sonic advantages to using a separate preamp?

I would like to hear from Emotiva/Keith on this, specifically on DC-1 direct vs. a DC-1/XSP-1 combo.

Well it could be adding coloration. Or....the pre-amp you would use it with may have more "robust" circuitry in terms of driving the amps. I auditioned the XDA-1 connected to a USP-1. And the USP-1 produced dynamics that the XDA-1 COULD NOT MANAGE when connected direct to the power amp. Those dynamics were so good ..... even the DC-1 couldn't manage that fast swing from soft to loud with that level of presence when connected direct to the power amp. However the USP-1 was not as clear as either the XDA-1 or the DC-1 connected directly to the amplifier. But it was able to provide those dynamics. I don't know the technical explanation of what I heard. But the difference was reasonably obvious.
I haven't heard the XSP-1 in my system so I can't comment on it.

[sahmen]

Mar 20, 2014 15:57:29 GMT -5 KeithL said:

You may actually have "answered your own question" on this one......

As you perceived it, the USP-1 was "had better dynamics", but was "less clear"..... now, what if those two differences were really one difference?


Even though the DC-1 and the USP-1 are both very low in distortion, the DC-1 is probably lower.....
Beyond that, the actual spectra of the distortion for the two will be different.
And, even though both are very flat, they will also differ slightly in frequency response.
(We're talking about the acoustic equivalent of how a slightly foggy windshield will make streetlights look slightly blurred - but often also make them look brighter.)

Mar 19, 2014 9:34:06 GMT -5 garbulky said:

Keith: Here's a related but slightly different question.  I know you consider the explanation you just gave to be hypothetical, but assuming it is entirely accurate, and one could say for sure that the "dynamics" that Garbulky associates with the USP-1 is are actually the result of a slightly higher distortion rate over that of the DC-1, what would be the probable result (or advantage) of replacing the USP-1 with the XSP-1 in the same chain of components, with everything else being equal...?  I am asking because I have both the USP-1 and Pre-1, and have been thinking of upgrading one of them to the XSP-1, because of all the great things I have heard about the XSP-1.  The problem is that without actually purchasing the XSP-1, I have no inkling of what kind of differences to expect by upgrading,  The upgrade would be, in that sense, a "jump in the dark.", which is why I think I would benefit from getting a more expert opinion.. I do enjoy the sound I'm currently hearing from my DC-1-->Pre-1 chain, and really have no complaints about that,  but if there is room for a significant "improvement"  via the XSP-1, I would definitely like to explore it.  I am familiar with all the caveats and disclaimers one often hears in this lounge  regarding the "subjectiveness" of musical tastes, and the peculiarities and uniqueness of each component/room configuration etc. etc., and I am not disregarding them.  I would still want your opinion about my question, nonetheless.  Thanks in advance.

[garbulky]

Mar 20, 2014 15:57:29 GMT -5 KeithL said:

You may actually have "answered your own question" on this one......

As you perceived it, the USP-1 was "had better dynamics", but was "less clear"..... now, what if those two differences were really one difference?

We humans to a certain degree perceive distortion as loudness (which is how a 0.1 watt table radio can sound painfully loud).

Now, let's assume that I have some signal with two "notes", and the second note is ten times as loud (by measured power) as the first one.
Lets further assume that I am going to play my two notes on several different amplifiers - all set so that the quiet note is at 1 watt and the loud note is at 10 watts.
If I play those notes through a perfect (zero distortion) amplifier, the 1 to 10 relationship will remain as expected.

But what If I play them through my nice new SET triode amplifier (which has 1% THD at 1 watt and 10% THD at 10 watts)?
Now the quiet note is playing at 1 watt - AT 1% THD, and the loud note is playing at 10 watts - AT 10% THD.
Even though the wattage remains the same for each, the 1 watt note will sound slightly louder because of the 1% THD; and the 10 watt note will sound "more louder" because of its 10% THD.
The result will be that the difference in loudness between the two notes will be exaggerated....
In other words, the dynamics will seem to have increased - so the amp will sound "less clean but more dynamic".
You will, in effect, have the psychoacoustic equivalent of a dynamic range expander......
In this case, because the distortion is so extreme, the "audible effect" will also be very obvious.
But similar things, although far more subtle, can occur with even small differences in distortion or frequency response - and almost certainly account for most "differences in sound" between preamps or power amps.

Even though the DC-1 and the USP-1 are both very low in distortion, the DC-1 is probably lower.....
Beyond that, the actual spectra of the distortion for the two will be different.
And, even though both are very flat, they will also differ slightly in frequency response.
(We're talking about the acoustic equivalent of how a slightly foggy windshield will make streetlights look slightly blurred - but often also make them look brighter.)

Mar 19, 2014 9:34:06 GMT -5 garbulky said:

Well it could be adding coloration. Or....the pre-amp you would use it with may have more "robust" circuitry in terms of driving the amps. I auditioned the XDA-1 connected to a USP-1. And the USP-1 produced dynamics that the XDA-1 COULD NOT MANAGE when connected direct to the power amp. Those dynamics were so good ..... even the DC-1 couldn't manage that fast swing from soft to loud with that level of presence when connected direct to the power amp. However the USP-1 was not as clear as either the XDA-1 or the DC-1 connected directly to the amplifier. But it was able to provide those dynamics. I don't know the technical explanation of what I heard. But the difference was reasonably obvious.
I haven't heard the XSP-1 in my system so I can't comment on it.

I actually considered what you said. For instance t could be a different harmonic giving that sound. Also I noticed that the sound was concentrated in the mid-range while the last bit of treble and bass was sacrificed via the USP-1. That could also give that perception.
But... there are a few things that don't quite add up for me when actually listening to the component.I'll try to expand on what I heard before in a later post. But essentialy what I heard was more dynamics so close to real life that the USP-less dynamics were made so much more artificial in comparison. And also the quickness in those dynamics. It was just clean and VERY fast. Zero to hero like that. No "overhang". And if one hasn't heard it before, it's very hard to imagine how dynamics could possibly be better.
But if you do have the time, maybe you could do a listening session and let us know.