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Monoprice Liquid Platinum Headphone Amp Review

SIY

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Was it this thing?

I'm amazed by the 1.6 ohm output impedance on a $6 800 amp. I'm further amazed by the fact that they dare call it "plays nicely with all speakers" (emphases theirs). If made to drive very low-impedance speakers, a large amount of power would be lost in the amp itself.

Yes, that's the one. Even with my not-so-low impedance speakers, there was a lot of frequency response variation because of that. I'd be interested in seeing if the source of some of the odd measurements is the impedance transformation, the power supply, or something in the input/driver stage design. If the impedance transformation circuit is clean, I can imagine that this technology could be used to build an amp with very good performance- output transformers are indeed the chokepoint in tube power amp design.
 

ccw

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It's too bad you passed on the opportunity to listen to the amp when it was in your possession. You might have been surprised at how good it sounds. Maybe particular measurements don't always translate into the sonics you expect?

The Berning topology is unique. Why do so many people love the sound these amps impart despite their "poor performance" as measured by a device? Why did your co-reviewer love it? And please, expectation bias (based on Bernings reputation??)-- is a really lame excuse. Amps do sound different.

Where is the scientific curiosity? Basic scientific method would apply here. At least: Test by measurement device -- Listen with ears -- Question -- Hypothesize...

Instead the grand total of your investigation of this unique amp was:
Test by measurements -- close mind -- publicly pan amp.
 
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SIY

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I know that it's difficult for some to understand what an amplifier does, but fortunately, I do.:cool: This is not true of people who make pronouncements on an amplifier's "sound" using peeking and without understanding what the measurements mean or what they tell you. That's OK- if the worst criticism I can get is based on non-understanding and completely made-up assumptions, I can live with that.
 

NTomokawa

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close mind
If we take that LTA Ultralinear amp, we don't even need measurements to know that the given output impedance of 1.6 ohms would have all kinds of interesting effects on different speakers, unless of course all speakers have perfectly linear impedance curves.

If one tries to drive very difficult loads with that amplifier, such as speakers with a nominal impedance of 2 ohms (or less), then the amp may well fry itself trying to deliver all the necessary current.
 

ccw

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If we take that LTA Ultralinear amp, we don't even need measurements to know that the given output impedance of 1.6 ohms would have all kinds of interesting effects on different speakers, unless of course all speakers have perfectly linear impedance curves.

If one tries to drive very difficult loads with that amplifier, such as speakers with a nominal impedance of 2 ohms (or less), then the amp may well fry itself trying to deliver all the necessary current.

The amp is designed for high efficiency speakers 88db and up.
 

NTomokawa

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I don't think they're marketing it for speakers with high current requirements.
LTA said that the amp "plays nicely with all speakers" (emphasis theirs). I'm not seeing any cop-outs such as a fine print anywhere, so I guess they really mean all speakers. With a 1.6 ohm output impedance.

That's the problem I have.
 

SIY

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LTA said that the amp "plays nicely with all speakers" (emphasis theirs).

I was unaware of that, thanks for the correction. My speakers don't go quite that low, but the LTA did not match them well. I assumed that it was just an unintended application for the amp, but apparently not.
 

ccw

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LTA said that the amp "plays nicely with all speakers" (emphasis theirs). I'm not seeing any cop-outs such as a fine print anywhere, so I guess they really mean all speakers. With a 1.6 ohm output impedance.

That's the problem I have.

They do state on their website, specifically, that the UL is ideally designed for high efficiency speakers 88 db and up, so that's pretty specific.
 
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ccw

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Yes, that's the one. Even with my not-so-low impedance speakers, there was a lot of frequency response variation because of that. I'd be interested in seeing if the source of some of the odd measurements is the impedance transformation, the power supply, or something in the input/driver stage design. If the impedance transformation circuit is clean, I can imagine that this technology could be used to build an amp with very good performance- output transformers are indeed the chokepoint in tube power amp design.

According to LTA, as regards to the measured noise, they said all the Berning Zotl amps show that on the scope due to the 250khz carrier that the tubes are operated at-- and that the noise is not in the audible frequency range or so many db down as to be inaudible.
 

SIY

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According to LTA, as regards to the measured noise, they said all the Berning Zotl amps show that on the scope due to the 250khz carrier that the tubes are operated at-- and that the noise is not in the audible frequency range or so many db down as to be inaudible.

Yes, I'm very familiar with that technology and how it works. The graphs I showed were not scope shots, these are spectrum analyses within the audio band. All that "hair" between the tones is distortion, especially intermod and the weird sideband distortion that the LTA amp showed.

I have been in some severe disagreements with others on this forum about the importance of out-of-band (ultrasonic) noise from switching amps. I think it's very rarely important and bandwidth limit my noise measurements, some others feel that it's of huge consequence.
 

ccw

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Isn't the harmonic distortion expected with any tube amp? I would imagine my 300b set would show prolific low even-order harmonic distortion-- based on it's effect on music-- mostly very nice but relatively weak on complex music like orchestral. Certainly, the LTA plays much cleaner, so the distortion won't be of any consequence if it sounds good.

I looked up some typical "good" distortion spectrum distortion graphs and they very similar to what I see on the LTA. But I'm in no way qualified to analyze these...

And it's critical what kind of speakers an amp is being paired with. I'm using 107 db horns. They are going to sound hard and aggressive with almost all solid state amps. Sets are almost always better with such speakers, with the exception of the Pass Sit series and the LTA's.

I plan to demo the Ultralinear. Hopefully the distortion measurements won't produce a negative expectation bias result! But I doubt it.
 

Wombat

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Hard and aggressive. An old horn put-down. Some other possibilities, you prefer a subdued sound, your horns are impedance mismatched to SS amps(try 1 or 2 Ohm resistance in series) or your horns are not well designed. Sets generally roll-off the upper frequencies, giving a subdued sound.

Have you ever been up close to a trumpeter in a jazz combo? That trumpet is hard and aggressive. My horns do that well. One man's ………… .
 

SIY

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It's not just harmonic distortion- the LTA showed sidebands around every tone, both fundamental and harmonics.

A "good" distortion spectrum is one without any significant harmonics and definitely without spurious sidebands. Like this one, from an amp that costs 3 times less and puts out quadruple the power:

Figure 2 Edge W Distortion Spectrum 1W 555B.png


Any "hard" or "aggressive" will be in the recording or the speakers. This is an amp that is functioning properly.
 

ccw

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Hard and aggressive. An old horn put-down. Some other possibilities, you prefer a subdued sound, your horns are impedance mismatched to SS amps(try 1 or 2 Ohm resistance in series) or your horns are not well designed. Sets generally roll-off the upper frequencies, giving a subdued sound.

Have you ever been up close to a trumpeter in a jazz combo? That trumpet is hard and aggressive. My horns do that well. One man's ………… .
My horns, AvantGarde Duo Mezzo's, are pure heaven playing all horns, including trumpets. These are the exact opposite of subdued, lol. Ask anyone with experience with the AG's (including Jim Smith, who is as experienced as anyone with them ) and they will all tell you to use sets. Or Pass sits for ss.
 

Wombat

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Using specific amps for EQ to tame a 'hot' mid-top-end?

Your post seemed to generalise that high sensitivity horns(107 dB per whatever) will sound hard and aggressive with almost all SS amps. That is a wide-sweeping opinion.
 
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ccw

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It's not just harmonic distortion- the LTA showed sidebands around every tone, both fundamental and harmonics.

A "good" distortion spectrum is one without any significant harmonics and definitely without spurious sidebands. Like this one, from an amp that costs 3 times less and puts out quadruple the power:

View attachment 45768

Any "hard" or "aggressive" will be in the recording or the speakers. This is an amp that is functioning properly.
But it's not just the recording and speaker. The final product- the sound-- is the synergy between components and speakers. Almost all the users of my speakers that I know of use sets because most solid state (as exemplified by the above "ideal" distortion spectrum) will sound overly analytical. I'm looking for a nice middle ground between set and ss for my particular speakers.
 

ccw

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Using specific amps for EQ to tame a 'hot' mid-top-end?

Your post seemed to generalise that high sensitivity horns(107 dB per whatever) will sound hard and aggressive with almost all SS amps. That is a wide-sweeping opinion.
I'm just reporting my first hand experience and along with many others with much more experience than me. Avantgarde makes their own ss amp. I've never heard of anyone using it (though I'm sure there must be a few out there).
 
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