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Luxman M900U 2 Channel Power Amp

Frank Dernie

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Yes. In my life, I’ve given up all pleasures (almost). It began with giving up unhealthy eating habits. Then I gave up alcohol. Then I began torturing myself in the gym 5 days a week at 5am. I recently gave up caffeine. This must be the final stage.
I feel I should pass on a warning I was given many years ago.
You don't actually live any longer if you keep fit and eat healthy food, it just feels like it :)
 
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dallasjustice

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Good question, just as monoblocs, I don’t really need two, when one is out on demo it becomes a one amp ‘stereo’ set up.
Keith
Keith,
I read the manual and the JA (Stereophile)measurements. My only concern about them is that they are very low gain amps, even in the high gain setting. I plan to use them as monos not because I need the power. I need the gain to be close to 29db.

I believe the gain is 29db when they are bridged in the high gain setting. At least, that’s what Atkinson said when he measured them. Do know whether that is really correct? The manual doesn’t specify what the gain is in bridged mode.
 

DonH56

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Their spec is 23 dB stereo so an extra 6 dB makes sense going to mono... Twice the voltage, four times the power (in theory).
 

RayDunzl

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I need the gain to be close to 29db.

Can you explain?

If I may (mis)calculate a little:

The DAC3 can be set to 24dbu, same as max setting for Lynx Hilo. This is the level I need

DAC3 output 24dBu:

upload_2018-1-18_14-55-36.png


Add 29dB gain in the AHB2

upload_2018-1-18_14-59-26.png


However I look at it thatsa lotta volts out toward the speakers (more than the AHB2 will provide).

Specified "380 watts bridged mono into eight ohms"

upload_2018-1-18_15-13-18.png



Your speakers are not insensitive.

"Sensitivity (2.83V@1M) 94dB
Nominal Impedance 6 Ohm"

upload_2018-1-18_15-20-25.png


Whoa...

What am I missing?
 
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dallasjustice

dallasjustice

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You are correct to wonder why I’d need so much voltage.

I use DSP which takes off about 6db. I also often use a VST plugin called perfect declipper which chops off another 6db. I usually just leave perfect declipper on all the time. But when I listen to certain wide dynamic range symphony, I really do need all 24dbu out the DAC.

Can you explain?

If I may (mis)calculate a little:



DAC3 output 24dBu:

View attachment 10093

Add 29dB gain in the AHB2

View attachment 10094

However I look at it thatsa lotta volts out toward the speakers (more than the AHB2 will provide).

Specified "380 watts bridged mono into eight ohms"

View attachment 10095


Your speakers are not insensitive.

"Sensitivity (2.83V@1M) 94dB
Nominal Impedance 6 Ohm"

View attachment 10096

Whoa...

What am I missing?
 

Wombat

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Yes. In my life, I’ve given up all pleasures (almost). It began with giving up unhealthy eating habits. Then I gave up alcohol. Then I began torturing myself in the gym 5 days a week at 5am. I recently gave up caffeine. This must be the final stage.


Sounds like mid-life crisis. Don't worry, it will pass. ;)
 

RayDunzl

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You are correct to wonder why I’d need so much voltage.

No problem, just curious, considering the estimated levels. I like a little headroom, too.

I have this guestimation:

upload_2018-1-18_15-51-1.png


Which doesn't quite square with the amplifier spec:

upload_2018-1-18_15-53-12.png


The 49V rms is probably somewhat misleaing, 49V pk to ground, maybe that's how they have to calculate it to meet FTC requirements.

The Output Power numbers appear to be calculated using one leg of the speaker outputs to ground, so may be on the low side of reality, also courtesy of the FTC. scanning the document, it doesn't mention rms or root mean square or ground, and volt is only mentioned once, with sensitivity, so, ???

As I see it, Differential Output makes it 98Vrms available (2400Wrms), or 138.6Vpk (4788Wpk), across the speaker itself, here at Neverland East.

upload_2018-1-18_16-6-47.png


upload_2018-1-18_16-12-0.png


Speaker spec:

upload_2018-1-18_16-17-19.png


Anyway, lots of power headroom available here too.

I don't push too hard. I don't like to break stuff.

I don't hear any strain at the levels I play (loud enough for me when loud is 105dB peaks or a couple more), and the one "Let's see what happens in a calibrated way on this exuberant drum solo" I did with the current setup sounded fine, but also sounded like someone bashing the speakers with a baseball bat for the few moments I let it go (117dB SPL peak noted at the listening position), so, no need...
 

RayDunzl

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Sal1950

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svart-hvitt

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@dallasjustice

I read your story with interest. And I think your experience would be of great interest to many more audiophiles (audiophile in the original meaning of the word).

Just one thing: Why don’t you go active? Or do you plan to use for example Audiolense?
 
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dallasjustice

dallasjustice

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@dallasjustice

I read your story with interest. And I think your experience would be of great interest to many more audiophiles (audiophile in the original meaning of the word).

Just one thing: Why don’t you go active? Or do you plan to use for example Audiolense?
I have been using digital crossovers for many years now. I’ve used both Acourate and Audiolense. In fact, I was one Bernt’s early customers when Audiolense first came on the scene about 10 years ago. I’m no expert tho. I’ve learned a lot and my knowledge is very strong when it comes to using DSP for subwoofer integration. However, I’ve never felt the need to use a digital crossover inside a well designed passive loudspeaker. I use JBL 4367 now. With Audiolense or Acourate, I can get a step response indistinguishable from any well designed digitally active speaker.

Here’s a thread I started which can give some insight into how I currently use AL5.
https://audiosciencereview.com/forum/index.php?threads/cascaded-multi-driver-subwoofers.1341/
 

svart-hvitt

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I have been using digital crossovers for many years now. I’ve used both Acourate and Audiolense. In fact, I was one Bernt’s early customers when Audiolense first came on the scene about 10 years ago. I’m no expert tho. I’ve learned a lot and my knowledge is very strong when it comes to using DSP for subwoofer integration. However, I’ve never felt the need to use a digital crossover inside a well designed passive loudspeaker. I use JBL 4367 now. With Audiolense or Acourate, I can get a step response indistinguishable from any well designed digitally active speaker.

Here’s a thread I started which can give some insight into how I currently use AL5.
https://audiosciencereview.com/forum/index.php?threads/cascaded-multi-driver-subwoofers.1341/

I envy your gear, both new and old (sold) and find your priorities, choices and experience interesting :)
 
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dallasjustice

dallasjustice

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I envy your gear, both new and old (sold) and find your priorities, choices and experience interesting :)
Thanks. I’ll post some pictures of the new Benchmark gear and measurements later on this week (or if you go by ISO 8601 calendar, next week).
 

Sal1950

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Thanks. I’ll post some pictures of the new Benchmark gear and measurements later on this week (or if you go by ISO 8601 calendar, next week).
Can't wait to see the new stuff setup and running!
TIA DJ
 

sofrep811

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By far one of the coolest and most beautiful amps I've seen. I'd seen it before your listing, but if I had $20K burning in my pocket--that's the amp I'd get.
 
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