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LUXMAN - SQ-N150 Tube Integrated


EmilC

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55 minutes ago, jcn3 said:

 

not that i don't believe you, but how do you know they're nearly identical?

 

I know from analyzing and comparing both circuits which is first half of the 12AX7 is a common cathode gain stage directly coupled to the other half wired as a split load phase inverter. The front is AC coupled to the push pull cathode biased output stage using EL84 tubes. The only difference is Luxman is using a SS rectifier which for all intensive purposes will not affect Class A operation. The two albeit having different rectifiers will perform the same up to the 10 watts or so where it is rated at.

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Circled in Red is the reason you don't want to run the Luxman into class B operation and why they rated it at 10 watts and a Class A amplifier. It can be driven into this area but performance will be awful because they do not AC bypass the cathode bias resistor with a capacitor which will make the output stage have some gross bias shift and crossover distortion. Not a huge deal so long as you keep it under 10 watts.

luxman.png

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2 hours ago, captainbeefheart said:

Circled in Red is the reason you don't want to run the Luxman into class B operation and why they rated it at 10 watts and a Class A amplifier. It can be driven into this area but performance will be awful because they do not AC bypass the cathode bias resistor with a capacitor which will make the output stage have some gross bias shift and crossover distortion. Not a huge deal so long as you keep it under 10 watts.

luxman.png

 

So what's your view of the measurements from JA at Stereophile?

 

https://www.stereophile.com/content/luxman-sq-n150-integrated-amplifier-measurements

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3 hours ago, jcn3 said:

So what's your view of the measurements from JA at Stereophile?

 

Spot on what I would expect, after 10 watts distortion goes through the roof and it clips out at 12.5 watts. Same exact performance and specs you would see from a Fisher 30a console amplifier.

 

I just don't see why Luxman, with just a little extra effort wouldn't improve upon the design, you can easily get 20 clean watts from push pull EL84's and it will still stay in Class A to around 10 watts or so but you get the added benefit of double the output power.

 

Not a bad little circuit but also not great either. I can see if a company was trying to make a very budget oriented amplifier but for $3,300 it's kind of a bad joke.

 

 

luxdist.png

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so outside of the flowery language on the web site (i agree its a bit much), here's my take on the discussion above.

  • the design of the amplifier is a proven, not innovative design
  • the amplifier measures well and operates within specs

subjectively, i find:

  • the amplifier looks great and appears to be very well built
  • it's surprisingly heavy (at 27 lbs) -- it appears the transformers are hearty enough for the job
  • photos of the guts show that it's thoughtfully manufactured
  • it's certainly not cheap, but luxman has a great reputation for durability and longevity 

subjectively, regarding sound:

  • i find the sound to be full, rich, and nuanced
  • i was quite surprised at the quality of the bass, relative to my other experiences with lower powered tube amps
  • soundstage is wide, reasonably deep, and places instruments well
  • i found the sound much more refined than my most recent experiences with tubes (trials with some primaluna amps)
  • it's a great match with my klipsch heresys -- sounds much better than the very nice solid state amps i had tried previously
  • while i haven't had the amp a long time, at this point i would have to give it two thumbs up
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1 hour ago, jcn3 said:

so outside of the flowery language on the web site (i agree its a bit much), here's my take on the discussion above.

  • the design of the amplifier is a proven, not innovative design
  • the amplifier measures well and operates within specs

subjectively, i find:

  • the amplifier looks great and appears to be very well built
  • it's surprisingly heavy (at 27 lbs) -- it appears the transformers are hearty enough for the job
  • photos of the guts show that it's thoughtfully manufactured
  • it's certainly not cheap, but luxman has a great reputation for durability and longevity 

subjectively, regarding sound:

  • i find the sound to be full, rich, and nuanced
  • i was quite surprised at the quality of the bass, relative to my other experiences with lower powered tube amps
  • soundstage is wide, reasonably deep, and places instruments well
  • i found the sound much more refined than my most recent experiences with tubes (trials with some primaluna amps)
  • it's a great match with my klipsch heresys -- sounds much better than the very nice solid state amps i had tried previously
  • while i haven't had the amp a long time, at this point i would have to give it two thumbs up

 

I had a pair of the Fisher 30a mono amps a long time ago and they did sound good, actually a friend of mine still uses a pair in the summertime because of the lower heat output compared to some of his other tube amps and every time he hooks them up he falls in love with them all over again. He is a very hardcore tube enthusiast so that's saying something for the little console amps.

 

The sound was never an issue with the Luxman, I know it will sound good because I know the circuit very well. I was only trying to educate people about the origins of the circuit and that they basically cloned a 50's console amp design. I have no problem with this I just had a good laugh at the sales departments take on the amp. I get it, they have to do their job and fluff up the product but I feel more people would enjoy an honest approach to what it is and actually might like it more since it's a tip of the hat to a nice sounding vintage circuit. I felt the need to explain that the phase inverter circuit since the way Luxman states it is very odd but oh well that's marketing. I suppose initially the name "neo classico" didn't click at first to me but now I feel at least they were reviving an old design hence the classico part. Marketing aside it is very high quality and I don't think anyone should be ashamed of owning one, I just like to give a real world assessment of the circuit to the people interested in the amplifier from an engineering point of view instead of the marketing team point of view. Now I have also had HH Scott 299 amps with push pull EL84 and that is in my opinion a better circuit and better sounding with double the power. I have also designed and built several EL84 push pull amps in my time so I know what they are capable of. Luxman decided to do what they did and that's fine, I am in no way trashing it and telling people not to buy it or anything like that, I suppose at the very least I felt Luxman could have done better with push pull EL84 circuit but that's neither here nor there, they made the amp and sold it and for 10 watts it will sound good if that power range is enough for you.

 

You should get many years of no hassle tube goodness with the amplifier, it does look nice and is built very well. I just hope if people interested in the amp and wanting to purchase one that stumbles upon this thread they will have much better real information about the circuit and it's heritage.

 

Enjoy!!

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14 hours ago, captainbeefheart said:

 

Not a bad little circuit but also not great either. I can see if a company was trying to make a very budget oriented amplifier but for $3,300 it's kind of a bad joke.

 

 

 

 

IMHO that's exactly what "high-end" audio has become.

 

Edit: That being said, I've had Luxman valve amps in my possession for 40+ years.

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2 minutes ago, artto said:

IMHO that's exactly what "high-end" audio has become.

 

Yes this is what also bothers me which is why I give a true analysis of the circuits being sold today that cost a pretty penny. They didn't have to do any R&D on the amplifier circuit because it's a proven design and they just cloned it, typical of many companies. More money goes into marketing and cosmetics vs actual circuit research and development, I don't mean  you have to reinvent the wheel but often times these amps can be much better if effort was put in. Back to the marketing, there is no shame in what they write, I mean the part about the phase inverter is ridiculous and a poor attempt of trying to sound like they are applying state of the art research they have invested in when in fact they just twist words around to sound inventive.

 

I truly believe to be profitable they know that people are going to purchase with their eyes, psychologically you can even fool yourself into thinking something is better if it looks better. For example the same circuit on a piece of plywood vs the Luxman, people will say the Luxman sounds better because it looks way better than a rats nest on plywood although the circuit is the same and the output measure exactly the same. The Crimson 275 scandal was an eye opener for many I would think. A lot of people were in complete denial about it when I didn't even have to put the amp on a test bench to know that a 19 pound amplifier cannot produce 2x 75 watts down to 20Hz with less than 1% THD, it's simple physics. Well unless it's a David Berning ZOTL amp but it wasn't, it had output transformers.

 

I won't name names but there is another company I just found out about that makes very artistic chassis that are very ornate and people are drooling over them but the circuits are nothing great, really the inside is a mess and they are nothing but mediocre circuits done over a million times but the price tag on these amps are in excess of $6,000. Sorry I don't care how nice it looks it also needs to perform excellent and at that price it should run circles around other designs. But again people purchase with their eyes. I personally would rather have an amazing circuit with amazing performance than just eye candy.

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If I remember correctly, Forum member Mark Deneen (former Paragon owner) conducted an experiment to expose what you described C.Beef.

 

The same system components were used for two “identical” systems. One was all messy, cables and wires all over the place, amp components in cheap DIY chassis, and the other all nice and neat, expensive looking. Everyone would choose the clean and expensive system as sounding better – even though all the components were exactly the same.

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Not to change the subject, but currently my favorite amp is NAD M32, a “Direct Digital Feedback Amplifier” (DDFA, technically a Class Z amp, not Class D as is often quoted).

 

Google “Direct Digital Feedback Amplifier” and see what comes up first. Qualcomm. NAD & Cambridge Silicon Radio (CSR) co-developed DDFA starting nearly 15 years ago. Reading Qualcomm’s website you would think this is a Qualcomm invention when in fact hey had nothing to do with it. They simply bought – 15 years after the fact.

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Quote

 

If I remember correctly, Forum member Mark Deneen (former Paragon owner) conducted an experiment to expose what you described C.Beef.

 

The same system components were used for two “identical” systems. One was all messy, cables and wires all over the place, amp components in cheap DIY chassis, and the other all nice and neat, expensive looking. Everyone would choose the clean and expensive system as sounding better – even though all the components were exactly the same.

 

 

Who's to say if cable routing, paying attention to details, and a better enclosure (better isolation from floor borne and airborne vibrations) didn't yield better sound. Sometimes it's the little things that add up to something more.

 

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10 minutes ago, artto said:

Not to change the subject, but currently my favorite amp is NAD M32, a “Direct Digital Feedback Amplifier” (DDFA, technically a Class Z amp, not Class D as is often quoted).

 

From my understanding it's still Class D output architecture with additional modulator and feedback processor chips added to it for improved performance. So people still call them Class D amps because core function is the same with the exception of the added feedback processing technology. I suppose you could take any Class D amplifier and add the two chipsets to them and make them Class Z. I have never done this I admit, but in theory I believe it would be possible.

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11 minutes ago, Shakeydeal said:

 

Who's to say if cable routing, paying attention to details, and a better enclosure (better isolation from floor borne and airborne vibrations) didn't yield better sound. Sometimes it's the little things that add up to something more.

 

 

This is true to a degree, lead dress and layout will change parasitic properties, typically this only effects frequencies above the audio band and can effect the phase margin when feedback is applied, this will only effect stability. So as long as the amplifier is compensated properly for it's layout all is well. Open loop designs these extremely small differences shouldn't be of any concern.

 

The easy way to tell if the output for both devices is the same is doing a null test. If a proper null test is applied and the output sums to zero then you know the outputs are identical and then you can move onto the listening tests.

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26 minutes ago, Shakeydeal said:

 

Who's to say if cable routing, paying attention to details, and a better enclosure (better isolation from floor borne and airborne vibrations) didn't yield better sound. Sometimes it's the little things that add up to something more.

 

Then conduct the same test yourself. And please invite all of us for the demo - you get to test it blind so the rest of us can have a good laugh.

Just sayin'. I'm sure you know what I mean. There are much more important things that affect the sound we hear. Like the recording and the room.

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19 minutes ago, captainbeefheart said:

 

From my understanding it's still Class D output architecture with additional modulator and feedback processor chips added to it for improved performance. So people still call them Class D amps because core function is the same with the exception of the added feedback processing technology. I suppose you could take any Class D amplifier and add the two chipsets to them and make them Class Z. I have never done this I admit, but in theory I believe it would be possible.

Class D amps are not true digital amplifiers. DDFA is.

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I bookmarked that document years ago.

 

If you've read it, and understand it, Class Z is not quite the same as Class D. Similar to Class AB not being quite the same as Class B or Class AB+B, etc.

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31 minutes ago, artto said:

If you've read it, and understand it, Class Z is not quite the same as Class D. Similar to Class AB not being quite the same as Class B or Class AB+B, etc.

 

If you read it I assume you saw where it says

 

"The Zetex Class Z chipset combines with Class D output stages to create high performance amplifiers achieving a THD+N of lessthan 0.004% and dynamic range of 120dB. "

 

And you can read a block diagram pictured below.

 

It's a method of improving upon the deficiencies in Class D amplifiers via output to input processing in the feedback network. I explains how it improves upon the Class D architecture. Did you stop and think when you said and I quote;

 

1 hour ago, artto said:

a Class Z amp, not Class D as is often quoted).

 

 

That possibly they and I are correct and you are not? The definition of the technology was pretty straightforward if you ask me. The block diagram shows the Class D switching output stage is untouched and the outlined section is the only difference which is the method of feedback from output to input implementation.

 

 

classz.png

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1 hour ago, artto said:

Then conduct the same test yourself. And please invite all of us for the demo - you get to test it blind so the rest of us can have a good laugh.

Just sayin'. I'm sure you know what I mean. There are much more important things that affect the sound we hear. Like the recording and the room.


Show me two amps with the same circuit, one homely and a mess, the other neat and tidy in an attractive chassis. The second one is 1k more than the first one, that’s the one I’m ponying up for.

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