Luxman SQ-N150 Integrated Tube Amplifier

@rankaudio "For example, when we play the line-in using digital sources, the volume only needs to be about 12 o’clock to fill the room, while the phone requires 3 o’clock or more and it already sounds out of steam."

@rankaudio Interesting, I never had to use more than a third of the range of the volume control. Are your speakers wired in phase?

@viridian "A quick bit of math will lead us to the native gain of the MM section being 35.7 db, and yes this is below the 40db plus that is typical of most moving magnet phono stages." 

@viridian Can you provide an example of your figures for our edification?

Some highlights from the Stereophile review that @viridian pasted a link to. -

The following measurements are consistent with a modestly powered amplifier well under the ten watts specified by Luxman of "1% or less (1kHz, 10W/6Ω)". Atkinson’s measurement is from 20Hz - 20Khz which is a more accurate measure of an amplifier’s power envelope below 1% THD. 

"I examined how the SQ-N150’s THD+N percentage varied with frequency at 2.83V (equivalent to 1W into 8 ohms and 2W into 4 ohms). The THD+N was low in the midrange into 8 ohms (fig.7, blue and red traces), but rose both into 4 ohms (cyan, magenta) and at the frequency extremes.

Fig.7 Luxman SQ-N150, THD+N (%) vs frequency at 2.83V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta)."

Nothing here suggests the integrated’s phono stage lacks sufficient gain for a MM cartridge with a 3mV output at 1Khz. -

"Turning to the SQ-N150’s phono input, the MM input’s voltage gain at 1kHz with the volume control at its maximum setting measured 68.5dB from the speaker outputs, as specified. The MC input’s gain was a very high 85.8dB, again as specified. The phono input inverted absolute polarity set to both MM and MC input signals. The MM input impedance was 45k ohms at 20Hz and 1kHz, and 35k ohms at 20kHz, these impedances appropriate for MM cartridges. Switched to MC, the phono input’s impedance was 100 ohms across the band."

The following is a link to Paul Miller’s technical analysis of the MP-500 from the Feb 20, 2023, Hi Fi News & Record Review if you’re interested. -

https://www.hifinews.com/content/nagaoka-mp-500-cartridge-lab-report

Just so we’re all well informed here. Do with it what you will.

I really don’t want to dramatize the situation and I appreciate the input, however, if the Luxman’s lack of gain with the phono stage wasn’t a real issue, this subject about gain wouldn’t be drawing attention to itself in the first place in other reviews. It clearly appears to be a subject of concern in a number of reviews and it isn’t just us. It’s obvious that this is a known issue and turning the volume too high just to get reasonable volume levels has side effects without proper gain.

I also can’t edit anything with Audiogon’s old software with regard to the confusion about digital inputs in the OP. What I meant was using digital sources for the line-in stage, so my apologies for the confusion. We also have a Luxman 509z and it too leaves much to be desired with regard to the phono stage. It’s just clear to me that Luxman puts little R&D into their phono stages which is truly sad because they obviously make beautiful integrated amps. 

We have compared lots of gear on my channel, so this is nothing new and it’s not rocket science. The reason I was interested in resolving this phono gain problem is because I absolutely LOVE the sound of this little Luxman sq-150. The sweet, beautiful tone, soundstage and bass are absolutely world class using sensitive speakers like the Volti Razz. 

BTW, for those interested, we haven’t had any issues using any of these cartridges with any of the amps and phono stages with any of the gear I’ve reviewed on my channel for years. The Yamaha A-s3000 phono stage for example is absolutely world class in sound quality in my opinion. We were shocked how good it is, not to mention the sound of the amp itself. We’ll just accept that the phono stages in the Luxman’s are what they are. Thanks to all

We changed the tubes in our SQ-150 from the JJs to Telefunken preamp and Mazda of France power tubes, took a good sound to a great sound. We only stream, through a Luxman N-150 DAC and Melco music server feeding Altec A7-8 VOT speakers. Power is not a problem in the 18’x22’ living room. 1/4 volume yields 80+ DB. Luxman does not recommend tube rolling but a friend who is long time high end audiophile, suggested the tube swap, and he was spot on.

"It’s just clear to me that Luxman puts little R&D into their phono stages which is truly sad because they obviously make beautiful integrated amps." 

"The reason I was interested in resolving this phono gain problem is because I absolutely LOVE the sound of this little Luxman sq-150. The sweet, beautiful tone, soundstage and bass are absolutely world class using sensitive speakers like the Volti Razz." 

"We’ll just accept that the phono stages in the Luxman’s are what they are. Thanks to all"

@rankaudio Points taken.