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Pass Labs XA30.5 in my system?

Dear Audiophiles!

I am looking for a solid-state class A power amplifier with balanced circuit topology to replace Acurus in my modest Hi-Fi setup:
 
Mac mini (USB3 output) ->
Singxer SU-1 ->
Yggdrasil DAC (AES/EBU XLR input) ->
Primare PRE30 preamplifier (AES/EBU XLR input) ->
Acurus A250 power amplifier (RCA input) ->
Monitor Audio RS-6
 
I am currently considering Pass Labs XA30.5 and am wondering if it will “work nicely” with my upstream and downstream components.

Any info/advice is very much appreciated. Please chime in!

Please see the specs below for your consideration.

Pass Labs XA30.5

Type: Solid-state stereo amplifier
Power Output: 30 wpc into 8 Ohm, 60 wpc into 4 Ohm (both 14.8dbW)
Power Consumption (Watts): 238
Temperature (deg C.): 53
Voltage Gain: 26 dB
Input Sensitivity: 0.77 V at 26db gain
Frequency Response: 1.5Hz–100kHz, –3db at 1.5Hz, –2db at 100kHz
Signal/noise: 150db at full power (I cannot believe this is not a misprint!)
Distortion: 0.01% at 3 watts, 0.1% at 30 watts (measured at 1 kHz)
Input Impedance: 30 kOhm balanced, 15 kOhm unbalanced
Damping Factor: 150 for an 8 Ohm nominal load
Maximum Output Current: 20 Ampere
Maximum Output Voltage: ±35 Volts
Output Noise: 150 microvolt unweighted 20 Hz - 20 kHz
DC Offset: <50 mV
Slew rate: ±50 V/µs
Dimensions: 19" (485mm) W by 7" (180mm) H by 19" (485mm) D
Weight: 62 lbs (28kg)
Shipping weight: 75 lbs (34kg)

Primare PRE30 Preamplifier

Balanced inputs          560mV
Line inputs                   280mV
Sensitivity adjustment    -20dB to +20dB
Tape outputs               280mV
Gain                            16dB
Frequency response    DC to 100kHz ± 0.1dB
THD                             <0.01%
Signal-to-noise ratio    -118dB
Crosstalk                      -113dB
Mains                            100/115/230V
Dimensions (WxDxH)    430 x 410 x 100mm
Weight                           9.5kg

Monitor Audio RS6

Frequency Response: 38 Hz - 30 KHz
Sensitivity (1W@1M):   91 dB
Nominal Impedance:     6 Ohms
Power Handling (RMS): 120 W
Recommended Amplifier Requirements (RMS): 40 - 120 W
Tweeter Crossover Frequency: 3 KHz
Drive Unit Compliment: 1 x 6” C-CAM® Bass, 1 x 6” C-CAM® Bass Mid-range. 1 x 1” gold dome C-CAM® tweeter.
Cabinet Design: Balanced velocity twin reflex ported
Product External Dimensions: (H x W x D) 850 x 185 x 250 mm
Plinth Dimensions: (H x W x D): 25 x 255 x 305 mm
Individual Weight: 18 Kg

N.B. Impedance varies with frequency and goes to as low as 4 Ohms and as high as 16 Ohms. And, most importantly,“real” sensitivity is much lower than “nominal”: 87.40dB (averaged 300Hz-3kHz, 2.83V/1m)!
Measurements taken in the anechoic chamber at Canada's National Research Council can be found through this link:
http://www.soundstagenetwork.com/index.php?option=com_content&view=article&id=1221:nrc-measu...

hardball
hardball OP
9 posts
 
Thank you very kindly @wolf_garcia !

My "cave" is only about 14x14x9 and I am concerned about it being overheated. Hence, requirement for a SS amp.
Is there such a thing as fully balanced Tube power amp within my price range? How often is it required to change tubes, please? I would guess, every 2000 - 3000 hours or so? Some of them are made in Russia. How is it even possible to find those in case of necessity?! 

Found one XA30.5 for sale at 3.3K (ouch...). What questions regarding this amp would you recommend me to ask the seller, please? I have no experience with class A gear...
wolf_garcia
6,687 posts
 
Tubes can last years (preamp tubes the longest, power tubes less so but no biggie as switching them out is interesting), there are tons of them available (remember…millions of guitar amps out there use FAR more tubes than hifi ever will), and a tube amp isn't necessarily much less hot that a class A SS amp. One benefit of the small amp I mentioned is the fact that it has 4 under stressed tubes, as opposed to 8 in the amp it replaced. 
hardball OP
9 posts
 
Thank you very kindly @wolf_garcia !

This is totally unexpected: "... millions of guitar amps out there use FAR more tubes than hifi ever will..."! I must confess I had no idea tubes are still in use by musicians, i.e. professionals who can obviously hear the difference and did choose tube-based over SS gear! This is truly astonishing...

Could you please give me a few examples of tube-based power amps working in class A to drive my Monitor Audio RS6? Are they also end-to-end balanced?

If I go tubes with power amp, should I also switch to a tubed preamp as well?

Frankly, I still cannot understand how it is even possible a tube amp dissipating less heat than an SS-only design...

Checked your Sonist Recital 3 speakers: they are work of art!
wolf_garcia
6,687 posts
 
I use a SS preamp (and everything else except the amp) and it sounds fine as it's a very good preamp. I referred to Class A solid state amps only as running hot like a tube amp, as any normal SS amp is much cooler…it is interesting to note how many guitar amps are tubed, and how inexpensive they are relative to hifi stuff (I have a single ended Burriss amp that's hand made, has spring reverb, a preamp, and lists for about a grand). Any "single ended" tube amp is Class A, although regarding balanced stuff they're all over the map…OTL (Output transformerless) Atmasphere amps are balanced and Class A with plenty to read on their site (recommended reading, and the designer often visits this site to comment on things), although a lot of tubes are used in the power amp designs…BAT stuff (Balanced Audio Technology), etc.  Your speakers aren't necessarily efficient (relative to high efficiency speakers) so a low watt amp like mine may not cut the mustard, but I really think tubes are more fun as you can see 'em and mix 'em up (ever take transistors out to look at them?). Have fun.
hardball OP
9 posts
 
Thank you very kindly @wolf_garcia !

I never believed tubes can be superior to transistors in Hi-Fi realm because they are "prehistoric", "archaic", etc. You name it... A friend learned I am on the market for a quality power amp, and was kind enough to bring his PrimaLuna ProLogue Premium stereo power amplifier over. I must confess this amp totally annihilated my Acurus A250: I have never heard my Monitor Audio RS6 giving such punchy, tight, well-articulated bass. Piano and vocals did really come to life as well. I was just moved into another level of realism with this amp. Am I imagining things or it is really in correlation with what you found moving from SS power to tube-based, @wolf_garcia ?

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