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
I can't imagine you not loving this amp in your system which is far from modest.  It will allow you to use XLR connections from your great Schiit DAC/primare and will drive your speakers without issue.  I've been using one for several years and have no desire to upgrade other than random curiosity.
Thank you very kindly Karl!

It is VERY important for me to learn from a Guru my components are compatible with XA30.5. Quite frankly, I was a bit worried my speakers with their "real” sensitivity of only 87.40 dB, 1 meter/2.83 volt input (averaged over 300Hz-3kHz band) are not a good match...

Could you please comment on how hot the XA30.5 gets during prolonged listening sessions? Would you recommend using external forced air cooling (desk fan, e.g.)? My "cave" is only about 14x14x9 and I am concerned about it being overheated... I know, I know it is a silly one, but please give me some pointers here!

I had the RS-6 a few years ago, very nice speaker. I used a McCormack DNA-1 which sounded good. My local dealer had the RS-6 hooked up to the Ayon Titan and wow the sound was amazing, the speaker came alive. You'd probably be thrilled with the XA, but if you ever want to try tubes they seem to work well with that speaker. My $.02
Asking about heat is an excellent question.  It's not so much the amp, but the room that needs cooling - for your personal comfort.  A small room such as yours with a 9ft ceiling will warm up pretty quickly.  (Have a T shirt and shorts on standby.)   If you run your system frequently, expect your electric bills to climb upwards of $15-25/mo - not counting air conditioning.  This is equivalent to a monthly subscription to Tidal.com.

I have two Class A amps - ss and tubes.   In the summer, air conditioning is mandatory.  Fortunately, my AC is fairly quiet - but it does create a constant white noise that can be distracting.  It's not uncommon for people to buy a 2nd amp that runs cooler for just the summer months.  OTOH, a Class A amp is a great space heater in the winter.

Where you live - what kind of climate - what kind of ventilation in the listening room - are all factors in dealing with a true Class A amp.   There are many high quality Class A/B amps that don't generate as much heat.   They put out Class A for the first several watts - which is fine for most listening.
This amp is a bit deceiving... it is called a 30 watt Pure Class A amplifier... It is not,  It is a sliding bias Class A,  but it does put out a Full 30+ watts of Class A before switching to A/B..... I'm sure the spec is published somewhere, but I recall that it will do 100 to 120 watts before going into clipping... Someone out there is sure to know that spec... Either way,  the point is that this amp should have zero issues driving your Monitor Audio. 
I've always thought of a Pure Class A amp as an amp that won't fall out of Class A... Like the old Sumo Nine,  it ran 60 watts of Class A,  never switched to A/B...    Of course, you could fry an egg on it while it was in Idle. 
Thank you all very kindly!

I can only dream of Ayon Titan... @4hannons, would you agree XA30.5 (much less powerful...) is also capable of driving RS-6 nicely?

@steakster, do I understand you correctly there is no need in external forced air cooling (desk fan, e.g.) for XA30.5?

You also noted "There are many high quality Class A/B amps that don't generate as much heat.   They put out Class A for the first several watts - which is fine for most listening." Could you please give me a few examples of such balanced (end-to-end) power amps?

@timlub, could you please explain what you mean by "sliding bias Class A" in case of XA30.5? I think I have seen in one your posts the headroom of XA30.5 is 4dB. Could you please confirm if this is correct?

I believe we have a consensus XA30.5 will drive RS-6 comfortably. Are you guys in agreement PRE30 will also "work nicely" with XA30.5?

What balanced interconnects would you recommend for my setup, please?

Do you believe the stock power cable is adequate?

My budget is rather tight, hence all the bugging... Sorry guys and thank you!

@timlub, could you please explain what you mean by "sliding bias Class A" in case of XA30.5? I think I have seen in one your posts the headroom of XA30.5 is 4dB. Could you please confirm if this is correct?

In a Pure Class A amplifier,  the outputs are at full throttle in idle... that is why the amps generate so much heat... In a sliding bias amplifier, the amps biased is raised so that the amp will output Class A longer,  the higher you raise the bias,  the more output in class A before switching to A/B...I know that other models of Pass do this,  one of the Alephs as well as the 30.8... I suspect it is the same on the 30.5. 
Best to do a search in the Audiogon discussion archives. It has an enormous wealth of information. You will find all the answers to your questions and much more.
I have this amp, wonderful, hope to soon move to the .8 series.

Stereophile's measurements:
http://www.stereophile.com/content/pass-labs-xa305-power-amplifier-measurements#GIlEwhIt3MzcHIZ2.97
The Pass Labs website does a great job of explaining their amplifier designs. If you wanted something that was less heat producing you could try their X series instead of the XA series. But I really don't think you have a problem with the heat from the XA 30.5. The efficiency of your speakers is not an issue with this amp nor are the lower  impedance dips across the frequencies.  
 Because your preamp is fully balanced you shouldn't  worry too much about quality of your balanced interconnects. I have compared A shorter run of Audioquest SKY to a long run (20ft) of regular old Mogami quad XLR microphone cable. The 60 dollar microphone cable was not inferior.  Other designers of balance amplifiers like Atma-sphere would agree that you shouldn't spending too much money on XLR cables  in a fully balanced connection. 
Why did I type Mogami?  I meant Canare star quad XLR.
Thank you ALL very kindly!

Sorry to bug you again... Could somebody please comment on the XA30.5 headroom? 

From Stereophile's measurements: "Ostensibly a 30Wpc class-A design, its measured performance reveals that it can actually deliver clipping-free peaks 6dB higher in power..."

Not sure if I understand this correctly, but does it mean the XA30.5 has a headroom of 6dB?! For example, MC452 has 1.8dB only...

@jaybe noted "I have this amp, wonderful, hope to soon move to the .8 series." EXTREMELY important: could you please give me your considerations? XA30.5 - Stereophile Recommended in 2015...

@karl_desch Are you referring to Canare L-4E6S Star Quad Balanced Audio Cable, please? I can order this XLR from Blue Jeans Cable.

Do I understand correctly you guys believe the XA30.5' stock power cable is adequate?

And last but not least... What do you guys believe would be a fair price for XA30.5 in excellent condition nowdays?


Before changing speakers to a high efficiency design, I had Thiels and an XA-30.5.  I loved the combination. Left the amp on 24 hrs a day and the room would only get hot if I was really pushing the amp for long periods.  At idle or casual listening it was just warm.  I also did not notice huge electricity bills (gas and electric around $90 for a three bedroom house with two people).  
And although folks around these parts argued otherwise while I was shopping, the amp had plenty of power for my speakers.  Thiel 2.4s:   Impedance: 4 ohms nominal, 3 ohms minimum. Sensitivity: 87dB/2.83V/m. Recommended power: 100–400W.  I've posted this a number of times, but I also tried a McIntosh MC402 and a Pass x250.5 and preferred the XA30.5.
The amp has massive headroom yes. Not your typical 30 watt amp.
The Canare cables can be purchased through Blue Jeans Cable.  I actually purchased mine through Amazon!  I use a Cardas Clear power cable on my amp but I have not compared to the stock cord.  
As far as fair price goes, I would strongly recommend you contact Mark at Reno HiFi.  He will give you a fair price on a new, demo or used piece and you will always be able to trade up the line in the future. How about a matching XP-10???  On Agon, I have seen them go for $3000 - $3500. 

Thank you guys!

@cal3713 I understand if XA30.5 can happily drive speakers with 87dB/2.83V/m Sensitivity, and Recommended power of 100–400W, I should have no problems with my Monitor Audio RS6. Most reassuring!

"Left the amp on 24 hrs a day..." in standby mode, I presume?

@karl_desch I have just checked Reno HiFi, and found they have XA30.5 with the following description:
"Used, Excellent condition, about two years old, one year transferable factory warranty, all factory accessories, new factory double-boxing, Satisfaction Guaranteed. S/N 28934. $3295. " Would you consider this to be a fair price, please?

What amp stand would you recommend for XA30.5, please? I have just realized my 17" audio stand is too small for the "monster"!



I use a SolidSteel amp stand and it looks good with the Pass.  MusicDirect sells them.

Call Mark at Reno Hifi and he will likely give you an even better price. He will also likely confirm most of the points made in this forum.

I leave the amp in standby mode when not listening.  It consumes lots of energy at idle so not a great idea to keep it on full power 24 hours a day. Also, not necessary.

cal3713-


the Thiel CS 2.4 is one of the best kept secrets in Audio.

Why did you move to another speaker? Which cabling do you use in your system?  Happy Listening!

hardball-


why not use a Primare power amp to mate w/ the pre-amp?


Happy Listening!

@hardball
@jaybe noted "I have this amp, wonderful, hope to soon move to the .8 series." EXTREMELY important: could you please give me your considerations?

Well, it's a good sounding amp. Drives my 85db sensitivity ATC speakers just fine.
Regarding price, I just looked up "usaudiomart xa30.5" and saw that they've tended to go at around $2700 if you go through a private party.  On the plus side, Reno will let you return it so you're only out shipping if you decide you don't love the amp.
And jafant, I had Thiel 1.6s and 2.4s for over a decade, but would periodically overheat the aluminum drivers (woofers on the 1.6s, midrange on the 2.4s) and need service.  Given where the company was headed after Jim passed (losing Gary Dayton and giving up on the classic design), I decided it was time to change.  Went with Coincident and have thoroughly enjoyed the low power design, although every once in a while I do miss my Thiel & Pass combination (e.g., Rhye: https://www.youtube.com/watch?v=sng_CdAAw8M).  The solid state didn't pair nearly as well with the Coincident so I sold my Pass too (for Coincident's 300b monos).  If I ever can't have tubes sitting out in the open I'll probably switch to one of Nelson's first watt offerings. 
Ohh, and not very coherent yet on cables... ocellia for IC and anti-cables for a reasonably priced speaker solution.
Thanks! for sharing- cal3713
Thank you very much @cal3713 ! For me it is a huge difference: $3300 at Reno and about $2700 at US Audio Mart. My problem is that not many sellers are willing to ship to Canada...

Could you please give me your suggestions on solid-state  power amplifiers with balanced circuit topology biased in such way that they do operate in class A for the first 20W - 30W? Oh, and I would prefer to stay up to 3K used...

I was considering the Son of Ampzilla II stereo power amplifier (http://www.sst.audio/son-of-ampzilla), but in this design Class A bias extends to 10W only (http://www.6moons.com/audioreviews2/sst/2.html).
I recently switched to the Efficient Speaker/Small Tube Amp Camp (ESSTAC). This is after decades of having fun with various SS and tube amps (I also owned an Acurus A250 years ago that sounded fine but had to be sent back to Mondial a couple of times for repair…annoying). I recently bought a pair of Sonist Recital 3 speakers (93db seems like enough efficiency for my purposes) and a Dennis Had "Inspire" SEP "Fire Bottle" amp with 12 massive watts per side (massive…trust me). By far the best sounding rig I’ve owned, and FAR less expensive than one might expect for hifi astonishment.
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...
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. 
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!
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.
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 ?

I avoided tube hifi for years as I also thought tubes would be a chore and wear out. They are sort of, and they do…and I'd been messing with tubes for decades in guitar amps. Then I realized I LIKE to mess with hifi stuff, and fell into tube hifi through a Jolida amp (I'd heard other tube stereo amps, but not enough of them seemingly).  Primaluna amps are well regarded and I like their ability to switch to "triode" mode, and there is something about the linearity of tubes in a well sorted amp along with the 2nd order harmonic musicality that is more suited to my tastes. Note how often descriptions of SS amp designs claim they're "tube like." I've gone over to the "dark side" of tubophilia (!) with the single ended amp I just bought, and it's the best sounding amp I've owned…fun…just fun...
You know, @wolf_garcia , it is good to learn I am not going crazy hallucinating: it is a huge relief to hear from you I am not the only one who was just amazed with the sound transformation when switched from SS to Tube! 
With your years of experience working with tubes you must really know what is out there, and I would appreciate it very much indeed if you could please name some reputable manufacturers of tubed amps.  
I mean in addition to PrimaLuna, Atma-Sphere (way too expensive...), and Jolida you have already told me about.
I have discovered a company named Ayon. Looks like they make excellent amps, but, again, way too expensive for me: their entry level integrated amp, Scorpio (0dB negative feedback!), is for sale at $3550...
Look at the tube amps for sale here on the 'Gon…simply google anything that seems interesting and there ya go! I wound up with a Jolida because I like balanced inputs (I have a balanced preamp) and the 502P had cannon plug inputs at least…not actually balanced inputs but it didn't matter after all. The new version might be actually balanced in (has a switch for that) and it allows more tube types than my amp does. Plus, even the "factory upgraded" version was relatively inexpensive, and I could talk to the Jolida dudes. My new "Fire Bottle" was stumbled into and, again, a bargain.
Hardball,

Another option is going with one of the recent class d amps.

I was a longtime tube and class a user for many years now I put all the heat and messing around with tubes way behind me.

Kenny.

For a lot of us, once you go tubes, there is no turning back. I made the foolish mistake a couple or three years ago of getting rid of all my tube gear and buying a Devialet--which is an attractive, very "nice" sounding, user friendly, all-in-one solution--and within six months, I found I was just not listening to the music very much. As good as the Devialet was, it just did not have that tube magic. 

Bottom line, I sold it and started over, and now I am back in the tubes--and back to listening to music far too long into the night. I agree with Wolfie that the Jolida is a very nice amp. I had a 3502 for a while and really enjoyed it. Eventually I moved on to a Line Magnetic 508ia, which is the best amp I have ever owned and better than I could ever imagine an integrated sounding. The 518ia and 219ia are also excellent, and I have seen the 518 in the classifieds recently. Might be worth looking into, as most of the people who get them seem to like them as much as I do.

I am not sure what your budget is, but somewhere between Jolida, Primaluna, and Line Magnetic (just to name a few), you should be able to find something that will tickle your ears and touch your heart.

If you really want the info on the amp call Peter at Pass Labs, he is a great guy.