The Last Amplifier Project - Pass Labs X600.5 Monoblocks

heiney9

unc2701 wrote: »

They're both balanced designs, so they will both have the same issues with low impedence loads. The difference being that Bryston always under-rates their amps.
http://www.stereophile.com/content/bryston-28b-sst-monoblock-power-amplifier-measurements

The Pass is spec'd at 1% THD; from Stereophile's results, had you cranked the Bryson until you hit 1%, you would get 1300 watts into 8 ohms and 1800 watts into 4 ohms.

I'm not aware of a class A/AB amplifier that truly "doubles down"; manufactures just manipulate the THD at which they report wattage to give the appearance of doubling down. The good news is that at 600 watts into 8 ohms, it'll be far better than the 1% THD reported.

In any case, they're both beasts and I'm sure you'll get plenty of enjoyment from the Pass.

Pass is one manufacturer that doesn't need to manipulate the specs. If anyone is conservative and completely upfront about the design and it's capabilities you won't find another enthusiast or manufacturer that doesn't use marketing speak to explain what's going on. You should read his owners manual's sometime.

All that said, doesn't mean the B&K's are any better or any worse.

H9

F1nut

Very nice, Ray.

Ducati Guy

Congrats,
green with envy.
wow, you're old JC1 monoblocks were my idea of a forever dream system, can't imagine the musical bliss of your new system.
Definitely compare the 2 systems for us.

DarqueKnight

Lasareath wrote: »

Congrats DK!

I'm just surprised that you are going to trade in your beloved JC 1's ?!!!

I would have thought that you would move them down the line?

DarqueKnight wrote: »

I also implemented a "no hoarding" rule in January of 2006 which stipulated that I must make a reasonable attempt to sell a piece of gear unless I have some current or future use for it.

I went over it many times in my mind, but there was no way I could justify, or rationalize keeping the JC 1's. I don't have another system that it would make sense to put the JC 1's in. I would certainly miss them...if only for sentimental reasons.

I still miss my Adcom GFA-5802, and I regret that I never got a chance to implement all the performance improvement tweaks that Adcom recommended.

GlennDog

DarqueKnight wrote: »

I still miss my Adcom GFA-5802, and I regret that I never got a chance to implement all the performance improvement tweaks that Adcom recommended.

Just a coincidence, and certainly not a "dig". . . .

I woke this morning to find my 5802 and Cary SPL-98 idling. . . . I shook my head and said to moi, let's pop one in. There was a noticeably improved "warmth" to the sound. I normally listen 2-3 hours at a time. The Adcom is always fired-up cold (from room temp) but the Cary (Sweet Little Pre-98) is always on stand-by

Anywho, I was impressed/surprised by the SQ diff. Do you think this is justification for NEVER turning your gear off (if you listen every other day)??? I think so . . .


G

DarqueKnight

GlennDog wrote: »

Do you think this is justification for NEVER turning your gear off (if you listen every other day)??? I think so . . .

I think so too. I never turn my two channel system gear off. I do turn off the gear in my secondary systems when I am not using them.

unc2701

DarqueKnight wrote: »

I think so too. I never turn my two channel system gear off. I do turn off the gear in my secondary systems when I am not using them.

Ahhhhh. I was wondering why you included the power consumption at idle in your comparison.

Anyhow, stereophile defines clipping as 1% THD, so the 1800 watts really is an apples to apples comparison with the Pass Labs 1200 watt spec... if you're going purely by specs. (The 900 watt figure given by Bryston is a result of that lump in the graph that crosses Bryston's tighter THD criteria)

As for Pass conservatively rating their amps, that is certainly true in this case- I would bet that into 8 ohms it'd go to about 750-800 watts before it hit 1% THD. "Manipulating the spec" might be a misstatement here; rather, they chose to under-rate the 8 ohm performance to have a 4 ohm "double down" that you see with true class A designs.

But with all things audio, the proof is when you actually get your ears on them. The Aleph is one amp I regret "pass"ing up and its specs look like crap next to just about any other amp I've owned.

heiney9

Which Class A designs are you speaking of that double down? Certainly single ended Class A doesn't double down and many of the Class A First Watt amps and have less power at 4 ohms. What is a "true" Class A design?

H9

BlueFox

DK, good job as always. If they sound as good as they look then you should be happy indeed. How many weeks before you start taking them apart for mods? It will be interesting to see some pictures of how they affect the AC. Will they be plugged into their own line, or your PS Audio conditioner?

I too am getting close to an amp upgrade, but those Pass bad boys will take a bit to much out of my retirement fund. I am looking at the Classe CT-M600 which has similar specs. So far I have not been able to find anything negative about them, versus the Bryston 7B-SST which is also in my price range. Did you investigate the Classe?

http://www.classeaudio.com/ctseries/ct-m600.htm

DarqueKnight

BlueFox wrote: »

How many weeks before you start taking them apart for mods?

I would only mod this if it was something recommended...and approved in writing...by the factory.:cool:

The only "mods" I have done with my Pass gear is change the fuses...and even that was done with written factory approval. The X600.5 does not use fuse protection. It has a magnetic circuit breaker.

BlueFox wrote: »

It will be interesting to see some pictures of how they affect the AC. Will they be plugged into their own line, or your PS Audio conditioner?

They will be plugged directly into the wall. Each amp will have a dedicated 20 amp AC circuit...same as the JC 1's.

BlueFox wrote: »

Did you investigate the Classe?

Briefly. I got the impression that they are more geared toward home theater enthusiasts rather than the sensibilities of two channel stereo enthusiasts.

BlueFox

DarqueKnight wrote: »

Briefly. I got the impression that they are more geared toward home theater enthusiasts rather than the sensibilities of two channel stereo enthusiasts.

Then maybe I should get CA-M600, which is the two channel version. Of course, it is the exact same amp in a pretty chassis for display.

The drawback is it cost $500 more for the chassis. Anyway, again, congratulations. I am thinking of the XP-20 pre-amp as my pre upgrade.

http://www.classeaudio.com/delta/delta-cam600.htm

DarqueKnight

This is the response, in its entirety, that I received from Desmond Harrington, Pass Labs' president and head of industrial (mechanical and aesthetic) design:

"Dear Ray,

Continuous power ratings are miss leading because music is not continuous. In the case of the X600.5, most people never see the meter move which means they are running around 40 watts. If you have inefficient speakers and play music very loud you will get the meter to move. If you play so loud that the meter stays between 1 and 2 o'clock, this means that you are putting out about 800-1000 watts (4 ohms). If you really push the amp you will get 1200 watts but your distortion will be a couple of % and above. At those levels you would not be able to hear 10%. At those levels the amp will get hot and may shut down after a few hours.

We do not measure the amps into 2 ohms, because the AC line starts to sag at that point. However we can take a guess at what the amp will do based on the supply. You will not get 2400 watts continuous out of the X600.5, it will be more like the 4 ohm rating.

Let me know if you have any other questions,

Best regards,

Desmond."

---

Well, I don't know of any home audio speakers that can absorb 1000-1200 watts continuous, but its nice to know that if that kind of transient power is needed, it will be available.

ZLTFUL

As a HUGE fan of the Pass Labs products, you get a big thumbs up from me.

Can't wait to read your impressions.

ZLTFUL

Sort of a side note, Ray, was Boulder ever a consideration? Just curious because I have yet to put my ears on anything of theirs I didn't like. Now...granted...the 3050 might be overkill at [email]2000w@4ohms...and[/email] 355lbs each but my god are they amazing. Hehe.

txcoastal1

In response to DK's post#45

When running my XA30.5 with my Usher MD2's (90db 4ohm) my meters never move till 100db which is way to loud.
When running the amp with my Dynaudio C1 II's (85db 4ohm) the meter moves before getting to reference...I love my Pass

I hope you like yours too.

DarqueKnight

ZLTFUL wrote: »

Sort of a side note, Ray, was Boulder ever a consideration? Just curious because I have yet to put my ears on anything of theirs I didn't like. Now...granted...the 3050 might be overkill at [email]2000w@4ohms...and[/email] 355lbs each but my god are they amazing. Hehe.

No. But I do like reading about Boulder products...especially the prices.

jumpindick

Wow Ray,
That is some serious stuff.. Contrats man. Would be nice if you can do a review after having them and listening them. Just curious what kind of speakers do you have?

Toolfan66

jumpindick wrote: »

Just curious what kind of speakers do you have?

Sorry but I had to LOL!!

disneyjoe7

Very Nice

strider

Beautiful.

heiney9 wrote: »

Which Class A designs are you speaking of that double down? Certainly single ended Class A doesn't double down and many of the Class A First Watt amps and have less power at 4 ohms. What is a "true" Class A design?

H9

That "true" Class A is a loaded question. Who really decides? I do know, however, that the F5 doubles as impedance halves. Down to 2 ohms, IIRC from the manual.

DarqueKnight

jumpindick wrote: »

Would be nice if you can do a review after having them and listening them.

I certainly will do a review.

jumpindick wrote: »

Just curious what kind of speakers do you have?

A heavily modified pair of SDA SRS 1.2TL's. If you are curious about what kind of modifications, here are a few threads:

Improvements-To-Modified-SDA-SRS-1.2TL-Crossover

SDA-SRS-1.2TL-Sonicap-Upgrade

The-AI-1-Dreadnought-Project-Pt.1

Steel-Retaining-Rings-For-SDA-Drivers-And-Passive-Radiators

SDA-Tweeter-Brackets-for-SDA-SRS-1.2TL-SDA-SRS-and-SDA-CRS

Upgrade-Low-Frequency-Inductors-For-the-SDA-SRS-1.2TL

Upgrade-High-Frequency-Inductors-For-The-SDA-SRS-1.2TL

Duelund-Resistor-Upgrade-For-The-SDA-SRS-1.2TL

Sonic-Barrier-Damping-Material-For-SDA-SRS-1.2TL-Crossover

SDA-SRS-1.2TL-Custom-Wood-Panels

In the future, when I am more dedicated to audio than I am now, I will invest in a real, big deal, audiophile-approved pair of loudspeakers...like these exquisite Dynaudio Evidence Temptations; sonic bliss at a mere $44,000 (less than half that used):

D_M

DK,

Did Accuphase or Luxman pass through your laboratory?

drumminman

Whoa! Serious hardware, Raife. :cool:

Congrats and looking forward to the review and comparison with the JC1's. I've never had my ears on Pass gear so I'll wait on your impressions with bated breath.

DarqueKnight

D_M wrote: »

Did Accuphase or Luxman pass through your laboratory?

No. The short list of amps under serious consideration (and their output into 8 ohms) was:


1. Pass Labs X600.5 monoblocks (600 wpc)
2. 28BSST2 monoblocks (1000 wpc)
3. PS Audio Classic 250 bridged monoblocks (1000 wpc)
4. Krell FPB 750 MCx monoblocks (750 wpc)
5. Classe Omega monoblocks (500 wpc)
6. Musical Fidelity KW monoblocks (1000 wpc)
7. Vacuum Tube Logic MB750 monoblocks (750 wpc)

In the end, it came down to a choice between the X600.5 and the 28BSST2.

My main selection criteria were:

1. Stereophonic design philosophy.
2. Output power, particularly performance with low impedance speakers.
3. Mechanical and electrical noise abatement design.
4. Reliability.
5. Company reputation.
6. Access to product information.

With regard to product information, Pass Labs was the only company that I could directly communicate, by phone and email, with the actual designers of the product. Over the years, Nelson Pass (power amp design), Wayne Colburn (preamp design) and Desmond Harrington (mechanical design) have always provided prompt answers to my technical inquiries.

schwarcw

Congrats Raife! I'll bet those mono blocks sound terrific!

Good luck with your new amps!

ZLTFUL

DarqueKnight wrote: »

No. But I do like reading about Boulder products...especially the prices.

True...hehe the 850s run used about what your short list options run new. But my god are they butter smooth. Hehe.

Still hoping for that rich uncle payout or lottery win so that I can build a system around a pair of the new 3060s. They are only 100lbs heavier than the 3050s...

I love that they use engine stands to work on them/move them around the shop...

drumminman

Man, that's some heavy metal :cool:

DarqueKnight

ZLTFUL wrote: »

Still hoping for that rich uncle payout or lottery win so that I can build a system around a pair of the new 3060s.

I think you would also have to build your house around those amps.

ZLTFUL

My original calling was design and architecture. I designed a house long ago that had a room based around a 2 channel system. It was in the lower level and the floor was a bed of 18 inches of sand and pee gravel with a 12 inch concrete slab with in floor radiant heat/cooling with a 1/4 rubberized coating on the floor before the flooring was put down.

But until my rich uncle leaves me a small fortune... lol

I am looking forward to your evaluations. My buddy's shop not too long ago stopped carrying the Pass products before I got back into audio so I never got a chance to put my ears on them.

DarqueKnight

Figure 1. The freight company only sent one person (the driver) with the delivery.

The driver asked why these amplifiers were so big and heavy. I knew he was hinting that he wanted some help, but I initially stood there and watched him struggle for a bit before offering to help.:twisted:

I was surprised that the driver only had a two wheel dolly. I went and got my four wheel flatbed dolly from the garage.


Figure 2. People often mention how hot the X600.5's run, but they actually run about 10 degrees (F) cooler
than my JC 1's, even though they have substantially higher class A bias current. However the X600.5's
spread that heat over a larger and thicker aluminum chassis and far more massive aluminum heat sinks.

The white things in figure 2 are digital thermometers. Idling out in the open, the heat sink temperatures averaged 100 degrees (F). Inside the cabinet, the heat sink idling temperature averaged 105 degrees. After playing music for four hours straight at 85-90 dB-C, the heat sink temperatures averaged 111 degrees (F). This compares to an average of 123 degrees (F) for the JC 1's.


Figure 3. I had just enough room, 3/8" on each side, to slide in the 19" wide X600.5's. I found out that those
aggressively sculpted heat sinks are big for good reason.

In the future, when I am not as dedicated to audio as I am now, I will quit dealing with hot, heavy amplifiers and get a nice pair of 10 pound, 1000 watt, cool running ICE amps.


Figure 4. So far, on the first day's playing, the fan's have not been required.

In anticipation of the X600.5's higher heat, I mounted a quiet 50 cfm fan above each amp's area. It lowered the JC 1's heat sink temperature an average 6 degrees (F). I can just barely hear them at the listening position during the quiet spaces between music selections.

I really don't understand people complaining about the heat. If you buy an amp that is substantially biased in class A, you are going to have some heat.


Figure 5. Such Good Sound! X600.5's installed. The Pass preamps play very well with the Pass power amp.
I noticed a bit of synergy.:cool:


Figure 6. The former JC 1 power amps. Time's up...Sonny's home.


Figure 7. Before I send the JC 1's back for trade in credit, I will re-read the 1987 Stereo Review article that
proved that all amplifiers sound the same. I don't want to be hoodwinked by those slick marketers at the
audiophile amplifier companies.

Other than the heat, the other thing people nitpick about is the brightness of the current meter. Some people wish for a switch that can turn off the meter's light. I do not find the meter to be bright at all. It is about the same brightness as Cary CD 306 Pro Version SACD player's display. The X600.5 meter is less bright than the CD 306's LED's and the XP-30 preamp's display.

The advice from Pass is that the X600.5's take 36 hours to warm up and five days of straight music play to break in.

More later.