Pass Labs X250

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Rabagast

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I have ML Vista and a X250, its play great! definitive something i can recommend. Had it for some year and no plans for change the amp, but have been considdering to try an McIntosh MC275 MkIV in an be-amp configuration.
 

john65b

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I have built a number of amps and my Pass Aleph 5 and Krell KSA-50 Clones are at the top as far as sonics. They drove my Tympani IVa HF panels perfectly and I finally heard all the microdynamics I was missing. I am convinced something very good happens when you couple Class A and ESLs....For raw power I use my Icepower 1000ASP monoblocks, and they had the LF duty on the maggies Tympanis.

Anyway, I finished building my original CLS (bought the panels used, built the 5kv bias power supply, and used toroidal trannys for the step up), and have been planning on using it over 250hz with the Tympani bass panels. I have not yet tried the Pass A5 or the Krell yet (waiting for the kids and wife to be out of the house), but what I have heard with lesser amps, I was very impressed with the CLS - a whole other level. I like it so much that I sold the Tympani IVa (never thiought I would do that)...

Now need to build the bass panels for the CLS. I have bought discarded Tympani IIId that I need to rewire the LF panels, which will again be on LF duty with the CLS...just looking for a little time to complete everything...
 

JD Fleming

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Kansas City
Amp Manufacturer: Pass Labs
Model: X250
Manufacturer's Suggested Retail Price: $6,000
Used market average price: $2,500
Basic Specs (watts, etc.): 250W into 8 Ohms. 500W into 4 Ohms
What ML speakers are you driving with this amp: reQuests

You can read many reviews of this amplifier online which will include technical specs, graphs, sine wave charts, etc. If you’re interested in any of the Pass Labs amplifiers, read those reviews before reading this review and before auditioning a Pass Labs amp.

This is my first foray into high end amplification. I should state that I believe auditioning amplifiers in an audio store will provide you with information on how the amplifier looks, how it is built, which lights get lit, how it can connect to your system, etc. What it sounds like at the store will not necessarily be any indication of how it will sound when you get it home. If you can, get a demo unit to take home – one that is broken in. This is the only way you’ll know what you’re getting into.

I should also state that I feel that amplifiers are like automobiles. As soon as you take a new one home from the dealer, they depreciate. Buying a used amplifier is like buying a used car – if you know the history of it, feel comfortable with the owner and see how he takes care of his other audio gear, you can feel confident in purchasing his used equipment. The Pass Labs X250 is a discontinued model, so finding a store that had one still in stock was not an option. It originally retailed for $6,000 – which is way more than I could justify spending on an amplifier, but used ones appear on Audiogon for $2500 or thereabouts and that’s where I found this one.

With all that being said, I purchased this X250 amplifier without ever hearing one in my system. I did this based on recommendations by several key people on the MLC site including jtwrace and Gordon Gray. I also did this based on the Nelson Pass history and the high regard and reputation his designs have earned over the years as well as what it says in the X250 user manual:

“The X circuit was designed to be quite happy driving electrostatic and other speakers”

The manual seems like it was written by Nelson himself, and probably was.

The amplifier is a monster. It’s 100 pounds and built like a tank. It is definitely something you don’t want to have to move that often. The big blue meter is nice. It’s nice to see something that will give you an indication of what the amp is doing. Here’s what the meter on the X250 does:

The meter shows bias. So while the amplifiers operates in Class A the meter will be stationary, as it draws more current and enters AB the meter will move.

This replaced a Carver TFM-35X amplifier that was driving my requests and I thought that the Carver did a pretty good job. Boy, was I ever wrong.

Right away I noticed the channel separation of this amplifier is so distinctly better that I may need to do some re-positioning of my speakers. Bass sounds much more controlled and richer. The sound is more airy, refined and open and I can hear more “layers” of instruments.

Here’s my Critical Listening playlist. These are all tracks that really show off the system and sounded exceptional prior to the X250. These are the tracks I use to show off my system to friends listening for the first time.

1. Straighten up and Fly Right from Round Midnight with Nelson Riddle and his Orchestra (2 of 2) by Linda Ronstadt / Nelson Riddle & His Orchestra
2. Blue Light, Red Light (Someone's There) from Blue Light, Red Light by Harry Connick, Jr.
3. Take Five from Time Out by The Dave Brubeck Quartet
4. Your Starter For from Blue Moves by Elton John
5. Funeral for a Friend (Love Lies Bleeding) from Goodbye Yellow Brick Road by Elton John
6. Flight Response from Days of the New II by Days of the New
7. State Of Independence from The Friends Of Mr. Cairo by Jon & Vangelis
8. The Friends Of Mr Cairo from The Friends Of Mr. Cairo by Jon & Vangelis
9. Gold Dust Woman from Rumours [Expanded] by Fleetwood Mac
10. Show Me from The Lexicon Of Love by ABC
11. Tied Up from Flag by Yello
12. Cantaloop from Starbucks Blue Note Blend by Us3
13. Flamenco.A. Go. Go. from Flamenco A Go-Go by Steve Stevens
14. The Downtown from Days of the New by Days of the New
15. No Such Thing from Room for Squares by John Mayer
16. Tempted from Singles 45's and Under by Squeeze
17. Freedom from Listen Without Prejudice, Vol. 1 by George Michael
18. Last Plane Out from Toy Matinee: Special Edition by Toy Matinee
19. To The End Of The Earth from Everybody's Changing by Keane
20. The Frog Prince from Under the Iron Sea by Keane
21. Cowboy Star from Somewhere I've Never Travelled by Ambrosia
22. Don't Go from Upstairs at Eric's by Yaz
23. Sirius from Eye In The Sky by The Alan Parsons Project
24. No Excuses from Jar of Flies by Alice In Chains
25. Badman's Song from The Seeds of Love by Tears for Fears
26. Standing on the Corner of the Third World from The Seeds of Love by Tears for Fears
27. Evil Empire from Blaze of Glory by Joe Jackson
28. Sultans of Swing from Dire Straits by Dire Straits
29. Opaline from Opaline by Dishwalla
30. Yours for the Taking from Libertine by Gene 1
31. We Close Our Eyes from Aces and Kings: The Best of Go West by Go West
32. Pullin' Back the Reins from Absolute Torch and Twang by k.d. lang
33. All Through the Night from She’s So Unusual by Cyndi Lauper
34. Borrowed Heaven from Borrowed Heaven by The Corrs


I won’t go into all of the details while listening to each of these tracks but here a few noteworthy comments:

Straighten Up and Fly Right by Linda Ronstadt w/Nelson Riddle is just an exceptional track that really pushes the limits of any amplifier. The Carver would clip like crazy and send the Denon into meltdown mode (protection circuit – shut off) at high volume passages of this track.

On Cyndi Lauper’s “She’s So Unusual” SACD on track 6 “All Through The Night”, the opening keyboard notes are super crisp and clear and in your face like I’ve never experienced before. At 1:17 into this song, there is a “swooshing” of high octave rings from left to right that I could hear before, but now it’s in the forefront of the soundstage.

Elton John’s “Funeral For a Friend” is one of those tracks that I have been using for critical listening for years as it has incredible dynamics and huge “WOW factor” when playing at high volume levels. The X250 controlled this so beautifully. The sustained organ notes were very strong.

On many of these tracks, I could hear the singer breathing or the air moving thru the instrument or the fingers sliding over the frets.

The Corrs “Borrowed Heaven” sounded like the lead singer was standing right in front of me. The ending of all her words were more pronounced and I could hear her breathing. This was another jaw dropping “WOW.. I’ve never heard THAT before!!” moment.

After about 5 hours of very critical listening at pretty good volume levels, the amp was warm to the touch on the top, the cooling fins and even on the thick metal face.

Conclusion
This is by far the most significant addition to my system EVER and the best $2500 I’ve ever spent. It controls the reQuests very easily and with authority. To me, it didn’t sound “warm” or “tubey” at all.. It just sounded very neutral. Again, I haven’t had much exposure to different types of amps, so maybe I just don’t know what “warm” or “tubey” sounds like. :D

I also noticed that when using my Squeezebox, the settings of the DBX 4BX dynamic range expander had to be lowered, which tells me the amp is able to reproduce alot more range than the Carver could.

I have no other high end amplifiers to compare the X250 to. I’m sure there are others that will sound equally good. I highly recommend getting a high end amplifier like the X250. You won't know what you're missing until you do!

Thanks Nelson!
 

JD Fleming

New member
Joined
Apr 14, 2021
Messages
4
Reaction score
0
Location
Kansas City
Amp Manufacturer: Pass Labs
Model: X250
Manufacturer's Suggested Retail Price: $6,000
Used market average price: $2,500
Basic Specs (watts, etc.): 250W into 8 Ohms. 500W into 4 Ohms
What ML speakers are you driving with this amp: reQuests

You can read many reviews of this amplifier online which will include technical specs, graphs, sine wave charts, etc. If you’re interested in any of the Pass Labs amplifiers, read those reviews before reading this review and before auditioning a Pass Labs amp.

This is my first foray into high end amplification. I should state that I believe auditioning amplifiers in an audio store will provide you with information on how the amplifier looks, how it is built, which lights get lit, how it can connect to your system, etc. What it sounds like at the store will not necessarily be any indication of how it will sound when you get it home. If you can, get a demo unit to take home – one that is broken in. This is the only way you’ll know what you’re getting into.

I should also state that I feel that amplifiers are like automobiles. As soon as you take a new one home from the dealer, they depreciate. Buying a used amplifier is like buying a used car – if you know the history of it, feel comfortable with the owner and see how he takes care of his other audio gear, you can feel confident in purchasing his used equipment. The Pass Labs X250 is a discontinued model, so finding a store that had one still in stock was not an option. It originally retailed for $6,000 – which is way more than I could justify spending on an amplifier, but used ones appear on Audiogon for $2500 or thereabouts and that’s where I found this one.

With all that being said, I purchased this X250 amplifier without ever hearing one in my system. I did this based on recommendations by several key people on the MLC site including jtwrace and Gordon Gray. I also did this based on the Nelson Pass history and the high regard and reputation his designs have earned over the years as well as what it says in the X250 user manual:

“The X circuit was designed to be quite happy driving electrostatic and other speakers”

The manual seems like it was written by Nelson himself, and probably was.

The amplifier is a monster. It’s 100 pounds and built like a tank. It is definitely something you don’t want to have to move that often. The big blue meter is nice. It’s nice to see something that will give you an indication of what the amp is doing. Here’s what the meter on the X250 does:

The meter shows bias. So while the amplifiers operates in Class A the meter will be stationary, as it draws more current and enters AB the meter will move.

This replaced a Carver TFM-35X amplifier that was driving my requests and I thought that the Carver did a pretty good job. Boy, was I ever wrong.

Right away I noticed the channel separation of this amplifier is so distinctly better that I may need to do some re-positioning of my speakers. Bass sounds much more controlled and richer. The sound is more airy, refined and open and I can hear more “layers” of instruments.

Here’s my Critical Listening playlist. These are all tracks that really show off the system and sounded exceptional prior to the X250. These are the tracks I use to show off my system to friends listening for the first time.

1. Straighten up and Fly Right from Round Midnight with Nelson Riddle and his Orchestra (2 of 2) by Linda Ronstadt / Nelson Riddle & His Orchestra
2. Blue Light, Red Light (Someone's There) from Blue Light, Red Light by Harry Connick, Jr.
3. Take Five from Time Out by The Dave Brubeck Quartet
4. Your Starter For from Blue Moves by Elton John
5. Funeral for a Friend (Love Lies Bleeding) from Goodbye Yellow Brick Road by Elton John
6. Flight Response from Days of the New II by Days of the New
7. State Of Independence from The Friends Of Mr. Cairo by Jon & Vangelis
8. The Friends Of Mr Cairo from The Friends Of Mr. Cairo by Jon & Vangelis
9. Gold Dust Woman from Rumours [Expanded] by Fleetwood Mac
10. Show Me from The Lexicon Of Love by ABC
11. Tied Up from Flag by Yello
12. Cantaloop from Starbucks Blue Note Blend by Us3
13. Flamenco.A. Go. Go. from Flamenco A Go-Go by Steve Stevens
14. The Downtown from Days of the New by Days of the New
15. No Such Thing from Room for Squares by John Mayer
16. Tempted from Singles 45's and Under by Squeeze
17. Freedom from Listen Without Prejudice, Vol. 1 by George Michael
18. Last Plane Out from Toy Matinee: Special Edition by Toy Matinee
19. To The End Of The Earth from Everybody's Changing by Keane
20. The Frog Prince from Under the Iron Sea by Keane
21. Cowboy Star from Somewhere I've Never Travelled by Ambrosia
22. Don't Go from Upstairs at Eric's by Yaz
23. Sirius from Eye In The Sky by The Alan Parsons Project
24. No Excuses from Jar of Flies by Alice In Chains
25. Badman's Song from The Seeds of Love by Tears for Fears
26. Standing on the Corner of the Third World from The Seeds of Love by Tears for Fears
27. Evil Empire from Blaze of Glory by Joe Jackson
28. Sultans of Swing from Dire Straits by Dire Straits
29. Opaline from Opaline by Dishwalla
30. Yours for the Taking from Libertine by Gene 1
31. We Close Our Eyes from Aces and Kings: The Best of Go West by Go West
32. Pullin' Back the Reins from Absolute Torch and Twang by k.d. lang
33. All Through the Night from She’s So Unusual by Cyndi Lauper
34. Borrowed Heaven from Borrowed Heaven by The Corrs


I won’t go into all of the details while listening to each of these tracks but here a few noteworthy comments:

Straighten Up and Fly Right by Linda Ronstadt w/Nelson Riddle is just an exceptional track that really pushes the limits of any amplifier. The Carver would clip like crazy and send the Denon into meltdown mode (protection circuit – shut off) at high volume passages of this track.

On Cyndi Lauper’s “She’s So Unusual” SACD on track 6 “All Through The Night”, the opening keyboard notes are super crisp and clear and in your face like I’ve never experienced before. At 1:17 into this song, there is a “swooshing” of high octave rings from left to right that I could hear before, but now it’s in the forefront of the soundstage.

Elton John’s “Funeral For a Friend” is one of those tracks that I have been using for critical listening for years as it has incredible dynamics and huge “WOW factor” when playing at high volume levels. The X250 controlled this so beautifully. The sustained organ notes were very strong.

On many of these tracks, I could hear the singer breathing or the air moving thru the instrument or the fingers sliding over the frets.

The Corrs “Borrowed Heaven” sounded like the lead singer was standing right in front of me. The ending of all her words were more pronounced and I could hear her breathing. This was another jaw dropping “WOW.. I’ve never heard THAT before!!” moment.

After about 5 hours of very critical listening at pretty good volume levels, the amp was warm to the touch on the top, the cooling fins and even on the thick metal face.

Conclusion
This is by far the most significant addition to my system EVER and the best $2500 I’ve ever spent. It controls the reQuests very easily and with authority. To me, it didn’t sound “warm” or “tubey” at all.. It just sounded very neutral. Again, I haven’t had much exposure to different types of amps, so maybe I just don’t know what “warm” or “tubey” sounds like. :D

I also noticed that when using my Squeezebox, the settings of the DBX 4BX dynamic range expander had to be lowered, which tells me the amp is able to reproduce alot more range than the Carver could.

I have no other high end amplifiers to compare the X250 to. I’m sure there are others that will sound equally good. I highly recommend getting a high end amplifier like the X250. You won't know what you're missing until you do!

Thanks Nelson!


I'm new to tis group, this reply is almost twenty years after the original posting, the playlist you have is phenomenal, particularly, Yello, Brubeck, Lauper, Dire Straights.... Just wondering, your mention of the Pass Labs Amps. How does the old Nakamichi Stasis Pa-7 hold up with the newer Pass Equipment, what I'm driving my ML's with?
 

twich54

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How does the old Nakamichi Stasis Pa-7 hold up with the newer Pass Equipment, what I'm driving my ML's with?
I remember the old Nak 'stasis' amps well, I had one ! As to how it would compare today to Modern Pass gear I have no clue as I've never heard a direct comparison. I would expect a re-capped and freshened up PA-7 to 'hold it's own' though !
 

Mirolab

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I remember the old Nak 'stasis' amps well, I had one ! As to how it would compare today to Modern Pass gear I have no clue as I've never heard a direct comparison. I would expect a re-capped and freshened up PA-7 to 'hold it's own' though !
YES!!!.... I am an original owner of a 1995 Nakamichi PA-7AmkII. At 20yrs old, it was sounding dark and sluggish, and developed a bias problem, so I sent it to Jon Soderberg (Vintage Amp Repair) for recapping. He specializes in Thresholds, and is familiar with the Nak. He told me that the Nak is about 90% of what you get from a true Threshold amp.... When I got it back... it was transformed! Possibly sounding even better than new with modern caps that are better than the originals, and new bias pots. This was NOT cheap... like $1400, plus shipping of a 70 lb amp. The PA-7A used sells for less than $1k, so you've got to really want it, but my PA-7A-II has a thickness and solidity in the mid bass that I really like. My main goto amp is a Bryston 4B-ST (also recapped) and I'd say it's the better amp overall, but the Nak still has a certain character that I like. Plus it looks amazing.
I'd really love to hear a Pass X250 in my system.
 

TomDac

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I'm new to tis group, this reply is almost twenty years after the original posting, the playlist you have is phenomenal, particularly, Yello, Brubeck, Lauper, Dire Straights.... Just wondering, your mention of the Pass Labs Amps. How does the old Nakamichi Stasis Pa-7 hold up with the newer Pass Equipment, what I'm driving my ML's with?
Thanks JD!! I remember hearing the Nak amp years ago when it first came out and I loved the sound.. Not sure how it would compare to the X250.
 
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