What tube pre-amps pair well with Pass amps?

I've often wondered about this, for different reasons like the allure of tubes etc.

I'm run the Pass Labs XP-22, XP-17 and the XA60.6s with an analog front-end only. I recently put in a distributed bass array and altogether I'm blown away and quite happy. Yet...

Curiousity and interest got the best of me and I reached out to Pass. Here was their recommendation for tube pres: Atma-sphere, BAT, Conrad-Johnson.

I'd like to know what the OP decided to do. And any other continuing thougths.

billtro
What tube pre-amps pair well with Pass amps?

Many don’t work with quite a few Pass amps as many Pass amps are low input impedance, and a lot of tube preamps are high’ish output impedances
You need to look at output impedance v input impedance 1 to 10 ratio or more for good impedance match. Otherwise it can start to become a voltage divider and "can" squash dynamic impact as well as output level.

Cheers George

When comparing Focals and any amp, pay particular attention to the mid bass.

They tend to be above-average demanding and therefore suppressing output this region. There's no right answer, you might like it suppressed, giving you a built-in loudness curve or matching better with the room.

Given this combo, old school CJ or Sonic Frontiers.

Atma-Sphere MP-3 Pre-Amp fully loaded will give you about 80-85% Of the Mighty MP-1 Performance.


I used to own VAC pre-amps before they are nice and warmer sounding but overall i still like the Atma-Sphere better. 

+1 @jake18aa
I felt the same when I matched up my Pass XA25 with an Aric Audio preamp! This combination makes a wonderfully musical, holographic, and natural presentation of the music that I find extremely satisfying!

I stated earlier in this thread how great my system sounds with a Pass Lab preamp and Pass Lab amps. I have now heard the Aric Motherlode II in my system and it sounds amazing! If you want a tube preamp you should definitely talk to Aric. I ordered one today!

@cal3713 , Yes, thanks. It’s been a while since last read. ...Hence, my suggestions.

Pass Labs whether due to technological or marketing reasons promotes their “super symmetry” as a selling point. This might be best used in balanced mode. Some of the Pass Labs amps have a somewhat low input impedance.  If wanting to use tubes, I suggest considering the Atmasphere and Sonic Frontiers pres.

@unsound If you're curious, here's an article where Nelson explains what the term actually means... https://www.passdiy.com/project/articles/super-symmetric-amplification

I am using the Pass Labs XA-60.8 amps with the Pass Labs XP-22 preamp in balanced mode and I can only say the musical presentation is outstanding in every way. It is very musical and not in the least anemic or lifeless. I have not heard any other Pass Labs preamps, but what I am hearing now is the best I have ever had in my system. 

May I respectfully ask for the names of some pre-amps that meet AES48?

Well ours do of course. Also Backert Labs, if you get the version with an output transformer to do the balanced output. Most preamps that use an output transformer in that manner should be able to support the standard- and it won't matter if the internal circuit is balanced or not.

I have to disagree with Atmasphere on two points:
1. I have a fully balanced Pass Labs XA60.5. The cable does make a difference.
2. I have two high quality Cary preamps. Cary SLP-98P Formula 1 mod, which is single ended. Cary SLP-05, which is fully balanced, but not upgraded. The single ended preamp sounds better with the Pass than the balanced in my case. That is why I am upgrading the SLP-05, for better SQ.

This is actually a really good example of what I was talking about. The Cary does not support AES48- any preamp that has RCA and XLR outputs, and does not need a switch to use one or the other, very likely does not support the standard, and so you will hear differences between cables that can be pretty profound.

One caveat to my points.
My preamps are very close to the Pass amps; so the interconnects are short. With a longer interconnect run, the balanced connections may possibly be superior.

The benefit of balanced operation really does not have much to do with the length of the cable. The benefit can be there even if the cable is only 6 inches.

@cakids
I have Pass Labs XA60.5 amps. My preamps are both Cary Audio - SLP-05 and SLP-98P F1 version. The modified SLP-98P sounds a tad better...

Last year when I was demoing different amps again, I asked Nelson about my own Cary SLP-98/F1 tube preamp pairing with a Pass .5 or .8 amp. He shared having many customers running them already. Guess it’s true :). A buddy with the XA-25 amp also tried with his own SLP98 preamp and liked the pairing a lot. We agreed it was not quite like his strapped triode tube amp, but really nice and musical!

@cakids   +1 !

The bottom line is that preamp quality is more important than using the amp in the balanced mode.

Pass Labs whether due to technological or marketing reasons promotes their “super symmetry” as a selling point. This might be best used in balanced mode. Some of the Pass Labs amps have a somewhat low input impedance.  If wanting to use tubes, I suggest considering the Atmasphere and Sonic Frontiers pres.

@billtro Ama-sphere (unsurprisingly) makes preamps that conform. I presume that Pass does as well. Unsure unfortunately about other brands, perhaps some others will know of some options...

One caveat to my points.
My preamps are very close to the Pass amps; so the interconnects are short. With a longer interconnect run, the balanced connections may possibly be superior.

I have to disagree with Atmasphere on two points:
1. I have a fully balanced Pass Labs XA60.5. The cable does make a difference.
2. I have two high quality Cary preamps. Cary SLP-98P Formula 1 mod, which is single ended. Cary SLP-05, which is fully balanced, but not upgraded. The single ended preamp sounds better with the Pass than the balanced in my case. That is why I am upgrading the SLP-05, for better SQ.
The bottom line is that preamp quality is more important than using the amp in the balanced mode.
Btw, make sure that if you use the Pass Labs in single ended mode, to insert the shorting jumpers, so that the unused half does not introduce noise.

Yabe, do  6H30 tube pre-amps meet the AES48 standard, or is the tube topography considered separate from the line output?  With  impedance matching, I assume your talking to pre-amp/amp impedance?  Can you expand on what your looking for?  FYI, I may be misusing some terms.  If so, please correct me.  TIA.

Hay Atmasphere, thanks for bringing that point up.  May I respectfully ask for the names of some pre-amps that meet AES48?  As you can see, I'm on a steep learning curve and I know I have a lot of work to do, so any further guidance/direction is appreciated.

One thing about balanced operation is that it is meant to help reduce the effect of the interconnect cable. If you've ever auditioned interconnect cables and heard a difference you know what I'm talking about. Audio engineers frequently poo-poo the idea that cables can make a difference, but they are using balanced lines and equipment that supports the balanced standard so they can come that conclusion not realizing that they are talking apples and oranges.

But Pass Labs are balanced input, so if you want to get the most out of both the amp and not have the cable be a big system influence, your investment in the amp will be best served by a preamp that supports the balanced line standard (also known as AES48). Not surprisingly, most high end home audio equipment does not support this standard! That is part of the reason there are exotic and exotically-priced interconnects (balanced cables need not be expensive to sound really right). Its a simple fact that if the preamp does not support the balanced standard, the interconnect cable will be part of the hidden cost of getting the system to sound right.

In a nutshell, here is the standard:
1) pin 1 is ground, pins 2 and 3 are the signal; pin 3 the inverted form of pin 2

2) The signal does not reference ground (instead pin 2 references pin 3 and vice versa) as that can cause a ground loop. This practice also means that the shield of the cable is not used for anything other than shielding and so in this way is fundamentally different from single ended connections!

3) the preamp should be able to drive low impedances with ease and no loss of low frequency bandwidth. 'Low impedances' means less than 5,000 ohms.
If the preamp cannot do these things you'll be hearing cable artifact and you simply won't get everything out of the amp as a result.

I have used ARC Reference 3 with SMc DNA 1 with great success. So, ARC Ref 3, 5, 6 and the SE versions should do very well. Perhaps other 6H30 tube pre's would do as well, like BAT for example. Be careful with impedance matching. PASS are terrific amplifiers for your stated purpose. Good luck. Enjoy.

@scothurwitz Thanks for posting that. My mistake actually just occurred to me yesterday and I was going to hop on to correct the error. Always great to make a mistake like that while correcting someone else's. Much appreciated. And apologies to Kent and Wayne for the mix-up too.

Hi cal3713

Just to set the record straight, Kent English works for Pass Labs in an administrative capacity, Wayne Colburn designs all of their line level preamps and phono preamps. Take care.

Scot

@koetsue13
"Anxiously waiting my Nelson Pass Designed Korg B1 tube preamp! It should be shipping soon"

Cool. I noticed a few reviewers giving it a go. Does yours have the 6P1 Dual Triode device? http://https//6moons.com/audioreviews2/firstwatt4/2.jpg

Lta microzotol ref pre + xa25

Very curious to do a back to back comparison with the 30.8. 

I would agree with laudionut   I've had both an xp20 pre and an xp30 and they did some things very well such as great dynamics and very quiet and very transparent but they lacked musicality in my opinion. I found them to be quite sterile and lifeless and I'm a huge Pass Labs amp fan. I used them both with an xa30.8 and was very disappointed. Sorry Wayne. 

Scot 

billtro

Yes, the xa30.8 has unbelievable drive capability. I used to have a pair of Magnapan 3.7i's with a pair of their DWM woofers wired in parallel to the xa30.8 and that means it was a constant 2 ohm load that the amp "saw" and it drove that setup effortlessly and sounded so musical it wasn't even funny. The are a lot of lesser amps that would have just shut off with that setup. I enjoted that system for 3 years. I am now using a pair of Eminent Technology LFT8B's with that same amp and I love it. Those speakers are 83db efficient and it also sounds amazing. 

I've had a lot of good preamps over the last 5 years such as Parasound JC2, a Mac C52 and a Rogue RP7 and others but the PS Audio BHK preamp was so much more musical with much better tonal color and much more accurate timbre. It just draws you into the music. I think the PS Audio is a very underrated preamp for the money and maybe gets overlooked by audiophiles willing to spend up to $10,000.00. You have to put a pair of vintage 1950's or 1960's nos tubes in it (I used a pair of Telefunken 12au7's) and it just comes to life. It will surprise you, it did me. Retails for $5995.00 and you can pick them up used for between $3 - $4000.00. Bascom H King has been designing tube based electronics for over 50 years! He knows all the tricks. Great preamp for the money. 

The Pass amps sound best when with balanced interconnects. In my opinion, Pass class a/b amps sound very good but their class a designs are magic. If you can take home that xa30.8 and listen to it in your own system I think you'll wind up getting one. Their xa25 is supposed to be a giant killer if you don't run balanced cables. Nelson Pass is another guy who's forgotten more than a lot of these other amp designers may ever know. The guy is a genius. Hope this helps. Good luck.

Scot

I have Pass Labs XA60.5 amps. My preamps are both Cary Audio - SLP-05 and SLP-98P F1 version. The modified SLP-98P sounds a tad better, so the SLP-05 is off to Cary for the Ultimate Upgrade. It should sound as good or better than the 98P when I get it back. The 05 has more features that I like - HT bypass, balanced operation, no phono.

Wow!  Talk about a wealth of info!  While I'm still in my researching phase, I want everyone to know that I appreciate each of you for taking the time to share your experience and perspectives!

@invalid Thanks for the kind words! Offhand, there is no optimization or tweaks needed for any of my preamps to mate seemlessly with any of the Pass amps. I have dozens of happy customers currently using my line-stages with Pass amps without any issue with integration. Feel free to contact me via my website if you have any other specific questions! Best wishes, Aric

The Aric audio preamps seem to be built well with a good circuit design.Can they optimize it for the pass amps when you order one?

I use my Pass XA-60.8 amps with an AR 5 preamp and YG Kipod speakers and the sound is exactly what I want.  My Digital gear is Esoteric N-01, K-01 and the Brinkman Nyquist II.  I am not a vinyl guy.

Anxiously waiting my Nelson Pass Designed Korg B1 tube preamp!  It should be shipping soon: https://diyaudiostore.com/collections/b1-buffer-w-korg-triode-pre-amplifier
I heard one at his place in front of a SIT-3 and an F7 driving Tannoys.  Sublime!

Many years ago , when the X250 was in production, I used a Lector Z.O.E preamp. I think it’s an Italian audio company. Anyway, it sounded really good after trial and error with various nos tubes. I ended up selling it to “upgrade” but it was manhandled during shipping. So sad. Anyway, when my friends come over to hear my new gear a lot of them will compare the new stuff to the Lector/Pass combo , ie , xx isn’t as extended as your old setup. Sort of became a gold standard for them

I’ve run my First Sound preamp with both the X150.8 and the X250.8 with great success.  Outstanding match in all sonic regards.  

Boulder power amps and Focal speakers are a match made in heaven.
I use a Wavac pre amp with my 2060 but also looked closely at VAC pre amps.
Sonically the Wavac - Boulder combo is spectacular, but on paper there are better matched preamps for the Boulder

@billtro please excuse my short sidestep to your thread. Wish you the best in your search. 
Thanks 1markr! One day I may talk to Aric regarding upgrade. Love my Special as designed. 
One needs to know what one wants to achieve prior to throwing resources into upgrades. 

@mesch

I got these details from Aric: the upgraded "Special" has: "Miflex PIO capacitors, all film cap power supply, heavy choke filtering, damper plates for the 6SN7s and features the Vishay resistors as well, but it has the standard iron-core transformers and ALPS remote volume control."

+1 dgarretson I would use a balanced pre with one of Pass Labs balanced amps. The XA25 is single ended. 

@keithr Pass labs most certainly does build active pres: https://www.passlabs.com/product_tags/line-preamps/

The xp20 is capable of 10db of gain.

And technically Kent English is primarily in charge of designing the company's award winning preamps.

Nelson Pass doesn't design active preamps

@1markr My pre is about 2 year old version of the Special. Bought from Aric as a demo. How was your preamp 'souped up'?

You may want a differential balanced preamp to bring out the best in Pass's balanced designs.  I use an AtmaSphere MP-1 preamp with XA 160.8 monoblocks and a modified XP-25 phono stage.  It sounds very clean and can be contoured to taste with tube rolling.

I will agree on his ability to build some of the best solid state amplification afforded the audio community. However, I have had both the XP20 and XP30 in my system(paired with the 60.8's), and they are anemic and lifeless in offering.

If Nelson pass wanted tube preamps, he would have made them  Stick with Nelson's designs. He is the best amplifier designer-engineer there is so why mess with tubes?

+2 for the Aric Audio preamps! @laaudionut, @mesch 

Since we are on the topic of the Pass Labs XA25, I am now running a souped up Aric Audio Special 6SN7 preamp with mine, replacing the already excellent Backert Labs Rhumba preamp, which I used for 3 years.  This was Aric’s own preamp that he used to voice his latest Motherlode II preamp, and it retains most of the Motherlode’s sonic characteristics.  It’s an amazing match with my XA25. 

I'll just note that the aric audio preamps are also 6sn7 based. I'd love to hear one, as every review is very positive (and I agree with many of his well-advertised design options).

+1 laaudionut. I own the Aric Audio Special preamp. Using it now with a BEL 1001 MK5. Plan on getting a Pass XA25 in the future. 

A few iterations back, I had a pair of Sopra II's, the Pass XA60.8's, and Aric Audio's Motherlode preamp...it sounded fantastic! Fast forward to today, and the only piece of gear still in the system is The Motherlode. Call Aric and you will not be disappointed.