Pre amp for Pass Labs XA30.5 – Tube or SS

I’m updating my system from the bottom up and have settled on the Pass Labs XA30.5 for power amp. The speakers are a pair of Harbeth C7-es3. Now I’m debating between getting a tube or solid state pre amp. Below are the ones I consider:

SS pre amps - Pass XP10, Ayre K-5xeMP

Tube pre amps – Audio Research Ref 3, LS27 used, LS 26, LS-17SE; Conrad Johnson ET-3, ET-3SE used, Premier 17; Leben pre amp.

Can you share your experience in any of these pre-amp with Pass Labs power amps? Any other SS or Tube pre amp that are worth exploring? Obviously, the Audio Research Ref 3 and LS 27 command a higher price.

I’m looking for a good synergy between pre-amp and power with correct output/input impedance matching. Music I listen include: vocal – both female and male, jazz, pop, chamber, symphony, etc. I’m looking for full-body mid, solid bass and extended treble, accurate sound stage, with a focus on vocal presentation.

Any suggestions are appreciated.
Out of what you listed I would chose the XP-10 for the ss choice nothing like system synergy IMO. Then either the ARC ref 3 or 17ls series II cj for the tubed units. The ARC has balanced outputs so that may present an advantage over the cj unit if that matters to you.

Nelson Pass has commented that either cj or ARC work well with his power amps; so take it from there. The ARC will be more analytical (ss) in its presentation whereas the cj will sound more like a tubed unit at least in my experience; both are great pre-amps.


Good Luck and Great Amp Choice by the way.
far not too many tube amps will be good with your amp and definitely not ARC of any model
you can try BAT VK51 or VK31SE, but using solid state preamp is encouraged. I'd choose Wyred4Sound for clarity and transperency.
I’m looking for a good synergy between pre-amp and power with correct output/input impedance matching.
How could anything be better than a Pass preamp?
Directly from the mouth of Nelson Pass.

"Our experience is no problems at all with the ARC or CJ products with regard to interface. The amp doesn't care about source impedance. It's actual input impedance is close to 0 ohms, and the input impedance spec comes from the resistors we put in series with that input. Adding a little more from the source doesn't create issues."

Tls49 I agree and the one I would go with if it were my decision.

If Mr Pass himself says the ARC and the CJ will be fine, thats good
information. Based on the criteria you list as desirable I'd select the CJ line
stage or the Leben(from your stated choices) as most likely to provide the
full body/tone you want(as well as excellent vocals and
soundstaging).Tube rolling will fine tune to your preference. I believe these
two will be more musically engaging and less analytical and dry.
Good Luck,
I would guess the Pass preamp should be the best match, although there should be no problems with the others.

It might come down to what kind of sound you prefer. I would think the Pass will be accurate and clear, while the tube preamps would lend a more tube-like sound. Given that the XA 30.5 may already have a bit of this, you might not want to overdo it. Can you try them out in your system before deciding?
Given the somewhat low input impedance of the Pass amp, specified as 20K single-ended and 30K balanced (those numbers having been essentially confirmed in John Atkinson's measurements), I took a look at the output impedances of the tube preamps listed in the OP for potential incompatibilities.

It should be kept in mind that it is very common for tube preamps to have output impedances at deep bass frequencies that are much higher than their specified output impedances (which are typically at mid-range frequencies). That low frequency rise will occur due to the output coupling capacitor that is used in most (but not all) tube preamps, and will reach a maximum (within the audible range) at 20 Hz.

Chances are that with nearly all tube preamps that will not be of significance to you with your present speakers, because of their somewhat limited deep bass extension. However, it may become a significant factor if you later change speakers, or add a sub that is driven from the preamp's outputs.

Based on my research, I would rule out the Premier 17. From JA's measurements:
The output impedance was below a lowish 800 ohms in the midband and above, but rose to 1.6k ohms at 20Hz, due to the presence of a finite-sized output coupling capacitor. The C-J should therefore be used with a power amplifier having an input impedance of at least 22k ohms if the bass is not to sound a little lean.
Also, the Leben preamp models shown at their website (RS38CX, RS-100, and RS-100U) all have specified output impedances in the vicinity of 600 ohms. I couldn't find any data indicating their 20 Hz output impedance, but the 600 ohm figure is high enough to suggest caution. If you want to consider those models, I would ask the manufacturer what their output impedance is at 20 Hz.

Also, the ARC datasheets for all of their models which are listed in the OP recommend a minimum load of 20K (although without indicating whether that applies to their unbalanced outputs, their balanced outputs, or both). So you should be ok with any of those models, but without a great deal of margin.

Regarding the statement by Mr. Pass that is quoted above, while I certainly would not question any statement he might make, when he says "the amp doesn't care about source impedance" I would point out that that does not necessarily mean that the preamp doesn't care about load impedance.

-- Al
Again it was a direct quote form the designer (Nelson
Pass)concerning tubed pre-amp choices and their ability to
work well with his XA series of amps. I am sure he knows a
fair amount about the amps he designs and their ability to
mate up with other manufacturers tubed pre-amps.

And as far as system synergy goes the best match with a Pass
amp is a Pass Pre-Amp. I suspect any designer is going to
use his own products to optimize their synergies together.


When you say you have "settled" on a 30.5, do you already have it or are you going to be getting it?

In any event, I have a 30.5 and 100.5's and use CJ tube preamps with them. Perfect for me. I didn't feel that they "needed" a tube pre, just that those gave me the sound I enjoy the most.

I did audition a XP20 and liked it a bunch. I don't see how you could go wrong with the 10 especially if you have to buy blind (is "deaf" a better word? smile).

If you do go tube, the length and capacitance of the interconnects should be taken into account.

Tube or ss, I think you're going to have a great system. Good luck.
Did you prefer the Pass preamp over your CJ pre? There's really no guarantee the OP will like the Pass pre more simply because it is the same brand as the amplifier. Depending on the listener's taste and goals,another brand could be a better fit sonically. There's only one way to determine which is preferable and that requires listening.
Thanks everyone for your feedbacks and suggestions. It's been very educational and informative. I'll surely consider the impedance matching when I search the pre-amp.

Meanwhile, for those who have experience listening the various pre-amps (i.e. XP10, Audio Research, CJ, Leben, etc)with Pass Labs XA30.5 or other XA.5, how would you characterize the different sound each pre-amp presents?
As Al stated, impedance matching is always a concern when connecting tube preamps to solid state amps. Thanks to JA for providing the real output impedance for the preamps reviewed in Stereophile.

For comparison consider the input impedance of Pass solid state amps and Balanced Audio Technology solid state amps. Note that BAT makes tubed preamps.

It'll take an atypical tube preamp to work well with Pass amps.

Here's a review for the Pass XP-10 and XA60.5. It gives you an excellent description of their sound, separately and together.

It's very easy to understand why the reviewer says what he does, just from my experience with other Pass equipment.
What is an atypical preamp?

And gives credence to the fact that designers design their
equipment to work together and why for best performance and
system synergy it is best to stay within the same brand.
Hence pass labs amp with pass labs preamp. Especially if
buying deaf; so eloquently stated above. Reno hi-fi offers a
free 10 day trial, all you pay is shipping to and fro if you
don't like it; can't beat that.

I have been using a Thor TA-1000 mk2 with my XA30.5 (upgraded from Aleph 5) for over three years now and I am very happy with the combination. The Thor is 400 ohm and I connect single ended. Highly recommend this combination. I also have a passive preamp that I also substitute at times. My experience concurs with Nelson that any reasonable preamp will probably work.
R0817 -
I'm using a Modwright LS36.5 with my XA30.5 and have enjoyed it greatly. I had the Modwright 9.0SE prior...something about that MW tube preamp sound that does it for me. Might be worth a listen if possible.

The Reno Audio trial option of the Pass seems a good move, you may or may not necessarily prefer this same brand sound.I know people who have ARC amps but prefer non ARC line stages. People use Shindo preamps with non Shindo power amps.It all about what sound you want and this could certainly differ from what the designer voiced to his own taste.What if you simply hear differently?
Chuck, An atypical *tube* preamp is one that has a low worst case output impedance so it can be used effectively with either tubed or solid state amps.

Understand Thanks just never heard it described that way .


I preferred my CJ (ART 2). I did tell Mark at Reno "If tubes ever start giving more trouble than their worth, I will just send you a check". Haven't heard the XP30 since it debuted but would imagine it could close the gap even more.

Agree with you, no guarantees. My rec was if he had to buy "deaf", as I so eloquently put it (thanks Czbbcl). It's just a comfort zone being from the same brand especially if that brand has Nelson Pass behind it.

I think most philes will end up with different brands. You have done extremely well with your same brand pair. It's not often a manufacturer makes a world class amp AND preamp. They seem to excel at one or the other even though they may make a decent attempt at the other.

RO817, to your last question:

My particular tube pres (CJ ARTs and ACT 2.2) seem to give me more harmonics and in their natural order than the different ss ones I've tried but the XP20 was certainly one of the better ones. Gather as much info as you can but it will eventually come down to your ears and preferences.
Your success with and preference for the CJ over the Pass line stage makes my simple point, at some point you just have to listen.

The value I do see in forum advice (if it's not agenda driven or heavily biased) is that sometimes you can't listen before you buy so you gather as much info as you can (hopefully from people like yourself) and take your best shot.

I've used this phrase/formula before but I think it's time to mention it again:

Hypothetically: If 100 people heard my system while alternating between a ss and tube preamp, 95% may prefer the tube pre but you might be one of the 5% that prefer the ss.

95% doesn't make it right, your ears make it right. BUT if you can't listen first it's probably safest to go with the odds.
Well said Onemug.
Onemug have you heard the ET-5 ? I also enjoy the sound of cj pre-amps and feel they make one of the best sounding pre amps in the business. I would go with one of their tube amps but not sure I want to deal with power tubes especially given how good the Pass XA series sound.


Haven't heard the ET-5. I would guess it's pretty nice. I sure like mine paired with the XA's.
One Mug

What amp do you have ?

I have been looking at a pair of LP140M's .

ET-5 vs ET-3SE vs CT-5

Anyone has experience comparing the ET-5 with ET-3 SE? The ET-3SE uses only one tube.

How about the ET-5 vs CT-5? Fundamentally different in sound? Thanks.
I believe the ET-5 uses one vacuum tube as well. Tone audio did a nice review of the ET-5. Basically saying it had 90% of the sound of the GAT for half the price.

One Mug

Sorry I think you have have the XA 100.5's correct? Great amps by the way. I am looking at the Pass XP-20 pre-amp or the cj ET-5 to pait with a pair of XA100.5 or 60.5's. I am sure they will both sound very good. The Pass would fit in my Rack better .

I owned the XA30.5 for a short time. Just for sale. I used it with the XP-20. I was amazed how good this combo could play togheter. I owned the XA-100.5 before. With the XP-20 had the same stunning stage. I tested some Ayre in the past. There is a big difference in depth and stage wide as well. Pass labs makes the stage wider and deeper. I would not even want a pre-amp for free when my stage would become less wide and deep. Ayre had a less deep and wide stage. For the people who want a big and deep stage this would be a no go. With Tube you also will have a wide and deep stage. Wenn you prefer a more warm sound you can choose for tube. Wenn you want more precision I would go for a XP-10.

Correct on the 100.5. I got the 30.5 first and still use it in another system from time to time.

ET-5 or XP20...that would be a tough call. Is there something in the sound of your system that you want more of (or less of)?
First post here, hope it works.
I use a Pass X1 with my XA30.5, the combination was awesome. I'm sure the XP10 would sound even better.
I need a pre-amp as I sold my Cary Tubed Integrated and it looks like I am going with either the 100.5's or 60,5's. How does the 30.5 compare to the 100.5's. I am sure the 100's are better but how much better.

I even thought of trying an XA30.5 paired with an XP-20 as my speakers Focal 1007 Monitors are pretty efficient. Although I did try an INT30A and thought it was a bit light on power but it did sound great.

Thanks Chuck
I don't know why the larger Pass amplifier should sound any better.It has more power to drive speakers with a difficult load and are more demanding of current. With the appropriate speakers the smaller Pass should sound as good at the very least.
I had the 30.5, 60.5 and 100.5. Even with the same speaker you will hear the difference with ease. There is a big difference in quality. The 100.5 has a lot more drive and resolution. Even with a small speaker you can hear the difference with ease. It is more precise. Cause of the precision you will get a more 3D image. There is even a difference in musicallity. To be honest the 100.5 I found a lot better than the 60.5. The difference between the 60.5 and 30.5 is noticeble easilly. But the 100.5 is more musical in sound and more precise. I prefer the 250.5 over the 60.5 as well. The integrated amps Pass makes I found not that convincing as there Poweramps and pre-amps.
I have read and talked to Pass and I understand there is an improvement as you move up the line and just not more power.

hi, I own a xa-30.5 and wondered if there are other users that could comment on the banana plug binding posts...although the connections are snug and secure, there is just not enough depth for the plugs to be completely inserted...sounds great, but it's the only amp I've ever owned where the banana plugs are not 100% inserted

I just checked my 30.5. The tips of my bananas are 3/4" long and I can insert them all the way. They possibly could go in even farther. I also tried some old Monster Cable bananas and a Radio Shack dual banana and they all went in all the way.

How long are the ones you are trying to insert?

btw, the 30.5 comes new with plastic inserts to keep people in "some' foreign countries from plugging their a/c into them. Did you get your 30.5 new and are you in the USA?
I've tried both SS and tube preamps with my X250.5 and I believe I prefer the solid state for the better bass quality. The x250.5 does bass so well that it's a shame to not have a preamp that can do it justice in this department. Depends on your musical preferences however.

And about speaker binding posts on the Pass Labs amps: use spades not banana plugs. Pass amps are not really designed to be used with bananas.
I owned the XP-20 for 2 years. I did a lot of tests in the last 2,5 years with Audyssey Pro. Now with a Onkyo PR-SC5509 with my way of Audyssey Pro measurement it is a lot better with my Pass Labs x250.5 in every aspect. Even wenn I play extrem loud the needle is less moving then witht the XP-20. The stage is wider and deeper. Individual focus is superior to the XP-20. articulation of voices is also superior to what I had with the XP-20. I have to admitt that my way of measurement is totally different than what Audyssey does. Without this, it would be inferior to the XP-20.
Happy Thanksgiving! I just want to report back what I settled with for pre-amp.

I picked up a Ayre K-1xe, which has a separate power supply. It's very natrual and neutral sounding pre-amp with excellent resolution and detail. Great synergy with my Pass Labs XA30.5 as well. Another advantage is that I use balanced XLR between them. Recently, I acquired a Audio Research CD7 tube CD player - a very musical and involving player indeed.

Now I'm re-discovering every and each of my CD collections. Let me tell you this - the front end, both the CD player and pre-amp made a tremendous difference in performance in my system.

Thanks for again for your input.