Pass Labs x250.8 or x350.8

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tarasman

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Hi Everyone,

First time poster for my own selfish reasons, of course. I have an XA30.5 that can't control the woofers on my Revel F208 speakers that are in a VERY lossy room. FYI, there are two 8 inch woofers per speaker, and the impedance where most of the action happens is about 3.8ohms.

I haven't heard either of the .8 amps. I do like the midrange on the XA30.5, but it isn't as spectacular as you move away from the middle. I also think it might be lacking some detail in the midrange in favor of thickening it up a bit. That may be explained by the amps difficulty in driving the speakers, rather than an inherant characteristic.

Kent English from Pass Labs told me "I find with similar speakers that the X250.8 has a tiny bit more warmth in the lower mids and the X350.8 is a tiny bit more neutral and certainly more dynamic; neither better than the other with 89dB speakers but certainly different. "

I keep going back and forth, but at the end of it all, I wonder if anyone with the X350.8 would regret not getting the x250.8 for sonic reasons.

It is interesting to me that the x350.8 has extra transistors. You'd think that would result in lower distortion at the least, but others say matching the transistors gets a lot more difficult as the numbers increase.

I should say that I doubt I would make the x250.8 struggle, I'm just very interested in the "certainly more dynamic" aspect, even at moderate listening levels.

Does anyone with personal experience have anything to share? Did anyone prefer the x250.8 over the x350.8?

TIA
 
TIA, welcome to the fold.

I own a pair of Revel Studio II's, driven buy a pair of X260.8's , IMO they are the 'sweet spot' in the Pass lineup. There are no control issue what so ever with respect to the bass drivers.
 
Based on your choice above, 250.8 vs 350.8, I'd recommend the 250.8 based on it being a little "sweeter" overall. I have extensive listening to the 350.8 and love it but that was on more power hungry Salon2 speakers.
 
Hi tarasman, Joe for sure has tremendous experience in hi-end audio and Kent from Pass is always very supportive and knows his products inside out. So I’ll just add my 2 cts to the views of those guys who I think already gave good advice.

I was facing the same question you have and went for the X250.8 to drive Magico S3 mk2s. I think it comes down to your sonic preferences. As I mostly listen to classic and Jazz the tad of warmth comes in handy with my musical choices. And 500 wpc with the 4 ohm speakers is also plenty. At my listening levels I hardly leave class A.

I have not faced any dynamics issues, but for sure the X350.8 has more power on tap. Both amps certainly have enough headroom for good dynamics and sweetness on the top.


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A fun tidbit: Because of my room, the XA30.5 only hits 98db on my RatShack meter, whether it's a 1khz tone, or music. So, I'm about 9db down from the sensitivity rating of the speaker assuming I'm dumping 128W or so. It's astonishing, but an actual 500W won't even get me to 105db. That said, I think it's common knowledge that Pass underrates their amps. I am going to install a dedicated 20A circuit for the amp, and possibly another for the rest of the gear. My SVS SB16-Ultra already causes voltage drops.

I should mention that my pre-amp is a Sonic Frontiers Line-2 that has been upgraded to "SE+" level from Chris at Partsconnexion. In addition to the SE+ upgrade, I had him replace the coupling capacitors (these are interstage, not output) with very expensive V-Cap CuTF caps. How does this compare to a new pre? No idea. I think it's probably really good, but most tubes seem to have some kind of compromise. If I change out any of the three pairs of tubes, the difference is usually really obvious. Once the amp is replaced, I think the pre will be the weak link. But for now, I probably DO have the sweet midrange thing covered at the pre-amp, and I can certainly sweeten it up if I so desire with less neutral output tubes. I will eventually replace this with something along the lines of a Pass XP-30, or a REF6 that doesn't require 50 year old tubes.

My DAC is a Schiit Yggy. Not sure how popular that is here. I have to say that I like it. My system really does piano right, and I have to believe the DAC gets a lot of the credit.

I see myself stepping up to the Studio II, Salon II, or maybe the new Magico A3 sometime in the future.

So, yeah. It kinda sounds like I'm trying to talk myself into the x350.8. On the other hand, if I wouldn't be able to hear much difference between the two amps, I could be blowing an extra $2k that could have gone towards my next speaker or pre upgrade.
 
Because Pass sounds sooo wonderful [emoji3].

But you’re right, there are also other great amps. I was just cheeky.


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Fair question. Another amp that came up on my radar is the Hegel H30. I haven't read anything bad about it other than it's actually superior in the stereo config vs mono. Bass control is supposed to be off the hook. In fact, things I've read lead me to believe that it's just great in about every way.

Do you have any other amp recommendations for $9000 or less used?

If memory serves, the absolute most amazing amp I ever heard was the big Halcro monoblocks (that don't look like blocks). Incredible separation and dynamics. I saw one for sale on Audiogon, but I just don't know enough about them. Were they unreliable? Did they have some fatal flaw after the honeymoon period? It seems weird that the "greatest amp ever" by many accounts didn't seem to gain a lot of traction.

I like my Pass XA30.5, and it did a pretty good job of driving my Revel M106 speakers, but the F208s require more grunt. So familiarity is a big part of this, but also know I did a lot of research before I bought the xa30.5. Nelson Pass has a great reputation as a contributor to DIY forums, his company has a great reputation, and there is a pretty good resale market for Pass gear.

I've owned some fiddly stuff. My pre-amp has been sent in 5 times over 18 years for fixes and upgrades. My DAC is broken and on its way to Schiit house for repair. That said, I am extremely averse to regularly packing up and shipping something that weighs over 120lbs on even a semi-regular basis. It's hard work, potentially injurious (I ain't 20 anymore) and it's expensive to ship and insure. So for the amplifier especially, reputation and reliability really are important to me.

If I have a reservation about the two Pass amps in question, it's that Pass intentionally added some distortion because a panel of people preferred the sound (I'm sure that's an oversimplification). The .5 certainly measured great, and the .8 really doesn't in some respects. So I'd be going out on a limb by trusting the wizard's judgement. Also, I'd be going from a (small) XA model to a big X model. At the same output rating, I wouldn't be surprised that the XA models sound better, but I'm going from a 414VA xa30.5 to a 2240VA x250.8. Also, it seems there are a lot of super satisfied people driving big expensive speakers with the x350.8, so I figure it has to be great for the money.
 
My feeling is amp power is like money. Better to have too much than too little. Get the 350.8, and better yet, get two X600.8 amps. You can thank me later. :)
 
If it were me, I'd choose the X250.8 - the Pass sound and plenty of power for your Revels. An alternative you might consider is the Bryston cubed series, easier on your back and your wallet. And their 20-year transferable warranty makes them relatively easy to sell if your situation changes.
 
I vote for the 250.8, plenty of power and the 250 series have constantly been compared to amps costing twice as much in reviews. I own one of the original 250's and it is still going strong with no problems.
 
If you have a large room I can see how you might need more power but I am shocked to hear any Pass can't control the F208. It takes current to control your drivers which Pass has plenty of. I'd more inclined to believe you are either over driving the amp or it's not getting the AC it needs, you made the statement your sub drops your voltage. If that's not a tongue in cheek exaggeration, you have a power issue for sure. I can't remember if the 16 Ultra is Class D, if so, it shouldn't draw that much power. If it's A/B it must weigh a ton. If your home AC even flenches with your current set up, you should upgrade there first before ever thinking of a larger amp. You could spend all that money on a new amp and still be at square one.

I'm assuming you are using the 16 Ultra in your 2-channel set up with the Pass? Have you played with the crossover point of the sub and the contour controls on the F208 to see if you can smooth the bass response? Placement adjusts could help as well. I'm also assuming when you say the Pass don't control the woofers it's because you are not getting low end detail. Another question, are you crossing over the F208 where the sub is rolling off or are the F208's full range?

A friend low passed his Salons and added the Ultima sub, I was amazed at how smooth the Salon's response became. It was my friend's room that was the issue. Another friend with Salons I always asked him to turn his sub off when I listened with him, I thought it sounded better that way.

I've seen the F208's driven with far less contenders than the Pass, even a Cambridge 100x2 integrated. So I hope you give my comments some thought. It's not like the F208's are a difficult load in regards to low impedance or swings.
 
I've owned the Hegel H30 and currently the Pass 350.8. Both are amazing amps. I had no intention in replacing my H30, I was completely happy with it.

Mike insisted I demo the Pass, so he sent it to me to try. I never hooked the Hegel back up. The 350.8 did everything the H30 did, but did it better. More detail, better bass control, better separation of instruments and vocals, bigger soundstage, blacker background. My Salon 2's came alive like never before. The 350.8 is neutral. But it still has the warmth to make music enjoyable for hours on end.

I've not heard the 250.8, but I'm sure it's wonderful.
 
Mr. Peabody,

So there are three facts that make me think I need a bigger amp.
1. When I first got the Revel F208 pair, I hooked them up, and the bass was WORSE than the M106s with a sub. I mean, it just didn't sound as good... less distinct, less tuneful.
2. I can only measure 98db in my room without the sub. Yes, that makes the meter go all the way to the right. It's a VERY lossy room (many big openings, and some broadband diffusers). On the other hand, it doesn't sound boxy in my room at all, so I'm happy about that.
3. Since my DAC is in the shop, I connect the F208s to my $200 Yamaha AVR. The tuneful bass came back.

Regarding point 3, my pre-amp is also out of the picture with the Yamaha. You really got me thinking about that. I'm driving a 3m pair of XLRs into my sub, and 1m XLRs into the XA30.5. In the past when I had a different sub, I used the RCA outputs into the sub, and it turned out that it was causing my pre to struggle and the sound wasn't as dynmaic OR open. So part of what I may be experiencing could be the pre struggling to drive these two devices at once. Pass says the .8 series is friendlier to tube pre-amps. I think I'll setup things without the sub when I get the new amp. We'll see what my Line-2 SE+ can do. It WILL be the limiting factor at that point.

Regarding the mains power: I will say that the circuitry they put in my house sucks. You can't run a small compressor in the garage because the GFI interferes. I use a variac for my coffee roaster. Yes, the sub can lower the voltage by 3v, but I was TRYING to do that with some major output. The sub is 1500W contiunous, 5000W peak, and I had it drawing some juice. But I've already scheduled to have a pair of dedicated 20A circuits installed for my listening area.

I understand what you're saying about the amperage of my XA. Doing some math, you realize the XA30.5 literally has more than it can use. But the XA30.5 just doesn't have much in terms of voltage. It has less than cheap AVRs, and I think that's the issue here. Also, woofer control wasn't a strong suit for the XA series; I saw numerous posts of people needing more than an XA60.5 or XA100.5, and those things have a lot more voltage and amperage than my XA30.5. I saw in a review they were comparing the x600.8 to an XS amp. The XS had a LOT more "current" devices by far (whatever that is), and it is more dynamic than the x600.8. So, I don't think the amperage specification tells the whole story.

At first glance it doesn't look like the F208 should require a big amp, but it has some ugly stuff going on down low, and the XA30.5 is NOT a big amp. You're below 4 ohms for the most active regions of bass, and then you have some incredibly ugly phase angles etc. below 30hz. Also, if you look at a chart, you'll see that the F208 is a full 5db boosted in the bass. I've tried the contour setting (which looks like it measure more flat) and it's not enough (with existing gear), and set to "normal", it's a little overkill. I really need to get a USB mic and test the full frequency range of my system. In terms of frequency response, my room is pretty flat from 120hz down to 15hz. I use an old Velodyne SMS-1 (includes calibrated mic) to measure and adjust my sub. I'm sure adjustments will be made with a replacment amp.
 
Tarasman,

I own the X250 and it replaced a Parasound A21. I can't speak for the 250.8 and 350.8 but my Parasound's slew rate(150) is much faster than my Pass and the dampening factor is much better at greater than 1100 vs 150. I found the bass with the Pass to be slower and not as tight. However, the bass has much more punch with the Pass. I see that your XA30.5 has similar specs with a slew rate of 50 and dampening of 150. That could be what you are hearing. More so due to the dampening as the slew rate I believe has more to do with high frequencies and higher slew rate is not always better.

Last week I took my Pass amp and BAT preamp to a friends house who recently bought a pair of Revel Studio 2's. He is using a Parasound A21 and P7 preamp. We tried the Pass with the P7 and one of the first things he noticed was that the bass was slower but it has more oomph and it was more musical. The A21's bass was tighter and faster for sure.
 
Will be interested to know how your next amp pans out with the Revels. I had the Studio 2's for several years and really liked my Simaudio I7 with them. After I sold it I tried many other combinations with varying but lesser success. Some amplifiers just seemed to shut down the bass, over-dampening it, with a resulting anemic sound. It's funny you mention the AVR bringing tuneful bass. One of my favorite combos with my Studio 2's was a Sony receiver I literally got for free. Sure it was a little "woolly" sounding in the bass and the highs were a bit "hashy" but it was very musical and the bass was huge and effortless. I never really understood that and became weary trying to find the right match. Other circumstances led me to sell the Studios but no doubt that they are very rewarding if you find the right match. I do remember Audio Research tubes sounding very good and I believe Mike had a Ref 250 Studio 2 combination for a while that he raved about.


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From what I've read about the 250.8 vs 350.8, and from my experience with Revel, I'd go with the 350.8 thought I don't think you would go wrong either way. I suspect going from 30.5, it is going to sound like you got new speakers. I had the F208's for about 2 years and thought they were excellent. I now have Salon2's.

You mentioned another amp possibility....I'd be remiss to not suggest you look at the Rowland 625 or 625 S2. On the used market, it would fit squarely into your budget. I have the 625 S2 with my Salon2's....it is an outstanding amp in every respect. Build and cosmetics are without peer. Rowland is a classic pairing with Revel. Give it a look.
 
I pulled the trigger on the x350.8, but I will keep Rowland in mind in the future.

What do you find are the biggest differences between the f208 and the salon2? I assume there are some areas that it was a bigger upgrade than others.

I'm reserving final judgement on the F208 until I get the big amp driving them.
 
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