As mentioned above, I was also pretty concerned about the power of the amp and was set on purchasing an X-250.5 for the Thiels. I eventually settled on the XA30.5 after seeing Nelson Pass explicitly recommend it over the other comparably priced amps in the line.
So far, the amp only moves out of class A at very high volumes, higher than I would use for about 90% of my listening... and still sounds very warm and sweet even when the needle starts bouncing.
As for the problem with the Classe, it's great and I love it, but unfortunately, it's obscuring some detail from my source components. I've got a PS Audio PerfectWave DAC and there is a lot more information in the system when I use it as a preamp and run it directly into the Pass. Alas, my girlfriend loves vinyl, so that's not a solution either.
Ohh, and for those offering solutions, my $2500 cap is for used equipment. I won't buy new. |
Here's a quote from Nelson Pass from a discussion about choosing a Pass amplifier for the 2.4s...
"The XA30.5 will beat out the X250.5 for the first 20 watts or so because it has a much higher bias, and this is particularly true of low impedance loads. (I used Thiel 3.6's to voice the original Aleph 0, and they were 2 ohms across the board). I suggest you take a look at the article Leaving Class A posted at Pass Laboratories which discusses this in detail."
(from: http://www.diyaudio.com/forums/pass-labs/175913-pass-labs-amp-combination-thiel-speakers-need-mr-pass-advice-everyone-5.html) |
Unsound: This doesn't really matter, and I don't know the true state of affairs because I haven't directly compared the XA30.5 to the X250.5, but if you take a look at the entire thread, you'll see that it is actually a recommendation, and that the thread owner A/Bs the two amps on his 2.4s and vastly prefers the XA30.5. And in my listening, I'm in class A about 90-95% of the time.
In any case, this thread hasn't really addressed my actual issue. Regardless of people's perceptions regarding powering the Thiels with a 30 watt amplifier, removing the Classe from the system and using my PS Audio PWD as a preamp allows me to hear significantly more detail from my source components... so some successful preamp pairing suggestions would still be useful. |
By the way, thanks for the folks that did offer some pre-amp suggestions... |
Unsound: Yeah, I've only lived with the amp and speakers for a week or so (both are new to me), so other than some initial impressions of really hearing some great stuff out of the two, I still don't know either in much detail. Perhaps in the end I'll have to decide whether to switch to the 250.5 or change speakers. I certainly was encouraged by the volume level needed to leave class A, so we'll see... And thanks for the rec. |
Ha! It is funny to see people's reactions. The amp does, for example, easily best the Classe, as it should given the quality and price difference. Also, unless I'm mistaken, simply watching the front current meter should provide a pretty good indicator of how much difficulty the 30.5 is having driving the speakers. As I've said repeatedly, I only leave class A for 5 - 10 % of my listening. |
Thanks for all the comments folks... it's been useful, even if somewhat discursive. I've been leaning towards Aesthetix Calypso, mostly because it is fully balanced and has especially high gain, although I see that the Stereophile measurements have its output impedance ranges from 112 ohms at 1kHz to 3900 ohms at 20Hz (balanced). Perhaps that's on the edge of being a problem with the Pass' input impedance?
So far, the other contender I've been considering is the Audio Research LS-17. Most of the other suggestions got axed because they are unbalanced, higher than my price cap, or (in a couple cases) don't come with a remote.
Unfortunately I still need to sell my old system to free up funds for any purchase, so if anyone's interested in Thiel 1.6s, a Classe CAP-151, or an Exemplar Universal player... just let me know. They'll probably be posted next month, hopefully once folks have started to recover from the holidays.
Thanks again for all the input. |
Unsound, not I'm not, I guess I just saw in some other threads that people had used those with Pass Amps and had success... and they were recommended in here. And, perhaps it was just made it an easier choice to be biased towards either tubes or SS. You'd personally choose a solid-state? I did see that there's a Pass X1 up for about $1900. |
Thanks unsound. Despite it's auspicious start, this thread has ended up being useful, both for recommendation and educational purposes... |
For educational purposes, is there a reason that low output impedance is "good" besides the fact that that's what the Pass requires for system matching?
And I do like the features of the Sonic Frontiers Line 3 that I was reading about... |
This thread's been dead for a while, but I thought I would chime in with some conclusions now that I've lived with the XA-30.5 and Thiel 2.4s for a while. Anyway, on these speakers the amp is spectacular, beautiful, quiet, delicate, with great imaging... on quiet, delicate music. As the music gets more complex and ads greater bass requirements, it just can't keep up. Certain disks and movies with that complexity (e.g., rap & hip-hop) just sound flat and uninteresting.
I've discussed the issues with some professionals... Reno-Hifi suggested that the XA-60.5 might ameliorate the problem, Pass themselves suggested (in this order) the XA-100.5, X350.5, and then X250.5. In talking to Pass I even mentioned selling the speakers and getting another well imaging speaker that mated better with the XA-30.5. They said to keep the Thiels... even with the implicit understanding that that might mean going with a different companies' amps.
In any case, I think I will probably try a 250.5 next (the only suggestion within my budget) and see what happens from their. Unfortunately the first pre-amp solution I tried was using an INT-30A, which is a nice one-box solution to my prior pre-amp issues (and cost efficient... just $1200 more than the 30.5). I just added an external phono... the Chinese Jasmine LP2 MKII (after trying a pretty poor sounding PS Audio GCPH). Anyway, I'd like to have done it right the first time, but the journey's been educational. And I guess shortly I'll still be looking for a pre to match to a Pass amp. Keep your eyes open for a mint INT-30A going up in the next couple months. |
What do you folks think about something like a set of Aleph 2s? Quite a bit cheaper than the X250.5, not as much power, but at 200W into 4 ohms, they should be a better mate to the 2.4s than the XA-30.5...
I did mention briefly the possibility of going to something older like the Aleph 0 to the Pass folks and they pretty unequivocally said to do the 250.5... just because the older designs have so much more distortion. |
The original owner of my 2.4s used a McIntosh MC-402... which he certainly loved (I think he was still going to use it with a new pair of 3.7s).
Wish folks had had a warmer response to the idea of the Aleph 2s, that would have saved over 1k over the 250.5. You all convinced me, however, that I'd probably end up reselling them sooner than later.
Thanks for the input. Despite being fairly sold on the 250.5, I am open to trying some other brands, so the other suggestions are welcome. |
Ohhh, and obviously the low end isn't my primary focus (hence even trying the XA30.5 to start with)... imaging is really the most important target as far as I'm concerned. |
Cal3713...if there is a way to audition the X250.5 before purchasing it (or maybe negotiating a time frame in which you can return the amp if it's not a good fit and just be out the shipping costs)?
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I'll just be buying used and hopefully reselling at a negligible loss if I don't like the combo (unless Reno gets a demo/used 250.5 in).
There are a number of McIntosh 402s up right now that are certainly interesting... also assuming that I could resell without too much loss there, so the purchase would be the demo.
I've been scared off of tubes. Everything technical about the match sounds bad, so the only real draw is the characteristic "tube sound." I'm also good at getting worried about non-issues, so I don't like the idea of having to worry about tube maintenance. |
After saying I wasn't interested in any tube amps, I did run across these guys and become interested... The eastern electric 160W mono-block tube amps:
http://www.stereomojo.com/EasternElectricM156TubeMonoblockAmplifiersReviewtm/EasternElectricM156TubeMonoblockAmplifiersReview.htm
They'd be cheaper than the 250.5 and provide a lot of power for tubes, and come with great reviews... |
Also, unsound... in a different thread, I read that the Mcintosh amps (at least the big ones) still double down as impedance drops. So basically, a 402 would give you 400W out of each of the different taps, but if you had a 4 Ohm load on the 8 Ohm tap you'd still pull 800W. It would just tax the amplifier a lot more than if you were attached to the 4 Ohm tap, where you'd be pulling 400W with the same exact load. That said, I don't understand the technology and am just regurgitating someone's anonymous internet post. |
A Chinese amp with an unusual tube, that will put out less power than the amp you currently find to inadequately power the speakers your driving? Good luck with that!
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Ha... well, I see you have a strong opinion on that! I thought I was comparing 60W (the XA-30.5 into 4Ohms) to 160W out of the EE. Still learning how to compare amp output though...
As for the Mac, all I read about was the response into varying loads from a single tap... so the way I read it, from any single output, they will double down in provided Watts as the speaker's impedance drops by half (i.e., goes 4 to 2 ohms). |
Here's a quote from a discussion about Mac autotransformers:
The output autoformers have different windings in them so the 2,4 & 8 ohm taps are like 3 different amps that are optimized for speakers with the corresponding 2,4 & 8 ohm resistances. If you have a MC501 rated at 500 watts and you hook up a 4 ohm speaker to the 8 ohm tap you will get the expected 1000 watt output (maybe a little less). This could cause the amp to go into protection though, it is usually best to match the speakers to the correct tap.
http://www.audiokarma.org/forums/archive/index.php/t-71322.html |
As you know the 60 W @ 4 Ohms of the XA30.5 was the Class A output, the XA-30.5 would actually put out another 130 or so Watts in Class B @ 4 ohms for a total of about 190 Watts @ 4 Ohms.
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Is it the case that many Tube amps don't provide more power as impedance dips? |
This thread is long since dead, but I thought I'd finish it off now that I've tried a Pass Labs X250.5 and compared it to my INT-30A.
The X250.5 had better bass, but in the end the 30A was just much more natural. Vocals (even on hip-hop) sounded more real, and the soundstage was better defined. So, after all the amp comparisons, I ended up keeping the INT-30A, despite the shortcomings. Although I did add a Thiel SmartSub to help put some additional bass in the system. |
