Pass Labs amp combination for Thiel speakers, need Mr Pass' advice ! And everyone...

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Seems that my next power amp will be the XA100.5... or if I don't wanna spend the money maybe a second hand class A Plinius...

Julien,

Why not take Mr. Pass's advice and get a XA 30.5 as your second amp?

I had the pleasure of spending time with a Pass Aleph 0s. It is rated at 30 watts full Class A.

The hifi club I belong to hooked it up to a pair of Apogee Mini Grands as an experiment thinking there was no possible way it would have enough power. To be honest, it was just one of those "let's watch it fall on it's face" sort of experiments. The Apogees had always required large amps with lots of power to sound decent. From the first note, all in the room were blown away. The joke was clearly on us! That 30 watt amp had FAR more control over those speakers than the 200 watt amps we had been listening to. The lesson we learned was it's about the current capability and not the wattage (within reason). I would have been VERY happy to live with that amp, but it was on audition and had to be returned. I've never forgotten the incredible sonics and will definitely own one someday. And yes, the 30 watts got more than loud enough.

I can only assume the XA would be even better.

I'm sure you won't be disappointed and I would submit Nelson knows what he's talking about.

Kind regards,

Steve
 
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Julien,

Why not take Mr. Pass's advice and get a XA 30.5 as your second amp?

I had the pleasure of spending time with a Pass Aleph 0s. It is rated at 30 watts full Class A.

The hifi club I belong to hooked it up to a pair of Apogee Mini Grands as an experiment thinking there was no possible way it would have enough power. To be honest, it was just one of those "let's watch it fall on it's face" sort of experiments. The Apogees had always required large amps with lots of power to sound decent. From the first note, all in the room were blown away. The joke was clearly on us! That 30 watt amp had FAR more control over those speakers than the 200 watt amps we had been listening to. The lesson we learned was it's about the current capability and not the wattage (within reason). I would have been VERY happy to live with that amp, but it was on audition and had to be returned. I've never forgotten the incredible sonics and will definitely own one someday. And yes, the 30 watts got more than loud enough.

I can only assume the XA would be even better.

I'm sure you won't be disappointed and I would submit Nelson knows what he's talking about.

Kind regards,

Steve

You are right. I didn't have the experience nor that much information when I ordered the x250.5, now I understand that the bias/current capabilities are much more important for low impedance speakers such as mine. Apparently the sensitivity is closer to 88db, but even at 87db it shouldn't be a problem since I don't listen at crazy volumes and my normal listening position is under three meters away from the speakers. Isolation is bad in our building so I don't want to play too loud anyway, do not need huge dynamics (sometimes if you're close a little compression is welcome, you don't want to be adjusting the volume at the extremes...), and need controlled but not "big" bass. So my guess is that even into my speakers at medium volumes it shouldn't really leave class A too much. XA30.5 on the way, please tell me I am doing the right thing...
 
I tell you you can spend a lot of $$ then :D

For the "bzzzz" from the amps, Nelson is right it's about DC residual on your AC line.

The Cleaner someone shown could be built easily. A rule of thumb seems you can do one with a big diode bridge, big capacitance bypassed by a high quality fim capacitor. This "DC block filter" can be conveniently built in a plastic box for safety, with a AC line plug in and an AC line plug out. Then you connect your amp on it and it won't bzzzzzz anymore :)

Afterwards you can even build one per apparatus eg one for your source and one for your pre. The rule of thumb is described here: per 100VA, 10.000uF capacitance

DIY Audio Projects

the site uses frames so I can't point out the right page. Go to tips and tricks then •230V/AC DC-Filter

I try to attach pic of schematic here


Technique was used long ago in power amps such as Mark Levinsons. Those modules can be placed right in each DIY apparatus, or in external box for hifi regular. One per element can make the DC block more efficient and capacitance adapted to each element's power consumption.

Less than 10 euro for the filter :cool:

Maybe you'll run the XA on the top and X amp for the bass if yout speaker permits bi-wiring / passive bi-amping ? That way you have to output 2 sets of parallels from the pre and feed each amp. Once gain settings are set, it could run fine ... you'll get bass punch of the X and soft highs and medium from the XAs :) might be a little complicated to set at first, I wish I could help you, if the Thiels permit this of course :) Terrific setup !!! :p


Regards,

nAr
 

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doing the right thing...

....Yeah : http://www.youtube.com/watch?v=_OA4PghOpbM
........Or : YouTube - Snap - The power

I've had the 0s on 86db (/w/m) ESL's, worked like a charm.
In practice, the Aleph 0s is more like a 50W amp : a 50W amp + 86dB sensitivity loudspeakers is near equivalent to a ~30W amp and 88dB loudspeakers.

In my experience, even low sensitivity loudspeakers produce loud enough sound with far less powerfull amps than often used.
A 200W amp is serious hardware, but doesn't turn up the volume so much louder than a handy-size amp.
Plus us entre-midi Europeans seem less hard of hearing than the average North-American, or e.g. the Scandinavian ear flavor.
Noblesse oblige ? :clown:
 
Hi Julien,

In Japan for now, leaving tomorrow very early ...
Come back to France where the weather is very cold it seems (snow)

Have you survived the arrival of the XA-30 ? I just wondered if you had time to plug it and make the usual burn-in tests ...

Forward to hear your comments. And also, did you try passive be-amp with the X amp for the bass :devilr: ?

Best regards,

nAr
 
You are right. I didn't have the experience nor that much information when I ordered the x250.5, now I understand that the bias/current capabilities are much more important for low impedance speakers such as mine. Apparently the sensitivity is closer to 88db, but even at 87db it shouldn't be a problem since I don't listen at crazy volumes and my normal listening position is under three meters away from the speakers. Isolation is bad in our building so I don't want to play too loud anyway, do not need huge dynamics (sometimes if you're close a little compression is welcome, you don't want to be adjusting the volume at the extremes...), and need controlled but not "big" bass. So my guess is that even into my speakers at medium volumes it shouldn't really leave class A too much. XA30.5 on the way, please tell me I am doing the right thing...

Greetings Julien,

Yes, I believe you've done the right thing.

I'm very anxious to hear your thoughts once you've spent time with the XA30.5.

I must disagree with Nar in that I would not mix amplifiers on the top and bottom at this time.

I would bi-wire from the amp to the speakers making sure to use decent wire, and making sure what I used for the bass is heavy gauge; that's it. I would keep it very simple to get a feel of what the amplifier is capable of. Minimizing complexity is usually a good thing in my opinion.

Please keep us updated. I look forward to your comments.

Kind regards,

Steve
 
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Hi Julien,

In Japan for now, leaving tomorrow very early ...
Come back to France where the weather is very cold it seems (snow)

Have you survived the arrival of the XA-30 ? I just wondered if you had time to plug it and make the usual burn-in tests ...

Forward to hear your comments. And also, did you try passive be-amp with the X amp for the bass :devilr: ?

Best regards,

nAr

I'm going to France now... filming a few shows and then getting married... I haven't received the XA30.5 yet, they didn't have it in HK and had to order it. Should arrive in Beijing in a few days when I'm in France... which means I'll give you guys my impressions at the end of the month.
Apogee says I shoudn't biwire and I won't, even if I wanted to Thiel speakers only have two entries...
Anyway thank you guys, I'll keep you informed!
 
First impressions of the XA30.5, right out of the box, compared directly to the X250.5 : would seventeen thousand times better seem exaggerated? Not to me: much more natural, finally it's just music coming out. No more acid-like high frequencies because of the low impedance, much better bass depth and control than the X250.5, and by a wide margin! Do you believe that? I hope this can help people in the doubt to forget the myth about the X series automatically controlling the bass better than a few dozen watts of class A...
Thank you Mr Pass for pointing out to me that higher bias was important with low impedance speakers! That must be why my speakers used to work so well with the Plinius 9200 (high biased AB). Simaudio W5 was beautiful too, I guess they just have more polished highs than the Pass X series... So right now I would recommend to anyone with Thiel speakers or speakers that go down to under 3 ohms especially in the high frequencies to try the XA30.5. Better than anything I've ever tried, and definitely more than enough power ! My 87db Thiel CS2.4 suck a lot of power right now, especially since my VSE modded Sony SACD player has ridiculously low gain and my newly bought Audio Research balanced tube pre doesn't have gain settings. But even like this, even though I'm often in AB mode when I listen loudly, I'm not even close to using the power of the amp. People tend to think that so called headroom is much needed in order to feel an effortless flow of the music, well it may be true to some extent but when you use 100 W at most on the loudest peaks and have 180 W at your disposition it is more than enough. At least the 180 Watts into 4 ohms of available AB power in the XA30.5 give me so much more effortlessness than the 500 Watts in the X250.5! Just music in the air...
So this is for those with the same concerns I had: unless you have speakers under 86db and play really loud in a really big room, I suspect the XA30.5 will be well enough for your speakers, and make some smooth, effortless music for you. I think also that people tend to forget that even if your speakers use a lot of power and the XA30.5 runs AB all the time, this still is one of the best sounding AB amps in the world, I definitely still hear the exact same full bodied smooth XA series class A sound when playing loud in AB push-pull operation. Very different than the X series even while running in class AB, I suppose it is mainly because of the higher bias... And for this price it's a steal! Don't forget that for the exact same amp with just more power, XA160.5 or XA200.5 sell at prices many many times higher and are widely considered as some of the best amps on this planet!
So, we have a winner. XA30.5 gives me a big smile I haven't had for years...
 
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Hi,

I hope people don't mind me unearthing this very old thread, but it hit on a question I have been worrying over exactly--can I run my Thiel CS 2.4's with the XA-30.5/Int-30? The end of the thread is an enthusiastic yes, but I figured it was worth asking one more time--does anyone out there have any similar experiences? Reading Mr. Pass's website, the Thiel's would be just on the side of the 30.5 (as opposed to 150.5), but the Thiel's call for 100-400 watts at 4 ohm. As noted in the thread, the 30.5 can operate above its rated power level in A/B...I will stop here, as I am just an economist, not an engineer. Maybe I will figure this stuff out eventually.

I will be somewhat sad when I buy an amp; this stuff is fascinating. Great website, too.
 
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