[mg3720]

I'll chime in here.

My 20.7’s are driven by  Krell 400e monos:  400 watts 8 ohm, 800 watts 4 ohm.  Both pairs of 3.7’s are driven by Emotiva XPA-1 monos:  500 watts 8 ohm, 1000 watts 4 ohm.  My one pair of 3.5’s are bi-amped with XPA-1 monos as well.  The tri-center is a CCR and a pair of MMC2’s each with their own XPA-1’s.  And lastly, my MGSS1 ‘s  are also driven by their XPA-1’s.  All in one home theater.

I am not too tempted with the new XPR-1 mono.  Double the power?  I think I have enough already.

[medium jim]

Just for the record, it is a rare amp that does double down from 8 to 4 ohms, most will go say from 200 to 275 - 325 or so...

Jim

[Rclark]

No, I just learned about it the other day. It's a new model that's switchable between Class AB and Class A mode, and when it's in Class A, it automatically switches to Class AB above 35 watts. Sounds interesting, no?

I suppose, if you're looking for 35 watts of class A power with a bit of room above that. . I'd be more interested in the big XPR's and what those would be like loafing along at a few percent of their rated output.

[Rclark]

I did have what I consider a seriously powerful amplifier in the Pass X350 – capable of pushing 700W into 4 ohms (the first 40W, or so, into 4 ohms being class A). That bias meter on the front was an indicator of the departure from class A – when it was 'at rest', the amp was running in lovely class A. It was a terrific amp with the MMGs because it 'loafed' along in class A. It was a terrific amp with the 3.7s because it had the goods to render solid, tight, loud bass from them. It was superb with the 3.7s after introducing the XO, because it spent lots of its time in class A (didn't take long to fall in love with that sound).


How could I not answer the call of the obvious? I either wanted to try 100W of class A or something in that range from a valve amp. I'm not going to deny coveting a pair of Pass mono-blocks, but I designed and constructed my cabinet with a single (main) amp in mind – hence, its prominent location. Had I gone that route, I think they'd qualify as 'big guns'. I ended up with a 150W valve amp, which is no small potatoes, but it doesn't qualify as monster power – insufficient, actually, to drive the 3.7s full-range (no big deal because I didn't buy it for that purpose).

I have no objection whatsoever to a thread celebrating seriously powerful amplifiers, but there is no  'one size fits all' statement which can be validly made regarding power requirements (or which technology is 'best'). Context, as with all things, matters. There are many variables to consider.
In fact, I wasn't at all surprised at the results when I tried it. Volume and dynamics weren't issues, but the tautness of the bass was. Prior to redirecting the bottom end away from the 3.7s, which, by the way, is not something I regard in a negative light at all - it's something I prefer as a matter of course. To my ears, the midrange and lower bass approaches the quality of a good pair of stats when the panels aren't asked to reproduce deep bass. It's one choice among many, but it's one that I make without the slightest regret.

Don't forget that I previously did have big power on tap. The 3.7s managed to draw heavily on its reserves when driven full range. I witnessed radical rotation of the meter on the front of the X350.

Yeah they build these big amps for a reason, right? Because they're actually quite useful! Looking at my mmg's and extrapolating out to the size of 3.7's, I could imagine them needing a nice gust to really fill those sails.

[rw@cn]

Nice review on the NewClear amp.

http://www.tonepublications.com/review/the-newclear-nc1000/

[SteveFord]

That's awfully close to nuclear and I have enough things blowing up around me.
I suppose I'm worrying about nothing.
Does anyone here have one?  It sounds pretty promising according to the review.

[srb]

Does anyone here have one?  It sounds pretty promising according to the review.

I'm curious - although certainly much better looking than either the Wyred 4 Sound or D-Sonic ICEPower amps, do the Lundahl input transformers make it sound significantly better the comparable (?) Wyred ST-1000 @ $2000 or the D-Sonic M2-1200S @ $1675?

Steve

[Hasse]

I did have what I consider a seriously powerful amplifier in the Pass X350 – capable of pushing 700W into 4 ohms (the first 40W, or so, into 4 ohms being class A). That bias meter on the front was an indicator of the departure from class A – when it was 'at rest', the amp was running in lovely class A. It was a terrific amp with the MMGs because it 'loafed' along in class A. It was a terrific amp with the 3.7s because it had the goods to render solid, tight, loud bass from them. It was superb with the 3.7s after introducing the XO, because it spent lots of its time in class A (didn't take long to fall in love with that sound).

How could I not answer the call of the obvious? I either wanted to try 100W of class A or something in that range from a valve amp. I'm not going to deny coveting a pair of Pass mono-blocks,

Were you considering the XA100.5´s by chance?

[Rclark]

Nice review on the NewClear amp.

http://www.tonepublications.com/review/the-newclear-nc1000/

Ah, another new class D making the grade in a review.

"Many say the “first watt” is the most important, however I feel they are all important.  I also prefer a lot of power to not so much.  There are a number of classic low power amplifiers, all of which have a tonal magic about them: the Wavac EC-300, the Pass Aleph 3, the McIntosh MC-30, etc., etc.  And as much fun as they’ve been at very low levels, if you don’t have efficient speakers, those amps run out of steam fast. Ultimately, dynamics are just as important as tonal accuracy, or any of the audiophile parameters that try to convince us that we are hearing reality through our stereo systems – even with music that you don’t think demands it.

Low powered amplifiers are always fun to take for a spin, but I always go back to high power at the end of the day, and the NC1000L delivers the goods.  I mentioned Magnepans at the beginning of the review, and after about a month with both the 1.7 and 3.7, unless you are going to drop upwards of $15k on an amplifier, the NC1000L is the amplifier for you – at an introductory price of $2,600."

[kevin360]

Were you considering the XA100.5´s by chance?

Yes, those are exactly what I had in mind (if not the 160.5s). They are pretty costly, though. I lucked into something else. I'm not at all unhappy with what I chose, but I am curious about those XA amps - beauties.

[Hasse]

Yes, those are exactly what I had in mind (if not the 160.5s). They are pretty costly, though. I lucked into something else. I'm not at all unhappy with what I chose, but I am curious about those XA amps - beauties.

So am I. I´m also curious about the REF150 and how they compare.

[Rclark]

Were you considering the XA100.5´s by chance?

These win on sheer looks alone.

[kevin360]

Of course, looks without substance would be pretty much worthless. The beauty is far from skin deep. Pass amplifiers are built. They are very simple, in a way, but they make use of massively paralleled voltage followers with zero feedback. I once read someone rationalizing that the smaller X-series amps were more linear (than their larger siblings)  because they were simpler, but the design is essentially the same throughout the family – the output device count increases as the power rating increases. Since the output waveform is an average of all of them, the greater the number of devices, the less each one's influence – ergo, greater linearity.

My valve amp doesn't have much on the X350 in terms of heat production. Oh, it dumps more heat into the room, but it's a fractional increase as opposed to a factorial one. In my current configuration, a pair of 'puny 100 watt' XA100.5s would more than suffice – I'm sure of it (whether or not I'd drive them out of class A is another question).

As much as I acknowledge that one should not select a product on the basis of looks, I don't mind paying for a pretty face – as long as the 'pretty' goes all the way through the bones. Pass amps are beautiful – in a fractal sense. So, I think, are VAC's products. I don't deny being called by its physical beauty, but ever more so because that appealing form follows a maximally ergonomic function.

Here it is in modified form. There's only a slightly visible hint that something is different. Behind the lower center of the plexiglass front (which simply lifts off – there is a switch on the rear apron for the lights), there is a reflection being cast by a new display with eight LEDs. If a tube misbehaves, B+ is lifted and an LED illuminates to indicate which tube caused the shutdown. It works – there's something I adore about thoughtful engineering (even more so when I witness it in action - beautiful).

It weighs in excess of 100lbs, which is a pretty big amp.

[josh358]

I suppose, if you're looking for 35 watts of class A power with a bit of room above that. . I'd be more interested in the big XPR's and what those would be like loafing along at a few percent of their rated output.

I dunno, that Class H power supply makes me nervous . . .

[josh358]

.

[satie]

I'll chime in here.

My 20.7’s are driven by  Krell 400e monos:  400 watts 8 ohm, 800 watts 4 ohm.  Both pairs of 3.7’s are driven by Emotiva XPA-1 monos:  500 watts 8 ohm, 1000 watts 4 ohm.  My one pair of 3.5’s are bi-amped with XPA-1 monos as well.  The tri-center is a CCR and a pair of MMC2’s each with their own XPA-1’s.  And lastly, my MGSS1 ‘s  are also driven by their XPA-1’s.  All in one home theater.

I am not too tempted with the new XPR-1 mono.  Double the power?  I think I have enough already.

Have you had a chance to compare the XPA 1 with the Krell?

Generally speaking, I have found most planar systems to be way underpowered so they could not render transient peaks realistically and had their bass bottom out because of the amp - well before the panels' bass went out. So I count myself as a big amp advocate. When well braced the big maggies can produce prodigious transients and enormous peak acoustic power in excess of 120 db. And they can do so into the bottom octave.

While I respect people's choice to keep their systems sotto voce, playing maggies with a SET, I don't get my kicks from ethereal beauty and tonally live images alone. It goes a long way, but keeps me just outside the music's emotional reach. For that to breach my "disbelief" and touch emotionally, I need the full dynamic envelope to come through. Particularly in the bass and to an extent in the deep bass.

To make use of the entire capacity of a braced big maggie, and to leave headroom beyond that, you want to either have really good 2kw/ch for the entire speaker or multiamp with that for the bass and something appropriate for the top end.  There is hardly anything that is going to sound good in the treble and mids while pumping out 1kw or more into  the bass. Since I believe nearly all commercial recordings have compressed deep bass, I tilt my Tympani's response up towards the deep bass using room modes and/or EQ. The band 25-40 hz is elevated 10 db above the midrange. To get that accomplished you need bracing and 2kw+ of power.

[Rclark]

^

excellent post and really cuts through it all. I too think underpowering these things is really selling yourself short. I know that the Ncores are bridgable to something like 1200 watts. If I ever move to a big panel or stat I could see myself taking that approach. In fact I would have to, I think Ncores are the only way I could get 1200 watts and a power bill that won't kill me. They're extremely efficient.
....

I dunno, that Class H power supply makes me nervous . . .

What makes you say that?

[kevin360]

While I respect people's choice to keep their systems sotto voce, playing maggies with a SET, I don't get my kicks from ethereal beauty and tonally live images alone.

Trust me; neither do I. It's voce alta in my listening room and I have no SET amp (now, if I had a pair of horns...). It's all about context. You have Tympanis. If I had Tympanis, I'd have massive power to drive them as well. I have 3.7s. I have driven them hard and full with fairly big power, but I prefer their sound when they aren't asked to reproduce deep bass. As my old amp indicated the draw on the power supply, I had visual evidence that it transitioned from busting its ass prior to the XO to loafing along after adding it. The massive bass engines I'm using put a smile on my face - I like deep, solid bass (music just doesn't work for me when that's missing). My 3.7s put a smile on my face - I have plenty of muscle to get them loud while delivering startling dynamics. It's all there and it's incredibly satisfying. I wouldn't lie to you and I'm not exaggerating - Scout's Honor.

[josh358]

What makes you say that?

Class H amps have a reputation for being problematic. Here's a thread that discusses some of the issues:

http://www.diyaudio.com/forums/solid-state/68415-class-h-amplifier.html

I haven't seen any reviews, or heard them myself, so of course I don't know, but I wonder what's to be gained by adding a circuit that could result in sonic compromise when few need that much power? Of course, someone who does need the power might justifiably decide otherwise -- or it may be that their implementation is so effective that there are no sonic compromises at all.

[srb]

Class H amps have a reputation for being problematic. Here's a thread that discusses some of the issues:
http://www.diyaudio.com/forums/solid-state/68415-class-h-amplifier.html

I am a little unclear on what exactly is going on with this Emotiva design.

According to Emotiva, the actual amplifier gain stage and output devices are biased as conventional Class A/B, but the power supply is described as Class H.

The power supply has a 2.5KVA transformer, a 240,000 uF capacitor bank and requires a 20 amp circuit.  It has all the ingredients of and sounds very much like a linear power supply, but there must be some power supply switching operation to be called Class H.

Doesn't seem to be any white paper or technical explanation of this, though, and I don't recall previously seeing a Class A/B amplifier combined with a switching power supply.

Steve