XPA-1 or 2 XPA-2's Bridged for 802's

[bigmak]

I am trying to get amps for my B&W N802's. I presently have one XPA-1, but am having trouble finding another single. I am thinking about buying either new XPA-1's or XPA-2's and bridging them. My family room opens to the kitchen, with a lot of windows and tile floor, with a rug. It is my main area, so about 75% HT and the remaining time I like it loud and rowdy. To my question: I could save about $500 by going with XPA-2 and bridging them over the XPA-1. What will I gain and what would I lose?

[garbulky]

xpa1

[garbulky]

The Nautilus is 8 ohms I believe? But it does go down to 3.5 ohms I think. The XPA-2 bridged is rated for 8 ohms only. Anyway, dependingo n the model of the XPA-1 you get...the gen 2 which I have has 60 watts of class A, which I think is worth going for. The XPA-2 is built using a lot of the same components as the XPA-1 but it's not the same amp. Especially at the quality of speakers you have, it is not worth compromising imo. You get fully balanced, true monoblock stable to 2 ohms, and class A architecture.

[bigmak]

Thanks, garbulky. I didn't realize XPA-2's would not be able to handle going below 8 ohms. That makes it a very easy decision. Now i have to decide whether to wait around for another XPA-1 gen 1 to go for sale or purchase the new XPA-1 gen 2 and sell the older single XPA-1 gen 1 amp. Is it possible to use the gen 1 amp with a gen 2 amp? I imagine that will not work due to the different output structure of the two amps. At least worth asking thew question.

[qdtjni]

Nov 24, 2016 13:23:47 GMT -5 bigmak said:

Thanks, garbulky. I didn't realize XPA-2's would not be able to handle going below 8 ohms. That makes it a very easy decision. Now i have to decide whether to wait around for another XPA-1 gen 1 to go for sale or purchase the new XPA-1 gen 2 and sell the older single XPA-1 gen 1 amp. Is it possible to use the gen 1 amp with a gen 2 amp? I imagine that will not work due to the different output structure of the two amps. At least worth asking thew question.

You could use your old XPA-1 G1 with a new XPA1 G2
but it would be far from ideal and your speakers deserve better.

[Gary Cook]

As an experiment I'd really like someone to try an XPA-1 Gen1 on one channel and an XPA-1 Gen2 on the other, flick the switch to mono and see if any real world differences can be heard. A review post would be very interesting to read, by a lot of people I expect. If there is a difference, the Gen2 is noticeably superior and the difference justifies the cost then the path is clear.

BTW I would never sell a XPA-1, there is always a use for a top shelf monoblock, for example driving a centre speaker or a sub woofer.

Cheers
Gsry

[garbulky]

Nov 24, 2016 13:23:47 GMT -5 bigmak said:

Thanks, garbulky. I didn't realize XPA-2's would not be able to handle going below 8 ohms. That makes it a very easy decision. Now i have to decide whether to wait around for another XPA-1 gen 1 to go for sale or purchase the new XPA-1 gen 2 and sell the older single XPA-1 gen 1 amp. Is it possible to use the gen 1 amp with a gen 2 amp? I imagine that will not work due to the different output structure of the two amps. At least worth asking thew question.

gen 1 XPA-1 32 db gain. gen 2 29 db gain. So there is a mismatch. Not insurmountable though.

The main difference is the class A circuitry. You can switch back and forth from class AB (similar to the XPA-1 gen 1) and the class A. The class A improvement is subtle but it does sound more enveloping.cohesive and brings that nth degree of improvement which to me is worth it. I've heard the XPR-1, 2, XPA-1, 2, 5, UPA-1, 2, 500, Mini-x and XPA-1 L. The XPA-1 gen 2 is the best amp they've got.

BUT....you have to have other parts of your system and setup working well together to provide reasonable resolution for the class A difference to become noticeable. S it's not guaranteed you'll hear them. Just that imo the difference is there.

[PoloOle]

XPA-1 G1 for sale.

emotivalounge.proboards.com/thread/48642

[vneal]

XPA 1

a great speaker deserves a great amp or in this case a two great mono amps

there is a single one available here for 550$

[leonski]

I've NEVER heard anyone say a bridged amp sounded better than the Un-Bridged version.

Measurement panel from the Stereophile road test of the 802 D, which is the 'diamond', I guess?

www.stereophile.com/content/bw-802d-loudspeaker-measurements#h27rHudzAPJ6ildv.97

a 'moderately' difficult load due to impedance drop to 3 ohms AND 4ohms/ -50 degrees at a critical 60hz.
I would NOT expect any bridged amp but the Most Elite to stand a chance, especially at higher levels.

Sensitivity was a very good 89db 1watt@1meter, which overall makes GOOD use of available amp power.


All the above is preamble to thinking that if 'ya GOTTA go with EMO, the XPA-1 is the obvious way to go.

Unless you can find a pair of Parasound JC-1s for the same money. Never gonna' happen!

One Possibility NOBODY mentioned:    SELL the G1 XPA-1 and buy a PAIR of the G2.      Best outcome, IMO, without going to the Parasound Solution.

[bigmak]

Hope everyone had a great Thanksgiving. Thank you all for the great feedback. The single XPA-1 for sale on this site is mine. I thought I would put it up and see if there was any interest. I am probably going to order (2) new XPA-1's while they are on sale. I will probably keep it for a center, which I have an older Polk CSi40, that has served me well for many years but might look at replacing. Garbulky you make a very good point when you said, "BUT....you have to have other parts of your system and setup working well together to provide reasonable resolution for the class A difference to become noticeable." I looked at the link that leonski provided the 802's and it's Greek to me. I have made very few changes to my receiver because I am unsure what changes to make and how one change affects another setting. I am sure that I can tune they system, but not sure where to start. I feel I am building a mystery. This is turning out to be one of those hobbies that you need to do with a friend that can see and listen to your system and help make it the best it can be. Thanks again for all your input.

[novisnick]

bigmak , thanks for the well wishes, I hope you had a blessed Thanksgiving also.
It is great having someone to help and share your system with but remember this, the only ears you HAVE to satisfy are your own. If you don't like how it sounds then know one could ever convince you that it sounds great.
We here on the forum will be more then happy to help you on your journey of sound appreciation and council you where we can. Audio Nirvana is just over the horizon,,,,,ha,,,,ha,,,,,ha,,,,,  

[leonski]

Nov 25, 2016 11:24:47 GMT -5 bigmak said:

Hope everyone had a great Thanksgiving. Thank you all for the great feedback. The single XPA-1 for sale on this site is mine. I thought I would put it up and see if there was any interest. I am probably going to order (2) new XPA-1's while they are on sale. I will probably keep it for a center, which I have an older Polk CSi40, that has served me well for many years but might look at replacing. Garbulky you make a very good point when you said, "BUT....you have to have other parts of your system and setup working well together to provide reasonable resolution for the class A difference to become noticeable." I looked at the link that leonski provided the 802's and it's Greek to me. I have made very few changes to my receiver because I am unsure what changes to make and how one change affects another setting. I am sure that I can tune they system, but not sure where to start. I feel I am building a mystery. This is turning out to be one of those hobbies that you need to do with a friend that can see and listen to your system and help make it the best it can be. Thanks again for all your input.

Eyes CLOSED, you'll NEVER know when it goes from 'A' to 'A/B'.    It is NOT a brick wall.    It is a 'sliding scale' in which output transistor BIAS is the key measure.

During very Loud peaks, you'll be out of 'A'.    But to run the amp ALWAYS out of 'A'?    Do you have ANY idea how loud that'd be?  With a CLAIMED 60 watts in 'A', you'd be EVICTED from your TOWN at that level.  With the output devices conducting ALL the time, you also consume LOTS of power just sitting, warming the room.  As an experiment, I'd recommend getting a Kill-A-Watt meter and take a reading with amp at idle or at a VERY low level.  Currrent thru an 'A' amp is CONSTANT since it is dumped to ground OR the speak (load).   Only as you 'transition' to A/B does this change.
The XPA-1 is most properly called a 'high bias' A/B design.  Pass has made GOOD use of this design idea.   His XA30.5 puts out 30 watts in class 'a'.   But, over 6db dynamic headroom at 1% distortion.  That's a 30watt amp putting out OVER 120watts at clipping.     Most people with a pair of these NEVER or certainly Rarely get out of 'A'.
The Pass amp is a MONObloc and SHIPS at about 75lb for a 30watt amp.  That should give you SOME idea of how much heat sink it takes to support such a topology.  

With the kind of power you have on tap with the XPA-1, the biggest hazard, IMO, since you like it 'loud and rowdy', is to keep from burning a tweeter.  The HF driver is the most vulnerable.    And requires the LEAST power.  Be sensitive to distortion and turn it down if you hear any.  

[ronwickens]

gen 1 has higher gain than gen2 your better off having both monos the same generation

[leonski]

Nov 24, 2016 13:23:47 GMT -5 bigmak said:

Thanks, garbulky. I didn't realize XPA-2's would not be able to handle going below 8 ohms. That makes it a very easy decision. Now i have to decide whether to wait around for another XPA-1 gen 1 to go for sale or purchase the new XPA-1 gen 2 and sell the older single XPA-1 gen 1 amp. Is it possible to use the gen 1 amp with a gen 2 amp? I imagine that will not work due to the different output structure of the two amps. At least worth asking thew question.

BRIDGED XPA-2.      Unbridged, which IMO is the only way to use the amp, is good to a solid 4 ohms with some parts of the impedance curve below 3 ohms.      I've heard 2.7 bandied about.

You have another problem with B&W speakers which is that some models are very reactive and while of reasonable sensitivity, actually make poor use of amp power.   
Speakers that look much like a capacitor or inductor to the partnering amp can reveal substandard amps.    Even some 'big name' amps don't like such treatment.

Bridging an amp will just make the reactance situaion worse.       

'output structure'?    You are really mostly worried about the GAIN.    If the gain is the same, you are probably OK.    Gains differing by 3db or more will require other adjustments.   And maybe on an ongoing basis
as you adjust the main level up or down.   

I've seen on these forums by some persons who actually measured the amp, that the XPA=1 in 'A' will IDLE at over 300 watts. EACH.   And put out THAT MUCH in heat, since it's not doing anything but sitting there.   Running up your electric bill.    In Winter?    Nice.     In Summer with the AC already laboring?    Not so nice.