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Post by boomzilla on Oct 19, 2012 5:21:31 GMT -5
No, I don't mean that in the street sense (bad = good), I mean the amp just doesn't sound good! This amazes me, because with my low-impedance, low-sensitivity, difficult-to-drive Thiel 3.6 speakers, the XPA-2 was the closest thing to heaven.
So what speakers does the XPA-2 not like? Actually my 103 dB per one-watt Klipsch LaScalas! Apparently at power outputs of 1/10 of a watt or so (maybe less?) the XPA-2 just sounds FLAT. No dynamics, no bloom, no soundstage, just flat.
I'm speculating as to the cause of this. Perhaps the multiple output transistors of the XPA-2 (needed to supply the power that the XPA-2 develops) have switching imbalances at so low a signal level? Perhaps the transistors just aren't in perfect synch at so close to ground? Whatever the problem, my XPA-2 just doesn't sing with the LaScalas.
On the positive side, the XPA-2 still is dead quiet with the LaScalas - no hiss, no hum, etc. Once cranked up LOUDLY, the XPA-2 sounds significantly better with the LaScalas, but I can't listen that loudly for long.
So the decision that I'll have to make is: Do I keep my Thiels with the XPA-2, or do I sell both & keep the LaScalas? Any rational audiophile voice would probably council the former, but in my living room (with tube amplifiers), the LaScalas are killer! They may not be flat in frequency response, but they have life and dynamics that the Thiels can't touch (even with the superamp XPA-2).
Has anyone else had the same experience using an XPA-2 amp with high efficiency speakers?
Thanks - Boomzilla
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Post by mgbpuff on Oct 19, 2012 7:02:59 GMT -5
That's exactly why Class A type amps are recommended for extremely high efficiency speakers. Emotiva has two amps that have significant Class A capability, the XPA-1 and the XPA-1L, but these are very high power amps, probably way more than you need with LaScalas. Speakers are the most important component so if LaScalas please you, get an amp that they're compatable with. If you want ss, you might look at Nelson Pass's First Watt offerings.
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jamrock
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Post by jamrock on Oct 19, 2012 8:03:49 GMT -5
The gain of the XPA-2 is 32dB.
High gain amps can be very unforgiving
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Post by audiohead on Oct 19, 2012 8:06:42 GMT -5
jamrock..Very true about high gain amps,one of the draw backs on them.I wouldn't go as far as saying they sound bad.
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jlafrenz
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Post by jlafrenz on Oct 19, 2012 8:07:18 GMT -5
Have you tried different placements of your speakers? I had some issues with dynamics in my 2 channel room and tried multiple different amps and DAC's. I found the only thing that really made a difference was different speaker placements in my room.
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Post by Golden Ear on Oct 19, 2012 9:37:32 GMT -5
No, I don't mean that in the street sense (bad = good), I mean the amp just doesn't sound good! This amazes me, because with my low-impedance, low-sensitivity, difficult-to-drive Thiel 3.6 speakers, the XPA-2 was the closest thing to heaven. So what speakers does the XPA-2 not like? Actually my 103 dB per one-watt Klipsch LaScalas! Apparently at power outputs of 1/10 of a watt or so (maybe less?) the XPA-2 just sounds FLAT. No dynamics, no bloom, no soundstage, just flat. I'm speculating as to the cause of this. Perhaps the multiple output transistors of the XPA-2 (needed to supply the power that the XPA-2 develops) have switching imbalances at so low a signal level? Perhaps the transistors just aren't in perfect synch at so close to ground? Whatever the problem, my XPA-2 just doesn't sing with the LaScalas. On the positive side, the XPA-2 still is dead quiet with the LaScalas - no hiss, no hum, etc. Once cranked up LOUDLY, the XPA-2 sounds significantly better with the LaScalas, but I can't listen that loudly for long. So the decision that I'll have to make is: Do I keep my Thiels with the XPA-2, or do I sell both & keep the LaScalas? Any rational audiophile voice would probably council the former, but in my living room (with tube amplifiers), the LaScalas are killer! They may not be flat in frequency response, but they have life and dynamics that the Thiels can't touch (even with the superamp XPA-2). Has anyone else had the same experience using an XPA-2 amp with high efficiency speakers? Thanks - Boomzilla Proper matching component is critical achieving good sound. For instance, if you combine bright sound gear and bright sound speakers the combination wont be good. Prior to my emotiva amp, I find my polk lsi and marantz combination were too warm to my taste so having emotiva gear balance things out without sounding cold or warm. |
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Post by boomzilla on Oct 19, 2012 10:15:30 GMT -5
Yeah, Mr. Pass' amps would be the schizz, but they're HIGH ticket items... I've ordered a cheap Chinese 16.5 wpc hybrid integrated (tube front, single chip solid state output). The brand Qinpu A-6000 Mk. II has good buzz, but no solid reviews yet. Had I opted for an extra $200, I could have had the Jolida FX-10 (which IS highly reviewed by TAS magazine).
Ever the cheapskate, I decided to try the Qinpu first. If it sounds as good as my VTL compact 100 power amps, then I'm through shopping! Why didn't I just keep the VTL 100's? One of them has a leaky capacitor & blows its fuse periodically. The designer, one of the #&^%&)*(! Manleys, never published a schematic. Therefore any repair attempt involves extensive circuit analysis & testing of multiple components. Nobody locally works on tube amps, and I haven't the time or inclination to do it myself.
In the next month, I plan an "Audiophile Garage Sale" where I'll be unloading all my closets. Wish you were here...
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Post by Jim on Oct 19, 2012 10:17:45 GMT -5
Generally when I hear someone say that one set of speakers sound great with an amp, but another set sounds terrible - I generally suspect the speaker rather than the amp. The Audio Precision reports support how the amp behaves in low and high impedance. I am driving high sensitivity speakers with XPA-1s, and I'm sure there are lots of XPA-2 users with high sensitivity speakers. With that sensitivity, the XPA-2 is cruising along probably entirely in Class-A.
I'm not refuting your experience, but it makes me wonder about the crossover design and behavior of the LaScalas.
I'd be curious to hear your comments if you get a chance to hear any other high sensitivity speakers with an XPA-2.
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Post by Chuck Elliot on Oct 19, 2012 10:39:41 GMT -5
How old are your LaScalas?
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Post by boomzilla on Oct 19, 2012 10:45:27 GMT -5
How old are your LaScalas? Judging by the AL crossovers, somewhere in the mid 80's. The papers on the back are too faded to read anymore. I've ordered a type "A" crossover replacement from Mr. Crites, & look forward to hearing the speakers with fresh caps. I'm not saying that ALL high power amps would sound bad with the LaScalas, but only that my LaScalas profoundly sound flat with my XPA-2. I'm sure that the amp IS running in Class-A at that low a power output, but that obviously isn't helping. I know that the LaScalas are not the problem, because when I hook them up to my VTL Compact 100 monoblocks (tube), they sing. I know that the XPA-2 is good because when I hook it up to my Thiels, they sing! 'Tis truly a mysterie... |
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Post by paintedklown on Oct 19, 2012 10:53:22 GMT -5
Perhaps this is seriously a case of some not so great "synergy" between the speakers and amp.  I would lean toward the idea that Jamrock had regarding the high gain of the XPA-2. Great speakers, great amp, just not great together. It happens.  |
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Post by Chuck Elliot on Oct 19, 2012 10:59:01 GMT -5
The crossovers in the LaScala have a pretty wide impedance swing.
This is because the horns are attenuated via an autoformer. This causes the impedance of the horns to be multiplied back to the amplifier.
The above "could" be giving the amp a load it just doesn't like at low levels, but I would put my money on the new crossovers making a huge difference.
I would also replace the K77 tweeters with Bob Crites CT125s. They are a much better tweeter and I have a friend with LaScalas that this change made a huge difference with.
I don't have XPA amps rather UPA. My Klipsch just "sing" on Emotiva!
PS Why are you replacing the AL crossovers with A crossovers? The A is for the Klipschorn.
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xki
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Post by xki on Oct 19, 2012 11:03:34 GMT -5
How old are your LaScalas? Judging by the AL crossovers, somewhere in the mid 80's. The papers on the back are too faded to read anymore. I've ordered a type "A" crossover replacement from Mr. Crites, & look forward to hearing the speakers with fresh caps. I'm not saying that ALL high power amps would sound bad with the LaScalas, but only that my LaScalas profoundly sound flat with my XPA-2. I'm sure that the amp IS running in Class-A at that low a power output, but that obviously isn't helping. I know that the LaScalas are not the problem, because when I hook them up to my VTL Compact 100 monoblocks (tube), they sing. I know that the XPA-2 is good because when I hook it up to my Thiels, they sing! 'Tis truly a mysterie... I'm in the process of planning the switching out the cross overs and tweets on my 1972 La Scalas. Going with Crites but not the A or AA original replacements. I'm going with the A/4500. Bob Crites states that the cross overs from the 80's just aren't very good. Who am I to argue!  I know what you mean about 'flat' at lower levels. UPA2 driving the La Scallas. Once I'm in the 75-85 db range they just.... kick in. When these were new, lower SPL wasn't that much different in sound quality. I do know that my cross overs are old and decrepid. That's why I'm doing this change. I have no expectations but hoping there will be a big improvement. Many who have done this are very pleased. Mine being 40+ years old, I think I'll see a difference. |
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Post by xki on Oct 19, 2012 11:06:22 GMT -5
I would also replace the K77 tweeters with Bob Crites CT125s. They are a much better tweeter and I have a friend with LaScalas that this change made a huge difference with. Yes! Their response is all the way up to 20KHz as opposed to the K77 limit of 17KHz. |
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Post by Chuck Elliot on Oct 19, 2012 11:15:35 GMT -5
I also offer these for your consideration: www.alkeng.com/ap_xo.htmlThe ALK crossovers have a "swamping" resistor on the autoformer that prevents the wide impedance swing. |
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sorbe
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Post by sorbe on Oct 19, 2012 11:21:53 GMT -5
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bootman
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Post by bootman on Oct 19, 2012 12:16:19 GMT -5
If XPA2 + thiel = good and XPA2 + Klipsch = bad Logic tells me Klipsch = bad, no?  |
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jamrock
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Post by jamrock on Oct 19, 2012 12:24:08 GMT -5
If XPA2 + thiel = good and XPA2 + Klipsch = bad Logic tells me Klipsch = bad, no? That would be the logical conclusion. However, the OP made a subjective evaluation. Nothing objective offered. (The XPA-2 was not clipping or the FR showed a great bump or dip at a particular frequency, etc). So, maybe, the "expected difference" in the sound due to the change of speakers is being interpreted as bad. But in general, it definitely seems that the speaker is the culprit. |
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Post by boomzilla on Oct 19, 2012 12:47:25 GMT -5
No, the Klipsch speakers are NOT bad. They ARE "different." I doubt that the XPA-2 cares about the crossover or phase angles of the La Scalas - it was completely oblivious to the strange crossovers & phase angles in the Thiels, which are some of the WORST for amps.
I am also leaving my original Klipsch tweeters in the boxes (despite the fact that they measure less-extended than Mr. Crites' CT-125s). In my room, I like the sound of the K-77 originals.
The Crites "A" crossovers can work in K-horn, La Scala, or the Belle equally well provided you're not playing the speakers as sound-reinforcement units. The "A" crossovers don't have the zener diode for tweeter protection that the more expensive crossovers have, but they are reputed to sound sweeter.
Mr. Jamrock hit the nail on the head - I've made NO measurements of the combos that I'm reporting on here - only the feedback from mine own ears. My conclusion is firm, though. The XPA-2 just doesn't "work" with my La Scalas.
I'll further agree strongly with Mr. Sorbe - The XPA-2 is CLEARLY a more accurate amplifier and doesn't add the second order harmonics that the La Scalas seem to like so much. The VTL compact 100 tube power amplifiers that the La Scalas do like is not as "euphonic" as many tube components, but it undoubtedly has some "tube bloom."
The main difference between the XPA-2 and the VTLs (with the La Scalas), however, is not tube bloom or its lack. It is instead the vastly different DYNAMICS at the very low power outputs. The VTLs sound punchy & dynamic with wide range from the most quiet to the loudest sounds. The XPA-2 compresses that dynamic range and sounds as if a compressor has been inserted that raises the volume of the quietest sounds and lowers the volume of the loudest sounds.
The XPA-2 does NOT do this with the less-efficient Thiel speakers - only with the La Scalas. Average listening level = 80 to 85 dBA in the living room.
Finally, as Mr. PaintedKlown says, all of these components are great - just not together.
Cheers - Boom
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Post by sharkman on Oct 19, 2012 12:52:15 GMT -5
Do you guys know how many people in this forum have and love Klipsch with XPA amps?
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