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Post by rcheliguy on Jun 18, 2015 12:20:04 GMT -5
By the end of the year... It will be interesting to see how it goes.
The THD and IMD on Class D amps is typically amazing, as is their efficiency and there is no switching like an A/B amp.
Then again there is switching in a way just at an extremely high frequency.
Hopefully their Class D amps will do like some others I've seen that don't clip and will round off the wave forms if it goes past the power it is capable off.
What they are doing is "effectively" using software to model the output to be more like a tube amplifier when it goes above a certain value.
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Post by leonski on Jun 24, 2015 2:15:07 GMT -5
Many current manufactures, among them NAD and others are using Hypex N-Core technology in a license deal.
I wouldn't get TOO caught up in D amps 'specs'. All of 'em that I know of are severely limited to time at maximum power Cooling is an issue at max power. Also, there are 2 major topologies of output. Bridge and HalfBridge. Some are switchable for 'bridging' purposes, which is cool.
I owned a 'd' amp for several years and eventually sold it for a conventional A/B amp. There was SOMETHING not quite right in the high frequencies. Some of it may have been due to the phase shift caused by the output filter.
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Post by leonski on Jun 24, 2015 2:28:50 GMT -5
One of the BIG myths of 'd' amps is the 'high efficiency'. Using the B&O ASP series modules as an example, they are about 83% efficient AT FULL POWER from Plug to Speaker. Measuring JUST the output stage, the number goes UP. But at more reasonable power output levels, the efficiency is much lower, down around typical A/B numbers. Maybe 50 to 60% or so. High, but not as quoted by most. Most D amps will NOT pass the Stereophile 1/3 power for 60 minutes 'preconditioning' test prior to measurements. Insufficient heat sinking.
And Europe already has LOTS of wacky rules about stuff like Wall Warts and power supplies in general. They are very concerned with Power Factor and other issues American's havent' yet been made aware of.
And Yes, a 'd' amp with a SMPS really CAN become a source of interference. My Plasma TV, however puts out FAR MORE than my 'd' amp ever did. I would use my ShortWave receiver which I could tune to the switch frequency of my amps and they were not detectible. The TV? A monster up to 25 feet away. During a SoCal power failure in '14, (maybe '13?) it was so electrically quiet I sat up all nite with my SW radio and litened to stuff I coudn't get otherwise.
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Post by audiobill on Jun 24, 2015 7:20:49 GMT -5
By the end of the year... It will be interesting to see how it goes. The THD and IMD on Class D amps is typically amazing, as is their efficiency and there is no switching like an A/B amp. Then again there is switching in a way just at an extremely high frequency. Hopefully their Class D amps will do like some others I've seen that don't clip and will round off the wave forms if it goes past the power it is capable off. What they are doing is "effectively" using software to model the output to be more like a tube amplifier when it goes above a certain value. All that trouble , just get a tube amp!!
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Post by rcheliguy on Jun 24, 2015 7:47:34 GMT -5
Many current manufactures, among them NAD and others are using Hypex N-Core technology in a license deal. I wouldn't get TOO caught up in D amps 'specs'. All of 'em that I know of are severely limited to time at maximum power Cooling is an issue at max power. Also, there are 2 major topologies of output. Bridge and HalfBridge. Some are switchable for 'bridging' purposes, which is cool. I owned a 'd' amp for several years and eventually sold it for a conventional A/B amp. There was SOMETHING not quite right in the high frequencies. Some of it may have been due to the phase shift caused by the output filter. I don't think that they are quite done yet. There is an issue with some "around" 19kHz that is dependent on their operating frequency. I understand that they have increased their operating frequency quite a bit to improve that, but that is also pushing them higher into RF. I'm quite happy with the sound I'm getting from my XPA-2 and won't jump ship instantly. I'm very curious about the issues you raised about their efficiency running them at lower volume levels. There is obviously more to learn and I'm not intending to jump without doing my research. Thanks for the info.
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Post by rcheliguy on Jun 24, 2015 7:49:38 GMT -5
All that trouble , just get a tube amp!! Funny! To my mind soft clipping is the only real advantage of a tube amp. Everything else is downside. I'm looking for the cake and eat it situation. We aren't there yet, but technology will improve.
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Post by pedrocols on Jun 24, 2015 8:13:51 GMT -5
All that trouble , just get a tube amp!! Funny! To my mind soft clipping is the only real advantage of a tube amp. Everything else is downside. I'm looking for the cake and eat it situation. We aren't there yet, but technology will improve. Don't believe your mind and trust your ears....
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Post by audiobill on Jun 24, 2015 8:21:34 GMT -5
Sonics are the only thing that matters......the rest is irrelevant IMO.
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Post by rcheliguy on Jun 24, 2015 9:03:03 GMT -5
Funny! To my mind soft clipping is the only real advantage of a tube amp. Everything else is downside. I'm looking for the cake and eat it situation. We aren't there yet, but technology will improve. Don't believe your mind and trust your ears.... The problem is that your ears report to your mind and your mind clouds reality quite a bit about almost every sensory input that you have. In an identical room with identical equipment playing identical source material you can hear different things on different days depending on your mood or whether you just heard about some cool new device that makes you suddenly feel what you are hearing is lacking something.
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Post by pedrocols on Jun 24, 2015 9:15:51 GMT -5
Don't believe your mind and trust your ears.... The problem is that your ears report to your mind and your mind clouds reality quite a bit about almost every sensory input that you have. In an identical room with identical equipment playing identical source material you can hear different things on different days depending on your mood or whether you just heard about some cool new device that makes you suddenly feel what you are hearing is lacking something. Precisely! However, oscilloscopes can only measure and your ears can (subjectively) hear. At the end of the day what matters is what you hear and not what the oscilloscope measures...Some people can't hear pass 14khz and yet they obsess about buying a speaker that measures flat all the way up to 25khz. Go figure...
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Post by rcheliguy on Jun 24, 2015 14:07:07 GMT -5
The problem is that your ears report to your mind and your mind clouds reality quite a bit about almost every sensory input that you have. In an identical room with identical equipment playing identical source material you can hear different things on different days depending on your mood or whether you just heard about some cool new device that makes you suddenly feel what you are hearing is lacking something. Precisely! However, oscilloscopes can only measure and your ears can (subjectively) hear. At the end of the day what matters is what you hear and not what the oscilloscope measures...Some people can't hear pass 14khz and yet they obsess about buying a speaker that measures flat all the way up to 25khz. Go figure... Agreed about people obsessing over statistics. Right now I am really happy with how my stereo sounds. However it's been suggested that I run frequency response tests in my listening room. There is part of me that is curious, but a more pragmatic side of me thinks if I'm already happy do I really want to go down that path? Once I see any type of issue It will probably bother me until I do something about it. I know that there are some areas in my listening room that are way off, but in the sweet spot it seems very right to me. The imaging is crystal clear and I can't hear anything that sounds like too much or too little to me. I went through the Phillips Golden ears listening test just for grins and I think I have a pretty good grip on what I should be hearing. I've also listened to many systems over the years, but not many recently ( read in the last decade ).
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Post by audiobill on Jun 24, 2015 15:02:26 GMT -5
It's sensory satisfaction, not a science project!!
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KeithL
Administrator
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Post by KeithL on Jun 24, 2015 15:56:43 GMT -5
The problem with that sentiment is that you CANNOT separate your mind from your ears. In fact, you do not hear with your ears; you hear with your mind! Your ears take in data, which is then processed by your mind, but the "you" somewhere inside is getting its information from your mind. Therefore, you cannot avoid having that information filtered, adjusted, and interpreted by your mind. It is, as they say, "all in your mind". If you're really serious and find soft clipping to be the ONLY advantage of tubes, then wouldn't it be easier to simply buy an amplifier powerful enough that it never clips at all? I suggest that, if you were to compare our XPA-2 to a stereo tube amp of similar or lower price, the tube amp would be far into hard clipping before the XPA-2 was clipping at all (hard, soft, or otherwise). (I kind of suspect that there must be something else you like about them... ) Funny! To my mind soft clipping is the only real advantage of a tube amp. Everything else is downside. I'm looking for the cake and eat it situation. We aren't there yet, but technology will improve. Don't believe your mind and trust your ears....
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KeithL
Administrator
Posts: 9,929
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Post by KeithL on Jun 24, 2015 16:08:27 GMT -5
I would agree that you really should avoid getting caught up in the specs of Class D amps..... Many early Class D designs were overly obsessed with efficiency - and with delivering very compact and light weight devices. Because of this, many of them had virtually no heat sinks, which did indeed mean that some of them had heat problems running at full load. (An amplifier putting out 1000 watts at 90% efficiency will still make more heat than one putting out 150 watts at 75% efficiency.) Bridge and half-bridge refer to how the output devices are arranged. Other factors, including the switching frequency, and the switching speed of the output devices themselves, will have a much greater impact on efficiency. Overall, the performance of Class D amps has been improved a lot in the last few years - to the point where there are several available that can potentially meet our requirements in terms of cost and sound quality. You will definitely be seeing a few turning up in our product line sometime soon.... but you'll have to wait a while to see exactly where.... Many current manufactures, among them NAD and others are using Hypex N-Core technology in a license deal. I wouldn't get TOO caught up in D amps 'specs'. All of 'em that I know of are severely limited to time at maximum power Cooling is an issue at max power. Also, there are 2 major topologies of output. Bridge and HalfBridge. Some are switchable for 'bridging' purposes, which is cool. I owned a 'd' amp for several years and eventually sold it for a conventional A/B amp. There was SOMETHING not quite right in the high frequencies. Some of it may have been due to the phase shift caused by the output filter. I don't think that they are quite done yet. There is an issue with some "around" 19kHz that is dependent on their operating frequency. I understand that they have increased their operating frequency quite a bit to improve that, but that is also pushing them higher into RF. I'm quite happy with the sound I'm getting from my XPA-2 and won't jump ship instantly. I'm very curious about the issues you raised about their efficiency running them at lower volume levels. There is obviously more to learn and I'm not intending to jump without doing my research. Thanks for the info.
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Post by rcheliguy on Jun 24, 2015 21:29:57 GMT -5
If you're really serious and find soft clipping to be the ONLY advantage of tubes, then wouldn't it be easier to simply buy an amplifier powerful enough that it never clips at all? I suggest that, if you were to compare our XPA-2 to a stereo tube amp of similar or lower price, the tube amp would be far into hard clipping before the XPA-2 was clipping at all (hard, soft, or otherwise). (I kind of suspect that there must be something else you like about them... ) I've not noticed any clipping I can hear with the XPA-2. My speakers are rated at 92dB at 1W and I've had it as loud as I can stand, so I think I'm covered. Honestly I'm not a tube fan and I was dead serious about their soft clipping being the only advantage that I think they have. My solid state A/B amp gives me silky vocals and everything sounds great.
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Post by leonski on Jun 25, 2015 0:38:11 GMT -5
Yes, no question about it. 'D' amps have improved LOTS. My IR development board sounds OK, but not as good as my old ASP moduled PSAudio integrated and certainly not nearly as good as my new A/B amps. A friend had some ASC module mono blocs from Bel Canto which sounded FINE as part of a biamp setup on his panels. Here, for a good case of Brain Burn is a link to the ASP module specs. Look at it a line at a time. Check out time / frequency limits. Phase shift was an issue as impedance dropped and frequency passed maybe 16khz or so. This module also has an ON BOARD switching PS. Each module can power lower power rated modules from an on-board DC bus. Good feature for bi/tri amped speakers. If you want 'soft clipping', some NAD of old had a switch for just that feature. www.icepower.bang-olufsen.com/files/solutions/icepower500aspdata.pdfThis is the datasheet for the MIDDLE of 3 power rated amps. Bel Canto sold a BUNCH of the 1000watt version. Keep in mind that 2 or 3 NEWER generations of amp are available, but also don't forget physical limits.
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Post by rcheliguy on Jun 25, 2015 7:35:48 GMT -5
For the record I'm not having any issues with clipping that I can hear.
It just seemed like a nice feature.
In addition my XPA-2 runs pretty cool. It sits inside a cabinet, but there are two 2.5" holes underneath it, and 6" clearance above it and to either side. The back is completely open. Convection seems to be handling this pretty well.
So far the XPA-2 is doing a great job.
I know a guy who is also using an OPPO 105 and ML Ethos speakers, but he has a $4K Macintouch Preamp and a $6K Macintosh amp in between. I'd love to do a blind A/B test between the two systems.
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Post by pedrocols on Jun 25, 2015 7:48:12 GMT -5
If you guys are corcern about wether you will potentially have any clipping issues, I would suggest you assess and evaluate your listening habits. I run a pair of Magnepan 1.7 speakers with a pair of 125wpc tube amps and I have zero concerns about clipping my amps. Be mindfull that Magnepan speakers are not allegedly the most easy speakers to drive.
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Post by leonski on Jun 25, 2015 10:53:29 GMT -5
Pedrocols: Maggies are a mixed bag. No QUESTIKON that they are Very Low sensitivity. So the do make use of as much power as you are willing to buy. But it's also true that in general, they are NOT a 'bad load' since they are also very low reactance. That is, when measured, the speaker looks a Lot like a simple resistor, not a capacitor or inductor. And while this does vary as a function of frequency, the AMOUNT of deviation from pure resistive is not that much. So in the sense of reactance (stored energy) maggies are a fairly EASY load. That's one reason that Maggies make reasonable use of ANY good amp, be it Tube OR SS. As kind of an aside, it appears that one measure, that of Damping Factor is also of minimal importance.
Highly reactive speakers with HUGE shifts in both phase and impedance are the 'enemy' here. Speakers like that can be very difficult to drive, even if of moderate sensitivity. Look at Any speaker for which Stereophile took data. The impedance / phase curve will pretty much tell you all you need to know in this one regard. How it sounds? Another matter altogether.
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Post by rcheliguy on Jul 4, 2015 11:18:04 GMT -5
Out of sheer curiosity I finally broke down and ordered an ECM 8000 and a Scarlet 2i2 to do some room measurements. I think my system sounds great already, but I also realize that the largest improvements I could possibly make at this point would be to the room's acoustics, so I'm going to check that out for a little bit. If I don't see anything noticeably off, I don't intend to do anything. I've looked at the phase and impedance vs. frequency graphs of a lot of speakers. The only speakers that seem to have close to even phase response from 20-20 have lots and lots of drivers and crossovers tweaking the phase alignment, but I have to seriously wonder what other artifacts are introduced by matching all of those drivers and using such a high number of analog components that can drift over time. In the case of my Ethos speakers which have a single cross over at 380Hz, the key is whether each instrument or voice you are listening to has enough range to move very far along this phase non-linearity. Vocals are in a narrow enough band that they sound in phase. Most instruments are the same. As long as the whole cohesive sound comes from a similar phase the stereo imaging should sound intact and not be something upset by the frequency specific phase differences. So far I haven't heard anything surprising in the sound stage. That said I'm curious what the frequency response of my room looks like in the sweet spot and one butt width to either side
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