AudioNervosa
Systemic Development => Amplification and Preamplification => Topic started by: rollo on June 09, 2011, 08:25:33 AM
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Yesterday I was fortunate to hear Analysis Omega speakers driven by Analysis Arion Class "D" Hybrid Monoblocks. Using a 6H30 tube and NO "Ice Chip". My Lector 7TL CDP as the transport feeding a Weiss DAC. The preamp a tubed kit [ to be announced] was IMO the most realistic presentation of home reproduced music I have EVER heard. No tube sound no SS sound just the real deal.
The initial seesion used generic PCs for the amps and a homebrew PC for the Lector and a Digital PC from PI audio. Sounded really good with no issues. Inserting the Triode Wire Labs PCs at the amps improved every parameter of the sound. Clarity and bass improved dramatically. Added punch and a larger soundstage were quite obvious. The presence and weight of the presentation was as close to real, no darn it it was real.
The Omega speakers crossovers were reworked with superior parts and the difference between the original and revised was just night and day. The revised crossover yielded even more clarity and an overall sense of realism. We were not prepared for the improvement the crossover made.
The final kicker which truly tied it all together was installing the PI Audio Rev B power conditioner. Can only imagine how an Uberbuss from PI audio would improve the sound further. I cannot fathom an improvement but PI audios products appear to do just that.
To date I have heard the Omega speakers numerous times with Lamm gear, Joule Electra, Arion, Dehavlland GM70,and other SS amps.
The Lamm gear has an edge however the Arion hybrid is really close. I could easily live with the Arion as the Lamm gear is a stretch of the budget. A big stretch.
Thee were some interesting footers being used. A materials Scientist created footers using a rod of three sizes sitting on a cradle. They appear to be some Nylon composite but that is a guess. we took home three pairs which I installed two pairs under the CDP and Preamp. They are not going back. The midbass was clearly defined as never before in my system. Never! Again added weight and presence were there in spades. Improved focus and clarity. They are called "Pon -Tunes and list for $179 for three pieces [ one component]. Club members $100.
Yesterday was an eye opening experience for me. The top to bottom coherence weight and presence was unlike any Ribbon speaker I have heard anywhere anytime. If you have the scratch these are a must hear.
charles
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Charles - sounds like you had an audiophile's vision of a perfect day yesterday!
I totally agree about the Triode Wire Labs PCs. I replaced every PC in my system with Pete's cords and couldn't be happier!
Tell us more about the "Pon-Tunes"... who's selling them?
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(http://www.analysisaudio.com/Avmentor/arion_audio_mk1000_0.jpg)
http://www.analysisaudio.com/Arion.php
Pon-Tunes made by Arion Audio also. Arion is a division of Analysis Audio. Mike Kallelis, super nice guy. http://www.audiophileoutletstore.com/Arion-Audio-NEW-Pon-Tunes-Vibration-Control-Syste-p/ara-pt.htm
I'm glad they are making their own amps. I have never been totally enthralled with the Analysis panel demos I've seen using various amps. The worst was Joule Elektra, the best was Spectron, also VTL and Behold. Meh. Class D is great for the impedance and current requirements, and will give a much needed edge to the panel's slightly polite sound. I thought I wanted a touch more edge even with Spectron on Omegas, but you can't judge too much at a show. I see they have a tube preamp too.
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Yes a trip it was. A learning experience. The Deuland resistors in the crossover made such a difference. The Arion chip amp was a huge surprise. JPS internal wiring in the crossovers as well throughout the system also a major improvement. Pon-tune footers under all the gear improved the sound.
I learned my CDP was improved by the Weiss DAC :( . Finally I need to buy a Lotto ticket.
charles
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.... Inserting the Triode Wire Labs PCs at the amps improved every parameter of the sound. Clarity and bass improved dramatically. Added punch and a larger soundstage were quite obvious. The presence and weight of the presentation was as close to real, no darn it it was real....
This shouldn't surprise any of us anymore - Pete is the MAN. :thumb:
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Apparently a digital, not a chip amp (I own both).
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Apparently a digital, not a chip amp (I own both).
Thanks for the clarification. Class D it is. Elaborate on the differences you have noticed between the two please. This is new terrortory for this old fart.
charles
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A chip amp is a self contained amplifier on a single integrated circuit, like this:
(http://solderslingers.com/cart/images/lm3875tf.jpg)
You just supply power, heatsink, signals in and out and you have tunes. They are cheap and high quality sound. They are intended for car audio, and low priced consumer products like $129 receivers. These days you see them in $400 receivers. But the newer generation chips are excellent quality.
Chip amps can be linear class AB, or they can be class D, like those made by Tripath.
(http://image.dhgate.com/upload/spider/e/111/096/e_bfhalv096111_0.jpg)
See it is still an integrated circuit, an amp on a chip.
Chip being the slang for a single small square piece of silicon cut from a round silicon wafer with all the discreet components printed right onto the silicon. Resistors, conductors, transistors, caps? all formed onto the silicon. Then the silicon chip is installed in a plastic jacket and connected to the pins with small copper/gold wires. http://en.wikipedia.org/wiki/Integrated_circuit
(http://sivasankarivlsi.files.wordpress.com/2011/04/silicon-wafer.jpg)
See the separate chips formed on the big round wafer. The chips will be cut from the wafer with a diamond saw and assembled into the package. The wafer is about 7" across. These are probably microprocessor chips with millions of discreet parts printed on each square.
I think there are some other classD integrated circuits now besides Tripath, but they were the first. Tripath is out of business now.
The opposite of integrated circuit is a discreet circuit. That means that it is built out of discreet parts instead of all the parts printed together on one piece of silicon. Discreet parts are what you normally think of as resistor or cap, or transistor. In a discreet transistor there is still a piece of silicon inside the package, connected to the pins with wires. But there is only one, and usually nothing else. There are some transistor products that have temp sensors and other cool goodies in there now.
Most class D amplifiers are discreet. This allows using much more powerful transistors and getting much more output power than an IC. A discreet class D amp looks like this:
(http://www.rumoh.nl/2807-1788-large/hypex-ucd700hg.jpg)
You can see the discreet transistors bolted to the blue heat sink. There is an opamp input stage, which is an IC, but the output stage is discreet. This bad boy makes 700W into 4ohms, using only 3 pairs of small plastic transistors, with the lowest output impedance of any amp topology, <.001 ohm. And it fits in the palm of your hand.
The last thing is that a class D amp is not a digital amp. It is an analog switching amp. It pulses current into an inductor based on the comparison of the input and output signals. If the output voltage is too low it gives a few pulse of "ON" to catch up. Class D amps are literally a big feedback loop on steroids. A digital amplifier is one that accepts a streaming digital audio signal on it's input, and the DAC is actually the output stage of the amplifier. You can see this topology in Tact amplifiers and the new NAD M2 "direct digital" amplifier, aka power dacs. I wonder if the little Wadia iPod doc power amp is a direct digital amp? Most of the digital amps we talk about these days are class D, analog switching amplifiers. Digital Amp Company, Bel Canto, W4S, B&O modules, Hypex, Spectron, Nuforce, Tripath, etc. They take an analog signal in and spit out an analog signal. the signal is never converted to logic bits. You can picture it as the input signal is being redrawn by the output stage using dots not a smooth line, using ~500,000 dots per second. Then the dots are followed by an analog filter (always with an inductor) which connects the dots. The output filter is what makes or breaks the class D amp, how smoothly can the dots be reconnected. This is Red Wine's success with Tripath chips, Vinnie found a nice recipe for output filter.
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A chip amp is a self contained amplifier on a single integrated circuit....
As usual, Rich. You are a wealth of information! :thumb:
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Rich that was a great plain English explanation of Chip and class D amps.
For those that want a little more in depth discussion about amplifier Classes the following Wikipedia article explains not only Class D, but also Class A (including SET), Class AB Push-Pull and all of the other amplifier categories.
http://en.wikipedia.org/wiki/Class_A_amplifier#Single-ended_and_triode_class_A_amplifiers
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Charles,
Both my chip amp (VMB-1, 40 watt monoblocks) and digital (D-100, 100 watt monoblocks) are from Channel Island Audio and I scored them both used. The D-100 was Dusty Vawter's (owner, designer, etc. of CIA) replacement for the VMB-1 (chip amps have had a huge following on DIYaudio.com with supporters praising them for sounding like the best of solid state and tubes).
The D-100 are modded Hypex designs and Dusty is big on hefty power supplies. My speakers are rated 27 watts RMS, 80 watts peak and I'm not a headbanger, so either should have been "enough". In fact my previous was a modded T-amp (7 wpc) which did an amazingly good job, but moving up to 40 watt monoblocks provided better grip/control and improved channel separation (duh), transforming the speakers from polite dinner guests into NFL linebackers in tuxs. I'd heard that my speakers would blossom with more power, so I after years with the VMB-1's I turned back to looking for an upgrade.
Moving up to the D-100 (which were at a price too good to ignore) added more bass control (hit harder) with improved resolution (I'm guessing better parts as the retail price is almost double).
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Rich you never cease to amaze me. Dang your good. Now I understand the difference, thanks. We had a Tripath in the system many moons ago. Some really good results but overall didn't do it for me. Too lean, no meat on the bone. The Arion had meat and presence.
When the amp is switching timing I guess would be key. The sound of the Arion flowed not mechanical in any way. Got the top right. Cymbals just shimmered and decayed similar to the real thing. I would like to compare the Arion to my Cyber 211's.
Tom IMO they would mate quite well with the Thiels. Analysis will be demonstrating for us at a later date this fall.
charles
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You bring up an excellent point Charles, when you say mechanical sound of the switching. The switching frequency is so fast that you have ~25 switches per wave at 20kHz. That's 11x more than the CD standard, so it should not be a concern. It is almost as fast as AM radio carrier, so it's not even physical sound. But there is no reason to assume that the switching will not create a "jitter-like" distortion at high freqs when beat down intermodulation frequency interaction is considered. The class D output filter always uses inductors whose hysteresis prevents a perfect feedback reference if the feedback signal is taken after the inductor. All feedback loops have time delay whether linear or class D, even the Spectron digital feedback scheme with its 20nS delay. Jitter is measured in pico seconds and even in the Spectron with its lowest feedback delay, 20,000pS jitter would be very audible if it were in audio frequencies. Some class D amps take their feedback prior to the output filter which eliminates the hysteresis of the inductor but any feedback delay is huge compared to the jitters audible threshold of only a few pS. The switching jitter is non-linear and so the intermod distortion down in the audible freqs is also non-linear. In a linear amp the intermod distortion is linear (and correctable) because their is no switching jitter.
Some people have alien brain probe reaction to class D amps. There must be a reason for that. It will take time for the reason to be known and accepted by all and for solutions to trickle down to mortals. It took almost 3 decades for jitter to become a mainstream topic to audiophiles so their demand for low jitter DACs is now just this year making them available to budget minded audiophiles. Maybe it is some aspect of non-linear phase distortion that is annoying sensitive class D listeners. Maybe traditional phase distortion measurements used for linear amps is not able to discover the cause of the headnail. I am lucky that I don't have the bad reaction. I liked the Spectron even with a slight edge I heard, and I liked the CIA D500mk1 with no perceptible edge.
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Maybe now someone will not yawn when I mention how good my modified ICE amp sounds? :thumb:
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The output filter used in a Class D amp will exhibit phase shift clear down into the mid-range if the filter pole is too close to the audio band. When I used a Tripath amp it had a modified output filter that was only a 12 db/oct filter. The filter was at about 75kHz which is almost twice the frequency of most of the filters used in Class D amps.
Between the hysteresis distortion from the inductors in the output filter and the phase shift from the filter pole being too close to the audio band ClassD amps have a hard row to hoe. The reason the Tripath amps have a lean sound comes from the dead-band time chosen by the amp manufacturer.
Both positive and negative output devices cannot be in the on state at the same time. There has to be a certain amount of time between the switching on of one device and the switching off the other device.
Into this gap between the on state of the two output devices is where the information goes missing.
The dead band time can be set at 20,40 or 60 nano-seconds. The safest dead-band time giving the greatest protection to the output devices is 60 nano-seconds. This is also the leanest sounding choice. The best compromise for sound versus protection is 40 nano-seconds and this is how my amp was setup. It still sounded lean in the midrange compared with analogue amps but I could live with it.
There maybe a ClassD amp in my future but it will half to equal or beat my analogue amp in the mid-range and highs before it will be allowed in the house.
Scotty
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Thanks Scotty! Great info there as usual. I knew about dead band, but not that Tripath was selectable. You mentioned that all class D amps must have deadband between the positive swinging output device and the negative (and I agree,) but Mark Levinson #53 (http://www.marklevinson.com/ProductDetails.aspx?prdid=1) is a class D amp which claims no dead band, even slight overlap of output devices. Ironically it is by far the worst sounding class D amp I have ever heard, even for my tin ear it is unbearable, even on easy listening classic rock. On the plus side (I think) the transient response is so violent it is physically painful to listen to action movie soundtracks or synth dance music. I'm sure it's measured specs are quite amazing, since that is Levinson's thing. Their new linear 532 costs almost as much and is one of the best sounding amps I've ever heard.
Scotty, what do you think about the idea that switching frequency jitter adds nonlinear noise to high freqs via intermod distortion? Possible or am I missing something fundamental? Some class D designs have even have variable switching freq. which seems to me to make any potential jitter issue even worse. I never believed much in the importance of low intermod distortion until my friend/amp designer Sol showed me how damping an oscillation at 60kHz cured problems at 4kHz.
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Intermodulation distortion is a measurable parameter. It should be possible to minimize its contribution to the problem. The Tripath designs I am familiar with all have a dead-band between 20 and 60 nano-sec. I think this part of the problem was solved by both B&O and Hypex.
Downward intermodulation distortion may not be that big a problem with a switching frequency at 1/2 mHz or higher. These frequencies are a long way from the audio band.
As far as the ML 53 goes there are a lot of things that could be going wrong that would contribute to your negative impression of the amp.
Ringing on the power supply rails could be occurring. The storage-caps and the inductance in the wiring from the the caps to the output transistors form a resonant circuit that can be excited by the high currents and switching frequency the amp operates at.It may be a work in progress and not quite ready for prime time.
I wouldn't use the term jitter in regards to switching amplifiers. It implies a timing error which is not the source of problems in these amps.
The interesting thing is how the ML53 and the ML532 sound so different from each other. They both can't be right. You would think there would some convergence in sound as each approach to amplifier design improves and moves closer to a theoretical ideal.
Scotty
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Thanks for responding to all of my points, Scotty!
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There is a new class D design from Hypex called N-Core. It looks very interesting. The white paper touches on some of the points made above, and their solutions.
White Paper (http://www.hypex.nl/docs/papers/ncore%20wp.pdf)
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We did not detect any of the traits described. The Arion Hybrid design seems to have overcome the nasties associated with Class "D" amps. When I get one to demo in my system I'll really know.
So far the first demo with Analysis speakers was well breathtaking. How will they sound with the Pipedreams ? Time will tell.
charles
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Scotty the Arion has adressed the phase shift dilema according to its designer. That was one of his goals, besides other issues. Sounds like he has accomplised that goal to my ears. Then again it just may have a super synergy with the Analysis speakers. :roll:
If you or anyone wants to try a pair, let me know.
charles
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Well its been awhile. Ordered a pair for evaluation finally. Just too many other things going on. Parts are coming in. Hopefully within two weeks it will be ready for prime time. The only change to the original [ option] will be Deuland Cast output coupling caps.
After hearing Joe's modded Spectron it moved me to act. As good as the Arion sounded when first heard it was not through my speakers. The Spectron did not sound like SS or tubes. Since I was unfamiliar with Joe's system it was hard to tell if it was any particular component. Synergy was very good. Nervosa edging in. Since my experience with both amps was positive , make the move.
It would be interesting to compare a hybrid design to the Spectron.
Being an SET type of guy this is new territory for me. As good as the Cyber 211s sound with the Pipes I oftened wondered about how having more juice would sound. 500W per channel just may handle all those drivers better. At 94db one would think not, however there is a lot of mass with [ 9] mid/bass drivers and[ 24] tweeters.
When shown originally the Pipes were driven by Melos amps. I believe 200W per ch. The designer Lee Porzilli did state they perform better with more juice. What does he know. :-P
When we used the AR 250 with 240W per side the Pipes sounded fuller and more dynamic . However tube rush city. The cost of new tubes [ 32] killed the decision. I mean [ 20 ]6550s alone oh my. Some day when flush new tubes will be had. 8)
With the Qol inserted now the RCA 211s in the amp just may be too colored towards the lush side. Just exposes every darn thing. Changed the output tubes to GE 211s and it made a difference for the good. Not as lush however still rich in character. With more dynamic impact. The jury is still out with the treble region.
The tube change as well as Joe's Spectron got the Nervosa up again. Yeah I'm done HA !! *&^)$# you know what I said. :lol:
Time will tell.
charles
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Interested in your impressions Charles. Have you heard any of the DAC amps that Tommy makes?
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Hi Guys
The second of my Arion 500's has finally been released from Customs - Yippie - and I finally got yo listen to them.
I know we are not supposed to do any serious listening for at least 300 hours but I have to tell you right out of the box they are pretty impressive - and in exactly the way Charles said - namely they are real sounding. They changed a bit during initial listening in exactly that way - becoming a bit more real sounding. They were within a bulls roar of MAC 501's and I am hopeful once fully burnt in they will give them a real run for their money. Already I can say they are above any amp I currently own but I do have access to some much pricier stuff and it will be interesting to see how they go against that as time goes by.
Thanks
Bill
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The output filter used in a Class D amp will exhibit phase shift clear down into the mid-range if the filter pole is too close to the audio band. When I used a Tripath amp it had a modified output filter that was only a 12 db/oct filter. The filter was at about 75kHz which is almost twice the frequency of most of the filters used in Class D amps.
Between the hysteresis distortion from the inductors in the output filter and the phase shift from the filter pole being too close to the audio band ClassD amps have a hard row to hoe. The reason the Tripath amps have a lean sound comes from the dead-band time chosen by the amp manufacturer.
Both positive and negative output devices cannot be in the on state at the same time. There has to be a certain amount of time between the switching on of one device and the switching off the other device.
Into this gap between the on state of the two output devices is where the information goes missing.
The dead band time can be set at 20,40 or 60 nano-seconds. The safest dead-band time giving the greatest protection to the output devices is 60 nano-seconds. This is also the leanest sounding choice. The best compromise for sound versus protection is 40 nano-seconds and this is how my amp was setup. It still sounded lean in the midrange compared with analogue amps but I could live with it.
There maybe a ClassD amp in my future but it will half to equal or beat my analogue amp in the mid-range and highs before it will be allowed in the house.
Scotty
Scotty,
Although the phase shift issue is present in 99% of the Class-D amps out there, it is not catagorically true of Class-D. In fact, at Digital Amplifier Company, we have made conquering this one of our highest priorities. Our newest design, Maraschino Cherry (TM), in development for several years, has a unique advantage when it comes to phase flatness. Another interesting point is that flat(er) phase can come at a terrible cost if not done properly (distortion, latency, etc.).
-Tommy O
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Hi Guys
Heard the 250W non monoblock version the other day in comparison to the 500W version with Duelunds and my new divine KT120 valve amp.
Very good - especially for the money and not as dry as I thought it would be in comparison to the 500W version. When we switched to the HS-500 sorry - game over - it was clearly and obviously better - but hey - its over twice the price with the Duelunds.
The comparison to the valve amp was mixed - some preferred it while others didn't - which is an extremely good showing considering its price. It had better bass grip and dynamics were more startling but sorry - the vocal presence of that valve amp gets to me every time - its just so real and alive I am wowed every time I hear it. Its probably impractical in the sense the valve monoblocks are as heavy as hell and changing them in and out is murder but I will be keeping both amps. Why oh why does it have to be this hard - ah well.
Thanks
Bill