I thought it was time we had a pro- Class D thread. There's plenty of threads about comparisons, or detractors of Class D.
That's fine, you don't have to like Class D amps, and if you don't please go participate on one of those threads.
For those of us who are very happy and excited about having musical, capable amps that we can afford to keep on 24/7 and don't require large spaces to put them in, this thread is for you.
My ARC DS450, is a very capable and musical amplifier. I know Arc uses some proprietary parts in it, and has an analogue power supply I believe, or something to that effect, which doesn't make it like many of the other class D amps discussed. All I can say is, that is a shame that many bad mouth this topology.
I will say that it did need a massive break in period. At first, I will admit, it was murky with little air and honestly didn't compare to my hd220, but now I don't miss it at all. Would I like ref 150? Yep, but I think a ref pre to upgrade my LS-17 would be a better upgrade. The DS 450 is an effortless poweramp, that had more than enough resolution, warmth and musicality to get your foot tapping of hairs standing, depending on what you want at that moment.
I really appreciate your careful reading of the purpose of this thread, not to mention your thoughtful and nuanced contribution to the hobby in general.
I can only hope that the you can contribute as much for others in your life.
randy-11982 posts05-19-2017 9:50amI also saw news on a new Class D amp from Constellation with very high switching freq. - dunno if it uses GaN devices...
Very interesting if it does, I thought Technics had a monopoly on them, if so they’d be the first one to start using them, since the Technics SE-R1 started thing off.
I will say, for the form factor, the Mytek is really small, even for a digital amp. I'm VERY curious to know what is inside it. :) A scaled down nCore? Pair of Pascal amps???? Hmmmm......my screwdrivers scream to be let loose to see inside. :)
I'm such a fanboy Mytek should send me a prototoype. :)
randy-11982 posts05-19-2017 9:50amI also saw news on a new Class D amp from Constellation with very high switching freq. - dunno if it uses GaN devices...
Just checked, just the same as everyone else 600-800khz if they used the new GaN semiconductors it would be 1.5mHz, I wish they did, then that would mean supply to the little folk is available. Technics probably have a monopoly on them for now. " Its Class D amplifiers use a special topology with ultra-high-frequency 600 kHz switching"
I want to interrupt y'all for a millisecond and make the observation that this is the most positive thread of it's sort in progress on AG at this time.
Thanks, Eric....and all y'all that don't feel threatened by a 'new tech' that's beginning to make it's mark on the thing we love....the reproduction of the music we fill our lives with.
The more support you give it, the better it will become. Twas always thus...;)
This is a nice thread, hence a small contribution to the Class D information seekers and long with when Class D will have some synergy with the system.
The largest characteristic of the Class D is the low output impedance. This allows a higher damping factor and in turn more control of the speaker. Synergy 1: If the speaker cannot handle the damping, it will cause break up, distortion and hence won't work. Typically softer cones and larger cones will have this issue. This is not limited to woofers only.
Class D is high frequency modulation or switching which is then filtered to recover the original signal. So band bass filters in essence, high frequency requirements and so on. Most Class D run around 400-450khz. This is much higher then the normal audio band of 20khz. Design, layout, placement, even length of similar runs will create RF noise and distortions. So design of the board, and chassis is very important. The high switching speed places a requirement on the transistors to switch fast. However as with all transistors, there is a lag between the command to switch and the actual full switch. This is call the dead time. This has been reduced over the years with faster transistors and also limited with feedback. But it is fast. Hence the apparent speed of Class D also. Synergy 2: The speakers should be able to hand the speed. Otherwise breakup etc. Bi-amping with a tube/classA (for illustration purposes only) on top and Class D at the bottom causes different speeds, creating a bit of coherency distortion, if there is a word for this.
Most Class D amps use switching power supplies. These have higher instantaneous power delivery. Hence can delivery a very high current and voltage in a small package. There is no large reservoir so the draw on the mains is almost as instantaneous as the draw from the amp. Synergy 3: Power delivery which will include power cords. Line conditioners and other filtering devices, including power cords can limit and clearly slow/change the sound of Class D amps. It is best, IMHO, to remove all conditioners and any high filtering devices but you can listen to the differences to determine what suits you and your system the best.
Class D is quite efficient, however it has to constantly filter the carrier signal and hence the coil gets very hot. This is one of the main sources of heat in the system. The transistors are on or off, so very little heat here. While class D is claimed to run cool, it still requires sufficient venting for the coil to dissipate the filtered energy. So it takes a while to warm up and if not vented, can have thermal runaway and early failures. The heat build up is most when playing, not in idle. For example the VERITAS Monoblocks takes up 20 watts in idle, about the power of 2 LED light bulb or low power CFL. Certainly a lot less then a incandescent bulb at 70 watts
Class D tends to be fast, unless slowed intentionally or with a tube (which helps with dead time distortion also). Synergy 4: personal preferences.
Class D with recent large improvements is catching on in audiophile world. There will always be multiple technologies, as there will be multiple personal preferences. The audiophile world continues to improve in the reproduction of the audio signal, and more rapidly it seems these days. We are luckly.
“In times of change, learners inherit the earth, while the learned find themselves beautifully equipped to deal with a world that no longer exists. ” Eric Hoffer
Thank you you for taking the time to share great insight on Class D amplification. A bit of clarification on couple of things, in your comments,
"Class D tends to be fast, unless slowed intentionally or with a tube" - Are you referring to mating Class D with a tube preamp/Linestage?
In reference to above comment, the end user should be able to reduce "Coherency Distortion" issues with a tube pre as pointed out in your Synergy 2 paragraph, right?
I have been experimenting with Tube/Class D amps in a bi-amping setup with Tube preamp. It hasn't been easy as I intentionally chose not to add any external crossover or gain switch in the signal path.
I do feel I am very close to the attaining that perfect synergy of Tube's lush mid range and Class D's prodigious slam in the low end.
@lalitk I've a tube pre used in conjunction with my class D monoblocks. I absolutely love this combo. Beautiful, lush detail with loads of power and control.
If you don't mind me asking, how the heck are you going to bi amp without a crossover? I do hope you get there..
Just about a month after getting my first class D, I now have two. I love the Primare I32; but it has no acceptable option for headphones. So I got a little Topping TP30 Mk2 which accepts input from the I32's Pre-out and has headphone and speaker outs. I can connect conventional headphones in the conventional way and my Stax electrets to the speaker terminals. It works and sounds quite nice, except the I32 does not have a speakers on/off switch, since it only has one set of outputs. I need a quick, convenient way to disconnect the main speakers, which are bi-wired and a PITA to connect via bare wire, without compromising the 12G speaker wire. As much as I wanted to avoid bananas, I ordered some stackable ones yesterday.
Welcome. I'd like to ask you a few questions about what you pointed out.
However as with all transistors, there is a lag between the command to
switch and the actual full switch. This is call the dead time. This has
been reduced over the years with faster transistors and also limited
with feedback. But it is fast. Hence the apparent speed of Class D
also.
Sorry, could you be mistaking "switching time" with "dead time?"
As I understand, you are talking about switching time. How long to go fron on to off, or vice-versa.
I think "dead-time" is a little different. As I understood, the problem with bi-polar PWM amplifiers (uses + and - V at the transistors) is that you must NOT have the positive and negative sides on at the same time. This affects both efficiency and distortion. I link Wikipedia and a B&O brochure discussing it. (The PDF is a little easier to get).
By the way, this issue with multiple transistors being on at the same time plagued Carver for many years. :) but in his case, he was switching among multiple voltages of the same polarity. Eventually it was solved by reducing the switching speed.
@toddverrone, You may be confusing 'Active' bi-amping with bi-amping.
Bi-Amp - 2 amps wired to the speakers LF and MF/HF binding posts using the internal passive crossover.
Active Bi-Amp - Putting an active crossover in between the amps and the preamp. In this case, it's highly recommended to remove the crossover in the speaker and wire the drivers directly to the binding posts. This adds a level of complexity you may or may not like because you have to know crossover point of the MF/HF and LF drivers.
Fortunately, my VT-80 outputs equal watts in 4 and 8 ohms load with 26dB gain which made it bit easy to coordinate. I tried few Class D amps that had very high damping factor or high gain settings (obviously they didn't quite gel as they over-powered the tube amp). While it's only been couple of days with THOR mono's in my system, I am throughly enjoying their more than adequate bass slam. In my system, the key was to attain just the right amount of low end without overwhelming the mid's and high's. So far I have not notice any coherence or speed mis-match issues.
PS: I am glad to hear that you're enjoying your setup.
In the professional world, "bi-amping" a single speaker system is always active, meaning it uses an active crossover before the amps. Multi-way active speakers also use this type of crossover.
Only in the consumer world is there a question of whether or not to use a crossover when bi-amping, hence the confusion.
Far too many types of crossovers further confuse this, because while most line-level crossovers are "active" or powered, a rare few are passive.
I received my ATI Class D 3-channel amp. Right out the box it's a definite improvement over the Marantz SR5011 and Marantz MM7055 I had. I'm using it to drive my center and rear channel. The power and clarity is just what I wanted. Now if I could figure out how to reduce the white noise between my Marantz AV 7702 and Corus preamp when in HT bypass. I thought I had it reduced with a power cord with the SR5011, but with the current 7702 it's bad. I'll start a new post or revive my old post.
Can’t really argue with that. :) The separates craze creates it’s own list of extra problems to solve.
At the same time, I really really like selecting my own parts. I find it a real difficult thing to want to give control to some one else as to what makes my system.
If I could, a two box system with a 5 channel amp and HT processor would have been here long ago. :)
S&V: Generally speaking, what are the key benefits of Class D versus the traditional Class AB and Class A designs that have long been favored by audiophiles? BP: Efficiency and therefore the ability to construct amps that are powerful for their size. Only that. Modern Class D amps, in particular mine—ahem—sound good not because they’re Class D, but in spite of it. I can’t repeat that often enough. Left to its own devices, a switching power stage tries to do just about anything except amplify audio. You choose Class D to save energy but it’s all elbow grease after that. People don’t realize how much more challenging Class D is compared to Class AB. It’s truly an order of magnitude. Read more at https://www.soundandvision.com/content/bruno-putzeys-head-class-d#S70SckY6kyOPIC2d.99
However as with all transistors, there is a lag between the command to switch and the actual full switch. This is call the dead time. This has been reduced over the years with faster transistors and also limited with feedback. But it is fast. Hence the apparent speed of Class D also.
Sorry, could you be mistaking "switching time" with "dead time?"
Dead time is the consequence of switching time - i.e. time from the garage door switch is pressed (switch) to time you can actually move out of the garage - takes a while for the door to open.
@lalitk "Class D tends to be fast, unless slowed intentionally or with a tube" - Are you referring to mating Class D with a tube preamp/Linestage?
You can use a Tube stage to slow down the signal or other circuit designs in solid stage to do that as well.
In reference to above comment, the end user should be able to reduce "Coherency Distortion" issues with a tube pre as pointed out in your Synergy 2 paragraph, right?
Coherency is very tough and you don't hear it until you hear something coherent. So the short answer is - it is really difficult to get it exact.
One thing I do not agree with Putzeys on is that reality is logical. Reality IS. We can understand it logically, emotionally, sexually, spiritually, intuitively.. or, hopefully, all of the above and more.
You can use a Tube stage to slow down the signal or other circuit designs in solid stage to do that as well.
Agreed- **and** FWIW, there does not have to be anything slow about tubes. Keep in mind that in order for color TV to have existed, tubes had to be able to operate with bandwidth over a range of multiple MHz.
Tubes are only slow because of the design of the circuit, not because of tubes in general. In fact you can build a class D amp using tubes as the output switching devices, and switch them at some really crazy high frequencies- in excess of 100MHz- and likely with no need for dead time circuitry. That's pretty fast! I'm pretty sure solid state isn't there yet (but that's off the top of my head; haven't checked).
in excess of 100MHz- and likely with no need for dead time circuitry
This would be a spectacular improvement upon the state of the art. I can't wait to see it in real life.
Don't even need a working amplifier to try this, just hook up two tubes and have them switch back and forth as you suggest. Please post the pics of the results. By pics, I mean of the smoke. :)
I have over 500 hrs on my S-500 and thought I might comment a little about it.I think it's a step up in Sound vs nc400 and ref600m,these are the 3 class d amps that I own and I have access to more through a local audio club where we lend and or borrow equipment or occasionally listen to each other's systems.
I have been using a bel canto pre3 with all the diff. amps just to make a even playing field,the pre 3 is a pure water no coloration preamp.
The S-500 is the best class d amp I have had in my system and it has the warmest most engaging midrange with very sweet nicely extended top end that has more air and separation with the individual instruments making the entire frequency range very coherent.The bass is equally as good maybe better than my other class d amps listed.
I borrowed a Nuprime st10 to try out and found it too be a very close match to the S-500,with the nod to the S-500 for the best overall sound especially the midrange.
Offcourse this is in my system with my ears and judging the musical presentation that I prefer.
The next test will be comparison with a modwright kwa100se that I have owned for a few years but I haven't used it in about 3 years,I have loaned it out to club members though.I know it's a very good amp but can it equal or beat the S-500,only time will tell.
On my journey to find a class D integrated, someone suggested I try using a power ampalong with a passive preamp, such as the Schiit Sys. some of the amps Im currently investigating are the Class D Audio, D-Sonic, red Dragon and Nuprime models. I recall at least a couple of these have been previously mentioned in this thread,but can readers share their thoughts on any of the power amps from these companies? Thanks for the input as I meander along the path to purchasing a new amp!
Don't even need a working amplifier to try this, just hook up two tubes
and have them switch back and forth as you suggest. Please post the pics
of the results. By pics, I mean of the smoke. :)
Class D was first proposed in the 1940s. The problem isn't the switching, its finding tubes that could manage the current :)
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