Hi Mapman, what is fascinating is that the NCore NC1200 modules do not seem to leak RF into the air regardless of power supply design.... Merrill Veritas use the basic non regulated Hypex SMPS that matches the power conversion module... While Rowland M925 uses a custom massive multi-regulated SMPS.... Neither amps generate any extra noise in an FM tuner operating near them.
Perhaps Tim can do the test on his D-Sonic powered by the AbleTech module and tell us results.
All, please note that if some RF leak occurs, that does not mean at all that the particular class D amp does not generate good music... the ICEpower ASP1000-based Bel Canto Ref1000 Mk.2 and Rowland M312 remain absolutely marvelous amps... Just do not stack an FM tuner just on top of them.
G. |
B, I think excellent recommendations from Guidocorona. I know he has a big interest in Class D amps and probably has actually heard and spent time comparing the most of just about anyone I am aware of in these parts. |
OK Guido, now you've accelerated my desire to add a pair of pangea ac9 cords to my amps to go with the AC14ses on my line level gear.
I guess it never ends. :^} |
One other thing I would note about Class D amps is that they typically seem to have very high damping factors. That will play well with larger speakers taht can benefit with more control of the driver movements as a result of the high damping factor. My large OHm F5s use a 12" walsh style driver known to benefit from high damping in terms of bass control and articulation and that is in fact the result.
Due to high damping, Class D amps can come off as somewhat lean in other speakers. That is the case with my smaller Triangle monitors in particular. I have those set up accordingly to compensate and the results are still quite top notch. My Dynaudio monitors are more in between. I like the clean taut articulate bass that results with them as set up (see my system pics) but I could easily see where some might consider the sound a bit too lean despite the fact that the bas is all there and very detailed and accurate. it just won't be shaking the rafters, at least on most recordings. |
B_Limo, in a lot of cases, the answer is... "It depends"... But here are some specifics as they have applied to class D amp I have used... ROwland M312, Merrill Veritas monos, Belcanto REF100M and REF500M, Rowland M925.
Q: Leave on 24/7?
A: Yes, in all cases... Takes at least 24 hours of playing time for all class D amps in my test set to reach peak performance after being off for a spell.
Q: Plug in its own AC circuit?
A: It depends.... Amps with high degree of power supply isolation like Rowland M925 do not inject much noise back into the AC line, others do. In all cases, you may get slightly better dynamics by plugging power amps in a dedicated outlet.
Q: Stacking or not.... RF leaks?
A: It depends again on degree of isolation... Newer amps like Rowland M925 and Merrill Veritas do not leak RF... Try moving an FM radio on top of them... You will not hear any additional hash on the radio... IMO stacking is OK with these... Both amps are based on Hypex NCore NC1200 modules.
Q: What power cords?
A. Use high current capable power cords... with class D amps, instant current swings/transients can be huge. Do not use analog cords for low power applications, nor old style "digital" cords like the old Shunyata VX.... They will "caramelize" the sound. Note that some cable manufacturers might have today new styles of digital-ready PCs that handle high current class D amps... E.g. Check with the Shunyata factory for their recommendations.
Let me know if you have further questions. G. |
Xt explained it pretty well I would say. THe Wikipedia article is a good one and highlights key advantages and disadvantages of each. The main advantage of Class D is its efficiency, and often a resulting smaller package. Class D amps are a practical alternative in cases where a large heavy and expensive monster class A or class A/B amp would be needed for best results otherwise due to speaker power and current demands. Its a common case these days that smaller inefficient speakers with extended bass are designed to fit tighter quarters. A Class D amp fits this need well. Some good quality 250 w/ch Class D amps with decent current delivery capabilities can be had for less than $1000 these days. Most smaller ineffficient speakers capable of extended bass in larger rooms will likely benefit sonically from teh extra power and current. In my case I find the high power Class Ds to be uniquely capable of driving the larger OHM speakers that I like, hence my enthusiasm over that pairing in particular. They also benefit my smaller Dynaudio monitors compared to other higher power SS amps I have used in the past, but the benefits are greatest whenever more power and current out of a smaller more efficient package is what the doctor ordered. |
I'll try the most basic explanation. I really only know that Class A amps are usually lower wattage, inefficient (whatever that means aside from drawing more electricity from the outlet...), run hot, but sound good (right?). The output is always on driving both the positive and negative side of the signal. Class A/B is some type of dual mode where it runs in Class A for the first few watts then switches to Class B? Now this doesn't really make any sense to me. Wouldn't the transition be audible? Not at all. Class A/B has 2 outputs where one side only passes the positive part of the signal and the other for the negative side. You also just doubled the output power. Can you hear the switch over? Um no. Some manufacturers will start in class A then switch to A/B for more power. Then Class D... some type of switching amp, where it switches on and off? This makes no sense to me either. And why the heck did I think it was a Digital amp? The outputs are turned on and off very fast (usually in the mega hertz or way out of the audible range) and then filtered. So the output is on as much as it is turned off. But the resulting output like the input is analog (sine wave). Digital is a bunch of square wave pulses that needs to be converted to analog. With Class D the signal is analog with the power being turned on and off. Of course it gets much more complicated than that but it's my most basic understanding of the different classes of amplification. |
Ok, now I remember why I can't get this...
Can someone dumb it down for me as far as Class A, Class A/B, Class D?
I really only know that Class A amps are usually lower wattage, inefficient (whatever that means aside from drawing more electricity from the outlet...), run hot, but sound good (right?).
Class A/B is some type of dual mode where it runs in Class A for the first few watts then switches to Class B? Now this doesn't really make any sense to me. Wouldn't the transition be audible?
Then Class D... some type of switching amp, where it switches on and off? This makes no sense to me either. And why the heck did I think it was a Digital amp?
Anyhow, when I go to research what a Class D amp is, or any amp/preamp/dac/electronics, my research instantly turns into me looking up 15 words in the first paragraph which leads me to look up 100 more words, trying to wrap my head around it all, then steam comes out my ears and I start twitching.
I'd like to have a better understanding of all this so maybe someone can describe it in layman's terms?
PS, Thanks Mapman for your input. I've noticed you've been raving about your Belcantos for awhile now, not quite as much as ohms, but close! Good to see you enjoying the setup |
I mean class d, which I thought was some type of digital amp...I just briefly read about that lastnight. I'm going to go read up for a minute and see if I can get this... |
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I prefer Class D left disconnected at all times. |
In my system pic, you will notice that I do keep my amps on their own stand physically separated from other line level gear to help insure against noise. Can only help and not hurt. One can always experiment either way to see if it makes a difference. I also keep some space between amps as additional physical isolation between the two.
ALso not that it seems there have been strides made with newer Class D amps in regards to noise levels. Mine are a generation old and are quieter than what proceeded them. The latest and greatest are likely even better in taht regard, but of course every product is different. Its just worth noting that these things can produce a fair amount of RF noise if not addressed in the design.
Also not that Class D amps are switching amps, not digital, however both use very high frequency oscillators that produce RF noise and that must be controlled, either by design or otherwise. Most modern devices like Class D amps and computers that can suffer from noise issues designed for hifi audio use tend to have these things largely in control due to their potential negative effects on sound quality but just be aware that it can be a real issue that can limit performance if not under control somehow. |
Whoops in response to question 2, I do plug my amps into a different wall outlet from the rest of my gear mostly as a convenient way to utilize the outlets I have available. My line level gear plugs into a conditioning strip and my amps plug into a different wall outlet directly. Seems to work well. Noise levels are non existent and everything sounds most clean smooth and dynamic. |
I can only offer my experiences in my case. Different products may always behave and perform differently.
Do digital amps benefit from being left on 24/7in the same way the ss amps do?
I don't notice too much difference in teh sound quality either way but I leave mine on most of teh time unless I know I will not be listening for a day or more mostly out of convenience. Power draw idle is small.
2. Is plugging a digital amp into a different outlet as your preamp as crucial compared to a ss amp?
Digital (Class D) amps have their own unique noise characteristics due to their high speed switching nature. I find using shielded ICs to be beneficial in this regard but also use unshielded ones but these tend to be more sensitive to noise issues.
3. Do digital amps have small transformers? If so, is distancing equipment from one another less important? (My peachtre Nova Pre/220 look best stacked).
Mine uses a dedicated power supply circuit board internally. No large or heavy parts involved. It works well...the amp never sounds even slightly strained or runs our of steam or clips that I have heard. Some other designs I have read about do appear to still use overbuilt large and heavy power supplies that may work well also but seems to defeat the purpose of being small and lightweight.
4. When upgrading power cords on a digital amp, do you look for cords that do well with digital gear like your preamp and dac, or do you still go for a beefy cord?
I use upgraded cords on my line leve gear to control noise but still use stock cords on my amps in that I have no clear reason to change. They seem to do teh job needed well. I might try better ones someday just to see but stock cords are not a problem as best I can tell.
I apologize ahead of time for my ignorance on the matter! Thanks! |
B limo,
By 'digital amps' do you mean class d amps? 'digital amps' is a bit of a misnomer probably persisting because people believe 'class d' refers to digital, but it was just the next letter in the alphabet used to designate various types of audio amplifiers using different methods of amplification. Class A defines amplifiers that use a more traditional circuit that has input devices that constantly remain 'on', resulting in excellent sound but produce excessive heat as a byproduct. Class D amps use 'switch mode power supplies' (smps) that are able to switch on and off extremely quickly, which produces much less wasted heat as a byproduct. I use a pair of class d mono-blocks that sound very good, output over 1k watts and barely get warm to the touch no matter how hard they're driven. I leave them on 24/7 since they only require a few watts of electricity at idle.
I'm no expert on amplifier design, so others may need to answer your other questions. So, if by 'digital' you meant class d, then yes I would advise to leave them on constantly. I thought it would be useful to clarify your question before your thread progresses.
Let us know,
Tim |
