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.
Perhaps you feel your preamps are less susceptible than most, which I could believe. I did not make my statements absolute. If you’d like to submit FR charts at different loads like Stereophile has and at different volume settings this would prove your preamps outstanding exemplars.
I have to say that for you to call my statement in its entirety misleading or false when anyone can pull up page after page of examples in Stereophile measurements of tube preamps showing variance in their frequency response based on difference in the impedance they are driving is pretty gutsy.
Anyone can also compare solid state preamps to this and see that in general they perform better by this measure.
So I hope that maybe you misread the generalities and nuances I was making and re-think your reply or produce engineering principles and data which makes all the other data and the basic electric principle of impedance in series and voltage division a quack science.
I'm sure you make fine products, but would you then please explain the
variance in all the tube preamps in the Stereophile section if not due
to output impedance issues?
My prior post was a correction and not an attack. I was merely pointing out where the problems were and stated why, basic engineering principles included. More are below.
We won't allow Stereophile to review our products (we don't agree with their editorial policy which seems to be tied to their advertising and I know this from direct experience) which is one example of why if you limit yourself to their pages, you won't get the full picture.
This has more to do with the choice of coupling capacitor at the output of the preamp than it does the output impedance!
Please note that this phenomena has to do with solid state just as much as tubes.
Of course, the ultimate indicator is a graph of the output impedance vs. frequency. If you see it rising as it approaches 20Hz, this **might** indicate a loss of bass impact depending on the input impedance of the amp. The general rule of thumb is a 10:1 impedance difference between the two; as long as you hit that margin with the amp you have in mind its likely no worries.
The output impedance curve of our balanced preamps looks the same as their frequency response curves; we cut them off at 1Hz. So regardless of the load its driving, the preamp will have flat response from 1Hz to over 200KHz. Ours are not the only tube preamps with direct-coupled outputs that have ever been made- as a result you can't just assume that if it has tubes that it will have troubles making bass into a solid state amp with a 10K input impedance or the like. Generalities are often misleading that way.
My prior post was a correction and not an attack. I was merely pointing out where the problems were and stated why, basic engineering principles included. More are below.
You called my statement:
mostly misleading or outright false.
That’s not a correction. If you had said "I feel distortion is a bigger issue" then it’s a matter of opinion as to which is more audible. If you want to say I wrote falsely or in a way to mislead back it up.
You then state:
This has more to do with the choice of coupling capacitor at the output of the preamp than it does the output impedance!
What, exactly, are you claiming is a result of the choice of coupling cap? Distortion or output impedance?
The general rule of thumb is a 10:1 impedance difference between the two; as long as you hit that margin with the amp you have in mind its likely no worries.
The biggest issue with input/output impedance is the change in frequency response...
I was very specific in what I was talking about. I did not say "the biggest issue with tube preamp sound quality." I said the issue with "input/output impedance."
If you see another issue with input/output impedance to be more important, please show your work.
A statement of fact is not an attack. You are taking this personally.
Here’s the work:
What, exactly, are you claiming is a result of the choice of coupling cap? Distortion or output impedance?
Here’s a formula for calculating cutoff frequency: F=1,000,000/CxRx 2Pi
Normally you see this formula with a 1 instead of a million; I used the latter so that f is in Hz (-3db point), R is in ohms and C is in uF.
The coupling cap at the output of a preamp, in concert with the input impedance of the amplifier used determines the cutoff frequency.
example: a solid state preamp has a 10uf output coupling cap. The input impedance of the amp is 10K.
1.59Hz=1,000,000/10K x 10uf x 2Pi
We can see from this example that if a tube preamp has a 10uf coupling cap that it too will have a cutoff of 1.59Hz into the same amp.
This means there will be no appreciable phase shift at 20Hz so bass impact will be unimpaired, since the cutoff is 1/10th the lowest frequency to be played. A cutoff at 20Hz will mean that phase shift exists up to about 200Hz. The phase shift will cause the system to sound lean.
Many tube preamps **do** have such large coupling caps unless the designer has not done their homework (or has figured out that the larger the coupling cap, the more coloration it imposes, and so has elected to limit the capacitor size so as to get greater transparency). As a manufacturer you can’t forecast to what amps the preamp will be paired.
The size of the coupling cap will not affect the output impedance unless one is able to graph the impedance curve; if rising at lower frequencies the culprit will be the output coupling cap and otherwise not the output impedance of the preamp.
Now how much **distortion** the preamp makes can be affected quite a lot by the load that it drives. That is likely the more powerful argument for being careful about what preamp drives what power amp. Tube preamps often have very low distortion; in most cases its a good idea to have them drive a higher impedance so as to take advantage of that fact. Our preamps again are an exception- they regard 10K as an effortless load.
Please note:
This supports, not undermines, my statement.
yes, this is evidence of how this was simply a statement of fact and not an attack.
The biggest issue with input/output impedance is the change in frequency response...
I was very specific in what I was talking about. I did not say "the biggest issue with tube preamp sound quality." I said the issue with "input/output impedance."
As we can see, if one is to point at a tube preamp and blame it for a change in frequency response, the factor is not the output impedance (which is often only stated at 1KHz), its the coupling cap at the output. That is a bit different from ’output impedance’ and that is why I placed the correction.
The biggest issue with input/output impedance is the change in frequency response....(followed by supporting discussion with links to external sources)
You replied:
This is mostly misleading or outright false.
Now your latest posts seem to be supporting my argument. I’m not sure you even read what I wrote before you claimed it was a lie or misleading, but you launch into discussions about how Atmasphere preamps are different (which while informative does not make your case that I was wrong).
So I challenge your "statement of fact" as having anything which directly refutes my statement with evidence.
As we can see, if one is to point at a tube preamp and blame it for a change in frequency response,
I don’t "blame" preamps for changes in frequency response. I say high output impedance causes frequency response changes which vary based on the load. This is an irrefutable fact based on simple serial circuit analysis. Anyone with a basic understanding of AC circuit analysis would conclude the same.
It is also irrefutable that in general, tube preamps have higher output impedance than solid state. That is different than saying preamp X sucks, which is what you seem to have read.
the factor is not the output impedance (which is often only stated at 1KHz), its the coupling cap at the output. That is a bit different from ’output impedance’ and that is why I placed the correction.
A - I never limited myself to 1 kHz B - It makes no sense to talk about changes in frequency response if i was talking about a single point C - The coupling cap is a major if not THE major contributor to output impedance. However it is not the only issue. I never said it was. The factors that go into any devices output impedance is more complicated, but includes the coupling cap if any.
There is no logical way to make both of these statements true at the same time:
Tube preamps don't have a problem with output impedance
The problem with tube preamps is the impedance of the coupling cap
Since the first includes the second, you can't have both of these be true at the same time. Best,
I was taking a look at the NAD C390DD integrated. I like the concept of being able to change out the boards as upgrades become available. Anyone have experience with the sound quality of that model?
I don’t "blame" preamps for changes in frequency response. I say high
output impedance causes frequency response changes which vary based on
the load. This is an irrefutable fact based on simple serial circuit
analysis. Anyone with a basic understanding of AC circuit analysis would
conclude the same.
And I showed the math for why that is not so: the first half of your quote here is false, the second half being based on the first is thus also false.
**Do the math**.
Its the coupling cap at the output, not the output impedance that governs the frequency response.
Example: I've seen ARC preamps with 20uf output coupling caps. If you put them on a 10K load, they will be as flat as they are on a 100K load in the audio passband. Yet the very same preamp according to ARC should not be asked to drive anything less than 30K.
Your claim to which I was objecting was that the higher output impedance of tube preamps leads to frequency response errors and the simple fact is this is not so- it depends more on the timing constant that may or may not be present at the output of the preamp in question. I showed the math. If you wish to refute this, then show the math.
Atma and all, let us please return this thread to its original topic. There are better places to discuss preamplifier design than this rare thread for class D amp enthusiasts.
I have reached 100 hrs on my dragon s500 and not really much change.It's a little lean and bright,nothing horrible,compared to my 600m's.I won't fully evaluate it till past 1000hrs,I have it playing in my 2nd system for now.Time will tell.
Erik. Keep up the good work on this thread about class D amplifiers, Designers such as Atamasphere will beat a topic into the ground to prove their point. He isn't the first, won't be the last. Again, good work on your part. I have a Class D integrated hybrid, and couldn't be happier.
Given that this is Erik’s thread, I presume Guido and the others posting above won’t deem it inappropriate if I comment on the disagreement between Erik and Ralph. Apologies if that is an incorrect presumption.
Ralph, it appears to me that what underlies much of the disagreement between you and Erik is that he is viewing the impedance of an output coupling capacitor, if present, as contributing to and being part of the component’s output impedance. While you are not, possibly because you are considering "output impedance" as corresponding to "specified output impedance," which as we all agree is often based on a mid-range frequency such as 1 kHz. The capacitor’s impedance of course being unlikely to be a major contributor to the 1 kHz output impedance in just about any reasonable design.
Regarding that terminological difference, I would have to agree with Erik, and consider "output impedance" to be whatever impedance is seen "looking back" into the output of a component, at a frequency that should be and hopefully is stated. Also, as he pointed out, measurements of **many** popular high quality components that have been presented over the years by John Atkinson in Stereophile, that have specified output impedances of perhaps a few hundred ohms, show impedance rises to the vicinity of 3 or 4K or even more at 20 Hz. Obviously the sonics of such a design would be compromised to some degree when driving a low impedance, such as 10K, or even 30K or more in some cases.
On the other hand, regarding this part of Erik’s statement that you quoted above:
I say high output impedance causes frequency response changes which vary based on the load. This is an irrefutable fact based on simple serial circuit analysis.
As I assume he would agree, high output impedance will not affect frequency response when driving a resistive load if the output impedance itself is resistive, and does not vary significantly at relevant frequencies. As I said in an earlier post, it is the **variation** in output impedance, as a function of frequency, that may be significant in that regard. Although of course under extreme circumstances high output impedance can in itself affect frequency response in the treble region, even if there is no variation as a function of frequency, due to its interaction with cable capacitance. Capacitance not being a resistive load, of course, by definition.
Hopefully this post will result in the divergent opinions expressed in the foregoing posts becoming less divergent.
I think Class D is as good as many Class A or AB designs. It may sound different, as some amps will sound different to each other regardless of the technology. Some may also deal with different speakers differently, just like Class A/AB designs.
I think there are some very affordable great sounding Class D amps right now. Please skim this thread for a number of good suggestions, and listen for yourself.
My Class D monoblocks sound as good as mega-buck class A amps to me.
Let’s say my hearing is impaired (for argument’s sake). Why would I buy anything more expensive I don’t hear an improvement for? :)
I'm trying to get a hold of a pair of Bel Canto Ref 600s to compare to my Jeff Rowland 625 S2. May be time for a change. I'm curious to hear if they mate well with the Corus preamp.
I had been planning a change in my system for quite a while that just started coming together. I went from a system that paired a Cambridge 851N DAC and ARC DSi200 integrated amp to a system that pairs a PS Audio Directstream Junior with Bel Canto Ref600m amps. I've had the new DAC for a couple weeks and the amps just arrived yesterday. Still breaking them in, but so far so good. The jump in DAC SQ was major, as one would expect with a more than doubling of price. The first thing I noticed about the Bel Canto amps was greater bass authority. Besides that, I've got a lot of variables going on. We'll see. For now, I'm having a grand time.
As an aside, I work in the energy efficiency consulting industry and I like being able to leave my equipment on all the time without feeling like I'm wasting lots of energy.
ricred1735 posts05-05-2017 5:43amI’m trying to get a hold of a pair of Bel Canto Ref 600s to compare to my Jeff Rowland 625 S2. May be time for a change. I’m curious to hear if they mate well with the Corus preamp.
@ricred1 I got my Bel Cantos through a dealer that made me an incredible deal. I have no skin in the game whatsoever, but if you're curious about the Ref600ms, send me a message and I can forward the dealer's info.
Ralph, it appears to me that what underlies much of the disagreement
between you and Erik is that he is viewing the impedance of an output
coupling capacitor, if present, as contributing to and being part of the
component’s output impedance. While you are not, possibly because you
are considering "output impedance" as corresponding to "specified output
impedance," which as we all agree is often based on a mid-range
frequency such as 1 kHz. The capacitor’s impedance of course being
unlikely to be a major contributor to the 1 kHz output impedance in just
about any reasonable design.
Thanks Al! To be clear here, this was Off topic (we're working on our own class D circuit that is not based on any modules so you can draw your own conclusion about what my attitude about class D is); my main concern was was to try to express the idea that it was the output coupling cap in a given design that was determining the frequency response variation seen in some designs. Since there are tube preamps with a high output impedance that also do not have the rising impedance as seen (due to the fact that they have larger coupling caps), its hard to allow a generalization like 'high output impedance leads to frequency response errors' or the like. It doesn't have to was my point and I didn't have to look very far to find examples.
Put another way, its the rising impedance at low frequency, not the **overall** higher output impedance that causes the problem; I should have expressed it that way earlier!
Atma, I understand now the reason behind the technical discussion on line stages... Very exciting that you are working on an amp project based on class D. Please do keep all of us posted!!!
Sorry- I've said as much as I can offer at this point: 1) its not a module but our own circuit 2) it looks like we have something to contribute in terms of technology.
Hi Ralph, Having an integrated with a preamp section as wonderful as yours with a Class D output done right would be a match that would produce big sales.... Just putting that out there, but I'm sure that you know that. Good Luck Brother, I look forward to what ever new comes our way from you. Tim
@samac I recently acquired a Nuprime IDA16 and I am very impressed with it. I am using it with Amphion Argon 1 speakers in my office. It is still improving, but I agree, it is a remarkable amp, and a remarkable bargain. I'm not thrilled with the remote, or the front panel buttons, but in terms of sound quality. it is very, very strong.
And on topic, it is nowhere near metallic, or fatiguing. In fact, it is already a much more .... easy, amp than the Hegel amps I've listened to. I don't understand any of the technical stuff, but my class D amps, the Nuprime and my Devialet 220 Pro, are outstanding. Dandy? Yes.
I saw a Nobsound TPA3116 mini power amplifier for $40, so I figured, "Just how bad could that be?" and along with a 24-volt PS for another $10, I was surprised how GOOD the little box sounded, when hooked to my Large Advent Loudspeakers (circa 1975, new foam rings in 1990).
I tested the set-up with a broad range of musical types-- Jazz Classical, Rock, Live Rock, and I was impressed for a $50 Class-D chip amplifier.
Then I plugged the harman/kardon 330i back into the system, and there was no fair comparison.
My conclusion was the Nobsound (which I might add can be bought from another vendor for as little as $25) would be just fine for the garage, or a workshop, with a pair of small speakers. At that price point it was acceptable, listen-able, and surprisingly small. At 90% efficiency, the power draw for the wall-wort would be negligible.
No sense in trying to compare it to some high-end exploitations of the Texas Instrument chip, but in the right circumstance it wasn't THAT Bad.
Unfortunately, folks like to make blanket statements like "Class-D is inferior"... but that is the same as saying "I like Limes but not cherries"...
I see that Professionals have embraced Class-D in PA systems, and some high-end applications are very good. If this technology is like other aspects of progress, in 5-years we will marvel at what amplifiers might look and sound like.
Anyway, as the "Computer Audiophile on the Cheap" -- I gave the Nobsound a fair trial, and deemed it to be just fine, if we are NOT talking about Audiophile listening.
I admit, being unable to best a 1980s era radio receiver is a very tall standard to eclipse, but I didn't want to send it back for a refund, so I will find it a home...maybe hot-wired to my 24-volt power wheelchair, a pair of cheap speakers, and an MP3 player. I can sound as 'Bad' as the folks with external speakers on the cars with huge rims...
I bet the NuPrime/Amphion combo is excellent. I'm a month in with my IDA16 and I love it. I'm using it with Bowers and Wlikins 683 S2s. With the sound I'm getting I have to believe the DAC in it is outstanding as well. Yeah, the feel of the buttons on the remote and the front panel are lacking a bit but they work very well. The volume control on the IDA-16 is fantastic, it tracks beautifully.
I agree with you. There is nothing fatiguing about it . It is refined and powerful.
First time Forum responder...aged audio dude...amps along the path include modded Electrocompaniet Ampliwire II (1980's start of good sand amps) ...modded Moscode 300...Muse 160 and now the direct digital NAD M2 integrated ($6K) with full Marigo dot treatment and fuse upgrade. Small room with Salk Veracity HT1's (sealed for added detail) & a pair of Paradigm Ultracube 10 v.2 sub woofers, also Marigo dotted. I was raised in a household of live music, nearby cousins becoming professional musicians. My musical "truth" is instruments and vocals sounding as they do in real life, without amplification. In a hi fi, it begins with good electricity..good grounding and dedicated lines with good outlets. I've been exposed to uber systems, including Volti Audio, better new Marigos, large Kings, Emerald Physics, Tannoys... plus. The NAD M2 simply BRINGS IT! with refinement, depth, stage, air and full slam of the expensive stuff. Without the Marigo dot treatments, things were a little bit "hi-fi" sounding, a bit dry accompanied by that detachment that can happen with digital sources. My audio niche is finding great stuff on a reasonable budget, and making it come more alive with ancillary upgrades. I have several audio buddies who have gone from excellent tube and SS amps to versions of the NCore amps without looking back. The time is here. Pinthrift
Check out the Auralic Merak mono block Class A/D amplifiers that put out 400 watts per channel into 4 ohms. Google the reviews. These sell for $5000 for the pair new. These are the best sounding Class D amps I have heard, and can be had for under $3000.00 used. Often for less than that.
I'm reluctantly selling my Meraks so I can raise cash to get new speakers.
These Auralic Merak, (linear power supply and Hypex D-amp modules), you only just got them 1 month ago?? Going back to the Parasound A23 that you have?
I shouldn't have bought them since my main goal was to upgrade the speakers. I have too much equipment right now and need to Get rid of some excess stuff. I really like the Meraks and will have to determine what stays and what goes.
randy-11: "Can anybody list very affordable great sounding Class D amps - say below $2,000 for a stereo pair, and better or comparable SQ to a Sunfire amp?"
I'm not sure if you're looking for a stereo amp or a pair of mono-blocks.
But for stereo amps, I'd suggest: ClassDAudio SDS-470C for $700. I own the model just under this, the SDS-440-CS for $630, and it's a very good performer so I would think the 470-C sounds similarly good with a bit more power than the 440-CS. Not exactly audio jewelry but bargains sound wise. D-Sonic M3A-1200S, 2 x 600w for $1,875. Stereo version of the M3-600 mono-blocks that are very good. D-Sonic M3A-800S, 2 x 400w for $1,475. Red Dragon S500 2 x 250w currently on sale for $1,899 (reg price $1,9999 black in stock but silver temporarily sold out). Very well reviewed and uses dual Pascal class D power modules usually used in very hi-end amps.
For mono-blocks:
D-Sonic M3-600-M 1 x600w for $2,150/pair. I've owned these for about 2yrs and use them to drive my Magnepans with 1,200w @ 4 ohms. By far the best amps I've ever used on them. D-Sonic M3-1500-M 1 x1,500w for $2,750/pair. I haven't heard these in my system but, based on the rave 6Moons review I read on these, they may give you the best performance short of spending $10k+ on the excellent Merrill Audio Veritas monos. Use the highly regarded Pascal power modules. Red Dragon M500 1 x250w currently on sale for $750 each (reg price $800 each black in stock but silver temporarily sold out.) Very well reviewed and uses Pascal class D power module usually used in very hi-end amps.
There are others I haven't heard such as the Nord monos from the U.K. and the James Romeyn Hypex NC-400 mono kit amp builds in Utah
This "competes" is not saying anything, as I can "compete" against
Usain Bolt in a 100mt race, I don't think there'd be any money put down on me to win anywhere in the world!
But I think we all know what the others mean by "compete," whether we agree with them or not.
Best regards, -- Al
FWIW dept.:
@almarg , you might be interested in a book called 'Born To Run' by Christopher McDougall. In it, we find out that we are the dominant species not just because of our brains but also because of our ability to run further than any other animal. Not as fast for sure- its well-known that a cheetah is only good for short bursts. Its a fascinating read.
I've yet to see a class D amp keep up with a good tube amp, but that is on my Classic Audio Loudspeakers, which are not well suited to solid state in general . As a result, I'm sure there are those that would say they are 'difficult to drive' despite being 16 ohms and 98 db 1w/1M :) On a different speaker I would expect the situation to be reversed. Just saying- its important to include the speaker when talking about what is 'competitive'; blanket statements can get tricky in high end audio.
On a different speaker I would expect the situation to be reversed. Just saying- its important to include the speaker when talking about what is 'competitive'; blanket statements can get tricky in high end audio.
So very true,So much too matching speakers and amps.
Atmasphere 5-11-2017 ... you might be interested in a book called ’Born To Run’ by Christopher McDougall. In it, we find out that we are the dominant species not just because of our brains but also because of our ability to run further than any other animal. Not as fast for sure- its well-known that a cheetah is only good for short bursts. Its a fascinating read.
Thanks, Ralph. I’ll check it out. Having run one marathon and a lot of middle distance races in my younger days it definitely sounds of interest.
My understanding is that at middle distances the fastest land animal is the pronghorn antelope, which is found in western North America. According to Wikipedia it can do 35 mph for 4 miles. Of course there are many humans who can go vastly further than that.
And of course +2 re the importance of putting amps and speakers into context with each other, and being cautious before making blanket statements.
Our Kangaroo some say in plague proportions in Australia is very efficient, a bit like the Class-D, of the distance v speed travelled in the animal world. But is very one dimensional in it's movement and that straight ahead, easily picked off by a Mick Taylor (Wolf Creek) https://www.youtube.com/watch?v=uTUp4IJ_xqQ Cheers George
I think Im descending further into the rabbit hole with this but any thoughts on how the ICE Ncore and Hypex UCD modules stack up against each other? Or has anyone noticed any differences? I know there are many other pieces that produce the final sound but will the different modules have an affect?
i was told by an audio manufacturer that they were told by a supplier that Hypex was superior to ICE. What are everyone's thoughts?
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