Article: The Value Proposition in Audio: It's Not Your Father's Class D

[bluesman]

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[bluesman]

5 hours ago, The Computer Audiophile said:

As usual @bluesman, well researched and very informative. Thank you!

 

I'm sure many will be interested in your take on the Purifi Eigentakt modules, but perhaps that's not the price point you were going for with this article. 

They're a bit costly to be considered value pieces at the entry level.  But even at $1k for the module, they may represent great vaue in the high end market.  When I sell my Rogers LS3/5a monitors (currently posted in the classifieds), I'll get a stereo board and build a monitor system with them to see how good they are.

 

For interest, here's the basic spec sheet on the 425 W unit:

 

[bluesman]

17 hours ago, PeterG said:

Thanks for the great review.  I especially appreciate that you've done clear comparisons against traditional amps, and have skipped the chip-on-the-shoulder attitude that pops up too often in Class D discussions

I'm so glad you found it useful.  The only thing preconceived notions can accomplish is to prevent the possessor from learning and improving.  The most important thing is what we hear, not the path it followed to get there.  😀

[bluesman]

34 minutes ago, PYP said:

A very interesting review.  I had no idea that the kind of performance you discussed was possible at this price, although the Shiit Audio gear, which I haven't heard myself, gives a sense of what is available at lower price points (however, seemingly made in U.S.).  

Thanks! I'm a professional musician.  My jazs trio plays every Thursday night at a local club, and I record as many of my shows as I can with my TASCAM DR40x recorder.  I was able to get our entire show last night, and I edited the raw file into tracks this morning.  I then sat in the living room with my coffee and listened to it all, since I make these recordings to find ways to improve my playing, my tone, and my band.

 

So I'm sitting there paying close attention to the music and thinking how happy I am with my Prima Luna amp and Focal speakers........when I realize that I still have the little Douk in the system, not the Prima Luna.  I was marveling at the clarity and realism of the drum kit - the cymbals really sounded fantastic and alive, with the small and the large ride cymbals easily distinguishable.  The kick drum was right there and the snare was tight and crisp. 

 

The bass player plays a very interesting electric upright that he designed and muanfactures (the Kydd Bass).  It sounds great live and it sounds just as great in my living room today through the Douk.  I'm still blown away by the sound quality I can get from  a $129 amplifier!  It may not be quite up there with its 4 and 5 figure cousins, but it's very very good!

[bluesman]

1 hour ago, davide256 said:

Not saying the treble is bad for class D but my experience so far is that its not forgiving for up stream flaws.

That’s why I was so amazed at the quality of reproduction of the cymbals in particular and the entire drum kit.  I sit directly in front of the drummer between the hi-hat and crash on my left and the ride on my right.  So I’m very very familiar with their sound.  I use good IEMs for blues shows (loud) and none for quieter jazz - so I know them acoustically and through a very good reproduction system.

 

The Douk is surprisingly realistic top to bottom, and it makes a believable 50+ WPC into 8 Ohms.  My little TASCAM recorder does a stellar job.  But it cost less than $200, so the two mics in it probably don’t have Neumann trembling.  So there are “upstream flaws” for sure.  Class D won’t remove them, but the best examples no longer magnify them either.

[bluesman]

1 hour ago, Geoffrey said:

A fine article and reportedly iFi continues to have issues with software, which is keeping me from pulling the trigger on the iFi Zen Stream. 

I have some real world experience with some S.M.S.L. amps. I first bought the S.M.S.L.  SA300 for $139.00 and was impressed. The SA300 uses one Infineon Merus MA12070  amplification chip. However, my then situation did not allow me to position my bookshelves properly, I was forced to position them way too high, so it wasn't until I moved to my current abode that I discovered that the SA300 biggest flaw for its price class is IMO, in a lack of depth in the soundstage.

 

6 months ago I bought the SMSL AO200 @ $279. which employs 2 of the same Merus amplification chips and that provided a big upgrade in performance. Depth of field was now acceptable, though not outstanding.

 

3 months ago I purchased a pair of Elac Carina BS243.4 Bookshelves with dedicated stands on sale for $999.00. I'm using the AO200's  sub out to a Quad LF66 subwoofer. That combo works well. But I intend to use the AO200 amp in my desktop system, along with the Quad sub, so I need some replacements to use with the Elac's. 

 

Enter the SMSL A300 ampifier @ $196.00. I intend to buy two of them and Bi-Amp the Elac Carina bookshelves. Coupling them with two Emotiva Airmotiv SE8 Flex 8" Subwoofers. Besides affordability, a passive radiator to avoid port chuffing, these subwoofers offer a high pass filter for bass management. "Simply connect the output of your preamp or DAC to the Flex Sub, and then connect the line-level outputs of the Flex Sub to the inputs of your power amp". allowing the speakers to only have to handle frequencies above the cutoff point, a decided advantage. 

 

To the above, I've settled upon the Parasound Zpre3 Preamplifier, which besides volume control and numerous inputs offers a highly desirable remote that features Balance, Tone, Treble and Bass controls. I'm a fan of the Master Set Speaker Positioning System, which requires a balance control. Here's an informative post on employing the system. Here's a useful video: Master Set & Rational Speaker Placement; A How To For GREAT SOUNDSTAGE 

 

To my mind, this is an affordable priced system of separates for those of modest income with performance well above its price point.

Stellar!!  I’d just politely suggest changing the last sentence and the thinking it expresses.  In today’s world, only performance sets the bar.  Price reflects the cost of goods sold and the expected returns on investment of the designers, manufacturers, vendors, shareholders etc.  But it’s no longer a strict guide to objective quality.  Thankfully, even the crustiest audiophiles are starting to listen with their ears alone 😀

[bluesman]

1 hour ago, botrytis said:

That is a mistake when ears can be fooled so easily. One needs both, objective and subjective to make a good decision. 

I agree that there are many objective parameters to help guide the purchase, use, and enjoyment of audio equpiment and many other things.  But I have a bit of difficulty with the idea that any of them should supersede the subjective perception of the user.  The main matter of importance to me is enjoyment / fuilfillment / satisfaction / etc.  Specs, reviews, recommendations etc mean nothing if I don't like the performance I'm getting.  And if I'm happy, neither outside opinions nor cost will change it.

 

On the other hand, I think we all need to educate ourselves continually by experiencing what others believe to be greatness.  Both objective parameters and subjective impressions from others should cause us all to find and experience everything we can.  By trying everything, I've discovered a lot of wonderful stuff and experiences I either didn't know existed or might have otherwise dismissed because of everything from my own biases to bad press.

 

We can all up our games if we keep open minds and seek new experiences.  But if I like something, I like it even if someone has pulled the wool over my poor old ears 😀

[bluesman]

23 minutes ago, botrytis said:

 

This cuts both ways. Remember, just making a decision on listening, humans have a very small-time window which their hearing memory is accurate. If one listens and listens, then makes a decision, hearing memory is a bit mixed up. 

I’m just a tired old hedonist.  All ya gotta do is play me some music, pour me a wee dram, and feed me.  If I forget why I’m having a great time, it’s OK - I’m still having a great time!  😃

[bluesman]

3 hours ago, IQ_AV said:

@blues man Thank you for bringing attention to low cost high performing gadget such as the Douk.  As I was looking for headphonne amp, this one somehow popped up in Amazon.  I am delving into a headphone based system and without knowing anything, just purchased a Lavaudio DS400 and now thinking if can get the output from that into an decent amp, it might work fabulously. I did not see any headphone output for this and i am looking for a wired headphone.  Any thoughts on using this for my use case? Thanks, Ahmed

The ST-01 has no headphone out.  There are many very nice inexpensive headphone amps that do a wonderful job, in my opinion.  SMSL makes a few - I like the AD18, especially at the price.

 

As we begin to appreciate these things, their prices are rising rapidly.  I now see SMSL units for $400+ USD.   I’m now looking for new alternative sources around the world for great value.

[bluesman]

3 hours ago, bbosler said:

 

Your Benchmark puts out 100W. Most of these Class D amps are no more than 200W which is really a small difference considering it takes about 10 times as much power to be perceived as twice as loud.

 

There is no harm in having plenty of headroom

True dat!  But remember that class D amps do not use linear power supplies - so they don't need serious capacitors in there.  There's no storehouse of instant power for transients and peaks, which makes them somewhat compressed when pushed to their limits.  The RMS output wattage is not much below the peak output they can squeeze out for the cannons in the 1812.

[bluesman]

3 hours ago, Kal Rubinson said:

Generally true but not universally so.

But virtually all class D amps do use SWPSs.  It makes little sense to design and buld an efficient amplifier only to power it with a grossly inefficient power supply.  The non-sonic advantages of class D (e.g. low weight, little heat generation, and  small size) would be offset dramatically by a traditioal linear power supply with serious capacitance and smoothing / regulation that are unnecessary with class D.  This explanation from Rotel explains it well:

 

" The Switch Mode Power Supply (SMPS) is not what makes these "switching" amplifiers. As just described, the amplification stage is a high speed switching circuit and what defines this design as Class D. A Class D amp could, in fact, use a conventional power supply; and a linear amp could use a SMPS. A traditional power supply stores large amounts of energy, but wastes "excess" energy not demanded by the load in the process. An SMPS matches output to real-time requirements, supplying only the power required by the load, as a result operating very efficiently. The analogy is a water tank (linear supply), which is always being refilled and spills over if demand is insufficient; compared to an endless series of buckets (SMPS), which can be slowed down or sped up as required. The SMPS in our Class D amps reflects the fact that the Class D amplification circuit does not require the massive energy storage of a linear power amp, so the more efficient/compact SMPS is a better choice."

[bluesman]

26 minutes ago, bbosler said:

Audio amplifiers do not generally have a "grossly inefficient power supply." A traditional amplifier power supply consists of a  transformer, rectifier,  and a capacitor bank. The rectifier and cap bank consume a tiny bit of power so that leaves the transformer and  most transformers are well over 90% efficient.  

 

Compared to a switching supply, conventional power supplies as above are larger and heavier and more expensive, but they are not inefficient. 

 

The exceptions would be 

• regulated power supplies but power amps rarely have regulated supplies
• tube amps that use inefficient tube rectification, but that is not what we're discussing here. 

Most reference sources disagree with you.  Linear power supplies in class A and A/B amps are much less efficient than SMPSs.  Just look at the % of power input from the mains that makes it to the output stage.  Here’s a typical explanation from Cadence, in which they separate heat loss from other inefficiency for an unclear reason.  That heat is simply energy that came in as electrical energy and left as heat energy instead of mechanical energy in the form of sound.

 

“In summary, the disadvantages of linear power supplies are higher heat loss, a larger size, and being less efficient in comparison to the SMPS.The primary issue attributed to the linear power supply’s inadequacy in high-power applications is its size and weight. This stems from its requirement for large transformers and other sizable components in its construction. Aside from size disadvantages are the issues of high heat loss that present during the regulation of high-power loads. Due to its design, high output currents pass through the power transistor and the thermal stress requires heat sinks to dissipate this energy.”

[bluesman]

9 hours ago, bbosler said:

your analysis and conclusions are incorrect. "Much less" is relative, but the major loss of power from heat is in the inefficient class  A and A/B  output stages, not the power supply. Your "just look at % of power.. lost" statement is an incorrect analysis because the majority of the power that goes in but does not come out is given up in heat in the inefficient output stages, not the power supply. 

 

Please read my post again.  I said that the efficiency of the power supply is reflected in the delta between power consumption and power delivered to the output stage, not the speakers.  A traditional power output stage is definitely less efficient than the power supply that feeds it.  Criticism and correction are always welcomed, even if delivered harshly and in haste.  But accuracy is really helpful in preparing a response.  Thanks for your interest.

[bluesman]

10 hours ago, bbosler said:

All power lost is lost in the form of heat.

This is also not correct.  EMF generated in / by the device is also lost energy and is created wherever there’s electron flow through a conductor.  Transformers transform electrical energy into heat because of the resistance of their windings.  But the process of inducing current in secondary windings also loses energy to the very magnetic fields that induce those currents.  And the eddy currents induced in the core are another measurable nonthermal loss.

 

“Back EMF” is also generated in transformer windings.  This is current induced in the primary winding by the secondary, and it reduces efficiency by opposing the forward flow of current in the primary.  It is not heat - it is a pure electrical loss.
 

There are also non-thermal energy leaks in semiconductors.  Voltage gradients occur between internal components in chips, resulting in current leakage that reduces performance. Some of it does generate a tiny amount of heat, but the performance degradation is caused by deviations in voltages and other operating parameters.  The smaller the functional units (eg transistors on a chip” the harder it is to minimize these.  That’s one reason why CPUs consume power at idle with no internal activity.

[bluesman]

10 hours ago, Jud said:

THD+N spec for my SMPS front end Class D amp is 0.00017%.

Come on now, Jud - we can’t hear no stinking’ specs 🙃

 

Actually, I’m amazed at the dramatic recent drop in distortion specs on class D amps.  I’m very impressed with the SQ of the half dozen I have, the most surprising of which is that little Douk.  My main gigging guitar amp is now a Henriksen Blu 6.  It’s a 12 pound, 120W class D cube 9” on a side and is as accurate, clean and loud as any traditional amp I’ve ever used.  It amplifies my best carved archtops and other acoustics with amazing fidelity and has rapidly become the gold standard for jazz guitarists.

[bluesman]

55 minutes ago, PYP said:

Yes, exactly.  The luthier tries to remain loyal to his/her own design (say for an acoustic guitar) and therefore has decisions to make about the kind of pickup.  The choice is governed by what sounds true to that person's ear.  That decision influences how an amplifier is designed.  And so on, including when we choose equipment and then, often, tweaks.  Tweaks that may alter the sound of the equipment from what the designer expected. 

It's interesting to me how well this discussion now ties into those we had many moons ago about accuracy in reproduction of music.  I used as examples the different sounds of archtop and flat top guitars, and we discussed how different pianos of the exact same size, scale etc can sound , eg Baldwin vs Steinway vs Bluthner vs Yamaha etc.  Now we introduce the role of the sound reinforcement system, which is basically there for only one reason - to make the sound of the instrument louder.

 

Yes, many guitarists select amplifiers that grossly color or otherwise alter the sound of their instruments.  Distortion, phasing effects, delays etc are integral parts of the "sound" of many well known players like Pat Metheny, Mike Stern, etc.  But the pure sound of a fine, well made full body guitar like the gold standard Gibson L-5s, Benedettos, and DeAngelicos played by so many of the great jazz guitarists is prized for its beauty - and most of us amplify our "good" guitars only so they'll be heard in the bands and settings in which we play.  We want them to sound exactly as they sound unamplified - just louder.

 

Pete Henriksen has created amplifiers that are perfect mates for great guitars with tone no one in his or her right mind would alter.  They let the characters and the differences among them shine through whether you play a Campellone, a Benedetto, a '50s Gibson L-5 or Super 400, a Grimes, or a Dale Unger American Archtop guitar.  And they sound like themselves at any volume the amplifier will deliver.  That ain't easy!!

 

I finally broke down and popped the $1k a Blu 6 costs - and the 6 is the entry level amp from Pete.  It's so spectacular that everyone from the band to the audience came up to find out what I'd done to my guitar the first night I brought it to the club for our Thursday night jazz show.  It's truly accurate - those of us who know the sounds of the different guitars at this level can more easily tell them apart than from any other amplifier in my 65 years of experience playing the guitar.  Adn even though few in the audience or my band can identify the sound of a guitar by make and model, everyone can hear that there are differences - and that's where we left off our discussion of accuracy last time.