Class D Technology

Regarding the EE Times article, I took a look at some of the many patents that were issued to what was then the author’s company, JAM Technologies. It appears that most or all of their amplifier designs were intended for applications in which the amplification circuitry is provided with digital inputs, and operates exclusively in the digital domain until low pass filtering is applied to the pulse width modulated signal at the amplifier’s output.

Given that, the references in the article to jitter and to quantized output levels seem understandable, but along with the rest of the article would seem to have little if any relevance to class D amplifiers that are driven with analog inputs.

Also, JAM Technologies was described as a fabless semiconductor company (the word "fables" appearing at the end of the article is an obvious error or typo). Their designs appear to have been mainly intended for flat panel TV, PC audio, and personal media player applications, not for higher powered audiophile-oriented applications.

Some additional background I found that may be of interest: The company was founded in 1998 or 1999, and no longer exists. The author of the article was a co-founder of the company, together with another gentleman who was its chief technology officer and the inventor named in most or all of its patents. Both gentlemen left the company within a year or two after the article was published in 2005, and their subsequent professional endeavors have been unrelated to audio or consumer electronics.

Regards,
-- Al

@arafiq
I've had 3 different Peachtree amps (NovaAmp220, Nova 125SE, and Grand Integrated X-1), as well as a Parasound (older HCA-2003 model).  The Peachtree amps (with my gear, in my room) all absolutely sounded better than the Parasound.  Granted, the A23 is a much newer amp, so I might have favored that one over the Peachtrees, who knows?

@spenrock
I agree with your assessment of the Peachtree gear.  Their stuff is a great value for what you get.  They "punch above their weight class" you could say.  I have Peachtree integrateds in two rooms of my house with nothing but a Sonos and Altec Lansing speakers connected to each of them, and I'm not wanting more for these rooms.  That said, if you want to spend more, you can certainly get better sound.   These aren't reference systems.

I currently have the Nord One Up (Hypex NC500 based) monoblocks in my big system.  These have replaced the Peachtree Amp220 and immediately sounded more transparent and dynamic.  The new generation of Hypex class D amps are the real deal.  These amps use the same Hypex amplifier boards and power supply module that the Bel Canto 600m amps use, and they are a great fit in my system.  So far, these are the best of all amps I've used (10s, but not 100s).  FWIW I am using a tube pre (PS Audio BHK Pre), power regenerator (PS Audio P10), and large, low impedance speakers (Martin Logan Aeon i), all of which seem to lend themselves well to class D.  I'm very happy with the set up.

I owned the Devialet and it sounded very good, however, the Lyngdorf TA2170 with room correction is MUCH better and a very special piece. Check it out folks as it replaced over $15,000 in separates and sounds better. 

Hi seanheis1, amplifier designers modifying class D modules is largely an urban legend.... One of the few amp designers who has done this is Bruno Putzeys, who has made some minor modifications to his own Hypex NCore NC1200 for integration into the Mola Mola Kaluga amplifier that he has also designed.

Rather, Designers who utilize class D amplifier use an incremental design approach to their amp implementations.

For some entry level implementations, it is often possible to limit oneself to housing the power conversion module in a chassis and wiring it to output terminals.... If the module is of very high quality, such as the NC1200, or its NC600 younger brother, the results can still be remarkably good.

Some other manufacturers, such as Merrill Audio, do a thorough "passive" component design around the modules... They implement highly dampened chassis, highest quality internal wiring (e.g. Cardas), and I/O connectors: see for example the Merrill Audio Veritas monos that I have reviewed for PFO a couple years ago. In some cases, like in the entry level Merril Teranis stereo amp, they design custom input stages.

Finally, some manufacturers, like Rowland, utilize the Hypex NCore NC1200 models as component parts of sophisticated amps, where all but the power conversion module is a custom-designed component.... In the M925 monoblock, the power supply is a 2500W DC multi-regulated SMPS unit fed by a power factor corrected rectifier (PFC) where the generated DC is further "whashed" through Jensen 4-pole capacitors to eliminate any residual ripples. The inputs are coupled to very large Lundahl transformers to maximize common mode noise wrejection.... There is a lot more to the technology of the Rowland M925 amps in my own system, but I do not pretend to know all technical details.

Suffice to say that the resulting sound and music are too die for.... The amps are as quiet as can be, and the output is harmonically articulate, with no trace of grain, and certainly without any treble intermodulation that I would otherwise easily detect as harshness in split high string and high brass parts.

Granted, in general NCore amps, the higher end Pascal amps, and also the better ICEpower implementations are not likely to fit the requirements of the lover of triode designs who prefers a slight bloom in the midrange, a warm mid bass, and a gently tapered off treble.

Rather, these amps, once they are well broken in, tend to yield what I like to call a "goldielockian" musicality. In other words, a sonic environment that yields an even harmonic treatement to the entire audible spectrum.... I love it, but admittedly not everyone does.

Regards, Guido

e

Guido and others, the Lyngdorg is one such Class D design with other new and cutting edge technologies implemented. Best sounding amp I have had the pleasure of listening to. It is a dac, room correction, preamp, and amp all in one. This is indeed the future of audio and it is coming fast. I love tube amps and preamps. I love NOS dacs, I love vintage tone. This Lyndorf bettered all those other separates I still love. So Class D with other SOTA technology mixed in can not only be great, it can be stunning and best in class. 

Regardless of the technology used in an amp, Class A, AB, D, H etc... It is the implementation that counts. Yes, Class D is implemented differently with emerging SOTA solutions. So buckle-up Aphiles as we are in for a great ride. I will also say this to Class D detractors. Have you heard every Class D option out there in your home? No is the obvious answer. Leave room in your mind for  the possibility that Class D with its various implementations may in fact please you.

I am a believer now and was not about 12 months ago. I had heard several Class D amps in my home and in the end thought they were OK. Well Lyngdorf changed that with their particular implenmentation......for me anyway.