Introducing the Musical Design D-75D, an exquisite audiophile power amplifier.
D-75D design: Our original D-75 amplifier used three circuit boards - power supply and channel driver boards. This has been integrated into a single board with reductions of wiring lengths and mechanical/wire connections by comparison. The circuitry has changed too with single-ended front-end circuitry distilled down to a simple but very effective design using a unique Class-A Ultra-Linear Cascode driver stage. Our standard Musical Design D-75D employs a toroid power transformer, dual channel CRC power supplies with eight Nichicon Audio Grade power supply caps, eight Nichicon Audio grade capacitors in the CRC front-end power supply. The DC feedback loop also uses these caps. The MOSFET power output stage uses a single pair of devices which is the most pure way to construct an output stage. High quality Vishay/Dale resistors are used in most all positions. Our most basic version is a high-quality ‘build’.
What is “CRC”?: The power supply rectifiers convert the AC voltage supplied by the power transformer into a pulsating DC which refreshes the voltage to the power supply caps 60 times per second. Over that short period of time, 1/60th of a second, representing the charge-discharge cycle the capacitor will discharge somewhat because it is supplying the current to bias the power amplifier into a rich Class-AB operation while the diodes are ‘switched off’. That produces what looks like a ‘saw-tooth’ wave if you view it on an oscilloscope. The vertical dimension on the ‘scope’ represents the amplitude of a wave and the horizontal dimension represents the passage of time. Now here’s the technical trick. A second power supply cap is added but you don’t put it in parallel to the first one, rather you separate them with a resistor. That is the CRC, capacitor-resistor-capacitor connection. It is also known as a pi-filter. Now you see something more like a greatly diminished trace of a sine wave on the second cap. It is a far smoother and far more pure voltage in terms of switching noise, high frequency content if you wish. Yes, we use eight(8) power supply caps to accomplish this for the two dual-mono channels of the MOSFET output stage quite unlike most solid-state amps which typically using two or four power supply caps dedicated to the output stage. Expensive? Yes! Worth it? Yes!
So we know it sounds great, but what does CRC look like. Here is a sample of a MOSFET amplifier pulling 300ma bias current with a single 10,000uF power supply capacitor. Ouch, look at that voltage spike. The top two pictures are shown at the same scale. The final picture is to show a sense of comparison. Vertical is voltage and horizontal is time.
Now lets double the capacitors and have a look see. That looks better, yes? More capacitance equals smoother output. It doesn’t guarantee better sound since all capacitors are not equal in other respects. With the same quality of caps this is good.
Lets have a look at the Musical Design CRC. The input cap is in red showing a similar result to those above. The voltage of the output cap is the one on the bottom in green. Wow, the sharp peak voltage is gone and we have a nearly sine wave look. This looks and sounds a lot different, a lot smoother and silkier, plain better in every way.
Illustrations generated by the PSU Designer II Cad program from Duncan’s Amps. Actual measurements are very close to these results.
You stuck with us, thanks. Now what does this all mean.
D-75D sound: Yes, there are some moderate powered amplifiers that have superb sound quality, but they are mostly tube-type and always expensive. And yes, there are low priced, modest powered amps from some of the mainstream companies, but they sound modest. You know the sort. The D-75D is a new generation of amplifier with sound quality comparable to the finest products on the market, yet affordable. The D-75D is an amplifier with world-class soundstaging and naturalness. It has superb inner detailing, yet without edge or bite. Oh yes, sometimes live music can have an edge and bite, then those dynamic shadings are captured in a way that just has to be heard. There is a glorious ability to render the subtlest of shadings, while cruising through complex passages. The sense of naturalness with human voice is stunning. Subtle clues are revealed, that tell you something about the vocalists and the emotion they felt during the performance. In fact, there is always an exhilarating sense of emotional impact whenever the software can deliver it, and yes, in a system up to the high standards of the D-75D. Come to think of it, its sound is hard to describe just like the sound of live music. Listen for yourself, it’s an unbeatable bargain at twice the price.
D-75D Elite Design: We enhance the standard model in several ways. The Elite gets it name from the Elite parts which make it so special. Firstly, we have a quiet pair of toroid transformers. You’ll enjoy the superb connector array with upscale connectors including a rhodium IEC socket, gold and copper connectors. We use high performance, quiet resistors. High wattage wirewound resistors are found in the power supply. We employ great sounding Nichicon Muse Audio Grade DC feedback caps. We have found the Nichicon Muse capacitor superb in it's natural octave to octave balance and its open, dynamic freedom and frequency extension.
The Elite Sound: You will find that if you imagine the sound of the D-75D described above and then improve it in every way you have an idea of he capabilities of the Elite. It is especially superior in the sense of bass power and soundstaging. Soundstaging remains wider, more focused and open at even higher power outputs. It keeps its cool at higher sound levels leading to a sound like ‘it never clips’. It allows the music to achieve its full natural color shading unlike some ‘silk’ caps. In summation the Elite is utterly natural, clear, dynamic and 100% foot-tapping great. It’s a screaming bargain.
Elite Ultra Technology: The Elite Ultra is, well, ultra. It uses a costly CRC power supply like the other designs but with the unmatched Mundorf Black Titanium capacitors for the output stage. These caps are more than twice the value of the less expensive models with a total of 80,000uF for the output stage. It is then cascaded into a further CRC power supply utilizing Nichicon Muse power supply capacitors for the front-end stages. This is an amazing power supply design for any amplifier, much less an actually affordable product. We use eight superb Mundorf Black Titanium electrolytic caps for the output stage.
The great sounding Nichicon Muse KZ caps are employed in the additional CRC front-end circuit producing smooth, highly filtered DC voltage for the input stages with purely passive techniques. It gives you more true, vivid ‘tonal colors’ than a certain silk capacitor. The voltage here has no trace of the peaky saw-tooth noise you see in many front-end supplies. High purity, passively filtered DC means high-purity sound.
Takman CF resistors are used. They have a great purity and naturalness. The 3D soundstage and pinpoint imaging quality is a treat too.
Elite Ultra sound: The CRC technical details aside you get an even greater benefit than you might expect. The sound is much in the same family that you get from our Elite version, but with an added neutrality, smoothness, silkiness, dimensionality and a striking purity. The soundstage is even more solid and ‘locked in’. It produces wide dynamics without hesitation nor does it soften peaks. Bass is tight, clean, very deep and timbre definition is superb.
D-75D - $1295.00
D-75D Elite - $1995.00
D-75 Elite Ultra - $2495.00
Total Dual-Mono option: add second power transformer to standard D-75D for $200
Rated power: 75 W/ch@ 8 ohms, 20Hz-20kHz both channels driven, clipping power at 1kHz is 100W/ch @ 8 Ohms, 120 W/Ch @ 4 ohms Distortion (THD): 75 W/Ch @ 8 ohms, typically less than 0.05% Dimensions: 17"W x 11.5"D x 4"H
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