DJS

Yes you have me on the ropes... everything shown are customer requested retrofits, not part of the original design of that DAC model.... A USB input and latter model volume modules added to a previous generation DAC as a retrofit, the dac shown has at least three generations of modules in it indicating a long upgrade process for that customer... That particular DAC shown even needed a retrofit to the motherboard power bus (wires in lower left corner and to the left of the blue board) to support the excess power required for the late model DSP (blue board). So lets see its a 2007 motherboard with 2008 volume module in it, 2009 DSP module and about a 2011-12 model USB input. Most companies would tell the customer "sorry you can't stick this new hot input or that newer model volume control in your old outdated model, buy this years model instead." We have always tried to make customers happy by retrofiting old product if it was possible. In fact the previous owner made it company policy, if we could upgrade a product then we would upgrade it no matter how difficult or hacked the upgrades were. I used to strongly disagree with him about these messy "hacked" upgrades but after he forced me to talk with our customers directly about what they wanted I did learn an important lesson. Yes one offs and retrofits require hand work and "mess" but they make customers happy (as long as they work well, which with some of the mandated "upgrades" wasn't always the case and definitely results in angy customers) because they get what they want without having to re-buy a product every time the fast moving technology changes. I have learned the lesson that customers want a long life span out of their products so well that at this point that all of our lattest products contain obscenely flexible hardware to keep all the hand retrofits to a minimum wherever the technoloy wind may blow. For example the lattest DAC modules are built of software defined analog blocks so that they can be configured on the fly as multibit, multibit delta-sigma (8-2bit) or single bit delta-sigma and support sample rates from 44.1khz to 98Mhz. Another example is an input module design that supports any digital format up to 300Mbps (for example 12 channels of 32 bit/768Khz pcm) with an electrical and thermal design to 12W per module to support most any interface from simple s/pdif to the latest full blown multichannel network computer endpoint. All of this is probably overkill but may tun out to be necessary 5 years from now. I will also say that all of my designs have also much improved with time. My first product design was the MSB Link DAC and even tho most customers loved it I now view that design as naive, overly complex, underperforming and formulaic. When I had the chance to redo that design years latter I did it on a busness card sized PCB with a total build cost of $4 and we gave it away as "swag" at a couple of trade shows. The recipients may not have realized it at the time but that silly "buisness card" DAC was much superior to the Link DACs they may have already owned. However my lattest designs, for example the Select DAC, I find satisfingly divergent and polished with circuit design maximally refined, simplified and unique. And now I'm tired and feeling antisocial after such flames so I won't be continuing this argument. I respond much better to direct questions rather than sarcastic inuendo like that above. I thought that maybe there was some open minded people out there that might be curious to know what is really going on with a product that none of them will ever be able to afford (myself included, I only get to have temporary loan of prototypes for testing). It seems if I design something that breaks established convention (with specs, design whatever) established designers feel that I stepped on their toes or invaded their private domain and require a "whipping." I learned my lesson this time, I don't think I will ever try post any useful information again, I will just let the flames roar in the vacuum.

I never said the amp would blow up, yes if you coupled 100Vrms into the input you may damage the protection devices or overheat the input transformer but I doubt any sane person would connect it up to a power amp or power line on purpose... clipping produces objectional distortion so I choose to have that be impossible in system. Look, I have no intention of any markting BS. MSB makes less than 1% of our revenue on products other than DACs and OEM contracts. I only step up to the plate to design something like an amp when all the avalable products are difficient in one way or another and we have need of it. I have zero interest in lying about technicalities. Yes a calibrated metrology KVD is the worlds highest performance 1000v amplifierless DAC but that fact alone does not make it suitable for music reproduction. Tossing hypotheticals about does not change reality. I must say that you seem very defensive, did a grandkid poke you in the eye at Thanksgiving dinner? Flames usually accompany smoke, do you have something to hide? Nothing I posted was inaccurate so I don't believe I deserve being called a FOOL. BTW when is any electronic component off the table when a designer sets down to design a product? Every DAC we sell has multiple transformers throughout its circuitry. RF transformers isolate external data busses and impedance match clock transmission lines, micro transformers do level translation or isolation for voltage islands, power transformers are used to generate power supplies, MF transformers are used for DC to DC converters, ect... The only drawbacks to designing with any transformers in my view is cost and size, they tend to cost more than any other circuit component and consume more space so I usually attempt to design them out of products that have a low cost BOM constraint or size constraint. My view is that a designer should test and choose the best architecture and componets that fit the relevant design constraints, not reject possibilities out of hand because of some irrational belief or fear. Just because a box has a transformer in it disqualifies it from being called a DAC in your view? I'm curious for you to explain your position on this... Obviously I can stand the heat or I wouldn't have a product... Being terrified of being caught in a line and being dragged into a storm has never stopped good sailors either... fear is what keeps people cautious and alive.

I am a designer with MSB and I will not get into an argument with anyone about value or sound quality which are highly subjective parameters, but I do want to clear up some technical misconceptions about this electrostat amp. Fist Kevin is correct about one spec being wrong, our website is new and there are likely some more incorrect specs as well. The frequency spec should read 5Hz-20Khz +-0.8dB driving one Stax SR-009 at 100Vrms. This is mostly due to the amps 6500 Ohm output impedance driving the low Q capacitor of the headphones. Also from a normal designers perspective the 75 Ohm input impedance seems like a bad choice, but this amp was designed to only be used with the Select DAC so this amp forms an optimized circuit with the amp. As the designer I prefer to think of it as a super high output voltage DAC that happens to be housed in two boxes. The other specs are correct but slightly conservative. The dynamic range is actually closer to 144db (20Khz bandwidth) because the amp only has a 3dB NF but any particular amp could have a slightly slightly variable PSRR or slightly less effective input transformer shielding which could lower the dynamic range a couple of db due to a slight excess of 120Hz or 180Hz noise coupling from surroundings. When noise floor reaches the nanovolt level (the input stage) even the orientation of a wire can couple excess noise into a circuit so I like to publish conservative specs that don't reguire a farady room to reach. Distortion at 20Hz 300Vrms is limited by the input transformer to 0.05% but by 100Hz that is down to 0.001%. At 1Khz 50Vrms THD+N reaches its minimum measured value of 0.0004% (probably the limit of my AP test system) then slowly increases to 0.02% at maximum output of 440Vrms (mostly 3rd harmonic). This is intentionally limited by the maximum DAC output so that the amp circuitry cannot clip. Distortion to 20Khz remains esentially unchanged from that measured at 1Khz. Most of the semiconductors are mounted under the PCB with heat pipes carrying heat to the heatsinks. Heatsinks on this product are full depth without the hand pockets of the Select DAC to facilitate the additional power dissipation. Static power dissipation is about 60W which is close to the maximum comfortable heat dissipation for the Select chassis. To get the 120db of power supply noise rejection required there is a three stage regulator and noise filter. The numerous capacitors are elements of the three stages of regulation. The amp is a zero feedback design because even tho feedback reduced the THD at full output considerably, lowered the effective output impedance, and flattened the frequency response at 20Khz it also reduced perceived sound quality significantly so I decided to omit it. I feel the measured specs are plenty good without it and as a benefit the amp is unconditionally stable with any load. As a side note the more than 140db of dynamic range was a happy surprise. I was shooting for 135db or better. Also prototyping a HV amp or power supply like this is terrifying, especially with modern miniaturized components, a mistake or slip means more than an Amp at 600Vdc stopping your heart. PCB and case design is no joke either if you want a safe error tolerant design, every three dimensional leakage path from each component to nearby components has to be considered.