Bonsai said:
Well, if the resistors are really that good, they could follow the Vishay model. Vishay only used to make super-precision resistors for the aerospace and instrumentation markets. They were $5 to $10 each. They made enough money selling these resistors that they now own 28 other electronics manufacturers!
http://www.vishay.com/company/brands/
But maybe the silicon resistors aren't really good enough to sell for $.50, let alone $5....
I don't like high feedback regulators applied DIRECTLY to amplifier stages. I always use an open loop cap multiplier equivalent buffer between the IC power reg and the amp stage. I didn't know this 35 years ago, when I designed the JC-2, I just 'lucked' into it, when buffering studio board stages from each other. That is how the Wilson Audio master tape recorder electronics were designed, and the Crystal Clear studio board, among other projects. Please consider that I use vinyl records made from these companies among my reference sources, just to have a more complete chain of high quality electronics from source to speaker.
These 'suggestions' much like: "Eat an apple a day, and keep the doctor away" are learned by experience and often by accident, and are often scoffed at by the 'typical scientists' of the time period. In this case, some engineers on this thread.
These 'suggestions' much like: "Eat an apple a day, and keep the doctor away" are learned by experience and often by accident, and are often scoffed at by the 'typical scientists' of the time period. In this case, some engineers on this thread.
Charles Hansen said:
That would be the AD846/844?
I'll check on that link.
Edit: interview with CH on Ayre website
Jan Didden
Nothing to really add, but some FYI on National. Their sound room dates from the early 90's. This is when the Overture parts were being developed and coming out. They didn't talk as much about it then. They talk about it now because all the new LME parts are targeted more to high-end audio and listening is as or more important than bench testing for this market (as demonstrated by many on this board). The guys there are usually pretty open to doing listening test with others and any other equipment and music selections one might want to bring. Course, you have to be someone who brings some potential business opportunities, they won't spent a lot of time with just anyone off the street. Those with real opportunities can probably call and get a visit from some engineers who will bring amps along to evaluate.
-SL
-SL
There's no excuse anymore for that preamp to take off. 
http://www.diyaudio.com/forums/showthread.php?threadid=115727
/Hugo
http://www.diyaudio.com/forums/showthread.php?threadid=115727
/Hugo
janneman said:
The 844. The 846 was discontinued many years ago. Since then several others have used the 844 in a similar way. If you do a search under the Digital forum for "AD844" you will see some of the basic ideas. However, there are some subtle problems with those designs that we have overcome. I'm told that Krell also used a similar approach with the AD844 in some of their products also, but that information is third hand and may not be accurate. (It wouldn't surprise me, as they have followed our lead in many areas -- now they are bragging about their zero-feedback preamp, although they still haven't figured out how to make a zero-feedback power amp. They claim 8 dB of feedback, and only around the output stage if I recall correctly.)
Here is the pertinent text from the interview:
"We are now using ICs (integrated circuits) in some of our less
expensive products designed by Dr. Barrie Gilbert, one of the
"godfathers" of analog circuit design. Now, it’s very important to
differentiate between the terms "integrated circuit" and "op
amp" (operational amplifier). We’re using integrated circuits,
which simply means that there are many transistors created at
once on a single piece of silicon. An op amp, on the other
hand, uses negative feedback as its fundamental operating
principle. You cannot use an op amp in a zero-feedback circuit.
The topology of the IC we use in the less expensive products is
very similar to the topology of our discrete circuits. We've figured
out how to implement these monolithic ICs with zero feedback.
By using two of them together, and modifying their characteristics,
we can get within spitting distance of the performance
of our discrete circuits at a much lower cost. The critical
advantage here is that the monolithic design of the IC means
that all of the transistors are matched extremely closely. In contrast,
with our discrete circuits we have to spend a lot of time
measuring, sorting, and matching transistors, which translates
to a more expensive final product. By using an IC in a way that
hasn’t been done before, we’re able to achieve a real breakthrough
in performance at a real-world price point. It's great to
make an all-out assault on the state of the art, when the only
limit is your imagination. But the real challenge is to bring those
lessons back to the real world where more people can enjoy
the fruits of our labors."
The "breakthrough" I referred to was one of performance versus cost, and not simply of performance. That has been my stance all along. In my original letter to Stereophile I specifically criticized $15,000 preamps that used only op-amps. In the case of the Ayre products using IC's, they sell for 1/5 of that price. Furthermore we use them in an original, unique, and innovative way that provides sound quality far beyond what they are normally capable of.
Also please note that interview is five years old. As mentioned, we have since developed circuits that outperform the circuits we were using then. One of the main benefits of using IC's is simply to save money. I'm not sure that we would still use IC's in a product at that price range any more. On the other hand we are looking at introducing a product with a target price of $1,000. We may (or may not) resort to using IC's in that product in order to keep the price down. (Naturally, this would still be in a zero-feedback configuration.)
I hope this clarifies things for you. If not, feel free to ask further questions.
luvdunhill said:hmm.. an Ayre electrostatic headphone amplifier? I'd be interested in more like 800-1500 V swing myself
For many years my transducer reference was a pair of Stax SRX Mk II's. Lovely, lovely sound.
One time I took a pair of RTR electrostatic panels and hooked them up to an old DuMont tube 'scope I had. There were connections on the back to access the deflection plates. It had identical X and Y channels so it was perfect for stereo. Think about it -- all triode, zero feedback, fully-balanced, fully regulated (by tubes, of course) and direct coupled to the electrostatic panels. The sound quality was absolutely insane!
In the real world, the first design by Jim Strickland (Acoustat) had a direct-drive amp with a HV tube output stage. It received mixed reviews, largely because the front end was a 301 op-amp with high feedback. The transparency of that system sure let you hear how bad the op-amp sounded!
For a while there was a company that made a new (tube-based) front end for that amplifier. I never heard it, but reports were that it transformed the sound into something quite magical. They didn't last long, as only a handful of the original speakers were ever sold.
By the way, if you are into electrostatics, check out an article from Charles Malme in the AES journal from '59 or '60. He figured out a simple way to solve one of the chief problems of electrostatic panels. To this day I am shocked that it has almost never been used. (Acoustat borrowed this idea for their "SPECCTRA" design shortly before they went out of business. I don't know if that speaker ever even went into production.)
Bob Cordell said:
Not based on what you heard from the Halcros, eh? Okay, so we'll delete the two paragraphs you spent extolling the wonderful Halcro dm58 as having mysteriously appeared out of thin air, attributable to no one. Good. That simplifies things since we've cut out roughly a quarter of your letter. It also removes that rather inconvenient 'high sonic quality' comment. Paragraphs gone. No harm, no foul.
On to the next thing: 'Actually, glass capacitors (silicon dioxide or silicon nitride) are very, very good.' On what basis are you making this statement? Can you give me some numbers to look over? Also, while we're at it, are those numbers on stand-alone tests of the passive components in question, or are they in situ with parasitic effects from the rest of the circuit included?
Resistors also, please.
Actually, it occurs to me that the parasitic effects will change from chip to chip, and from passive to passive within the chip, depending on where in the circuit the component in question happens to be in relation to other components, both active and passive. With that in mind, it might be helpful to specify exactly which resistor or capacitor in which chip, so that we can judge how representative the specifications are. For that matter, we'll also need to see the etching masks for the chip in order to judge physical proximity to other components, as the schematic alone will only hint at this.
Granted, there are interactions between components in discrete circuits, but I think everyone will agree that the distances involved (which can be controlled by the designer if needs demand), coupled with the inverse-square law, will render them many orders of magnitude lower compared to passives in chip opamps.
Claims that chip-process passives would be too expensive for the market are questionable, at best; a deliberate red herring at worst. One of the reasons chip fabrication is expensive is due to the micro scale necessary. Once you go macro, your costs will drop significantly.
Keep trying guys! Give 'er all you've got! You've made such bloody damned nuisances of yourselves in other threads that I really can't say that I'm pulling for you, but I'm willing to give you a sporting chance. Given all the spurious B.S. that you heaped on Charles over his letter, I think it's only fair to hand a little back to you. After all, fair's fair...right?
If it gets too deep or difficult, an honest apology to Charles will be considered "crying uncle" and I'll let up.
Grey
- Status
- Not open for further replies.