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Topic: What is inside the DPA MMP preamp?
Author Topic: What is inside the DPA MMP preamp? (Read 1994 times)
szegedin
What is inside the DPA MMP preamp?
I read somewhere that the DPA preamp (the smaller C version of which sells new for $359 and the transformerless A version goes for $509) were actually cheap and generic mic preamp circuits and 'nothing special.' Yet this preamps are the backbone of the current DPA 4006 etc, which sound second to none. It's the Bruel and Kjaer microphone capsules that are the magic.
So I have long been wondering what kind of circuit the MMP actually is. It's an electret mic. Has anyone here who uses DPA mics slid that thing open and looked at it? Could someone post a picture of the circuit?
DSatz
Re: What is inside the DPA MMP preamp?
I have no information about this particular circuit, but would merely like to point out what you're describing is the general situation with condenser microphones.
Capsules are at least 80% of what makes a condenser microphone sound good if it sounds good. Capsules are transducers, which straddle the acoustical and electrical realms, and their design and production has many complex, inherent problems. Manufacturing consistency that any $25 amplifier from Radio Shack would have (e.g. frequency response within 1 to 2 dB of design specification across the audio range, and any two samples being within 1 to 2 dB of each other) is a crowning achievement in capsule manufacture--and condenser microphones are the most consistent kind that there is.
Microphone amplifiers, on the other hand, soundwise, were essentially perfected in the 1960s (some would say earlier). All significant developments since then have been for the sake of practical features, reliability, new applications, etc., rather than sound quality as such. There are few remaining secrets to their design or manufacture; manufacturing tolerances can be within a fraction of a dB; plenty of companies and individuals can design and build them to fully professional standards.
Note that the people who modify microphones mostly work on the electronics; that's what it's possible for them to know about. And sometimes those modifications produce worthwhile results. But most people who try to modify and improve capsules, or who try to make their own from scratch ("how hard can it be?") end up botching it quite badly. There's this strange idea that it's an intuitive art, but in fact, even the earliest condenser microphone capsules were designed by physicists with Ph.D.s after extensive special research, and we're still not to the point where a capsule's design can be modeled on a computer workstation so that it sounds good when it's manufactured.
I'm not saying that it's a magical art or anything, but rather, Arthur C. Clarke's principle ("Any sufficiently advanced technology is indistinguishable from magic") applies here, and the requisite technical knowledge just isn't generally available. The know-how to design and manufacture really good-sounding capsules still includes some information that is tightly held as trade secrets. (An old friend from Schoeps has numerous anecdotes about the attempts by Chinese interests to woo him into telling them how to make good-sounding capsules ...)
--best regards
« Last Edit: July 13, 2019, 01:25:50 PM by DSatz »
music > microphones > a recorder of some sort
Quote from: DSatz on February 18, 2019, 09:09:15 AM
Microphone amplifiers, on the other hand, soundwise, were essentially perfected in the 1960s (some would say earlier). All significant developments since then have been for the sake of practical features, reliability, new applications, etc., rather than sound quality as such. There are few remaining secrets to their design or manufacture; manufacturing tolerances can be to within a fraction of a dB; plenty of companies and individuals can design and build them to fully professional standards.
So in other words... you don't know.
Kidding. Sorry, irony won't come across on the internet.
Appreciate the insightful comments. Funny you mention the Schoeps capsule. Recently I was looking at a picture of one of those (mk41) disassembled, and it's clear to see the difference in how it's built from those chintzy mics that use the same circuit, and people wonder why they are nowhere close to the former. And in the result, it's mainly the evenness of off-axis response that distinguishes it. On paper, anyway. I use one.
I mostly agree with your comments, although I wouldn't say that anything about mic design was 'perfected' by the 60s, so much as it ran aground and hasn't developed. But needs to. I still feel that the best microphones fall woefully short of human hearing as we experience it - in terms of sensitivity and dynamic range. [Of course, the inadequacy of the loudspeaker transducers share equal blame]. Generally I'm not impressed with mics. When you think about human hearing, and how there are thousands of cilia that each resonate on a very narrow frequency band, and then that is summed.... When that kind of mic is developed, I will open my wallet. We've got to get past this thing about some plastic stretched over a disk.
As for the electronics, I think the only development I would point out is that there are some now that are much, much quieter. That CAD with four FETs on the input stage... whatever that means... with it's very low noise spec, and others. The low noise thing matters a lot to me. Certain kinds of recording require microphones that amplify very quiet sounds to a reasonable approximation of how things sound to the human head, and for that, they are not even close to good enough yet.
As for the DPA, it's probably just hard to open the mic. Like I said, it's not even a good preamplifier, but I'm interested to know what they are using, or getting away with using. And as for the Chinese, they have actually cracked the code of the DPA capsule.
> So in other words... you don't know.
No offense taken! That's my kind of humor as well.
_Many_ years ago I had lunch with the then-chief engineer of Schoeps (Jörg Wuttke) and Schoeps' then-U.S. representative (Jerry Bruck). At some point in the conversation, Jerry asked Jörg about developing a special version of some product--maybe a capsule. Schoeps is generally willing to consider such ideas, but this one crossed the line.
Jörg began to reply, but then decided that he should be more careful with his words. He asked me if he could reply in German, and I would then translate for Jerry. I agreed to do this.
So he described in some detail the time and cost requirements for product planning and development; the risks that always have to be taken when introducing any new product or product version; the extra investment in tooling for producing unique, new parts; the unwanted side effects of added complexity on existing production, marketing and service arrangements; the costs of stocking a new product for which the future demand was completely unknowable. Nothing that he said was news--but he really tried to paint the complete picture.
All in all, I think he took maybe four to five actual minutes of non-stop, well-thought-out German prose, and by the time he finished speaking, the subject had been thoroughly covered. Whereupon I turned to Jerry, and all I told him was, "He said 'no'."
Of course then I backtracked and relayed the whole reply to Jerry--but first I couldn't resist the practical joke.
Gutbucket
record > listen > revise technique
Ha! Great story, thanks for sharing it.
Working in manufacturing (not audio related) I can relate to the complexity required to develop, build, sell and support a product.
musical volition > vibrations > voltages > numeric values > voltages > vibrations> virtual teleportation time-machine experience
Better recording made easy - >>Improved PAS table<< | Made excellent- >>click here to download the Oddball Microphone Technique illustrated PDF booklet<<
ThePiedPiper
DSatz, Thank you for sharing that! Very funny story. I have enjoyed and learned so much from you and Gutbucket. The two of you should have your own forum.
ycoop
Quote from: ThePiedPiper on February 28, 2019, 01:59:36 AM
My vote is for a podcast.
Mics: Avantone CK-1s, AT853 c+o
Pres: CA9100
Recorders: DR-60d mkII, DR-2d
Quote from: ycoop on February 28, 2019, 03:13:42 AM
YES!!! We could start a GoFundMe and finance it for them. I would listen!