multiple personality microphone design?

I've been thinking about building a solid state large diaphragm capacitor microphone. Recently I saw the Soundelux ifet7 and it inspired me. Though it looks more like a U47fet, they also build a U87 circuit into it and you can switch between the two. Has anyone though of trying a DIY idea like this?
Kelley

Why not simply build two microphones? That topology- switching sounds like a sales-gimmick to me..

I second that. I always thought Millenias Twin Topo was a sales trick :roll:

The ifet7 a sales gimick? Not if you have a clue about this mic!
Different mic amps sound different, we all know that, hence the hundreds of types on the market past and present. Some amps are even better suited for different applications. We know the same mic capsule hooked up to different amps sounds different and again, excells in different applications.
If you know anything about the fet47 (which the ifet7 was primarily modeled after), you'd know it had frequency and dymamic issues that make it excell at some things and really suck at alot of others. You'd also know that most of the time these mics are purchased second hand by beggining recordists who find themselves extreeemely dissapointed that it doesn't sound like a U47 tube.
We found a way to build the classic fet47 (again, usefull only for a few things) AND a simple class A fet, closer to the 47 tube sound which now makes the mic much more usefull at a reasonable price. No gimmick, just maximizing the available resource (the capsule), increasing the aplications it can be used on.
Sort of like a very complex HPF/LPF/dynamic Range/tone changer/switch. You do understand the value of having some controls on mics, right? Why would having two amplifiers be a stretch from having a high pass filter?
So it really does use two entirely different circuits, one of which had never been available as a commercial product using the kk47 type capsule (the class A fet circuit has never been mated to the kk47 in any Neumannn product).
As for Millenia, I don't know and can't say, but the ifet7 was created to fill a need AND expand the possibilities!
Sincerely,
David Bock
Soundelux Microphones

Hello & welcome David!

I'd really much rather have two microphones than one with a dual topology. Any day. I'm sure the ifet7 is a wonderfull microphone though. YMMV and all that jazz..

Dave

Thats interesting a k47 capsule with a close to u87 circuit if I understand correctly and a fet47 circuit.

I assume the transformer is bigger than the tiny thing in a u87.

FWIW I kind of like a km84 circuit with a LD capsule adjusting the gain cap for the transformer size and adjust linearity of the fet gain stage.

I realy like to get the PET m7 gefell makes I think they call it the M9

Wow! I'm honored David Bock responded to a thread I started. I've only heard the highest praises about the ifet7, Fletcher is really into them as well as others.

But for me it's a whole different reason. I'm not exactly the fastest horse at the gate, it takes me a while to complete a project, but at least all my projects sound perfect when I'm done. So, I could either spend forever building microphones and never record anything or come up with a way to maximise my efforts. When I look at all that goes into making a microphone, correct me if I'm wrong, but it looks like the actual circuit is maybe about 5% of the effort involved. Making the chassis, (or would "body" be the proper word?), with all the hacksawing, filing, soldering together mesh, on and on, then put together what doesn't look like much more that a FuzzFace worth of parts for the circuit itself, the later is trivial, (I exaggerate when I use the FuzzFace as an example, so no flames please). Why cant one leverage all that hard work and just make room for a second circuit one can switch to? Of course there would be some extreme limitations, both circuit would have to have in common that they work with the same capsule and transformer, that, or can be tweaked to work so. Solving those limitations should be what DIY is all about? I mean think about it, wouldn't it be a nice thing to have a mic to do this provided it wasn't a gimic and both circuits were truely dialed in? I'm not suggesting cloning the ifet7, instead, coming of with a group DIY mic that added this level of versatility to a mic the DIYer has already slaved over by only increasing the complexity a comparitively small amount. I'm not saying that in the final analysis it's do-able, it may turn out that there's a sticking point, a show-stopper, like maybe only a special transformer has to be developed that's made of pure unobtainium, but before giving up on the idea as a gimic, why not toss it around for awhile before giving up on it. I'm sure it would have to be the best of solid state designs, I'm not suggesting doing this with two completely different tube circuits. Maybe a switch between a KM84 and a U87 or that Brauner schematic I saw earlier. Just looking at kicking around a few ideas at first.

Kelley

Whats wrong with a Fuzzface? :wink:

-Jay

When I use Gillette I don't have any problems with my fuzz face.
Kelley

I actually don't see any reason NOT to try different topologies in the same housing PROVIDED it's not your first mic building project!
BTW, the 87 and 84 are similar enough that you might find the sonic differences subtle, especially if you aren't using Neumann's kk87 for your experiments.
Concerning the xfmr in the ifet7 it is significantly larger than that used in the U87, and slightly larger than that used in the fet47.
regards,
David Bock

David,
Thanks for the advice. I've never built a microphone before, but wouldn't this just be an issue of getting the board layout right for the 2 circuits provided you have enough space. I do have a lot of experience with insanely difficult PCBs as that's what I do for a living and don't see anything about those circuits that would be a problem for me. Getting the capsules is a concern though, I've seen everything from $99 mics which include LD capsules, to the Pelusos at $150 to the Cactus by Blue at $400 all the way up to the one by Gunther Wagner for about $650, I can't find a source on the Neumann KK87 capsule. So I don't know which capsule to get when they all claim to be the best, does Soundelux sell just the capsule to the DIYer?
Kelley

[quote author="sismofyt"]
I'd really much rather have two microphones than one with a dual topology. [/quote]


Id rather have one mic with dual topology than one mic with one circuit, providing both mics we are speaking about are on an equal playing field.

I have a pair of U195's which so completely rule, its disgusting. I probably use them too much as it is, but I would *definitely* use them more if there was a mid rangier amp happening as with the ifet7. I certainly dont regret purchasing the 195's at the time, as thats what my budget would have allowed, but having used both the 195 and ifet7 (only got to use the ifet7 briefly though) I can safely say that my money would have went a lot farther with the ifet7.

Dual topology might be a "sales gimmick" if you are talking about a piece of shit with two modes, shitty and shittier, but when you are dealing with a quality piece of gear, whats the problem with it making two awesome sounds instead of one, provided both are awesome? I use the feedback and feedforward modes on an api 2500 pretty mcuh equally and if that isnt feature creep, I dont know what is... Ive often thought of putting a switch to select different opamps and transformers on output stages of my DIY stuff, its pretty cool when a manufacturer gives you this option.

I think if you are talking about some junky prosumer gear, maybe a bunch of features IS a marketing gimmick, but when you've got something that sounds awesome to begin with, please, throw a whole bunch of sound shaping options on that fucker just so long as it doesnt compromise the integrity of the original good sounding design. The sound deluxe Ifet7 fits that description as does the millenia EQ with the selectable amps that Ive used.

In regards to mic capsules, I got to hear peluso's capsules in a few homebrew mics and they are fully awesome and I mean FULLY awesome and most certainly so for the price.

dave

[quote author="sismofyt"]I second that. I always thought Millenias Twin Topo was a sales trick :roll:[/quote]

No trick. Twin Topology is two separate, selectable amplifier topologies. One topology is a transformless 350V vacuum tube amplifier. The other topology is a transformerless discrete solid-state amplifier. In most cases, the amplifiers are biased Class A.

The functional stages, such as opto-resistive elements or active filters, are shared in common by both amplifier stages. Fred (who I see is a regular around here) did the original TT circuit design circa 1997-1999, which includes the NSEQ-2, TCL-2, and most of the STT-1 Origin. Fred did a great job for Millennia, and I see he continues to design fine circuits. Fred makes note of his work for Millennia on his website:

http://www.forsselltech.com/forssell-MM.htm

The "Twin Topology" idea is not mine. To my knowledge, the TT concept was first introduced in the mid-1990's by Bruel & Kjaer with their type 4040 microphone. This microphone has both a Class A biased vacuum tube head amplifier and a Class A biased FET solid state head amplifier in the same mic body. An engineer selects FET or tube electronics, depending on the artistic or sonic goals. Type "4040" in their search engine:

http://www.dpamicrophones.com/

I remember seeing the prototype 4040 at an AES show (1994?) and thinking ?what a great idea for a mic preamp.? Some years later, I was talking with Wyn Morro who said that he was ?working on an EQ with tube and solid state signal paths and I?m going to charge $15,000 for it!!? Between Wyn and DPA, I became inspired to create our own version of parallel amplifier products, including mic preamps, EQ?s, and dynamics.

More recently, we?ve developed a product called the TD-1 ? a half-rack recording channel with Twin Topology instrument amplifiers (vacuum tube or discrete FET). In fact, we learned this week that the TD-1 was nominated for a 2004 TEC Award! You can see how the TT amplifiers are implemented in TD-1 here:

http://www.mil-media.com/pdf/td1-block-diagram.pdf

We?re also working on some other TT product ideas, but I?m not going to talk about those yet . I think David Bock did a good job of explaining the multi-topology concept from a mic makers perspective. I hope this clarifies ?Twin Topology? design and sheds some light on the subject. If you have other questions, I would be happy to address them.

By the way, I think this is probably the most on-target chat room in pro audio.

Best wishes,

And I think Mr. LaGrou has quite the spiffy avatar!

* Consul paces around singing, "There! Coming over Charaton Bridge..."

I agree. We are lucky to have the minds here that we do. I know I'm learning tons just from reading all of these posts and asking questions.

Welcome John!
Do any boating down the South Fork?
:guinness:
Been to Poor Reds!
:guinness:
Keep posting!

Man this place is geting better and better each day!
:guinness: :guinness: :guinness: :guinness:

[quote author="cjenrick"]Welcome John!
Do any boating down the South Fork?
:guinness:
Been to Poor Reds!
:guinness:
Keep posting!
[/quote]

We really like taking the kayak on Jenkinson, Silver, and Caples Lakes. Jenkinson is just 10 minutes from our house. Last river we paddled was the Rogue up near Grants Pass. Poor Reds years ago -- what a place!

Cool!
Your up 88 near below blue lakes I guess.
We do the Rogue every Sept.
Hit a few plays at the Shakephere thingy.
That was quite a fire near the Rogue a couple of years ago. Biggest in Oregon history.
I did some fishing on Caples. Very nice lake.
I will have a Gold Cadillac for you next tome I'm at Poor Reds!
cj :sam: