Mic Debate.

  • Thread starter Thread starter shoggoth80
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I personally would like to know more as well. I find all kinds of mic mods... but no detailed explanations of how some of the stuff is done.
I read about Capacitor swaps, but don't get much info on what types of capacitors to grab, how many to swap. I read about transformer swaps, but there are a number of transformers, and the hot one is pricey, but I would use it in a heartbeat if it worked, and I knew how to swap the part out etc. I have also read about capsule swaps... Peluso being a popular one. I even looked into the price of nice capsules. Makes me wonder if it is possible to custom roll something between components, and finding a mic that I could rip up for the body just to stuff a custom build into? Perhaps I am getting far too deep into this? Lol. Like a Peluso "Neumann" capsule, with a Royer tube circuit/mod board. Or maybe that capsule with the Dorsey modded circuits? Don't suppose there is any place that will just sell me a mic body, XLR out, and a decent windscreen? Lol.

Also, wondering about Ribbons? The MXL R144 in particular. It sounded nice from demos I have watched. My tube pre goes up to about 75 db gain... and my interface could add a little more if needed. Viable for vocal and guitar work? Or too fragile?

Information overload on some areas, and not enough information from others. I know that soldering stuff together isn't too difficult. With a set of instructions, and decent components, anyone should be able to acquire enough skills to piece something together. Lol. But I am a tinkerer by nature, and at least somewhat mechanically inclined.
 
moresound said:
Come on!!! not even a clue? You just can leave me hanging here Phil.
Click to expand...


Clues I can give you. Direct information? no.

Some real advise I can give is that I prefer to build point to point now days. If you're going to etch your own circuit boards, then you need to pay attention to how the traces are laid out. Remember, this is a high impedance circuit. There are also issues regarding paths for traces. The other direct advise I can give is to be careful when soldering a directly connected tube. Heat can cause leaks and can damage the tube in other ways.

Clue #1: Is the Jensen direct box transformer, or even the Cinemag 2480 the right transformer for the 5840 given the Rp of the tube at 100v. Both would work with a 12AX7 or similar, but with a 5840? They can, but its not ideal. What about the overload point? What about the choices for the core material or bobbin configuration? Those are also things to consider.

Clue #2: look closely at the input stage of the tube for the Royer mod coming from the capsule if you have the schematic. Compare it to other classic mic circuits. David has his theories for why he did it that way, but there are potential problems with it. If you look long enough and research it, the answer will hit you. It can also be taken to extremes that (in theory) are better, but as far as sound goes may not be as musical. Some of the "gurus" on the web have gone this route, but I'm not sure if they really listened to the results. Maybe they did. Its really personal preference.

Clue #3. Look at the voltage divider and capsule bias points. Part values could be better calculated, and can be adjusted based on the capsule type. Like I said, David based it on off-the-shelf parts. The more proper components have to be ordered and can be costly, but they make for a markedly better head amp. This can affect both noise and low end response.

Clue #4. I don't like how he's biasing the tube. Just my personal preference, but it can be improved.

Obviously, using the stock capsule can have pros and cons depending on the application the microphone will be used for. This will make the choices for the circuit vary if you decide to change the capsule. Same with the grill.

Other things to consider, like how to solder and clean up. How did you handle the components? What type of wire should be used and where? Did you check all components for microphonics? How should the capsule wires be allowed to pass through the grill's base plate? How should the capsule wires junction to the circuit board? What should the value and type of capacitor be at the coupling and decoupling parts of the circuit? Depending on the capsule type changes to the circuit can be made to reduce brightness with some capsules. With other capsules there are ways to modify the grill to boost or smooth high end response, but those can also have adverse effects on low frequency.

With microphones there is stuff besides just general electronics to consider. For a home build project his mod is a good start. It just depends on how good you want it to be.

I wish I could just hand out the answers, but the experts in microphone technology have earned the right to keep this info somewhat under wraps. That's why they are the experts and are trusted with these precious instruments. Its a craft and art and they are musicians in their own right.

And by the way, if you research stuff on the web, DO NOT listen to every bit of advise as though its true. There's a lot of misinformation out there, especially among user boards. There are folks who are talking like they know about it, but really don't. They may understand electronics and how it relates to common electronics, but microphones are a little different. After a while you'll learn what's true and what isn't.
 
Ah yes, the guild model of economics. Unfortunately, it works very poorly when those with said knowledge produce so little that it's largely irrelevant to the market. And that's a shame.

The world's supply of 5840s and other long-out-of-production obscure tubes won't last forever, so this knowledge might as well die with its practitioners.

Don't get me wrong, I don't particularly want to see all of this copied by China for free, but they aren't likely to branch out into the field of NOS anyway. But seriously, this is like "I have all this secret knowledge I won't tell you so you can't build your own, and oh yeah, the people that know it for the most part don't produce any microphones, unless you know somebody they know, and even then you have to beg them really nicely." Who cares? Not me.

Before you think this is sour grapes, note that I am exiting the mic business myself. But in the world of preamps I have competitors that epoxy their circuits. I publish my schematics . . . and they still can't match my product line because I have efficiencies unrelated to the circuit itself. China could by brute force, but they ignore tiny small markets . . . for the time being. Just like they didn't used to bother to produce $50 pairs of mics from stock electret capsules . . . and now they do.
 
I understand your position John, I really do. The fact remains, however, that I was specifically asked not to give the information I've learned out. I have a friend who's very well known in that field and he agreed to mentor me under the agreement that what he tells me is "for my ears only". I do so to protect his livelihood. The same how it was with the person who mentored him and he eventually took over the business. I have another friend who also likes to call and talk shop, but his position is the same. Earn your stripes. If someone digs they can find it. Its not like its too hard to see some of it if you just look. They only started telling me this after finding out how much I've learned on my own. The things I can divulge from my own discovered knowledge I will.

Example: Hey folks, you really need to super insulate the leads from the capsule going through the grill base if it's metal. Teflon or glass grommets work really well. Also, Teflon insulated standoffs should be mandatory on the circuit board, especially where the grid from the tube connects. Oh, and if you can..heat sink the wires from the tube as you solder. And insulate, insulate, insulate the tube leads!

There. How's that? ...Not like anyone examining a well made mic wouldn't notice some of these details, but they do indeed affect the performance of the mic.

Keep in mind, I do NOT make my living out of this, nor do I intend to. When I do a mod for someone its usually because I want to, and I don't charge as much as I should. I'm learning this stuff purely for my own interest. I'm not starting PhilGood Mods®. In all honesty i'm trying to make really good mics for myself. Do I mod on the side? Sure, if someone asks and I have time. i have a full time job and a family, plus a band. I ain't startin' no mic company. I am trying to protect the interests of my friend. If that makes me a bad guy, then call me Dr. Evil. I don't care.

As for tubes and the future, several new manufacturers for tubes exist. There are even unconfirmed rumors that Oliver Archut has the machines for making the original AC701 tubes and may go into production. Just something I read, but who knows.
 
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Tell you what, John. You're a very smart individual. Look at my clues and see if you can provide the answers. Then neither of us have broken the rules and the info is available. I know you'd be able to digest the info and respond with the right answers. Let's see if we can do this. We can PM each other with more questions and clues and see if we end up at the right spot.
 
I'm not saying people should disclose proprietary info, but you don't have to taunt people with it either. Look, about 10 years ago it was common for me to get insider info that could have made me or my associates very wealthy, if we wanted to risk the SEC sending us to prison. You just don't talk about it at the time.

As for me, I just ask myself, WWHD?

And for your clues, no thanks, I don't do anything with 5840 or mic mods in general. I got a commission to do a custom 6418 mic though, haven't done those in a while but I like tubes that don't need their own power supply. This time though I'll have current draw down in the 1mA range :) There is no great mystery how, after I published the MSH-4 schemo zapnspark did a charge-pump version for the filament supply and published that as well. My latest approach is somewhat different, but the concept and results are the same. I would guess that several dozen people have built some version of the MSH-4, slightly fewer zapnspark's Frankentube--people get intimidated by charge pumps since most of the ICs are SMT. I wouldn't mind using one in every mic I did though, since the efficiency is so much better than linear regulation.

And I would like to see development of microtubes; tube development ended with the subminis and that was a very long time ago. There is no reason to be consuming watts for small-signal stuff. If I ever get really bored, I'll work on that :)
 
Aaaaaaaaaaaagggggggggghhhhhh! Lol.

Ok, after a bunch of researching, I think I nailed down what I want to do.

I have read a lot of nice things about the MXL 960 model. I like tube stuff... mostly, I miss my NTK... buuuut...
I figure if I take the MXL 960, toss in a Peluso capsule, and upgrade the tube... that ought to get me well above the price/performance ratio, have a very nice capsule, and still keep that nice tube sound. For less than the cost of just buying another NTK mic.

Oh... does anyone know what the body is made out of? For some reason, I think having a steel toned grill support, bare brass center, and steel bottom cap would look pretty tight. I mean, if I am gonna mod this thing to my own tastes, should that not also include appearance as well?
 
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