UM57/ CMV 563 sound so boring, whats up?

[jrmintz]

Perhaps they arent totally colorless but they dont AT ALL inspire any kind of microphone lust when you use them, no excitement at all.

That's how I usually feel about U87s - they're always fine but rarely exciting.

 

[tommytones]

Its my prediction that in the future, maybe 15 years from now, but the future sometime, there are going to be a lot of people going through this exact thing.

Ya, I agree. Although, I'd venture to say it's already happening now (you're a good example :green: ). This is why I always tell people who ask me for advise that they really need to try the mic and inspect it before plunging in and dropping a load of money. Especially when it's an old mic. You don't know where this thing has been sitting and what kind(s) of abuse they've been subjected to. Case in point, someone I know just bought a mint condition u87 without seeing it or listening to it and guess what...I opened it up when he brought it to show me and the only thing related to a u87 left in there was the capsule...at least I think...

The way I see it, I don't hesitate to rebuild or mod old gear if it's gonna be something I know I'm gonna use a lot. The whole vintage value thing becomes irrelevant at that point because chances are I won't sell it untill I retire or go broke (which ever comes first :green: ). In the case of these mics, I personally have 2 of them which will certainly be worked over.

 

[Gus]

Dave

I would measure the lams and size of the transformer add replace with .014" Mu lams if possable or call cinemag and see if they make or can make a replacement. IIRC the 47 uses a 6.5:1 so I would guess that the 57 was 8:1 to 10:1 because of the tube used. This is strapped at 200 ohm out

I have been looking for a stock type transformer for a tube microphone power supply Hammond makes some that are close : however the fils all tend to be 6.3VAC we need >9VAC 12.6VAC would be fine for the fil regulator circuit.

I have some ideas about what you could do with the circuit in that microphone if you don't care about the vintage stuff. You got a M7! and a OK to good body grill, I have not worked on a UM57 so I don't know for sure about the grill and body.

I have some Ideas for older u87s

 

[jrmintz]

I have some Ideas for older u87s

Hey Gus, had I known about this place or the possibilities for improving stock gear when I got rid of that U87 3 or 4 years ago, I'd have been dying to know what you have up your sleeve. Maybe I'll keep my eye out for another one. I always thought the U87 almost sounded great, but never quite achieved it. I feel the same way about every piece of M*nley gear I used to own. Don't miss any of it.

:thumb: :thumb:

 

[soundguy]

hey gus-

Im just airing ideas, when I get time to work on this, maybe in march, Id love to get into details with you. I dont have a um57 but two cmv563's. I think they sound similarly poor for the same reasons which is why I lumped them together, I dont know if they are the same circuit at all but the ones I have heard sound equally inefficient in the same kind of way.

dave

 

[neilium]

A modified vintage mic is still a vintage mic with an unobtanium capsule, and it would be a star on any studio's equipment list. I can't imagine it losing that much value because you swapped out some parts that could be swapped back in.

-neil

 

[Guest]

[quote author="Gus"]I have not seen one: however the microphones use negative feedback from looking at the schematics. The "bottom" of the transformer primary goes to the cathode of the triode 6ab4 (1/2 a 12at7) the cathode then goes to ground. I have seen a schematic of a 57 using a ef86 in triode IIRC
[/quote]
What negative feedback to the cathode on CMV563 ???.
It is positive feedback. And it is noise optimal.
It causes in cathode resistor with lowest noise ratio.
Gus, see Van der Ziel once more ...

xvlk

 

[andre tchmil]

I own 2 CMV's with M7 capsules.
Here's what I did:
Bypassed the preamp board in the PSU.
Replaced the 3 big resistors close to the capsule (or are there 4 ?)
Replaced the small styroflex cap near the capsule.
Raised the cap voltage .
Cleaned the capsule.

I'm happy with them.
In fact they sound near identical now

 

[jrmintz]

I have an M71, the single pattern version of the M70. it's an M7 capsule with an MV 692 amplifier. Anybody have any tricks for spiffing that one up? For that matter, does anyone have a schematic for the Gefell MV692?

:thumb: :thumb:

 

[Gus]

xvlk

I don't know where to get that book in the USA.

CMV563 and UM57 and the ef86 UM92 schematics http://www.geocities.com/SiliconValley/Peaks/5212/start.htm

Does anyone have the inductance of the transformer ?

anyone know the PS V?

lets look at this circuit midband. Same current should flow in the plate and cathode R except for any energy storage in the cap inductor feed(?) path

Most of the time you would want a cap bypass on the cathode R for lower noise with the end of the transformer to ground.

I was thinking this circuit was made this way because of trying to do the best they could with cheap lams alloys on the other side of the Wall

I need to do some math and try to understand this circuit.

Someone I forget who, posted at the old place the circuit kind of looks like this one at the bottom of this PDF

http://www.lundahl.se/pdfs/datash/5402.pdf

 

[Guest]

[quote author="Gus"]
Most of the time you would want a cap bypass on the cathode R for lower noise with the end of the transformer to ground.
[/quote]
Not, if you bypass cathode R, you loss headroom.
And result wil not be "CMV"...
[quote author="Gus"]
I need to do some math and try to understand this circuit.
[/quote]
Yes, math around it is pretty.
It is one of several non boring microphone schematics (and acoustics
schematics at all). If someone say, that this mike is "sonically" boring,
he can modify load impedance (or termination).
I think, that it will not be so boring
xvlk

 

[Gus]

xvlk

This thread does bring up something I have been finding. Sometime the best circuit on paper does not sound as good as something else.

I keep finding that a simple triode or fet circuit sounds the most musical.

I have built the standard cathode biased circuits. take something like a EF86 with a 150K plate R and 2.2K cathode R. B+ at about 190VDC.

The one with a good cap bypass on the cathode resistor(>=100uf low ESR) always seems to sound more musical. This is adjusting for output level.

I always seem to like the C biased triode circuit in microphones without any cathode feedback about as close to no feedback as possable

Books say one thing ears say something else. I like to find the science in what the ears like.

Yet the gefell circuit is interesting.

 

[Guest]

By the way,
are somewhere on the net schemas of newer Geffells ??????
xvlk

 

[badger]

Gus.
Winding detail for both mics.
My German is not so good, but here goes.
Twin bobbin trafo.detail for one bobbin
primery.280 turns...0.13 wire.....10.6.mtrs......14 ohms
sec .2500turns..0.05 wire.....110 mtrs.......1000 ohms
windings connected in series......ratio8.95: 1
Hope this makes sense
andy.

 

[Gus]

Andy

Thanks!

Maybe a LL3616 wired 10:1 would be good to try?

 

[soundguy]

I was just gonna ask about suitable replacements, however there is not a lot of room in there, the transformer is suprisingly small. I think Id be more inclined to go with a jensen anyway for the extra color in comparison to a lundahl.

dave

 

[Marik]

[quote author="badger"]Gus.
Winding detail for both mics.
My German is not so good, but here goes.
Twin bobbin trafo.detail for one bobbin
primery.280 turns...0.13 wire.....10.6.mtrs......14 ohms
sec .2500turns..0.05 wire.....110 mtrs.......1000 ohms
windings connected in series......ratio8.95: 1
Hope this makes sense
andy.[/quote]

Andy,

Are they interleaved? Is it 2 sec and 1 pri in the middle?

 

[jensenmann]

Hi everybody
Dont be so shy and contact Micr*tech-Gefell to get the schems, they are very nice. I got my schems from them. If they don´t help you p.m. me, I can give you the CMV563 and N61/N61V schems.
The preamp in the N61V is indeed lousy. Bad quality east german parts, and so are the caps in the mike. Today I had a CMV on the bench with a f***ed up 1uF Elko. If you are plannig to mod your mike I´d suggest to change this cap first and listen if the replacemant had improved the sound. The cap is responsible for the lowend cutoff and makes it sound thin when getting old (and they are old). Maybe thats all it needs.
I´ve been told to leave my fingers away from the capsules since they are very, very sensitive. Gefell still services them.
cheers :guinness:
Jens

 

[hitchhiker]

hi Jens,

My mics are the older ones with neumann labels and N61 preamps.

Are these any better than the N61V version?

Lance

 

[jensenmann]

Hi Lance
The difference is - as far as I know - onle that there´s a micpre in the N61V Version ( V stands for "Vorverstärker" = Preamp), the mike itself remained the same through time. The N61 is only a PSU, audio is directly linked from the mike to the output plug, no preamp inside. But there was an option to upgrade the PSU with the preamp later. To find this out you have to undress your beauty and take a deeeeeep look inside :shock: . If you find any Transistors you do have the preamp version.
:green:
cheers
Jens