UM57/ CMV 563 sound so boring, whats up?

[soundguy]

The first time I heard a UM57 I thought it was broken, then I heard a few more and they are just boring sounding. I have two cmv 563's which have to be similar circuits (to the um57) , they are boring sounding in the same kind of way. Out of all the tube mics I have ever listened to, these two are the most characterless mics out there I think, and yet people fiend over them, cant imagine why. Everytime I hear someone compare a cmv with an M7 to a U47 I scratch my head, maybe I just have the absolute worst examples of these mics which could be my bad luck.

the sound of those mics to me, is that the circuit is just taking advantage of maybe only %80 of what the capsule is giving it, they dont sound efficient to me at all. Even a noisy c60 sounds more interesting to me.

any of the mic heads here ever look at those mics? Is there an easy obvious "mistake" in design that would explain my observations? Im bored to hell with my cmv's and am thinking about modding them into something more usable to my ear, but would like to understand a little more about whats (not) happening with those mics.

dave

 

[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

Something to try connect the transformer wire to ground instead of the cathode Bypass the 1.5K with a good electro 100uf or greater.

Possable problem the gain is greater than a 12ay7/ 6072a I don't know if the transformer will "like" being driven harder or it might sound real good.

IIRC I read on the web that sometimes the lam alloy in the transformer in east germany was not always good.

 

[andre tchmil]

Don't underheat the tube.

Replace the 220 M resistors with new ones.


Change the output 1µF to a bipolar type

 

[soundguy]

I think I'll try that this winter. Whats the logic behind changing the resistors? Drift, or do those have a rep for not sounding good?

dave

 

[andre tchmil]

Dave , I got this info amongst other from an older german guy who used to service these babies.

from what I remember , some components were very low quality.
And you have to have some luck with the capsule also.
Something to do with Mylar or PVC ( ?) in certain bathes.

And oh yes ! , rip out and bypass the preamp in the PSU.

 

[soundguy]

I didnt even realize there was a preamp in the power supply...

is there a schem for the cmv563 online anywhere?

dave

 

[asm]

dont brutalize that beautiful thang.
sell it to me.

seriously.


:razz: :guinness:

 

[soundguy]

Id consider selling one, got two... I could part with a body, M7, M8 and a power supply.

dave

 

[hitchhiker]

hi Dave, I have two of these and they are so different. My fave is
a wee bit mellow but has a bottom end that maybe I'll hear beat out if If I get to hear a u47 :razz:

the other has a boost about 8 - 9 kh that I'm gonna try on drums next.

Pretty good on bass but I like a gefel 711 for bass amp. With my minimal
experience I'd say my u87ai is so matter of fact, plain and artless where the cmv563 is a gentle but solid , interesting sound.

Are your capsules very close in sound?

Lance

 

[soundguy]

my capsules have slight differences, but the difference is dirt Im sure, if I got them cleaned, Im pretty sure these mics would sound the same. Whatever differences there are, they are nominal, after hearing bunches of these now, I can make a good overall picture of what the sound is and I think its really characterless and boring. Not really what Im looking for when reaching for a tube mic. Thats not to say that I havent made great recordings with these and one has saved my butt on a singer that didnt work on anything else, but with so much money invested in these things, it would be nice to use them more often. The sound they make, along with the UM57 really sounds inefficient to me, its the type of sound that really has the feeling that it could be made to sound better. I guess I posted out of curiosity to see if anyone else had similar feelings, first I thought this was isolated to the few Ive used, but now Ive heard a bunch and now Im starting to get similar feedback from guys that use these in other places so Im starting to think its just a lousy design that could be improved and not just an isolated case of yet another 40 year old mic starting to fade out...

dave

 

[squib]

these mics are great. My tip ... clean the capsule. Adjust the PSU HT to get 80V onto the capsule rather than the usual 60V..they like it!!

 

[hitchhiker]

Dave,

maybe we could choose the mods that seem most likely to be a good start
and then compare notes? I'm game.

I have schematics for the power supply but not the mic.

Lance

 

[Gus]

IMO capsule voltage need to be adjusted on a capsule by capsule basis. Sometimes lower is better depend on spacing and other things.

The m7 are PVC with pasticisers added to the PVC the pasticisers help the PVC strands to flex by filling in between the bends. It outgasses over time

Remember the older cars that the plastic would flake off the inside parts.

Cleaning a M7 is a pain I have only cleaned one in a gefell I have it is not as easy as PET.

You need to think like an Art restorer working on a painting

I think even PET changes something happens with it that the gold flakes off with time and it seems to start at the edge of the gold in a 87 type capsule.

Maybe a new gefell capsule will help the microphone. I believe the newer M7 with the PET skin is called the M9

 

[soundguy]

Ive got omni's and 8's also, I think the main problem is with the amplifier in the mic. The transformers in these things are really tiny and not particularly impressive looking at all.

Im kinda torn between what to do here, I went through this with a c12a, sent it to korby and he turned it into a mic that someone last week offered to trade a u67 for. Im sure these could be turned into something impressive, they are just worth so much Ive got cold feet to mess with them.

It pretty much sucks when a bland sounding not so good mic is worth potentially more than the same mic fixed up and changed. I should probably stop thinking along these lines and either sell it or make a good mic...

dave

 

[Gus]

or buy a new gefell

 

[hitchhiker]

Bill Bradley told me that when he gets cmv563 mics sent over from Europe
that he doesn't bother to ship the power supplies. He said they're not
good enough to bother with. He uses a new solid state supply .
I also think he almost always does up a new capsule.

 

[soundguy]

It wouldnt come as a shock if the power supply is half the problem. Im not an antique collector so Im sure this is bound to offend someone, but I cant see the point in staying with a tube power supply for something as delicate as a microphone. I have some C60's whose performance was improved, I dont know, approximately one million times better by using a new supply with a jensen audio transformer. They are not stock, so worth less, but a stock one sounds worthless in comparison. It would seem that adding a new modern regulated supply would be something to consider, Ive only ever seen improvement by going this route. I think Im really starting to lean towards turning one of these into a REALLY good mic. Stock I think its anything but.

dave

 

[hitchhiker]

I'll scan and give a link to the power supply shem over the weekend.

 

[tommytones]

Work on the psu Dave. We have like 15 of these (um57) mics and they do need work to make them come alive. The biggest difference is a new psu. Completely changes the whole picture and improves the noise significantly. I certainly wouldn't say they lack character. Mind you, how old are your mics? I'm biased with my opinion because our stuff is old (all Neumann badges) and I haven't listened to any of the newer ones. I had some of these mics right up there with m269's.

 

[soundguy]

mine are old neumanns. Perhaps they arent totally colorless but they dont AT ALL inspire any kind of microphone lust when you use them, no excitement at all. Im gonna research maybe buying a new supply to start, just to see. Im leaving for a few weeks out of town shortly, so Im months away from working on this right now, but wanted to get some feedback and start toying with the options before just jumping right in to modding a nice old neumann mic into some *I* thought would be better.

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. I have this old vintage mic or whatever. Its worth a shit load of money. Everyone says its good. I can sell it right now for tons of money. But it sounds like shit and it isnt *broken*, its just old and out of spec. I dont want to mod it because then Ive changed the circuit which is supposed to be so awesome. I dont want to use it because its pretty lackluster. I dont want to sell it because I finally have one.

As the gear we love gets older and older, this becomes more and more of an issue. Noisy old completely out of spec not so good but usable sounding guitar amp is one thing, but quite a different animal when you are talking about a microphone or a preamp or something like that.

dave