My BRAUNER VM1 modification

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MS Vienna

Well-known member
Joined
Feb 1, 2016
Messages
110
Location
Vienna, AUSTRIA
The times when the VM1 was hyped are long gone.
Almost 10years ago I witnessed a shootout as a friend planned to buy one. It did sound fine and he got one.
A bit later I got a deal on a VM1 that has been sitting in a showcase but unused and with full warranty. And for the price I jumped on it. It even sounded a bit more balanced than the friend´s specimen.
However it never became a favourite of mine. I felt something was wrong with the sound. It just didn´t sound "right", "true".
So after the warranty extinguished I opened it and looked what could be done.

I started with the coupling cap. It´s a big Wima MKS 1µF 250V.

DPP_0215.jpg



I tried out various capacitors. When I got to the russian PIOs it got better (for my taste).
In the end of capacitor testing I settled on a well proven, high quality model for it offered least sound degradation and best transient transmission. Sonically almost "invisible".
I noticed that this forum is pretty heavily focused on the U47, so many of you might recognize this classic cap:

Bosch%20MP_zpsijjhgfek.jpg


In order to mount it I made a brass brigde that I screwed onto the VM1´s frame. Luckily there´s plenty of space inside so it´s a perfect fit.
The nice thing about the Bosch is that you can get three different capacitance values depending on how it´s terminated.
 
Hi,
you could also try to swap the source capacitor of the N Jfet with an Elna Silmic II ...
the improvement is probable ...

regards
 
MS Vienna said:
In the end of capacitor testing I settled on a well proven, high quality model for it offered least sound degradation and best transient transmission. Sonically almost "invisible".
I notice you have substituted a 0.5uF for  a 1uF. I would think the difference in LF response is dominant over the difference in "capacitor sound". Cleaning VLF response can "open" the sound.
Hav eyou tried connecting both halves in parallels, so the value would be unchanged; scientific approach 101: change only one parameter at a time.
 
Who cares about science? We're looking for "mojo" here ;D

abbey road d enfer said:
Hav eyou tried connecting both halves in parallels, so the value would be unchanged; scientific approach 101: change only one parameter at a time.
 
I like the brass bridge and old fashioned output capacitor wires.
MS is ready to start a new VM1 special edition. :)
 
abbey road d enfer said:
MS Vienna said:
In the end of capacitor testing I settled on a well proven, high quality model for it offered least sound degradation and best transient transmission. Sonically almost "invisible".
I notice you have substituted a 0.5uF for  a 1uF. I would think the difference in LF response is dominant over the difference in "capacitor sound". Cleaning VLF response can "open" the sound.
Hav eyou tried connecting both halves in parallels, so the value would be unchanged; scientific approach 101: change only one parameter at a time.

Usual in tube mikes where i tried different values, mostly measuring electronic circuit response on the scope, difference between 1uF and 0.5uF was above 20Hz. Of course there are phase differences. Anyway jumping between 1uF from various type, or 470nF - 500nF  (comparing similar values - measured also) best results i always had with MP caps. Russian are good but the best results i had with these old german made - bosh, siemens, hydra, itt etc.
Other thing is that the best results i always had with lowest capacitor value - of course not changing low end drop in usable range.

Highly reccomend to try E80F tube (Valvo/Philips/Mullard)!
This could be the best mod for that mike ;)

Another usefull thing could be setting new cathode capacitor value - sometimes even could go lower with better results ;)
 
I am basically an acoustics/mechanics-guy focusing on capsule performance and the acoustics inside the grillecap (term for "headbasket" I´m used to).

Compared to you guys I´m pretty blank when it comes to electronics so good suggestions and help are always welcome.
Swapping coupling caps was obvious and easy enough so I just tried it.
However, no miracles should be expected from just doing this (btw I tried all possible value settings on the Bosch). It just removed a bit of mist from the signal and allowed me to get a slightly clearer impression of the mic´s acoustics which I adressed in my further steps.
Edit: With the Bosch the word "mojo" doesn´t come to mind. "Fidelity" does.

micaddict said:
Have you guys, by any chance, heard of the Klaus Heyne Edition?
Yes. Klaus often pointed out that the KHE is a totally different beast than a stock VM1, so nothing to have in mind when you´re planning to tweak your regular VM1.

granger.frederic said:
Hi,
you could also try to swap the source capacitor of the N Jfet with an Elna Silmic II ...
the improvement is probable ...

regards

Thank you! I´ll consider it. Could you point me to it? One of the other Wimas? I don´t have a schematic and I don´t bother since I don´t plan to change the circuit.
In the course of my experimentation I swapped the two small Wimas for other types of the same value.  More about that later.

ln76d said:
Highly reccomend to try E80F tube (Valvo/Philips/Mullard)!
This could be the best mod for that mike ;)

Interesting! Is it a drop in replacement or does it require changes to the circuit?
How does it affect the sound?

Gus said:
You like the capsule?

Not dearly...

abbey road d enfer said:
scientific approach 101: change only one parameter at a time.

Exactly! Otherwise you just fool yourself and don´t make real progress.
The coupling cap testing took me quite a bit of time and probably can´t be done on one afternoon if you´re serious about it. The differences can be barely audible and many times I listened to a change on several different days to form myself an actual opinion.

I´m going to find the making-of pics of the acoustics-mod and post them soon.
 
If your microphone uses 5840 tube, you can't use E80F without significant  modification. But, maybe it is possible if there is already 9pin socket and 5840 is attached with an adapter. Some VM1 was equipped with EF86, as I know.

OT:
Does anybody know which tube is really used in VM1 KHE? It looks to me as ordinary EF86, not as low noise, selected TFK EF806 stated in the info on
http://recordinghacks.com/microphones/Brauner/VM1-KHE


 
AFAIK all early Brauners had a carefully selected EF86 (or EF806).
Then it was replaced by the 5840/EF732.

The capsule used to be made by Haun, but since a couple of years Dirk makes his own.

Regarding the KHE, I was just curious if you guys knew it (but obviously you do), especially since Klaus is a member here now. He might chime in.
Yes, his is seriously modded. But/so he knows a thing or two about the original and its arguably "weaker" points, of course.
 
my mistake,

i just looked at the picture , i didn't realize it was the VM1 thus a tube headamp...
however , you can swap the CATHODE capacitor for an ELNA Silmic II....

i never opened a VM1 , could you make a schematic ?
then we could discuss more about improvements and see what's the role of the transistor (probably not a Jfet...)

regards
 
MS Vienna said:
ln76d said:
Highly reccomend to try E80F tube (Valvo/Philips/Mullard)!
This could be the best mod for that mike ;)

Interesting! Is it a drop in replacement or does it require changes to the circuit?
How does it affect the sound?

It can affect the sound in many ways :D

It's a pin to pin compatible with EF86. "Special Quality" tube with better specs.
https://frank.pocnet.net/sheets/030/e/E80F.pdf
If you will put it in the circuit - first i would measure polarisation voltage, since E80F draw more current.
If topology is typical (and probably it's) front diphragm voltage can drop a little - so you will have to change one resistor if the voltage is going thru divider. Overall it affect sounds in few ways. If everything is ok, you should notice better high frequency response as also better controll of low end. It's very "clean" tube.
Maybe there's a chance, that you could drawschematic?
 
granger.frederic

There should be at least two schematics of the VM1 on the web.  I posted one years ago.

Other things to note

There are threads that have information on the output coupling cap size and type in tube microphones

Capsule is different there have been posts on this as well
 
Ok i found one - this one is without transistor.
No luck with 5840 version...

Gus do you have it?
 

Attachments

  • BraunerVM1schem.GIF
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Basically most microphones is like G7 and G7 is like most of microphones ;D
The Devil is in the details.
Hand  drawn schematic for EF86 is above but this exact version with 5840/EF732 have additional transistor, so it would be goud to see what for it is ;)
 
ln76d said:
Basically most microphones is like G7 and G7 is like most of microphones ;D
The Devil is in the details.
Hand  drawn schematic for EF86 is above but this exact version with 5840/EF732 have additional transistor, so it would be goud to see what for it is ;)
I haven't seen it, but a wild stab-in-the-dark guess would be that it is a constant current source as the anode load. Higher linearity, high dynamic range, but then it will clip really nastily if you overload it.
 
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