Tillmann

RFT 7151 Bottle microphone
« Reply #40 on: August 03, 2006, 07:49:04 AM »
Michael,

I was pretty sure you were going to say that it was Andreas Grosser.  A friend of mine just met with him a month ago about a U57 microphone and was very, very impressed.  Grosser also didn't have many nice things to say about many of the American guys modifying and selling parts for old German mics (actually, many of these guys are Germans who now live in America).  That statement can be a bit misleading, so let me clarify- I won't get any more specific other than to say Mr. Grosser very respectfully declined to say much of anything and definitely nothing positive about modifications being done in the States by many of the "experts".  He refused to talk a lot of sh*t, but it was apparent he did not approve and gave examples of things, but did not mention names.  He seems very much like a purist though, who trusts the original designers and the parts they used, which is the opposite attitude of the guys in the States.  That was my second-hand impression, so that could be off-base, I don't know.  I really don't know who to believe on issues with the old East German tube mics.  There is just so much conflicting information out there.

Have you heard your new mic?  How do you like it?  Can you compare it to some other mics that you've heard?  How do you like the sound of the original output transformer compared to the U67 transformer?

Friends of friends of mine rescued loads of old tube mics in the trash after the wall fell out at the old East German TV complex in K√∂penick, and at other places as well.  Wow, what a time it must have been to be an audio engineer in Berlin and even all over Germany in 1989 and 1990!


3phase

RFT 7151 Bottle microphone
« Reply #41 on: August 03, 2006, 08:13:35 AM »
He is indeed very purist and modifies only when he sees mistakes in the circuit...and he sees often mistakes...
Beside that he is not into changing the original sonic signature of a mike.
He however usually improoves the headroom, often drasticaly...even on "modern" Neumanns.

RFT 7151 Bottle microphone
« Reply #42 on: August 11, 2006, 09:47:13 AM »
I would have  a hard time paying Grosser back for all the help and time he has given me. He is an electronics engineer as well as a tech, and a good one at that!

mig27

RFT 7151 Bottle microphone
« Reply #43 on: August 11, 2006, 12:04:30 PM »
Seconded - Andreas Grosser really knows his sh*t.

Michael

mig27

RFT 7151 Bottle microphone
« Reply #44 on: August 11, 2006, 12:14:07 PM »
Oh, and I promise to post some audio samples of my 7151, in A/B with my U47 fet.

Later folks...


Michael

Tillmann

RFT 7151 Bottle microphone
« Reply #45 on: August 11, 2006, 12:28:51 PM »
You know, I don't deny for a second that he really knows the technical aspects of these mics, probably as well or better than anyone out there, but in the end, it seems like a lot of this comes down to taste.  A lot of the mods that people are doing in the States revolve around really trying to change the sound of the mics and make them better by, for example, swapping out output transformers and the like, and it's not an issue of the transformer being broken, it's an issue of the sound of the transformer or the circuit build itself.  Grosser, being a purist, seems to believe, as I've heard, that the original transformers sound fine.  Others don't.  Michael (Mig 27), even your tech here in Germany as you put it:

"...wasn't happy with the performance: Good s/n ratio, but questionable frequency response.... He simply could not accept a less than stellar performing RFT product leaving his home lab. So he installed a second output transformer, taken from nothing less than a Neumann U67."

This seems to be the type of thing Grosser, as a purist, frowns upon.  It seems like he would say, "If it's not broken, don't fix it".  Others say, "Yes, but it could sound better."  So this is why I say I don't really know who to trust, because the taste in sound of each tech restoring the mic is different.

If I had some different mics restored by different techs, all in a room, I would be able to know whose work I like better, but that doesn't seem possible.  Unless..... :idea: :idea:  :idea:  MICROPHONE SHOOT OUT IT BERLIN, ANYONE???  Come on fellas!  Let's do it!

 :green:

T

rodabod

RFT 7151 Bottle microphone
« Reply #46 on: August 11, 2006, 12:41:27 PM »
Quote from: "Tillmann"
:idea:  MICROPHONE SHOOT OUT IT BERLIN, ANYONE???


sh*t, I think I'm gonna have to comne over to Berlin again.  :razz:
Quote from: tv
punchy fat bastard chip

Tillmann

RFT 7151 Bottle microphone
« Reply #47 on: August 11, 2006, 01:59:51 PM »
Yeah Roddy, if this actually happens, you can crash on the sofa!  We'll need witnesses!  :razz:

T

Gus

RFT 7151 Bottle microphone
« Reply #48 on: August 11, 2006, 06:34:00 PM »
FWIW

  When I work on a microphone I first try to understand it.  What I mean, what does it sound like it does best.  If I can find a schematic I will study  it like I am doing archaeology.  Why did they do that? etc.  Hints are sometimes in the schematic.  Why that operating point? why that grid resistor? etc.

  It is kind of cool to do this.  A few microphones I worked on I tried to get them as close to stock from what I could reason from the circuits.  I sometimes change very few parts, often just changing bad electro cap(s) and cleaning  the capsule if it needs it fixing the grill and body and a good cleaning of the contacts.  Often an old microphone can sound very good when it is close to stock.

  Any change I make I save the old parts.

I recently worked on 6 u87s from the 70's (clear plastic)  after I cleaned the capsule and other parts and fixed the grill and bodies I was impressed at how good they sounded stock.  All I did was try to bring them back to as close as I could as when they were bought.

transformers
« Reply #49 on: August 11, 2006, 08:40:47 PM »
I think the output transformer is a big part of a mics sound. If you were to rebuild a 7151 and improve the signal to level by completely changing the circuit then fine. If you were to change the circuit and the transformer thats fine too. But at what point is it not a 7151 anymore? Leaving in the stock transformer is O.K. if you can  get a nice flat response form 50 or 80 to 35k or 40K and the mic retains its original character but has low noise. Then you have another mic sound to add to your 47s, 37s ,u87 mics. If you have few mics and need a u67 or something you can build the 7151 closer to that.. Also I think some of the 7151 transformers are better than others. Just by accident I think. In that case you have no choice but to change them out.


Tillmann

Re: transformers
« Reply #50 on: August 12, 2006, 09:29:19 AM »
Quote from: "lewilson"
I think the output transformer is a big part of a mics sound. If you were to rebuild a 7151 and improve the signal to level by completely changing the circuit then fine. If you were to change the circuit and the transformer thats fine too. But at what point is it not a 7151 anymore?



Point taken, but I think for a lot of people, it's all about the capsel and the tube that attracts them to those mics.


 

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