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Author Topic: Building a second M49 clone  (Read 3671 times)

NelisB

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Building a second M49 clone
« on: March 11, 2014, 05:21:06 am »

Hi all,

After converting a TLM49 to a M49 clone a couple of years ago, I am going to do another. For the first one I used Oliver Archut's diagram: http://www.tab-funkenwerk.com/id89.html

I have a Neumann K49 and a SPA 1 micron M7 capsule, a AC701K tube and an AMI Bv11a transformer.

But now I am considering to build the original M49C circuit.

What are the cons and pros of both the diagrams? And which one would you choose?

Thanks !!

Best Niels
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klaus

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Re: Building another M49 clone
« Reply #1 on: March 11, 2014, 12:00:38 pm »

At first glance, Oliver's schematic duplicates that of an M49 pretty exactly, aside of the (wisely) omitted high- and low-frequency attenuation, and the missing "cardioid-only" switch.

The biggest obstacle to get close-to-original M49 performance will be your use of the 1µ SP capsule.
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Klaus Heyne
German Masterworks®
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NelisB

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Re: Building another M49 clone
« Reply #2 on: March 11, 2014, 02:55:06 pm »

Hi Klaus,

Thanks for your reply.
The SP capsule is not a must, but I want to give it a try. It comes from a UM57 that I had moddded by SPA.
The noise floor of the UM57 is very (too) high. And my first TLM49 conversion is very very quit. So I want to try the capsule in a M49 circuit.
If it doesn't work out, I'll replace the capsule with a Neumann K49.

Cheers
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J.J. Blair

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Re: Building another M49 clone
« Reply #3 on: March 19, 2014, 12:47:03 pm »

1µ???? I guess you can never have too thin a membrane.

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panman

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Re: Building another M49 clone
« Reply #4 on: March 20, 2014, 11:02:17 am »

1µ???? I guess you can never have too thin a membrane.

J.J., please verify, that you really have first-hand information of using that product! Otherwise your posting has to be deleted.
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Esa Tervala

J.J. Blair

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Re: Building another M49 clone
« Reply #5 on: March 20, 2014, 01:08:17 pm »

How do you think I protect my microphones?
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panman

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Re: Building another M49 clone
« Reply #6 on: March 20, 2014, 07:28:13 pm »

Oh, I see. Hmm.....
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Esa Tervala

NelisB

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Re: Building another M49 clone
« Reply #7 on: March 29, 2014, 07:22:28 pm »

LOL!!!

Oliver has 3 1G resistors in his schematic.
Not many manufacturers make 1G resistors.
Can you advise one, especially for R2, which is between capsule+grid to earth?
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NelisB

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Re: Building a second M49 clone
« Reply #8 on: April 10, 2014, 09:50:01 am »

I found these:
http://www.vishay.com/docs/31039/bh.pdf

Carbon film, there is a 500M/0.5W on the datasheet. Not 1G, but must be enough, right?

Any thoughts about this resistor?
Biggest problem untill now: Nowhere available..

Thanks, Niels
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Jim Williams

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Re: Building a second M49 clone
« Reply #9 on: April 10, 2014, 11:13:17 am »

1 gig film resistors are available from
www.digikey.com
Look up the 'mini-mox' series, the 1/4 watt runs about 5 bucks.
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NelisB

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Re: Building a second M49 clone
« Reply #10 on: April 10, 2014, 12:55:20 pm »

1 gig film resistors are available from
www.digikey.com
Look up the 'mini-mox' series, the 1/4 watt runs about 5 bucks.

Thanks Jim,

Are they good quality for a tube mic? Compared to carbon film? Noise and sound? What I heard is that Metal Oxide resistors are not the best for audio.

Thanks!
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Terry

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Re: Building a second M49 clone
« Reply #11 on: May 19, 2014, 05:28:09 pm »

Hello,

You won't find a carbon film 1G resistor that will fit in a microphone!  It takes metal oxides to get the HIGH values.  Also, you won't have significant current passing through it.
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NelisB

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Re: Building a second M49 clone
« Reply #12 on: May 31, 2014, 04:33:56 am »

Hello,

You won't find a carbon film 1G resistor that will fit in a microphone!  It takes metal oxides to get the HIGH values.  Also, you won't have significant current passing through it.

I know. I found a 500M carbonfilm from Vishay Dale. I am going to try those.

Thanks
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Jim Williams

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Re: Building a second M49 clone
« Reply #13 on: May 31, 2014, 11:59:17 am »

The 1 gig metal oxide resistor is not the major noise contributor to the system, it's the active element, in this case a vacuum tube.

In fet designed mics with super low noise jfets the resistor is still not heard as a noise source. If you use carbon resistors, that may change.
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