M49 with Tab Funkenwerk body

[scott_humphrey]

I bought a bunch of the 6947 tubes here:

http://www.dailyelectronics.net

 

[justgold]

Scott, your build looks lovely!

I purchased Oliver's M49 alternative kit and have been digging into it - the metalwork is really beautiful and solid, and I'd recommend it to anyone considering it for a project!

The kit comes with parts for the build (resistors, capacitors), and I have a question about these. I'm using Oliver's TLM149 to M49 schematic (http://www.tab-funkenwerk.com/id89.html) and layout (http://www.tab-funkenwerk.com/id88.html) that he recommended. But the part values he sent don't always match up with the schematic (not to mention a few extra resistors and a cap)...  I'm uncertain how to proceed, whether 1. The differences have to do with the use of the 5840 tube rather than the AC701, or 2. Having the parts for different versions (M49B or M49C), or 3. Some parts were misplaced, and I should just procure parts with the exact values from the schematic.

This confusion may all be due to this being my first project of this nature, as while I've been trying to research everything, laying things out well, etc - I'm still pretty green.

Any insight would be welcome, and I can't wait to share the results when I'm done.
Thanks!

 

[ValveTone]

Hi Justgold,

The parts included with the kit are indeed a bit off the schematic.  I would just order for yourself the parts you are missing to match up with the schematic; that's what I have done, where I didn't have them on hand.

Damon

 

[Edward]

Hi Scott,

I want to start by sayng that your M49 build looks fantastic. Great work.

I have a question, maybe you could help me with it..

If I understood correctly you used a BV11r transformer from AMI for your microphone. I have the same one but I am having troubles figuring out which lead is which on the transformer. On the AMI web page there is no spec sheet for the BV11r, and I tried emailing AMI several times without any response. Could you share something about on how you wired yours?


Best regards,

Edward

 

[Edward]

Nevermind... recieved an email from Oliver @ AMI now. All good.

Best,

Edward

Hi Scott,

I want to start by sayng that your M49 build looks fantastic. Great work.

I have a question, maybe you could help me with it..

If I understood correctly you used a BV11r transformer from AMI for your microphone. I have the same one but I am having troubles figuring out which lead is which on the transformer. On the AMI web page there is no spec sheet for the BV11r, and I tried emailing AMI several times without any response. Could you share something about on how you wired yours?


Best regards,

Edward

 

[tubestation]

Hello Scott,
Amasing Build!
Thank You very much for sharing your Experiments with the different Tubes. I looked at the 6947  Technical Papers and  it looks very good but i saw that the Tube pulls 350ma Heatercurrent. That s pretty hungry .It s probably because it s a dual Triode  with a shared  Fillament for both Systems. Do You tie the other unused System to Ground ? Is this Tube getting very hot in the Mic ? Do you think that it s possible to use this Tube in a small Mic or is it getting too hot ?
Thank You very much.
Lothar

 

[scott_humphrey]

Hello Scott,
Amasing Build!
Thank You very much for sharing your Experiments with the different Tubes. I looked at the 6947  Technical Papers and  it looks very good but i saw that the Tube pulls 350ma Heatercurrent. That s pretty hungry .It s probably because it s a dual Triode  with a shared  Fillament for both Systems. Do You tie the other unused System to Ground ? Is this Tube getting very hot in the Mic ? Do you think that it s possible to use this Tube in a small Mic or is it getting too hot ?
Thank You very much.
Lothar

Hi Lothar,

With the 6947 I tied the unused tube elements to ground, just like they do with the unused half of the tube in an AKG C12. I haven't tried it any other way.

Heat does not seem to be an issue, but I've not tried this tube in a small mic. I've used it in M49 and the U47-style mics, and the bodies of those mics don't seem to warm up much at all. Of course, you'll need a power transformer that can provide that current….

Best,
Scott

 

[tubestation]

Hello Scott,
Thank s for your Answer !
I try to get me a few of this Tubes to build me a Km 54 style Mic. I have a almost new Nickel KK 54 Capsule waiting to get activated.
If the Mic gets too hot i could  dig some small holes in the Body to vent the Tube.
I need to find a good small Outputtranny that fits into the Body first, or i put the Iron outside the Body.  I have some Lm 317 based Powersupplys with enough Power for the 6947 that could work with a Km 54c selfbiased Circuit.
Greetings and thank s again.
Lothar

 

[Banzai]

Bit late, but for these and other solder terminals the company you're looking for is Osterrath.

See pdf 

I like those solder tabs. They seem like a great combination of what I like about eyelets and what I like about turrets.

Anyone know where to buy them?

 

[madbeavis]

I built an M49-style mic recently with metalwork from Oliver at Tab Funkenwerk:

Capsule is a BeesNeez K7. I used a 6947 tube. O.K., now that I've purchase enough of these tubes to last me the rest of my days, I'll let the cat out of the bag:

http://frank.pocnet.net/sheets/084/6/6947.pdf

Enjoy,
Scott

Hi Scott,

I am in the process of doing the same tube with a Neumann K49 capsule. Did you use Oliver’s kit components or did you sub in some boutique caps/resistors in your build?

I was planning on using some TFT caps for the capsule and a silver mica for the capsule bypass. I am debating using some low ppm spiral wound resistors for the 100m around the grid.

Let me know you recommend any design changes to fit this tube better.

Thanks,

Chris

 

[madbeavis]

I completed this M49c build using the 6947 married to a Tab BV11r transformer and it is amazing. Here are some notes:

- Make sure your voltage divider network is accurate. Mine required some fine tuning to get the 60v capsule bias voltage when running at 140v on the B+.

- The Sennheiser/Nuemann K49 capsule sounds lovely in this mic and is totally worth the $800

- I was able to fit 2 teflon caps for the Capsule diaphragm bypasses on the middle deck by positioning the capacitors with the legs out. Be careful to leave room (around 2mm) for the basket lip when assembled.

- When I first powered it on it sounded terrible but after 2-3 days of burn in it became sweet and magical (probs due to the TFT caps). I swear it sounds better every time I turn it on.

- This microphone is 2-3DB quieter on transient response than my U47 with the same capsule. Im guessing this is a result of the 8.5:1 xmfr (BV08 is 6.5:1) and the pattern switching circuit but this could also have something to do with the cathode biasing. Over all its still a very loud microphone when compared to other LDCs

- Frequency response is excellent and appears to be better than charts ive seen for a stock M49c online.

- Self noise is astonishingly low. I guess I got lucky with this 6947 as I didnt even need to use my backup tube.

 

[earlfsmith]

I completed this M49c build using the 6947 married to a Tab BV11r transformer and it is amazing. Here are some notes:

- Make sure your voltage divider network is accurate. Mine required some fine tuning to get the 60v capsule bias voltage when running at 140v on the B+.

- The Sennheiser/Nuemann K49 capsule sounds lovely in this mic and is totally worth the $800

- I was able to fit 2 teflon caps for the Capsule diaphragm bypasses on the middle deck by positioning the capacitors with the legs out. Be careful to leave room (around 2mm) for the basket lip when assembled.

- When I first powered it on it sounded terrible but after 2-3 days of burn in it became sweet and magical (probs due to the TFT caps). I swear it sounds better every time I turn it on.

- This microphone is 2-3DB quieter on transient response than my U47 with the same capsule. Im guessing this is a result of the 8.5:1 xmfr (BV08 is 6.5:1) and the pattern switching circuit but this could also have something to do with the cathode biasing. Over all its still a very loud microphone when compared to other LDCs

- Frequency response is excellent and appears to be better than charts ive seen for a stock M49c online.

- Self noise is astonishingly low. I guess I got lucky with this 6947 as I didnt even need to use my backup tube.

Where are you getting these SennheiserNeumann k49? Not seeing anything on google

 

[emrr]

Where are you getting these SennheiserNeumann k49? Not seeing anything on google

They stopped selling parts recently. 

 

[madbeavis]

Oh man!!! That totally sucks about Sennheiser. I bought 2 K49’s from vintage king just last year. I’m not surprised I guess considering the k49 was still built in Berlin using similar techniques to the OG capsules and probably not worth keeping assembly lines going for them.

I always wanted to try a M49c with a CK12 like Tim Campbell offers. Not really the same thing but what is these days...

 

[madbeavis]

This from Klaus’ forum:
https://repforums.prosoundweb.com/index.php?topic=37497.0

 

[madbeavis]

Update on this thread. My Original 6947 tube got noisy so I swapped it for a JAN Phillips 5840 and did the 4.5v heater thing. It sounded pretty good but not exceptional. Eventually that tube also went noise and i missed the higher output from the 6947 so I went to purchase another one but could not find any.

I eventually found some 6948 tubes for sale and bought those. After installing the new tube mic is quiet again and aggressively loud. This past 5 months of using the 5840 I barley touched this mic. Now it might be my best sounding.

food for thought...

 

[jeremynothman]

What do you like about the new tube? That is a much higher gain factor, no?

 

[mjmajilton]

Update on this thread. My Original 6947 tube got noisy so I swapped it for a JAN Phillips 5840 and did the 4.5v heater thing. It sounded pretty good but not exceptional. Eventually that tube also went noise and i missed the higher output from the 6947 so I went to purchase another one but could not find any.

I eventually found some 6948 tubes for sale and bought those. After installing the new tube mic is quiet again and aggressively loud. This past 5 months of using the 5840 I barley touched this mic. Now it might be my best sounding.

food for thought...

The 6947 is a medium mu dual triode. The 6948 is a high mu dual triode. The 5840 is a pentode. Why are you replacing a dual triode with a pentode? Why 4.5v on a 6.3v heater. I've read that too low a voltage will poison the cathode.

 

[terry setter]

The 6947 is a medium mu dual triode. The 6948 is a high mu dual triode. The 5840 is a pentode. Why are you replacing a dual triode with a pentode? Why 4.5v on a 6.3v heater. I've read that too low a voltage will poison the cathode.

I've run 5840's very successfully at 5.7V and like the sound quite a bit, but 4.5V is low enough to reduce output and IMHO have a somewhat negative impact on the sound quality.

 

[Migs 31]

Phillips 5840 and did the 4.5v heater thing. It sounded pretty good but ...

Hi there,

Myself and fellow GDIY member @thomasdf are putting together parts for M49 inspired mics.

Can you kindly explain what the “Phillips 5840 and did the 4.5v heater thing.” actually did for you and what the basis for such under heating is.

That’s a genuine/curious question, I’m not being snarky or sarcastistic.
I am seriously willing to experiment with various parts, versions and variations of the M49-b-c-etc etc

Thank you kindly
M