[Melodeath00]

poctop,

I noticed that Neumann biased the AC701 differently in the 269b, which has 2.4V on the grid, compared to 1.6V in the 269c (and the M49b and c, which use the same tube, too). They also have the plate resistor at 150k in the 269b and c, compared to 100k in the 49b and 49c. Any idea why for this stuff?

[dmp]

I fired it up with a sylvania 5840, 150k and 3k, and got 1.5v on vk, and 46v on vp. Seems right on.

[dreadheaded]

Hi Guys

Through reading this thread the m269b and the u67 thread I have managed to overcome all the issues with my m269c build up to this point, Installed a CV 468 tube and the capsule managed to get the Heater Voltage to the right area with a load, but the B+ voltage didnt change at all upon plugging in the mic

The mic powers up fine and I get 6.3 on H+ and 127.5v on B+

as opposed to around 20v H+ and 128v on B+ unloaded

I can measure around 30v on the front diapgram but I am guessing reading from here is pretty inaccurate due to the impeadance

The only noise coming out the mic is from the switches, But they arent popping, it seems like you can actually hear the switches being switched through the microphone but nothing else. Also get an occasional squealing that I am guessing is a bad tube

Could this all be from a bad tube?

I have triple checked all the transformer, PSU, XLR and Capsule connections and just cannot work out the problem


For reference the mic has a CV 468 Tube, Peluso KK67 capsule and Sowter 1304 transformer

Thanks!

[dreadheaded]

OK I worked it out, turns out I am a total idiot who cant read instructions!!

As a side note the mic's output is REALLY loud, like so loud it doesnt seem right, is the m269 a particularly high output mic?

using a CV468 Tube

[poctop]

if it sounds thin and way too gainy it might be that your transformer is backwards ,
Dan,

[dreadheaded]

Thanks I will check that. I am using the sowter 1304 and I was a little confused when working out how to connect it

[dreadheaded]

So after a while of playing around with my m269 I have got it sounding pretty great, but no matter what I do I cant seem to get rid of what sounds like a grounding issue

I notice that no matter what I do pin 7 on the XLR is connected to the Ground on the 3 pin XLR, is this correct??

I am wondering if that is whats cauusing my issues

[poctop]

You Should always have the SHLF Jumper in position ,  this will ensire that you cable shield is tied at both end of the cable ,
you Should Also have the 0V star grounded to your case and then from there to you IEC earth ground ,

Best,
Dan,

[Marcedona]

Hi Poptoc, nice sound! wich transformer you used in this specific build?  Regards

Here it is, the process is started  i got that neumann capsule on ebay and cleaned it a bit and i will try to put it in all the other mic and take a shot at it ,

Here with the D-M269c and the restored neumann capsule back to life again,

https://io.groupdiy.com/file/gdiy-2017/u/39511/58d0281993c52.wav

Best,
Dan,

[doqmemory]

Any idea when the PCBs will be back in stock Poctop?

[doqmemory]

If we could get 50 commits to order, perhaps we could persuade Dan to order some more boards?  I would be in for a pair.  Anyone else?

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