Phrazemaster

OK, it's clear my bad voltages were due to the IPA not totally dry - weird. But they are spot-on now!

Installed a BeesKneez K7.

She's gorgeous!

She sings!

She's got that magic sheen, presence, etc...

Shame we can't post mp3's here. I don't have a soundcloud account. Otherwise I'd post a sample.

Thanks to Dany and all y'all!
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Phrazemaster

Just before finishing initial testing she started humming, louder and louder...Not sure if that's the tube going, or what.

Turned her off and going to bed for now.

Night all.
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Just before finishing initial testing she started humming, louder and louder...Not sure if that's the tube going, or what.

Turned her off and going to bed for now.

Night all.

you may have to experiment with the shield wire cause you may end up with a gnd loop to mic chassis ,
try just keeping the circuit(audio) gnd and lift the shield out of the mic pcb  and try that out before you remove the tube ,
Best,
Dan,

Phrazemaster

Here's a link to a file with the buzzing in it, plus a little of me goofing off singing and talking. But you can hear the buzz at a low level in the background. In the studio, with headphones, it's LOUD, although not so loud in this sample. No processing on this, except normalizing.

https://www.dropbox.com/s/1fyow5e3kod9mff/M49%20Buzzing-Track%202.wav?dl=0

I did try lifting the jumper in the psu but that didn't help. But again, this noise did not appear until a few hours after using the mic. Prior to that, it was very quiet. Does this sound like tube noise? Or shielding/grounding? Or do I need to reconnect a connection?

Dany suggested maybe resolder a grid connection; I may try redoing the capsule connections tonight and report back. But suggestions are welcome.

So close...such a lovely sounding mic!!!

Here's a pic of the grounding scheme I used in the mic itself. Is this OK?

Thanks.
« Last Edit: May 20, 2015, 09:36:03 PM by Phrazemaster »
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Winetree

I'd like to use the AMI BV 11r in this build. Being a P.S.B. transformer how would mounting  be possible?
How could it be wired?

I'd like to use the AMI BV 11r in this build. Being a P.S.B. transformer how would mounting  be possible?
How could it be wired?

you mean the AMI BVr11r is wire transformer ? or circuit mouting with pins
Let me know,
Dan,
if it is wired , just hook it up to the second deck with the wires,  follow schematic for pinout of this transformer and color code
Best,
Dan,


Phrazemaster

Question gang, could a bad tube cause low plate voltage?

I've been wracking my brains on my build; at first the plate voltage was only 28v. This after lots of cleaning with IPA and flux remover. Then after it dried really well the plate voltage rose to 43V or so.

I was getting a noise issue, so I ended up replacing a couple of components to try to solve it, and also used more IPA. After that, the plate voltage was again low to 28v or so, but rose steadily as it totally dried again to 43v.

Still having the noise issue, I replaced another component and again cleaned the board. The voltage dropped to 27v or so, but I though no big deal; there's just some residual IPA somewhere, maybe in R7 or something.

Thing is, it's never recovered. Now plate voltage is about 27v and I've now replaced many other components to try to figure this things out. I've also reflowed all solder joints.

Turning R7 doesn't make any difference; I replaced it and still no joy.

Could I have a bad tube? It was expensive; I hate to take it out, but I could. I'm about ready to rebuild the main PCB with all new parts, and hopefully there was a cold joint or some bad component in some fashion. Just hope not the tube.

Anyway, could a bad tube cause a low plate voltage? And why would it react that way, going in/out of spec, with basic cleaning of IPA?

Thanks; I'm getting frustrated as I can't seem to find the fault.

Best,

Mike
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SO CLOSE to being finished with my build! Two quick questions:
1.  Does anyone have specific spec on the standoffs? I need to order a few to round things out but want to get it right the first time!
2.  I have a Neumann K49 capsule that will eventually go in this build, but I'm uncertain of what the proper capsule holder would be as well as dialing in the correct height - any suggestions?
Thanks!

vinylwall

I picked the majority of these parts up from "justgold".  Oliver Archut AMI M49 Alternative Kit.  New AMI M49 metalwork (body), AMI made PSU, Neumann K47fet capsule, Sylvania NOS 5840 Tube, AMI T49 transformer, Dany's D-49 PCB's.  "justgold" had most of the PCB's already built.  I finished off the complete build (M49c version), and she sounds great.  I still need to raise the capsule higher a bit:
« Last Edit: July 08, 2015, 09:58:53 PM by vinylwall »
Jimi Ray

vinylwall

Assembled M49c:
« Last Edit: July 08, 2015, 10:01:24 PM by vinylwall »
Jimi Ray


vinylwall

Oliver's PSU for this build:
Jimi Ray

Phrazemaster

Still can't figure out grounding. Is my diagram right?

I'm redoing this mic from the ground up and I would love to know how to ground in the mic properly. I got buzzing before.

Comments from those who have built this successfully? Pic attached.

Thanks,

Mike

Here's a link to a file with the buzzing in it, plus a little of me goofing off singing and talking. But you can hear the buzz at a low level in the background. In the studio, with headphones, it's LOUD, although not so loud in this sample. No processing on this, except normalizing.

https://www.dropbox.com/s/1fyow5e3kod9mff/M49%20Buzzing-Track%202.wav?dl=0

I did try lifting the jumper in the psu but that didn't help. But again, this noise did not appear until a few hours after using the mic. Prior to that, it was very quiet. Does this sound like tube noise? Or shielding/grounding? Or do I need to reconnect a connection?

Dany suggested maybe resolder a grid connection; I may try redoing the capsule connections tonight and report back. But suggestions are welcome.

So close...such a lovely sounding mic!!!

Here's a pic of the grounding scheme I used in the mic itself. Is this OK?

Thanks.
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Phrazemaster

Or would the following scheme be better? Or something different?

Anyone?

Thx.
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Or would the following scheme be better? Or something different?

Anyone?

Thx.

use only from psu pin 7 to mic pcb pad 3
and do not use psu pin 3 to mic pcb pad 7

let me know how this works
Best,
Dan,



Phrazemaster

Many Thanks Dany.

So I've attached one more photo with two versions; which would be better?

It seems version 2 would avoid a ground loop, but then the schematic shows a connection to the shield from the mic...Or is there yet another way of doing this?

I thought I saw pix with people having a connection from the mic PCB to the chassis...did my eyes wrong me?

Thanks a million,

Mike
« Last Edit: July 05, 2015, 09:17:59 PM by Phrazemaster »
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Phrazemaster

Many Thanks Dany.

So I've attached one more photo with two versions; which would be better?

It seems version 2 would avoid a ground loop, but then the schematic shows a connection to the shield from the mic...Or is there yet another way of doing this?

I thought I saw pix with people having a connection from the mic PCB to the chassis...did my eyes wrong me?

Thanks a million,

Mike

Bump? Anyone tried either of these schemes? Which is better?
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Many Thanks Dany.

So I've attached one more photo with two versions; which would be better?

It seems version 2 would avoid a ground loop, but then the schematic shows a connection to the shield from the mic...Or is there yet another way of doing this?

I thought I saw pix with people having a connection from the mic PCB to the chassis...did my eyes wrong me?

Thanks a million,

Mike

Bump? Anyone tried either of these schemes? Which is better?

it might depends on the RF environnement of the mic ,
somtimes it is better to lift the shield of the cable to prevent issues ,
somtimes it is best the other way , that is why i had a sheild lift jumper option on most of my psu ,

hope this helps,
still no luck ?
Best
Dan,


Phrazemaster

Thanks Dan.

Haven't finished yet.

Of the two I posted, which version would you try first?

Thanks man,

Mike
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Thanks Dan.

Haven't finished yet.

Of the two I posted, which version would you try first?

Thanks man,

Mike

the version with no shield attached to ground ,
Dan,

Phrazemaster

Thanks Dan.

Haven't finished yet.

Of the two I posted, which version would you try first?

Thanks man,

Mike

the version with no shield attached to ground ,
Dan,

Thanks Dan.  Neither Version 1 nor Version 2 here have the shield attached to the ground.

Of these two, I was thinking Version 1 is better. It looks like that's what you used. Am I right?

But that also means that the shield wire in the cable is left floating. Is that OK?

Thanks,

Mike
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