GT Microphones design (LA parts sale)

[ChuckD]

Have a look at the schematic posted by Jakob for the MD1 and others the 9 pin connectors only really used 7 of the pins. So I think a standard supply would work just fine. What model did you grab?


-Chuck

 

[maxwall]

chuck is right , 7 pins

any 7 or higher pin connector can be used, the supplies output 120V B+, and either 12 or 6 Volts filament and mic signal output all on the same connector. and their easy to make , parts are easily available to build one. Infact many of the chinese made mics have the same power requirements as they run the same tubes.

Anyone interested in a PCB run for mic powersupply boards ?

 

[gyraf]

PS-1A Power supply:

http://www.twin-x.com/groupdiy/albums/userpics/GT_PS-1A.gif

Jakob E.

 

[ChuckD]

I picked up 2 GT supplies that I am going to fix. Thanks Jakob!

Also I would not bother having PCBs made. You can order a complete PSU from Alctron Directly for 28 USD each. The shipping is a little high but if you get a group buy together you may find that whole supplies can be had for only a few dollars more then PCBs!

I just ordered a (Mic "APEX460" with Supply) direct and I ordered a spare supply and shock mount for my G7 so I didn't have to build one! Lazy me! The whole thing broke down as:

APEX460 type with PSU, shock mount, and case  - 90USD
Spare Supply - 28USD
Spare Shockmount - 8USD
Plus
Shipping 135.60 USD


Something to think about.

-Chuck

 

[maxwall]

Ordered direct ..... where ?  90USD thats cheap. I think  a lot of DIY'ers here including myself would like to order direct , Direct from Alctron you mean ?  can you help with more info on this ? or PM me I'll keep it low key , promise.

 

[ChuckD]

PM sent ...

-Chuck

 

[ericjazz]

Hello,
I'm trying to build a psu according to Jakob's schematics (thanks Jakob!). I've found BU806 Dartlington transistor (Mouser #:512-BU806) but not the BU or BV85. Could someone tell me what equivalent transistor to use ? Next, I'll try to simulate this psu in order to choose the right transformer (secondaries voltages). And maybe I'll try to design a pcb that fit the PSM box. Btw, It seems that 5 pin connectors are ok (+B, fil, audio+, audio- and gnd). Feel free to correct me...
Thanks in advance for your help.
Eric

 

[doubleroger]

I think 5 pins is ok too.
Have you finally found the capsule you were looking for ( I saw your post on audioaddict).
I would be very interested in knowing the secondary voltages needed in the psu too!
Why not breadboard the psu, by the way?

 

[ChuckD]

So I was comparing the schematic posted by Jakob above for the PSM1 and my broken PSM1 that I got for cheap at the Big sale last fall.
They are not the same at all.

I decided to scan in the PCB into Eagle CAD and reverse engineer it for everyone to use. Here is what I have:

Are there any corrections that someone wants to point out? I did this rather quickly late last night.
If anyone wants the BRD eagle file just throw me an email and I send it to you.

I was thinking I might change this PCB to match Max's MK7 PSU? Is that version better then this one for noise?
Other comments?

-ChuckD

 

[MikoKensington]

Not that they are of much relevance, but here are pics of my early MD1, shipped in converted Case Logic cassette tape organizers.

http://img.photobucket.com/albums/v473/MikoKensington/MD1a.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1b.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1c.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1d.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1e.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1f.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1g.jpg
http://img.photobucket.com/albums/v473/MikoKensington/MD1h.jpg

 

[synthetic]

Groove Tubes is still in business and is now a division of Fender. Aspen told me they had no plans to discontinue the pro audio gear. He is just retiring.

 

[3nity]

Will the MD1 work with a Peluso capsule or something similar??
I tried some electret capsules microphones before and didnt liked them.


Thanks.

 

[3nity]

BUMP.

 

[rodabod]

Will the MD1 work with a Peluso capsule or something similar??
I tried some electret capsules microphones before and didnt liked them.

You might be able to get it to work if you rely on grid leakage alone, but a possibly simpler option would be to make a 1M/1M voltage divider from B+ to ground, tie the node to the backplate, tie the diaphragm to ground, then couple the backplate to the grid with a 1nF capacitor.

 

[3nity]

I'm not sure i got it really well.
But heres me trying to figure it out.

Thanks.

 

[3nity]

Hey Roddy.
The capsule i have right now its a CEK367 style.

 

[rodabod]

Do you want switchable polar pattern?

The mic doesn't have a controllable pattern voltage to permit this at the moment.

 

[3nity]

Do you want switchable polar pattern?

The mic doesn't have a controllable pattern voltage to permit this at the moment.

Not really....not interested at the moment.
I really want to focus on making it work first.

Thanks.

 

[Marik]

I'm not sure i got it really well.
But heres me trying to figure it out.

Thanks.

Hi 3nity,

Some observations with your schematics.
The capsule bias is incorrect and the mic won't work as drawn.
2G grid resistor might be fine for JFET, but is way too high for tube.
Did you draw the curves for the 1st stage?
If you want to make an output CF why wouldn't you go direct coupled?
The cathode resistor of 2nd (CF) stage looks like very low value, so most likely you are putting way too much current through the tube. Have you looked at the curves with that value?

Best, M

 

[3nity]

Sorry Marik.
I barely understand microphones.
This schematic its from the Groove Tube MD1B tube mic.
It comes with an electret capsule.

Now i;m trying to put it to work with a CEK367 that i own..
The only mods i did to the schem its adding 2 x 2M resistors as voltage dividers as sugested by Rodd.

But any input its more than welcome!

Thanks