MA1 GERMANIUM mic pre support thread

[Potato Cakes]

Then you have to cut a notch in the back of the Grayhill switch. I recommend removing the tiny nut first.

 

[Potato Cakes]

Then I soldered leads that would attach to the stepped gain switch PCB from Classic API. Where you see the brown wire there is already a solder point  available that is connected to the ground plane. The blue has to attached to a preexisting solder joint, which is on the PCB trace that connects C5 and C6. With these colors as they are shown brown would attach to solder pad 3 on the gain switch PCB and the blue would connect to pad 1.

You can see C29 that is mounted parallel to the PCB (solder legs bent 90 degrees).

I should also recommend putting a small piece of electrical tape over the solder pads on C29 on the top side of the PCB to prevent any shorting since the back metal cap of the Grayhill switch is going to be pressed right against them.

You may notice the not so great soldering job. As I have stated earlier I have been abusing both of my MA1's to experiment with mods. I've swapped out components in this area several times.

I hope someone finds this helpful. Or hilarious.

Paul

 

[Krcwell]

Excellent work!

I've been thinking for a while of making another pair of these pre's as a "deluxe" version doing just what you did. I hadn't even begun to consider the logistics of how to fit everything, so I really appreciate the detailed explanation.

Did you end up using the DI switch for a HPF?

 

[Potato Cakes]

I did use the DI switch for a HPF which definitely adds to this preamp's versatility. Email Pier for those instructions.

Thanks,

Paul

 

[ppa]

I did use the DI switch for a HPF which definitely adds to this preamp's versatility. Email Pier for those instructions.

Thanks,

Paul

thanks for posting
I am going to send him an email with the mods and if for you and him the mod is fine I will post the mod here.



Pier Paolo

 

[Siegfried Meier]

Hey guys,

I just finished a pair of these and they sound incredible - all working on the first fire up, except for the DI?  I used the jack from Classic API, but neither of the 2 channels work?  I can hear signal if the jack is plugged halfway in, but not otherwise…has anyone else had issues with this?

Any help appreciated.
Thanks!
Sig

 

[[silent:arts]]

How did you wire it?
Bridge Ring and Sleeve, and while you are there the switched and the unstitched side to make sure.

 

[Siegfried Meier]

Documentation was incorrect in the photographs - it's been fixed, and these babies are now rocking.

Love 'em!

 

[kosi]

Hi Pier Paolo,
on my Version 3 PCB from 2015, I have a J1 and a R32, these don't show up in the BOM. I attach a pic.
What values do I have to use here ?

one more hour and I'm finished !

thanks,
Andreas

 

[ppa]

Hi Pier Paolo,
on my Version 3 PCB from 2015, I have a J1 and a R32, these don't show up in the BOM. I attach a pic.
What values do I have to use here ?

one more hour an I'm finished !

thanks,
Andreas

thanks for the question,
R32 connects the analog ground to MA1's chassis,  R32 = 10 ohm.
Usually R32 is not needed (the previous versions of MA1 didn't use it).
J1 is the jumper to use R32 or not.

Pier Paolo

 

[kosi]

Thanks Pier Paolo.
In which scenario would you recommend it ?

 

[[silent:arts]]

There is no need to connect ground to chassis in the modules.
At least I don't do this.
Chassis and GND is connected together in the PSU.
If you connect it together in the module use at least the 10Ω Resistor to avoid loops.

Did you find the 180pF? 

 

[kosi]

Hi Volker,thanks for chiming in.

And yeah, I bought the 180 on ebay, a bit expensive (10 pcs for 2,90€) but: SUPERQUICK  ;D

 

[kosi]

Up and running !
The first test was flawless.

While assembling the transformer, I recognized, that I hadn't ordered the screws for the EA2503, so I had to improvise and used cable ties 

I used Lundahl 1576 and the EA2503

The next days I will assembly the second one and will try the HPF mod,
a BIG thanks to Pier Paolo and all the rest of this fabulous board !!!

 

[ppa]

Many thanks for comments ! 

 

[kosi]

Here are 2 pics
the sound is really outstanding !!!
And I really like the sound of the DI Box a lot, so I won't do the HPF update.

One little thing: the colors of the faceplate are different...

 

[kosi]

2 different colors

 

[Winetree]

2 different colors

One is brushed and the other looks painted.

 

[ppa]

thanks for comments

yes,  one is brushed and the other is grey painted.
They are from two different stock of front panels.

 

[ppa]

2 different colors

so I will send you another front panel for getting them the same.

Pier Paolo