MA1 GERMANIUM mic pre support thread

[TillM]

You can use UTM 2503 as Output Transformer.
For input you can use Cinemag, EA, Lundahl or Haufe.

 

[ppa]

I agree with Till

 

[soloyosoyyo]

Hi, thanks for the answer.
I suppose that the UTM you say is UTM 3503, the one you mention does not appear on their website.
Do you think its a good combo Lundhall and UTM in this preamp?
Thanks.

 

[ppa]

Yes, the trasformer is the UTM 3503

 

[ppa]

yes, the Lundahl LL1576 is good for input

 

[soloyosoyyo]

Cool, thank you for the answers.
Now i know that i could find all the "hard to find" parts of the project.

 

[soloyosoyyo]

Hello again. Finally i got cinemag cmmi-8apc for the input and cinemag cmoq2 for the output. I hope these two sound well in the project .

 

[soloyosoyyo]

Hello, can somebody tell me if i am correct .
With cinemag cmmi-8pca:
R21 100k
R22 9,76k
C31 22pf
Thanks.

 

[ppa]

yesss, they're right.

 

[ferrochrome]

Hey ferrochrome,
Looks great, also the other pres in your lunchbox.
Which resistors do you change to get lower output ?
I want to use the MA1 for my drums.
I can't wait till they get back in stock.

Hi TillM, stumbeled on to this thread again after several years. Thanks for your comment! Here's my super late reply to your question: I didn't change any resistors, I'm just padding the output with the next equipment in line, but that's rarely necessary anyway, it usually gives me the sound I want without padding. Did you get to build yours yet? Fantastic pre!

 

[TillM]

Yes in the meantime I think I build 6 or 7.
But 4 I build for friends of mine, who hear mine and also wants them.

 

[kato]

These are the 2 current limiting resistors for the LEDs, correct?

I want to make the LEDs less bright.

 

[ppa]

Hi

thanks for your question,
the LEDs brightness changes with the values of R33 and R13. More precisely, in this case, the brightness decreases linearity as these two resistances increase. Being, in this case, the law linear between brightness and resistance, and, being the two res of 4.7k, to reduce the brightness for half brightness, these two res should be two times bigger so 2 x 4.7k = 9.4k, so in practice, 10k.
It goes without saying that, if you want a value between 1 and 2 times the original brightness, you should use a value between 4.7k and 10k. For a brightness 3 times less than the original one the value is 15k.

best regards
Pier Paolo

 

[ppa]

I add that the sensation of brightness of the human eye is not linear so I recommend focusing on 10k to see a good result.

 

[Janus Audio]

I want to use UTM transformers for my MA1s and found that th UTM3503 does not have exactly the same layout as the EA2503. It has two primaries and two secondaries with 150 ohm each (150+150:150+150).
So do I have to get solder the primaries in parallel to get the 75:300 as in the EA2503.
Another option would be the UTM3523 which is 75150+150), so should work fine, wouldn't it?

https://utmindustry.com/wp-content/uploads/2023/03/1645133609UTM_Catalog2B.pdf

 

[ppa]

The MA1 uses the same API312 configuration for the EA2503. You can use the UTM3503 with this configuration, so one primary only and the two secondaries in series configuration, this configuration is a 150 : 600. The other primay is not connected. I will send you the connection list.
I didn't test the UTM3503 but people said me that it's very fine.

 

[ppa]

Regarding the UTM3523, it has different dimension vs. the 3503 so it doesn't fit the MA1 PCB.

 

[ppa]

the UTM3523 is smaller.

 

[Janus Audio]

Awesome, thank you! So for the UTM3503 I assume it's black/red leads to green/blue inputs on the PCB. And out put GRN/PKN-VIO/ORG leads of the transformer to brown/orange-red/yellow on the PCB.

 

[Janus Audio]

And the restisors and caps are as in EA2503?
R21 not used
R22 10k
C31 220pf (or 270pf)