MA1 GERMANIUM mic pre support thread

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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.
 
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 :):).
 
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!
 
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
 
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.
 
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 75:(150+150), so should work fine, wouldn't it?

https://utmindustry.com/wp-content/uploads/2023/03/1645133609UTM_Catalog2B.pdf
 
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.
 
Regarding the UTM3523, it has different dimension vs. the 3503 so it doesn't fit the MA1 PCB.
 
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.
 

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