MA1 GERMANIUM mic pre support thread
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mus1k_freak
Well-known member
whats the S for in the germanium spot?
S is shield , but only some ge transistors have it, AC126 have not it.
S on Q1 PCB place is connected to the collector hole, so S hole on PCB is connected to C hole.
C is the hole for the ge tr collector, if you want, you can use S hole to connect AC126's collector instead the C hole.
S on Q1 PCB place is connected to the collector hole, so S hole on PCB is connected to C hole.
C is the hole for the ge tr collector, if you want, you can use S hole to connect AC126's collector instead the C hole.
mus1k_freak
Well-known member
changed the ac126 and still have no sound, if i turn it all the way up and play a really loud source into it i get a little level but nothing audible, driving me nuts i usually dont have problems like this, im sure im over looking something simple, only thing i can think of is a input transformer issue maybe? im using a cmmi 10pca, just pulled out the input transformer, and it is in the correct position, im running it with no zobel or load resistor, but that shouldnt affect volume level
ok it looks like the silkscreen on the pcb is wrong for the ac126, ill get the input trans put back then ill wire it acoring to the ac126 pinout and not the silkscreen and see what happens
ok got the germanium in right and the DI works now
just gotta figure out what i did to mess up my mic input
could someone post a picture of the bottom of the board for me? just wanna check my soldering around my transformer, thanks!
ok it looks like the silkscreen on the pcb is wrong for the ac126, ill get the input trans put back then ill wire it acoring to the ac126 pinout and not the silkscreen and see what happens
ok got the germanium in right and the DI works now
just gotta figure out what i did to mess up my mic input could someone post a picture of the bottom of the board for me? just wanna check my soldering around my transformer, thanks!
3nity
Well-known member
Does it work the same with condensers and dynamics?
I see the pcb in dual sided, did you make sure to let some space between pcb and transformer?
I see the pcb in dual sided, did you make sure to let some space between pcb and transformer?
mus1k_freak
Well-known member
i got it facing the right way, i even un soldered it to make sure, on the input i read 20.3 everything else looks good, got me stumped. ill try a few more things tomorrow
mus1k_freak
Well-known member
Good news, Victory! 8)
The issue was the input transformer, the cinemags are NOT compatible with this pcb, as it shorts the ground on the casing to the output of the transformer, so to get it to work i soldered in a cm 2480 backwards, input from the phase flip switch and output across R21. worked like a charm, its a really quiet and dark mic pre, but i think paired with the right mic and source it could definitely sound great, hoping to get it all put back together and try it on some guitar tracks tomorrow. thanks again for all the help and support! next time ill just use the transformers suggested
The issue was the input transformer, the cinemags are NOT compatible with this pcb, as it shorts the ground on the casing to the output of the transformer, so to get it to work i soldered in a cm 2480 backwards, input from the phase flip switch and output across R21. worked like a charm, its a really quiet and dark mic pre, but i think paired with the right mic and source it could definitely sound great, hoping to get it all put back together and try it on some guitar tracks tomorrow. thanks again for all the help and support! next time ill just use the transformers suggested
3nity
Well-known member
I dont think this is the problem here
Classic EA2622 and cinemag are compatible... If cinemag dont work in this pcb then EA2622 wont work wither.
Did you made sure that when you solder the 10pca to board you left some space between pcb and transformer?
Thanks
Classic EA2622 and cinemag are compatible... If cinemag dont work in this pcb then EA2622 wont work wither.
Did you made sure that when you solder the 10pca to board you left some space between pcb and transformer?
Thanks
mus1k_freak
Well-known member
It looks like pins 6 7 8 are all connected I guess those three are area supose to be case ground xformer ground and bottom of the coil and all tied together? I tried it 3 different times and checked the pinouts and I couldn't get it to work, checked with my ohm meter to make sure nothing was shorted to ground that wasn't suppose to be, now that I think about it it looks like it should if you follow the traces, I did find this transformer in the spare parts box , maybe it's just shot
3nity
Well-known member
Transformer Shot? pretty much that is!
I saw the pcb underneath and the way the transfo is wired it is correct.
So the transformer gone bad its pretty much it!
I saw the pcb underneath and the way the transfo is wired it is correct.
So the transformer gone bad its pretty much it!
mus1k_freak
Well-known member
I gotta stop all these "spare parts" builds, trying to use up all my left over parts, sometimes you save money and sometimes you pull your hair out
mus1k_freak said:Good news, Victory! 8)
The issue was the input transformer, the cinemags are NOT compatible with this pcb, as it shorts the ground on the casing to the output of the transformer, so to get it to work i soldered in a cm 2480 backwards, input from the phase flip switch and output across R21. worked like a charm, its a really quiet and dark mic pre, but i think paired with the right mic and source it could definitely sound great, hoping to get it all put back together and try it on some guitar tracks tomorrow. thanks again for all the help and support! next time ill just use the transformers suggested
very good,
regarding the dark sound , MA1 does not sound dark so I think that the 2nd AC126 gone damaged when soldered inverted the first time. So will send you another one. Regarding the input transformer it may be damaged. I have tried a cinemag CMMI8PCA and it works inside MA1.
mus1k_freak
Well-known member
The dark sound may be due to the cm2480 transformer, I'll see if I have any others to try, on the ap126 mine doesn't seem to sit as pictured in yours, I'll post a picture of that tonight to verify, though I gave decent volume level so assume it's correct
Hi. I´m about to build this pre and reading through the posts I´ve got a couple of questions:
- R16=10M or nothing on somebody´s BOM. My BOM just says 10M. Is it for different PCB versions or just different aplicattions ? (di bass, keyboards...)
- Cut trace between C4&C8 and make the solder joint as in the picture (2nd ver. pcb). Does anybody has the picture? How can I make sure mine is the 2nd v pcb?
Also I´d like to know about EA/Cinemag trafos in this pre. For what I read my guess is Cinemag would put things a little more upfront? More presence? Maybe a little bit more compressed sounding?. Maybe I´m totally wrong... Any thoughts would be great Thx a lot
- R16=10M or nothing on somebody´s BOM. My BOM just says 10M. Is it for different PCB versions or just different aplicattions ? (di bass, keyboards...)
- Cut trace between C4&C8 and make the solder joint as in the picture (2nd ver. pcb). Does anybody has the picture? How can I make sure mine is the 2nd v pcb?
Also I´d like to know about EA/Cinemag trafos in this pre. For what I read my guess is Cinemag would put things a little more upfront? More presence? Maybe a little bit more compressed sounding?. Maybe I´m totally wrong... Any thoughts would be great
Thx a lotthanks for posting,pachi2007 said:
in that version there is a mistake, as in the other two versions there is a ground plane on the PCB top layer.
The mistake is that this ground plane is not connected to the analog gnd, so it should connected manually with a solder joint. MA1 has a star ground and the star ground point is made with an hole.
First all, should be removed a bit of the ground plane's solder near the star ground point hole.
At this point is possible using the zone of the ground plane, with the solder just removed over, to connect both the ground plane and the star ground point hole making a solder joint as in pic attached.
Pier Paolo
