MA1 GERMANIUM mic pre support thread
- Thread starter ppa
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Mrosso
Well-known member
pier,
Thanks. Looks like I reversed Q2 and Q4. Hope I didn't destroy anything other than the two resistors.
Thanks. Looks like I reversed Q2 and Q4. Hope I didn't destroy anything other than the two resistors.
I think no, Q2 and Q4 are rated for 4A max and the currents on burned resistors was of 1.5A (circa) so they were under these 4A.
Let me know if the preamp runs in any case, please.
BTW I can send you all set of transistors if you want, but first all I suggest you to test the preamp with those just assembled.
thanks
cheers
Let me know if the preamp runs in any case, please.
BTW I can send you all set of transistors if you want, but first all I suggest you to test the preamp with those just assembled.
thanks
cheers
mus1k_freak
Well-known member
well i fired it up and no sound came out, boo. it may be this ginormous output transformer i have, i matched the colors on the wires but maybe it doesnt line up to what is on the pcb, everything i think looks right, neither of the led's came on either, short lead should be in the gnd hole no? ok checking the carhill diagram it definitely doesnt match the board, so ill fix that and report back, still dunno why the led's dont work, backwards i guess
edit 2: leds were backwards, thats fixed now, ordered the suggested output transformer from classic API keep ya posted!
edit 2: leds were backwards, thats fixed now, ordered the suggested output transformer from classic API keep ya posted!
3nity
Well-known member
This is more than matching the colours with the pcb.
you need to properly match the transformer primaries wires to pcb !!
you need to properly match the transformer primaries wires to pcb !!
mus1k_freak
Well-known member
Yup I opened the schematic and looked how the capi tranfo is wired and checked the carnhill and matched them that way, should of done that before I soldered them all in haha was hoping it was more like the input transformer and would match up
Hi all,
carnhill is a very nice out transformer but I have not written the labels on MA1's PCB for it , infact it is not listed on MA1 BOM. I have designed the labels for the cinemag CMOQ-2S and the classicapi 2503. However this mistake does not broke the preamp.
BTW there is 3 holes for an aux mic input on the PCB that are on the bottom of your trasformer as it is placed on the same PCB. Maybe the transformer's chassis are shortcutting them too, please you should isolate them from the transformer chassis.
kind regards
Pier Paolo
carnhill is a very nice out transformer but I have not written the labels on MA1's PCB for it , infact it is not listed on MA1 BOM. I have designed the labels for the cinemag CMOQ-2S and the classicapi 2503. However this mistake does not broke the preamp.
BTW there is 3 holes for an aux mic input on the PCB that are on the bottom of your trasformer as it is placed on the same PCB. Maybe the transformer's chassis are shortcutting them too, please you should isolate them from the transformer chassis.
kind regards
Pier Paolo
mus1k_freak said:well i fired it up and no sound came out, boo. it may be this ginormous output transformer i have, i matched the colors on the wires but maybe it doesnt line up to what is on the pcb, everything i think looks right, neither of the led's came on either, short lead should be in the gnd hole no? ok checking the carhill diagram it definitely doesnt match the board, so ill fix that and report back, still dunno why the led's dont work, backwards i guess
edit 2: leds were backwards, thats fixed now, ordered the suggested output transformer from classic API keep ya posted!
C31 is not soldered on PCB , what's the transformer you are using on input?
mus1k_freak
Well-known member
input is a cinemag cmmi 10pca, i just have a 150k load resistor and left out the zobel
mus1k_freak
Well-known member
the germanium transistor was rotated to the wrong postion, so i fixed that, but the output is VERY low turned all the way up i have to hit the mic to get any kind of noise to come out, any ideas?
3nity
Well-known member
what about the DI, try an instrument and see how the gain acts.
mus1k_freak said:
I hope it not was broken by wrong position, MA1 is one of the most quiet preamp on 500 rack , it is very quiet.
BTW Is the germanium transistor placed as indicated here?
http://groupdiy.com/index.php?topic=49710.msg647169#msg647169
buildafriend
Well-known member
sr1200 said:
Did anything ever come of this? I would love to hear shoot outs of what you have. I did a good one recently between a BA2 clone, an orange 86, a MILA, an access 312, a vp26, and a vp312. I'll trade you my audio samples for yours.
I want to hear an a/b between the MA1 and a vp312..or 26
mus1k_freak
Well-known member
this is how i have it now, but a previous post says differnt and thats what i went by, now its correct, maybe ill pick up a new ac126 and see if that solves anything
ppa said:
buildafriend said:
Actually we did a pretty informal shoot out again this past week. I compared the MA1 with EA trafos to 3 access 312 with cinemag trafos (one with PPAs germanium DOA, a whistlerock 918 DOA and a whistlerock 2520 doa) Also compared it to Martins Ez1290 and a Daking preamp. Was expecting to hear very little difference between the access 312's but depending on the source of the material, it was pretty eye opening.
EDIT: the biggest difference we didn't expect was in the EA trafos, vs the Cinemags both using germanium opamps... HUGE tonal difference between the 2 transformers.
If you'd like shoot me your email address I can send you files. We did guitar tests mostly, (electric w. overdrive using an sm7b, an acoustic strummed using the 87i clone and a fingerpicking acoustic also with the 87i clone)
3nity
Well-known member
id like to hear those tracks.
send em to me at jorge_aristondo AT yahoo DOT com
please!
send em to me at jorge_aristondo AT yahoo DOT com
please!
K i sent a we transfer out to a couple folks that wanted it. (full quality 24bit 48k wav files)
Heres one thing i noticed with the EA transformers. When running some frequency sweeps through all the different pres, I noticed somewhere after about 500hz or so, the cinemag transformers took on some extra harmonic content (2nd and 3rd predominantly) where below 500 there wasn't much. The EA transformers were kind of opposite, they had a LOT of harmonic content UP to 500 and it kind of rolled off after that. (which is probably why the MA1 is my GOTO on direct electric bass
) The Carnhill transformers had harmonics from bottom to top but not quite as much as either the EA or the Cinemags at their highest. (so more consistent, just not as rich) Same could be said for my LA-610 from UA (tube pre) Which had a little more than the carnhills and were present from bottom to top. Didn't test my other pres, but I plan on doing a nice comprehensive test with some videos after new years (wife got me a lola kit for xmas I cant wait to pop together! )
Heres one thing i noticed with the EA transformers. When running some frequency sweeps through all the different pres, I noticed somewhere after about 500hz or so, the cinemag transformers took on some extra harmonic content (2nd and 3rd predominantly) where below 500 there wasn't much. The EA transformers were kind of opposite, they had a LOT of harmonic content UP to 500 and it kind of rolled off after that. (which is probably why the MA1 is my GOTO on direct electric bass
) The Carnhill transformers had harmonics from bottom to top but not quite as much as either the EA or the Cinemags at their highest. (so more consistent, just not as rich) Same could be said for my LA-610 from UA (tube pre) Which had a little more than the carnhills and were present from bottom to top. Didn't test my other pres, but I plan on doing a nice comprehensive test with some videos after new years (wife got me a lola kit for xmas I cant wait to pop together! )
