Mitsos API 312 / 990 Build Thread
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laddie.music
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Anyone know where I can get the PPA power supply board taht can power 8 channels of api,
The only one I found was this http://www.diyrecordingequipment.com/projects/app-studio-psu2/
but that is APP not PPA?????
and it says it only powers 4 channels
I have 8 mitsos boards...
The only one I found was this http://www.diyrecordingequipment.com/projects/app-studio-psu2/
but that is APP not PPA?????
and it says it only powers 4 channels
I have 8 mitsos boards...
I did that, exactly. Powering 8 boards with PPA PSU. It works well, but if you have any opamps that don't work correctly and at some point short the +- rails (I made at least one with that error), some electrolytic onboard will blow. Just a word of caution, check your opamps before you power them with PPA PSU.
Cheers,
B.
Cheers,
B.
tmuikku said:laddie.music said:
That is the one, it is PPAs naming convention that confuses youJust PM him and he will guide you how to power up 8 preamps with the board.
laddie.music
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http://www.diyrecordingequipment.com/projects/app-studio-psu2/
So where do I pay and order it?, i can't find any contact information for the purchasing of the board....??
So where do I pay and order it?, i can't find any contact information for the purchasing of the board....??
mitsos
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I don't know yet how that site works.
But a note on PSUs. This preamp is made to take a fourth power rail (+12V is what I use) for powering the LEDs. Not 100% necessary to have a separate rail, but it's there if you want it. For any type of 3 rail PSU (PPA, SSL9K, Green PSU, among others) you have to run the LEDs between the positive rail and ground. To do that you'd connect the Led +V to the opamp +V and the Led Ground to the audio ground.
That said, you can use almost any PSU. All of the above, as well as mikefatom's, JLM, and probably 99% of all PSUs on this forum are based on the same or similar parts/schematics, so they will all work the same, especially with a few 2520's which use practically no power. I would just pick the PSU that is geographically closer to you so you get it quicker.
my 2 cents.
But a note on PSUs. This preamp is made to take a fourth power rail (+12V is what I use) for powering the LEDs. Not 100% necessary to have a separate rail, but it's there if you want it. For any type of 3 rail PSU (PPA, SSL9K, Green PSU, among others) you have to run the LEDs between the positive rail and ground. To do that you'd connect the Led +V to the opamp +V and the Led Ground to the audio ground.
That said, you can use almost any PSU. All of the above, as well as mikefatom's, JLM, and probably 99% of all PSUs on this forum are based on the same or similar parts/schematics, so they will all work the same, especially with a few 2520's which use practically no power. I would just pick the PSU that is geographically closer to you so you get it quicker.
my 2 cents.
laddie.music
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martthie_08 said:finally got the faceplate on my unit, have been using it "naked" for the last couple of weeks (sounds great).
More pics and infos at http://homepage.mac.com/marten.thielges/racking/apiX8.html
thanks for this nice project!
cheers, Marten
I'm in the USA does anyone know the depth of this case?, i love how it's compact, I know it's a 2 unit, just don't know the depth, should I just get a hammond with these dimensions?
laddie.music
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Ok Mitsos I found the PPA power supply,
http://www.groupdiy.com/index.php?topic=33576.0
Do I need to upgrade any of the parts if i want to run 8 mitsos with it?, do you know?
http://www.groupdiy.com/index.php?topic=33576.0
Do I need to upgrade any of the parts if i want to run 8 mitsos with it?, do you know?
mitsos
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Well, it's hard to say. the info says limit of 800mA, you can get more if you up the main rectifier and pre-reg caps (assuming a suitable trafo). I would do the following (these suggestions are valid with almost all PSUs available here) :
Swap diode bridge for one with higher current limit (not sure what is spec'd but the common small ones here are 1.5A). You can use single diodes here, like shottkey's (MR851G) but they are rather large and you'll have to solder them together, because the PCB only has 4 holes. Or just go to your local electronics store(if you still have one near you) and ask them for a higher current bridge that will fit the PCB.
Up the pre-regulator caps. IIRC the schematic has 1000uF, I'd stick 2200 or even more if you can fit them.
Make sure the difference between the regulator input DCV and output DCV is less than 10V. The input has to be at least
3V higher than the output for the regulator to work, but to get max current throughput from the reg, you have to stay under 10V difference.
Heatsink the regulators.
That said, you'll need at least a 70-80 trafo for 8 channels. They'll work with much less if you're going straight to A/D, but might choke going into 600 Ohms.
I'd also ask PPA as it's his project and might make further suggestions.
hope that helps!
Swap diode bridge for one with higher current limit (not sure what is spec'd but the common small ones here are 1.5A). You can use single diodes here, like shottkey's (MR851G) but they are rather large and you'll have to solder them together, because the PCB only has 4 holes. Or just go to your local electronics store(if you still have one near you) and ask them for a higher current bridge that will fit the PCB.
Up the pre-regulator caps. IIRC the schematic has 1000uF, I'd stick 2200 or even more if you can fit them.
Make sure the difference between the regulator input DCV and output DCV is less than 10V. The input has to be at least
3V higher than the output for the regulator to work, but to get max current throughput from the reg, you have to stay under 10V difference.
Heatsink the regulators.
That said, you'll need at least a 70-80 trafo for 8 channels. They'll work with much less if you're going straight to A/D, but might choke going into 600 Ohms.
I'd also ask PPA as it's his project and might make further suggestions.
hope that helps!
creal
Well-known member
Hi all,
i have a question about C6/C8 bi polar, i have all the parts except these two capatitors.
So my question is, can i replace this two caps by simple litic or poly?
Does the replacement have an impact on the final sound?
Also, i don't have the 619r in stock can i use a 620r?
Thx for advises
Cheers
Cyril
i have a question about C6/C8 bi polar, i have all the parts except these two capatitors.
So my question is, can i replace this two caps by simple litic or poly?
Does the replacement have an impact on the final sound?
Also, i don't have the 619r in stock can i use a 620r?
Thx for advises
Cheers
Cyril
mitsos
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Hi Cyril,creal said:
yes, you can use a polarized lytic, use the same values and put the positive towards the opamp. Changing these caps around will definitely affect the sound. If you change from crappy caps to anything decent you will hear a huge difference, at least I did. But going from say, a Panasonic bipolar to a panasonic FC, might not give that much difference, they are both excellent caps. Try elna Silmic II, those are great, or maybe try the axial ones from classicapi? I have tried those too, but haven't done any direct comparisons.
The only comparison I've done was Silmics vs Nichicon KZ (top of nichicon audio line) in the audio path of two SB4000 compressors. Neither was bad, but the Silmics were much better. I didn't make any notes, but the mids were much better with the silmics. There were 4 people in the room the day I heard it, and everyone agreed.
No problem, same thing.
good luck!
d
creal
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Hi Dimitri,
thanks for the precious advices
Cyril
thanks for the precious advices
Cyril
Cosmonaut
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I'm finally wiring my 312 pres, and after reading the complete thread I'm little confused...I'm using TS plastic neutrik connector for DI, is this correct?should I use the switching one?should it be TRS? I have read the needs for using TRS switched...but with my bad english skills I can not understand what I should switch...
Thanks in advance.
Thanks in advance.
mitsos
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Hi Cosmo, you only need a TS, but it must be switching (or shorting or normalling, Ive seen all these terms before). It's the kind of TS jack that usually has 4 connections, 2 for tip and 2 for sleeve, where they are connected together when nothing is inserted, but as soon as you plug in, it lifts the connection. "
here is one for sale I found through google (this is TRS though, and PC mount, but same principle):
http://www.tubeampdoctor.com/en/shop_Cables_Jacks_amp_Plugs_Connectors/1_4_Phone_Jack_Jack_plastic_stereo_shorting_CL_309
Plug a cable in to see how it works, see which lead is connected to the TIP and and connect it to DI+ on the PCB. Connect the normalling/shorting TIP lead (the one that gets broken when you plug in) to the DI_SW pad. Niels and I handle the ground/shield differently, I usually connect it to the ground side of C12, he takes it straight to star ground. Do whichever gives you no hum. I also use a shielded mic cable for this, one conductor for +, one for SW, and use the shield for the ground connection. I definitely recommend you use the protection diodes between + and - opamp inputs, as well as the 1K resistor, R11. Niels has told me that he's had a couple of 2520s go to heaven, when a guitar cable was unplugged at the guitar side, and left in the preamp. I tried to reproduce this but couldn't, and the only difference I could find between our builds is that he did not use those diodes (but with the opamp input hanging in mid-air like that, I suppose it's possible that something else could have happened to it).
I hope that's clear, let me know if you need a visual, and I can maybe draw something (very ugly) in corel.
good luck!
here is one for sale I found through google (this is TRS though, and PC mount, but same principle):
http://www.tubeampdoctor.com/en/shop_Cables_Jacks_amp_Plugs_Connectors/1_4_Phone_Jack_Jack_plastic_stereo_shorting_CL_309
Plug a cable in to see how it works, see which lead is connected to the TIP and and connect it to DI+ on the PCB. Connect the normalling/shorting TIP lead (the one that gets broken when you plug in) to the DI_SW pad. Niels and I handle the ground/shield differently, I usually connect it to the ground side of C12, he takes it straight to star ground. Do whichever gives you no hum
. I also use a shielded mic cable for this, one conductor for +, one for SW, and use the shield for the ground connection. I definitely recommend you use the protection diodes between + and - opamp inputs, as well as the 1K resistor, R11. Niels has told me that he's had a couple of 2520s go to heaven, when a guitar cable was unplugged at the guitar side, and left in the preamp. I tried to reproduce this but couldn't, and the only difference I could find between our builds is that he did not use those diodes (but with the opamp input hanging in mid-air like that, I suppose it's possible that something else could have happened to it). I hope that's clear, let me know if you need a visual, and I can maybe draw something (very ugly) in corel.
good luck!
Huh, finally finished my 8 channel box. What an effort without drill press almost 1000 drill actions to make all the holes with 1mm increments hehe. Well, the box has been in use 1,5 years already with 4 preamps and today I put the rest into the box and tested it out. No problems besides some noise when rotating the knobs. Got bourns pots and api knobs from classicapi. The case is properly shielded and grounding should be ok all around. I'll post if I tackle the noise issue.
almost 1000 drill actions to make all the holes with 1mm increments hehe. Well, the box has been in use 1,5 years already with 4 preamps and today I put the rest into the box and tested it out. No problems besides some noise when rotating the knobs. Got bourns pots and api knobs from classicapi. The case is properly shielded and grounding should be ok all around. I'll post if I tackle the noise issue.
mitsos
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Hi,
noise when ""rotating" knobs is a sign of DC through the pot, not a good thing, check the cap going from the pot to ground for value and correct polarity. If it's polarized, the plus should go towards to pot.
If it's an issue like what Mrcase had a few months back (don't know how that worked out in the end) that's a sign of insufficient shielding by the front panel. The same thing as removing the top panel and putting your hand close to the opamp, if using a DIY unshielded opamp.
Sometimes anodized faceplated can create this problem as anodizing is not electrically conductive. In these cases, it's good to have a second metal faceplate behind the front, but that makes things more complicated, so a work-around might be scraping off some anodizing from the back of the faceplate where it touches other bare metal, or maybe even inside the mounting screwholes. If you have the pots mounted offboard you could try a shielded cable with the shield tied to the case, not audio ground.
good luck, post back.
noise when ""rotating" knobs is a sign of DC through the pot, not a good thing, check the cap going from the pot to ground for value and correct polarity. If it's polarized, the plus should go towards to pot.
If it's an issue like what Mrcase had a few months back (don't know how that worked out in the end) that's a sign of insufficient shielding by the front panel. The same thing as removing the top panel and putting your hand close to the opamp, if using a DIY unshielded opamp.
Sometimes anodized faceplated can create this problem as anodizing is not electrically conductive. In these cases, it's good to have a second metal faceplate behind the front, but that makes things more complicated, so a work-around might be scraping off some anodizing from the back of the faceplate where it touches other bare metal, or maybe even inside the mounting screwholes. If you have the pots mounted offboard you could try a shielded cable with the shield tied to the case, not audio ground.
good luck, post back.
hey!
I still have this issue but I´m living with it at the moment. though I will spend more time with the unit soon. Maybe this is related to the bourns potentiometers mounted offboard? I´ve checked continuity between the pot and the rest of the case. It´s on all 4 channel btw...
good look with yours and lets keep each other updated!
cheers
M
I still have this issue but I´m living with it at the moment. though I will spend more time with the unit soon. Maybe this is related to the bourns potentiometers mounted offboard? I´ve checked continuity between the pot and the rest of the case. It´s on all 4 channel btw...
good look with yours and lets keep each other updated!
cheers
M
seavote
Well-known member
after a failed attempt at a direct M1 clone (cut traces, jumping offboard to a home made pcb then back again,as well as a DIY 990) just to much to troubleshoot.
ive started again and im keeping it simple. i'll use the recommended 604 ic. ive been able to get my current psu down to 22.75 V + and -, with just a trimmer adjustment .from experience do any of you think this will be too high. i thought i read some of you were running it at 24V with no problems.
also what type of molex connectors are you guys using for the bias input and servo in/out jumper? the "normal size" that most guys on the board use dont seem to fit along with the DIY990s. do they fit with John Hardys 990's ?
for the +18V i was planning on taping off the +24V leg of the psu and add another stage to the psu. is this how it should be done? can anyone recommend some starting component values to acheive near 18v? any help is appreciated. and mitsos thanks for the 2 pcbs.
8) 8) 8) 8) 8) 8) 8) 8)
ive started again and im keeping it simple. i'll use the recommended 604 ic. ive been able to get my current psu down to 22.75 V + and -, with just a trimmer adjustment .from experience do any of you think this will be too high. i thought i read some of you were running it at 24V with no problems.
also what type of molex connectors are you guys using for the bias input and servo in/out jumper? the "normal size" that most guys on the board use dont seem to fit along with the DIY990s. do they fit with John Hardys 990's ?
for the +18V i was planning on taping off the +24V leg of the psu and add another stage to the psu. is this how it should be done? can anyone recommend some starting component values to acheive near 18v? any help is appreciated. and mitsos thanks for the 2 pcbs.
8) 8) 8) 8) 8) 8) 8) 8)
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