Unknown (aphex?) api 500 series preamp problem

[bram]

Hi, I recently bought an aphex lunchbox 4b-1 for cheap, and there were two preamps in it (called: mp-1). On one of the two i found "aphex" on a chip so they must be aphex made. These modules fit perfectly in my API lunchbox, but the sound is a problem. The output volume is very very low, even if I see the peak led clippig. The standard values on the Aphex lunchbox are set to high input, high output, and here the output is fine (even if i use an unbalanced cable from mic to lunchbox and from lunchbox to audio interface). There is also a 48 volt switch, which is very curious given the fact that the aphex lunchbox has no xlr connections. If I engage that switch, a green led starts shining. Now, if I put the modules in the API rack, the green phantom power led won't shine.
So i got several questions: why is the output too low if I put the aphex modules in the API box? and is there a way to make phantom power work in the API box?
Have these modules any value at all or should I sell them to the next guy who thinks he could fill his rack on the cheap?

Thanks,
Bram

Some pictures:

[JRE Productions]

Hmm. I don't know these specific modules, but isn't there supposed to be an output transformer where the big hole is? Can you get schematics?

Whats on the cheap? I am looking for some 500 series cards to make some DIY racks. These would not have to work, but would be cool if they did. Basically I need the a card with the right size, shape and connector to make a prototype rack that would be universal for 500 series cards.

Joe

Pin 14 is your 48V in the standard API 500 series modules. Trace the edge connecter in your aphex lunchbox and see if that is were the 48 V is applied. If there is no 48V applied through the Aphex box, then it is configured differently. All API 500 series modules accept for the 560 graphic and some old 550 series EQs grab there 48V from pin 14. If you have any of the modules mentioned before, cut the trace or you'll burn up the module, to some degree anyways.

Basically if, your system is compatible with API series 500 modules, then pin 14 is 48V

[bram]

Really? I thought 48v was on pin 15. Anyway, pin 3, 6 and 15 are not in use on the aphex preamp, as far as I can see. Pin 5 and 7 are connected between each other. On the api 512c pin 6 and 11 are not connected.
Anyone sees what's the difference between the api pinout and the aphex pinout?
Here's a picture of the inside of the lunchbox:

[bram]

hmm why do so many manufacturers call there first preamp "MP-1" ? It's horrible to look after more information about these modules on the internet. And Aphex won't answer.
Can anyone confirm the pin 14 or 15 phantompower or see any differences between the api lunchbox and the pictured aphex lunchbox?

Muchas gracias,
Bram

[JRE Productions]

I am thinkinig the aphex is set up for -10. I dont see the output transformers either. On api, thats what turns the unballance signal into the ballanced, and adds color.

If this is true, that means they are not set to drive the +4.

I can check tomorrow for the pin out on 500 rack. I looked and thought it was on 15. I think power is on 12, 13 and 14, but I need to check.

I am still interested in the aphex gear if it does not work for you.

JD

[JRE Productions]

http://www.apiaudio.de/512.pdf this is the pin outs for 500 stuff. Yes 15 is the 48 volts.

Joe

[bram]

well i bought the whole thingie for 250 euro. If the lunchbox would be worth 150 then the preamps would go for 50 euro each. But I prefer European transactions.
Anyways, I'm a buyer, not a seller. I haven't sold a single piece of the music equipment I bought. I will try some more time and compare the mic pres to see if they are worth there 50 bucks. If not i will let you know. Now i'm gonna compare it to my apis and the daking mic pre I just bought. The price was so silly i feel guilty and it works just fine (although I still have to check if they haven't removed the transformers as is apparently the case with the aphex ones).
Any input on these mysterious aphex preamps is still appreciated!

bram

[Jeff Goodman]

I wouldn't be so sure that any transformers were removed from the Aphex mic pre's. I've never heard of those particular modules, but the ones that I am aware of, the CX-1 and EQF-2, could be bought new with or without output transformers.

When they didn't have output transformers the output was capacitor coupled. Is there a capacitor of maybe 470 or 1000mFd at the output?

Jeff

[bram]

Jeff you might be right. I don't know nothing about capacitors, but there are at least three blue (well, on the first picture I uploaded you can see clearly one blue and two purple) tubes with 470mF25v on. Next to the two purple capacitors are two red boxes that say 6,8mF 100- 5%A (where in all cases "m" is the greek micro symbol).
Remains the question why that preamp isn't completely API compatible. On the aphex lunchbox you can change the internal input and output level by changing the combination of little black wires (the small black lines you see on the picture of the inside of the aphex lunchbox) I don't know if you can do that with the api lunchbox.
hmm sorry for this very non-professional description

thanks,
bram

[bram]

Update:
after the vacations I started looking at these preamps again, changed positions in the lunchbox etc. First I got a sound full of crackles, and after a small cleaning of the connectors there it was: right sound at right volume!! So now these preamps officially work within an API lunchbox. Yesss!
That also means my aphex lunchbox is for sale.
So from now on, include the aphex mp-1 within the ever growing list of 500-type preamps. (damn Im so excited that a newbee like me can actually contribute something to the gearslutz community

bram

Yeah, I was wrong. Pin 15

[6dyslexicelephnt]

I can't get the phantom power to work on my aphex 4B-1 and I would like to check the power going to pin 15 so that I can know if it's being supplied to my Great River MP-500NV preamp. Thanks

[bram]

The Aphex 4b-1 as no phantom power.

Best regards,
Bram

[6dyslexicelephnt]

thank you! damnit!