Calrec AX3797 AX3798 schematics & pinouts

I've bought some of these AX3797 and AX3798 modules recently.

They look to me like together they could form a sub mixer (5 channel mono to single stereo).
I saw references to other AX modules being "Audience miXers."

The preamps have partial discrete analogue front ends with an on-board minature transformer feeding dual (balanced) long-tailed pairs with a programmable current sink. Looks like that was a common design block on the Q series as I've seen that sort of layout on other cards.

I've made a start at tracing out the pins and schematic, and I think I can work it all out myself although it will take time.
3797 has 3 input channels with L+R bus & mono PFL out. Although it'll be simple to tap the output of the 3 channels separately before the pan pot.
3798 has 2 input channels and one stereo output.

Anyone else interested in the information?

Work so far attached, which I think covers all the major audio and power connections, but I can tidy it up if anyone is truly interested.

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/ax3797_input_1.jpg
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/ax3797_input_2.jpg
http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/ax3797_input_3.jpg

http://i958.photobucket.com/albums/ae69/MeToo2_Prodigy/ax3798_output_amp.jpg


No guarantees and subject to change!

Thanks - saved for future reference. So much of this Calrec stuff is becoming impossible to find.

Jakob E.

I've updated the drawings on the first page. Confirmed that the ax3797 & ax3798 should work as a pair to make a 5 channel sub mixer with 70dB of input gain per channel and outputs of balanced L+R + balanced mono PFL out. It'd be simple enough to copy the balancing circuits to tap off each channel separately if that's what you want. I must say it looks like very complex (servo) feedback on the discrete balanced input amplifier. Certainly all high quality stuff.

Anyone any idea how phantom power / any input transformers would be attached on typical Calrec "PY" type input modules?

MeToo2 said:

I've updated the drawings on the first page. Confirmed that the ax3797 & ax3798 should work as a pair to make a 5 channel sub mixer with 70dB of input gain per channel and outputs of balanced L+R + balanced mono PFL out. It'd be simple enough to copy the balancing circuits to tap off each channel separately if that's what you want. I must say it looks like very complex (servo) feedback on the discrete balanced input amplifier. Certainly all high quality stuff.

Anyone any idea how phantom power / any input transformers would be attached on typical Calrec "PY" type input modules?

Click to expand...

No one know what was attached on typical Calrec "PY" type input modules?

I'll post a trace of the PY4012 module itself when I get around to it.
The physical PCB is marked PY3741, which was an earlier routing module so presumably there's a lot common with that.

But I have no definitive idea if any magic went on between the module and the patch bay.
It all looks electronically balanced to me but I'd like to know what was there on the original Q series.

What's the vintage of Q-series?

I'm trying to figure out who at Calrec did these from the circuit style.

MeToo2, you use certain schematic drawing conventions that IME are only found in Calrec stuff of a period.

ricardo said:

What's the vintage of Q-series?

I'm trying to figure out who at Calrec did these from the circuit style.

MeToo2, you use certain schematic drawing conventions that IME are only found in Calrec stuff of a period.

Click to expand...

Thanks. To be honest I don't particularly know. I only have individual cards. The AX3797 boards have a copyright date of 1995. The PY4012 don't seem to have a date on them although they are mainly surface mount discrete designs, with a limited number of through hole components, which probably dates them to mid 90's I suspect. Any schematic conventions and correspondence to official Calrec drawings are probably coincidental (these are my own drawings based on reverse engineering, and I studied electronics in the late 80's, so it probably dates me rather than the cards


Ahh just found manufacturing date codes on a Philips Semiconductors NE5532 of 1995 week 27 and a Motorola 4503 of 1996 week 7