B. MDX1200 modding

[mhelin]

I opened my MDX1200 Autocom (collecting dust as usual) to see if it's worth replacing any components there (besides the opamps). The VCA's seem to be uPC1252 type (http://www.datasheets.org.uk/preview/3538911.html ), and the pinout seems to be compatible with THAT218x, also the CV vs. gain graphs are quite similar in mV/dB (-5.9 of 1252 vs. -6.1 of THAT in pin 3). THAT seems to be about 4 dB less noisier (at Av = 0 dB , -98 dB vs. -94 dBV noise level). Worth swapping? I think the pins can be cut and the sockets soldered to remains of the pins so that the PCB has not to be removed from the box.

Some related threads:
DBX160X modding:
http://www.groupdiy.com/index.php?topic=9960&highlight=&sid=bf9520edf3a381e1ec4ccda2f01a06a7

GSSL VCA comparisons:
http://www.groupdiy.com/index.php?topic=10420&highlight=1252

 

[walter]

I have been asked to modify an MDX1000. I have an MDX1400, and an MDX1600. The 1600 does not have the transformer space on the back pcb, it does have a Unity, and a THD trim pot for both channels, THAT 2159 IC's. The 1400 has the spaces for output transformers, a THD trim pot for each channel, THAT2159 IC's. Looks like 4580 op-amps on the back, and 917317 (14 pin) on the front pcb. An op-amp swap, and filter cap upgrade could be a good start. Those are some interesting links, I have some reading to do. As mentioned in one of the links, a Jensen 123-slpc transformer fits in there, although there is room for any transformer just connect with jumpers. I won't bother to do anything without removing the pcb's, gotta get a good whack at it, and worth the extra trouble of disassembly imo. Another way to remove those suckers is: Flood all the pins with hot solder, and (gently) yank the sip out. I gotta get a desoldering station. How is the project going Mhelin?

 

[clintrubber]

Any opinions on the unmodded MDX1000, 1200, 1400... ?

I got me a '1200 for an easy lazy case for the Fred F. opto-comps, but didn't have a listen to the original inhabitant yet.

What's the feeling, significant improvements expected for modded Autocoms ?

Regards,

Peter

 

[Snatchman]

I have the MDX-1000. This is from Behringer's early 90's gear. All thru hole technology, no SMT..Has the place on the pcb for the transformer. It's heavy and well built..Not like the light weighted stuff they build today.. :roll: .. I bought this new ( early 90's) and it's worked every since. Still working right now!.. :shock: ..It sounds decent, but I'm sure it would benefit from mods. Uncluttered looking PCB..SOT..I have a 5 band parametric designed the same way for sell, if anyones interested...Thanks