Aries AR-323 Dual Mixer

Aries modules were available both as kits and factory modules.  This module sold in 1977 for $71.00 in kit form or $121.00 assembled.  This module appear to be a kit due to the non-uniformity of components and build and solder quality.

Aries AR-323 Documentation (compliments of Mark Glinsky)

This dual mixer features polarity switches for two of the four inputs and a sum out and difference out for the two mixers.

 

The design is a fairly simple circuit comprised of six dual LM301A op-amps.

 

 

 

This particular mixer had bleed issues between the A and B mixers. The jacks were not normalled to ground and the wires were all bundled together. The crosstalk between inputs would sum and result in about a 50 mV output signal from the other mixer. The bleed from A to B was a bit worse than B to A. You can also see about 12 mV of offset in the cyan trace.

 

I normalled all the input jacks to ground which improved the bleed. I also separated unbundled the wires which further reduced the bleed.

The bleed was more noticeable on inputs 1 & 2. These wires run to the rear edge connector and traces run in parallel across the PCB to wire to the attenuators. Since the edge connections were not used in the system I merely wired the input jacks directly to the attenuators. This reduced the bleed on these channels to near 0. The DC offset is clearly visible in this image.

 

The bleed on inputs 2&3 was now about 15 mV.  I thought there might still be capacitive coupling on the long parallel traces so I grounded the two now unused traces (black wire on the rear). That had minimal affect. That is when I noticed the normal connections on the jacks were not very reliable. Grounding these inputs reduced the noise to near 0. Since replacing the jacks required disassembling most of the module and the bleed level had been reduced 3.3X the owner decided this was sufficient.

 

 

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