The old Pioneer CL-99A's I just got.

I would imagine it's designed to handle two sets of 8 ohm speakers, since that's the most likely load that would've been placed upon it. On the other hand, it's hard to imagine that many folks had the gumption to set up two independent quad speaker systems, even if they had the wherewithal (which, given the price of that receiver, they likely would have!).

The Monitor 10 (at least the early models thereof) is a nominal 6 ohm load, so exercise a little caution if you were to go that route as part of your dual quad system.

Couple of comments:

This receiver has (I presume) four identical power output amplifiers, but one power supply. That said, the per channel power rating is (at least by modern standards) modest, and a photo of the guts of one suggests (to me) that it probably has a semi-split P/S (i.e., dual transformer secondaries, most likely for "front" and "rear") similar to, e.g., the Kenwood KA-7100 stereo amp of a couple of years later.


source: https://classicreceivers.com/pioneer-qx-949


Adding two more speakers (i.e., going from stereo to quad), all else being equal, would result in 3 dB more SPL at the listening position. Of course, for 'true' four-channel program material, the output from the rear channels would be (much) lower than the front ones, so the actual volume increase with four speakers wouldn't be that much. If, however one fed the same stereo signal to front and rear channels, you would, at least on paper, get 3 dB more output.

It's OCL = output capacitor-less. The power supplies still use capacitors as filters and storage reservoirs.

Here's what "OCL" means: In the early days of soiled solid state, limited availability of reliable, affordable (NPN/PNP) pairs of transistors for "fully complementary" output led to the use of a 'quasi-complementary' output scheme. In that case, there was, essentially, a biasing DC voltage that rode under the music signal all the way through the output stage. That DC HAD to be removed, else it would cook the loudspeakers' voice coils. Rather than use transformers (which are expensive, especially wide bandwidth output transformers with good power handling capacity), the hifi manufacturers used blocking capacitors between the output transistors and the speaker connections on the back panel of the amp or receiver. These capacitors were large value and moderately high voltage but cheap compared to transformers. They had the interesting effect of rounding off the sound of the earlier capacitor coupled amps that some folks (at least nowadays!) will describe as tube-like. <don't get me started...>

Eventually, the industry moved towards fully complementary "push-pull" circuits that allowed the output transistors to operate around a midpoint of zero DC volts. This amplifier topology requires no output capacitor -- hence OCL.

When there entire amplifier signal chain is complementary and there are no blocking/coupling capacitors or transformers anywhere from the input to the output, the brochures would usually refer to the amp or receiver as Direct Coupled (DC).

Aren't you sorry you asked?!

Now, all this being said, IF anything goes wrong, the amplifier can gleefully cook one's
loudspeakers with the DC "rail" voltage that powers the outputs! This is one of the reasons why it is ESSENTIAL to have fast acting and reliable protection circuitry on an OCL or DC solid state amp. If a transistor fails (shorts), the usual result is instantaneous destruction of at least one speaker

I used a teeny bit of De-Oxit on a Q-tip to clean off the terminals on the back. Did the job perfectly, they look new!
Also worked on a similarly aged Lafayette that I had, although not quite the same success. Still a thousand times better though.

Good lord man they are clean already !!! Lol, the insides of the jacks can be cleaned by using a Q-tips™ I cut the cotton completely off mine though and use only the paper stick part and Deoxit™ (D5) . By removing the cotton on the ends I do not get cotton trapped in there and the paper is a bit more abrasive than the cotton anyway. Paper is what many (including me) use for cleaning the occasional relay contact..

https://youtu.be/YQfzrBcjoBs

Clean gold or silver with those gold or silver cleaning cloths sold at the jewelry counters at you local discount store. they work GREAT !!!

Regular Deoxit is a more powerful cleaner than the pro gold stuff. the Pro Gold is actually made to be put on after you clean with Deoxit. I only use the 100% Deoxit and Pro gold the D5 stuff is only a 5% solution of the actual chemical.