As reported by engineer Phil York in a communique with David Bullock:

"Sound City had Ampex recorders; a 4-track, 2-track, and full track,
plus an Ampex 1/2" THREE track deck as well. We would sometimes fill
up the 4-track, mix them down to one track of the 3-track, place that
tape over on the 4 track machine and add 3 more. The hiss build-up
was formidable.
The mixing board was an Altec Lansing 8-channel vacuum tube radio
broadcast board, converted to do recording. It was indeed very green,
with large 3" diameter rotary knobs; 8 channels plus one master knob,
total of 9. Two big VU meters, L&R. There were two small outboard
equalizers in the wall-rack to the right which had to be patched in.
There was ONE limiter with almost no adjustments on it. It was either
an Altec-Lansing or a Gates brand, I forget which. The plate reverb
was a German EMT and a nice sounding one, too.  To the left of the
mixer was a small stand with a 3-speed turntable on it. One of the
1/4" tape machines was there also. The disc cutter to the back left
was a Presto 8-N, I believe,  with two speeds and a metal converter
device which would make the 33.3 rpm setting run at 45 rpm.
There was one very odd piece of equipment. It was a graphic
equalizer, a Blonder-Buss, I think. Each frequency, about 6 or 8 of
them, had a verticle slot through which shone a revolving cylinder.
When you turned the rotating disc at the top of each band to change
the frequency, a peppermint-looking mechanical disply would move up
or down.... not unlike the speedometer in the infamous 1959 Buick.
There was a VERY OLD Hammond organ, pre-B3,  probably a B-1 or B-2,
in the studio, which more or less was suitable for funerals. And
there were only about 6 or 7 mikes. The most prominent were a big
Neumann U-47, quite a vintage collector's item today, and an RCA
DX-77 pill-shaped ribbon mike. There was also an Electro-Voice 667
dynamic mike and one Altec 639-A ribbon/dynamic."