Studiomaster Diamond Pro 12-3 1990s - Grey / Black

Early 1990s Studiomaster Diamond Pro 12-3, manufactured in the UK. This is the original version — not the later Pro-3 or overseas models. If you know, you know.

Features:

• 12 mono input channels, each with:

– XLR mic input

– 1/4” line input

– Insert jack

– Fixed 3-band EQ (±15 dB at 12 kHz, 2.5 kHz, 80 Hz)

– 4 aux sends (2 pre-fader, 2 post-fader)

– Pan, PFL, Group 1–2 assign, L/R mix assign

– 100 mm long-throw fader

Master Section:

• Balanced XLR L/R main outputs

• Mono output (1/4”)

• Group 1/2 outputs (1/4”)

• 2 stereo aux returns with routing to mix or groups

• Stereo RCA 2-track input and output

• 12-segment LED meters

• Headphone output with monitor source selection

• Global +48V phantom power

• Internal linear power supply

Sound & Design:

• Analog British console tone

• Broad, musical EQ — no sweep

• Ideal for synths, drum buses, summing, or tracking

• No onboard effects or digital control

Build & Serviceability:

• Modular channel construction (1 PCB per channel)

• All ICs socketed — upgrades and repairs require no soldering

• Through-hole components

• Steel chassis

• No surface-mount parts

Condition:

• All channels tested and pass audio

• Meters and LEDs functioning

• No broken jacks or missing knobs

• Cosmetic wear consistent with age

• Power supply stable

• No mods or internal changes

• All original capacitors; unit is unserviced. As with all vintage gear, electrolytic capacitors will require replacement at some point.

Additional Notes:

Item tested and passes audio. Given its a vintage mixer, it is not guaranteed or warrantied in any way and is sold as-is.

Video is of my 16-3 but internally the same minus 4 channels

Optional Services Available After Purchase:

• Full cleaning (pots, faders, switches, jacks)

• Power supply capacitor replacement

• Signal path capacitor upgrade

• Full electrolytic recap

• Op-amp upgrades