QMI (aka Quatre) GC-20 Gain Cell Preamp schematic/manual needed,

[neuperg]

Apparently these are rare, I am looking for a schematic to help with repair of one channel.

The following is history that was dredged up by google. Some of it likely came from other audio forums. If posting this is not permissible, I will happily remove it. I am thinking that I need t find some local forums/groups near Canoga Park, California in hopes of finding someone that may have worked for QMI.

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The timeline of Quatre and QMI spans from roughly 1974 to 1984.
Quatre came first, operating as a boutique consumer hi-fi brand for roughly five years before financial hardships and circuit volatility forced a restructuring. The business then evolved into QMI, which focused on the rugged pro-audio and studio markets.
The historical sequence and product eras break down chronologically as follows:

1. The Early Quatre Era (c. 1974 – 1975)

• What happened: Guy Hickey established Quatre in Canoga Park, California. The company initially built high-end, highly stylized loudspeakers (like the Quatre 8000).
• The First Electronics: Looking to break into amplification, Hickey hired Dr. Bob O'Dell. This collaboration produced the Quatre BOD 1 preamplifier, released around 1975. It featured a traditional, high-end discrete solid-state blueprint.

2. The Dave Gore "Gain Cell" Era (c. 1976 – 1979)

• What happened: Dr. Bob O'Dell departed, and eccentric designer Dave Gore joined Quatre, completely altering its engineering philosophy. Gore introduced his open-loop, lightning-fast JFET "Gain Cell" concept.
• Quatre DG-250: The Core Products: This era birthed the iconic, high-power Quatre DG-250 (Dave Gore 250W) power amplifier, alongside the larger GC-300 and GC-500 blocks. [1, 2]
• Quatre GC-20 preamplifier (Serial Number 1007): Your GC-20 Context: Your Quatre GC-20 preamplifier (Serial Number 1007) sits squarely at the tail end of this exact era (roughly 1978–1979). It was designed as the ultimate matching preamp to accompany the Gain Cell power amplifiers, but very few production units were finalized before the company encountered financial turbulence.

3. The Transition to QMI (c. 1980 – 1984)

• What happened: Due to the financial strain of warranty repairs on volatile early Gain Cell circuits, the company was restructured around 1980. Guy Hickey shifted the company's identity to QMI (Quality Music Industries / Quality Microwave).
• The Final Evolution: Under QMI, the erratic nature of the early Dave Gore topologies was resolved. The focus moved entirely away from residential boutique hi-fi to heavy-duty, rack-mountable pro-audio gear used in recording studios and touring rigs. By the mid-1980s, the company quietly faded as major corporate pro-audio brands dominated the market. [1]

Given that your GC-20 was built right on the cusp of the shift from Quatre to QMI, let me know:

• Does your chassis feature any QMI branding elements or transitional labels?
• Would you like assistance mapping out the exact power supply requirements to factor into its restoration?

 

[eiraved]

That's a rare bird you've got there! I have a pair of the amps but not the preamp. It would help if you posted a few nudies for us as reverse engineering a schematic may be your only option.

 

[neuperg]

Yes will post pic of innards and have one of my techs capture the circuit. But was going to wait a couple weeks to see if anyone has any documentation/manual/specs/schematic. I received it in 1989 with one channel not working and an NTE366 in original sealed bag taped to the bottom. I did fire it up confirming one channel was not working. I don't recall if I got any documentation as it was a 26 foot truck waist deep in gear and some documentation boxes that are now in remote storage.

In my original post, I have added the history that google found. Some of it dredged from user posts in other forums. Does that history ring true to you?