GML Model 8300
A two-channel mic preamp that turned up to a magazine shootout in a borrowed rack because the factory had none to spare.
Overview
The GML Model 8300 is a two-channel, transformerless microphone preamplifier in a single rack space. That much is settled. The surviving documentation does not say when it was made, what it cost, or how many were built. The record is thin, and this page says so rather than filling the gap.
What does survive is a substantial hands-on evaluation published by Recording Engineer in the fall of 1987. The 8300 was one of eight stand-alone mic preamps pulled together for technical measurement and listening tests. That review is the backbone of everything below. It is the primary witness, because there is very little else.
The format is simple: two channels in 1U, external power supply, XLR in and out. The review's comparison table lists a polarity switch, phantom power, a stepped gain control, and a peak LED. That is a fuller front panel than several of the units it was tested against, some of which shipped without phantom or without any peak indication at all. Stepped gain instead of a continuously variable pot divides engineers. One side gets repeatability and channel matching, the other gets fine trim. The 8300 went with steps.
Two channels is the whole point of a box like this. The Recording Engineer piece (September 1987, p.60) opens by noting that the growing taste for stereo-pair recording - spaced omnis, MS arrays, coincident pairs - had created demand for a clean, short signal path. A matched pair of low-noise preamps suited that work better than threading a signal through a large console's bus and EQ stages. The 8300 is aimed squarely at that user.
Component matching is where it separated itself from the field. In the common-mode rejection measurements, Recording Engineer (September 1987, p.67) reported that only three of the eight preamps showed real evidence of matched components in assembly. The evidence was how closely the two channels' CMRR curves tracked each other. Those three were the Jensen Twin Servo 990, the Summit Audio TPA2, and the GML Model 8300. The magazine's authors were blunt about the rest of the field, arguing that anyone buying a stereo preamp should expect both channels to sound the same, particularly for stereo-pair work. The 8300 was built as a matched pair, not as two channels that happened to share a chassis.
Phase behavior was the other strong showing. In the low-end phase measurements, the 8300 landed in the second-best group, alongside the Sontec MB-1A and the Studio Technologies Mic Pre Eminence. All three showed less than four degrees of low-end shift. Only the Jensen Twin Servo 990 did better, with no measurable low-end non-linearity at all. For comparison, the Summit Audio TPA2 and the HART MP-501 card showed roughly seven degrees of shift, the Innovative Audio UTMP-2 about ten, and the Benchmark 4x4 about thirteen. The review treats low-end phase deviation as a real audible concern.
One operating note from the same review: the 8300 responds best with the output gain at maximum and level adjusted with the input gain alone. Treating the two controls as interchangeable means not hearing what the preamp can do.
The test also says something about the unit's provenance. Recording Engineer (September 1987, p.60) states plainly that the 8300 was not supplied by the manufacturer like the other production units. It came from a local owner, because GML apparently had no stock on hand at the time of the evaluation. The editors also noted that no photographs of the 8300 were available for the article, and the same went for the HART MP-501.
The listening-test results were published separately, in the October 1987 issue. The available material from that installment is fragmentary. A partial scoring table survives, but not enough of the 8300's specific ranking to report. The technical half of the review is where the documented record is strongest.
Anyone chasing an 8300 today should expect to be chasing. The absence of a loaner unit in 1987, the missing product photography, and the sparse paper trail all point the same direction: this was not a high-volume product, and it does not turn up often. Anyone who finds one should check that the external supply is included, since the review's comparison table lists the 8300's power supply as external. A missing supply on a low-production preamp is a genuine problem. Beyond that, pricing history, common failure points, and service documentation for this model are not established in the sources available here. Treat any listing that claims otherwise with suspicion.
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