JBL Synthesis S-650
A five-channel THX amp whose spec sheet reads like a Bryston - because, owners say, that's what it is.
Overview
The JBL Synthesis S-650 keeps showing up next to the words "rebadged Bryston." Audio Asylum Trader listings for the S650A variant state it outright - "rebadged bryston 9b sst" - and that one claim explains most of how the amp is regarded today. JBL's own materials describe the S650 as a "reference-grade 5-channel power amplifier designed for high-end residential home theaters," and hifi4sale.forumotion.com labels it a "THX 5 Channel Power Amplifier." The THX tag is the reason the amp exists. It was built to drive the dynamic peaks of a multichannel film soundtrack across five channels at once without sagging. The unit was made in the USA, according to hifi4sale.forumotion.com.
The model name wanders. Documentation and listings show "JBL Synthesis S-650," "JBL SYNTHESIS S650," "JBL Synthesis S650," and "Jbl Synthesis S650A." The last one is on the Audio Asylum Trader listing that names the Bryston connection. Whether the "A" suffix marks a revision, a regional variant, or a seller's shorthand isn't documented in the available material. Treat the S650 and S650A as closely related until someone produces paperwork that says otherwise.
There's also an identity snag. At least one source, hifi.fan, describes a "Synthesis S-650" as a high-performance subwoofer with a 12-inch driver. That doesn't match the amplifier that dominates every other reference to this model number, and the fact sheet carries it as a conflict rather than a settled fact. Given the weight of evidence for a five-channel power amp, the subwoofer description looks like a misattribution. Anyone hunting an S-650 should confirm what they're buying before money changes hands.
Key Features
130W RMS Per Channel Into 8 Ohms
The key number is 130 - as in 130W RMS per channel into 8 ohms, with THD specified at under 0.03 percent. That figure appears in both a forum post on Audioholics and a Carousell listing, which is more corroboration than most specs for this model get. It reads as a conservative, real-world rating rather than a marketing peak. Five channels at 130 watts each is enough to drive a full surround array of moderately demanding speakers. The 0.03 percent THD ceiling is a low figure for a multichannel amp of this type. Some sources also quote the amp as "650 watts 5 channel," which is best read as the aggregate rather than a per-channel claim. 130 times five lands right at 650.
THX Certification
The S-650 carries THX certification, per hifi4sale.forumotion.com. For a five-channel amp meant for a high-end residential theater, that certification signaled the amp could meet THX's requirements for headroom, low distortion, and stability under the sustained, dynamic demands of film playback. It also shows what the amp was built for: not two-channel listening, but a full surround rig where the center and surround channels need the same authority as the mains.
38 kg of Power Supply
At 38 kg, the S-650 is heavy. Most of that mass is the power supply - the transformer and reservoir capacitance needed to feed five channels of Class-AB output without voltage sag on transients. It's a two-person lift onto a rack shelf, and the shelf had better be rated for it. Collectors note that weight in this class is usually a reliable proxy for build quality.
The Bryston Connection
The most repeated claim about the S-650 is that it is a rebadged Bryston 9B SST, stated directly in an Audio Asylum Trader listing for the S650A. If true, it explains the amp's reputation among owners. The Bryston 9B is a five-channel amplifier with a long service life and a devoted following, and an amp built to that standard under a JBL badge would carry the same virtues: sturdy output stages, generous power reserves, and a design that tolerates decades of use. The claim is repeated by sellers rather than confirmed by manufacturer documentation, so treat it as an owner-reported attribution rather than a settled fact.
Collectibility & Value
The S-650 trades on the secondary market at prices that reflect its pro-adjacent build rather than any collector cachet. An Audio Asylum Trader listing for the S650A 5 Channel Amp carried a price of $1,100.00 and was marked SOLD. A separate listing on hifi4sale.forumotion.com priced a JBL Synthesis S650 THX 5 Channel Power Amplifier at RM4,380 and was likewise marked Sold Out. Both are asking prices on completed sales rather than confirmed transaction values, and they are the only data points available, so treat them as a rough band rather than a firm market. They suggest an amp that sells for a fraction of what a comparable Bryston-badged five-channel unit might fetch.
Owners talk about the amp in practical terms. One Audioholics forum poster simply states, "I do have a JBL Synthesis s650 power amp." An Audio Asylum Trader seller describes moving on from an S650A after upgrading: "I am selling my JBL Synthesis S650A 5 Channel Amp that I used to run my center and surrounds from. I have upgraded to 2 Citation 7.1's to run these speakers." That's the pattern - the S-650 gets replaced when an owner steps up to separates, not because it failed. A service manual exists, running seven pages, and a downloadable PDF is available through the usual manual repositories. No specific faults, parts-availability notes, or repair procedures are described in any source, so prospective buyers should budget for a technician's inspection rather than assume a known failure mode.
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