Akai GX-635D 1981-1984 - Silver/Wood sides

Akai GX-635D Reel-to-Reel Tape Deck – Extensively Refurbished, MRL-Calibrated – Includes dbx 150 Type II Noise Reduction

Asking Price: $3,200 – Reasonable Offers Considered

An exceptional opportunity to own a beautifully preserved and extensively refurbished Akai GX-635D, one of Akai's most respected automatic-reverse reel-to-reel tape recorders, accompanied by a dbx 150 Type II noise-reduction unit. This is not an ordinary, unserviced vintage tape deck. The GX-635D has undergone substantial electronic and mechanical restoration, including replacement of known failure-prone components, modernization of its forward/reverse switching system, precision calibration using MRL reference tapes, and extensive operational testing. The included dbx 150 Type II provides the option of high-performance encode/decode noise reduction for compatible recordings. Extensive Electronic and Mechanical Refurbishment Over 35 components were replaced during the restoration process.

Work performed includes:

- All 20 original 2SC458 transistors replaced. These transistors are notorious for developing excessive noise and reliability problems as they age.

- Forward/reverse switching system modernized. The original mechanical switching assembly developed contact problems that could not be corrected through conventional contact cleaning. It was replaced with a purpose-built, drop-in solid-state-controlled relay board incorporating high-quality Takamisawa silver-contact relays.

- New pinch roller installed to support proper tape handling and transport operation.

- Tape transport serviced and lubricated, with attention to the mechanical assemblies and operating mechanisms.

- Controls and switches thoroughly cleaned, including treatment of electrical contacts.

- Additional components replaced as necessary to address identified problems and restore reliable operation.

This was a targeted, technically informed refurbishment rather than an indiscriminate replacement of every original component. Large original electrolytic capacitors that tested satisfactorily were retained. The deck is not represented as fully recapped. I replaced known component failures and parts that were measuring poorly at the time of repair.

Professional MRL Calibration

The tape deck underwent electronic alignment using professional MRL (Magnetic Reference Laboratory) calibration tapes. Recording bias and recording adjustments were performed using ATR MDS-36 magnetic recording tape, and the deck was specifically biased for this tape.

Testing and calibration covered:

- Playback-level alignment.

- Record-level and bias adjustments.

- Frequency-response verification.

- Forward and reverse tape operation.

- Both 7½ IPS and 3¾ IPS speeds.

- Left and right channel performance.

Frequency Response

- At 7½ IPS: High-frequency response extending to approximately 21,000 Hz.

- At 3¾ IPS: High-frequency response extending to approximately 17,000 Hz.

These results reflect the actual measured performance of this machine under the test conditions, rather than simply reproducing the original manufacturer's specifications.

The GX-635D incorporates Akai's celebrated GX glass-and-crystal ferrite magnetic heads, designed for exceptional resistance to wear. The heads on this machine are in good condition.

Additional features include:

- Three-motor direct-drive transport.

- Automatic reverse recording and playback.

- ¼-inch, four-track stereo operation.

- 7½ and 3¾ IPS recording and playback speeds.

- Large-reel capability with original AKAI NAB adapters included.

- Independent recording and playback functions.

- Classic Akai analog VU metering.

Operational Testing

Following refurbishment and calibration, the machine completed approximately 12 hours of operational testing. Forward and reverse transport operation, recording, playback, and general functionality were checked. The machine is offered as a functioning, extensively serviced vintage audio component, with documented calibration results as shown in the listing photo gallery. Included: dbx 150 Type II Noise-Reduction System Also included is a dbx 150 Type II noise-reduction unit. The dbx system uses companding technology to compress the dynamic range during recording and expand it during playback, substantially reducing tape hiss when used with properly encoded recordings.

The dbx 150 Type II offers:

- Approximately 2:1 compression during recording and complementary 1:2 expansion during playback.

- Up to approximately 30 dB of noise reduction under appropriate operating conditions.

- Expanded effective recording dynamic range.

- Reduced audible tape hiss.

- Compatibility with appropriately encoded dbx Type II recordings. When correctly configured and calibrated, a GX-635D and dbx Type II system can provide a remarkably quiet analog recording and playback experience.

Important condition disclosure: The dbx 150 Type II has not undergone the electronic refurbishment performed on the Akai GX-635D. It is included in its existing vintage condition and is not represented as restored or recently calibrated.

Cosmetic Condition The GX-635D is in excellent overall cosmetic condition. Its original wood side panels are exceptionally well preserved for their age and have a beautiful factory appearance. The aluminum front panel presents very cleanly as well, with both sections showing only very minor cosmetic marks consistent with age and normal handling.

The machine retains its classic original Akai appearance, with no aftermarket cosmetic modifications.

Please review all photographs carefully for the exact condition of the equipment.

Included With Purchase

- Akai GX-635D reel-to-reel tape recorder.

- dbx 150 Type II noise-reduction unit.

- Original Akai NAB reel adapters.

- Metal take-up reel.

- Bag of replaced components included for reference.

Why This GX-635D Is Different

Many vintage reel-to-reel machines are offered with descriptions such as "powers on," "seems to work," or "recently serviced," with little documentation of the actual electronic work performed. We provide you with a bag of all the replaced parts so you can see what was changed! This GX-635D offers something more substantial: Extensive component-level refurbishment, replacement of all 20 original 2SC458 transistors, a modernized relay-based switching system, a new pinch roller, serviced transport mechanisms, and documented precision calibration using MRL reference tapes.

The inclusion of a dbx 150 Type II noise-reduction system adds additional versatility for the analog recording enthusiast.

For anyone seeking a classic, high-performance Akai reel-to-reel deck that has received serious technical attention, this is a particularly appealing example.

Asking Price: $3,200 – Reasonable Offers Considered.

Please contact us with any questions regarding the restoration, electronic measurements, included equipment, or shipping arrangements.

A Note About the Person Behind the Restoration I am not a conventional audio service technician. I am an electrical engineer with a Master of Science in Electrical Engineering (MSEE) from Northwestern University, and I design high-end audio equipment professionally. My work includes circuit design for established, mainstream high-end audio manufacturers, with several of my designs currently in commercial production. Confidentiality agreements prevent me from identifying the manufacturers or specific products. My background is in audio electronics engineering, circuit design, component selection, signal integrity, and performance optimization. I personally performed the electronic refurbishment, troubleshooting, and calibration of this Akai GX-635D, applying the same engineering principles and attention to detail that I bring to professional audio design.......

And yes, I can sling a soldering iron!

SHIPPING Your purchase will be packed and protected for shipment. It will be boxed with suitable cushioning and padding, as well as a shock indicator. We also arrange appropriate insurance coverage via Reverb SafeShip. Shipping charges are additional unless otherwise stated. See Reverb shipping costs at checkout.