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The Surround Sound Series

Just like many other brands (Teac, Sony and Dokorder come to mind) Akai produced a couple of 4 channel decks from the early until the mid '70's. The use of 4 seperate channels could make some sense:

1. A user could record and play 4 channels seperately, which means the recorder can be used as a "mini home-studio". You can record four different instruments for example by one person only. However, you will always need four speakers and a quad amplifier to reproduce the sound.

2. In the early 70's people thought there was something to add to plain stereo sound. Akai described the quadrophonical sound in their Dutch 1976 magazine like this: "Four channel sound reproduction is in a huge advance. It's a valueable improvement. In a concerthall the sound reaches you from all directions. This is because walls, ceiling and even the floor reflect the sound.

Research has proven that reflections 'coming from the back' determine the spatial impression of the sound-picture in an important way. You will notice that sound and the balance of the sound-picture are more realistic with quadraphonic sound reproduction".

It's very sour to learn Akai was about to quit the production of Surround Sound components about a year later.

Buying a Surround Sound reel to reel is not enough. You will also need a 4 channel amplifier tuner, turntable and/or receiver. Although this equipment has been produced, "Quad" sound reproduction never reached the big public. The reason for this may be that people just tossed their mono equipment in the late 60's and early 70's in favour of the just new stereo equipment, which was also very expensive then.

It would be much too expensive too change all the stereo equipment for quad equipment again just a few years later. I think people were also very impressed by the new late 60's stereo sound and they didn't feel the need to go another step higher.

Akai produced some quad receivers, a couple of quad reel to reels and some decoding-equipment to "translate" 2 channel stereo sound into 4 channel quad sound. This decoder was based upon the Matrix system. Other known systems to translate 2 channel into 4 channel were CD-4 and SQ.

In the early 90's surround sound re-entered the audio world. Lots of today's receivers have some sort of Dolby surround system. In fact this "new" surround sound is based upon plain stereo 2 channel sound which is translated into 4 channel sound by some built-in decoder.

The earlier Akai Surround Sound reel to reels were most likely mainly intended to listen to 4- channel prerecorded tapes or make recordings from 4-channel LP's, because the ability to switch the 4-channels seperately were not present. The later and more expensive models had the so called "Quadra-sync" system, which enabled the user to switch all 4 channels seperately.

The problem with the simpler models is you could never synchronize a later recording.

In fact, there's always a time delay, caused by the distance between the recording and playback head and depending on the tape speed.

The introduction of the Quadra Sync system, made this problem a thing of the past. By means of a rewiring switch, the recording head was used as a playback head so the user could listen to one or more earlier recordings and synchronize another one.

The GX-270D-SS, GX-400D-SS, and GX-630D-SS all had the Quadra-Sync system; basically the ability to play one channel in sync with ther recording of another channel by using the Record Head Gap for Playback which would be physiocally in line with the newly recorded material on the "other" track.

These early to mid 70's sets used some plug-in boards, which years later could translate into broken PC Board Edge Connectors, where a drop or fall causes the chassis mounted edge connectors to split in half.

There is a huge harness of wires inter-connecting these edge connectors, making for an almost impossible to repair situation, and most of these edge connectors are no longer made. The GX-400D-ss and GX-630D-ss also use the failure prone LD3141 IC's both these items can cause difficult to fix failures.

Because of their rarity properly working Surround Sound sets have a relatively high value in the second hand market.


The 202D-SS (1975-1976)

The 202D-SS is derived from the GX-210D; the mechanics are just the same. This set has two speeds, three motors and 4 heads: a full track erase head, a 4-track 2-channel erase head, a 4- track 4-channel recording head and a 4- track 4-channel playback head.

It speaks for itself that the full track erase head erases all 4 channels at one time.

This deck like any other Akai Surround Sound set, could be used as a 4-track 4-channel set but also as a 4-track 2-channel set. A switch on the front is used to switch between 4 and 2 channel use.

Because of the 4-channel playback head, a solenoid which pulls down the playback during reverse had become redundant.

The 202D-SS also has the auto-reverse feature which can be used in 2 channel mode only. It also has a tape selector and four line-in knobs with one VU meter each. There are also four microphone inputs and a double headphones output.


202D-ss Specifications

Track system: 4-track, 4-channel/2-channel compatible stereo system

Tape speed: 3.75 ips and 7.5 ips

Total Wow and Flutter: Less than 0.08% @ 7.5 ips

Frequency response: 30 to 25,000 Hz +/- 3 dB @ 7.5 ips

40 to 15,000 Hz +/- 3 dB @ 3.75 ips

S/N ratio: Better than 50 dB

FFWD/RWD time:

Main motor: 2-speed servo control outer rotor motor, model SCM2-24

Reel motors: Eddy current outer rotor motor; model: XO24-MR

Heads

Erase Head:

Recording head:

Playback head:

Dimensions: 442 (H) x 391 (W) x 231 (D) mm.

Weight: 18.0 kg.

Power consumption:

Listed new:


The 280D-SS (ca. 1973-1974); the GX-280D-SS (1974-1976); and the GX-297D-SS (ca. 1976)

These 4-head, 3-motor models are about 99% alike and can be regarded as the predecessors of the GX-270D-SS. They are relay controlled and can do a single auto-reverse cycles during playback in 4 track, 2-channel mode only.

In 4-channel mode the user has the ability to use auto-repeat, which means the machine goes into REW mode at the end of the tape as soon as a piece of sensing foil reaches the reverse sensing post. At the beginning of the tape when the other sensing foil reaches the second sensing post again the machine stops and goes into playback mode again. When auto-reverse and auto-repeat aren't used there's also an auto shut off function which cuts down the power.

Just like the 2-channel models GX-280/D and GX-285D, the servo control takes places with an external "head" which is mounted on the capstan motor. This head "checks" the motor revolutions. The 280D-SS does not have the GX heads. The solenoid which pulls down the playback head a little when the deck switches to reverse mode is not present in these sets since they already have a 4-channel playback head.

The differences between the GX-280D-SS and the GX-297D-SS are just internal. Except for the headcover they are 100% identical externally. The GX-280D-SS has the fourth edition of the KD-1001A system control board, the GX-297D-SS has the fifth edition. The GX-280D-SS uses the E4-200 and E4-250 erase heads, the GX-297D-SS uses the E4-210 and the E4-260 erase heads.


GX-280D-ss Specifications

Track system: 4-track, 4-channel/2-channel compatible stereo system

Tape speed: 3.75 ips and 7.5 ips

Total Wow and Flutter: Less than 0.10% @ 7.5 ips

Frequency response: 30 to 24,000 Hz +/- 3 dB @ 7.5 ips (LN tape)

30 to 15,000 Hz +/- 3 dB @ 3.75 ips

S/N ratio: Better than 55 dB

FFWD/RWD time: 68 sec. (83 sec.) using a 1200 ft tape @ 60 Hz (50 Hz)

Main motor: 2-speed servo control outer rotor motor, model SCM2-24

Reel motors: Eddy current outer rotor motor; model: 24XO-MR

Heads

Erase Head: Full track erase head: type E4-200 and 4-track erase head: type E4-250

Recording head: type R4-280

Playback head: type P4-280

Dimensions: 505 (H) x 435 (W) x 250 (D) mm.

Weight: 22.4 kg.

Power consumption: 140W.

Listed new: $ 1250.00 for GX-280 D-SS in 1973


The GX-270D-SS (ca. 1976) and the GX-630D-SS (ca. 1976)

The GX-270D-SS and the GX-630D-SS were Akai's last Quad sets. The GX-270D-SS is derived from the GX-270D and has the auto-reverse capability in 4-track 2-channel mode only. Both sets have the Quadra Sync feature which means they could be used as a mini home- studio to a certain extent. Each channel can be switched seperately. They have a switch for either 4 channel or 2 channel use.

Since the GX-270D-SS has four heads, there's no fifth head for reverse play. The playback head is a four channel example and is used for both forward and reverse play in 2 channel mode. The other heads are: a full track erase head, a 4-track 2-channel erase head, and a 4- track 4-channel recording head. To adapt an earlier recorded tone pitch, the GX-270D-SS and the GX-630D-SS were supplied with a 5% pitch control function.

The more common 2- channel models (GX-270D and GX-630D/DB/D-PRO) didn't have that feature.

There are four microphone inputs and two headphone outputs available. The functions found on the GX-270D-SS are almost identical to those on the GX-630D-SS. Latter lacks the auto-reverse feature but can handle reels up to 10.5".


GX-630D-ss Specifications

Track system: 4-track, 4-channel/2-channel compatible stereo system

Tape speed: 3.75 ips and 7.5 ips

Total Wow and Flutter: Less than 0.05% @ 7.5 ips

Frequency response: 30 to 23,000 Hz +/- 3 dB @ 7.5 ips

30 to 16,500 Hz +/- 3 dB @ 3.75 ips

S/N ratio: Better than 55 dB

FFWD/RWD time:

Main motor: SCM-2-24KJ

Reel motors: Eddy current outer rotor motor; model: 24XO-TD

Heads

Erase Head: E4-260

Recording head: R4-285

Playback head: P4-280

Dimensions: 530 (H) x 440 (W) x 265 (D) mm.

Weight: 20.7 kg.

Power consumption: 90W.

Listed new: $


The GX-400D-ss (1975)

This massive giant of a set has about the same functions as the GX-630D-ss; but then there is even more. The GX-400D-ss is derived from the GX-400D and the GX-400D-PRO.

The upper front panel including the part which houses the tape control function knobs are like the ones from the 2-channel models. The lower part of the front contains all ther audio section electronics, and has a different construction, which also tells us this deck is a little newer than the 2-channel models. The knobs for input and output level are like the ones found on the GX-286 models.

The GX-400D-ss has the quadra sync system so each channel can be recorded seperately though synchronously with earlier recorded channel(s).

Just like the GX-280D-ss and similar models, the GX-400D-SS has an auto-reverse capability in 2-channel mode and an auto-repeat function in 4-channel mode.

There a three tape-speeds: 3.75 ips, 7.5 ips and the more professional 15 ips., a shut off capability, a tape cueing function and a tape selector to switch between normal and low noise tapes.


GX-400D-ss Specifications

Track system: 4-track, 4 channel stereo system and 2-track, 2 channel stereo system

Tape speed: 3.75 ips, 7.5 ips, and 15 ips.

Total Wow and Flutter: Less than 0.035% @ 15 ips

Frequency response: 20 to 27,000 Hz +/- 3 dB @ 15.0 ips Using SRT Tape

20 to 26,000 Hz +/- 3 dB @ 7.5 ips

30 to 17,000 Hz +/- 3 dB @ 3.75 ips

S/N ratio: Better than 55 dB @ +3 dB

FFWD/RWD time:

Main motor: SCM3-16TW 4 Pole eddy current AC servo motor

Reel motors: IMI-24TW 6 Pole eddy current inner rotor motor

Heads

Erase Head:

Recording head: R4-285

Playback head: P4-280

Dimensions: 590 (H) x 457 (W) x 240 (D) mm.

Weight: 31.2 kg.

Power consumption: 160 Watts

Listed new: $1495.usd


This page is under construction ( Like software, the job is never done!....)
Last Update - 6-22-05 7:30 PM.



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