akai

AKAI VX600 MATRIX SYNTHESIZER

The VX600 is a quite rare analogue synthesizer made by AKAI in 1988. The VX600 has 6 voices, each containing two oscillators with square/pulse, saw and triangle waves plus white noise on VCO2. Real voltage controlled oscillators, mean a tune is required to keep them in sync. It was marketed at players of the EW1000 series wind instruments.Each voice can be assigned to a different MIDI channel for multi timbre operation.The GLIDE, BREATH and VIBRATE controls seem to be redundant if not using the EW controller. BEND works though. Add the following to the MOD matrix to control filter cutoff.

  • (EW.BEND) (+50) (CUTOFF)

The filters consist of 6 low-pass resonant (up to self-oscillation), keyboard tracking VCF's and 6 high-pass filters (no resonance this time). the low-pass filter can also be modulated by VCO2. The VX609 uses Curtis chips 3372 (VCF) and 3374 (VCO).

two LFO's (with delay) both LFO1 and LFO2 have a range of waveforms: triangle, positive sawtooth, meg sawtooth plus square wave. It has three ADSR envelopes. or ADDSRs , every envelope has two decay settings. the EG's can also be delayed. The LFO can be a bit slow for some, so add this line (even multiple times) to the MOD matrix controllers to add more speed

  • (KEY GATE) (+99) (LFO-1 SPEED)

I purchased this in later 2017 from eBay. It cost a small fortune. I saw the superb Jexus videos on YouTube and when one came up for sale I just went for it. It's a US version with 120vAC. Overall it was in good condition. Display is 40x8 LCD. The back light had been replaced, although it still seem washed out and faded. The inverter also makes a high tension whine.

display

card

It takes about 15 minutes for the synth to stablilise before doing a VCO tuning calibration. I looked at this on a DVM and ound the voltage sits at .22v then rises up to 2.5v over a period of 9 minutes. Why this is is unclear, bad capacitor perhaps? I have found that if the auto calibration doesn't complete, or takes an eternity you my need to check the DAC voltage. It should be 2.5v DC. Procedure is in the service manual. If your VX600 sounds bad this is possibly the reason.

Some pictures of the insides:

Inverter

inverter

 

Battery/CPU/ROM

processor

 

Voice Cards x6 voices play from bottom to top, when first powered on

voices

 

Below voice cards. Opamps and multiplexers

vb

 

Power Supply

psu

 

There was some UV damage to the side panels. I'm not a fan of nicotine yellow so I must try and restore these.

uv

The synth can have 6 separate outputs. I believe back in the day the VW-X6 DIN/PHONO cable was available. It possible to make your own using a 13 pin cable similar to those found on old Atari ST monitors, Digikey part number CP-1013-ND. The pinout for the VOICE OUT connector is shown below.

sep