Sansui BA-2000 Rebuild and Modification

The Sansui Ba-2000 is a power amplifier made to compliment the Ca-2000 preamplifier. The BA-2000 was rated a 110 watts per channel. Sansui also made 2 other power amplifiers at this time. the BA-3000 rated at 170 watts per channel and the BA-5000 rated at 300 watts per channel.

When I purchased this amp I had plans for it. I rebuilt the power supply using modern bridge rectifiers for the OPS supply and replacing all electrolytic and many transistors in both the driver supply and the ops supply.

Most importantly, on DIYAudio there is a very interesting thread titled “revisiting some “old” ideas from the 70’s”. a very good thread full of excellent amplifier designs. Built and tested with boards available. Well, one of the designs was an updated driver and ops for the BA-3000 using modern devices and a few mods mostly to achieve soft clipping. 

These specs, FFT and square wave test are from the virtualzero.com website.

Key specs with +/-65V rails:

  • Maximum output power: 200W @ 8 ohm
  • Voltage gain 29db
  • Input impedance 47 Kohm
  • THD: 1KHz – 0.0075%, 10KHz – 0.008%, 20KHz – 0.0085% (measured at 50W @ 8 ohm)
  • IMD: 14+15KHz – 0.007% (measured at 50W @ 8 ohm)

 

What I ended up with is a modern BA-3000 in a BA-2000 chassis. I couldn’t be happier with the amp. More information is available in the DIYAudio thread and the boards are available from https://www.vzaudio.com/

I had these boards made before they had their boards available. The vzaudio boards are nice and red.

I think it would be easier if you had a BA-3000 because the boards would fit. For the BA-2000 there are a couple ways to approach it. I lengthened the chassis by 2 “.

 

I used MakerBeam to bridge the new distance.  I was able to use the original holes so it was pretty straight forward and they worked well. Stiff and solid.

I cut up the old heat sink and mounted the fins in grooves on a piece of 3/8″ aluminum using thermal epoxy.

I was able to reuse the brackets for attaching the original heat sinks but as a spacer/hanger. The new heat sinks are now attached to the front divider panel and the back panel.

Here is the OPS mounted to the heat sinks. I was going to leave the inductor mounted on the existing protection board but I later put the inductor on the OPS board and used  different speaker protection and soft start circuit. I should have straightened the insulators for the picture but rest assured, they are straight now.

2 photos of how I covered the empty space left by lengthening the chassis 2″. I used a flat piece of aluminum across the front and a piece of ebonized oak as sides. The faceplate extended beyond the chassis cover so there was already room for the wood side panels.

 

The Power supply circuit board was corroded so I cleaned it and used an overcoat pen to cover the exposed traces.

These 2 photos are the before and after cleaning and overcoating.

The original SS-5R, SS-5151R diodes were replaced with 6A bridge rectifier diodes with heat sinks.