Nice 400-ll to rebuild

[wattsabundant]

Glen, nice work with that Zener diode addition. I don't see a downside (i.e. noisy diode switching or heat generation) and the rating of the 1N5366 diode is 5 Watts, .....Thanks, Mark

It's funny you mentioned switching noise. When I looked at the dwg. the first thought I had would be to hang a .1uf cap on the anode of the zener or the regulator output. No justification, but I'm always concerned about oscillations etc.

 

[grapplesaw]

It's funny you mentioned switching noise. When I looked at the dwg. the first thought I had would be to hang a .1uf cap on the anode of the zener or the regulator output. No justification, but I'm always concerned about oscillations etc.

Don there is a .1 uf cap right after the regulator along with a 220 uf audio grade electrolytic cap. There is no oscillations of any concern.

 

[mlucitt]

I spied another possible mod to the WOA Rev G1 Control Board. What capacitor are you using for C4L and C4R? They do not look like the Nichicon MUSE 470uF/25V capacitors that I have been using.

 

[grapplesaw]

I spied another possible mod to the WOA Rev G1 Control Board. What capacitor are you using for C4L and C4R? They do not look like the Nichicon MUSE 470uF/25V capacitors that I have been using.

Mark they are what came from Joe so not change on my side

 

[grapplesaw]

The only other item on the board is two .33 Panasonic metal film caps on the 12 and 11 pin in for both channels.

 

[mlucitt]

Mark they are what came from Joe so not change on my side

Glen,
I see now that it was probably just the light angle in the picture.


The .33uF Panasonic metal film caps on the 12 and 11 pin in for both channels is a good idea for an amplifier that does not have the WOA Backplane Boards installed. The PL400 Backplane Boards have 7.5uF of capacitance across the rails on each channel.
I see that you also have installed four of those 1.5uF Panasonic capacitors on the chassis for each channel. That is a lot of rail capacitance!

 

[grapplesaw]

So having been up to the lake house and repairing my boiler I set down to test this new amp

well had some issues with putting a ground wire on the wrong pin on the balanced to unbalanced board but that is sorted

first the soft start does what I wanted only 4-5 amps to start up
Wish I could post a video but that is a feat I have yet to master

also residual noise is good enough at .5mv on the balanced inputs, not sure how to short a balanced input so did not get that
The amp noise is less with inputs on the board shorted Noise is 320uv
The distortion is excellent and shown at 1-1/2watts output
And I am happy

 

[grapplesaw]

Was my mind in in the game today
Retested with a 8 ohm load
Thought distortion was way to low

floor noise improved withis load attached

I had to use the top AP to generate balanced output , because it’s a balanced setup machine and read the amp out put on the bottom AP