I built Grey Rollins' version of the amp and now I get 13.3V common mode oscillation of about 500Hz. Anyone familiar with this problem? I havent had any time to investigate further. I will statr with powersupply decoupling first, as I don't have a clue where else this type of problem could originate.
Thanks
Thanks
Re: Solved
For your info. I often fix the bridge diodes on the main heatsinks.
In this case, we need to be generous with somewhat lengthy wire arrangement.
DACMan1 said:Now the only problem is heatsinking for the diodes on the powersupply which is inadequate but there is not enough space for bigger heatsinking
For your info. I often fix the bridge diodes on the main heatsinks.
In this case, we need to be generous with somewhat lengthy wire arrangement.
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That won't work with my layout and the fact that I am using 4 BYV diodes. Also, I want to minimse the wires to and from the diodes, as they carry large current spikes to top-up the reservoir caps. I have other heatsinks that are suitable, just don't know how much better they will be. I will look into it tomorrow.
Ones I have is 15.5degC/W which means a temp rise of 52degC but its the best that will fit. However, forward voltage drop on these will only be less than 1V(worst case 1.15V and will drop at higher temperatures. Thus:
2.25*1=2.25W
2.25W*15.5degC/W=35degC
Worst case:
2.25*1.15*15.5 = 40degC
This is acceptable to me.
PS, they will be mounted directly on the heatsink, so lets say a 0.8degC/W case to heatsink junction temp. They have 1.6degC/W junction to case drop.
So the die will run at: (above ambient in case)
(1.6+0.8+15.5)*2.25=40.25degC
*1.15(worstcase) = 46.3degC
at worst case internal temp = main heatsink temp
gives realitic to worst case ratings of die temp 90-110degC.
These diodes will live quite happily at a die temp of 100degC.
Hopefully internal temp will be a bit lower
2.25*1=2.25W
2.25W*15.5degC/W=35degC
Worst case:
2.25*1.15*15.5 = 40degC
This is acceptable to me.
PS, they will be mounted directly on the heatsink, so lets say a 0.8degC/W case to heatsink junction temp. They have 1.6degC/W junction to case drop.
So the die will run at: (above ambient in case)
(1.6+0.8+15.5)*2.25=40.25degC
*1.15(worstcase) = 46.3degC
at worst case internal temp = main heatsink temp
gives realitic to worst case ratings of die temp 90-110degC.
These diodes will live quite happily at a die temp of 100degC.
Hopefully internal temp will be a bit lower
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