Author Topic: h_a  (Read 5237 times)

0 Members and 1 Guest are viewing this topic.

Offline peranders

  • Administrator
  • Reached Nirvana
  • *****
  • Posts: 1230
  • Karma: +6/-0
  • Gender: Male
  • Forum owner
    • Sjöström Audio
h_a
« on: September 30, 2008, 04:48:45 PM »
Comments
In some places I think you have too little creapage distance between traces/pads.

How much trace width is required due to current? In many places you have too wide traces to the expence of difficulties to manufacture the boards.

Increase creapage!

Compactness is a virtue! I would have made the board more compact and tight. Even if the size is defined by case(?) I should have made it more compact (= less inductance)

The Vbe multiplier misses a resistor between base and collector and you'll need only one transistor and since you have symmetry you'll need only one point where you can sense the temperature. You should also decouple the Vbe multiplier with 100 nF at least.

Do you really need two heatsinks for the driver transistors? You can glue the temp sensing transistor to either the heatsink or to one of the driver transistors. You'll get a more compact solution using only one heatsink.

The Sziklai pair needs possibly a resistor in series with the compensation cap. Make room for both hole mounted and SMD.

The cascode of the input pair needs possibly decoupling between the cascode bases and the sources of the jfet's.

The power lines needs decoupling such as 100 nF + 100-470 uF between the rails and possibly down to ground if you'll have a dual power supply with ground. I would have made an option for it at least. I would have made groundplane in order to get a well defined electrical environment. You can place the caps very close the output transistors but keep in mind not to put the electrolytics too close => short lifetime due to heat.

Trimpots
Art no 64-634-18 http://www.elfa.se

Model 72PT https://www1.elfa.se/data1/webroot/Z_DATA/06463012.pdf  very nice.

Skip the hot relief pads for the power transistors. Not necessary.

The bottom traces can go under the heatsinks!

The input stage can be rotated 90 deg in order to get it more compact.

The input stage should have decoupling and I should have made it to ground.

Why don't you make space for a Zobel network and output inductor?

Fuses?

The jfet's tighter?

I'll recommend that you write pcb name and revision status in each layer. Remember that you can have it outside the board in some layers.

Bigger pads for the power transistors and use round ones.

Use round pads for the TO220 parts. 75 mils is OK.

Skrewholes, a bit tight to the copper areas.

The speaker connections miss text. You have only the designators.

Otherwise it looks good.
« Last Edit: September 30, 2008, 07:24:35 PM by peranders »
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff