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Old 30th December 2012, 09:45 AM   #211
alex mm is offline alex mm  Romania
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.....Thanks L.C , another PCB , attached

Happy New Year to all diy members ! Alex.
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Old 30th December 2012, 02:38 PM   #212
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Quote:
Originally Posted by alex mm View Post
.....Thanks L.C , another PCB , attached

Happy New Year to all diy members ! Alex.
Hi Alex,

I love this last one. Could you just include solder pad for trimmer located on 15K resistors. One fine tuned done resistor equivalent value take place on 15k location.

Marc
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Old 30th December 2012, 03:21 PM   #213
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LC, according to nice Alex mm work, do you think VAS tansistors heatsink are sufficient? They mesure 15x10mm surface. On ebay wa can find those unit that are 20mm long.

Marc
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Old 30th December 2012, 03:52 PM   #214
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Quote:
Originally Posted by alex mm View Post
.....Thanks L.C , another PCB , attached

Happy New Year to all diy members ! Alex.
Alex by using 1uf with 7.5mm pin spacing tou could improve output layout and feedback return.

Marc
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Old 30th December 2012, 04:47 PM   #215
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Alex, one more think you forget the zobel network according LC shematic

Marc
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Old 30th December 2012, 05:21 PM   #216
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LC, according to nice Alex mm work, do you think VAS tansistors heatsink are sufficient? They mesure 15x10mm surface. On ebay wa can find those unit that are 20mm long.

Marc
Hi Marc

VAS BJTs have 0.6 W dissipation, at 45°C final temperature, we need heatsink with 30 K/W temp koeficient, so check the specifications.

If VAS BJTs are on the top of PCB, 120 ohm bias spreader is OK, if they're on the main heatsink, ref zener (shunt regulator) is a must. I measured Vgg=1,5165 V at 100 mA output bias.
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Old 30th December 2012, 05:38 PM   #217
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Measurements from today gives similar results like yesterday. 100 kHz 16 Vrms on 8 ohm (2 Arms) gives +5 mV when loaded, so VSSA has negative output impedance.

At 1 MHz 16 Vrms on 8 ohm I measured 100 mV voltage drop on output impedance, that gives us 50 mohm output impedance or damping factor 160.

-3dB lower roll-off is at 6 Hz so maybe I'll higher feedback impedance to 2,2k/100 ohm to go down to 3 Hz.

I'll assemble cmos square wave generator to test 10 kHz to 1 MHz squares response.

Regards L.C.
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Old 30th December 2012, 05:42 PM   #218
pergo is offline pergo  Italy
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can you test also 100Hz and 1kHz damping factor?
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Old 30th December 2012, 05:49 PM   #219
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This VSSA PCB gives you craziest simple amp that you can assemble in a hour.

New Year's gift from me and Alex, enjoy.

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Old 30th December 2012, 05:53 PM   #220
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can you test also 100Hz and 1kHz damping factor?
From 20 Hz to 10 kHz VSSA gives +3 mV when loaded, so stil negative output impedance.
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