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Old 12th March 2012, 08:00 PM   #61
dadod is offline dadod  Croatia
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Quote:
Originally Posted by keantoken View Post
In the third schematic, shouldn't Q13 be MJL1302A?

I always thought PCBs without silkscreen looked gaudy, but you make it look good. Most PCBs are that awful yellow-brown...
Second schematic, and yes you are correct.
Thanks, and there is a silkscreen.
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Old 12th March 2012, 08:09 PM   #62
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Oh, well then I meant the greenscreen, or is that what they call it? Arr ye mus' un'rstand.
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Old 26th March 2012, 04:59 PM   #63
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All PCBs are ready. Now is time to start some measurements, but first I will listen some music over this PCBs connected together. ThermalTrak bias current is very stable from 25 degree to 60 degree centigrade. I will show a result after I finish test measurements. For now here are all needed PCBs.
dado
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Old 26th March 2012, 05:13 PM   #64
AndrewT is online now AndrewT  Scotland
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Gad,
the thickness of the L angle for connecting to the heatsink is too thin.
4 devices can dissipate a lot of heat.
Try for at least 50% thicker and if you can source it, double the thickness.

The two device version is possibly OK.
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Old 26th March 2012, 08:34 PM   #65
dadod is offline dadod  Croatia
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Quote:
Originally Posted by AndrewT View Post
Gad,
the thickness of the L angle for connecting to the heatsink is too thin.
4 devices can dissipate a lot of heat.
Try for at least 50% thicker and if you can source it, double the thickness.

The two device version is possibly OK.
Thanks Andrew, the thickness is 3 mm and I never have any problem with heat transfer to the heatsink. By the way I could not find thicker alumina here in Zagreb.
Two device version is the Power Suply Regulator, a kind of a capacitor multiplier.
dado
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Old 29th March 2012, 11:03 AM   #66
dadod is offline dadod  Croatia
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Both channels are playing now. It is to early to final comment of the sound, but I like it, very punchy bass well controlled clean mid and heights.
I wanted very well thermal control of the output stage bias. I divided this in two part. First the drivers are situated on separate heatsink together with the bias transistor (BD139). The bias spreader use ThermalTrak diodes connected in the bias transistor emitter. In this way I tried to separate thermal drift of the drivers from the output ThermalTrak transistors. The bias spreader transistor it self has to compensate thermal drift of the drivers and ThermaTrak diodes have to compensate thermal drift of the ThermalTrak output transistor only.
And I think the result is quite good. In first seconds after power on the bias current will go up from 60 mA (per output pair) to 130 mA and after the driver temperature have settled, temperature increment of the output transistor will no influences the bias current. It stays at between 125 mA to 130 mA. I was measuring the voltage drop on the output transistors emitter resistor and it stay quite firmly at 20 mV.
Next, I m going to do some measurements with sinus, triangle and square waves. I will insert different value capacitors parallel to the dummy load.
Dado
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Old 29th March 2012, 11:06 AM   #67
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Thumbs up bravo

Quote:
Originally Posted by dadod View Post
Both channels are playing now. ....
Next, I m going to do some measurements with sinus, triangle and square waves. I will insert different value capacitors parallel to the dummy load.
Dado
Congratulations!
the sound is better than from your JHLs?
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Old 29th March 2012, 11:17 AM   #68
dadod is offline dadod  Croatia
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Originally Posted by padamiecki View Post
Congratulations!
the sound is better than from your JHLs?
Not sure yet, this amp has to play some time as electrolytic caps need a time to reform(thay stayed in my drawer) One think is certain, bass is more puchy and better controled.
JLH amp realy a treasure (after my modest improvement) and I like it. It uses original Hitachi lateral, I am not sure how it will work with other producers lateral.
dado
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Old 29th March 2012, 11:24 AM   #69
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Nice one

What's output L inductance? Output impedance at 20 kHz?

Andrej
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Old 29th March 2012, 11:49 AM   #70
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Quote:
Originally Posted by Lazy Cat View Post
Nice one

What's output L inductance? Output impedance at 20 kHz?

Andrej
Thanks Lazy Cat!
I am not sure, did not do any measurement yet. As it uses triple OPS and very high NFB(70dB at 20kHz) it should be quite low.
dado
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