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Old 25th February 2012, 04:29 PM   #261
Eddie2 is offline Eddie2  Netherlands
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Hi everyone !
I also found the LME49830, and it looks very nice to me!
But I have a question: Could it be an idea, to use the IRFP630 ?
It can handle 400 V, 23 A, and 280 W.
I did not found a P-channel equivalent yet. Anyone an idea ?
If one wants to build something for 300...400 Watts, one can get 20V over the FET, while
drawing 10 Amps, meaning a dissipation of 200 Watts.
Any advices ?
Thanks in advance !
Eddie
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Old 9th March 2012, 09:23 PM   #262
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I just ordered two of the compact boards. Looking forward to a fine amplifier.
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Old 9th March 2012, 11:27 PM   #263
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I also ordered the power supply board. It calls for 20 of 1,000uF/50V with 7.5mm lead spacing. It turns out that there are plenty of 2,200/50V capacitors with 7.5mm lead spacing and 16mm diameter... whoa! 44,000/50V of capacitance!
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Old 10th March 2012, 08:33 AM   #264
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Quote:
Originally Posted by Kalle-Grabowski View Post
Hi Panson,

first of all I'd like to thank you for your well documented and well engineered designs. That's quite a massive effort. I'm also impressed how good your PCBs look.

Perhaps there's still some room for improvements. ....
Hi Kalle,

Thank you very much for your comment. The current compact PCB has definitely room to improve. Adding big caps might be difficult
in order to keep it compact, aimed for below 80 W power. I also wonder if this is a good idea to place "reservoir" cap onboard. I did that in some of previous/current layouts. But I also question myself to date if this is wise to do so. My latest preference is all massive reservoir caps very close to the rectifier diodes in order to have a very short path for huge charging current.

Local decoupling caps near output devices are definitely employed without doubt.
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Old 10th March 2012, 12:00 PM   #265
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Quote:
Originally Posted by panson_hk View Post
Hi Kalle,

Thank you very much for your comment. The current compact PCB has definitely room to improve. Adding big caps might be difficult
in order to keep it compact, aimed for below 80 W power. I also wonder if this is a good idea to place "reservoir" cap onboard. I did that in some of previous/current layouts. But I also question myself to date if this is wise to do so. My latest preference is all massive reservoir caps very close to the rectifier diodes in order to have a very short path for huge charging current.

Local decoupling caps near output devices are definitely employed without doubt.
What about on board voltage supply regulators for the chip? I was thinking of replacing C10 and C11 with zener diodes and scaling R13 and R14 accordingly. That would be a simple regulator right there.

Also, what kind of transistor do we use for the Vbe multiplier?

It might not make much difference, but C8 should be a smaller 0.1uF MLC or film type, not a big electrolytic.

Otherwise, thanks for your hard work!

I'm going to use low ESR electrolytics ($$$) for the power supply board.
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Old 10th March 2012, 12:25 PM   #266
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So, these amps are set up for 28dB of gain? That seems like a lot. I know it's in the data sheet. Lower -3dB point seems to be about 1Hz. Phase shift is a few degrees @ 20Hz.
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Old 10th March 2012, 03:31 PM   #267
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Did you see this application note from National?
http://www.ti.com/lit/an/snaa058a/snaa058a.pdf
this is like a no brainer. They give you everything right there. Dang.

Last edited by dirkwright; 10th March 2012 at 03:33 PM.
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Old 12th March 2012, 10:52 PM   #268
atupi is offline atupi  Romania
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Panson i see all the measurements made for 8ohm speakers. I intend to build a low power version (50w). One pair of thermaltrack's would be enough ? Are needed some more adjustments ?
I need more than 2pcb's from your website "New Compact 4981x ThermalTrak Amplifier Board " ?
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Old 13th March 2012, 03:13 PM   #269
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Quote:
Originally Posted by dirkwright View Post
What about on board voltage supply regulators for the chip? I was thinking of replacing C10 and C11 with zener diodes and scaling R13 and R14 accordingly. That would be a simple regulator right there.

Also, what kind of transistor do we use for the Vbe multiplier?

It might not make much difference, but C8 should be a smaller 0.1uF MLC or film type, not a big electrolytic.

Otherwise, thanks for your hard work!

I'm going to use low ESR electrolytics ($$$) for the power supply board.
Hi,

You can add zener diodes as simple regulator. If I were adding a regulator for the front end, I will use linear regulator.

Do you use conventional output devices instead of ThermalTrak? Vbe multiplier can be MJE15030.

Why do you use small cap for C8?
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Old 13th March 2012, 03:17 PM   #270
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Quote:
Originally Posted by atupi View Post
Panson i see all the measurements made for 8ohm speakers. I intend to build a low power version (50w). One pair of thermaltrack's would be enough ? Are needed some more adjustments ?
I need more than 2pcb's from your website "New Compact 4981x ThermalTrak Amplifier Board " ?
Hi, One pair ThermalTrak NJL3281D/1302D is enough for 50 W / 8 Ohms. Very safe for driving reactive loads as well. You need to adjust bias setting, nothing more. Are you doing stereo amp?
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