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Old 28th April 2004, 01:52 PM   #81
tiroth is offline tiroth  United States
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They are still recommending it for new designs. This was posted just over a week ago.

http://www.semicon.toshiba.co.jp/sol.../poweramp.html
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Old 28th April 2004, 03:08 PM   #82
MBK is offline MBK  Singapore
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I wouldn't be surprised if the 2sk389 was in fact alive and kicking. Whatever they tell me here I take it with a grain of salt. The English is not always the best, and rather than embarrassing themselves in attempting to describe a complicated situation they just cut it short and say "discontinued".

FWIW - what other transistors are a close match to the 2sk389? Maybe I can get an equivalent type locally. It's always nicer to play around with stuff that can be replaced easily in case of crash'n'burn
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Old 29th April 2004, 03:55 AM   #83
tiroth is offline tiroth  United States
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It works.

The MOX board is good to go. I won't have the discrete opamps verified until tomorrow as I...mmm...blew up the only one I built so far.

Note: the LP filter appears to cut off after 10k, but this is simply crosstalk in my soundcard.
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Old 29th April 2004, 04:20 AM   #84
tool49 is offline tool49  Canada
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Looks very nice, would you mind giving us a bit more info about the graph? What were the curve chosen, the Q of the filters, the target frequencies, etc...

Also why is the level at -10? What was the gain configured in the buffers?

Thanks!
Sébastien
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Old 29th April 2004, 08:06 AM   #85
moamps is offline moamps  Croatia
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Quote:
Originally posted by tiroth
It works.
Hi,
very nice work.
Quote:
I won't have the discrete opamps verified until tomorrow as I...mmm...blew up the only one I built so far. [/B]
Problem is maybe wrong BJT's orientation if you are using MPSA42 and 92.

Regards
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Old 29th April 2004, 12:45 PM   #86
tiroth is offline tiroth  United States
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Dimensions
The completed dual opamps have a footprint that is just about exactly .930x.930", or about 23.6mm square.

They stand 1.45" (37mm) tall, plus another .1" (2.5mm) if you use the headers I used.

The total height of a MOX board populated with opamps is about 2.25" (57mm), less depending on your use of sockets, etc.

Graph
The graph shows the curves for HP and LP @ 2kHz with Q of 0.5, 0.7, 1.4, 1.7 (on the HP).

Don't pay attention to the absolute gain; I needed enough headroom to show the high Q peaking.

Opamp
Moamps, I have the sinking feeling that you are right. I traced my layout against yours, not thinking that your red traces were problably bottom signal for a single layer board.

Time to fix.
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Old 29th April 2004, 02:01 PM   #87
tiroth is offline tiroth  United States
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EDIT: The Q values I listed may be wrong. It was rather late last night when I finally got to tracing the curves and I replied from memory. Comprehensive tests are coming tonight.
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Old 29th April 2004, 02:01 PM   #88
moamps is offline moamps  Croatia
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Quote:
Originally posted by tiroth
.....not thinking that your red traces were problably bottom signal for a single layer board. ...[/B]
Hi,

It's my fault too, sorry. OPAMP PCB is designed at the first time for BC550C and BC560C (diferent pinning). MPSA transistors are later placed on board (mirrored), but I didn't made changes on PCB board picture I published in MOX thread.

Regards
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Old 29th April 2004, 02:10 PM   #89
MBK is offline MBK  Singapore
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How about leaving it as is and using BC550/560?
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Old 29th April 2004, 02:53 PM   #90
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Quote:
Originally posted by tiroth
EDIT: The Q values I listed may be wrong. It was rather late last night when I finally got to tracing the curves and I replied from memory. Comprehensive tests are coming tonight.
Quote:
Originally posted by moamps

Hi,

It's my fault too, sorry. OPAMP PCB is designed at the first time for BC550C and BC560C (diferent pinning). MPSA transistors are later placed on board (mirrored), but I didn't made changes on PCB board picture I published in MOX thread.

Regards
Quote:
Originally posted by MBK
How about leaving it as is and using BC550/560?
I hope we can go with the MPSA 42 and 92 since I already have a stock just for this project.

BTW, that was what was shown in Moamp's original schematic.
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