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Old 30th September 2013, 09:06 AM   #1
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Default Current Dumping Amplifier

Simple DIY frendly amplifier, descrite circuit use voltage global feedback.
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File Type: jpg Apex BX100.jpg (180.3 KB, 2701 views)
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Old 30th September 2013, 10:31 AM   #2
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PCB design by 'spookydd' but not tested.
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File Type: png BX100 sch.png (51.1 KB, 2490 views)
File Type: png BX100 top.png (139.2 KB, 2172 views)
File Type: png BX100 top1.png (98.1 KB, 1969 views)
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Old 30th September 2013, 11:14 AM   #3
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Looks nice! I've been trying to find the current dumping bridge elements and not sure which ones they are (apart from the obvious 1uH and R13 I believe).

Jan
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Old 30th September 2013, 11:19 AM   #4
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Quote:
Originally Posted by jan.didden View Post
Looks nice! I've been trying to find the current dumping bridge elements and not sure which ones they are (apart from the obvious 1uH and R13 I believe).

Jan
L1, R15, C8 and R6
Regards
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File Type: pdf Current-dumping-audio-amplifier-A-EN2-920-QUA.pdf (869.0 KB, 838 views)

Last edited by apexaudio; 30th September 2013 at 11:40 AM.
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Old 30th September 2013, 01:06 PM   #5
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Thanks! Also for the nice scan of the article - mine is much worse!
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Old 5th October 2013, 02:34 AM   #6
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Hi all,

Here is something to perhaps stir a little interest:

I made a slight change to the board so the TO3s were a little more angled flat and that gained 5mm in width, so the board is now 75x100 instead of 80x100.

Not much gained, but it's something.

I made some 3D outputs, just for kicks, and even tried adding a corner profile under the TO3s to make it look even a little more bluffing. It's still missing a good size heatsink on its back, but maybe I can add this later.

It's not perfect, and there are always improvements that can be made. It would be nice to test this. The board as it is wouldn't pose any problem to a board house to make, so if we can make it as good and worthy as it can be, maybe we can have a run made.

I have more than 50 2N3773 in my old stock, so those would be better put to work than staying in storage...
Attached Images
File Type: png BX100_top.png (553.2 KB, 1638 views)
File Type: png BX100_top_silk.png (39.7 KB, 350 views)
File Type: png BX100_silk.png (668.0 KB, 256 views)
File Type: png BX100_HS.png (817.2 KB, 247 views)
File Type: png BX100_copper.png (55.0 KB, 307 views)
File Type: png BX100_bottom.png (377.8 KB, 180 views)
File Type: png BX100_bottom_.png (42.0 KB, 217 views)
File Type: png BX100_board_top.png (57.0 KB, 301 views)
File Type: png BX100_board_bottom.png (52.6 KB, 235 views)
File Type: png BX100_3.png (348.4 KB, 303 views)
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Old 5th October 2013, 02:52 AM   #7
danny92 is offline danny92  Portugal
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Hi there,

Interesting project
This amplifier uses a bootstrapped VAS(TIS), right?
I don't understand the compensation method, but it's an interesting one.
What the 1.5 pF capacitor is doing in the lower output transistor?
The 150 pF are used to lower the Q and reduce the chances of oscillation, right?

Best regards,
Daniel Almeida
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Old 5th October 2013, 06:22 AM   #8
Mooly is online now Mooly  United Kingdom
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1n5 (1500pf)
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Old 5th October 2013, 09:14 AM   #9
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Quote:
Originally Posted by spookydd View Post
Hi all,

Here is something to perhaps stir a little interest:

I made a slight change to the board so the TO3s were a little more angled flat and that gained 5mm in width, so the board is now 75x100 instead of 80x100.

Not much gained, but it's something.

I made some 3D outputs, just for kicks, and even tried adding a corner profile under the TO3s to make it look even a little more bluffing. It's still missing a good size heatsink on its back, but maybe I can add this later.

It's not perfect, and there are always improvements that can be made. It would be nice to test this. The board as it is wouldn't pose any problem to a board house to make, so if we can make it as good and worthy as it can be, maybe we can have a run made.

I have more than 50 2N3773 in my old stock, so those would be better put to work than staying in storage...
Nice work, thanks for this pcb design.
Regards
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Old 5th October 2013, 04:35 PM   #10
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Here is a 3D with a big heatsink added. That heatsink is an SK155 from Fischer, 120mm long.

This brings a topic: calculating the needed heatsink.

I'm thinking of making a spreadsheet with the calculations.

If we use +-55V rails, we're looking at an amp that could give around 150watts rms into 8 ohms, more or less.

Now for the power dissipation, if we start with a gross figure of 75 watts of heat to get rid of. Is that about right?
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