SymAsym - "The Sequel", AAK's PCB Builders Thread

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A

AAK

Member
Joined 2004
Hi Aidan,

Do you know the LEDs forward voltage? If your not sure connect the LEDs cathode to about a 5k resistor and then a 12V supply and measure the voltage from the cathode to ground. If the voltage measures around 1.75V to 1.85V they should work fine. If not you may have to adjust the front end bias resistor R19 to compensate.

Regards,

Al
 
A

AAK

Member
Joined 2004
Hi All

I just finished a low power version of my DTV Rev_1.3 PCB with the same amplifier circuit but with only a single OT pair and no on-board PS. The PCB measures only 2.5" (63.5mm) x 2.95"(75mm) which is perfect for a home theater amp using an external PS. The PCB provides provisions in the OT section to accept Lateral Mosfets for an all input/output fet operation.

Attached is a picture of the PCB and schematic. Since this is a low power version I dropped the rails to +/-36V and bypassed the differential/VAS cascodes. From my testing bypassing the VAS cascode increases 2HD resulting in a softer sweeter sounding amplifier.

Al
 

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A

AAK

Member
Joined 2004
BOM update, Fuse Clip part number change.

Hi All

I've attached a new BOM with a new Fuse Clip part number (576-01000054H) thanks to sng001. Igreen pointed out that the old part number had the wrong lead spacing. If you already bought them try bending the leads inward far enough to see if they reach the pads. Sorry about that.

Regards,

Al
 

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C

chalkandtalk

Member
Joined 2006
Hi Al,

sorry for the slow progress here but finances are still recovering from Xmas. But I am getting there slowly. I'm also building one of Rod Elliot's 24db active 4 way crossovers - hence the need for more amps.

I have found out that VF for the LEDs that I've got is 2V for green and red and 2.1V for yellow. I measured a green one as you suggested and it was 1.9V - close. Do you think these will do?

Thanks for your help

cheers

Aidan
 
A

AAK

Member
Joined 2004
Hi Aidan,

Refer to post #36 regarding the LEDs.

I think they'll do but you may have to adjust R19. Initially leave R19 at 261 ohms and check the current across R23/R24. If the current is to high than increase R19 until you get it down between 1.65ma to 1.75ma.

Regards,

Al
 
Ed LaFontaine

Ed LaFontaine

Member
Joined 2004
Al,

The appearance of this edition fell into place for me. It will become part of a work in progress:
New speakers based upon Geddes/Parham/Zilch/augerpro. A 2-way using a hi-eff. 12" under a CD 90 x 50 horn. Bi-amped using your offering and the F-5. The bottom will be 4 X 10" subs. I expect to get ~117 dB if needed. ;)

Boards are in-hand. Parts are ordered. Aluminum has been cut and tapped. The fun continues. :D
 
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