Old school hcca 225 amp modification?

[mcbigman]

Hi guys, I'm new, be nice. Thank I'm relieved i finally found someplace on the web that has a clue regarding car audio tech. So thanks up front. I have been reading several threads over the last several days regarding bridging older orion amplifers. I have a G1 225 hcca that i would like to bridge mono but for the life of me i cannot find a 400 bdg module on ebay. So my question is, can i modify the amp?? or build a bridging module for it. Realy i just want to get on with this project so what ever you guys (or gals) think is the best and quickest way to solve this problem i appriciate the advice.

[Perry Babin]

You need to invert one channel so it can be bridged. To do this, you need to build an inverter. If you use the supply voltage in the DIN, it will be simple.

Using an op-amp (TL072 or similar)...

Connect the non-inverting input (pin 3, if you're using an 8 pin dual op-amp) to the ground pin in the DIN.

Connect the positive power supply pin of the op-amp to the +15v pin in the DIN.

Connect the negative power supply pin of the op-amp to the negative 15v pin in the DIN.

Connect a 4.7k ohm resistor from pin 1 of the op-amp to pin 2 of the op-amp.

Connect a 4.7k ohm resistor from pin 2 of the op-amp to the signal source.

Connect pin 1 of the op-amp to the right channel input of the DIN.

This will produce a signal that's the same level as the input but the output will be inverted. This is essentially what you'll have:
http://www.bcae1.com/images/swfs/opampinvertingamp.swf

You will use the two positive speaker wires of the amp for bridging.

To prevent noise and/or oscillation issues, connect two 0.1uf mylar caps from the positive and negative power supply pins of the op-amp to the ground pin in the DIN.

[mcbigman]

Thanks Berry, i think i might be able to handle that. Back in the late 80's early 90's when i was installing and selling orion equipment i think i only saw one customer with the 400bdg. So when i bought this amp i completly forgot that i needed one to bridge it. thanks again for the help.
great web page!!!!! awesome tech info, used it months ago when designing my speaker box.
Thanks!!!

[Perry Babin]

http://bcae1.com/temp/DINBridgingModule/IMG_5950b.jpg

http://bcae1.com/temp/DINBridgingModule/IMG_5951b.jpg

http://bcae1.com/temp/DINBridgingModule/IMG_5952b.jpg


These photos show a working bridging module. Instead of using op-amp A of the dual op-amp, I used op-amp B. The pin placement worked out better in the DIN.

pin1 = pin7
pin2 = pin6
pin3 = pin5

Pins 4, 5 and 8 are soldered directly to the DIN connector. I didn't take the time to add the 0.1uf caps. If you use this, you would probably have to use 1000pF (1nF) caps.