Bridging 2 mono blocks of lm3886

[rs1026]

i have two separate mono blocks for lm3886. There are no connections /jumper avialable on the pcb for bridge mode connection.Can I still connect thme in bridge mode with no addtional components directly slodering the wires to lm3886 pins??

[psychosteve]

never having done it, i dont know.

id say thet if you got two mono blocks, both built the same then no, because you need one half the signal inverted.

id say it would sound better any way if you used a twin op amp buffer, one side non inverting the other inverting, to supply the mono blocks, keep the gain at zero for both sides. the components are cheap and easy to build. there is a thread on here about bridging boards, try that. or just wire to the pins, there are only 8 pins on twin op amps.

[richie00boy]

psychosteve's advice is good, but for bridging to work it's essential that the two monoblocks share a common ground point. By this I mean the 0V point, not the safety earth. This is not always easy to achieve with true monoblocks.

[psychosteve]

cheers richie, i forgot about the earth loop problems, how could i do that!! ive had no end of probs with them.

probly be easier, and sound better to take the boards out of monoblock cases and build both into a single case, with the twin buffer inside aswell. that should ease conection to inputs and speakers. hope that helps, steve.. ..

[richie00boy]

Steve, it's not the earth loop problem as such. The problem is that the amps must be tied closely (in voltage terms) together to function properly. If they are not then e.g. amp 2 will be at signal+whatever voltage higher/lower than amp 1.

Not only that, but because the amps are now working such that current is flowing e.g. out of the +ve rail of amp 1 and into the -ve rail of amp 2, they must share the same PSU for the current to flow.

Putting them in the same case with a shared PSU is really the only solution.

[psychosteve]

my mistake,, i knew what i meant and it was what you said, just me being to sleepy to type the proper wording. and yes build into a single case is probly the best way. see you soon, steve.. ..

p.s. richie, did you see my post on the group buy? hope all is well.

[soundNERD]

I know you don't want to add additional components, but I think thats the only way to do it.

Check out Texas instruments DRV134.

[psychosteve]

another way is get two more chips, and build two inverting or non inverting, depending on what you have already, you need the opposite, into the two mono block cases bridging to the two amps you have allready.

this will give you two channels both with bridged chips!!! you will need to be carefull on design as most inverting GC's use different feed back paths/t netwrks and the like. and be carefull to match the gain.

i dont see why it wont turn into a much higher powered dual mono set up.

or parallel the amps you have allready, and drop the ohms by parallel mounting your speakers, you could drop 4 speakers parrallel pair to pair for 2ohms ( i think!!!) but you may be running up the draw on your transformers.

have fun and dont blow yourself up. see you soon, steve.. ..