Bridged GC according to National application sheet

[Nuuk]

I want a GC with more power to drive some OB speakers. Should I go with bridged or parallel design?

I think from what I have read, more current is better with OBs but would like some expert opinion before I start soldering.

[filholder]

Hi Nuuk,

This sounds interesting, what are you planning on using the 4870?

[Nuuk]

Nope - LM3875!

[halo0925]

What series of OB's? they seem to have a pretty high sensitivity level 94 to 96db 1W1M and there impeadance seem's pretty normal 6 to 8ohm range, they do seem to have a little more complex frequency/impeadance curve.
I would go with a bridge if the impeadance wont drop below 6 to 8 ohms but only with a +/- 25 to 28VDC supply, as to keep the dissipation down.
If these things are really impeadance monsters I would go parallel at a higher supply voltage +/- 35VDC.
If you really want some get up and go, go with a BPA solution.

[Nuuk]

I'm running Hawthorne AUdio SIs at present. My Goodmans 201s are quite happy with a single-chip amp but they don't have to go so low as the SIs.

I'm using a single LM3875 IGC at present but comparing it with an Autocostruire CT MC4x100 (with the outputs paralleled) it feels like I could do with a bit more power for listening loud.

I've got a 28 volt regulated supply I can use so that's not a problem.

I just don't need as mch power as the BPA200 provbides.

[owen]

Nuuk,

I'd go BPA too... That way, you get heaps of current and Voltage to provide solid load tolerance - you never know when you might just need it


Owen

[Nuuk]

Well you should at least have an idea when you will need all that power Owen!

I'd have to buy more chips for BPA and this is intended to be a low cost project. In fact, even if I had enough chips, I would be tempted to build one bridged, and one paralleled GC, just to find out which did sound better with the OBs.