Searching for a PCB for a BR100 - Bridged LM3886

[seebaer]

Hi,

I'm looking for a PCB to build a bridged LM3886 as shown in AN-1192 from National. Where can I find a PCB? I didn't find one in the typical gainclone shops.

Thanks, Bernd

[TheSeekerr]

Why would you want one? Buy a stereo pair from one of the usual sources, and knock up balanced line driver around DRV134 (or around a pair of opamps, see http://sound.westhost.com/project87.htm ) to provide the necessary inputs.

DRV134 is a seriously easy chip to implement, the only necessary external components are the supply decoupling capacitors (and, obviously, the +/- 15V power supply). Alternatively, there exist suitable transformers that can do the job, see http://www.shine7.com/audio/bpa300v2.htm

These are both better solutions than the 1-inverting, 1-non-inverting setup described in the application notes.

[ST7677]

Originally Posted by TheSeekerr

Why would you want one? Buy a stereo pair from one of the usual sources, and knock up balanced line driver around DRV134 (or around a pair of opamps, see Balanced Transmitter and Receiver II ) to provide the necessary inputs.

DRV134 is a seriously easy chip to implement, the only necessary external components are the supply decoupling capacitors (and, obviously, the +/- 15V power supply). Alternatively, there exist suitable transformers that can do the job, see DIY BPA300 v2 6x LM3886 300W audio Amplifier

These are both better solutions than the 1-inverting, 1-non-inverting setup described in the application notes.

Is there any difference in the above two approaches? i.e. is one approach better than the other? Why?

The LM3886 bridge application note AN1192 suggests using an inverted and a non inverted configuration to bridge. Most people seem to be looking at BPA using DRV134. Is it because they are using 6 LM3886 instead of just 2?
What is the better approach to bridge just 2 LM3886 chips?


I am building a 3+3 channel amp. Each channel will have 2 LM3886 in bridge configuration. So looking for the best approach to bridge.
DRV134 adds to complexity and real estate issues considering that there are 6 amps to be bridged. I am wondering if there is any sonic benefit of taking that approach.

[pacificblue]

Try the Simplest Ever Bridging Adapter for Amplifiers. Cheap, simple and the result is the same.

[AndrewT]

Does ESP's inverting amplifier operate at unity gain?
What does ESP's 100r on the +IN of the inverting amp do for the circuit?
Does the "added resistor" give any significant noise problem?

[pacificblue]

I don't see why it should not work at unity gain. On the other hand the LM3886 does not work at unity gain, so that circuit need not work at unity gain either. What use is a BTL power amp with unity gain?

originally quoted from 'http://sound.westhost.com/project20.htm'
The input of the second amp should be grounded as shown (using a 100 ohm resistor), to prevent noise pickup.

100 Ohm is in most cases smaller than even the tolerance of the feedback resistor. Its Johnson noise can therefore certainly be regarded as insignificant.

That resistor should also have a cancellation effect on the bias current which should in theory reduce THD, and it will limit the current that flows into the amp input thus providing some protection during start-up and shut-off.