Bridging the amp

[pchw]

Just bought a vintage Luxman M-111 power amp from ebay without user manual.
The specs of this beast as following:
"Can be operated in 4, 3, or 2 channel operation via bridging capabilities for each stereo pair,
25 Watts RMS x 4 from 20Hz – 20Khz into 8 ohms, THD <= 0.05%, Bridged – 75 Watts RMS x 2 (short term, 1 Khz, 8 ohm)"
Since I don't really use 4 speakers, I definitely love the 75wx2 set up than 25x2 :-) However,
I never bridged amp before. Does the following sound correct:

C - output channel of the amp
L - left
R - right
<---> - wire

LSpeaker(+) <---> C1:L(+) C1:L(-) <---> C2:L(+) C2:L(-) <---> LSpeaker(-)
RSpeaker(+) <---> C1:R(+) C1:R(-) <---> C2:R(+) C2:R(-) <---> RSpeaker(+)

If not, please advise.

Thanks in advance,

-fred-

[markw]

simply connecting the outputs wily-nily can have disasterous results.

Bridiging the two channels on my NAD amp requires that I first throw a switch on the back panel.

Then I would connect the positive lead of the speaker to ONE positive terminal and the negative lead from the speaker to the negative lead on the OTHER channel.

There is NO connector joining the two channels...

YMMV. Get hold of valid instructions.

[E-Stat]

Since I don't really use 4 speakers, I definitely love the 75wx2 set up than 25x2 :-) However,
I never bridged amp before. Does the following sound correct:

Fred, in addition to mark's comments, I would recommend you also check your speaker impedance and see if the amp can drive that load while bridged. Bridging amps typically drops the apparent load in half. If, for example, you have 4 ohm speakers, then the bridged amp pairs might individually see a 2 ohm load and not be happy about that.

rw

[pchw]

simply connecting the outputs wily-nily can have disasterous results.

Bridiging the two channels on my NAD amp requires that I first throw a switch on the back panel.

Then I would connect the positive lead of the speaker to ONE positive terminal and the negative lead from the speaker to the negative lead on the OTHER channel.

There is NO connector joining the two channels...

YMMV. Get hold of valid instructions.

Hi Mark,

Thanks for the reply. The NAD is definitely well thought in design of this feature.
The NAD bridging is all done "inside" which eliminates idiot like me fooling
around Yeah, I would like to get the instructions, but even google
and ebay turned up nothing .......

-fredv-

[pchw]

Fred, in addition to mark's comments, I would recommend you also check your speaker impedance and see if the amp can drive that load while bridged. Bridging amps typically drops the apparent load in half. If, for example, you have 4 ohm speakers, then the bridged amp pairs might individually see a 2 ohm load and not be happy about that.

rw

Hi RW,

Thanks for the reply.
I have a pair of Dahlquist DQ-12 (8 ohm) speakers which should be good enough
to handle the bridged output. The DQ-12 can be bi-wired, do you think it is better
off to bi-wire the DQ-12 with the 4 channels from the M-111, but 25W per channel
seems to be weak .....

-fred-

[markw]

Hi Mark,

Thanks for the reply. The NAD is definitely well thought in design of this feature.
The NAD bridging is all done "inside" which eliminates idiot like me fooling
around Yeah, I would like to get the instructions, but even google
and ebay turned up nothing .......

-fredv-

You might try the vintage pages here :

http://audiokarma.org/forums/index.php?

It's a well established site with a wide variety of knowledgable mixed nuts.