QUAD 909 Stereo - How to Mono?

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#3
nigelwright7557 said:
You would need an inverter to invert the signal into one of the stereo channels.

Then take the output from the two live pins of the outputs.

Make sure your amp will take bridging mode before trying it.
The output impedance halves for bridge mode and os takes twice as much power as normal mode.
Click to expand...

Thank you for the information. I do appreciate the information although I need more details like a schematic. I know several people have done many upgrades on the QUAD 405 & 405-2.

Does anyone have specific information on how to do this OR if it can be done?
 
#4
Quad 909 schematic.
DADA Electronics - Downloads

If you have a preamplifier with balanced outputs,
you don't need to invert the signal.
A balanced output produce non inverted + inverted signal.

Feed one channel with non inverted.
Feed the other channel with inverted.

Connect the speaker between the two red output terminals.

If you have no balanced preamp, you need to build a inverter circuit using an op amp.

This is general info for bridging, i never tried with quad 909.
 
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#5
bobodioulasso said:
Quad 909 schematic.
DADA Electronics - Downloads

If you have a preamplifier with balanced outputs,
you don't need to invert the signal.
A balanced output produce non inverted + inverted signal.

Feed one channel with non inverted.
Feed the other channel with inverted.

Connect the speaker between the two red output terminals.

If you have no balanced preamp, you need to build a inverter circuit using an op amp.

This is general info for bridging, i never tried with quad 909.
Click to expand...

Now we are getting somewhere! My problem is that my current preamplifier does not have balanced outputs.

Do you have an example of an inverter circuit? What can be some of the issues when trying this, that is, failure or problems when adding these circuits?
 
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