Inverted outputs?

[nascarmann]

OK....start explaining to me exactly how this works on a Pre-amp? It will allow you to bridge an amp that is not bridgable through the amp by doing it in the pre-amp? How do you wire this? Am I thinking right? HELP!

[HBombToo]

What are you referring to Nascarmann? Are you referring to my Post with Dr. Spec?

EFFIN Jr. Pissed me OFF last night!

[nascarmann]

No.....I scored a pre-amp with inverted preouts.....I think this is to bridge a stereo amp? Yeah.....Jr tried though.....glad Michael came through if not Jr.....

[nascarmann]

Russman.....can you help here?

[madmax]

nascarman,
What happens is your pre-amp or whatever audio device (may be a box designed only for this purpose) has a normal and an inverted output for each channel. (Soundcraftsmen did this a lot). What happens is you input the normal output to the left channel input on the amp and the inverted to the right channel input of the amp. You make sure the grounds of each output channel can be and are connected together. The outputs of the amp are left channel output + goes to the + speaker wire and the right channel + goes to the - speaker wire. Obviously you set the gain of each channel (assuming it is variable) to the same position. This allows you to bridge an amp L and R output into one speaker thus "bridging" an amplifier which could not normally be bridged. You would need two equal amps, one for the left channel and one for the right. Hope this explains it for you.
madmax

[madmax]

I forgot one thing. If you use your 1C's you can not do this unless you have a pin/blade connection on your sda cable and buy a 1:1 isolating transformer and connect it to the sda cable which isolates the grounds. The reason is that the grounds of the two amps are no longer at the same potential if you bridge them in this mannor.

[nascarmann]

Thanks madmax.....not sure if I will keep this pre.....probably won't have room to set it up? If I do....maybe you can help me with the transformer....I guess I will need to build one....they are no longer for sale are they?

[nascarmann]

Oh....they are pin/blade..

[hoosier21]

This inverted outputs, is it not just a simple swapping of + and -?
Some equipment back in the day had a phase invertion button, that would reverse the polarity of the signal.

It was felt that some recordings, from the original performance to the tape lp or whatever, the signal would get inverted, this was thought to lessen the impact and stereo image.

[nascarmann]

hoosier21

This is a new deal for me. All I have heard about this is it lets you bridge an amp that is not capable of bridging on it's own. So....I'm not sure if it just swapping or not. This pre-amp was Yamaha's flagship in it day....mid 80's. The Yamaha amps of this era were not bridgable on there own(except pro series)....so I guess this is why they did this??

[madmax]

You can't really just swap the + and - because the - side is hard wired together. You can use the normal output only just as you would any other piece of equipment. If you ever need to do the xformer thing let me know. It is so simple you would not believe.
madmax