Power Amp AB Speaker Swtiches

[GAWD]

This a question I've never gotten an answer too. My power amp has buttons for "A" speakers and "B" speakers. It's a 100w * 2 power amp. Now if I use either A or B I understand I'm getting 100w per channel to which ever set I'm connecting. What if I run both A and B at the same time?

• Will I be getting 50w per channel to all four speakers?
• Is it safe to do this? Am I harming either the speakers or the amp in any way?
• Can I use both the A and B connections at the same time to bi-wire my speakers? Any issues with that?
• If i'm using both the A and B at the same time is there any chance my amp is now seeing a 4ohm load instead of 2x8ohm loads?

[HAMP]

I think you may need to give the model number for your amp so that someone can look that information up for you.

[GAWD]

It's a NAD 2400 THX

[Big Daddy]

Originally Posted by GAWD

This a question I've never gotten an answer too. My power amp has buttons for "A" speakers and "B" speakers. It's a 100w * 2 power amp. Now if I use either A or B I understand I'm getting 100w per channel to which ever set I'm connecting. What if I run both A and B at the same time?

• Will I be getting 50w per channel to all four speakers?
• Is it safe to do this? Am I harming either the speakers or the amp in any way?
• Can I use both the A and B connections at the same time to bi-wire my speakers? Any issues with that?
• If i'm using both the A and B at the same time is there any chance my amp is now seeing a 4ohm load instead of 2x8ohm loads?

While this would be very convenient to use both A and B at the same time, it can only be done if the outputs are wired in parallel, rather than series. Many receivers and integrated amplifiers that have two speaker outputs will connect them in series when they are both selected at the same time, to protect the amplifier from an excessively low impedance. I don't believe your amplifier's manual has any information on this. A simple test would be to select both A and B and connect one speaker only to either speaker output A or B. If there is no sound from the speaker, then it means that they are connected in series. If you want to bi-wire a speaker, you will need to connect both of the bi-wire cables to one pair of speaker output terminals.


Series Loudspeakers:

This connection would give a final impedance of 8 ohms.

Parallel Loudspeakers:

This connection would give a final impedance of 2 ohms.

Nad Borchure:
http://www.nadelectronics.com/img/da...s/NAD_2400.pdf

Go to the bottom and see information:
http://cgi.ebay.com/NAD-2400-PE-THX-...d=p3286.c0.m14

NAD.jpg

[sorrell]

I s there a problem to cross the outputs AR + BL or AL + BR, with the amp switched to A+B all the time.
Is the amp working twice as much in this way (with 2 channels having no load)? Is there a problem if it has no speakers to send the signal to?
Thanks!

[Big Daddy]

Originally Posted by sorrell

I s there a problem to cross the outputs AR + BL or AL + BR, with the amp switched to A+B all the time.
Is the amp working twice as much in this way (with 2 channels having no load)? Is there a problem if it has no speakers to send the signal to?
Thanks!

In most cases, there should not be a problem with no load.

[JJJMan]

An additional question regarding this topic.

could i technically bridge the A+ and A- with B+ and B- of the Left and Right Channels? would it be a moot point putting them together or would i actually use both channels to push to the front speakers?

Additioanlly, could i use front A as highs and front B as Low's for Bi-wiring, or am i reaching a bit too far?

visual:

___________________________
l LA+ LA- l
l I I l
l LB+ LB- l
l l
l RA+ RA- l
l I I l
l RB+ RB- l
l__________________________l

EDIT, that should be bigger spaces, but the I's are representing bridges between the A and B setups

[Big Daddy]

Originally Posted by JJJMan

An additional question regarding this topic.

could i technically bridge the A+ and A- with B+ and B- of the Left and Right Channels? would it be a moot point putting them together or would i actually use both channels to push to the front speakers?

Additioanlly, could i use front A as highs and front B as Low's for Bi-wiring, or am i reaching a bit too far?

visual:

___________________________
l LA+ LA- l
l I I l
l LB+ LB- l
l l
l RA+ RA- l
l I I l
l RB+ RB- l
l__________________________l

EDIT, that should be bigger spaces, but the I's are representing bridges between the A and B setups

I am not sure I fully understand your question, but I do my best to explain bridging.

Bridging refers to combining two channels of an amplifier into one with twice the voltage. A two channel amp can be bridged to one channel, and a four channel amp into two channels. Bridging the channels increases the power output. An amplifier is usually bridged to combine two channels to power one speaker/subwoofer, or to combine four channels into powering two speakers/subwoofers.

It is common to bridge the power amplifier to increase the power available and generate more output from the sound system. This may be appropriate with a passive subwoofer. However, if you are dealing with full range speakers, it may be more appropriate to bi-amp them.

Bridgeable amplifiers are designed with an inverted channel for bridging purposes. The inverted channel produces voltage that is generated at the opposite polarity of the un-bridged channel.

Sometimes your amp will have a diagram for bridging. For example, look at the far right of the following 4-channel amplifier for bridging diagram.

If your amp is not able to bridge, you may still be able to do it with a DIY bridging adapter, but Before you attempt to bridge an amplifier, there are certain things you must keep in mind. Only bridge an amplifier that can handle the increased power load. Do not bridge an amp that will be unstable at the bridged load.

To understand how to bridge an amplifier that is not bridgeable, read these articles.


http://sound.westhost.com/project20.htm
http://sound.westhost.com/project14.htm
http://www.yamaha.com/yamahavgn/CDA/...402340,00.html

Bridging an amplifier produces twice the voltage and four times the power as it would in an un-bridged status. As an example, consider a 50 Watt per channel amplifier into 8 Ohms. This amplifier requires a signal voltage of 20 Volts RMS per channel to generate 50 watts per channel:

P = V^2 / R = (20)^2 / 8 = 400 / 8 = 50 Watts

The same amplifier into 4 Ohms will deliver close to 100W - provided the power supply can remain stable under the load.

If the two-channel amplifier is bridged into a single channel, the 8 Ohm loudspeaker now sees double the voltage. Using the formula above, we get:

P = V^2 / R = (40)^2 / 8 = 1600 / 8 = 200 Watts

[JJJMan]

oh, ok, thank you BigDaddy, i see what you're saying now, i've bridged a 2 channel amp into a single sub before, just forgot how to do it.

so what i'm wanting to do, is take the RightFrontA+ and the RightFrontB- to sent to the right speaker to get the wattage from both A and B channels, same with LeftFrontA+ and LeftFrontB-.

In my head what im saying makes perfect sense haha.