My preamp has one set of single ended, and one set of balanced outputs to connect to a power amp. I've recently bought a 5 channel power amp and I would like to use 4 channels to try out passive bi-amping.
My speakers have proper tri-wire inputs where each is separate from the other. I would probably wire the bass to one channel and the mid and treble to another. I have discussed converting my speakers to active with my manufacturer (PMC) who also make actively powered studio monitors. They've said I'd need an extremely good active crossover and a lot of testing and equipment to get it to sound as good as their built in passive. They also pointed out the drivers were not selected or intended to be actively powered i.e. I think their inductances may be different.
So I know the standard way to split each output from the preamp is to use a 'Y' cable that connects the single ended output in parallel to 2 power amp inputs. However this effectively doubles the load on the preamp by halving the inductance at its output (correct me if I'm wrong).
Another way I thought I could do it would be to split the balanced output. My idea would be to connect one power amp channel to the hot and ground pin, and the other between the cold and ground. Chassis ground would be left unconnected. As each signal is out-of-phase, I would wire one of the outputs of the amplifier to the speaker out-of-phase to correct this. Obviously the signal wouldn't be balanced but it does avoid having to wire anything in parallel.
I can't find anything at all about anyone trying this on the web. Does anyone know if it might be a good idea or am I just showing my lack of knowledge on the subject?!
My speakers have proper tri-wire inputs where each is separate from the other. I would probably wire the bass to one channel and the mid and treble to another. I have discussed converting my speakers to active with my manufacturer (PMC) who also make actively powered studio monitors. They've said I'd need an extremely good active crossover and a lot of testing and equipment to get it to sound as good as their built in passive. They also pointed out the drivers were not selected or intended to be actively powered i.e. I think their inductances may be different.
So I know the standard way to split each output from the preamp is to use a 'Y' cable that connects the single ended output in parallel to 2 power amp inputs. However this effectively doubles the load on the preamp by halving the inductance at its output (correct me if I'm wrong).
Another way I thought I could do it would be to split the balanced output. My idea would be to connect one power amp channel to the hot and ground pin, and the other between the cold and ground. Chassis ground would be left unconnected. As each signal is out-of-phase, I would wire one of the outputs of the amplifier to the speaker out-of-phase to correct this. Obviously the signal wouldn't be balanced but it does avoid having to wire anything in parallel.
I can't find anything at all about anyone trying this on the web. Does anyone know if it might be a good idea or am I just showing my lack of knowledge on the subject?!
The manufacturers would say that their system is going to work better than anyone elses'.
Using a 'Y' cable is probably good enough for what you want to acheive as the output impedance of your pre-amp should be a few KOhms and the input impedance of your power amps should be more than 18KOhms.
probably because they have spent quite a bit in R&D to get it right.
A balanced line out, is as it states, balanced but also floating with respect to ground so will not work as you suggest.
Using a 'Y' cable is probably good enough for what you want to acheive as the output impedance of your pre-amp should be a few KOhms and the input impedance of your power amps should be more than 18KOhms.
probably because they have spent quite a bit in R&D to get it right.
A balanced line out, is as it states, balanced but also floating with respect to ground so will not work as you suggest.
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Two channels of paralleled 10k inputs will present 5K to your source.
The paralleled capacitances of the two cables (and the RF attenuation at the inputs of your amps) will present doubled capacitance and that will draw doubled current charging the capacitance.
The current to drive the cable will probably be more than that required to drive the 5k
Your 47ohm source will easily drive the 5k. 3Vpk into 5kohms is just over 0.5mApk
Check the source current specification to see if it can drive the cable properly.
The paralleled capacitances of the two cables (and the RF attenuation at the inputs of your amps) will present doubled capacitance and that will draw doubled current charging the capacitance.
The current to drive the cable will probably be more than that required to drive the 5k
Your 47ohm source will easily drive the 5k. 3Vpk into 5kohms is just over 0.5mApk
Check the source current specification to see if it can drive the cable properly.
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The preamp manufacturer doesn't specify the current specification of the outputs.
However I was able to find this on the datasheet of chip used at the output stage:
I'm not sure if an additional output stage is used. There is certainly at least a passive component in the signal since the output resistance of the chip is 100 ohms, but the preamp manufacturer states the output as 47 ohms.
The total capacitance of the 2 cables per used per output will be less than 64 pF.
However I was able to find this on the datasheet of chip used at the output stage:
I'm not sure if an additional output stage is used. There is certainly at least a passive component in the signal since the output resistance of the chip is 100 ohms, but the preamp manufacturer states the output as 47 ohms.
The total capacitance of the 2 cables per used per output will be less than 64 pF.
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