Bi Amp

[snodge]

Hi I am thinking about a bi amp set up using a 5881 wad for the top end and a Conrad Johnson mosfet for the bottom. I believe I will need a crossover. Can anyone offer some advice? Thanks David

[bikerhifinut]

The first thing that springs to mind is that you are using dissimilar power amps.
So, you really need to synchronise the gains so that for any given input voltage, the output power is the same for both amplifiers. The easiest way here is to put attenuators on the input of each amp and adjust on test. For this you need a signal generator and an oscilloscope or a meter that will accurately measure the voltage across a dummy load.
You could try adjusting by ear but it seems a bit hit and miss to me.
If your speakers are biwireable then no need to use separate crossovers, just disconnect the link wires on the terminals on the speakers. Their internal crossovers will take care of the rest.
I believe the preferable way of bi amping is to use a crossover on the inputs, this isnt trivial as various factors will have to be taken into account including the input resistances of the individual amps and so forth. Then you have to remove the crossover on your loudspeakers, this will create an issue in that the tweeter will be exposed to the full power of one amp and may need an attenuator to prevent it blowing. the internal crossover deals with this issue as part of its design.
And heres a thought for you, I'm not saying it won't work but using dissimilar amps will possibly cause a tonal distortion due to differing frequency response curves and other factors. I know there are speakers out there that use their own built in power amps for the bass units, Martin Logans spring to mind, but I think they have tone controls to tailor the bass response to suit the amplifier driving the electrostatic panels.
Sound like a can of worms? Sorry but that's my take on it and I'd generally try to use identical power amplifiers in a bi amp set up.

I have no doubt somebody on the forum has tried what you are thinking about so if I have got it wrong i will stand corrected.

A.

[snodge]

Sounds tricky, will stick with what I have many thanks David

[bikerhifinut]

You could just get a couple of stereo log pots and wire the inputs via them and try it.
A.

[davebms]

hello all,, as already stated if your speakers are bi wire, its not to
difficult, I made my pre amp dual out (Just linked the together) put a
pot in a box on the bass rca lead and adjusted until it sounded ok

had el84 on top, 100watt on the bottom (that may not be the best option but it worked)

dave

[snodge]

Hi thanks for the further input. My speakers are Klipsch Heresy 3's and can accommodate a bi-amp set up. Happy to continue to discuss this. Many thanks David

[bob orbell]

Hi all I have bi-amped with SS amps exactly the same amp to drive both bass and tweeter, and it was fantastic, but then I moved over to thermionic amps, driving in bi wired form, well, no contest, if you are hell bent on bi-amping, then use two identical amps. BOB