isolation b/w NI DAC & 2KWatt power amplifier

[ASIM_BHATTI]

Hello

i am using NI DAC (PCI 6723) to drive QSC RMX 4050HD Power amplifier (PA) having input impedance of 10 kohm. I am generating 1-5KHz sinusoidal signals from my DAC.

1- I need some isolation & signal smoothing b/w DAC & 2kWatt PA.

2- Secondly, NI DAC has current limitation of 5mA/channel. I also desire to boost this capacity to say (10mA/channel) with some IC b/w DAC output & PA input.

Can any one kindly suggest some type of analog isolation IC/transformer which can do this job?

Thanks

Best Regards

asim

[johnsold]

asim,

You probably cannot do what you want with a transformer.  To increase the current level you would need to decrease the voltage by the reciprocal factor. So you need an amplifier.

Do you want to build your own or buy a package that you can just plug in?  How much isolation do you need (voltage)? Will the bandwidth requirement ever be greater than 1-5 kHz?

What do you mean by signal smoothing?

Lynn

[ASIM_BHATTI]

Dear

Thanks for reply.

Do you want to build your own or buy a package that you can just plug in?

I will prefer a  package that i can just plug in.

Will the bandwidth requirement ever be greater than 1-5 kHz?

 No, the bandwith will not exceede from 1-5KHz.

What do you mean by signal smoothing?

When i measure the output of DAC on oscilloscope, i see sine wave with discrete steps (staircase like output waveform) .when i got its FFT spectrum, i could see multiple hormonics in it. So i think there is need of low pass filteration (smoothing) at output of DAC.

How much isolation do you need (voltage)?

I just want to completely isolate (electricaly) my DAC system from high power amplifier (PA) system so that any transients on PA could not effect my DAC system.This means i have to completely isolate my DAC ground from PA ground.

Best Regards

asim

[johnsold]

asim,

NI makes some isolated devices (PCI-6230 series) but they have a 5 mA limit on the output current. They are also designed for 30 or 60 V isolation.  I do not know who makes isolated amplifiers with higher outputs.

All D/A devices will generate steps in the outputs. A higher resolution D/A converter will give smaller steps. A low pass filter will reduce the harmonic content. You do need to be carefule with the selection of the filters. At the low frequency end of your bandwidth several harmonics of any signal will be within the amplifier passband.  You may need to have several filters and select the appropriate one.  Use the highest sampling rate you can on the D/A converter as that will help move the interference out of the band.  Also, be careful if you choose digital filters as they are still discrete sampled data systems and could have the same problems as your D/A converter.

Lynn