Im having loads of fun with my budget Feeltech Fy6600 and Fy6800 Arb gens .
It occured to me that when you dial in a signal say in the milli volts region to test audio the units bit rate/dynamic range is severly limited
Like has been suggested in other posts, running your digital generator at full level ,then using an attenuator on the audio output is a good way to maximise signal quality . I remember Ian.T.B made a special attenuator for audio testing especially for this purpose but cant find the thread .
The sig gens are the usual 50 ohms output so I guess its a good plan to keep the attenuators to be able to opperate properly into that impedence . Something like five steps of ten db coarse adjusment and fine control in one db steps would be nice .
Of course Ive attended to other areas in order to allow sustained opperation of the unit at full power with more headroom ,new high power output op amps (THS3095 ,THS3491),powersupply upgraded ,+/- rail voltage raised etc.
I also note people recomending an output transformer in relation to testset outputs to prevent any chance of phantom power damaging the dc coupled out of the generator . What would be a good choice of transformer in this application ? I'd imagine mic input would be the lowest impedence you'd be expecting to drive with it , ballanced line level inputs at 20 k also . Could the attenuator be placed between the generator and the transformer ,say a smaller mu metal 1:1 10kohm to avoid core saturation due to the generators high output level?
Another suggestion someone made to improve the signal quality of a generator for single frequency distortion measurement was to include a low pass in the output in order to attenuate 2nd and 3rd harmonics etc .So, by scrubbing off a predefined number of db of output in a low pass filter can we improve on the theoretical limits set by the 14 bit dacs in the unit ?
Maybe a simple switchable low pass at a handfull of common test frequencies might work well here?
I have a couple of small die cast boxes , BNC connectors, some nice mini rotary switches 2x6ways etc ,I can patch in any one of a number of transformers as the need arises . 20V peak is quoted as maximum output from the generator ,into 50 ohms 10 volts is maximum . If anyone knows software that would allow me to calculate the resistance values ,impedence,number of steps and db loss that would be great ,Im aware there are also several different types of attenuation network which kind makes most sense for my application ? its a simple unbalanced signal ,but ladder ,pi etc , I'm aware of the different impedence charachteristics of the various types of attenuator ,but I cant clearly visualise which is best for the job
Thanks again,
It occured to me that when you dial in a signal say in the milli volts region to test audio the units bit rate/dynamic range is severly limited
Like has been suggested in other posts, running your digital generator at full level ,then using an attenuator on the audio output is a good way to maximise signal quality . I remember Ian.T.B made a special attenuator for audio testing especially for this purpose but cant find the thread .
The sig gens are the usual 50 ohms output so I guess its a good plan to keep the attenuators to be able to opperate properly into that impedence . Something like five steps of ten db coarse adjusment and fine control in one db steps would be nice .
Of course Ive attended to other areas in order to allow sustained opperation of the unit at full power with more headroom ,new high power output op amps (THS3095 ,THS3491),powersupply upgraded ,+/- rail voltage raised etc.
I also note people recomending an output transformer in relation to testset outputs to prevent any chance of phantom power damaging the dc coupled out of the generator . What would be a good choice of transformer in this application ? I'd imagine mic input would be the lowest impedence you'd be expecting to drive with it , ballanced line level inputs at 20 k also . Could the attenuator be placed between the generator and the transformer ,say a smaller mu metal 1:1 10kohm to avoid core saturation due to the generators high output level?
Another suggestion someone made to improve the signal quality of a generator for single frequency distortion measurement was to include a low pass in the output in order to attenuate 2nd and 3rd harmonics etc .So, by scrubbing off a predefined number of db of output in a low pass filter can we improve on the theoretical limits set by the 14 bit dacs in the unit ?
Maybe a simple switchable low pass at a handfull of common test frequencies might work well here?
I have a couple of small die cast boxes , BNC connectors, some nice mini rotary switches 2x6ways etc ,I can patch in any one of a number of transformers as the need arises . 20V peak is quoted as maximum output from the generator ,into 50 ohms 10 volts is maximum . If anyone knows software that would allow me to calculate the resistance values ,impedence,number of steps and db loss that would be great ,Im aware there are also several different types of attenuation network which kind makes most sense for my application ? its a simple unbalanced signal ,but ladder ,pi etc , I'm aware of the different impedence charachteristics of the various types of attenuator ,but I cant clearly visualise which is best for the job
Thanks again,