6x ladder attenuator on active system

aaronboumans · 21st February 2005, 08:54 PM

I want to use a six-channel ladder attenuator on my active system. The attenuator is between active filter (opamp output) and different Aleph amps. The problem is that I use an Aleph5 for low freq. and two Aleph 3's for mid and high freq. Trouble is that the input impedance of the 5 and 3 are not the same; 10k and 23k. This will affect my attenuator so that if I would use the same resistor for all freq's the attenuation will not be the same due to the parallel input impedance. Offcourse I could use and extra buffer stage between attenuator and Alephs but I dont like the extra opamp.
My question is; if I would use the standard calculations of a 'ladder attenuator with grounding resistor'
http://www.platenspeler.com/backgrou...#example_l12bn
can I 'see' the grounding resistor as being the input impedance and calculate the different resistors according the amp used so that I will get the same attenuation on all steps and all freq's???

aaronboumans · 24th February 2005, 08:56 AM

I have decided to put in the extra opamp because the problem will be to complex to solve with simple calculation. And it will be easier adaptable to other situations.

I am using the opa2134pa
any way to better them or easy replaced with better dip?

21st February 2005, 08:54 PM	#1
aaronboumans diyAudio Member Join Date: Feb 2003 Location: deventer	6x ladder attenuator on active system I want to use a six-channel ladder attenuator on my active system. The attenuator is between active filter (opamp output) and different Aleph amps. The problem is that I use an Aleph5 for low freq. and two Aleph 3's for mid and high freq. Trouble is that the input impedance of the 5 and 3 are not the same; 10k and 23k. This will affect my attenuator so that if I would use the same resistor for all freq's the attenuation will not be the same due to the parallel input impedance. Offcourse I could use and extra buffer stage between attenuator and Alephs but I dont like the extra opamp. My question is; if I would use the standard calculations of a 'ladder attenuator with grounding resistor' http://www.platenspeler.com/backgrou...#example_l12bn can I 'see' the grounding resistor as being the input impedance and calculate the different resistors according the amp used so that I will get the same attenuation on all steps and all freq's???

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24th February 2005, 08:56 AM	#2
aaronboumans diyAudio Member Join Date: Feb 2003 Location: deventer	I have decided to put in the extra opamp because the problem will be to complex to solve with simple calculation. And it will be easier adaptable to other situations. I am using the opa2134pa any way to better them or easy replaced with better dip?

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