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In Reply to: RE: How important is the bypass resistor on a stepped attenuator posted by airtime on August 11, 2014 at 06:26:21
I am not sure what you want to know. So far as I know, what most people call a "shunt attenuator" consists of a discrete single value resistor in series with the signal, and a variable resistance (which can be implemented in many ways, with a plastic pot or discrete resistors) to ground, aka the shunt or bypass resistance. Is that what you have in mind, in your first sentence?
And then it seems you want to compare that to a stepped attenuator. Of those, there are two types "series" and "ladder". The ladder type is superior to the series type in most ways, but ladder attenuators require a lot of resistors and take up more space. Which did you have in mind?
In my one experience, a shunt attenuator easily outperformed a series type attenuator, in the same application, but in designing a shunt attenuator you have to account for the fact that neither the input nor the output impedance is a constant.
Follow Ups:
"shunt attenuator" consists of a discrete single value resistor in series with the signal, and a variable resistance (which can be implemented in many ways, with a plastic pot or discrete resistors) to ground, aka the shunt or bypass resistance. Is that what you have in mind, in your first sentence?Yes, sorry for the poor discription. A fixed value discrete resistor in line with the signal and a variable shunt resistor. This is just a test project for now. I'm happy with the volume around 38-40db on the chart listed in the FIFTH post down
I have to read up more on the differences between series and ladder. I'll see if I can find the table posted in I believe audiokarmas DIY group.
charles
Edits: 08/11/14
"I'm happy with the volume around 38-40db ..."
Wow, you have a lot of gain there!
Have you ever though about eliminating some electronic gain stages to get the over all gain structure of your system closer to what you need?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
This is a Marantz NA7004 streaming player, aka DAC, feeding directly into the back of the power amp.
I'm simply putting a "volume control" between the two. No preamp, only a source, cablein, volume control,cable out and amp.
I think you need to be especially cognizant of the impedance matching, which is a bit tricky with a shunt attenuator, but I am sure you can do it.
OK, I guess there's not much else you can do.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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