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I would like to try, just as an experiment, using a variable resistor as the bypass shunt resistor for a set range I seem to like and use 90% of the time.
Thoughts?
Would it effect the sound quality I am gaining by using a discrete resistor, aka stepped attenuator?
charles
Follow Ups:
It tells you what to do when your amp gets too loud too fast
Edits: 08/14/14
I thought I might do something like this.
I think the end result is the same as what you are looking for: the volume control range is the range you use most often. There is no need for a 100k pot if you only use the "bottom" 50k, e.g. if your amp clips with 1V input from a 2V source.
Pretty much what I'm doing. Only a 240ohm resistor and 47k variable pot. But the same idea.
I was wondering if there was ANY effect on the sound?
thanks
charles
"I was wondering if there was ANY effect on the sound?"
In my example, it is possible that a high quality single 50k resistor could be slightly more transparent than one half the 100k pot; that's why I was considering it.
I do this in a tube preamp with a Texas Components TX2575 fixed resistor and a variable Silonex light dependent resistor(LDR) in the shunt position. By varying a 5V voltage across the LED of the LDR you can adjust the working range of the LDR to whatever you need to achieve your desired range of attenuation. This approach(see Lightspeed attenuator in DIY forum threads) easily surpassed a Shallco series attenuator.
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.
"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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