Hi all, I bought this DAC some time ago
Finished CS4398 + CS8416 USB DAC With R-core Transformer + case | eBay
it performs quite well but sometimes volume control is problematic (some software allows for control, some don't)
So I would like to add a stero pot to the output (unloaded output is 6.5vvpp)
Will an ordinary stero log pot (1M) be adequate?
Thanks
Finished CS4398 + CS8416 USB DAC With R-core Transformer + case | eBay
it performs quite well but sometimes volume control is problematic (some software allows for control, some don't)
So I would like to add a stero pot to the output (unloaded output is 6.5vvpp)
Will an ordinary stero log pot (1M) be adequate?
Thanks
There are two effects of inserting a high value resistive attenuator (pot.) directly to the DAC box output. One is a permanent reduction in the maximum output signal level, although this does not alter the system frequency response. The other would be the formation of an RC low pass filter in conjunction with the shunt capacitace of the interconnect cable and that of the amplifier input stage, which will alter the system frequency response. Whether either effect is of audible consequence depends on the relative impedances involved. The higher the pot. resistance, the greater those two effects will become.
The most obvious solution to those two effects is to use a relatively low resistance pot. However, even a 10K pot. could load the DAC output stage enough to raise the distortion profile of your DAC, especially higher order distortion products. Providing a high impedance to the DAC's output stage, while providing a low impedance to the interface shunt capacitance, is the area where inductive volume controls really have an advantage in the application you describe.
Bye the way, the effect of interconnect cable shunt capacitance can be eliminated by locating a resistive volume control pot. at the amplifier end of the interconnect. This would require mounting the pot. inside your amplifier chassis (in essence, changing it in to an integrated amplifier) rather than inside your DAC chassis.
The most obvious solution to those two effects is to use a relatively low resistance pot. However, even a 10K pot. could load the DAC output stage enough to raise the distortion profile of your DAC, especially higher order distortion products. Providing a high impedance to the DAC's output stage, while providing a low impedance to the interface shunt capacitance, is the area where inductive volume controls really have an advantage in the application you describe.
Bye the way, the effect of interconnect cable shunt capacitance can be eliminated by locating a resistive volume control pot. at the amplifier end of the interconnect. This would require mounting the pot. inside your amplifier chassis (in essence, changing it in to an integrated amplifier) rather than inside your DAC chassis.
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Thank you all for your replies. To achieve volume control and still be able to avoid the consequences Ken Newton described I added two switches on the back of the DAC which enable me to either use the 10k log stereo pot or bypass it completely. The two switches were used to avoid loops of any kind. When both are pointing "left" the output is directly connected to the board and shares no path to the POT, if turned right (pointing the knob) the opposite happens.
A correctly wired pot will not drop the maximum signal level by more than a trivial amount, unless the source has unusually high output impedance. Bypass switch not needed.
Ken's suggestion to put the pot at the receiving end of a long interconnect is worth following. Not necessary for a short interconnect.
Ken's suggestion to put the pot at the receiving end of a long interconnect is worth following. Not necessary for a short interconnect.
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