Folks:
I'm a newbie, so please go easy on me. Any answers to my question should be written with a knucklehead in mind.
I will start building a two chassis Pass Labs Aleph P preamp in a few weeks or so, once the parts start arriving. The preamp's rectifiers will be in the power supply chassis and two pairs of 16 gauge twisted pair will carry the DC voltage to the preamp chassis. My plan was to run those two pairs of wire inside some 3/8" braided copper sleeving that I have on hand. The preamp will include a remote control system (either Dantimax or the eagerly anticipated Twisted Pear Audio offering), and that will necessitate a second transformer in the power supply chassis.
Both remote control systems rectify AC on a PCB that will be in the preamp chassis. That means that there will be AC in addition to the DC running through the umbilical cable. I have two questions:
1. Will the AC line interfere with the DC lines in the umbilical? If so, can you recommend something to minimize the interference?
2. Should I consider a pi filter for the DC lines once they enter the preamp chassis? If so, how do I calculate the appropriate values for the resistor and capacitors?
Sorry for the basic inquiry; I'm trying to learn, but every audio project I try is incrementally more complex than the last, so there are always new questions.
Thank you,
Scott
I'm a newbie, so please go easy on me. Any answers to my question should be written with a knucklehead in mind.
I will start building a two chassis Pass Labs Aleph P preamp in a few weeks or so, once the parts start arriving. The preamp's rectifiers will be in the power supply chassis and two pairs of 16 gauge twisted pair will carry the DC voltage to the preamp chassis. My plan was to run those two pairs of wire inside some 3/8" braided copper sleeving that I have on hand. The preamp will include a remote control system (either Dantimax or the eagerly anticipated Twisted Pear Audio offering), and that will necessitate a second transformer in the power supply chassis.
Both remote control systems rectify AC on a PCB that will be in the preamp chassis. That means that there will be AC in addition to the DC running through the umbilical cable. I have two questions:
1. Will the AC line interfere with the DC lines in the umbilical? If so, can you recommend something to minimize the interference?
2. Should I consider a pi filter for the DC lines once they enter the preamp chassis? If so, how do I calculate the appropriate values for the resistor and capacitors?
Sorry for the basic inquiry; I'm trying to learn, but every audio project I try is incrementally more complex than the last, so there are always new questions.
Thank you,
Scott
mpmarino:
My first question was "should I be worried?"
The second question was "will a pi filter help?"
You're right, I could rectify the power for the remote control system in the power supply chassis. But I'm trying to understand if that is beneficial, or if there are other things I should consider. My goal is to learn where real issues exist and deal with them, and ignore concerns that are baseless.
Regards,
Scott
My first question was "should I be worried?"
The second question was "will a pi filter help?"
You're right, I could rectify the power for the remote control system in the power supply chassis. But I'm trying to understand if that is beneficial, or if there are other things I should consider. My goal is to learn where real issues exist and deal with them, and ignore concerns that are baseless.
Regards,
Scott
1) I think it would depend on a few variables. Is your AC separately and well shielded from the DC line within the cable? Amplitude of DC? ???? I would worry because I don't think you know what will happen. Personally I'd just pre regulate it to DC <or> you could just bring a wall wart directly to the pre for the aux circuits.
2) couldn't hurt I guess, but do you need it??? Did Nelson?
2) couldn't hurt I guess, but do you need it??? Did Nelson?
Hi,
the main charging pulses in the transformer secondary windings run through the rectifer to the smoothing caps and back through the rectifier to the other end of the secondary.
This route should be short and compact and lowish resistance.
This demands that the first stage of smoothing MUST be done local to the transformer.
Then distribute the roughly smoothed DC to the amplifier.
At the amplifier the supply rails expect to see a low impedance to get stable performance. This demands local decoupling.
This can be met using second stage smoothing. I think this second stage has more effect on sound quality and thus prefers to have good quality caps used for local decoupling. You may also want to look up RC snubbers and come back with further questions on how to implement them at the amplifier end. This also applies to your preamp, (it's a low current power amplifier and follows the same rules).
BTW,
first stage smoothing and the resistance in the umbilical and second stage smoothing are a Pi filter. Just make sure the PI filter is allowed to operate correctly by minimising the resistance of the zero volt line in the umbilical.
the main charging pulses in the transformer secondary windings run through the rectifer to the smoothing caps and back through the rectifier to the other end of the secondary.
This route should be short and compact and lowish resistance.
This demands that the first stage of smoothing MUST be done local to the transformer.
Then distribute the roughly smoothed DC to the amplifier.
At the amplifier the supply rails expect to see a low impedance to get stable performance. This demands local decoupling.
This can be met using second stage smoothing. I think this second stage has more effect on sound quality and thus prefers to have good quality caps used for local decoupling. You may also want to look up RC snubbers and come back with further questions on how to implement them at the amplifier end. This also applies to your preamp, (it's a low current power amplifier and follows the same rules).
BTW,
first stage smoothing and the resistance in the umbilical and second stage smoothing are a Pi filter. Just make sure the PI filter is allowed to operate correctly by minimising the resistance of the zero volt line in the umbilical.
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