I've populated my VSPS dual mono boards and now am planning out the rest of the preamp.
Plan is to use this eBay switch powered by a separate 12V supply:
And then this stepped attenuator for volume.
And use the fully differential line stage from amb.org.
I have an old wooden record player enclosure to play with and will likely use aluminum sheet as a base for grounding and such.
Question for the help desk:
I'm planning on putting the volume control between the input selector and the line-stage. That follows best practice guidelines, yes?
Plan is to use this eBay switch powered by a separate 12V supply:
And then this stepped attenuator for volume.
And use the fully differential line stage from amb.org.
I have an old wooden record player enclosure to play with and will likely use aluminum sheet as a base for grounding and such.
Question for the help desk:
I'm planning on putting the volume control between the input selector and the line-stage. That follows best practice guidelines, yes?
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The volume attenuator can be in any of three locations.
A.) At the input
b.) After the active stage but before any final active stage.
c.) After all active stages.
a. prevents the active stages from being exposed to overload.
c. gives the lowest noise with the wanted signal to be fed to the Receiver.
b. requires some skill in avoiding the pitfalls of a & c.
If one uses a very low gain low noise active stage, or a no gain Buffer stage, then the noise of these active stages can be so low, that option a becomes viable for all partially active vol pots.
A.) At the input
b.) After the active stage but before any final active stage.
c.) After all active stages.
a. prevents the active stages from being exposed to overload.
c. gives the lowest noise with the wanted signal to be fed to the Receiver.
b. requires some skill in avoiding the pitfalls of a & c.
If one uses a very low gain low noise active stage, or a no gain Buffer stage, then the noise of these active stages can be so low, that option a becomes viable for all partially active vol pots.
Hi, I wonder about modification of the original circuit VSPS.
Adding a resistor 2k2 at the entrance, completely removes the residual humm I had.
Deteriorates in some other aspect of the circuit ?.
The addition of this resistance was in evidence as in other circuits I've seen (it is in the phono pre Rod).
Another point in the photo guide construction, the chassis ground circuit and is welded to zero volts of power supply connector. It can be done well?
Regards.
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Adding a resistor 2k2 at the entrance, completely removes the residual humm I had.
Deteriorates in some other aspect of the circuit ?.
The addition of this resistance was in evidence as in other circuits I've seen (it is in the phono pre Rod).
Another point in the photo guide construction, the chassis ground circuit and is welded to zero volts of power supply connector. It can be done well?
Regards.
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Hello, I found a new tool, a spectrograph, and see where the slight humm that is listening at maximum volume.
It is in 49.7hz.
If I can I upload the video.
Greetings and happy Christmas and New Year (for those who believe in it) to everyone who has supported my interventions and those who have helped me in my doubts.
But a forum is a community of friends.
https://youtu.be/jA_5igPTxL8
It is in 49.7hz.
If I can I upload the video.
Greetings and happy Christmas and New Year (for those who believe in it) to everyone who has supported my interventions and those who have helped me in my doubts.
But a forum is a community of friends.
https://youtu.be/jA_5igPTxL8
@ALPUY
This is "hum", pickup in the signal of the AC line frequency. In a phono stage it is quite common and there are many possible causes, from the power supply of the phono stage itself, the power supply/motor of the turntable, poor grounding layouts, nearby amplifiers, poor shielding of the phono stage or upstream, etc.
This is "hum", pickup in the signal of the AC line frequency. In a phono stage it is quite common and there are many possible causes, from the power supply of the phono stage itself, the power supply/motor of the turntable, poor grounding layouts, nearby amplifiers, poor shielding of the phono stage or upstream, etc.
Here is the picture of the interference.
Merry Christmas.
Merry Christmas.
An externally hosted image should be here but it was not working when we last tested it.
Bobio, the mains frequency is 50 Hz in Uruguay.
As for sources switched there in the same place as the audio system, the TV; the computer; Satellite Receiver.
In the rest of the house it is full of electronic devices with switching power supplies. from cell phone chargers to other tv and more.
Tendíaa to leave only online audio system, set it to maximum volume and go connecting other devices.
I'm going to do and story.
But I wonder how it is done to avoid interference by network because all the houses there today multiplicity of devices that may cause interference.
I have in the PSU phono stage EMI filter, but is seen to be insufficient.
Greetings and after story.
As for sources switched there in the same place as the audio system, the TV; the computer; Satellite Receiver.
In the rest of the house it is full of electronic devices with switching power supplies. from cell phone chargers to other tv and more.
Tendíaa to leave only online audio system, set it to maximum volume and go connecting other devices.
I'm going to do and story.
But I wonder how it is done to avoid interference by network because all the houses there today multiplicity of devices that may cause interference.
I have in the PSU phono stage EMI filter, but is seen to be insufficient.
Greetings and after story.
its difficult to get a phono stage completely quiet due to the nature of it, your amplifying a minute signal that is prone to outside interference from every direction right from the cartridge all the way to the output phono leads. if the noise is not detectable at normal listening levels then i would not stress out about it. as for it degrading the sound quality then its subjective, personally i would not worry about it. an EMI filter will only filter the AC mains going in and only to a degree. only thing you can do is try unplugging everything else from the mains till you find the source of the problem and try moving the phono stage to different positions as far away from other electrical items including your amplifier, this is why you will see a lot of phono stages sat on peoples floors.
Close coupled wire pairs for every connection. This reduces LOOP AREA and that attenuates the interference.
That includes the Mains wiring outside and inside the amplifier.
Transformer and rectifier and smoothing caps and PSU triplets and signal input and signal output and auxialiary supply/s Everything needs close coupled pairs for all the wires that connect modules together.
Any single wire that has a varying current through it, will emit interference.
Any single wire that starts life outside the box will bring the interference inside the box. You must attenuate at the box/enclosure wall/hole/termination.
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