Maybe not critical, but would it still matter?
Is this an issue since we are using an AC coupling output cap?
I do not hear difference with or without it..
It is not same to have 500mV and 5V offset..
Hi Walt,
The usual configuration as a unity gain buffer "preamplifier" is a volume pot, followed by a coupling cap, followed by an optional RC filter, followed an input resistor, followed by the bboard.
Ideally the pot should be 10k or 20k, but 50k or even 100k is okay as long as you don't mind a little higher than normal output offset voltage.
Email me and I can send you the example setup.
Richard
@dimkasta
"It is not same to have 500mV and 5V offset.." Vulejov is as usual being efficient in his choice of words. It is correct: coupling cap saves you from damaging connected components, but the offset approaches the voltage rails you quickly run out of headroom. Also, yes .. or rather no... the value of the R3 is not so important that choosing 1k or 3k will make much difference.
"It is not same to have 500mV and 5V offset.." Vulejov is as usual being efficient in his choice of words. It is correct: coupling cap saves you from damaging connected components, but the offset approaches the voltage rails you quickly run out of headroom. Also, yes .. or rather no... the value of the R3 is not so important that choosing 1k or 3k will make much difference.
A couple of notes about the X-reg.
A voltage regulator is a DC amplifier: you feed it a clean reference signal, it puts a multiple of that on its output, and the circuit does its best to ignore variations/noise on its power rails (the regulator "input").
There is no perfectly clean reference signal, and any dirt here is amplified directly to the output ... so the idea is to make sure that the reference contributes less noise than what is seeping through from the input anyway, or generated by the amplifier itself. The latter is somewhat influenced by the impedance of the reference, so a clean but very high impedance reference is not ideal, either.
Rather than a zener or filtered zener, the X-reg uses RC filters to generate the reference. Since it is completely passive it is quieter than a Zener, but the penalty is the reference is a fixed fraction of the input voltage, not an absolute voltage like 6.3 V or whatever. At very high frequencies (and very low frequencies) it will have a higher impedance than a Zener too.
So with the X-reg, if your AC voltage drops 10%, the Xreg output will drop 10% too. Over a timeframe of several seconds or more though, so its not like this can add anything audible. Think of it as acting like an unregulated supply in this aspect, but a regulated supply so far as the noise level is concerned.
It is proper to call the X-reg a voltage stabilizer (sometimes "capacitance multiplier"). The web page keeps this term and indeed I tried this at first but people kept looking at me funny so I've lapsed to calling it a regulator more often than not. It is, anyway, sort of...
A voltage regulator is a DC amplifier: you feed it a clean reference signal, it puts a multiple of that on its output, and the circuit does its best to ignore variations/noise on its power rails (the regulator "input").
There is no perfectly clean reference signal, and any dirt here is amplified directly to the output ... so the idea is to make sure that the reference contributes less noise than what is seeping through from the input anyway, or generated by the amplifier itself. The latter is somewhat influenced by the impedance of the reference, so a clean but very high impedance reference is not ideal, either.
Rather than a zener or filtered zener, the X-reg uses RC filters to generate the reference. Since it is completely passive it is quieter than a Zener, but the penalty is the reference is a fixed fraction of the input voltage, not an absolute voltage like 6.3 V or whatever. At very high frequencies (and very low frequencies) it will have a higher impedance than a Zener too.
So with the X-reg, if your AC voltage drops 10%, the Xreg output will drop 10% too. Over a timeframe of several seconds or more though, so its not like this can add anything audible. Think of it as acting like an unregulated supply in this aspect, but a regulated supply so far as the noise level is concerned.
It is proper to call the X-reg a voltage stabilizer (sometimes "capacitance multiplier"). The web page keeps this term and indeed I tried this at first but people kept looking at me funny so I've lapsed to calling it a regulator more often than not. It is, anyway, sort of...
G'day all, I'm doing some investigations into the VSPS circuit and I wonder if there is a simple way of defeating and/or reversing the Allen Wright 50 KHz feature.
I believe that this might have been discussed before but I can't find and reference to it. It might have been as simple as shorting out one of the resistors. Any comments? Regards, Felix.
I believe that this might have been discussed before but I can't find and reference to it. It might have been as simple as shorting out one of the resistors. Any comments? Regards, Felix.
Shorting over R3 temporarily will help you discover if that's where the problem lies.
The other option to try easily is reduce the load resistor R1 to 10k or so. (leave the 47k resistor in place, just put an extra resistor in parallel, across the RCA jack) Sometimes this can help suppress high frequency resonances between your cartridge and the cable capacitance.
The other option to try easily is reduce the load resistor R1 to 10k or so. (leave the 47k resistor in place, just put an extra resistor in parallel, across the RCA jack) Sometimes this can help suppress high frequency resonances between your cartridge and the cable capacitance.
Hello!
I am building a VSPS and I have a question about wiring its ground.
The construction guide suggest a separated power supply, and the VSPS ground is therefore only connected to its own chassis and the power supply ground.
But I am building my VSPS with its power supply in the same case, for practicality.
I connected the chassis to earth, but I wonder if I should connect PCB (and thus turntable) ground to the chassis, or should I leave it just connected to the power supply's gnd, in which case I need to use an isolated terminal for TT ground?
Attached is a view of the work in progress. Wiring so far has been tested, voltages checked ok, at +13 and -13 volts from the rectifiers "output".
Here https://kiye.wordpress.com/tag/v-s-p-s/ is an example of all-in-one VSPS with chassis and pcb gnd all connected to earth, but I don't know if it is good pratice.
Thanks in advance!
I am building a VSPS and I have a question about wiring its ground.
The construction guide suggest a separated power supply, and the VSPS ground is therefore only connected to its own chassis and the power supply ground.
But I am building my VSPS with its power supply in the same case, for practicality.
I connected the chassis to earth, but I wonder if I should connect PCB (and thus turntable) ground to the chassis, or should I leave it just connected to the power supply's gnd, in which case I need to use an isolated terminal for TT ground?
Attached is a view of the work in progress. Wiring so far has been tested, voltages checked ok, at +13 and -13 volts from the rectifiers "output".
Here https://kiye.wordpress.com/tag/v-s-p-s/ is an example of all-in-one VSPS with chassis and pcb gnd all connected to earth, but I don't know if it is good pratice.
Thanks in advance!
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It looks fine to me.
May I suggest insulating the third tab on the power switch? If it is a normally closed switch that will be a live terminal when the switch is off.