The Phonoclone and VSPS PCB Help Desk

[rjm]

The X-reg schematic is a generic example of the circuit. Resistance values are adjusted depending on the input voltage and the desired output voltage.

If you want to combine the X-reg and VSPS, this has been done already and is called the VSPS300. The circuit schematic, board layout, and parts list are all available here.

You can put the power supply together with the VSPS or separately. Separately is recommended for novice builders, while metal cases are recommended for both power supply and VSPS.

[Stabby]

Thank you. The VSPS300 schematic is very helpful, didn't know it was included in the file.

I prefer building the VSPS from scratch on my own. I will use perf boards with a line pattern, drawing my own design and cutting the tracks where needed. I'll be sure to do a lot of testing (also to make sure the tracks I cut are really cut). Doing all this will give me a ton of experience, not to forget the satisfaction afterwards!

Still, if I were to order the PCB's for the VSPS 300 (without parts), can I pay through bank transfer?

[rjm]

Due to the high bank fees involved otherwise, I only accept Paypal payments.

"Doing all this will give me a ton of experience, not to forget the satisfaction afterwards!"

The satisfaction dividend depends on whether you ever get it working properly, though. Just sayin'.

[ahaja]

Here is my latest variation. Dual mono.

Wave files (44.1kHz - cd quallity):
MM section - Free File Hosting Made Simple - MediaFire
MC LO section - Free File Hosting Made Simple - MediaFire

K

[rjm]

Hi ahaja,

What modifications do the latest version of yours have?

/R

[ahaja]

Full dual mono.

Advanced power supply:
2 stage LM317/LM337 in series: one on pcb psu, second on pcb pre. After that finesse circuit.

MC:
- lowered R values and increased C values in RIAA section to values used in MM section. There is less gain, but sufficient.
- I stage feeds also IN+ of II stage through 2k2;
- from II stage IN+ 10uF and 232k parallel go to ground
- no cap on output
- variable gain in I stage - I like this because its useful.

MM:
- power supply like in MC section
- 12 positions dip switch for R load - dozens of possible settings from 1k to 100k
- 4 positions dip switch to set the C loading - from 0 ... 389pF
- variable gain of course ;-)
It may be used for MM and for MC HO cartridges, no matter from what producer.

Layout:
all grounds (psu and signal) comes to one point on each pre pcb.
Grounds on pcb psu are separated (for each rail) and meets together on pre pcb.

Sounds in my opinion very good ... like in wave files ;-)
Performance limits only turntable (tonearm, bearing, internal wires) and cartridge.
Cartridges used for recording:
MM - 2M Black
MC - SPU Naked

Regards Krzysztof

Ps. More pictures: https://picasaweb.google.com/1154538...762/NUDAPHONO#

[rjm]

Certainly DIP switches for various input configurations is a welcome addition and makes the circuit considerably more user-friendly, especially if one is of the habit to change cartridges regularly.

Originally Posted by ahaja

Advanced power supply:
2 stage LM317/LM337 in series: one on pcb psu, second on pcb pre.

You are the second person today I've corresponded with who is apparently convinced that adding LM317/LM337 regulators to a circuit improves it, and adding more LM317/LM337 to the circuit improves it further.

This is simply not the case.

Voltage regulators reduce noise within their passband as 1/G but add their own broadband noise X to the output. LM317 have a passband of about 2 kHz, which means they are great for reducing 120 Hz ripple and the higher order harmonics of it, but they spew out noise over the whole audio spectrum in return.

(Attach an LM317 to a DC blocking high pass filter and connect the output to your preamp and give it a listen. Or look at the 0-100 kHz FFT. Either way it isn't pretty.)

Op amps, such as those used in the phonoclone/VSPS are great at preventing power line ripple on the power pins from getting to the output. The PSRR is well in excess of 100 dB. They are quite poor at preventing high frequency audible line noise on the power pins from getting to the output, however. By 20 kHz, the power line noise is pretty much direct coupled to the output.

Adding a second LM317 in series does not reduce ripple (any residual component after the first LM317 can easily be absorbed by the op amps to below the output noise threshold of the op amp itself) but adds another 3dB of audio band noise to the power rail.

/R

[CxTurbo]

Has anyone ever installed a switch or variable resistors in the appropriate locations to accomodate any of the popular MM catridges (4mv,5mv and 5.5mv)? I was thinking it would be a nice option instead of having to adjust resistors based on future cartridge upgrades.

[rjm]

That's exactly what ahaja is doing above with his DIP array.

[CxTurbo]

Thanks RJM.

I was looking at his solution and figured since I was using your VSPS300 boards that maybe I could get other ideas on an off board solution.

I suppose Ahaja's idea could be implemented via dip switches on perf boards for each of the resistor and the cap locations. I am personaly thinking it might get a tad messy. Any thoughts on that?