The Phonoclone and VSPS PCB Help Desk

[rjm]

But looking at this circuit it looks to have infinate impedance. Not zero. What is zero is the loading.

Wrong on both counts I'm afraid. The input impedance is zero, and though it is a virtual ground rather than a literal short circuit, it behaves the same way. The loading is not zero. Its close to it, equal precisely to the value of your cartridge impedance.

At RF, though, I agree that this can all be thrown out the window.

I have vague memories of having a similar experience with hum in some commercial audio gear that changed with the position of people in the room, as they occasionally attenuated the reception of RF signals.

Although ferrite beads can do unpleasant things to the sound, they might be useful to you, especially on the power supply wires.

/R

[brainspex]

Hallo together,

I finished the complete project of all three preamps and will post the results here. It is essential to know, that I didn't use the PCBs from RJM. I used own layouts, all sharing the same power supply layout of regulated 3*7 regulators. I post the pictures here for each preamp separately. Starting with the Phonoclone.

Regards, BSPX

[brainspex]

the VSPS - ultra ..

[brainspex]

.. and the VSPS standard ..

[brainspex]

.. and from outside - if someone is interested in. I think there is not too much information in the pictures because the preamps all share the same look - .

Some remarks to the configurations and sound qualities:

1. All Preamps were used with the same 130VA Power supply.
2. All Preamps use the same dual regulation of 3*7 at 12 V.
3. The Phonoclone uses OP27G, Elna Silmic as bypass, Wima as RIAA and black gate as decoupling.
4. The VSPS-ultra uses OP27E, Panasonic FC as bypass, Wima as RIAA and Mundorf as decoupling.
5. The VSPS-std uses MAX437G, Panasonic FC as bypass, Arcotronic as RIAA and generic components as decoupling.

There is a difference in sound quality, which is quite listenable and not subtle. In the above mentioned configurations the phonoclone beats them all, followed by the VSPS ultra and the VSPS standard. The difference between the ultra and the standard is not that much ! All preamps used the same power supply, so the impact of the power supply and regulation to the comparism is minimal. All preamps were run in for at least six hours. All amps used the same cartridge - a denon 103 for the moment.

I suppose, the BIG impact is the OP27G. I will plug and play and switch some other chips in the next weeks and reports the results.

Regards, BSPX

[Bas Horneman]

Great pictures..

A little sidenote..it really is not possible to compare the Phonoclone with the VSPS is it??..the phonoclone was virtually made for the DL103 while the VSPS was made for your typical MM cartridges.. But nevertheless it was interesting and great that you could do the comparison.

Regards,
Bas

[rjm]

Brainspex, working hard so I don't have to!

The VSPS can be used directly with low output MC cartridges if you change the loading, R1, to something appropriate and can turn up the volume of the preamp to compensate for the low gain. Not normally recommended.

The only fundamental reason the Phonoclone should sound better than the VSPS is the inverting vs. noninverting topology. The rest is layout, parts, and and other open variables.

As Bas says, though, the designs are not intended to compete with each other ... but rather serve separate niches.

A very interesting experiment, though.

/R

[brainspex]

Some remarks:

I pushed the gain of the VSPS standard to 50dB to compete with the ultra and the clone.

"Brainspex, working hard so I don't have to.." Yo, my wife asked already for the reason of 5 little silver shining boxes (2 supplies, 3 amps) in our living area. Me: "It is an experiment !" - smile

I would not see the Phonoclone as a DL103 dedicated design. I had used it already with a shelter 901 successfully, and I think it will match to all low output MC's from 0.1 mV to 0.6 mV.

PCB-Layout: It has an impact, yes. The VSPS-ultra and the VSPS-std got a new grounding layout (seen in the pics). This layout beats the phonoclone in radio interference, noise, hum etc. In fact the VSPS-ultra without the cartridge connected is death silent, as silent that you cant hear anything from the speakers even if the volume is at the right end, like switched off.

Regards, BSPX

[rjm]

The VSPS-ultra and the VSPS-std got a new grounding layout (seen in the pics).

I did notice that the regs part of the same board in the two VSPS designs, closer to the op-amp(s). However its difficult to see from the pictures what the ground routing actually is.

On a side note, the VSPS ultra should not be that much different from the VSPS from a noise standpoint, when something like the OP27 is used for both and the same cartridge is attached. It is, after all, the same circuit and while the input impedances are slightly different they are sufficiently low in both cases that they shouldn't affect the total noise much. (That's assuming R2 in the VSPS is below 1k)

/r

[brainspex]

This is the layout of the PCBs of the VSPS standard and VSPS ultra,
there is no suprise so far. It follows the ideas RJM made in this
forum too. The size is always a half standard Euro PCB
size. Schematics and Layout were made with EAGLE - a fine tool !

Hints: cable-bridges were made as resistors. Some values of resistors were changed later.

- Regards, BSPX