Pearl2 Phono

[omishra]

:clapping: As usual a clean and nice build Om.

Are those shielded wires you are using for the power supply in the phono box?

Thanks Swapnil, yes those are shielded wires. I did not had anything handy. Though it was overkill and unwarranted still I used it.

 

[jls001]

My build completed:

Awesome build!

 

[Hiten]

As always nice work Om.
Regards

 

[sachu888]

Parts ordered for two members.It could take 15 days to receive all required parts.

Regards,
Sachin

 

[grubyhalo]

Nice build, do you foresee any benefits if you go for a regulated PS?

 

[omishra]

Nice build, do you foresee any benefits if you go for a regulated PS?

IMO, not in audible range. Because you can see there is capacitance multiplier in +ve rail. That makes first stage very quite and constant current source in each rail makes input and output stages stable. Power is filtered with bulk caps and CRC filter. So in conjuction to all, not so respected on board 7824/7924 linear regulator too work nicely.

Still I would have liked to put 317/337 kind of linear or shunt regulator after bypassing on board regulators. But that seems unwarranted and personal preference. Wayne has designed this keeping very simple.

 

[grubyhalo]

I see. Thank you!

 

[jls001]

On the Pearl 2, is there facility for adjusting impedance loading for different types of cartridges, and is there a way to change gain?

 

[omishra]

Yes, there is R14, default 1K. Reducing it to 680, 400 and 300 will increase gain. Other way is using R15, default jumper 0 ohm. Increase is by step of 1K will increase gain. Either way is possible.

Cart loading has mostly effect on MM cart only and tht is default 47.5K. There is provision to add parallel resistance in position R*, don't remember number now.

 

[jls001]

Thanks, Om.
My sudden worry was because I need a phono stage that does a better job - a much better job - than the phono stages that I have, for my Decca London Super Gold MI cartridge. So I need a means of bringing down the gain to somewhere like 40-46 dB, impedance loading of 47 kOhms (or thereabouts).

Also, I forgot to ask - does Pearl 2 have a means to change capacitive loading?

 

[omishra]

Yes, there is default 100pF marking near input on PCB. It is assumed that total capacitance of wire from cart till PCB is 125-150pF. If you could measure then good. And add required capacitance (any of 100, 120 or 150pF) in place of 100pF. I myself using 150pF now to make total capacitance 250pF for shure m97xe. Denon DL-110 is immune to loading, so same loading is working for it too.

 

[grubyhalo]

I have a silly question to ask. Could the Pearl 2 drive a power-amp through just a volume pot instead of a buffer or a pre in-between? Any pros/cons or possible issues to look out for?

 

[omishra]

I have a silly question to ask. Could the Pearl 2 drive a power-amp through just a volume pot instead of a buffer or a pre in-between? Any pros/cons or possible issues to look out for?

Yes, it's line level output. Default 57dB gain. For LOMC you need either SUT or ramp up volume level in absence of SUT. For denon 103 which is LOMC, without SUT we listen loud at 2 o'clock but with SUT its 11 o'clock for same audio level.

 

[grubyhalo]

Thank you.

 

[gurubhai]

Hi guys,

I recently recently purchased a Technics SL-10 which has a LOMC MC-310 cartridge.
I am interested in a set of Perl2 boards if anyone can spare them or may be start a new group buy if more members are interested.

 

[bhaskarcan]

GM to all,

Here's my Pearl2 built. As usual hips of thanks to Om for his excellent advice, support n explanations. Already lots have been told about this phono stage in this thread and they all stand true for me also. I only want to add few points here:

1. This is a very advanced & sensitive design. Everything matters i.e. quality of components, cartridge cap loading, gain selection resistor(system specific), RIAA adjusting cap........everything. Hence it's not plug n play. Adjustments are required to match one's system perfectly.

2. Vocal/mid range is very forward. So suits very well with Indian type of music.

3. Excellent bass reproduction with option to strengthen lower freq(not tried).

4. Overall if somebody wants his SS system to sound like a Tube one, go for this.

Brgds,

Bhaskar

 

[omishra]

Nice build!:clapping: Started with CNC now into pass lab designs.

Thanks for your kind words.

But please rectify the wiring layout.
1. Input and output should never go adjacent and parallel any point
2. By rotating the PCB layout you can make input of JFets to RCA phono input sockets at rear side of box.
3. Make output wires travel over the on-board PS section and then reach to output RCA. It should be neither over the 4X jFets of input nor parallel input wires except near RCA.

 

[bhaskarcan]

................

But please rectify the wiring layout.
1. Input and output should never go adjacent and parallel any point
2. By rotating the PCB layout you can make input of JFets to RCA phono input sockets at rear side of box.
3. Make output wires travel over the on-board PS section and then reach to output RCA. It should be neither over the 4X jFets of input nor parallel input wires except near RCA.

Thanks Om. I'll make the changes.

 

[jls001]

I started my Pearl II build last evening.

Edit: forked here to avoid cluttering this thread. Thanks.

 

[omishra]

Done my pearl-2 within new box and some letters on wooden faceplate.