New pearl layout with MC

[cviller]

After some good results with my pearl layout and a bunch of feature requests/ideas, mostly from steenoe, I have decided to make the board bigger.

The new design will be based on my old layout from here:
(Pearl layout - how to organise things to avoid noise)

New feature list:
- Pearl preamp by Wayne
- MC input (see attachment and The Analogue Addicts Phono Preamplifier 2006 Edition)
- 9V supply for MC (lm317 or mosfet regulated?)
- Flexible capacitor footprints for riaa part (5,7.5,10,12 and 15mm pin spacing)
- Parallel capacitors for C10,C11 and C13 (exotic capacitors are sometimes hard to get in the large values need for pearl)
- Suitable for home etching - I can make a fab version later.

The board will be approximately 180x110mm (for each channel).

I would like to get some input (ideas, comments, additions) before I go ahead. The feature list is not closed!

[steenoe]

Sounds like that will be a very nice layout

- 9V supply for MC (lm317 or mosfet regulated?)

I suggest to tap the excisting supply just after C15 and add another mosfetreg to bring the voltage down to around 14 volts, then duplicate the capacitance multiplier based around Q3 and make that bring down the voltage to 9V. That should hopefully be quiet enough. Another option would be to power the MC stage from a 9V battery.

Steen

[cviller]

Nice idea about the supply - I think battery should be optional.

What about adding a balanced output buffer? Would anyone appreciate that?

[spzzzzkt]

Yes please!!! Balanced outputs would be a very nice/worthwhile addition for those of us whom can't justify the cost of building a (x)ono

there was some discussion on the topic here:

A differential output PEARL... ...?

edit: and here:

The Pearl-X

but perhaps you have some better ideas ?


pj

[steenoe]

What about adding a balanced output buffer?

Yep, thanks a lot, generally.
Depends on how it would look like, though Do you have anything specific in mind?
Normally I have no concerns at all, letting my X-BosoZ do the conversion
BTW I wrote partly some; not usefull suggestions about the reg supply for the simple French MC headamp supply! The capacitance multiplier will not bring the voltage down that much. The initial reg has to take it all the way down to nearly 9V I agree about the battery supply being optional, indeed. What about implementing a MC-frontend with more suitable supply voltage?
Aleph ONO would be the obvious choice, but with some more parts?

Steen

[steenoe]

Aleph ONO would be the obvious choice, but with some more parts?

If Mr. Pass accepts and give his permission ofcourse Glad I caught that one!

Steen

[cviller]

I would prefer to keep it more simple than the ONO.
To me, something like
http://www.diyaudio.com/forums/showt...245#post566245
would be the best option, but the gain must be adjusted and I think the number of jfets needs to be increased too. It would be nice to have proper line level on the output.

[Buhl]

Hello Cviller

I think its a nice and natural expansion of the things people have been working on in here - especially promitheus' work with the ono mcstage - I have build a couple of them for my self and some friends, and that stage sounds really awsome (in the good way)!!! - low noise, "black" background, no feeling of coloration, and very, very dynamic.... (of course some migth say, cause its taken direct from the ono....hehe)

If you could incorporate theese two circuits on one pcb, I think that would be nice - but I dont know if the ono MCstage is to complicated compared to what you have in mind ?

The gain of the Ono MCstage is however, plentyfull - I feel the 30 dB is way enough, 20 dB could do with most cartrdiges I think, so maby you can spare some of the macthed jfets ??

About the 9-volt battery, well, I used it in the beginning on my pearl, and on a friends pearl to - but the battery only lasted a month or so (continious operation), so I changed them to a zener, and none of us could hear any difference. I fact, the only tweak we have tried, that made a difference, was upgrading the external PSU to 80000uF(like the ono) and including a couple of extra CRC's - that seemed to lower the noisefloor a bit, but not much, but made it sound powerfull in a way thats hard to dsescribe....

Happy work - Im exited to see how it turns out !

Cheers !
Hans

[steenoe]

To me, something like

That looks pretty nice, for balanced out. I think Hans's suggestions about a "downscaled" ONO MC is pretty good. It would make things easier if it could be powered from the Pearls psu, more or less directly. An additonal capacitance multiplier would probably be in order to lower the noise as much as possible. BTW. Hans, the 9V battery was for powering the simple French MC stage specifically, since it uses 9V.

Steen

[cviller]

I wouldn't mind adding ono mc preamp instead - I think I can squeeze it in somewhere, but the boards might get bigger then. And the cost of components will increase too.