D.I.Y. "Duplex" 2sk369 jfet mm phono preamp - diyAudio
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Old 19th September 2006, 06:07 PM   #1
doggy is offline doggy  Canada
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Default D.I.Y. "Duplex" 2sk369 jfet mm phono preamp

Just wanted to present another option for a phono pre. It is a design by Carlos and can be seen at: diyhifi.org. It uses two 2sk369bl (or gr), one 2n1711, one bf393/side. I used 2sc1815 instead of bf393 due to sourcing problems.

It works well, and is low noise.

There are no pcb's or parts kits, but I did it ; if you can read a schematic, that should get you there.

I live in B.C. Canada, so all parts were sourced from Digikey, the 2sk369bl, 2sc1815 from B&D Enterprises, www.bdent.com, partsales@bdent.com.

The generic pcb came from RS(The Source), 11cmX 15cm. Aside from the design itself, which I take "0" credit for, sourcing the parts and part no.'s was a lot of work. This is where a kit shines!

If any one is interested, I have the digikey part no.'s that I used.

I did enquire regarding the Pass Pearl but decided to go with this one.

Cheers
doggy
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Old 22nd September 2006, 06:45 PM   #2
Ropie is offline Ropie  United Kingdom
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Nice implementation and good to see some battery powered phono stages for a change. I'm about to attempt RJM's MC Phonoclone but with a battery PSU.
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Old 22nd September 2006, 08:05 PM   #3
doggy is offline doggy  Canada
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Default battery power

I have used battery power before, with an opamp phono stage it can go weeks to months before needing recharging.

This discrete design uses more power; it calls for 2 12v 4amp sla in series for24v dc; I used 2 12v 7amp sla. There is also 2x 10,000uf filter cap.s, bypassed w/100uf at the battery pack.

cheers
Thor[doggy]
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Old 25th September 2006, 02:05 PM   #4
Ropie is offline Ropie  United Kingdom
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Default Re: battery power

Quote:
Originally posted by doggy This discrete design uses more power; it calls for 2 12v 4amp sla in series for24v dc; I used 2 12v 7amp sla. There is also 2x 10,000uf filter cap.s, bypassed w/100uf at the battery pack.
What benefits do the large filter caps provide? Do you have a schematic showing the battery circuit? - I'm having problems working out the grounding for mine.
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Old 25th September 2006, 04:37 PM   #5
doggy is offline doggy  Canada
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Default power supply

This battery supply is part of the "duplex" schematic. A thread is started on diyhifi.org which will give you all the details. This is a design by carlosfm which is also referred to by Nuuk on his decibel dungeon site.

Maybe someone can comment on the application of large filter caps in battery supplies and what they do for filtering?

There is only one supply to serve 2 right , left circuits. The ground is attached to the negative ground plane or central ground wire as I did, and then on to the neg. at the bat. pack

cheers
Thor(doggy)
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Old 25th September 2006, 06:44 PM   #6
Ropie is offline Ropie  United Kingdom
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Default Re: power supply

Quote:
Originally posted by doggy
[B]This battery supply is part of the "duplex" schematic.
Oh, I should have seen that thanks!
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Old 26th September 2006, 08:23 AM   #7
owen is offline owen  United Kingdom
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The caps improve the slew response of the battery, and improve the sound to boot.

Dropping a 2 or 3 mH choke in the +, - and ground legs kills any chemistry noise in the supply too, and you can do that before the caps to ensure a silent supply.


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