NJ 72 Preamp

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Mr Onion
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NJ 72 Preamp

Post by Mr Onion » Sat Mar 22, 2014 2:40 pm

I've just spent the morning re making the power umbilical between the power supply and preamp (the old one was captive, and bloody annoying when trying to move the unit)


screenshot_555.jpg


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The power supply is a 24v 80va transformer, rectified and smoothed to single rail 35v dc

The Pre amp has 4 TeddyRegs running @ 25.5v dc each powering one of Neil James' improved NAC72 boards.

The re wired units sound a little tighter than before. The result (I think) of better construction and a screened umbilical.
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

grimreaper46
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Re: NJ 72 Preamp

Post by grimreaper46 » Sat Mar 22, 2014 8:25 pm

Clever sod.

xss09
LP12 (now with the special Peter Swain magic touch and a Kore and T-Cable) for analogue, Majik Aktiv System for digital

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Re: NJ 72 Preamp

Post by Mr Onion » Sat Mar 22, 2014 9:10 pm

The mother and daughter boards were made by someone else. I sourced the cases, the PS components and all the wires/plugs/sockets etc myself.

The PS was easy to make, assembling the Pre a bit more complex.

... and I didn't fuse the street or burn my fingers with the soldering iron :smt023
James
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

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Re: NJ 72 Preamp

Post by Mr Onion » Sun Mar 23, 2014 12:59 pm

Listening to the HiFi today, the sound has certainly improved. There is far more detail than there was previously. Amazing what changing something seemingly insignificant can do.

Of course, it could be breaking and making the connections thats made the difference. Or the better quality solder. Or ...

Who knows? Who cares? I'm happy :mrg:
James
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

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Re: NJ 72 Preamp

Post by Coyote Jim » Wed Sep 14, 2016 1:12 pm

Mr Onion wrote:Who knows? Who cares? I'm happy :mrg:
And that is all that matters 8)
I'm a firm believer especially with recent mods and soon to be upgrades that depriving one self of the system for a while brings great benefits.
Absence makes the heart " and ears " grow fonder. 8) :smt023
"Cymbiosis"
Klimax LP12, Linn CD, Linn Amp, Kudos Speakers.
Coyote Jim :wink:

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Mr Onion
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Re: NJ 72 Preamp

Post by Mr Onion » Fri Nov 16, 2018 12:44 pm

Now I have a Urika inside my LP12 I have some space on the rack. I was never totally happy with the power supply I made for the pre (It was far to cramped inside for my liking) but now I have a small PS taking up a full width shelf. Hmmm, I could use that space. A new case of that size can cost £100 or more, so how about a dead unit from the LINN LK range? Theres plenty on ePay and I got an Intersekt for ~£50. Stripped it out, had a new back plate made at a local Aluminium supplier just for the IEC Input and a XLR for power out to the pre thus covering the numerous holes the Intersekt has.


DSC_0093.JPG


Then I needed a good transformer. 'Off The Shelf' ones are OK, but they are mass produced for all purposes, not just Audio. I have heard good reports of Canterbury Windings so contacted Terry who will make to order. So I ordered a 240v -> 2x 24v 160va toroid. Not cheap, but not IMHO expensive (about double the 'off the shelf' price)


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Next the rectifier board and components. I had a spare board from when I made the original Power Supply which allows for a RCRCRC configuration. This gives a smoother supply than just using a capacitor and the unit being powered only 'sees' the last capacitor in the chain. Radio Spares had all the parts I needed:-

2x Rectifier Diodes 8A 600V
5x Wire Wound Resistors 0R47 (I only need 3 but 5 is the minimum order)
3x Capacitors 2200uf 50v


DSC_0094.JPG


Other bits came from my parts box.


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Put them all together and what do you get?


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All cables sleeved/twisted/plaited to prevent rattles. The Clarity Mains box you can see is from Russ Andrews and fits nicely in the case.



I triple checked I had the output configuration correct and then checked again before plugging it into the system.


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... and it works!

How does it sound? Well to start off the transformer isn't quiet, its totally SILENT. The old 'off the shelf' had a slight buzz to it. You could only hear it if you were right next to the PS but not this one. But onto the Music. With only a couple of hours power in the caps its sounding better than the old PS. Everything is just a little bit better. Things that you might put down to being things the Power amp or Speakers do (a nice sharp drum hit for example) are sharper. Perhaps theres a slight 'glare' about the sound (and I mean slight) but that will diminish as the caps run in.

Total cost? Under £200 plus the odds and ends I already had. Time taken? Perhaps half a day over 2 months planning ordering and getting the custom parts made, and worth every penny.

Conclusion? Never underestimate the importance of the Pre Amp and its Power Supply
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James
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

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LD100
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Re: NJ 72 Preamp

Post by LD100 » Fri Nov 16, 2018 2:17 pm

Congratulations on a job well done :smt023 ...now, what's the next project? :shock:
Original 1978 Fluted Afromosia LP12, Ekos 2, Lyra Kleos SL and lots of other stuff from the 70's that still work fine.

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Mr Onion
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Re: NJ 72 Preamp

Post by Mr Onion » Fri Nov 16, 2018 2:25 pm

Weeeeeeel, I had wondered about swapping the volume control for something a wee bit better.

I quite fancy this one

glasshouse-charcroft-seiden-ladder-350_0.jpg
Glasshouse Ladder 100K stereo 23 stepped attenuator, featuring Charcroft resistors on a Seiden switch.

We are pleased to announced we have created probably the best ladder step attenuator money can buy. Combining the best sounding resistors, the 0.4W Charcroft Z-foils and the beautifully crafted Seiden 4 pole 23 pole switch. Constructed using Mundorf 3.8% silver/gold solder with 1mm HGC pure silver as the earth ring. Truly astounding sound stage, clarity and detailing. Supplied fully built.

Dimensions: 60mm diameter x 70mm depth.
PRICE (1 off)
£1400.00+vat+p&p
:shock: from HiFi Collective
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James
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

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Coyote Jim
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Re: NJ 72 Preamp

Post by Coyote Jim » Fri Nov 16, 2018 3:45 pm

James,
You PS is really a work of dedication especially with the recycling of that lovely old LK project box.
As usual,no compromise or corner cutting in your jobs. :wink:
You do realise you have to change the Kosmetic Naim on it. 8) :smt023
Maybe with a sudden change of use it should be called the Interjekt. :roll:
"Cymbiosis"
Klimax LP12, Linn CD, Linn Amp, Kudos Speakers.
Coyote Jim :wink:

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Mr Onion
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Re: NJ 72 Preamp

Post by Mr Onion » Fri Nov 16, 2018 5:47 pm

Thanks Jim

If I knew of a way of removing the LINN logo and name without damaging the 'crackle' finish I would.
James
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Fluted Afro LP12, Khan, KEEL, Cirkus, Tranquillity, Urika, Radikal (with Allium Skin Mods), EKOS SE/1, sKale, DVXX-2mkII
Consonance Ref 2.2 Linear (upgraded) with Marigo Lab Aida CD Mat
NACish 72, NAPish 250, Kudos Super 20's

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