ThePre

[Mr Onion]

ThePreBlack3.jpg

Whats ThePre I hear you ask. Its my latest project to (hopefully) improve on my existing NACish 72 PreAmp.

The Idea

The NAIM NAC72 (upon which my PreAmp is based) is a fantastic Pre, even by todays standards but has one major failing for those of advancing years. No remote control. There is little free space inside a 72's case so it would need a total rebuild. Yes, I could replace it with a 282, 252 or even a 552 but at an ever increasing cost and all of them have facilities and features I would never use. All I need is 4 or 5 inputs and a volume control.

Research

You can buy 'remote control' modules on Auction Sites, mainly from China. Most say they have an 'Alps Blue' but at the stated cost quality has to be questionable, and even a genuine 'Blue' is not as good as the non remote controllable Noble I already have. Others have 'ladder resistors' but again at what quality. What I want is a quality package that can easily be added to NAC 72 based boards.

TKD make a fantastic sounding remote controllable Potentiometer, and HiFiCollective make a modular Remote control system that works perfectly with the TKD

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glasshouse-remote-control-350_0.jpg

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So with that the idea started to become reality.


Why "ThePre"?

Why not? I had the space where the bling badge was removed so I needed something classy looking to fill the space. I am not putting NAIM on the box, cos it ain't NAIM.

[Mr Onion]

Boards

My NACish 72 uses a custom board designed by Neil James that has space for 4 TeddyRegs and allows you to use either the original NAC 72 321/729 daughter boards or Neils own improved ones. I have tried it with both, but have stuck with Neils as they are just better being based on the same circuit that is in the NAC 52.

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boards_front.JPG

boards_back.JPG

Teddy has spend the last 12 years or so working on improving his regulators, going through the SuperTeddyReg and latterly the MiniTeddyReg which is not much larger than a TO220 semiconductor package. Great idea, small and space saving too. Far better and precise regulation than a HiCap, probably more like a NAIM DR module.

mini_teddy_regs.JPG

Put the two together and the result will be better than a NAC 52, maybe better than a NAC 252


The remote control boards use the industry standard RC5 codes, as does my NAIM CD player and there are conflicts which I could not resolve. Luckily the Remote Control Kit designer can re program it to work with an Apple TV remote control which is paired with its receiver to avoid such conflicts. Not a cheap option as such expertise does not come cheap, but it will remove hours of frustration.


Case

Simple requirements, difficult to satisfy. It needs a space enough for all the components, look smart, and have a 'window' to allow the remote control commands to be read then the figure 8 LED to be seen. After checking many many sites I found this.

case-1.jpg

The backplate is available in many versions, but none fitted my needs. The seller was happy to supply a 'blank' for me to drill myself.

Other Components

The TeddyRegs need +30v the Remote module needs ~12v, so a double power supply while seeming excessive was the obvious answer as it keeps the signal and control circuits totally separate. NAIM have also had the same idea. So I ordered a Custom Audio Quality transformer from Canterbury Windings, and a 'normal' transformer and other bits from either CPC, HiFiCollective or my parts box.

The Power Supplies will be assembled in seperate case to keep the noise away from the sensitive bits.

(The remote control boards could be powered from a simple SMTP 'wall wart' but they are so noisy they usually add Mhz crud back into the mains supply. We don't want that hence the OTT linear supply)

[Mr Onion]

Starting work

The first thing to do after getting the layout right was to drill the holes. 7 DIN sockets, 2 Power sockets and a grounding post on the back. Lots of measuring, measure again, and re measure then a little work with the Bench Drill and I have

back-after.JPG

Neat and tidy, and not at all cramped.

Next drill the base for the PCB's mounting pillars. As before measure and re measure. The 'problem' was that as soon as I had decided on the layout and drilled the holes I had a rethink and moved things around. Hence the unused and blocked off holes in the base. The front panel hole needed slightly enlarging for the TKD pot and a blind hole for the anti rotation 'pips' on the Pot and Input selector and the drilling is all done.

inside-drilled.JPG

[Mr Onion]

Mounting the boards


First the Remote Control boards. The IR Receiver needed removing from the board and putting close to the front window. Also the 5 core lead from the Control board to the Input board needed lengthening. All fairly simple to do. the bigger problem was the Fig 8 display, which is supplied as red. Looks OK in its own right but awful in the context of the rest of my system.

Good News:- NAIM Green Fig 8 displays are readily available

Bad News:- They are a different pinout. Lots of time with the multimeter and datasheets allowed me to figure out how to wire it to rest of the boards. Again, check, check and check again.

... and it didn't work. Checked again, corrected 3 connections. Still no joy. Checked again and one segment on the chip was fried New chip ordered and all was well.

All mounted in the case and we have

Remote Connections.jpg

Next the backplate needs wiring up and connecting to the Input and Remote control boards. The reason for the output going through the remote control board is that 1) they come supplied with a switch on delay negating several extra components on the main PCB and 2) the reprogrammed remote now has a mute facility using that switch on delay relay.


Backplate connections are fairly easy, if a little crowded. All fairly self explanatory except for the bundle of signal ground wired which will terminate at the motherboard to keep the star earthing intact.

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Connecting the signal wires to the input and output relay boards completed this stage.

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[Mr Onion]

Populating the Motherboard

The Motherboard has space for Four TeddyRegs which is easily adapted for the new MiniTeddyRegs by adding one powersupply bypass capacitor and 2 links per regulator. The space for a Balance control is bypassed with Z Foil Resistors and I am adding attenuation of ~16db, again with a Z Foil resistor by using otherwise unused pads on the board. Yes I could have made do without this board, and constructed something on some Veroboard but this has two advantages.

1) It has all of the hole spacing correct where the 321 and 729 boards 'plug in'
2) The Star Earthing has been taken care of.
(well, three advantages)
3) Its far neater

motherboard_populated.JPG

All of the existing TeddyReg components bypassed and sockets added for the MiniTeddyregs.

[Mr Onion]

Connecting it all together

All thats needed now is connecting the three boards and volume control together. Lots of point to point wiring needing patience and lots of checking (as usual)

I added a 3.5mm jack to the front panel for convenience when playing from the LapTop. I connected this to the 2 'out' pins of input 5 and then made a 5 PIN DIN plug with pins 1 and 3 bridged and 4 and 5 bridged. Thus plugging that in has the effect of connect the jack to input 5. Perhaps not the ideal solution but gives me the option of 5 DIN inputs should the need arise.

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Then its out with the multimeter again to check that everything that should be connected is connected, and everything that should be isolated is isolated.

[Mr Onion]

Power Supply


I started with one of these, which is the same size and construction as the one for the Pre Amp but obviously without any cutouts on the front.

PS_case.jpg

... but this case has been delayed in transit so I assembled the Power Supply in two cases. I will update this once I have assembled everything in the new case.

As mentioned before there are two supplies for ThePre. A 12v for the Remote Control and a 30v for the Active boards. A 'normal' Toroidal Transformer for the Remote Boards, and the Audiophile one for the active boards. They produce raw rails for the circuits in the pre to regulate as necessary.

[Mr Onion]

First Powerup


Before connecting anything I went through all of the soldering again, again and again. Then checked the connections, and checked it again. Once I was happy that nothing was cross connected, no dry solder joints etc I checked the Power Supply outputs.

Everything as expected, so plug the power supply to the pre, hold my breath and turn on.





... and it works. All voltages correct, nothing exploded or burning. So I guess I had better test it, but I am not risking my Kudos Super 20's, so I plugged it into the Computer Amp and Speaker, switched on, added a signal, and we have music

PHEW!

So its time to be even braver and plug it into the HiFi .


... and its still working. Just a couple of little glitches:-
1) Constant low level hum. Cured by adding a ground drain to the 0v on the Remote Control Power Supply.
2) Very slight hum during switch on and mute. Not a big deal but I'm thinking about a fix for it.

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"How does it sound?" I hear you ask. Its the same as it was before, but better. Clearer, deeper clearer bass. Very defined vocals, without being clinical. No harshness. AND its remote controllable Exactly as you would expect a better PreAmp to sound.

No down sides at all, and the sound will improve over the next few weeks, but to be honest if it doesn't I will still be happy.

Its been a long project, maybe 5 months from idea to completion, and probably about 2 weeks works spread over the months. Worth the time and expense? You bet.

[Mr Onion]

What did it Cost?

---

ThePre Case			£  190
Power Supply Case		£   90
Remote Control boards etc 	£  400
Transformer			£   90
Teddy Regs			£  130
Audio Quality cable etc		£  140
Plugs sockets and sunderies 	£  130

Total				£1,170

Add in what I already had

321/729 boards			£  300

Grand Total 			£1,470

Plus about 80 hours including Planning, Drilling, Construction and Bug Fixing

---

Suppliers

AliExpress Case
Neil James Improved NAIM 321 and 729 boards, plus the motherboard.
Teddy Pardo MiniTeddyRegs
HiFi Collective Remote Control, Z-Foils, other Audiophile Components
Canterbury Windings Bespoke Audiophile Transformers
CPC-Farnell Standard Transformer, DIN sockets and other components
Russ Andrews Audio Cable and Oak Cone Feet

Everything else from my 'odds and sods' box

[Coyote Jim]

Here's one for you James.
Very well done and I doff my cap.
This should be read a few times to fully appreciate.
Thank you for sharing we just need your address for a visit and audition now.

[Wenge1]

Congrats James - A real labour of love that has borne you plenty of 'fruit' ...............
.

[Mr Onion]

More like a labour of stress frustration and swear words


Thanks both, I am very pleased with the end product.

[Wenge1]

More like a labour of stress frustration and swear words


Thanks both, I am very pleased with the end product.

Yes for sure; but how do you feel about making the Pre ..........

Sorry, couldn't resist ...........

[Mr Onion]

More like a labour of stress frustration and swear words


Thanks both, I am very pleased with the end product.

Yes for sure; but how do you feel about making the Pre ..........

Sorry, couldn't resist ...........

[Mr Onion]

Just over two weeks listening and a few more observations.

The sound is way clearer than it was previously. Treble clear higher and defined without any shrillness. Bass appears a lot lighter, but thats because the boom has gone. Playing a sweep tome I estimate that I am getting bass down to around 25ihz in room. Vocals defined and easier to follow (and in some cases its now possible to hear all of the words) Less muddled. Less congested. Less intrusion.

Its a far betterPreAmp than it was before, but the active element is identical (the same actual 321/729 cards that I removed from the previous PreAmp) so why the big difference?

Better power supply regulation (MiniTeddyregs vs First Gen TeddyRegs) running at a higher voltage (29v vs 25v) better volume control (TKD vs Noble) and better attenuation (Z FOIL vs Metal Film)

Never underestimate the contribution that the small details add to the whole.

The Power Supply is still a bit of a lashup being in two separate cases as the full width case I ordered is stuck at the airport pre customs. No idea whats happened and I have no way of finding out. It'll get here when it gets here and then I can give ThePre the neat looking Power Supply that it deserves

[wiltshireman]

More than impressed! If I used Naim I would probably have a go myself.

[Mr Onion]

Thanks. Its been a long time getting there (and the PS yet to be completed) but if you have a 72 or 32 its well worth the effort.

If you don't factor my time its a bargain, factor in my time and it would probably be cheaper to buy 552

[Coyote Jim]

An update on this is seriously overdue.

[Mr Onion]

Well, the Power Supply has not changed since my last post and is still in its two separate boxes. The broken hip and subsequent lack of mobility delayed any work, then the por weather and my ME being bad just compounded things.

I am hoping the rebuild will get going in the next month or two now I can get into the garage to make a mess. For some reason Mrs O says I can't bring the Pillar Drill into the kitchen. Why are wives so unreasonable?

The Preamp it self is still amazing me in the way it doesn't amaze me It just gets on with things quietly and lets the music flow. No fireworks (either literal or metaphorical) nothing spectacular. It does what a good amp should do, a straight wire with gain.

I did manage to finally solve one strange issue. The Apple remote control handshakes to ThePre to avoid interference between other remotes, but the TV remote (not Apple) sometimes adjusted ThePre. Very strange. After literally months of experimentation I discovered that the TV's remote signals were travelling down the power cable, into the power block, up ThePre's remote control power lead and causing the problem.

I put a few turns of the TV's low voltage supply through a ferrite ring and that solved the issue.

If you had told me that was the cause I wouldn't of believed you. It just goes to so that theres no substitute for experimentation.

[Mr Onion]

Power Supply

Well, since then and now many things have changed in my life and I have not been physically or mentally aware enough to finish the power supply properly, so I contacted Sean at Custom HiFi Cables Ltd. who agreed to construct it for me using one of hisDC4 RECAP module which is fitted with Mundorf caps.

PS_Board.jpg

which is being fed by a custom made Canterbury Windings Transformer to power the active boards in ThePre. There is also an off the shelf transformer and 12v rectifier board to power the control boards, all assembled in a ModuShop Galaxy case.

It arrived today and after a small bug was attended to (the ground drain I had previously fitted to the Control Boards needed removing) its lifted ThePre to the next level. All round better and I am glad I made the decision.

Now I can finally put the build behind me and enjoy.

[Coyote Jim]

Power Supply

Well, since then and now many things have changed in my life and I have not been physically or mentally aware enough to finish the power supply properly, so I contacted Sean at Custom HiFi Cables Ltd. who agreed to construct it for me using one of hisDC4 RECAP module which is fitted with Mundorf caps.





which is being fed by a custom made Canterbury Windings Transformer to power the active boards in ThePre. There is also an off the shelf transformer and 12v rectifier board to power the control boards, all assembled in a ModuShop Galaxy case.

It arrived today and after a small bug was attended to (the ground drain I had previously fitted to the Control Boards needed removing) its lifted ThePre to the next level. All round better and I am glad I made the decision.

Now I can finally put the build behind me and enjoy.

Many congrats and best wishes to your feeling better and The Pre being complete just need some box photos now.

[Mr Onion]

Sean torqued the case bolts to tight I can't get the lid off. I'll get full frontal shot later (ooer missis)

[Coyote Jim]

Sean torqued the case bolts to tight I can't get the lid off. I'll get full frontal shot later (ooer missis)

I want to see the whole spread.

[Mr Onion]

Just a snap as I can't be arsed to move the armchair out of the way

stack.JPG

Top to bottom

LP12

ThePre

CD5si

Radikal A

ThePre PS

ZAP250 (NAIM NAC250 boards with dual mono unregulated PS)

[Coyote Jim]

Just a snap as I can't be arsed to move the armchair out of the way





Top to bottom

LP12

ThePre

CD5si

Radikal A

ThePre PS

ZAP250 (NAIM NAC250 boards with dual mono unregulated PS)

Nice one James a while in the making but a great achievement be proud and turn it up.