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Landed a NAC102... what's the first mod to do?

JimmyB

JimmyB

pfm Member
Managed a bargain NAC102 on eBay with a Napsc for £107 which leaves funds for a DIY Hicap to be built.

What's the next best solution to regs in the 102 itself? TPR4 in Hicap or other Homebrew option (don't want to cut up the 102 internally).

Last question, are my pair of NAP140's or NAP160 dual mono clone up to living with this beastie?
 
I'd consider to route the preamp output signal from Nac 102 to amps directly.
 
Sorry Jim, yes, very likely you need to - slightly - cut up the 102 internally.. but this should be reversible.

I cannot be very precise how to do it on the 102, and hopefully not wasting your time here.. however.. I did this on my 32-5 with good result, I de-soldered the plus left and plus right signal out from internal feet of 240° 5pin din amp socket which usually route through the hicap/snaps.
I took out another preamp existing din socket and substituted it with a proper 4pin din to which I soldered the plus left, plus right and negative signal out.
Hoping my English is clear enough..
 
That's a good way to do it - if you don't like, or eventually don't want the 102 or the split-output mod, you can sell-on either or both parts unmolested :)
(and frankly your is a bargain buy, even with the cables bought on top!)
 
Indeed, felt guilty picking up (collection only on eBay).

It's a bit late to get in touch with Avondale tonight and will be busy tomorrow at work so wondering if anyone knows what voltage range the TPR4 needs? I have a 600va 30-0-30v transformer on hand and a smaller (150va?) 25-0-25v one, would the big beast be too much?

Cheers,

J
 
The 102 is not so simple to mod socket connections inside - most of the DIN sockets are hard mounted on the main PCB so no chance of disconnecting cables- you have to cut PCB tracks. The 25V transformer should be fine for the PSU. But for best results you should be looking at a transformer with twin centre-tapped secondaries (as with the HICAP) so that you have a rectifier and smoothing cap for each 24V regulator to the pre-amp. Plenty of info about this if you search through the DIY pages here.
 
Good score on that 102! It's a marmite preamp in the Naim camp - the 72 worshippers say it's too brash/bright etc but really the 72 is just dull ;)

In relatively unmodified form (more on that later) it can give brilliantly insightful and musical results simply by giving it the cleanest power supply you can buy/build.
Step 1 is either get hold of an NAPSC or build a clone, then fit the gyrator mod as per the napsc-shocker thread Jo has linked to above. Do not underestimate the importance of getting the cleanest possible supply to the digital/control bits of the preamp. It really does open up a window to use that well worn audio cliche.
Step 2 is a matter of building the best possible dual 24V supply you can. The TPR4 offers DR style performance given a nice chunky primary supply upstream of it, and I know from personal experience it's a great 'drop in' regulator for a standard Hicap. However, there's another way to get a superbly capable supply and that's to simply add the above gyrator mod to Naim's own 317 based regulator. Since quite a few folk have seemingly fitted TPR4s in their Hicaps, it should be possible to pick up a Naim reg cheaply and modify it by adding 2 gyrators. I have 2 Hicaps modified this way, one powers my phono boards and the other powers my 102. The results are up there with what the TPR4 does in terms of resolving more information, but with a slightly less forward presentation - which I reckon helps counter the slightly forward presentation inherent in the 102. Hope that makes sense.
Step 3 is the single mod you can safely (and reversibly) do to a 102 that you'll shake your head at; Replace all of the PCB mounting pillars with precisely cut lengths of silicone tubing (model engine fuel tube is perfect), so that the board is effectively decoupled from the tray and case.

Mr Tibbs
 
is that the one from Edinburgh by any chance? I was going to have a bid on that myself, but then remembered I already have a 102 and that I really don't need another! You basically paid the going (ish) rate for a Napsc and got a free preamp! I thought I'd done well with a CD3.5 for under £200. Clearly not!

I very much like the idea of the fuel tube mod. Might have a crack at that over the weekend. Did the Acoustica mod #7 to my CD3.5 today and yep, very worthwhile!
 
Mr Tibbs said:
It's a marmite preamp in the Naim camp - the 72 worshippers say it's too brash/bright etc but really the 72 is just dull...
Click to expand...

I use a 102, with Avondale PSU's and I prefer it over the 72 that I had previously and yes, that is an amazing price!
 
Tristan Kelly said:
is that the one from Edinburgh by any chance?
Click to expand...

Yes it was, and I had to travel around 1 mile to collect as it was in the same village! My top bid was way higher so it was a shocker what I got it for...someday I will admit to SWMBO that it is in the house and yes, my amp total is now over 10....(passive pres , SUTs and phono amps don't count)

MrTibbs, that a great summary, thanks so much. Think that's the way to head. I'll keep my eyes out for old Hicap reg and mod that with your gyrators. Nice and neat.

Does vibration isolating the board make a difference? I also spotted mass loading the motors too, is that a similar? Precisely is very precise, that's just what I like...over-engineering to the nth degree. I can see myself making a cutting jig to ensure the same length...and having a model making brother, stealing silicone tube will be a cinch.
 
Other mods to consider at a later stage..IIRC there is a tape buffer circuit....if you don’t need it disconnect it from its power rails...lift a leg of the 27R is easy way. Ultimate mod is to power each circuit section with separate regulators built into the amp. The ALW super reg works well here.
 
JimmyB said:
Does vibration isolating the board make a difference? I also spotted mass loading the motors too, is that a similar? Precisely is very precise, that's just what I like...over-engineering to the nth degree. I can see myself making a cutting jig to ensure the same length...and having a model making brother, stealing silicone tube will be a cinch.
Click to expand...

It makes about as much difference as adding an NAPSC. Adding some mass loading makes it more effective but no need to get carried away here. I attached some small pieces of lead sheet to the pots using double sided tape as this is probably the area most likely to benefit. Here's an old pic I found that shows the mass loading and one of the silicone mounts in place.

16635999471_135ce6f46b_z.jpg


Mr Tibbs
 
Below is a Neil Jadman modified 102 powered from a Naim NAPSC to 7 x TeddyRegs. Naim circuits extensively modified along with star earthing.

I have a pdf document describing and detailing the mods - if anyone wants a copy, then PM me.

I am intrigued by Mr Tibbs tube decoupling mod. I will try that sometime. I've always wondered about DIYing a decoupling floating spring as Naim do on some higher end products.

C2x465L.jpg


TcWUbb2.jpg
 
Are the DIN sockets not mechanically attached to the rear panel, only to the PCB? Does this mean that the volume and balance knobs wiggle the board? And does plugging/unplugging cables also move things around?
 
booja30 said:
Are the DIN sockets not mechanically attached to the rear panel, only to the PCB? Does this mean that the volume and balance knobs wiggle the board? And does plugging/unplugging cables also move things around?
Click to expand...

Yes, the whole PCB including the pot's and DIN sockets are decoupled from the chassis and 'float' on the silicone rubber 'pillars'. That's probably why it makes such a noticeable difference, because all of the problem areas are no longer subject to vibration via the case and tray.
In practice (providing appropriate tubing is used and is accurately cut) the PCB tends to resist movement away from its normal location, though obviously it will move slightly when connecting up snaic and source cables. Just a little extra care is needed to ensure none of the cables are under tension when hooked up, so the board remains floating freely away from the chassis. We're not talking LP12 levels of suspension tweaking here - just make sure there is still free movement in the board after plugging everything in and you're done. It's got to be one of the cheapest and easiest to do/undo tweaks, so somebody give it a go and report back :)

Mr Tibbs
 
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