Dual Rail Snaps?

Posted by: Chris L on 02 May 2001

I've seen mention of a modification to run a Snaps as a dual rail ps. Can someone tell me (in simple language - it's been a long day ;-) how to check if mine can be converted?

Also, is this a mod that Naim do, or is unofficial and requires owner wielded soldering irons?

Thanks,

Chris

P.S. This is my first post after registering, so I'm all excited!

Posted on: 02 May 2001 by Chris Brandon

Hi Chris

Welcome to the Forum !

For a bit,well,actually, a fair amount of info on Dual Railing a Snaps.....

http://forums.naim-audio.com/eve/forums?q=Y&a=tpc&s=67019385&f=48019385&m=800197783#864190824

After digesting this little lot,if there is anything you are unsure about.........just ask !

Regards

Chris

Posted on: 02 May 2001 by Mike in CO

I dual-railed a SNAPS over six months ago to use it with a 32.5, and would recommend it as an easy, cheap improvement for someone comfortable with doing their own electronics work, and hacking into their gear. Although it didn't make a huge improvement, it is noticable. A HiCap will spank it in every way, but if you can't afford that, this is a decent step inbetween.

What made a more substantial change for my system, however, was actually undoing the dual-rail back to a single rail. By ganging the two transformer windings together, and changing a few components, I made a beefier dual-stage regulated single-rail supply. Quiet got quieter, loud got louder, and the music stepped up and grabbed me much more immediately. This is NOT an easy fix, and I'd recommend it primarily for people who have experience with electronics and replacing components on a board. Or perhaps for those who want to spend time -- and risk their gear -- learning such. Or for the generally nutty.

Even with the SNAPS changes, I think the 32.5 gained more improvements from removing the extra cards and adding the 72 filter. And much less risk/hassle. I also think it helped that I use this second system in my office, with CD/Tuner only, and have yanked all but the necessary cards out. There's really only one thing to power anyway. With phono and CD it may not be the same result; dual-rail may be better.

Some key things the above highlighted post on dual-railing a SNAPS left out:

1 - Start saving for a HiCap now. It really is a major move forward, and this mod, although it helps, isn't even close. You'll laugh out loud when you hear the difference.

2 - You need to replace one of the 4-pin sockets with a 5-pin, but be sure you get a 5-pin with the same pin arrangement as the POWER input on your 32.5, NOT the same as the source inputs. You want the 240-degree DIN5.

3 - The LM317's in a stock SNAPS can vary widely, and most are not so hot. (Mine weren't). They're older and not as precise as newer ones. I replaced them with two matched LM317AT's, which have tighter control on the voltage. Some of these can have more noise, so it's good to either have a supplier test for you, or get a few and sample them. Use two that are as close in performance as you can get. Unsolder the existing ones, and resolder the new ones in, they look exactly the same. Again, not for the faint, but good results if you are handy with a soldering iron.

3 - If you do the above mod, BE VERY CAREFUL AND AWARE OF HOW THE 317s ARE SECURED TO THE CHASSIS. For each there's a small insulator, and plastic washer/insulator, that keeps the regulator case (which is the "hot" voltage) from passing to the chassis. If you don't get that right, you can give yourself a shock (24v DC) and possibly damage your preamp.

Again, I suggest these tweaks only for those a) on a severe budget, b) working on a second system, c) insanse enough to actually try taking apart Naim gear. I, sadly, could qualify for all three based on this.

Good luck!

Posted on: 02 May 2001 by Mike in CO

Chris-
I realize your post said "In plain English..." and mine may not have been. Sorry if my ramblings are more confusing than enlightening. Just thought others might benefit from the info as well. Good luck.

Posted on: 02 May 2001 by David Dever

quote:
By ganging the two transformer windings together, and changing a few components, I made a beefier dual-stage regulated single-rail supply

Last I looked, there was a single secondary winding on a SNAPS transformer (grey / yellow), with a center tap--do tell where you found the other winding...

Dave Dever, NANA

P.S. In the U.S., the primary windings are ganged together by default, using twice the fuse rating.

Posted on: 03 May 2001 by Chris L

First, Mike, your reply was in sufficiently plain English that I could follow it. My problem is that I know snippets about electronics, but not all that much, so what usually happens is people tell me about something, and I understand enough to get the idea, not enough to form a step-by-step in my head.

Anyway, thanks to all who replied. I'm thinking I'll just go straight for a Hi-Cap. I decided to upgrade my amps a few months ago, from the current 32.5/Snaps/140 to a 32.5/Hi-Cap/250. Basically a suitable 250 came up first, and the reason I was looking into modding the Snaps was just as a stop-gap.

Plus, shortly after I posted yesterday I found out I'm getting nearly 300ukp refunded from my bank - a good start to the cost of a Hi-Cap!

I may still do the mod to the Snaps, tho', as it could be used with my spare 42.5 pre-amp and soon to be spare NAP140. Would be interesting to hear the difference!

Thanks, folks,

Chris

Posted on: 03 May 2001 by hifidaddy

as the both rails on 42.5 and 32.5 do not split left/right but phono/line, it is the use with vinyl which profits most from such a mod.

I did it myself, and well the difference was in the order of adding the Snaps to the 32.5 normally fed by the 140.

regards,
Hartmut from Munich

PS: did anybody 110' a 140 with the same mod as
described in the second post, just paralleling the secondaries to give more beef to the whole than only little beef to the separates ?

Posted on: 03 May 2001 by Mike in CO

Dave & others -

I stand corrected, what I merged were the two lines coming from the smoothing capacitor. Thanks for pointing that out.