advertisement


What to do with Naim Nac52 + 52PS

bob mccluckie said:
not before time.
Click to expand...

As I have next to zero grasp of electronics I seldom read threads in this room so I miss a lot, i.e. don't assume that I'm even aware of any trouble. Please report 'noise' or trouble making posts or tip me off with a PM - I really want this room to remain a calm and intelligent place where people can learn and share ideas. I'm very proud of this room, some cool stuff has emerged from it over the years.

Tony.

(who doesn't really understand what a pfm Flea is, but has one in his CD player!)
 
Hi chrism and everyone.

The plan is definitely to leave the 52/52ps as stock and concentrate my efforts on building an Avondale pre+psu to replace it.
I am just deciding whether to strip out the 92r box and build the new pre inside that, or to save for a while and then go for a Grad 1.

If I use the 92r box, I still need to decide whether to use the 821 or the 821a boards.
Also, I need to find another box to fit the psu into.

Decisions, decisions! 821, 821a or Grad 1. Hmmm!

Anyway, it's nice to see the thread has quietened down a little now.

One more question: Can anyone tell me if they have ever tried using completely separate transformers for the 2 power supply channels for the pre amp and if they heard any benefit? I would imagine that 2 separate transformers (say 500VA) would allow better separation between the channels than one even bigger one, yes? Or does using decent (separate) regulation on each channel completely negate any benefit possible from 2 transformers?

Regards to all who have helped. Much appreciated!
 
Si , if you are going to use 821 boards , use the Audiophile version , yes I know they are more expensive , but the sound is much better , more dynamics and scale , sweeter top and tighter bass .
how do you edit the title , another typo....... damn
 
Si-Pi,

Yes, 2 transformers is better (or, 4 secondaries is better than 2...); I originally built a dual 24v PSU with one dual secondary transformer using full-wave rectification to feed the separate regulated supplies, and ran it happily for 4-6 months. I then added a second transformer and switched to half wave rectification allowing the removal of 2 diode joints per regulated supply.

Opened out the sound very well, increasing blackness between individual sounds.

Also consider multiple supplies to feed each stage - if you use 821's it may not be so relevant (unless you want to keep the Naim phono stage too?), but if I were in your boat I'd start off building a decent DIY PSU for the 92 in it's current state first - all the better to judge the gains of then moving to 821's afterwards.

Your next question will be what sort of regulated supply to use; VBE'ed ALWSR, Traco's or TeddyReg's. All valid, I only have experience of the former currently.

Richard

Richard
 
Thanks Dowser

For each channel of the PSU I am envisaging using a 400ish VA C-core transformer and an Avondale APX2 reg board set to 30V.

Inside the 92R box there will be (per channel) a reservoir cap (Kendeil?) with bypass caps (any opinions on choice here would be very welcome!) feeding a teddyreg or Avondale TPR (I might play with both). The resultant output will power a closely situated Avondale 821a pre amp board. Wiring will mainly be with HGC pure silver hookup wire from hifi collective.

Inside the rest of the 92R case I will be looking to improve the shielding of the rc circuitry and of course making a small separate regulated external supply for it.

As well as choice of reservoir bypass caps, what motorised pot would everyone recommend? The volume pot definitely need replacing! Also, I'm thinking of leaving the balance pot out of circuit. I never use it.
 
Cheers, yeah been browsing there. Looks like it'll be the standard alps blue then, or I'll decide to ditch the idea of keeping the RC and go stepped attenuator instead.

Would it be worth it I wonder...
 
Si , if you really need the remote keep it ,if not ....stepped atenuator , you know it makes sense , mmmmmmm
 
Deep down, I know you're right, sigh!

Thing is, I'm wondering if it isn't just best to start from afresh now, new box, everything. Do you think the selector board will be ok to re-use? It'd be nice to salvage something from the 92R! There again if I ebayed the 92R I would have between £100 and £200 ish to go towards starting again. Actually, yeah, it does sound like the best idea now I come to type it down.

So, a new box and everything then. 92R to go on ebay to help fund the expense.

Right, 3 last questions:

1) If I go stepped attenuator for the volume pot, is it ok to go Dale/Vishay or is the Glasshouse/Shinkoh/(Elma/Shalco) really worth the extra huge wad?

2) For the selector, is it best to go with the Elma 2 pole 6 way switch or would the glasshouse 2 pole 6way selector switch kit be best? One other option is a reed relay switch pcb that might have to be of my own devising I assume...

3) Are there alternatives to what I'm proposing? Can anyone explain to me if the Starfish is worth considering?

Cheers!
 
Si , good move e-bay the 92 , free up some cash , build a minimalist pre amp , 821 boards , Volume pot , selector switch (some input sockets) and a PSU based on your choice from those listed (all good by the way) . You'll need to work out a star earth and you are done , I'd use a bit of a unetched PCB and drill a circle of holes in it , hard wire everything ....job done .
 
Tiz decided then!

Thank you for all your help zener!
I take it you might be interested in pics as I build?

Thanks again
 
Excellent plan Si!

The route you are taking is exactly where my Nac72 is heading. I've stripped out the boards i don't need (324,729,325) which only leaves the 821a and 323 MC boards. It's a shame i run more than one source (LP12 and CD3.5) otherwise i'd have only one input, therefore no input selector needed. Oh well.

Starting from fresh is the best way forward IMO. You can drill the case for whatever is needed to be attached and use the components of your choice - how exciting.

Jon's idea for a star earth point is excellent and you could even seperate the power and signal earths - think of a flower with all its petals arranged around the eye in the centre. The eye could be the CDP ground connection if your using a naim CD player as signal and power earth are connected in the CDP. The petals could have one earth return each which all join to the eye in the middle.

Use good quality wire for hardwiring and rear sockets of your choice. As regards volume pots and selector switches, i have'nt quite decided what to use yet. DACT attenuators and switches do seem quite expensive but maybe they are worth a go? I've been thinking about using mono attenuators - i'll need one for each channel and they would act as a balance control also.

Finding suitable cases seems to be like finding rocking horse shit. Personally, i am making a new chasis for my Nac72 leaving the old one intact.

If your thing of using ALWSR's, there were some for sale in the classifieds the other day.

stu
 
By the way Mike L: I tried to send a return PM but your inbox is full chap!

Les. I'm sorry I haven't 'phoned you yet but I will, soon.
 
Hi mega lord

Yeah, finding a decent box is well 'ard.
RS have a metal equipment case range but they're in the £70 to £80 range and dang me if they aint the ugliest things you ever saw...
 
http://i141.photobucket.com/albums/r51/fluffvogel/100_0220.jpg

in your case youd have extra inputs going to a selector switch , then hard wired to the volume pot , directly wire volume to 821's and then 821 to output. Power is fed by the blue cable direct to the boards and is dual rail. The star earth point is where the green wire goes and all the earths are mounted in a circle around the green wire. Mother board is used to hold the 821's in place and for its star earth point , thats all.
 
Hi Jon, does the 32.5 not have powered relays for the mute function or have you removed them from your motherboard. I realise you do not need them in your application , just wondered.

David
 
no relays for the mute function in the circuit , if you forget to turn things on in the right order it just goes "thump" through the speakers. The Avondale TPX psu does have a fairly soft start so that may help , I can hear its relays clicking in.
 
You must log in or register to reply here.


advertisement


Back
Top