Pre-amp Nirvana ?

[Robert]

While the 102 was out of service, and with the benefit of a now standard Hicap, I bunged in my trusty 42.5 for a couple of hours. The whole lot was hooked up in completely standard Naim fashion. The result was eye-opening enough that I even converted the 102 back to bog standard (easily done with the Traco boards), for a try alongside the 42.5

I'll tell all later

Mr Tibbs

Tibbs goes back to basics and finds that Naim were right all along!

 

[martin clark]

My ears tell me that a linear reg followed by the RC filter is the solution.
Agree. I think this has been mentioned before (by Martin Clark), but that 27R/47uF filter is just right for taking over where the reg is beginning to pass noise.

Erk. Maybe. Perhaps, even; but only for the Naim CFP-based stage designs. AKA i'm pretty damn sure its not a universal consideration; 27R DC supply impedance is not something that sounds like a great idea, ever*

Either way, a three-pin-reg is no universal panacea against HF noise - although yes, 27R/ 47uF will perform well here, offering maybe 60db of HF rejection maximum.

*[size=-1]I've no way of measuring PSRR at the 300Khz that the Tracos work at... though I'm thinking about it[/size]

 

[Mr Tibbs]

AKA i'm pretty damn sure its not a universal consideration; 27R DC supply impedance is not something that sounds like a great idea, ever

Agreed, but it seems to work very nicely with three-pin regs and naim stages.

Tibbs goes back to basics and finds that Naim were right all along!

The truth (the whole truth, and nothing but the truth) will be revealed tomorrow...



Mr Tibbs

 

[MartinC]

Please tell us it's not going to be that a stock Naim beats all the modded versions... Mick P will be so overjoyed and excited that he will likely explode!

Cheers

Martin

 

[Jo Sharp]

Calm down girls!

If that were to be the case, how do they get a 52 to sound better than a 102? Multiple supplies is always going to be better, all else being equal.

 

[James]

Ahhh ... but a standard 102 with Super Duper Cap doesn't a 52 make.

 

[Mr Tibbs]

It's an age-old debate, but is still worth looking at from time to time. Do the mod's we do make any real difference, or are we just kidding ourselves big time? I haven't put a 'standard' Naim preamp near my system for many moons, so felt the need to go back to how the manufacturer intended – at least for a few hours.

Contenders were as follows;

42.5 / hicap all hooked up according to how Naim specify.

102 (in completely standard spec) / hicap / napsc copy. Again, standard hook-up.

Traco Power 102 (with in-circuit mod of filtered input bias resistors) / hicap / napsc copy. Output signal taken direct from pre to power amp.

I know how the 42.5 sounds – it's partnered with a 110 feeding MS20i's in my son's bedroom. Day and daily it blasts out music and X box games, and it sounds none too shabby. When I fired it up in my system I have to admit I was (at first) pleasantly surprised. Good, powerful and punchy sound, with a pretty decent bass kick, and nothing seeming too far amiss in terms of picking out individual instruments and voices. However, two or three CDs later and the penny dropped. Where was all the harmonic detail and richness, and worse still, what was that annoying sheen that contaminated every high note as soon as the music got busy? Cymbals were worst affected. I can't describe what they sounded like and I don't want to try. Awful.

Next up, I quickly put the 102 back to scratch – I just had to know if Naim's £1000 preamp (not including hicap and napsc) would address the quite obvious failings of the 42.5. Well, it did make a fair stab at it. At least now a cymbal sounded a bit more like a cymbal and less like a half-dozen biscuit tins falling onto a tiled floor. A bit, but not a lot. Instruments did now begin to sound like real instruments – the way they can sound when enough of the harmonic information is present and correct. But still, I couldn't live with this sound long-term. It is just too flawed, too lacking in reality compared to what I now take for granted from a preamp.

Traco Power 102 back in place. Ahh, normal service has been restored What does it sound like? Like it's not doing anything at all, really.

Mr Tibbs

 

[Jo Sharp]

told you.......


Nice to go back and check occasionally that we aren't completely mad, Mr T.

 

[Robert]

My 42.5 and 32.5 (with 72 cards) didn't make cymbals sound like biscuit tin lids falling onto the floor whether they listened to in isolation or against my trusty triode powered pre amp.

However, playing devils advocate a bit, most cymbals I've heard live sound extremely metallic, rather harsh and often with more than a little sheen. We are talking about banging bloomin great sheets of metal after all
Are you sure you haven't sanitised the music?

 

[Mr Tibbs]

OK OK, the biscuit tin lids is not a great analogy.

How about I just say that with the Traco 102, the cymbals sound like REAL cymbals (hey, we've even got a drum kit in the garage so I've got the real deal for reference!).

With the 42.5 and standard 102, I'm left wondering WTF that splashy noise is supposed to be. But, you're probably right that they're not that bad and I'm just being too fussy. Hell, what should I expect from a preamp and PSU that only cost £1500 :-/

Mr Tibbs

PS I know sanitised when I hear it - that's why I had to offload a year-old Ikemi. Ohhh, that terrible mistake still haunts me.

 

[Meirkat]

Hello to every one, I have just joined the forum.

I realise this is an old thread, but I recently bought a Naim 102 pre amp and I would like to ask for some advise please.

When I got the 102 I also had the napsc power supply with it, and (foolishly) thought I could just plug everything up and away I would go, - but no. - I now realise that I need another psu to power the 102 as the napsc only powers the digital bit.
I am an audio/electronics enthusiast and have built circuits and stuff in the past, so I was thinking I would like to build a 'raw' psu to get me 'up and running', then at a later date do the 'Mr Tibbs' Traco smps mod.

What I would like to know initially (if any kind soul can help) is what I would need to build a raw psu. I’m not after a massive unit like the Hi Caps and such like, just something basic I can use now, but will also be suitable to power the Traco’s later.

1. What transformer should I use? i.e. VA rating, voltage, No. of supplies etc bearing in mind the later mods intended for the 102.

2. What is the max voltage I should feed the 102 with, so as not to cause damage by over voltage?

3. Is the 'Mr Tibbs' Traco smps mod still valid ?

I must admit I am a newbie when it comes to Naim kit (it's usually way out of my humble price range), so any advice would be greatly appreciated.

Thank you all.

Kind Regards
Meirkat

 

[Mr Tibbs]

Long time no see old thread.

AFAIK not many people tried the 'Traco mod' so you might not get much in the way of opinion on it. It was incorporated in the very popular 'Starfish" preamp (by Jim) and seemed to work well in there.

For me, the natural successor to the 'Traco mod' would be a more conventional power supply, but connected up in a very unconventional way. In simple terms, the outboard supply would consist of 6 individual 24V regulated supplies, each fully independent (electrically isolated) from each other (but housed in one case for convenience). The 0V and 24V of each supply would connect directly to each of the six individual stages (filter/buffer/voltage amp x 2) via a 12wire lead. The all important detail here is that each of the six 0V leads would terminate at the negative end of the 47u smoothing cap of each particular stage. This would have the effect of removing power supply current from the star earth system of the preamp, leaving it as a high quality reference for signal voltages only.

I hope somebody will try it - I think it would be rather good ;-)

Mr Tibbs

 

[martin clark]

It is, and does work. But separating the 6 rails by suitable decoupling on each works just as well

IOW there's no intrinsic benefit from the complication of such separate supplies. You can get enough equivalent reverse-isolation other ways IME.

 

[Mr Tibbs]

It is, and does work. But separating the 6 rails by suitable decoupling on each works just as well

IOW there's no intrinsic benefit from the complication of such separate supplies. You can get enough equivalent reverse-isolation other ways IME.

That's fine as far as the 24V rails go, but you cannot configure the 0V rails as described above unless they are separate to begin with. I'll lash a drawing up later.

I actually did try this on a 42 preamp, using eight PP3s to give four separate 18V 'power supplies". It beat the same preamp fed with the 0V lines hooked up in conventional manner at the star 0V point.

Conventional method of connection:

Same PS but with 0V lines connected at each respective stage:

The alternative method has no power supply current flowing in the preamp star 0V system - that's the key to the improved performance this method brings.

Mr Tibbs

 

[martin clark]

Aha - see what you meant now; definitely agree

 

[Meirkat]

Hi,

I see what you’re saying Mr Tibbs, but why have you moved away from the Traco’s? I had the impression these were the ‘beez kneez’. Would it not be possible to do what you suggest using the Traco’s, - with separate 0v returns from the individual regulators?
Also this latest mod would require one of the big ‘---- Cap’ psu’s wouldn’t it?

Kind regards
Meirkat

 

[binnie]

Same PS but with 0V lines connected at each respective stage:

http://www.btinternet.com/~david.ste...42battery2.jpg

The alternative method has no power supply current flowing in the preamp star 0V system - that's the key to the improved performance this method brings.

This is somehow similar to the advantages given by the symetrical power à la NAC552 ... i.e. decoupling as far as possible the 0Volt (signal) from the nasty power grounds, I suppose ?

My next NAC will be a symetrical one with local transformer and Hacker CAPs with STRs (+/- 13Volt) and the usual 729s and 321s circuits.
My idea was to avoid connecting the 0volt of the signal to the NAC-internal ground but directly to the NAP ground.
The same question applies to the B4 Buffer.
Is it possible to NOT connect the signal 0Volt to the pre-amp internal ground ?
Well I will in any case make some tests.
Interesting idea you had Mr. Tibbs !
Cheers,
Olivier

 

[Mr Tibbs]

Hi,

I see what you’re saying Mr Tibbs, but why have you moved away from the Traco’s? I had the impression these were the ‘beez kneez’. Would it not be possible to do what you suggest using the Traco’s, - with separate 0v returns from the individual regulators?
Also this latest mod would require one of the big ‘---- Cap’ psu’s wouldn’t it?

Kind regards
Meirkat

I like to experiment with an idea then try something new. My own amps are standard now and will probably stay that way since I have little spare time to try new ideas myself these days.

The Traco's eliminate the external part of the 0V supply (from the outboard supply) but don't have any effect on what's happening within the preamp 0V system itself. This is where the idea of using multiple separate power supply (MSPS), then terminating each supply at each stage comes into play.

The MSPS would not necessarily need big transformers. I think something like 50VA per supply would be ideal, and could be small toroid or frame transformers.

Hope that helps

Mr Tibbs

 

[Mr Tibbs]

This is somehow similar to the advantages given by the symetrical power à la NAC552 ... i.e. decoupling as far as possible the 0Volt (signal) from the nasty power grounds, I suppose ?

My next NAC will be a symetrical one with local transformer and Hacker CAPs with STRs (+/- 13Volt) and the usual 729s and 321s circuits.
My idea was to avoid connecting the 0volt of the signal to the NAC-internal ground but directly to the NAP ground.
The same question applies to the B4 Buffer.
Is it possible to NOT connect the signal 0Volt to the pre-amp internal ground ?
Well I will in any case make some tests.
Interesting idea you had Mr. Tibbs !
Cheers,
Olivier

Yes, the MSPS idea is meant to eliminate power current running in the 0V system, so similar to the 552, but without the need to run a split rail PS and all of the circuit changes required to implement it. I don't know anything about the B4 preamp so cannot comment there. If you do a search you might bring up some old stuff about converting a Naim pre to split rail PS.

Mr Tibbs

 

[binnie]

I have to export my NAC to another bo, I will use the opportunity to test your idea.
I somehow like those tests (well, wont bother here otherwise )

Thanks
Olivier