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  #121  
Old 19-07-17, 11:49 PM
Julf Julf is offline
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Quote:
Originally Posted by rontoolsie View Post
The Naim resistors are specced as 1% tolerance (see diagram below). But based on upgrading resistors in other Naim products-the Superline for instance-there are great potential improvements out there.

Here is the circuit the analog portion of CDS3-showing exactly where these resistors could be upgraded and the values of them.
And what effect does one of them being, let's say, 1010 ohm instead of 1000 ohm have on the functioning of the circuit (in your view)?
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  #122  
Old 20-07-17, 01:26 AM
Dark Energy Dark Energy is offline
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I'm curious, what is the identity of those very small 47uF "Oil filled capacitors" with such a wide manufacturing tolerance?
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  #123  
Old 20-07-17, 07:32 AM
rontoolsie rontoolsie is offline
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The original gold colored caps (which are small, but NOT the oil filled ones) are French Promisic ones. I do not know what the measured values were some twelve years ago, but certainly with the passage of time they are about -40%. They are supposed to be pretty decent audio caps, yet replacing them yielded fairly profound improvements.

They are also scattered throughout the 552 for instance, so maybe that too can be subject to the same mods.
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  #124  
Old 21-07-17, 05:42 AM
MJS MJS is offline
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Those 47uF caps are bipolar electrolytics. Naim like the sound of them, there's no need for their bipolar capability in pretty much all the circuits they're used in. Other caps are available, YMMV.
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  #125  
Old 21-07-17, 06:19 AM
rontoolsie rontoolsie is offline
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From another source...

Sic Safco Promisic CO31 47uF 40v axial electrolytic capacitors - applications - Naim pre-amps and crossovers - NAC52, NAC82, SNAXO, NAXO, NAC552, NAC252, NAC282

So it looks like they are really found in their higher end equipment. I wonder if the negative effect they had on the sound was more being wildly out of spec, or just their sonic trait? Are these routinely replaced when gear is serviced/recapped?
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  #126  
Old 22-07-17, 05:53 AM
rontoolsie rontoolsie is offline
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Missing images added

I have gone back and restored all of the dead images all the way back to the very first post of this thread. This will enable new readers to get a better idea of what has been done so far.

In addition...here is a pic of the CDS3 head unit showing most (about 16) of the Cardas bypass caps that were fitted years ago.
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Last edited by rontoolsie; 22-07-17 at 06:37 AM.
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  #127  
Old 23-07-17, 03:17 AM
Jo Sharp Jo Sharp is offline
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Quote:
Originally Posted by rontoolsie View Post
From another source...

Sic Safco Promisic CO31 47uF 40v axial electrolytic capacitors - applications - Naim pre-amps and crossovers - NAC52, NAC82, SNAXO, NAXO, NAC552, NAC252, NAC282

So it looks like they are really found in their higher end equipment. I wonder if the negative effect they had on the sound was more being wildly out of spec, or just their sonic trait? Are these routinely replaced when gear is serviced/recapped?
I had a new mech and service done at Naim earlier this year. The invoice specified the replacement of capacitors (can't remember the exact number, but might have been 30+); so yes, they are replaced.
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  #128  
Old 10-09-17, 05:23 AM
Paul_Quigley_ie Paul_Quigley_ie is offline
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Ron,

Long time reader here. Love the description of the custom Chokes. It seams such an elegent way of improving the regulation while keeping the same sonic siginiture.

Would this work for a Naim 52 PS? How could I get the Chokes built?

Thanks
Paul
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  #129  
Old 10-09-17, 05:29 AM
rontoolsie rontoolsie is offline
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It would work very well on the 52PS...you would need two chokes. I had a Supercap2 choke regged for a friends NAC252, and he was amazed by how great it now sounds. He has twice been to Statement demos and prefers what he gets at home, albeit on a smaller scale. In a Naim system, the quality of the power and power supplies is 99% of the battle.

The chokes we use require machining of very high permeability T-yolk and intensive shielding. You cannot get equivalent spec chokes from anywhere else (30H, 15A continuous current, 0.25 Ohms DCR).

As mentioned somewhere above, they drop the ripple after the voltage regulator boards from around 1-2mV to 0.04 mV, as well as adding considerable low output impedance energy storage. A daunting task, but one that is greatly rewarding.
Quote:
Originally Posted by Paul_Quigley_ie View Post
Ron,

Long time reader here. Love the description of the custom Chokes. It seams such an elegent way of improving the regulation while keeping the same sonic siginiture.

Would this work for a Naim 52 PS? How could I get the Chokes built?

Thanks
Paul
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  #130  
Old 11-09-17, 12:58 PM
Paul_Quigley_ie Paul_Quigley_ie is offline
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Two Chokes for 52/PS

Hi Ron,

Thanks for the speedy reply.

So how do I get my hands on the two Chokes?

The inside of the 52/PS box is tight. It has a seperate transformer for the non audio controls etc. What about putting the Chokes in a seperate box? Would this cause an issue. Not sure if the chokes would fit in the space of the big smoothing caps?

Why has no manufacture attempted this solution. It seams so much more elegent than the discreet component approach?

Thanks
Paul
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  #131  
Old 11-09-17, 02:59 PM
rontoolsie rontoolsie is offline
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Yes, its possible to place the chokes externally-this is what I did for the power supply to the front end of the NAP500PS-to place two chokes outside of the box wired in with flyleads. Before choke regging the voltage gain section, the 500 always seemed to get harsh and fall apart when driven *really* loudly. I never really noted it until I tried out a Boulder 1020 (at 300 wpc) which showed the high SPL limitations of the 500. After the two chokes (a total of 12 is possible) there was much more grip and finesse in the 500, as well as a lessening of the tendency for 'motorboat' oscillation when using the Prefix.

Anyway-back to the question. These chokes are proprietary and thus far have been used in Supercaps, XPS, 552PS, 555PS and 500PS units, but this far has not been tried out in a 52PS. The reason others have not tried this approach is simple-there are no other chokes available anywhere that come even close to having such high Henry amount with high current handling.

You can for instance get some 15H Hammond chokes, but they can only handle a fraction of an amp and have DCR in the hundreds of ohms. I did try one of these out AFTER the voltage regulators in a PS for the Prefix, but this was NOTHING compared to using a high current choke between the rectifier and the filter caps on the same supply. Chokes love to have as decent amounts of current before they actually start doing their job-which also has the added benefits of extra energy stores, that approach the amount that the filter caps can store. For instance....the XPS light now takes about 18 seconds to extinguish after powered down-before chokes it was within a fraction of a second.

The other thing is cost-given that it takes close to 10 hours to hand make each choke, these would have to sell for around $500 USD a piece. Still not bad compared to the gains to be had.

I would also be tempted to replace the aging (and not so great) VR boards in the 52PS with something much better than the Naim ones-the RSL boards I am sure will be more than up to the job. Avondale also do a set of Supercap VR boards too.

If you lived in the US, having a pair fitted (internally or externally) would be no problem. But the chances are very good that you do not.
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