Nap 500 just a thought.....

Yes, we tried this at the factory many years back.  In some ways it give quite a dramatic change in the performance, one that's initially quite exciting - bigger, wider soundstage and seemingly more airy - but you then realise it's not as cohesive and a bit less natural too - less all of a piece.  I guess you'd say it's a bit more hyped but less musically coherent.  On pondering as to why, I vaguely recall Roy speculating that the "parasitic effects" (?) of having half each PSU unused (where never designed to be so) might be the reason for this.

I think Ron has tried similar tests in the States, so maybe he will post his recollections.  Otherwise, ry a forum search on some old posts on this subject.

Hi thanks for replying  Richard wow that's interesting ..... I did wonder about 1/2 torroid not being used etc. I am suprised Naim don't offer reengineered supplies in two boxes with redundancy dropped. This would make it like a mini statement....in theory....  I can't see this happening .... allot of r&d and it may get too close to statement!!!

So is the same not true for those of us who drive our NDS's with two 555PS's ?   Or is the 555PS different in basic design from the 500PS?  (worried look)

RJ, the 555PS is different in design to the 500PS, so no need to worry.

Except, Richard, that "one that's initially quite exciting - bigger, wider soundstage and seemingly more airy - but you then realise it's not as cohesive and a bit less natural too - less all of a piece." is exactly what I have heard on NDS with two 555PS... spooky :-)

...and maybe with two 555PS on a 555.

There is very little (????any) difference between using two 500PS into one 500 head unit and using two complete 500 units and driving only one channel of each. The first guy I know to try this (onthlam) had a custom made Burndy that allowed front panel lights to come on (it is powered by only one of the Burndys) and then used only one Burndy from each 500 to its companion power supply. With DBLs he reported a very large improvement over using a single conventional 500. 

Another of my DBL owning friends also tried it, using two 500's as pseudomonoblocks and again thought it was a very substantial improvement. 

The 'weakness' of the 500 is that the channels share a common toroid transformer and as such are not true dual mono internally. 

The theoretical advantages of using two 500PS into a single head unit is that there is better matching between  L and R channels than would be obtained from a single head unit than with  two randomly selected 500s repurposed to this use. 

The potential benefits in doing so are probably much larger than using 2x555PS, as in the 500's case, there is actually some serious current being shifted with the 500 instead of a few hundred milliamps in the case of the 555PS, and the extra burden on the power transformer  by sharing channels with interchannel modulation becomes a real problem in power amps. 

I have a sneaky feeling that if those tests be reran today using 500DR and the Statement preamp, there would be an overwhelming preference a dedicated PS per channel. This unfortunately take a 3-way active system from a 6-pack to a 9-pack in terms of black boxes required to power the drivers. Or if you wished to use a single head unit and a single PS per channel, a 12-pack. Which ironically seems less OTT than when I first heard of  6x135 powering Isobariks. 

It is no accident that people have used 110 power amps as pseudomonoblocks and in every case reported a large improvement. 

Plus being able to use 500 head unit with 2x 500PS would be a great step up for those who would like to move up from the 500, but cannot quite reach to the Statements. Makes perfect marketing sense too. You probably would find that everybody who preferentially uses 2PS on the 555 or the NDS would also love what 2 PS would do on the 500s. And if that isn't marketing low-hanging fruit, then I do not know what is. Surely this is worth a punt again....any body out there willing to try??

jon honeyball posted:

Except, Richard, that "one that's initially quite exciting - bigger, wider soundstage and seemingly more airy - but you then realise it's not as cohesive and a bit less natural too - less all of a piece." is exactly what I have heard on NDS with two 555PS... spooky :-)

I wouldn't agree to that. I have heard the two 555PS setup at Naim and it sounded much more natural - the character of the instruments shines really through....

I would, fund permitting, never doubt such an upgrade...

Ron Toolsie posted:

There is very little (????any) difference between using two 500PS into one 500 head unit and using two complete 500 units and driving only one channel of each. The first guy I know to try this (onthlam) had a custom made Burndy that allowed front panel lights to come on (it is powered by only one of the Burndys) and then used only one Burndy from each 500 to its companion power supply. With DBLs he reported a very large improvement over using a single conventional 500. 

Another of my DBL owning friends also tried it, using two 500's as pseudomonoblocks and again thought it was a very substantial improvement. 

The 'weakness' of the 500 is that the channels share a common toroid transformer and as such are not true dual mono internally. 

The theoretical advantages of using two 500PS into a single head unit is that there is better matching between  L and R channels than would be obtained from a single head unit than with  two randomly selected 500s repurposed to this use. 

The potential benefits in doing so are probably much larger than using 2x555PS, as in the 500's case, there is actually some serious current being shifted with the 500 instead of a few hundred milliamps in the case of the 555PS, and the extra burden on the power transformer  by sharing channels with interchannel modulation becomes a real problem in power amps. 

I have a sneaky feeling that if those tests be reran today using 500DR and the Statement preamp, there would be an overwhelming preference a dedicated PS per channel. This unfortunately take a 3-way active system from a 6-pack to a 9-pack in terms of black boxes required to power the drivers. Or if you wished to use a single head unit and a single PS per channel, a 12-pack. Which ironically seems less OTT than when I first heard of  6x135 powering Isobariks. 

It is no accident that people have used 110 power amps as pseudomonoblocks and in every case reported a large improvement. 

Plus being able to use 500 head unit with 2x 500PS would be a great step up for those who would like to move up from the 500, but cannot quite reach to the Statements. Makes perfect marketing sense too. You probably would find that everybody who preferentially uses 2PS on the 555 or the NDS would also love what 2 PS would do on the 500s. And if that isn't marketing low-hanging fruit, then I do not know what is. Surely this is worth a punt again....any body out there willing to try??

I'd be in... if available.

tonym posted:

...and maybe with two 555PS on a 555.

Yes, thats what I thought Tony. The two PSU's were initially very exciting and seemed better, however reverting back to a single PSU brought the musicality back. I also thought two PSU's lacked timing!

Hi this is a very interesting thread ........ Polarbear ... has raised a good point .... years ago my brother used to build the amps at Heybrook ... they at the time had the C2 pre & P2 power amps. They experimented separating the supplies for each channel and did blind tests - they found that that the twin supplies sounded open and very detailed but curiously diffused. The mono supply in their opinion sounded more cohesive and tuneful........... just thought I would throw this in.

jon honeyball posted:

Except, Richard, that "one that's initially quite exciting - bigger, wider soundstage and seemingly more airy - but you then realise it's not as cohesive and a bit less natural too - less all of a piece." is exactly what I have heard on NDS with two 555PS... spooky :-)

Pretty much my experience too.  2x555PS did something unpleasant with the HF.  Hard to describe just not very nice.

Maybe we should try to S1 preamps, one for each channel

I remember asking one of the top people at Naim about this when the amp was launched. The answer I got was as Richard described. However, the explanation was that in the case of the 500, using 2 supplies destroys the signal earth arrangement, causing a tiny potential difference between the earths and thereby losing the cohesion of the music.

Yes, long time ago...

Frank.

Richieroo posted:

Hi this is a very interesting thread ........ Polarbear ... has raised a good point .... years ago my brother used to build the amps at Heybrook ... they at the time had the C2 pre & P2 power amps. They experimented separating the supplies for each channel and did blind tests - they found that that the twin supplies sounded open and very detailed but curiously diffused. The mono supply in their opinion sounded more cohesive and tuneful........... just thought I would throw this in.

Thats right Richieroo. I have run two 500's side by side in mono configuration and the result was very enjoyable. 

Great thanks for this ... I thought it may be a complex earthing issue ...... I suppose in theory it could be sorted...but then that would no longer be a 500.....  anyway they are still amazing amplifiers!