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Feedback capacitors for Naim power amplifier.

guy said:
As far I read in the forum big improvements can be achieved
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Could I please ask what you mean by "improvements"? Do you mean improvements along the lines of it sounding like a more expensive Naim amp? Or better in the sense that you don't like the Naim sound and so you'd like to stop it from being that way?

The film cap suggestions given here will certainly stop the Naim sound. But if you wanted to do that, then why would you have bought a Naim amp in the first place?
 
I was not the OP, however as I've revived this topic, my answer is:
I guess as I have got older, my requirements have changed. I am now finding the 250 somewhat tiring to listen to for an extended period. To try to put it into perspective, I have a Bose standalone cd player, which is definitely not what would be regarded as 'hi Fi' but it's certainly easier on the ear. The 250 and hi cap have been recapped, the 32.5 has Avondale 821 boards, hicap has TPR4. I'm looking for the sound to be more 'fluid or 'organic' Not 'In your face'. If I can achieve this by changing a few caps, then it's all to the good. So yes, I'm probably wanting to move away from the Naim sound, but how to do it while retaining my existing kit?
 
Arkless Repairs said:
You don't maybe mean solid tant axials as opposed to sintered bead tants?

Wet tants are silly money! Like £100+ each for 100uF and above! A 12,000uf 75V wet tant is around.... £750 each!
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Jez
No I dont mean the solid tantalum, As I quoted a Mil Spec Wet Tantalum cap and yes they are not cheap because they are so much better than solid tants, I use 82UF normally but 62uf would also be OK
http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=201952517730
http://www.vishay.com/docs/40056/40056.pdf
IMG_1651 by Alan Towell, on Flickr

Attached is the wet tants I use in the yellow sleeve as far as I remeber they were £20 each and I still have 2 left waiting for another special
addition of these amplifiers
Alan
 
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diybry said:
Thanks GWM, to clarify- Is it a 250 you re using the 150uF in? Everything I've read on here seems to say use 47uF as per the original spec?
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I have Naim boards,Hackernaps and NC200 boards from Les, they all have better bass with 100+ uF.
I have tried every combination you can imagine in feedback, for a full range amp wet tants are the best.
New ones a are ridiculous prices but demand seems to have pushed up the price on ebay.
There are solid axial tants that sound better than bead types that's what I have
In my NC it sounds pretty good they are the IT ones mentioned earlier.
 
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337alant said:
Jez
No I dont mean the solid tantalum, As I quoted a Mil Spec Wet Tantalum cap and yes they are not cheap because they are so much better than solid tants, I use 82UF normally but 62uf would also be OK
http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=201952517730
http://www.vishay.com/docs/40056/40056.pdf
IMG_1651 by Alan Towell, on Flickr

Attached is the wet tants I use in the yellow sleeve as far as I remeber they were £20 each and I still have 2 left waiting for another special
addition of these amplifiers
Alan
Click to expand...

Hi Alan, Yep that's a wet tant alright... Prices I'm quoting are for Mouser Electronics BTW.
 
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James Evans said:
I'm using these in my NCC amp and haven't felt the need to tinker. I think a few others use these as well?

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=311850150837
Click to expand...

Have you tried wet tantalum ?
It's the second time I have to change a wet one (109D) 'cause they fail causing large dc offset at output. I'm now using a bipolar (Muse) which are quite pleasant but shy at bass.
So, are these russian up to the level of bass quality wet give ?
If not familiar with wets you could just give more details about their sound
 
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ramona said:
Have you tried wet tantalum ?
It's the second time I have to change a wet one (109D) 'cause they fail causing large dc offset at output. I'm now using a bipolar (Muse) which are quite pleasant but shy at bass.
So, are these russian up to the level of bass quality wet give ?
If not familiar with wets you could just give more details about their sound
Click to expand...

It's a long time since I've swapped caps in and out so I can't remember at all I'm afraid. I was pretty much determined with this build (now 2 years old I think) to just fit and forget and if I didn't like it sell and move on. 2 years later it's still sat here and the only thing that's motivated me to change is the new Qudos boards from Les, that I'll also build with a pair of these Russian tants. Sound is incredibly personal, system and room dependent, but in my system I've never felt like I'm missing anything, and I really don't want to get myself back into the cap swapping frame of mind! (a possibly timely reference to the aspergers/autism thread in the off topic room...)

I've tried film caps in the past and know that I definitely didn't like them at the time, sounded detailed but sterile to my ears, lacking emotion I suppose. God knows what that means in objectiveland.
 
James Evans said:
I really don't want to get myself back into the cap swapping frame of mind! (a possibly timely reference to the aspergers/autism thread in the off topic room...)
Click to expand...

I surely understand what you're saying, I choose DC-coupled and DC-servo solution nowadays, maybe 'cause I'm getting older or the wallet is getting thinner.
Thanks for the info. Most probably I'll try them, don't feel like spending 50+ euros for a pair of 100uf 109Ds (Mouser). BTW, don't think that these caps ought to be matched perfectly.
 
My personal choice for input and feedback is the Russian PETP caps on ebay. I don't see the need for more than 47uf, that will give you -3db at approx 3.4Hz, I personally use 15uf to reduce cone flap playing vinyl for a -3db of 10Hz, my fhxl's start to drop off below 40Hz
 
Having ordered a couple of 100uF wet tants, I now understand that Naim used two 47uf in parallel to reduce the chance of failure.
CAn anybody please advise what the implications of failure are? Totalling my speakers is not a preferred option!
thanks
 
I wouldn’t worry about feedback cap causing problems the regulator board will shut down if the current goes over 10A or so.

Pete
 
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