NVA Amplifiers

bhobba

Before posting on this forum I hadn't heard of NVA amplfyers but they seem ot be very popular around here.  I am thinking of getting one out here in Aus for review and for people (of course including me) to check out.  Myself and most people I know prefer valve amps these days - how do people thing they would compare?

Also after reading up a bit on them the maker seems really keen on ensuring the amps are used with suitable low capacitance cables.  The cable myself and a number of my acquaintances use is Ribbonteck cables.  I think they are high capacitance but if anyone knows the ends and outs of this here is a link:

http://www.lenehanaudio.com.au/cables.php

Ribbontek Loudspeaker Cable: Capacitance - 0.41nf/ft

RibbonTek Interconnect Cable: Capacitance - 0.097nf/ft

My understanding is it may be a problem.  I would however be loath to get rid of these cables as they simply blow away any other I have heard.

Thanks

Bill 

uglymusic

Bill. I suggest you talk to @figlet108 (Jason) on this forum, who works with NVA.

Whether you like them depends what you like about valve amps. If you like soft, cushiony, valve amps, you're possibly in for a shock. NVA is very revealing, and plays rhythms with the drive of Naim, but with far more flexibility and subtlety.

I've had my top-of-the-range TDSs for something like 20 years, so I'm a real NVA nut. So maybe I'm not the person to listen to ;-)

bhobba

Bill. I suggest you talk to @figlet108 (Jason) on this forum, who works with NVA. Whether you like them depends what you like about valve amps. If you like soft, cushiony, valve amps, you're possibly in for a shock. NVA is very revealing, and plays rhythms with the drive of Naim, but with far more flexibility and subtlety. I've had my top-of-the-range TDSs for something like 20 years, so I'm a real NVA nut. So maybe I'm not the person to listen to ;-)

That is most definitely NOT the type of valve amp me and others I know like - the ones we like - such as the Leben - excel at being revealing and transparent.  In fact thats why I prefer valves - to my ears they are more transparent and revealing - I generally hear more details in them than transistor amps.

What I am more concerned about is that my speaker cables are rather high capacitance.

Thanks for the skinny on Jason - will drop him a line. 

Thanks

Bill

figlet108

Hi Bill,

I'm going on vacation on Tuesday so the best thing is to visit the hifisubjectivist forum and speak directly with Richard about sending you an amp. You can also ask about speaker cable capacitance.

thanks,

Jason

bhobba

I'm going on vacation on Tuesday so the best thing is to visit the hifisubjectivist forum and speak directly with Richard about sending you an amp. You can also ask about speaker cable capacitance.

Hi Jason

Thanks mate.  However since I am in no hurry will keep it on the back-burner for a while.

Thanks

Bill

Alan

HI Bill,

FWIW, people who have made the comparisons with NVA amps & 'better' valve amps have often expressed their view that NVA character is in no way "Solid State", and that the qualities they appreciate from their tube amps are also in evidence with NVA. I personally feel the 'weaknesses' of certain SS amps are not discernable with NVA, but they definately do not have a 'valve' character either.

I too appreciate NVA amps very much, having had a few of the range now. The company are generally very good to deal with too, especially given the 30 day money back trial period. That may not work so well with the shipping costs to Australia though!

Alan

A note on cables - NVA use low capacitance for a reason (hark at me the expert - I don't even fully know what capacitance is!). The output of these amps is unprotected, that is to say no zobel protection circuit or similar. Because of this lack of protection it is easy to short circuit them, which is an instant fail, so there is a 'thrill' (-not!) to changing cables or moving your kit around etc.

Cables with high capacitance or litz braided construction will make the unprotected amp extremely unhappy very quickly as NVA amps are not unconditionally stable like most amps are. This is all part of a design philosophy by Richard Dunn, which works very well when committed to fully. Their own cables are reportedly amongst the lowest capacitance on the market, and with NVA amps at least, are more than acceptable.

I am sure your cables are amongst the very best for your application, your system, but would be more than a disaster with NVA amps. This is not because it is bad cable of course, but simply designed for a different type of amplifier.

bhobba

Hi Allan

Fortunately, or unfortunately depending on how you look at it, I understand only too well exactly what capactance is and the issues here - I have a degree is applied math and an interest in how this stuff works.

Yes the high capctance cables I use may be a disaster with the NVA.  However if I get an NVA amp out here (and shipping is not that bad) I will get it checked out thoroughly by a very knoweldgabe tech out our way to ensure no problems of that type occur.  If it does then other cables will be used that are of known low capacatance.  That said my gut feeling is it won't be a problem.

Thanks

Bill

Alan

OK Bill, that's fine, You seem to have it all sorted clearly in your mind, and are fortunate to have a like-minded group around you for support. What do I know? By my own admission not a lot....But I have been regurgitating to you directly what I have been told by the designer of NVA amps (before he decided I was the spawn of the devil!) - You don't have to take heed at all, but I wonder why you asked the question if you already have decided the answer!

I simply offered advice to you based on what little I do know in order to save you a blown amp and also to save RD the hassle of fixing it!

bhobba

You don't have to take heed at all, but I wonder why you asked the question if you already have decided the answer! I simply offered advice to you based on what little I do know in order to save you a blown amp and also to save RD the hassle of fixing it!

Sorry - I expressed what I wanted to say poorly.   Rereading it I can see how I came across as a smartarse - which was not my intent.  Your comments reinforced what I had read and the fact it came from the designer indicates how important it is.  Please accept my apologies for basically behaving like an idiot.

Your advice is appreciated and because of it I will be taking the precaution of getting it checked put by a tech out my way.

Sorry

Bill  

Alan

Bill - now I feel bad! Perhaps I was a bit harsh in what I said. I don't think you're an idiot at all, and I'm glad you're posting here.

I was partly interested in imparting the warning about cables to you because the NVA designer is so damned prickly....if you blow anything up he'd likely blame the mods here on audiochews! He can be hard to deal with, but he does make very fine equipment (imo).

bhobba

Hi Alan

No problems mate.  In fact it piqued my interest enough to reacquaint myself with what Zobel networks on amp outputs do for stability.  The issue is the capacitance and inductance in the loudspeaker cables forms a transmission line resonant circuit.  If the resonance is in the region that the driving amp, due to phase shifts from time delays etc in the amp, leads to positive feedback - it can and often will oscillate. That's where the Zobel comes in - it consists of a capacitor and series resistor in parallel with the output.  At high frequencies the capacitor is an effective short so the resistor is in parallel with the speaker cable - this effectively lowers the Q factor of the series resonant circuit the transmission line is equivalent to so it is no longer a very high impedance (and hence can develop a high voltage) at that frequency making it much harder for the amp to oscillate.

Ok the bottom line here is if the resonant frequency of the speaker cables is much higher than the amp can operate at it will not oscillate.  High values of capacitance and inductance lower the resonance and causes problems if you have a wide bandwidth amp - so you need a zobel.  However large capacitance by itself is not the issue - its large capacitance in conjunction with large inductance - thats the real problem.  If your cables have low inductance then it is not a problem - even if you have high capacitance.  While the Ribbonteck cables have high capacitance they have a compensating low inductance so may be OK.

Thanks

Bill

uglymusic

Why not just use the recommended NVA speaker cables, Bill?

LS5s, in particular, have a very good reputation amongst non-NVA users.

bhobba

Why not just use the recommended NVA speaker cables, Bill? LS5s, in particular, have a very good reputation amongst non-NVA users.

Because I already have the Ribbonteck cables and they are by far the best cables I, and others I know, have heard.  They have been compared to plenty of cables, including some sickeningly overpriced $10K jobs, and nothing even comes close.  They are that good.  I will go out on as limb here and say they are likely the best cables in the world regardless of price.  I would be very peeved if for some reason I could not use them.

Thanks

Bill

uglymusic

I'd be very surprised if they're the best for every amplifier/loudspeaker combination in the world, but be that on your own ears :-)

bhobba

I'd be very surprised if they're the best for every amplifier/loudspeaker combination in the world, but be that on your own ears :-)

Sure.  But I think you can understand now that I found something that does it for me I am loath to change.

Thanks

Bill

uglymusic

I'd be very surprised if they're the best for every amplifier/loudspeaker combination in the world, but be that on your own ears :-)

Sure.  But I think you can understand now that I found something that does it for me I am loath to change.

Thanks

Bill

Yes, I can. I guess we all do that through our choices of gear, but I think we all have to be careful of getting sucked into hyperbole such as 'the best amp', 'the most transparent interconnects' or 'the biggest PRaT' (well, maybe not that one). IMO, it's not realistic because a hi-fi system is more than a single component and we hang something even more complex on the end of it - a human, with ears and a brain - in a sub-optimal acoustic environment.

Alan

On the subject of best speaker cables known to Alan, I am curious about these Tellurium Q cables....but that is another topic!

Gingernutt

As a passing nva convert, i thought I'd ask advice here.
I have an nva p90 pre amp which drives me wild adjusting the two volume controls.
Though maybe part of that's my fault from where it sits, below the deck.
Wwould converting to a p50 sa be a backward sideward or forward step?
Any opinions?

Thanks
Al

Alan

Hi Al

I had a P90 & know what you mean, but I never did try the P50sa. I have read it is better, but the P90sa is da bizznizz. Docfoster uses one, and I should imagine it is about as good as any passive will ever be - but it is dear. My feeling is the P50sa would be better than a P90sa in some ways but not necessarily all....non-committal? Moi?

Have you tried asking over at the HiFiSubjectivist forum? Richard Dunn, Mr NVA, runs the place and it is basically the manufacturer forum. Plenty of user experiences there.

Docfoster

The P90SA is luverly. Better than the standard P90.
I seem to remember someone asking the same question re. P90 v P50SA on the hifisubjectivist a while back. Can't remember the answer tho... Damn ageing...
You could probably find it on the search function there, or, as Alan suggests, just ask there again.

TimJ

I remember the answer as I was trying to decide what to go for at the time. The stepped attenuator pres should give better dynamics and a bit more presence than the regular (Alps? P&G?) ones. But the dual volumes give better stereo. So a regular P90 will have slightly better stereo separation than a P50SA, whereas the latter will have sound a bit more dynamic. Or something like that. Obviously a P90SA will have both advantages.

I'm not sure I could live with a regular P90 as the channel matching would drive me bonkers. A P90SA might be a different proposition, as you'd know how many clicks to turn each pot for the same level. If you see what I mean.

Anyhow, I'm loving my P50SA.

Docfoster

Well done Tim. :-)

uglymusic

Hi Al

I know this is not directly answering your question, but what is the rest of your system? I have the twin volume controls on my Statement Pre, but just set it and forget it and use a digital volume control. The one in Audirvana plus.

Jim

As a passing nva convert, i thought I'd ask advice here.
I have an nva p90 pre amp which drives me wild adjusting the two volume controls.
Though maybe part of that's my fault from where it sits, below the deck.
Wwould converting to a p50 sa be a backward sideward or forward step?
Any opinions?

Thanks
Al

Interesting how we all behave.  I have used separate left and right volume for years and really struggle when faced with only one.  I'd never change.

Jim

I've just remembered an old trick. Get a wide elastic band and stretch it across both knobs. If it's tight enough you should be able to turn both by just turning one if you see what I mean.

uglymusic

I've tried that with my friend and we're both in agony  :O X( @-)

Docfoster

Jim, your elastic band idea could just be the start.
Look here some guy has rigged up a remote volume control using an elastic band and an electric motor device. So 2 elastic bands one could be the start of a dual mono volume remote control system...



I suppose with enough elastic bands one could connect to the electric hob, electric light dimmer switch, tin openers... the list could be endless. One need never leave one's seat again.

Jim

I've tried that with my friend and we're both in agony  :O X( @-)

I'm surprised it took you an hour and a half )

uglymusic

Please sir, I have an excuse. I bin taking my poorly computer to see the nice man at the Apple Store  :-h