Preampli Passivo


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NVA England




390 circa



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Description Passive pre-amplifier

Controls - Volume and source select

Inputs - Four line level and direct

Outputs - Three pairs of `pre-outs' for single / bi / tri amp support - plus tape output

Dimensions - 250mm x 70mm x 210mm (whd)





Why go passive?

With the increasing use of CD as primary source, the need for traditional pre-amplification recedes. Line-level sources such as CD, tuner and tape normally have sufficient output to drive power amplifiers. All you then need worry about is the number of inputs provided since a passive preamp is simply a potentiometer placed between the source component and the power amplification.

Proponents of passive preamps point to their simplicity; those who argue for traditional active preamplifiers point to potential difficulties interfacing passive preamps with certain kinds of interconnect cables and power amps which may present the wrong electrical characteristics. There is truth in both arguments. NVA claims to have been one of the first manufacturers to market a passive preamp way back in 1983. Interestingly, the development was not driven by the widespread usage of CD, as the date might imply: according to NVA's owner and designer, Richard Dunn, `It has always been our view that circuitry should be kept as simple as possible. We developed a passive simply because it offers better sonic performance.'

When NVA switched to a passive preamp (with phono stage, of course), the company also changed the input stages of their amps to offer the correct load to the potentiometer.

NVA's P50 is built into a Perspex box, epoxy glued together - NVA is part of the school that believes magnetic boxes are a bad thing - that most people either love for its solidity, or hate for its Spartan simplicity. And, by gluing rather than screwing, even the tiniest eddy currents are eliminated.

Inside, there's no circuit board, just a potentiometer, a high quality switch and some expensive silver alloy wire.

The other main design aim was to provide good earth paths. Ground plane earthing is used, which the manufacturer believes is superior to the more fashionable star-earthing used in many better known amplifiers.


Over a period of several weeks I used the P50 preamp and a nva Phono 2 head amp both within this system and with a variety of source and amplification components from other manufacturers. The final listening session took place using an Arcam Delta 170 CD transport with Micromega Duo BS converter, and my regular Linn turntable, the NVA power amplifiers driving Naim SBL loudspeakers. I think it's fair to report that overall `the amp done good!'

It's obvious listening to the NVA combination that the company's design philosophy is based on information retrieval. That's not to imply that there's any lack of cohesion or musicality in the amplifier's presentation, simply that the P50 scavenged all the minutiae you can imagine. With a good Compact Disc player upstream, one that was able to reveal nuances and low level information, the P50 gave a graphic account of what was present on discs. It was similarly dextrous when handling dynamic variations in the music.


- For information on nva go to -

NVA's Overall Philosophy

Generally, we have never been keen on producing conventional literature, because it's usually just glossy expensive paper full of pretty meaningless specifications which have little bearing on how good the sound of audio equipment is when playing music. If you buy hi-fi equipment on the basis of what a manufacturer says about himself (including us!) you really do deserve what you get.

As an alternative, one of our dealers suggested that we try to explain good design and how to recognize it. People probably won't believe this, but really the basics are very straightforward. A famous British amplifier designer is supposed to have said, "Good amplifier design is not the things that you do right, but the things you don't do wrong". I really wish I had said it first, because it's amplifier design in a nutshell. You can come up with all the new circuit configurations under the sun such as feed forward, low feedback, class A to Z, but ignore the common sense ground rules, and you will have a sonic bag-of-nails capable of being blown away by a couple of EL34's in a 1950 Williamson tube circuit. I am afraid 80% of the amplifiers built today fall into this category. The thing that never stops amazing me is that so many audiophiles keep falling for it. There is nothing like a good story to have people hocking the next three years' spare income on the latest all-singing, all-dancing creation. Not only that, a good story sells magazines as well, which just exacerbates the problem.

Here are my ground rules:

1. There is only one thing better than the best component money can buy, and that is no component at all.

2. Never use two components when you can do the job with one.

3. Screw up your earth (ground) paths at your peril.

4. Always use the largest transformer (toroid if possible) you can cost in.

5. If your ears and your test equipment tell you two different things, trust your ears.

6. If you have a fault in your source material or elsewhere in the equipment chain, you cannot correct it by creating an inverse fault in the amplifier with tone, balance, and filter controls. Two wrongs do not make a right.

After that it is all down to experience, and fine-tuning the design to your own taste. It is easier to get a half-way decent sounding amp using Vacuum State Logic (warm glass bottles) than Solid State Logic (hopefully cool lumps of plastic) because there is less to do wrong (Neanderthal Logic). That is why so many people have jumped on the valve bandwagon. All things being equal, bits of doped silicon encapsulated in metal or plastic (transistors) potentially are capable of doing more things with music, i.e. wider (frequency), larger (amplitude), cleaner (distortion and noise) for less cost. Remember though, the more you try to do, the exponentially easier it is to do it wrong.

If you can get most of it right, then think very carefully before you try to get the very last bit, because you may be too clever and ruin everything you've gained thus far.

This explanation is all very simplistic of course, and common sense and experience must apply as well. For example, a Class A circuit is a lot simpler that the equivalent Class B or AB. Ergo, applying my logic it should be better. Wrong, unless you spend a fortune on the power supply, which then makes the amplifier grotesquely expensive and heavy. The problems of current demand by the amplifier outweigh the simplicity. If I could buy 1000VA transformers not larger than 4" square, and weighing less than two pounds for 10, and if I could get good and consistent output transistors (i.e. not FETs) that could sink 20 amps, and either, not get hotter than 70 degrees C doing so, or stand 150 degrees C without going into self-destruct mode, I would produce Class A amplifiers. I will not produce them just because they have become some reviewers latest buzz word.

Every amplifier has its own sonic character, which is very much down to the musical parameters that are most important to the designer. The process is very much "lose on the swings, gain on the roundabouts". I once knew an amplifier designer, in fact I employed him back in Tresham Audio days to produce a professional FET power amplifier, who saw no necessity for listening to the amplifier at all. It was only after he left, and some ears were applied to the design that it started to sing, not as much as the best hi-fi amplifiers, but it went very loud and was virtually indestructible.

My greatest hang-up is information retrieval - musical information, especially dynamic separation. I will always go for information even at the expense of upsetting the "make everything bounce and swing with the tempo" brigade. My other priority, which seems to be out of favour at the moment, is neutrality, or as I prefer to call it, lack of the irritation factor.

Richard Dunn, Founder and Owner, NVA
















Pre adatto a chi ama il proprio finale e non vuole modificare il suono che ne esce..



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