NVA and Speaker Cable Safety
For best sound, NVA amplifiers should be left powered-up indefinitely, because energy consumption is very low for this Class AB circuit. It is for this reason that the power switch is located on the back panel, where it may not be easy to reach. Please switch the amplifier off when you do not intend to listen to it for extended periods.
As you probably know by now, NVA amplifiers are unique, and one thing that makes them so is the minimal compensation for the output stage. It is possible to send the amplifier into oscillation by connecting too large a capacitive load on the output, the usual culprit being unsuitable speaker cable, or electrostatic speakers with low impedance at high frequencies. Normally, the amplifier will run very cool indeed, but if it becomes unstable, the output transistors will become warm or even hot. (The exception is the AP10H which doesn't have output transistors but a warm frame transformer, and the AP10 Personal if you continually drive it too loud into speakers) You can check this by placing your hand under the bottom of the amp and searching for hot-spots (the output transistors are attached to the base) if the sound becomes distorted or unusual in any way. If you do find a hot-spot, turn the unit off at once, and consider whether you are using low-enough capacitance speaker cable.
Never bi-wire your speakers with this amplifier. Bi-wiring doubles the capacitance of the speaker wire if you use the same cable for woofer and tweeter. Consider acquiring some NVA LS1 speaker cable, which runs only about 20pF per meter (7 pF per foot), and which will in any case wake up virtually any system into which it is placed, because it is very good.
Listed below are acceptable speaker cables. If cables other than these are used, our guarantee will be invalidated.
* NVA LS1
* Nordost (all types)
* DNM (all types)
* Q cable (all types)
Audio Note AND & AND 70
Audioquest F-14, F-18 and Argent
Cable Talk 3 and 4
Chord Company Rumour and Myth
Ixos Hardcore 6 and 12
Monster Cable XP
Naim NAC A5
Ortofon SPK100 & SPK300
Silver Sonic T-14
Sonic Link Care Music Cable
Supra Cable 10
Van den Hul Revolution & CS122
XLO Pro Type 625, 0.6 and Pro 600
If a cheap starter cable is required then use Twin and Earth solid core mains cable from a hardware store.
Only the cables with a star are recommended for sonic performance and
value by NVA. The remainder are electrically compatible and may prove suitable
in your system, but have not been assessed sonically. As a rule, avoid
cables of more than 200pF per meter (65 pF per foot) as an outside limit.
Also, speaker cables should not be over 10 meters (33 feet) in length.
Pre-assembled NVA amplifiers are warranted against manufacturing and parts defects for a period of three (3) years from date of purchase. There is also a 30 day money back guarantee if you do not like the product for some reason. It must be returned in as-new condition, and will be examined to ensure that this is so. The three year guarantee assumes you have read and understood the warnings included with each purchase regarding proper selection and use of speaker cable required by the amplifier. Output transistors can be destroyed by improper use of unsuitable loudspeaker cable or by shorting the outputs, so we may not be too tolerant of claims that involve blown transistors. The parts used are of high quality and fail infrequently, but that does not mean it never happens. This is the real world. Contact us at the address given below for assistance in returning the amplifier, and we will do our best for you. Remember to insure the amplifier when shipping, because we cannot be held responsible for damage sustained in transport. You are responsible for shipping costs incurred to get the amplifier back to us.
NVA amplifier kits are sold with a money back guarantee for 30 days from date of purchase -- valid reasons for return include your not liking the product for some reason, or that you are simply unable to put it together properly and do not want to continue. Naturally, we will examine the returned product for any damage that would reduce its value, including, but not limited to scratches and blemishes, overheated parts due to poor soldering techniques and so on. After that, we warrant the product for a total of one year from date of purchase on the conditions mentioned above for pre-assembled amplifiers. Why not three years? Well, because we can never be sure how well you put it together. Please contact your local distributor before returning any product, and obtain a Return Authorization Number. This helps us and it will help you because we should be able to handle things more rapidly -- i.e. the refund. Insure the amplifier against shipping damage as mentioned above for pre-assembled units. You are responsible for shipping costs incurred to get the amplifier back to us.
Also, with a kit amplifier, it may happen that you make some serious errors building it, and want us to sort it out for you. That we will gladly do, but there has to be a charge based on NVA's experience around the world. As it mentions in the assembly instructions, we can bring the amplifier to health for a fee of £50 + Carriage + VAT.
In later years as your NVA amplifier gracefully ages, it may require some care and attention. We will be happy to do that for you, so contact us for assistance in solving your problems.
We have tried to write this guarantee in simple wording that is clear
to one and all. We are not trying to limit your rights in any way, and
we want you to be satisfied with your purchase, so we will try to be fair.
The warranty is transferable for pre-assembled units, but not so for kits.
Please present your original invoice as proof of purchase if asked to do
so to gain warranty service.