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  Frequently Asked Questions


Part 1 Technical

Q: Q: I have a problem / Technical question....Who should I contact?
Q: What’s the difference between balanced and unbalanced connections?
Q: What’s the difference between transformer balanced and electronically balanced stages?
Q: Should both ends of the Input / output connection be floating
Q: How does Nagra select 845 tubes?
Q: What is the life expectancy of your tubes?
Q: Why does Nagra no longer delivers 845 KR tubes?
Q: Will Nagra offer other types of 845 tubes on the VPA?
Q: Can I use 211 or 242 triodes on the VPA?
Q: Should I buy a VPA or a MPA?
Q: What’s the difference between the PL-L and the PL-P?
Q: What is the advantage to use a battery in a preamplifier?
Q: Why doesn’t the PL-L feature an internal battery ?
Q: In the DAC, what does the Adaptative Time Filtering brings to my music?
Q: Is the DAC ready for SACD or other high definition formats ?
Q: Does Nagra recommend a specific loudspeaker brand?
Q: Can Nagra amplifiers accommodate any loudspeaker?
Q: Does Nagra recommend specific cables?
Q: Can I connect any source to my Nagra preamplifiers?
Q: Where Nagra products are manufactured?
Q: What are the final quality controls ?
Q: Does my NAGRA conform to the CE norms?

Part 2 Sales

Q: I can’t find a distributor in my country, what should I do?
Q: What should I expect from a Nagra dealer?
Q: Should I buy a Nagra product in my country?
Q: How can I know more about a second hand Nagra?
Q: What is the link between Nagra’s Hi-Fi and pro products ?

Part 1 Technical

Question: What’s the difference between balanced and unbalanced connections?
Answer: In physical terms, a balanced connection consists of a three terminal connection having a “High” and “Low” for the signal and an independent ground (Generally in XLR connectors). An unbalanced connection is a two-pole connection where the signal “low” and ground are connected together and the signal “High” is on the other terminal (Generally “Phono” or “Cynch” connectors.
Designing a high quality symmetrical output is an extremely difficult task, which, increases the cost of the output stage, offers no audible advantages, and no technical advantages, other than elimination of an AC mains loop. It is for these reasons, the outputs of the PL-P (like the majority of pre-amplifiers) use an asymmetrical “unbalanced” output through high quality gold plated RCA connectors. On the other hand, a High quality symmetrical input stage is a perfectly straight forward development, and it offers better isolation from noise than an asymmetric input, especially when the source is not located close to the amplifier, usual in the professional domain.

Q: What is the relationship between “balanced” and “floating” connections?
A: A Balanced signal has one phase of the signal on one wire (Phase +ve on High) and the opposite phase on an other wire (Phase –ve on Lo). Electrically speaking, the ground or reference point is the chassis of the amplifier (or other equipment). Such connections do not remove the possibility of an AC loop between two pieces of equipment, which may create persistent hum on the loudspeakers. In order to break such a “loop”, in addition to the balanced connection we need to be “floating”. In other words, an independent signal earth/ground connection between the equipment must be installed. There are two ways of achieving this: a transformer in the signal path, or an electronic floating stage (Input or Output).

Q: What’s the difference between transformer balanced and electronically balanced stages?
A: A balanced input or output using transformers provides true isolation (known as galvanic isolation). Electronically balanced stages avoid the inherent weaknesses introduced by transformers, but the amplitude of the hum loop to be isolated (common mode) is limited by the amplifiers supply voltages.

Q: Should both ends of the Input / output connection be floating?
A: No, it is perfectly sufficient to leave only one end floating. Generally speaking it is far easier to make an electronically floating input than an electronically floating output for manufacturers. Therefore, be careful to check if the manufacturer specifies a symmetric and floating output on a piece of equipment or simply symmetric, as this confusion can create severe distortion.

Q: How does Nagra select 845 tubes?
A: After a 24 hour burn-in and individual measurements on a custom Nagra benchmark amplifier, they are matched by pair and attributed to a specific VPA amplifier. The VPA is then checked to make sure the tubes meet our quality requirements, both electrically and subjectively in our listening room.

Q: What is the life expectancy of your tubes?
A: This is a very difficult question. Some PL-Ps that were returned to us for routine maintenance with 5000 hours of operation, showed tubes to be in excellent condition. These PL-Ps had exactly the same specifications as when leaving the factory as new.
So the usage timer does not necessarily indicate the need to change the tubes. An audible degradation is a much better indication (distortion, clicks and pops and hiss).

Q: Why does Nagra no longer delivers 845 KR tubes?
A: After numerous experiments and tests, we have come to the conclusion that the current 845 tubes manufactured by KR Audio, no longer comply to the original 845 specifications. We can not predict how these tubes perform in our VPA amplifiers.


Q: I have a problem / Technical question....Who should I contact?
A: Please contact your nearest agent / dealer (See Sales Network). If there is no dealer or agent in your country / region, please contect us directly in Switzerland via the "contact us" form and we will do our best to help you.

Q: Will Nagra offer other types of 845 tubes on the VPA?
A : At this time, the 845 tubes we are delivering meet our technical expectations and are available in large quantities and at a consistant quality. However, in a continuous effort to improve the quality of our equipment, we are still looking for alternate choices.

Can I use 211 or 242 triodes on the VPA?
A: Yes, 211 or 242 tubes can be installed in place of 845 on the VPA. The plate current should be readjusted and, in principle, there is no risk for the tube or for the amplifier. The sound will be good up to approximately 15 to 20 watts, but above that the distortion will rise quickly and reach an audible level.

It is important to keep in mind that the VPA is optimized to operate with 845 triodes.

The 845 is a real triode which operates in the same manner throughout the entire range of usual grid voltages. This tube never operates with positive voltage and a grid current. In consequence, we have created a driver which is able to provide the large signal amplitude needed to drive this low gain tube (approximately 5). The 211 and 242 have a better gain (approximately 10) but they are very hungry in terms of grid current because they have to operate in positive grid voltage. In this area, they behave more like a penthode.

Q: Should I buy a VPA or a MPA
A: While being very different in the design, the VPA and the MPA are both exceptional amplifiers. The VPA is based on 845 tubes polarized in A class and will deliver 50 W. The MPA is based on MOSFET transistors using a very specific Nagra design. The MPA will deliver 250 W (on a 8 Ω load).

The choice depends on your personal taste, musical habits and the sound pressure level (SPL) you want to achieve basically depending on your speaker’s sensitivity and the volume of the room.

If your speakers have a typical 90 dB SPL / 1 W / 1 m sensitivity, then the maximum average level using the VPA would be 107 dB SPL, and 114 dB SPL at 1 m distance from the speaker, using the MPA. Keep in mind; this is not the maximum level on transient signals but the level you could maintain without distortion. To make a comparison, the average level in a movie theatre is 85 dB SPL in the middle of the room.

Every 6 dB step, the sensation of sound level is doubled. The power difference between the VPA and MPA will result in a 7 dB shift in the sound pressure, that’s more or less twice the sound level sensation.


Q: What’s the difference between the PL-L and the PL-P?
A: The PL-L is a tube line preamplifier with a remote control, it has an optional balanced output (with Nagra custom made transformers). The PL-P is a tube line and phono preamplifier operating on batteries. It has unbalanced inputs and outputs and no remote control.

Though they look similar, the PL-L and PL-P have a different internal design. Let’s consider all other aspects than the audio quality, which may influence your personal choice:

The PL-L and PL-P offer different features, maybe the first question to consider is whether you need a phono preamplifier?

If you only need line inputs, the PL-L would seem a better choice, and it offers a remote control and an optional transformer balanced output.

Q: What is the advantage to use a battery in a preamplifier?
A: The PL-P has been designed with an internal battery because of the phono stage. A phono player has a low level output and is therefore more sensitive to hum. So, phono preamplifiers need to operate with very low noise floor. To achieve this, the powering unit also needs a low noise level. In certain regions, the mains power network suffers from severe interference and variations. In such cases, battery operation allows a quietness you can’t expect from other standard powering units.

Q: Why doesn’t the PL-L feature an internal battery ?
A: A clean power supply is especially important when dealing with low level signals. A phono (record) player delivers signal with amplitude in mV, whereas most CD players deliver up to 1 V which are considered to be a “line” level. So signals fed to the PL-L are higher than those to the PL-P, so the use of a battery is less critical. However, if you wish to use a battery on your PL-L, you can plug a 12 V battery onto the Lemo connector. A Nagra service center will provide the cable and advice needed.

Q: In the DAC, what does the Adaptative Time Filtering brings to my music?
A: The Adaptative Time Filtering feature allows the digital to analogue converter to be isolated from the clock of the incoming signals. This means, whatever jitter the source has, the DAC will keep a clean stable output. As the jitter is a great source of quality loss in digital systems, the use of a DAC will improve the sound of your system.

Q: Is the DAC ready for SACD or other high definition formats ?
A: The DAC already accepts 192 kHz / 24 bit signals today!
So SACD’s bit rate is compatible with the DAC. Unfortunately, the SACD players do not offer a digital output, mostly due to copyright protection. When this digital link is officially standardized and available to all manufacturers, Nagra will evaluate the possibility to upgrade the DAC. A hardware modification would be needed to decode the DSD stream. Still, it is worth having an exceptional DAC to convert your favourite CDs.

Q: Does Nagra recommend a specific loudspeaker brand?
A: Nagra amplifiers are recognized for many qualities. One of which is the ability to drive even the most difficult loudspeakers (electro-dynamic, electrostatic or compression chamber loudspeakers). So we do not recommend any specific brand.

Q: Can Nagra amplifiers accommodate any loudspeaker?
A: As speaker’s impedance varies with frequency, a good amplifier needs perform well even at low and very low impedance. This is the case of the VPA and the MPA. So they should accommodate any loudspeakers.

Q: Does Nagra recommend specific cables?
A: As for loudspeakers, it is difficult to recommend a specific brand of cable. We pay a lot of attention to our circuit design and internal signal cabling within our equipment; therefore it is of course important to use good quality cables for all the other connections of the system.

Q: Can I connect any source to my Nagra preamplifiers?
A: Nagra pre-amplifiers can accommodate both phono (PL-P only) and line level signals. The modulometer can be used as a true measurement tool, allowing the levels to be individually adjusted for each input. The PL-L and PL-P will allow you to benefit from the full dynamic of both your sources and your amplifiers.

Q: Where Nagra products are manufactured?
A: Nagra products are designed, manufactured, tested and certified in Switzerland. This ensures the high quality level that you expect from us.

Q: What are the final quality controls ?
A: Every single Nagra product leaving the factory goes through several final tests. One is mostly electronic and is semi automated. This is where the measurement protocol delivered with your Nagra is produced. Then the products go through the Subjective Test. Here, a highly skilled Nagra engineer will use the device as you would do in a “True home” environment. Every product is used for several hours and individually listened to before final certification.

Q: Does my NAGRA conform to the CE norms?
A: Yes. We have our own certified laboratory designated specifically for the CE certification procedure. Every product meets the required norms, and we keep available for the authorities all the measurement reports, for our equipment. A copy of a specific report can be provided if necessary.
Part 2 Sales

Question: I can’t find a distributor in my country, what should I do?

Answer: You should contact Nagra’s headquarter using our Contact Form on the web site.

Q: What should I expect from a Nagra dealer?
A: A Nagra dealer should provide you with a demonstration, advice on our products. Once you have decided to purchase one of our products, our dealer should come to your home to install all the equipment correctly and ensure that it is working perfectly.

Q: Should I buy a Nagra product in my country?
A: The retail price of all our products is based on the same price reference (based on the Swiss Franc currency). So all over the world the price should be the same. Of course, due to local customs and tax systems some minor differences may occur. We want you to benefit from a service you are entitled to expect from an established company such as Nagra. For this, we know that only your local dealer is able to provide you with service and support. For after sales issues, it is strongly recommended to officially import the equipment. In addition, be very careful with special offers over the internet, if you have any doubts, please contact us.

Q: How can I know more about a second hand Nagra?
A: Feel free to contact us, we’ll provide you with the manufacturing date and status of the machine.

Q: What is the link between Nagra’s Hi-Fi and pro products ?
A: Nagra professional and Hi-Fi products are designed and manufactured by the same employees from the Audio Division of the Kudelski Group. It is a great bonus for our team to know both worlds and the process of what happens during all the steps of the music production from the sound engineer to the music lover in its home.