Q: What is BORBELY AUDIO?
A: BORBELY AUDIO is a company that develops and sells high quality, high-end – yet economically priced - kits for DIY (Do It Yourself) audio amateurs. We also sell DIY audiophile components.

Q: What is BORBELY AUDIO’s design objective?
A: Our design objective is to reproduce music without adding or subtracting from it, i.e. to make our amplifiers as transparent and natural sounding as possible.

Q: How can you claim that your kits can match just about any “High End” amplifier in terms of sound quality?
A: Our customers are telling us that carefully assembled, the BORBELY AUDIO kits can match just about any “High End” amplifier in terms of sound quality, irrespective of price. We believe that we achieve this quality by using the “best” of the circuit topologies, and the “best” of active and passive components in our amplifiers.

Q: What kind of circuit topologies and devices do you use in your designs?
A:
1. All our circuits are fully symmetrical, using complementary devices.
2. We use discrete devices throughout because ICs are not available with fully complementary circuitry, and in our experience we get a better sounding amplifier with discrete devices.
3. We are using low-noise high gm JFETs as input devices, and JFETs or MOSFETs as output devices. FETs lack the graininess of bipolar transistors and are believed to generate a more “friendly” spectrum of noise and harmonics than bipolar ones. Low-noise JFETs are capable of an extremely high resolution of low-level signals.
4. Our High Performance kits are Cascode connected for best linearity and for reducing internal capacitance and capacitance modulation.
5. We use non-magnetic resistors from Vishay-Dale as standard resistors.
6. We focus on using good capacitors.
7. All of our Starter kits, the High Performance kits and the Pro Audio kits are DC-coupled circuits.
8. All of our preamplifiers and power amplifiers are operating in or close to Class-A (see below for separate note on Class-A operation).
9. Our power supplies and regulators set new standards in current capability, bandwidth and low noise.
10. Our Power amplifiers have enormous current reserve and good stability and can drive the most difficult loudspeaker loads on the market.
11. We are designing our amplifiers conservatively, to perform reliably and without degradation for many years.

Q: What are the main differences between the Low Cost Starter kits, and the High performance and Pro Audio Kits?
A: The major difference between Low Cost Starter kits and the High Performance and Pro Audio kits is the topology. The Starter kits are simpler, with no or very few cascode stages. They are not designed to drive very low impedance loads. They are easier to understand and assemble, and we’ve done some leg work for you by designing the Starter Kits with on-board regulators that are included in your purchase. We’ve also designed optional power supplies for each of our starter kits, so you’ll spend more of you time building the kit and learning than scrounging for parts. Of course it’s important to know that the Starter Kits are indeed “high performance” by their own rights. These kits are serious audio and all carry the “BORBELY AUDIO” sound signature of high resolution and transparency.

Q: What about your tube kits?
A: Our tube kits follow the same general guidelines, however, due to only one polarity tube, the designs are not complementary. Just like with the FET ones, we are trying to make the tube amps as linear as possible, in line with our objective of making our amplifiers as transparent and natural sounding as possible.

Q: What is Class-A?
A: The definition of Class-A is simple. The active devices (tubes, bipolars, FETs) are always conducting and never go into cut-off. This is especially important to keep in mind when we talk about the output stage, where large currents are flowing.
Naturally, the definition of “pure Class-A” can be very different from manufacturer to manufacturer. Often this is nothing but marketing hype; the bias current is probably high enough to support Class-A operation up to 1W, but nothing more. It is especially disturbing to see claims for Class-A operation up to, say, 50W and then find a tiny heatsink inside the amplifier. Class-A operation requires lots of current; consequently they generate a lot of heat and require large heatsinks. Here is the best rule to follow: An amplifier with a small heatsink, you can usually question the Class-A operation!

Q: What are the benefits of Class-A?
A: It has been proven in many listening tests that amplifiers working in “pure” Class-A sound better then those working in Class-B or AB. The improvements are increased low-level detail and ambience. These improvements are attributed to the fact that the active devices are operating in their linear region without abrupt nonlinearities and without turn-on/turn-off delays. This applies to both low-level and power amplifiers. Most Opamp based amps are working Class-B or best case with a very low bias in Class-AB, and they have to be forced into pseudo Class-A with external circuitry.

It is also important that power amplifiers working in Class-A have, by definition, high current capability, and they are capable of driving difficult loudspeaker loads better than Class-AB amplifiers.

Q: What is Class-B and Class-AB?
A: In Class-B amplifiers only one of the output devices is conducting at any one time, the other one is cut off. Since the devices are not perfect, there is no seamless transition between the devices. This is causing what we call “crossover distortion”. This non-linearity is causing mostly higher harmonics of the music signal, which is unnatural and fatiguing to listen to.

Class-AB is somewhere between Class-B and Class-A. Both devices are conducting simultaneously up to a certain output power, i.e. the amp is working in Class-A. However, when they run out of bias they revert to Class-B operation.

Q: What is included in a BORBELY AUDIO kit?
A: A BORBELY AUDIO kit includes drilled and printed PC board, all semiconductors, resistors, capacitors and mechanical components like heatsinks, stand-offs, screws that go on the PC board. All components are packed in separate plastic bags, which are marked with the component designation and the component value. This makes it easy to check the contents of the bags and also makes assembly easier.

Q: What kind of PCB material is used for the standard PC Board?
A: We are using the military grade fiberglass FR-4, instead of the Phenol based material used in mass-produced consumer goods.

All of our PCBs are hand-routed, because we feel that it is very important to place the components in the “right place” relative to each other. Automatic Routers are not capable of doing this. We also use single-sided PCBs, because it’s easier for DIY amateurs to assemble them.

Q: What is the difference between Teflon and FR-4 PCBs?
A: The FR-4 works very well in most audio applications. However, it is a very hard material and has a tendency to vibrate. This might cause tiny current changes in the components on the board, which, especially in very low level circuits like MC phono preamps and microphone preamps can cause unwanted “sounds”. Teflon base-material, which has been developed for HF circuits, is much less prone to vibration. Consequently it is very much preferred for low-level circuits. Some customers also prefer the Teflon boards for line and power amplifiers.

Q: Why do you not sell PCBs for your designs?
A: We have been selling PCBs alone before, but the result was not satisfactory. First of all we use only high quality components in our kits, including the Starter kits. These are not easy to find in low quantities. Also, most of the FETs that are used are matched to close tolerance. In order to do this we buy hundreds or thousands of FETS and match them carefully. If you just use components from Radio Shack or similar outlets, the result will be very disappointing. This will turn the customer off the kit building and it will give us bad reputation. Thus, we do not sell PCBs.

Q: Who can assemble a BORBELY AUDIO kit?
A: The manuals give detailed instruction as to assembly and set-up; however, there is no step-by-step instruction. The BORBELY AUDIO kits are easy to assemble for experienced kit builders, but could be difficult for beginners.

The first requirement in kit building is proper soldering. Most of the problems come from cold solder joints and shorted tracks. If you are new to soldering then you should exercise soldering before you start on the kits. To avoid shorted tracks a very fine tipped soldering iron and only fine solder should be used. A 2% silver bearing solder flows very well and gives excellent solder joints with low resistance.

Second requirement is a basic knowledge of schematics and stuffing guide. You don’t have to be an electronic technician to be able to read schematics. There are several books on the market that teaches you how to read schematics, look up the books available at Old Colony Sound Laboratory (www.audioXpress.com). If you have a friend who is experienced in kit building you can also ask him for some help.

Q: How can I upgrade my kits, and what sonic improvements can I expect?
A: See “UPGRADES” on the homepage.

Q: What makes a working amplifier?
A: One of our customers likes to point out that “There is more to an amplifier than just a kit”. And of course he is right. Although some kits include regulators, you still need to provide a power supply. And when these are available, then you have to think about the input switch, the volume control, the input/output connectors, wires, etc. And finally you need to have a nice box to put the whole thing into! All this requires a lot of effort and, lets face it, a lot of work. But then again, this is what makes it rewarding, because YOU have done it. AND saved a lot of money in the process. AND have a product, which you are proud to show to your friends, and, most importantly, you have a high quality product to listen to.

Q: What kind of support does BORBELY AUDIO provide?
A: Although you might be many thousands of miles from us you can always reach us via email, fax (+49/8232/903618) or phone (+49/8232/903616). I am sure we can work out most of the problems that might show up during assembly. Don’t hesitate to contact us if you need help!