My soldering skills are not that great, so my board is not as pretty as the one on the website, but I had no problems making workable solder joints. The pictures show the bare boards and the completed boards. Most of the time, I could find the answer just by studying his very complete schematics. Whenever I got into trouble, Jos was able to help me. This was my first time with surface mount components, but the board has been designed with many through hole components and enough room for hand soldering surface mount components. There is now a US component table because I found that some components that are available in Europe are not available in the US. The system uses separate power supplies for the audio and digital control system. They are very high quality and well laid out. The boards arrived from Europe in about a week. A significant part of this cost is the cost of the relays. Combined with the cost of the boards, the total cost of the project (less chassis) was a little over $400 US. The end user purchases these components his or herself to match the BOM. A component table with links to suppliers is on the website. Cost of the boards and controller, plus shipping was about $125 US at the time of my purchase. Jos offers PCBs for the project and the option of a pre-programmed micro-controller.

Status is shown by a two digit LED display. In this case, balance control is simply offsetting the left or right channel by a different choice of volume between the left and right channels.Īll of this is controlled either by a universal infrared remote control using Philips or Sony control language or by a rotary encoder on the face of the preamp. The Relaixed2 uses a digital control system to select the relays controlling input channel, volume, and balance. In Relaixed2, he uses relays to switch inputs and to switch between resistors in the stepped ladder attenuator. Jos found that high quality sealed relays have long life and make a very low noise contact. Mechanical wipers in potentiometers and mechanical contacts in manually switched attenuators have the potential for noise. Electronic volume controls can color sound. The most unusual thing about Relaixed2 is it's use of high quality relays. Output Noise Voltage – 10nV/Hz max volume Signal to Noise Ratio – 123 dB at max volume, input shorted

See his very complete website for more details.Ĭhannel separation 1 kHz) – single ended – 128 dB This is a good place to consider rolling op-amps to find the ones that you like best as the rest of the circuit should be insensitive to op-amp choice. LM4562s are suggested for the signal op-amps, but any 8 DIP dual op-amp can be used. The op-amps convert single ended inputs into balanced inputs and provide gain. Only input channel switching, 2 op-amps per channel as a buffer, and a stepped ladder attenuator. The signal has the minimum number of components in its path. Starting from the input, it has either 4 single ended inputs and 2 balanced inputs or 3 single ended inputs and 3 balanced inputs. I don't have any interest in this product, other than as a customer. The usual disclaimer here I am just a customer. It is a DIY balanced Pre-Amp from Jos van Eijndhoven. On my shopping list was a low noise design, neutral in sound, and hopefully with balanced outputs. Earlier this year, I was looking for a better pre-amp.

Balanced pre amp