Advance Paris has long been known for its excellent sounding Bluetooth receivers. Advance also regularly uses vacuum tubes in its products, such as in CD players and amplifiers. To design a Bluetooth receiver with vacuum tubes is therefore perhaps the obvious choice.
Tubes in the analog output stage
It has become the WTX-TUBES. A design where the famous Raytheon 5703 vacuum tubes are used in a Class A setup in the output stage, just after the d/a converter and before the analog output. The tubes are mounted in insulating holders to suppress microphonic effects and maintain a constant temperature. The analog output can be connected with an RCA/Cinch cable to an analog input (Line In or AUX) on an amplifier, receiver, etc.
Advance does not use the dac (digital/analog converter) integrated by Qualcomm into the standard Bluetooth chipset. Advance makes a tap and deploys a self-selected and higher qualified, Cirrus Logic/Wolfson WM8740 (24bit/192kHz), dac. Despite the fact that Bluetooth 5.0 HD has a maximum resolution of 24 bit/48kHz, the WM8740 is used with its higher resolution because of its beautiful sound. The WTX-TUBES also has an optical and coaxial output to be able to use an external dac.
HD-DETECT, a unique feature
The WTX-TUBES is in Bluetooth Hi-Res 5.0 mode by default. Recognizable by the illuminated blue LED in the front panel. However, it is possible that the sound quality decreases, especially when the signal transmission between the transmitting device and the WTX-TUBES is too weak or unstable due to a slightly too large distance, for example. In such a case, the HD mode can be switched off by setting the switch on the backs to ‘Off’.
If the source device does not offer aptX HD, that is no problem. The WTX-TUBES is backwards compatible with older Bluetooth protocols.