Today I had an in detailed look on the input amplifier of the OggStreamer – i documented the measurement in this report.
If you don’t want to read the full report – I copy’n’pasted the summary here:
The input amplifier stage of the OggStreamer performs in almost all respects as desired. One problem showed up during the measurement: The Inbalance of Gain between Channel A and Channel B. Further investigation proved that the Potentiometer is responsible for this Inbalance. We already took care for a second option for the potentiometer while desing the OggStreamer. The option would be a Vishaytype of Potentiometer – for the next batch of OggStreamer devices this will be an economic decission whether or not to use the Vishay-Poti (12 Euro) or the ALPS-Poti (1,2 Euro). Apart from the Inbalance-Issue the ampilifier works as desired.
|Gain||Channel Inbalance||-3dB cutoff||THD+N||Crosstalk|
|Measurement 1||0dB||0.18 dB||~ 30 kHz||< 0.2 %||< -60 dB|
|Measurement 2||-15dB||0.57 dB||~ 27 kHz||< 0.12 %||< -60 dB|
|Measurement 3||15dB||0.27 dB||~ 25 kHz||< 0.6 %||< -50 dB|
- We will specifiy the input stage of the OggStreamer for +/- 15dB Gain – in reality it is a little wider but for the docs we will stick with +/- 15 dB
- The ALPS-Potentiometer performs mediocre – We will test an alternative VISHAY-Type (Order Code: 148DXG56S103SP) and evaluate if we can afford using this more expensive Potentiometer