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:
Findings:
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 |
Conclusions:
- 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
OggStreamer 