#oggstreamer – measuring the input stage (2nd time)

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 ā€“ 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:

  1. We will specifiy the input stage of the OggStreamer for +/- 15dB Gain ā€“ in reality it is a little wider but for the docs we will stick with +/- 15 dB
  2. The ALPS-Potentiometer performs mediocre ā€“ We will test an alternative VISHAY-Type (Order Code: 148DXG56S103SP) and evaluate if we can afford using this more expensive Potentiometer
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