New projects coming: balanced preamp with stepped attenuator and modular headphone amp

Right after getting things up and running and promising more frequent updates, it has been quiet for some time. However, it has not been quiet in my home lab. I’ve had two major projects under development: balanced preamplifier with relay stepped attenuator and modular headphone amplifier where amplifier boards can be swapped. The preamp is not completely my own design but is based on work by Bruno Putzeys and Hans … Continue reading

LME49724 vs. OPA1632 in Addon BalOut

Following performance figures have been measured in Addon BalOut module: Both opamps are so good that it is difficult to measure differences directly. LME49724: Noise level: -117 dBV (A-weighted), THD+N ratio: at least -109 dB (1 kHz, 2 Vrms), around measurement instrument limits. OPA1632: Noise level: -118 dBV (A-weighted), THD+N level: at least -109 dB (1 kHz, 2 Vrms), around measurement instrument limits. Measurements Originally the balanced addon board Addon BalOut for H-DAC have LME49724 fully … Continue reading

PCM1794A left/right channel distortion difference

Basically in all of my PCM1794A measurements I have seen something strange going on in the distortion figures between left and right channels. Right channel is constantly weaker but the results are very consistent between measurements, parts, and even different opamp models, while left channel shows better performance but the results are very inconsistent. I will show few examples from different measurements. To be honest, I still do not know what … Continue reading

PCM1794A output stage opamp measurements: LM4562, NE5532, and OPA2134

LM4562 and NE5532 show almost identical performance in I/V stage, while OPA2134 is 2 dB weaker. LM4562 is the best performer in differential amplifier. The best solution is to use NE5532 in I/V-stage and LM4562 in differential amplifier as it gives almost identical performance to all-LM4562 implementation Differences in distortion are mostly due to odd left/right channel differences of PCM1794A. Introduction PCM1794A has differential current outputs and therefore requires some analog … Continue reading

High-Quality Enclosures with Custom Finish – eBay & Schaeffer AG

When you are designing a device for everyday use it is nice if it looks so that you can put it on a shelf and not hide behind closed doors. I assume all DIYers have done something that looks absolutely horrible, when at the time it was just all about technical performance, or bang for the buck. However, if you spend all your free time and already almost all extra money … Continue reading