Pro Audio Design Forum

My first series of tests on 15KΩ resistors used the 1984 CMF-55 10K matched to 0.01% in the bottom leg. I saw a little HD2 increase with all DUT so I changed strategy. The bridge is driven by a ground-referred balanced output and and is recovered by a floating-input balanced "double-twin-T"...

Give the exact scheme by which you measured the THD of the resistances. There are many pitfalls. Where is the evidence that everything else, the generator, the filter and the amplifier after the filter, have at least 10 times less THD than the resistors. The THD of a non-inverting amplifier or buff...

Looks like I'll be using either RN55, Vishay MBB0202 or the Holsworthy Y1RB in a few key locations: viewtopic.php?p=17744#p17744

I posted this over at DIY Audio. I now have some interesting comparative data. I built a bridge from 4X 10KΩ resistors and drove the upper and lower arms of the bridge with ULDO at +26 dBu. The center of the bridge was connected to the balanced input of the notch filter. The post-filter gain is 40 d...

Great job and thank you for joining us Sandy!

If I've done the mental gymnastics right it looks like you've manged to achieve 28 ppb THD.

Gotta ask: What resistors are you using?

From the noise floor it looks like your notch filter insertion loss is being corrected.

Cross-posted from the Build thread for ULD-Nacho: I've assembled quite a few ULDO_Nacho boards using value-matched resistors for the 15KΩ in the Wien bridge and the 10KΩ in the inverter. I've been installing Xicon or Yageo which appear to be identical and consistently get THD levels around -143 dBc ...

I've assembled quite a few ULDO-Nacho boards using value-matched resistors for the 15KΩ in the Wien bridge and the 10KΩ in the inverter. I've been installing Xicon or Yageo which appear to be identical and consistently get THD levels around -143 dBc or -139 dBc with a 600Ω load. I decided to try the...

A picture is worth a thousand words... For future reference I found this linear domain versus log domain filter comparison in Fred Floru's AES paper. https://proaudiodesignforum.com/images/jpg/Linear_Vs_Log_Domain_Filter.JPG Linear vs. log-domain filter The diodes in the final stage of the RMS detec...

IIRC both DBX and Paul Buff made wide range dB meters back in the day. Both probably used VCAs and companding inside to deliver wide dynamic range (my speculation). Sorry for yet another veer... ;) JR You sent me the data sheet for the Valley People meter I've been meaning to scan. I think I have a...

Thanks Jeffrey!