Search found 5477 matches
- Fri Apr 26, 2024 7:04 pm
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
The fact that there may be bad resistors does not mean that during the measurement one should not check what the capabilities of the measurement are. What appears as pictures is not clear. You say the bridge signal is +20db after the bridge is reduced by -60db and then amplified by +40d b So the AD...
- Fri Apr 26, 2024 5:42 pm
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
But I'm not attempting to measure THD with any precision. I'm attempting to find, and am finding, bad resistors by comparing them to good ones. I don't need an incredible DR to find these in the CMF-55s that led me down this rabbit hole. I recreated the original setup - it takes only a couple of min...
- Fri Apr 26, 2024 3:34 pm
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
Turns out my revised concept doesn't work as well as what I originally tried. In the revised concept common mode to differential conversion due to resistor mismatch swamps differential distortion created by the relative difference in resistors. The CM rejection is also not enough to keep the A/D wit...
- Fri Apr 26, 2024 9:53 am
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
My initial tests didn't use a 1646 or 1510 but conceptually it is similar to this: https://proaudiodesignforum.com/images/jpg/Resistor_Relative_Linearity_Tester.jpg As I mentioned earlier when RA=RB=RC=RD with any degree of precision the 1 kHz excitation and it's harmonics will be attenuated when sa...
- Fri Apr 26, 2024 7:39 am
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
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"...
- Fri Apr 26, 2024 7:33 am
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
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...
- Wed Apr 24, 2024 10:12 am
- Forum: Build
- Topic: ULDO-Nacho-Atto Ultra Low Distortion Oscillator, Notch Filter and Attenuator Construction
- Replies: 7
- Views: 27019
Re: ULDO-Nacho-Atto Ultra Low Distortion Oscillator, Notch Filter and Attenuator Construction
Looks like I'll be using either RN55, Vishay MBB0202 or the Holsworthy Y1RB in a few key locations: viewtopic.php?p=17744#p17744
- Wed Apr 24, 2024 10:06 am
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Re: Dale CMF55-series Resistor Distortion
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...
- Wed Apr 24, 2024 5:14 am
- Forum: Pro Audio Design
- Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
- Replies: 165
- Views: 397168
Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited
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.
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.
- Sat Apr 20, 2024 1:20 pm
- Forum: Pro Audio Design
- Topic: Dale CMF55-series Resistor Distortion
- Replies: 14
- Views: 426
Dale CMF55-series Resistor Distortion
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 ...