Search found 4595 matches

by mediatechnology
Mon Nov 23, 2020 5:28 am
Forum: The Peabody Lounge
Topic: The Corona Virus Hoax of 2020
Replies: 296
Views: 25022

"Pandemic is Over" - Former Pfizer Chief Science Officer Says "Second Wave" Faked On False-Positive COVID Tests

"Pandemic is Over" - Former Pfizer Chief Science Officer Says "Second Wave" Faked On False-Positive COVID Tests

https://www.zerohedge.com/medical/pande ... e-positive
by mediatechnology
Sun Nov 22, 2020 9:26 am
Forum: The Peabody Lounge
Topic: The Corona Virus Hoax of 2020
Replies: 296
Views: 25022

Portuguese Court Rules PCR Tests "Unreliable" & Quarantines "Unlawful"

Portuguese Court Rules PCR Tests "Unreliable" & Quarantines "Unlawful" An appeals court in Portugal has ruled that the PCR process is not a reliable test for Sars-Cov-2, and therefore any enforced quarantine based on those test results is unlawful. Further, the ruling suggested that any forced quar...
by mediatechnology
Sat Nov 21, 2020 3:49 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 52
Views: 49241

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

3) The third source is the output stage when heavily loaded at high levels. Working on it. Unloaded the second order is in the noise floor. The above appears to be PSRR related. I need to add bypass for the front end transistors and use shunt regulators for the whole oscillator similar to Vicktor's...
by mediatechnology
Sat Nov 21, 2020 1:13 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 52
Views: 49241

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

This is what the THD looks like when a 1KΩ load is connected to the opposing anti-polarity output. (Both outputs have 300Ω build-out resistors.) The output level is +16 dBu (differential). The notch filter is connected to a single output so the level at that node is +10 dBu. The peak current in the ...
by mediatechnology
Sat Nov 21, 2020 9:18 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 52
Views: 49241

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I am using a THAT2180 pre-trimmed VCA. I prefer them over the 2181 because they eliminate a trim and the on-chip Zener-zap trim of the 2180 has better THD tempco. The VCA is in parallel with a non-inverting path and subtracts a tiny fraction of the signal with the VCA typically operating with about ...
by mediatechnology
Fri Nov 20, 2020 6:47 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 52
Views: 49241

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I've been able to lower second harmonic distortion by identifying three sources. 1) The VCA. I lowered the input current by 14 dB. It no longer contributes. 2) The half-wave detector. With the VCA now being distortionless I could see detector residual ripple contributing. I added a passive filter po...
by mediatechnology
Fri Nov 20, 2020 6:38 pm
Forum: Build
Topic: Powerable from +/-15V supplies using an external 7824 or LM317 regulator
Replies: 2
Views: 43

Re: Powerable from +/-15V supplies using an external 7824 or LM317 regulator

Found this, which was super helpful; looking for an example of the implementation, if possible: “Re: Mid Side M-S Matrix Construction Information Report Quote Post Mon May 16, 2016 3:49 am [...] The bypass board is 24V (using 12V relays). The coil connections float and are not tied to any ground. T...
by mediatechnology
Thu Nov 19, 2020 6:35 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 52
Views: 49241

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

JR: I agree that some filtering would be a good idea. The following are the notch filter output. There is +40 dB gain post-filter so -100 dBu displayed on the graphs is actually -140 dBu. With a +4 dBu single-ended output into a 1KΩ load the distortion is in the noise floor. https://proaudiodesignfo...