Search found 261 matches

by terkio
Thu Jan 14, 2021 5:33 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

So far, with simulations I found no difference. Virtual grounds connected or not, no difference detected. The unbalances, I tried: inputs amplitudes 0.25 0.75 ( iso 0.5 0.5 ) input resistance 1K 2K ( iso 1K 1K ) With or without differential output load 100K. Interesting. I found the same thing on t...
by terkio
Thu Jan 14, 2021 1:38 pm
Forum: The Peabody Lounge
Topic: Entropy
Replies: 1190
Views: 463838

Re: Entropy

I cannot resist to tell a most stupid mistake of my own. That was with a battery charger. A cheapo. I set the charger near the car battery, checked I had an ok voltage at the battery, so far so good. A couple of hours later, I came back to check. From a clumsy move, the charger tumbled down, while i...
by terkio
Thu Jan 14, 2021 9:04 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

So far, with simulations I found no difference. Virtual grounds connected or not, no difference detected. The unbalances, I tried: inputs amplitudes 0.25 0.75 ( iso 0.5 0.5 ) input resistance 1K 2K ( iso 1K 1K ) With or without differential output load 100K. I then thought I should try with non idea...
by terkio
Wed Jan 13, 2021 6:48 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Extremely brain warping. When fully balanced, indeed both are at 0V so no current in between. So it should make no difference to split or not to split. But I am not sure, I feel some pit fall here. Assuming fully balanced inputs ( same level, same impedance ) and fully balanced output ( same load ) ...
by terkio
Wed Jan 13, 2021 6:03 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

All that has to be done to switch the filter topology from Left/Right to balanced is to float where VR2/C3/C4 on both channels would common to ground and switching R7 from ground to the other channel's R7 to make the SE 40 dB gain stages a 40 dB INA. It only takes two switch poles I think you need ...
by terkio
Wed Jan 13, 2021 4:06 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Do 5X 15K9 and 5X 10 nF sim at 1 kHz for differential inputs? Yes. I Simed with differential inputs. 5 X 16K and 5 x10nF: Notch -90dB at 994.7191 Hz Sim with 5 x 15.9K: Notch -96dB at 1.001 KHz. More info: The transfer function of the Twin H is certainly the same as the Twin T. From the simulation,...
by terkio
Wed Jan 13, 2021 2:36 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

0.0000076% THD Great result. Trimming a Twin T to null its output. How difficult, it is ? How many iterations going around at the two trimmers, does it converge smoothly to the final result ? Obtaining a stable phase looks awkward to me, because for a perfectly nulled filter the phase jumps from 90...
by terkio
Tue Jan 12, 2021 4:01 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Selecting 15K resistors < 1% is the right way to go. I was wrong. Based on caps 1%, with resistor selecting < 1%, indeed, it does halves the trimming requirement. Using the twin T calculator, I figured the f0 sensibility to the Resistors and Capacitors. I finally found: With +1% on all C and R, f0 g...
by terkio
Tue Jan 12, 2021 1:11 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I don't get it. I think, what is conditioning the value of the trim is mostly the caps tolerance. 15T trims and higher is no good answer, I think. Firstly, what's needed is as low a resistor value, that has a range good enough with reasonable margins. This is not easy, it requires good knowledge of ...
by terkio
Tue Jan 12, 2021 12:17 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55576

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Thanks for all these informations. I re read the Jansek's paper. Great work indeed. 10nF 1%. Excellent, the accuracy of the caps is an important point. 1% resistors is good, but no need for better, since there are trimmers. However, they better have a good TempCo ( The caps, too. ). Switching: Janse...