Search found 290 matches

by terkio
Wed Jan 13, 2021 4:06 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 132
Views: 175999

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: 132
Views: 175999

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: 132
Views: 175999

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: 132
Views: 175999

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: 132
Views: 175999

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...
by terkio
Tue Jan 12, 2021 10:12 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 132
Views: 175999

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Twin T calculator: http://sim.okawa-denshi.jp/en/TwinTCRkeisan.htm It gives the equation of the transfert function. It calculates everything, one wants to know about filters, when you plug in the C and R values. A point I do not understand. It gives two equations for f0, the "Center rejection freque...
by terkio
Mon Jan 11, 2021 2:45 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 132
Views: 175999

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Gain without A/D overload from the 1 kHz fundamental. Thanks, this is the key point, I was missing. I had overlooked the importance of the x100 gain at the output of the double T filter. The notch filter removes the 1 kHz fundamental and then adds 40 dB of gain to expand the analyzer A/D range abou...
by terkio
Sun Jan 10, 2021 8:17 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 132
Views: 175999

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I am puzzled about a notch filter you plan to add on the oscillator board. How will these be used ? With the ULDO I understand you can go at measuring the THD of some audio device. With the ULDO at the input of the DUT, the Focusrite at the output, you get the FFT then calculate the THD+N. This shou...
by terkio
Tue Jan 05, 2021 4:34 pm
Forum: The Peabody Lounge
Topic: Entropy
Replies: 1296
Views: 603725

Re: Entropy

With these cheap valves I often I see leaking from around valve handle/stem, my suspicion is that these valves are not engineered for many lifetime operations. Sometimes the leaking stops when turned hard open or hard closed, so I stopped trying after neither position stopped the drip. Some designs...
by terkio
Tue Jan 05, 2021 8:30 am
Forum: The Peabody Lounge
Topic: Entropy
Replies: 1296
Views: 603725

Re: Entropy

I really hate it when physical things do not behave as expected (its the laws of physics). I previously mentioned it was an odd "coincidence" that the sink cut off valve started dripping after I shut off the hot water heater... Now after repairing the heater and bringing it back online, the drip ha...