Search found 4693 matches

by mediatechnology
Wed Jan 13, 2021 3:44 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

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 ? I just built the second one and it took maybe 30 seconds. You just dip each one - the first iteration is only a few dB. Rinse, lather, r...
by mediatechnology
Tue Jan 12, 2021 7:05 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I built two Nacho filters and used them to monitor both output legs of the oscillator. I then extracted the differential output of the notch filters using a THAT1240 to check the distortion in a balanced load. (Looking at both legs individually, in common mode, doesn't tell you how the distortion ac...
by mediatechnology
Tue Jan 12, 2021 4:41 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

The oscillator network is almost identical to the twin-T. (10 nF, 10+10nF, 15K9, 7K95) One arm is 20 nF + 7K95. The feedback arm is 15K9||10nF. I pulled mine to 996 Hz using 3X randomly-selected 15K8. I think my C's are a tad high in value. It uses the same values for both C and R. The tolerance sen...
by mediatechnology
Tue Jan 12, 2021 2:49 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

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.
It's both the C and the R.
But the R is easier to match and that makes more trim range available for the delta-C.

15T trims are fine.
A super-deep null isn't needed.
I wouldn't over think this.
by mediatechnology
Tue Jan 12, 2021 12:39 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

My reasoning behind selecting the 15K resistors to <1% was to reduce the overall error of that arm and therefor reduce the value of the trim. With larger-value 15T trims the mechanical backlash in the adjustment is apparent as one attempts to adjust to a really deep null. The depth of the null howev...
by mediatechnology
Tue Jan 12, 2021 10:29 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Twin T calculator: http://sim.okawa-denshi.jp/en/TwinTCRkeisan.htm I use that site all the time but forgot to look there for a twin-T. The twin-T notch filter I published earlier in this thread will likely be what I layout on the PCB. It's from Jansek. The component sensitivity hasn't been much of ...
by mediatechnology
Mon Jan 11, 2021 12:44 pm
Forum: Test, Measurement and Repair
Topic: The iDefender USB Ground Isolator
Replies: 2
Views: 214

Re: The iDefender USB Ground Isolator

I bought a second USB A to A from B&H Video and we'll see how that works out. I'll repost iDefender's response to my open ticket on the C to C version. The promptly-delivered USB C to C iDefender from B & H Video works flawlessly. Now, both 2i2s have isolators. My desktop PC's 2i2 is dead quiet. I'...
by mediatechnology
Mon Jan 11, 2021 11:01 am
Forum: Document
Topic: Zener Diode Table
Replies: 3
Views: 90

Re: Zener Diode Table

My brother's former electronic distributorship, KA Electronic Sales, had a desk pad with tables like this as a promo/swag item.
I named my website to honor my brother who passed away in 2002.
I saved a sheet from that pad and should scan it for historical perspective.
by mediatechnology
Mon Jan 11, 2021 8:23 am
Forum: The Peabody Lounge
Topic: Radio World Commentary: “The Old Goats Are Going Away”
Replies: 0
Views: 47

Radio World Commentary: “The Old Goats Are Going Away”

Radio World Commentary: “The Old Goats Are Going Away” My first real bit of engineering was converting a 50 kW FM station to stereo in 1963. No one listened to FM then, I think there were 10 FM radios in the city and five were in Cadillacs owned by mob hit men. When we talk of RF, we talk of a whol...
by mediatechnology
Mon Jan 11, 2021 6:25 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 102
Views: 55542

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

The filter almost has to be passive in order be near-distortionless and it also needs to be made with ultra-low distortion passive components.

When I make a second Nacho filter, for either the right channel or for a quasi-balanced filter, I'll have a filter to check the filter.