Search found 4751 matches

by mediatechnology
Tue Jun 29, 2021 10:41 am
Forum: Build
Topic: Phono Transfer System Construction Information
Replies: 227
Views: 254132

Re: Phono Transfer System Construction Information

The preamp schematic would give us a clue about the head impedance. The active preamp would be the best one to look at. I would think either the MM or MC preamp could be adapted.
by mediatechnology
Tue Jun 29, 2021 9:58 am
Forum: Build
Topic: Phono Transfer System Construction Information
Replies: 227
Views: 254132

Re: Phono Transfer System Construction Information

Paul -

Send me a scan of the A80VU preamp and I'll have a look.

Wayne
by mediatechnology
Tue Jun 29, 2021 5:18 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Nice work Mike! Would the USB Power supply you are referring to be a Silent Switcher? Your photo made me go to eBay and look for a Leader LAT-45. I remember that when I modified my IG-18 in the early 1980s with the Morrey Super Oscillator board I bought an extra attenuator switch and removed the old...
by mediatechnology
Sat Jun 26, 2021 10:27 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

I think the Output Level range at the low end of adjustment needs to be limited by increasing R30. It's currently about -10 dBu minimum with a range of -10 dBu to +26 dBu on the balanced output. There are two reasons for this. 1) The oscillator has the best THD in the range of +10 to +20 dBu output....
by mediatechnology
Fri Jun 25, 2021 9:48 am
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

ULDO-Nacho FFTs and THD

I built a second ULDO-Nacho board and made some 1 M point 50 sample average FFTs. The Y-axis in the following FFTs have offsets to reflect the post notch filter gain (+40 dB) and the "carrier" (output level). The result is dBc and does not reflect the insertion loss of the notch filter. The Left ch...
by mediatechnology
Thu Jun 24, 2021 5:43 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Updated ULDO-Nacho Assembly and Test Instructions with Schematics: https://proaudiodesignforum.com/images/pdf/Ultra_Low_Distortion_Oscillator_Assembly_Instructions_ULDO-Nacho_18_Assembly_And_Test_070821_1.pdf Mouser Project Manager BOM for ULDO-Nacho: https://www.mouser.com/ProjectManager/ProjectDe...
by mediatechnology
Wed Jun 23, 2021 1:09 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Using a 5532 I just checked the output offset on the first PC board and it's about -1.8V with the notch filter unbalanced and about -130 mV with the jumpers set to balanced. That offset is primarily due to Ib*100KΩ*Gain. I made Rbias large to allow a lowish value polypropylene film cap and let the o...
by mediatechnology
Tue Jun 22, 2021 5:23 pm
Forum: Pro Audio Design
Topic: Super Low Distortion Ultra Pure Audio Oscillators Revisited
Replies: 152
Views: 179863

Re: Super Low Distortion Ultra Pure Audio Oscillators Revisited

Mike you're right about the output offset. That 10mV number was from cut and paste. The 1.5V that does develop shouldn't be too much of a problem since the output is AC coupled and the INA doesn't see much level due to the preceeding notch filter. I actually anticipated that and AC coupled it for th...
by mediatechnology
Sat Jun 19, 2021 3:04 pm
Forum: Pro Audio Design
Topic: Transistor Vbe Matching Using A Commutating Chopper-Based Circuit
Replies: 32
Views: 69198

Re: Transistor Vbe Matching Using A Commutating Chopper-Based Circuit

I had used up my stock of matched ZTX-851 transistors for the flat MC preamp and the time had come to match some more up. The ZTX851 for this run was from a different lot. Out of 30 devices I had no problem getting 12 pairs matched to <1 mV which is adequate for the MC preamp. This lot had higher ga...
by mediatechnology
Sat Jun 19, 2021 12:48 pm
Forum: The Peabody Lounge
Topic: The Corona Virus Hoax of 2020
Replies: 419
Views: 170405

Eric Clapton Details How The COVID 'Vaccine" Paralyzed Him

Eric Clapton Details How The COVID 'Vaccine" Paralyzed Him https://banned.video/watch?id=60c921e9384b080b2bf5dc83 The full Eric Clapton interview form Oracle Films can be found here: https://www.youtube.com/watch?v=4OHmMKrVbNk Eric Clapton details how he was duped into getting the Astra Zeneca vacc...