Search found 5449 matches

by mediatechnology
Wed Oct 14, 2009 1:58 pm
Forum: Document
Topic: SSL Phase Meter Schematic
Replies: 16
Views: 32018

Re: SSL Phase Meter Schematic

John - Unless they have a 'scope or are working on a DAW I don't know how they would have a visual indication of absolute polarity in the studio.
by mediatechnology
Wed Oct 14, 2009 10:56 am
Forum: Document
Topic: SSL Phase Meter Schematic
Replies: 16
Views: 32018

Re: SSL Phase Meter Schematic

I did it with log amps and ratios. I don't think it would be too hard in DSP. At some point in the chain you have to define the electrical polarity from the correct acoustic polarity using a measurement mic to define "right-side up" as pressure. If the speaker drive is "waveform posit...
by mediatechnology
Wed Oct 14, 2009 10:12 am
Forum: The Peabody Lounge
Topic: Are These Two Soundfiles the Same?
Replies: 1
Views: 5522

Are These Two Soundfiles the Same?

Here's the first one: http://www.proaudiodesignforum.com/Content/Renee_Olstead-Someone_To_Watch_Over_Me_Cut_1.mp3 Here's the second: http://www.proaudiodesignforum.com/Content/Renee_Olstead-Someone_To_Watch_Over_Me_Cut_2.mp3 Do you hear any differences? No peeking. Resist the temptation to open them...
by mediatechnology
Wed Oct 14, 2009 10:01 am
Forum: Document
Topic: SSL Phase Meter Schematic
Replies: 16
Views: 32018

Re: SSL Phase Meter Schematic

I'm still thinking about when I would want a correlation meter. The scenarios are few. In broadcast about the most obvious application is in machine room/content ingest applications where you occasionally get stereo content delivered with the polarity flipped on one channel. I think it makes sense i...
by mediatechnology
Wed Oct 14, 2009 9:39 am
Forum: Pro Audio Design
Topic: The 48V Phantom Menace Returns
Replies: 11
Views: 24528

Re: The 48V Phantom Menace Returns

Thanks John. The observation about transient interfering with PS rail may explain one difference between my (low) failure experience in mixers and your bench.. I suspect the consoles may have more rail capacitance to soak up the current. (Also I typically used 22 uF). I agree. And there's a lot of o...
by mediatechnology
Wed Oct 14, 2009 5:11 am
Forum: Pro Audio Design
Topic: The 48V Phantom Menace Returns
Replies: 11
Views: 24528

The 48V Phantom Menace Returns

Here's a paper Ros Bortoni and I recently wrote about the phantom menace. Ros has just presented it at AES 127. http://www.thatcorp.com/datashts/AES127-000183.pdf We managed to discover a differential fault mode that's particularly destructive. Previously, the diode bridges to the supply rails have ...
by mediatechnology
Wed Oct 14, 2009 4:32 am
Forum: Pro Audio Design
Topic: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
Replies: 80
Views: 350246

Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp

OK, glad that worked out. For RFI filtering you might consider a series R and capacitive shunt ahead of the pot at the RCA jack. With the inverting input of the op amp unaccessible its difficult (impossible?) to put it in the feedback loop.
by mediatechnology
Tue Oct 13, 2009 1:58 pm
Forum: Pro Audio Design
Topic: VCA theory question
Replies: 36
Views: 54192

Re: VCA theory question

Why not use the 4.98V directly - why scale it down? Like John I'm not sure I understand the question either. But if you want to apply 4.98V directly to Ec+ or Ec- it will cause problems. Ec is limited to less than one Vbe or the junctions in the gain cell will become reversed biased. Take a look at...
by mediatechnology
Tue Oct 13, 2009 1:27 pm
Forum: Pro Audio Design
Topic: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp
Replies: 80
Views: 350246

Re: Using the THAT1646 As A Transistor Pre-Driver/Headphone Amp

Very clever idea. Thanks for joining us and posting. I want to keep the complete amp DC coupled if possible, and in the 0dB setting the ofset is close to 0mV, but in the 9dB setting I get more that 200mV. But this is taken care of by a 15M Ohm resister to the negative voltage. This brings the ofset ...
by mediatechnology
Mon Oct 12, 2009 1:05 pm
Forum: Document
Topic: SSL Phase Meter Schematic
Replies: 16
Views: 32018

Re: SSL Phase Meter Schematic

Since I was never a practicing engineer my use of the "phase meter" was for setting 2 track azimuth. I almost never used it for multi track azimuth preferring the mono sum method. I'm glad I don't have to deal with tape any more. :| I could see how the SSL type which indicates correlation ...