Search found 5447 matches
- Mon Dec 29, 2008 1:24 pm
- Forum: Pro Audio Design
- Topic: Mid Side M-S Matrix Uses No Precision Resistors
- Replies: 271
- Views: 619307
Re: Mid Side M-S Matrix Uses No Precision Resistors
I also tried the precision bypass mode and the crosstalk improved. I swapped the L&R channels from prior measurements. By hand picking 1246/1240 combinations I can make the L to R as good as the R to L numbers. Unfortunately on this prototype the left channel 1246 is soldered to a flying lead. T...
- Mon Dec 29, 2008 12:08 pm
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
They were advised by THAT to use separate pads and buffers at + and - control ports. One inverting buffer and one non inverting buffer. This prevents hitting the VCA with a correlated noise source (in first buffer?). This seems like it should be a modest phenomenon but perhaps measurable with noisy...
- Mon Dec 29, 2008 10:24 am
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
I do want to forward Igor's article to THAT however and ask about the differntial Ec drive. I really need to print it but I don't think I've seen that approach used before - just differential audio path and parallel is what I've seen.
Thanks for sending it Igor and joining us here in the forum.
Thanks for sending it Igor and joining us here in the forum.
- Mon Dec 29, 2008 8:41 am
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
Wayne, have you ever discussed something like this with lads at THAT? The schematics you posted shows the typical parallel up a bunch, but that's to drop into some old sockets to make up for smaller geometry transistors. I wanted to show the Cv pads and buffers. The parallel-up-a-bunch doesn't make...
- Sun Dec 28, 2008 2:06 pm
- Forum: Pro Audio Design
- Topic: Mid Side M-S Matrix Uses No Precision Resistors
- Replies: 271
- Views: 619307
Re: Mid Side M-S Matrix Uses No Precision Resistors
When I originally designed the matrix I was concerned about gain build-up during encoding in the Mid (L+R) channel and also in the decoder which produces not L and R, but 2L and 2R . In anticipation of that I designed the following circuit and then allowed myself to get talked out of using it off-fo...
- Fri Dec 26, 2008 1:54 pm
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
The LM833 is compared by Douglas Self to the NE5532 with slightly higher noise and somewhat less drive capability. I think the 833 was National's answer to the 5532 and it's not a bad choice either. There may be a modest need for speed and output current in this stage to keep the output impedance fr...
- Fri Dec 26, 2008 12:00 pm
- Forum: The Peabody Lounge
- Topic: Merry Christmas!
- Replies: 3
- Views: 7741
Re: Merry Christmas!
It's 77 here right now at noon with a high in the low 80s predicted. Great weather for doing after-Christmas cleanup.
If it dries out I may go for a bike ride. We've had really high humidity and things are very slick for 1-1/4" English racer tires.
If it dries out I may go for a bike ride. We've had really high humidity and things are very slick for 1-1/4" English racer tires.
- Fri Dec 26, 2008 11:52 am
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
so low gain opamp noise is not as much of a concern as source impedance at control ports. You are correct that the op amp should buffer the pad or have less than unity (inverting) gain. I misspoke previously. An op amp's impedance rise vs frequency is particularly critical with most BIFETS showing ...
- Thu Dec 25, 2008 7:49 pm
- Forum: The Peabody Lounge
- Topic: Merry Christmas!
- Replies: 3
- Views: 7741
Re: Merry Christmas!
Merry Christmas Roger and everyone!
Just back from a long day of eating....
Just back from a long day of eating....
- Wed Dec 24, 2008 11:40 am
- Forum: Pro Audio Design
- Topic: OTB Mixer Using Current Summation
- Replies: 137
- Views: 214225
Re: OTB Mixer Using Current Summation
John - One op amp driving one port would be best. We might consider however having a resistive attenuator at the Ec and using something more like 20dB/V rather than the native 6.1 mV/dB. As long as the source impedance at Ec is low the attenuator would not add significant noise or CV modulation. Off...