Search found 569 matches

by emrr
Wed Jun 09, 2010 11:46 pm
Forum: Pro Audio Design
Topic: B+ and filament PSU problem
Replies: 13
Views: 21720

Re: B+ and filament PSU problem

another clarification, in case I wasn't. The 5V always starts. It's just that it shuts down when the 200V kicks on, in one particular switching pattern. Checking it again ASAP.
by emrr
Wed Jun 09, 2010 4:27 pm
Forum: Pro Audio Design
Topic: B+ and filament PSU problem
Replies: 13
Views: 21720

Re: B+ and filament PSU problem

I need to submit a drawing of the switch. I don't see a way that it could have any failure, and ever work at all. To be more clear, there is AC present on the primaries of both power transformers, as there should be. Thanks.
by emrr
Tue Jun 08, 2010 11:55 pm
Forum: Pro Audio Design
Topic: B+ and filament PSU problem
Replies: 13
Views: 21720

B+ and filament PSU problem

I have a custom tube preamp rack unit that's been out there for about 9 years, and the customer reports that sometimes it will make some sound, then fizzles out. Unit uses a pair of International Power regulated supplies. (1) 200VDC and (1) 5VDC. The 5VDC has OVP crowbar circuit, which I'm guessing ...
by emrr
Thu Apr 15, 2010 12:28 am
Forum: Pro Audio Design
Topic: Mid Side M-S Matrix Uses No Precision Resistors
Replies: 271
Views: 619504

Re: Mid Side M-S Matrix Uses No Precision Resistors

I don't think you are missing anything; maybe I'm missing something. :mrgreen: I think the crosstalk issue is fairly esoteric, and will have to be proven in practice, as to whether there's significant problems or not. May depend on the type of source material. I'm thinking it won't matter for most t...
by emrr
Tue Apr 13, 2010 12:41 pm
Forum: Pro Audio Design
Topic: "Modified phantom-powered microphone circuit reduces distortion," Dimitri Danyuk
Replies: 22
Views: 38345

Re: Electronic Design IFD: Modified Schoeps Capsule Design

I've always thought you were stuck using a minimum pad value close to 20dB, to preserve the loading characteristics for the mic with the average preamp. In practice and ignorance early on, I put a four position switch that added dual build out (for a U pad) to a 200 ohm shunt, for 0, -6, -12, -18 se...
by emrr
Mon Apr 12, 2010 12:56 pm
Forum: Pro Audio Design
Topic: "Modified phantom-powered microphone circuit reduces distortion," Dimitri Danyuk
Replies: 22
Views: 38345

Re: Electronic Design IFD: Modified Schoeps Capsule Design

Trivia: the Mackie uses the same amp for both preamp and line, and I am remembering the only practical difference (ignoring the differences for phantom power) is the addition of (2) 5-7Kish series resistors inline for the line input. I don't believe it is actually a U-pad.
by emrr
Mon Apr 12, 2010 10:51 am
Forum: Pro Audio Design
Topic: "Modified phantom-powered microphone circuit reduces distortion," Dimitri Danyuk
Replies: 22
Views: 38345

Re: Electronic Design IFD: Modified Schoeps Capsule Design

I remember Pro Audio Review looking at this question maybe a decade back, and I think their hottest discovery at the time was a TLM103, at something like +13 dBm. Of the preamps they were trying, only the Mackie was capable of dealing with full scale output. There were not a lot of preamps or mics o...
by emrr
Wed Apr 07, 2010 8:08 pm
Forum: Pro Audio Design
Topic: Mid Side M-S Matrix Uses No Precision Resistors
Replies: 271
Views: 619504

Re: Mid Side M-S Matrix Uses No Precision Resistors

Get down. Sounds excellent. I was guessing voltage dividers, so I understand the concern. Keep us posted.
by emrr
Tue Apr 06, 2010 10:31 am
Forum: Pro Audio Design
Topic: Mid Side M-S Matrix Uses No Precision Resistors
Replies: 271
Views: 619504

Re: Mid Side M-S Matrix Uses No Precision Resistors

Hey Paul, sounds like a tough soldering job. I'm thinking that the actual ratio of values in what you're building is such that absolute precision isn't terribly necessary to get results that are indistinguishable with slight variance. Of course, you don't want to build and find out the hard way. I j...