Search found 25 matches

by tubegeek
Tue Jun 18, 2013 7:47 am
Forum: Pro Audio Design
Topic: LC filter experiments, in Pultec MEQ context
Replies: 15
Views: 26750

Re: LC filter experiments, in Pultec MEQ context

Would anyone reading this thread have a schematic for a Langevin EQ252A or its rack mount equivalent, EQ270? This is a seven-band, "graphic" eq using passive bridged-T circuits.

A colleague has one that isn't working properly.

Thanks,

-j
by tubegeek
Tue Jun 18, 2013 7:45 am
Forum: Pro Audio Design
Topic: Very low level hum and how to get rid of it
Replies: 12
Views: 17861

Re: Very low level hum and how to get rid of it

In the context of high-voltage supplies, point-to-point wired, for vacuum tube circuits, the advice I have been given is: connect the power transformer center tap directly to the first filter cap after the rectifier. Connect the audio circuit ground directly to the last filter cap in the smoothing n...
by tubegeek
Mon Jun 17, 2013 11:40 pm
Forum: Pro Audio Design
Topic: Presenting "The Leslieator" - a work in progress
Replies: 10
Views: 17986

Presenting "The Leslieator" - a work in progress

On Sundays I mix sound for a church and, while my setup is quite functional, I'm always trying to do a little more with a little less. Case in point: I currently have a stereo mic setup on a very nice Leslie 122 cabinet (driven, just as it is ordained in the scriptures, by a very nice Hammond B3.) T...
by tubegeek
Tue Apr 16, 2013 5:30 pm
Forum: Pro Audio Design
Topic: Recommended implementation for THAT1512
Replies: 34
Views: 40698

Re: Recommended implementation for THAT1512

It works. The gain adjustment is odd but I was expecting that, I don't have a pot of the appropriate value. I tested it, I'm getting a maximum of 48 dB of gain, which is less than I expected with a step-up transformer. I haven't measured the transformers yet, I may have a smaller step up than I expe...
by tubegeek
Sun Apr 14, 2013 4:53 pm
Forum: Pro Audio Design
Topic: Recommended implementation for THAT1512
Replies: 34
Views: 40698

Re: Recommended implementation for THAT1512

JR: My drawing may be misleading. The connections at the XLR out jack are shown as if they are made on the XLR connector but (+, –, E and G) will actually be made by their own 4-pin connector, either a Molex type or possibly an RJ-11 or RJ-45 snap-in type to save some room. Depends on what I have at...
by tubegeek
Sat Apr 13, 2013 9:07 pm
Forum: Pro Audio Design
Topic: Recommended implementation for THAT1512
Replies: 34
Views: 40698

Re: Recommended implementation for THAT1512

I've got a single mic preamp channel almost finished on perf board. I've built this first one as a standalone mic pre stage to feed a line mixer via XLRs, running off a battery supply (+/- 18V rails.) I want to hear what it sounds like before I build up a bunch of channels. It's in three little boxe...
by tubegeek
Wed Mar 27, 2013 11:25 pm
Forum: Pro Audio Design
Topic: Level Detectors, Absolute Value, Peak and RMS
Replies: 35
Views: 70931

Re: Level Detectors, Absolute Value, Peak and RMS

Likely, I'm missing something, but - Isn't the behavior of the peak of the wave a whole lot more important than the zero-crossing behavior for level indicator application? What does distortion of the rectified wave even matter here? Wayne: are you looking at that output behavior so critically becaus...
by tubegeek
Tue Mar 26, 2013 7:55 pm
Forum: Pro Audio Design
Topic: Recommended implementation for THAT1512
Replies: 34
Views: 40698

Re: Recommended implementation for THAT1512

So in looking at the existing circuit (LINEMIXERSchematic.jpg) I see a couple of things that interest me. 1. The buffer ahead of the existing clip indicator (IC1B) looks like a good place to pull off a pre-fader, pre-pan signal - if I roll my own clip indicator I can repurpose that send as a pre-fad...
by tubegeek
Tue Mar 26, 2013 7:35 pm
Forum: Pro Audio Design
Topic: Level Detectors, Absolute Value, Peak and RMS
Replies: 35
Views: 70931

Re: Level Detectors, Absolute Value, Peak and RMS

If you have any hope of becoming a design engineer, read all the posted schematics, then design one of your own... 8-) Hope. Hmm. I guess I do hope for that. "Instead of a bum, which is what I am," to quote Terry Malloy. I am at the point, with reference to this design issue, that I don't even know...
by tubegeek
Mon Mar 25, 2013 6:09 pm
Forum: Pro Audio Design
Topic: Level Detectors, Absolute Value, Peak and RMS
Replies: 35
Views: 70931

Re: Level Detectors, Absolute Value, Peak and RMS

Excuse me, Wayne, but in another thread, JR had assigned me to design my own peak detector. You've TOTALLY screwed THAT up. Now, I do NOT suffer from NIH and this is an embarrassment of riches. Thank you. But it seems like I'm going to miss a learning opportunity..... of course, understanding what t...