Search found 184 matches

by chrisp
Sat Nov 26, 2011 11:41 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 183334

Re: BAN Build Thread

Thanks Joe - looks very easy. For those who have not tried it, Mid-Side recording is a stereo recording arrangement that uses an omni or cardiod ("Mid") mic directed to the sound source and a figure 8 ("Side") mic whose two response planes are perpendicular to the sound source (ie one of the "dead z...
by chrisp
Fri Nov 25, 2011 4:16 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 183334

Re: BAN Build Thread

No rush, Joe - enjoy your weekend
by chrisp
Fri Nov 25, 2011 9:35 am
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 183334

Re: BAN Build Thread

Is the balanced signal take off point around the 2K2 resistors between the opamps? And is the idea that you can use those 2K2s as mix resistors? Or am I barking up the wrong tree as usual?
by chrisp
Mon Nov 21, 2011 3:46 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 183334

Re: BAN Build Thread

Thanks Joe - that would be great.

I've made up an MS encode maxtrix for balanced signals before, but it was 8 resistors and not switchable - yech! So I am fascinated by the ol' JLM design magic...
by chrisp
Mon Nov 21, 2011 2:10 pm
Forum: JLM Audio Kits
Topic: BAN Build Thread
Replies: 129
Views: 183334

BAN Unbalance Output

Joe, I'm looking at a pair of BANs as a pre for stereo miking. I have a little PCB design to do mid-side decoding that I can switch in and out, but it works on unbalanced signals. Is there any unbalanced take off point on the BAN PCB just prior to the outputs? Will TP3 and ground do it for me? I cou...
by chrisp
Thu Apr 28, 2011 10:05 am
Forum: JLM Audio Kits
Topic: JLM Transformer mods for GAP 73, CL 7602 Mk1 and Mk2
Replies: 4
Views: 20009

Re: JLM Transformer mods for GAP 73, CL 7602 Mk1 and Mk2

Joe Malone wrote:give these pres some real fat Neve like Mojo
... or you might instead just build yourself some BA's for fat AND silky
by chrisp
Fri Oct 22, 2010 9:40 am
Forum: JLM Audio Kits
Topic: led vu meters
Replies: 9
Views: 10839

Re: led vu meters

Hey Izzi and Joe I'va done a little 7 LED PPM meter circuit using the LM3915, and have built a 10 LED VU using the LM3916. To be honest, the IC's are a little prone to oscillate so you need to be careful in layout etc, but with a bit of patience you do get there. The datasheets show circuits for pea...
by chrisp
Thu Sep 16, 2010 7:48 am
Forum: JLM Audio Kits
Topic: Hybrid Op build questions
Replies: 10
Views: 13395

Re: Hybrid Op build questions

3. Only need to remove 47uF next to BD139 if running the Hybrid in the BA or BAD or BAN PCB's. 4. To disable DC servo just do NOT solder the servo pads under the hybrid PCB together. Do NOT remove any parts as this may make the servo opamp oscillate and degrade the hybrid audio opamp section. There...
by chrisp
Tue Sep 14, 2010 9:32 am
Forum: JLM Audio Kits
Topic: Hybrid Op build questions
Replies: 10
Views: 13395

Re: Hybrid Op build questions

Jonte For information, the Hybrid's actual amp circuit uses just one half of the IC opamp in an open loop (no feedback) configuration as an input buffer, ahead of the transistor push/pull amplifier. Joe's idea is to use the second (unused) half of the opamp as a DC servo - a mechanism that takes the...
by chrisp
Sun Sep 12, 2010 9:57 am
Forum: JLM Audio Kits
Topic: Hybrid Op build questions
Replies: 10
Views: 13395

Re: Hybrid Op build questions

Okay - if other opamps work in the BA amp slot just fine, then you've identified the problem lies in the Hybrid build and not with the BA build or its onward connections. "little flashes" are A Bad Thing(tm). Could be something like a lifted pad (which can be very hard to see) where the pad solder h...
by chrisp
Sat Sep 11, 2010 2:54 pm
Forum: JLM Audio Kits
Topic: Hybrid Op build questions
Replies: 10
Views: 13395

Re: Hybrid Op build questions

Hi Jonte So far as I know, the BD140 is a stock standard PNP transistor, and any brand that's up to spec should be OK. Do not use the lesser power BD136 or 138 even though they are PNP. As for trouble shooting, are you running in class A or class A/B (or switching between the two?) DC servo? It soun...
by chrisp
Mon Aug 30, 2010 11:08 am
Forum: JLM Audio Kits
Topic: BA working great, unusual problem though...
Replies: 1
Views: 4195

Re: BA working great, unusual problem though...

That's normal, Timoski The caps on the power supply store energy (as well as even out the spikes), so when you switch off that energy is slowly drained (the LED, is the major current drain on the cap's power after switch off, so when you get the LED in place it will improve the power down significan...
by chrisp
Thu Aug 19, 2010 3:49 pm
Forum: JLM Audio Kits
Topic: vintage console ic mic pre's
Replies: 1
Views: 5050

Re: vintage console ic mic pre's

Hi Weroflu The same can be said for some old synths, yes? Them older chipped keyboards are getting quite a vintage shine. I think there are bigger issues than just the choice of IC for the opamps. Its about board design, getting right signal levels in the signal chain, having the right headroom in t...
by chrisp
Sun Aug 08, 2010 4:38 pm
Forum: JLM Audio Kits
Topic: BA BA2 BA4 BAD Dual99v Build Thread
Replies: 335
Views: 349438

Re: BA BA2 BA4 BAD Dual99v Build Thread

What, like my matched pair of Reslo ribbons?

Nah, I'm joking - LOW it is. Thanks for the response.
by chrisp
Sat Aug 07, 2010 8:04 am
Forum: JLM Audio Kits
Topic: BA BA2 BA4 BAD Dual99v Build Thread
Replies: 335
Views: 349438

Re: BA BA2 BA4 BAD Dual99v Build Thread

I'm just finishing up a couple of BAD cards using the VTX 102 003 input transformer, which can be wired low (6.45) or high (12.9) gain. Given the BAD isn't exactly short on gain (we'd be talking 74.5db vs 81db as the choices!), my instinct is to use the low gain jumper. One reason for wiring high mi...