JLM AUDIO

Yes will work fine. But I wonder why no one has recalculated all the resistor values in this whole design as the noise floor and crosstalk could be much improved without any real change to the circuit. It's an exact copy of old API circuitry, so authenticity is the paradigm. :D But I only care for ...

Perfect. This inductor should be as close to the -in as physically possible. Yes, that's where I put it. 8) Do you have a copy of this sections schematic? Sure: ACA_Booster.jpg Everything, including the dotted part, is actually there. As in the summing section I have used bipolar caps and will remo...

Joe Malone wrote:
The 1uF mono cost about the same as the 0.1uF mono in bulk so we use them as you can get super low esr much closer to opamp power pins and few 1uF add up to electro size uF. So makes most unstable opamps super stable.

Very interesting, thanks!

Thanks Joe. I thought offset might be the problem. Since adding output caps is not really an option I guess I'll use modern op amps after all... Audio path Cap is 1uF MKT polyester not ceramic. If lower input impedance is need then cap needs to be increased to 10uF etc so Non Polar electro will be b...

Thanks Joe. I use a 20uH inductor at the moment. Self-wound with a ferrite bead. I couldn't detect a change of the frequency response in the audio band. BTW, what about the buffer stage after the fader? In the feedback path it has a 47k resistor with a 47pf cap on top. Would this be a good candidate...

Hi Joe, looks like this is exactly what I need as balancing/output driving stage for my discrete multichannel DAC! :D I'd like to use NE5532 (got old Signetics ones that I consider the best sounding op amp out there), any reason why they wouldn't work here? What can you expect WRT to SNR and THD? Al...

Cool, thanks!

I forgot to add an inductor to the schematics. I added it between the input cap and the op amp's inverting input to reduce RF reaching the summing amp and increase stability. This shouldn't make a difference WRT to implimentation, I think.

Thanks Joe! I had a JLM99V in one of my BAs but it got destroyed accidentally. I remember it sounded better than all the other op amps I've tried...

The console has 32 channels + 8 returns, so 40 get summed to each side of the master bus in total.

Thanks Joe, here are the schematics. The channels are summed through 22k resistors. Consolesumming.png I would remove R14 to account for the DC offset at the output of the JLM99V. Signal path / DC blocking caps are bipolars, so no need to change anything there. How would you describe the sound of th...

Hi Joe,

does the JLM99V make a good summing amp? I'd like to use it in the CAPI 2-ACA for this purpose. I would remove the resistor following the op amp, so there is a cap in place to prevent DC from magnetizing the transformer.

Thanks!

Thanks Joe! I'll report back when I've got the JLM14 installed.

Thank you Joe, sounds great. Just two more question: Will this configuration work well with balanced as well as unbalanced sources? Also, how much DC on the input can the transformer handle?

Also, won't I have to attenuate the signal at some point so the converter doesn't clip?

Yes remove R1, R2 C1, C2 and R3, R4 to isolate the opamp circuit. wire JLM14 yellow to XLR pin 2 wire JLM14 blue to XLR pin 3 wire JLM14 red to TP6 VINR+ (PCM4222 pin 2) wire JLM14 green to TP5 VINR- (PCM4222 pin 3) wire JLM14 black to either VCOMR pin 48 (should solder to R23 end that connects to ...

Yes remove R1, R2 C1, C2 and R3, R4 to isolate the opamp circuit. wire JLM14 yellow to XLR pin 2 wire JLM14 blue to XLR pin 3 wire JLM14 red to TP6 VINR+ (PCM4222 pin 2) wire JLM14 green to TP5 VINR- (PCM4222 pin 3) wire JLM14 black to either VCOMR pin 48 (should solder to R23 end that connects to ...