[Build] CAPI HPA500, 500 Series Headphone Amplifier, Official Support Thread

[jsteiger]

At first quick glance, the LED leads seem pretty look and appear to be hanging off of the back of the solder pads. They can short to the ground plane so I would correct that.

You can check the right end of the 330R's to make sure the receiver is passing both left and right.

Might be silly to ask but have you swapped the XLR inputs at the back of the rack to make sure its not an external wiring thing?

 

[rockprocess]

Thanks, I’ll trim those leds.  I’ve swapped cables externally, swapped the opamps.  I’ve put two different test tones going into the unit on both channels so that I can tell if I hear the left side.  No luck on the left.

I’ve got no signal at r27 but full signal at r28.

 

[jsteiger]

Thanks, I’ll trim those leds.  I’ve swapped cables externally, swapped the opamps.  I’ve put two different test tones going into the unit on both channels so that I can tell if I hear the left side.  No luck on the left.

I’ve got no signal at r27 but full signal at r28.

R27 and R28 immediately follow the OPA2134 receiver amp. Test on their right ends closest to the OPA2134.

I would look for a cold solder joint or miss placed R with the following:
R30
R36-R40
C22
C26
C29-C30

 

[rockprocess]

Great advice Jeff.  I got it working.  Great sounding module!!!

 

[jsteiger]

Great advice Jeff.  I got it working.  Great sounding module!!!

Awesome!

What was it? Maybe it'll help someone in the future if you share what the issue was.

 

[rockprocess]

Thanks Jeff.  I’m embarrassed to say it was my fault, not the module.  I plugged one side into the extra jacks on my api 500 lunchbox.  I hadn’t used the far right side slots yet where the pass through jacks are.  Please excuse my stupidity!

 

[nicholasdover]

Hi guys

I made an initial mistake in a hurried and poorly lit build situation and put the wrong IC in A3, then when I corrected it, only one channel was working.  I switched A1 and A2 around, but no change so presumed I'd damaged A3. I just got a new IC for A3 through the mail and everything worked perfectly for a couple of minutes, but now one side has gone down again, and A1/A2 switch isn't curing it. So it seems my build is blowing one channel of A3 - is that possible? What could deliver a damaging blow to the IC? I did plug in and out of the extension jig without power down ( it was the only module in the rack, no power button, impatient, reckless...) so is there possible harm from "hot switching" like that?
Thanks
Nick

 

[jsteiger]

Hot swapping should not be an issue. It could also be bad solder joints somewhere. I mentioned in a post above where to check for audio immediately after the receiver chip. I think other folks have had trouble with faulty solder joints where the 2 boards connect.

 

[nicholasdover]

I'll check the solder joints tomorrow, but that side of things was neat I think and it did work fine for that couple of minutes. I made a mistake with the transistors too which is rectified now but I guess they could have been harmed? They weren't reversed in slots or anything, but 2 were in wrong positions. It's embarrassing... I have my reasons....
I can get hold of the IC's and transistors here (UK) if necessary but they're not cheap so it'd be good to know I'm replacing the right things if it comes to that.
Couple of new A3 IC's coming tmrw so I'll see if same thing happens.

 

[radtunez]

Hi Jeff,

I am a bit puzzled, as I thought this build was a breeze, but alas, my HPA is not functioning. At the moment, I am only getting Left channel signal and even that is very low. The pot is very scratchy and ceases to function after 3 o'clock. I have double checked all my placement, but I attached a photo just in case. I checked all joints and carefully redid any that were remotely suspect. I also cleaned the PCB well. The only issue that I am wondering about is there is a bit of daylight between the shroud and the ALP PCB on JP3. But the pins are not touching the L bracket beneath. I redid and cleaned the joints to the main PCB, and the soldering of pins to the ALP pcb look good to me. What am I missing?

Thank you so much,
Ryan

 

[radtunez]

Hi Jeff,

I am a bit puzzled, as I thought this build was a breeze, but alas, my HPA is not functioning. At the moment, I am only getting Left channel signal and even that is very low. The pot is very scratchy and ceases to function after 3 o'clock. I have double checked all my placement, but I attached a photo just in case. I checked all joints and carefully redid any that were remotely suspect. I also cleaned the PCB well. The only issue that I am wondering about is there is a bit of daylight between the shroud and the ALP PCB on JP3. But the pins are not touching the L bracket beneath. I redid and cleaned the joints to the main PCB, and the soldering of pins to the ALP pcb look good to me. What am I missing?

Thank you so much,
Ryan

 

[adalogue]

Great kit! Accidentally swapped two opamps and one got hot, but works like a charm, and sounds great!

 

[Vermillion Sound]

Hi Folks! Just finished my HPA 500 build. I can tell it sounds really nice, however my right side is lower than my left side. But both sides work at equal level when switched to mono. I swapped the OPA134P chips just to be sure, but the issue remains. Nothing looks damaged and the solder joints look great. I already checked the aforementioned points. Is there a voltage checklist at certain points posted anywhere? Thanks for the help!

 

[jsteiger]

Hi Folks! Just finished my HPA 500 build. I can tell it sounds really nice, however my right side is lower than my left side. But both sides work at equal level when switched to mono. I swapped the OPA134P chips just to be sure, but the issue remains. Nothing looks damaged and the solder joints look great. I already checked the aforementioned points. Is there a voltage checklist at certain points posted anywhere? Thanks for the help!

You most likely have misplaced resistors. Summing to mono will combine both sides so it won't tell you much.

 

[Vermillion Sound]

You most likely have misplaced resistors. Summing to mono will combine both sides so it won't tell you much.

I compared my build to the manual again. It all seems correct. Anything obvious I’m missing?

 

[jsteiger]

Could also be a bad solder joint between the pot PCB.

 

[Vermillion Sound]

I touched the solder joints on the pot PCB, though they looked alright beforehand. Tested again and now that I listen, it sounds like the mid signal is in the left channel and the side signal is in the right channel. I think this because the vocals and drums are mainly in the left channel. A very curious thing indeed. I wondered if this module is compatible with my chassis? Using a Rupert Neve R6 on channel 1. Have a CAPI 511 on order from a builder. Thoughts?

Thanks so much for the quick responses!

 

[Vermillion Sound]

Just went through and touched all the solder joints for the pot on the pot PCB as well as all points for the components on the right channel. Still the same issue however. I was curious if there's anyone I can send this to if I'm not able to figure this out quick?

 

[Conroski]

Hey I’m having a similar issue, what turned out to be your problem?

 

[CaptainVideo]

Jeff;

I have a HPA500 that I recently built and functionally everything works but the issue that I am having is that the output is distorted. If I drop the input signal then the HPA500 cleans up until I put the volume back up to compensate. I will review all resistor and component placement but just reaching out to see if there are any common solutions to this distortion issue. Also have to note that the output volume is around 65 to 70db and this is operating in a selected mode of mono.

Thank you for your products and assistance with DIY kits!

Regards

CCR