is that one channel to ground? or + to - ? also do remember that may be 2mv into the huge impedance of your meter, across a headphone impedance it will be MUCH smaller
but yes, measurements need to have the inputs shorted (both to signal/input ground), short them it should be zero at the output. with the input floating you are doing pretty well at 2mv
but yes, measurements need to have the inputs shorted (both to signal/input ground), short them it should be zero at the output. with the input floating you are doing pretty well at 2mv
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well with the input floating, you are essentially measuring the difference between the rails (not literally) plus maybe a bit of DC leakage and RFI, so I guess you matched the PSU rails well on that side.
essentially you could short them to each other, to ground, or even to a DC voltage, as long as its the same thing each is connected to and not floating.
essentially you could short them to each other, to ground, or even to a DC voltage, as long as its the same thing each is connected to and not floating.
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Hi gusp:
I hooked up the WIRE to my Twisted Pear Audio Beffalo II/IVY set up and discovered some problems. I have both channel PSU for the WIRE set at +/-14.5V. The left channel appears to be working fine but the right channel sounds intermittent with cracking noise and significatly lower in level.
I double checked and the IVY is working properly. The output DC on both channels of the WIRE when connected with the IVY are around 4 mv which I believe came from the IVY. (My IVY always has 4mv or so DC on the outputs.)
Not able to visually identify any suspect, I measured the input DC, the beoken channel has 155mv DC measured between +/- and ground while the working channel has close to 0 DC. If I unhook the inputs from the IVY, the broken channel DC measured some 13.5V while the working channel only measures 34 mv!!!
The weird thing is that I then measured the PSU output voltage and now I am getting 0L (out of range) reading from my Fluke multimeter.
I am totally baffled and do not know where to look next. Any ideas what I chould check or do next?
I had to apply lots of heat when soldering the heatsink. could I have damaged the buffers?
Sorry I do not have pictures - was 1am when I quit but can take some and post them if that'll help!
Any thoughts you or anyone has are greatly appreciated!
I hooked up the WIRE to my Twisted Pear Audio Beffalo II/IVY set up and discovered some problems. I have both channel PSU for the WIRE set at +/-14.5V. The left channel appears to be working fine but the right channel sounds intermittent with cracking noise and significatly lower in level.
I double checked and the IVY is working properly. The output DC on both channels of the WIRE when connected with the IVY are around 4 mv which I believe came from the IVY. (My IVY always has 4mv or so DC on the outputs.)
Not able to visually identify any suspect, I measured the input DC, the beoken channel has 155mv DC measured between +/- and ground while the working channel has close to 0 DC. If I unhook the inputs from the IVY, the broken channel DC measured some 13.5V while the working channel only measures 34 mv!!!
The weird thing is that I then measured the PSU output voltage and now I am getting 0L (out of range) reading from my Fluke multimeter.
I am totally baffled and do not know where to look next. Any ideas what I chould check or do next?
I had to apply lots of heat when soldering the heatsink. could I have damaged the buffers?
Sorry I do not have pictures - was 1am when I quit but can take some and post them if that'll help!
Any thoughts you or anyone has are greatly appreciated!
actually those PSUs are tricky little suckers, harder than the amp board.
there could be all manner of suspects here, need pics, as close as you can. the heatsink is live, where its soldered to and where the buffer tab is soldered to is the negative rail and you could possibly have shorted the rail to ground with the heatsink. the opamps are pretty bulletproof, but the regs may have been damaged with a short like that.
need pics
there could be all manner of suspects here, need pics, as close as you can. the heatsink is live, where its soldered to and where the buffer tab is soldered to is the negative rail and you could possibly have shorted the rail to ground with the heatsink. the opamps are pretty bulletproof, but the regs may have been damaged with a short like that.
need pics
I would guess it's a solder short somewhere on the input side of things. Pay close attention to the cap soldered to the VOCM pin.
There are some vias that are close to pads, but cannot be bridged to those pads. Double check all the joint on the bad board and make sure they are alright. Reflowing all the joints is probably not a bad idea.
It seems unlikely that heat would have damaged the parts, and they're usually quite tolerant to shorts and even reversed supplies.
Like qusp said, post some good macro pictures of the board itself, as we'll see if we can spot anything out of place.
Regards,
Owen
There are some vias that are close to pads, but cannot be bridged to those pads. Double check all the joint on the bad board and make sure they are alright. Reflowing all the joints is probably not a bad idea.
It seems unlikely that heat would have damaged the parts, and they're usually quite tolerant to shorts and even reversed supplies.
Like qusp said, post some good macro pictures of the board itself, as we'll see if we can spot anything out of place.
Regards,
Owen
Thanks guys! Will follow your recommendations to see I can identify and fix the problem.
Any ideas that the PSU output voltage would become out of range? This sympton actually showed up twice. When I first experience the right channel problem, I immediately measured the PSU and got the same out-of-range reading. I then di-soldered the wires connecting the PSU to the main board and verified the PSUs were still measured +/-14.5V without load.
I then wired the PSU and main board back together again and at first I was able to measure +/- 14.5V supply but a few minutes later it was out-of-range again. This sympton applies to both PSUs. Very odd!
Any ideas that the PSU output voltage would become out of range? This sympton actually showed up twice. When I first experience the right channel problem, I immediately measured the PSU and got the same out-of-range reading. I then di-soldered the wires connecting the PSU to the main board and verified the PSUs were still measured +/-14.5V without load.
I then wired the PSU and main board back together again and at first I was able to measure +/- 14.5V supply but a few minutes later it was out-of-range again. This sympton applies to both PSUs. Very odd!
Hi Owen and gusp:
I visually inspected the non-working board for possible shorts and re-flowed all the solder points except those of the heat sinks and checked to make sure the heat sinks are not accidentally shorted where they should not. The problem persists after all this.
Both PSU's appear to be working fine - outputting +/- 14.5V as intended. The issue I reported in my previous post may just be an user error.
I am seeing the same symptoms: ~13.7DC on the input when measured from + to ground and - to ground while the working channel measured ~34mv. No DC on the output end (~1.8mv).
I have posted a couple of pictures of the board hoping you can help detect any suspicious culprits.
Any help you can offer is much appreciated!
I visually inspected the non-working board for possible shorts and re-flowed all the solder points except those of the heat sinks and checked to make sure the heat sinks are not accidentally shorted where they should not. The problem persists after all this.
Both PSU's appear to be working fine - outputting +/- 14.5V as intended. The issue I reported in my previous post may just be an user error.
I am seeing the same symptoms: ~13.7DC on the input when measured from + to ground and - to ground while the working channel measured ~34mv. No DC on the output end (~1.8mv).
I have posted a couple of pictures of the board hoping you can help detect any suspicious culprits.
Any help you can offer is much appreciated!
Hi MWL168,
Everything looks pretty good in the pictures, which points towards a damaged OPA op-amp.
Before replacing it though, there are a few things you can double check to be sure.
1. The VOCM pin via is very close to the supply pin via going to the bypass cap. Make sure there is no solder short between the two. Check for continuity with a meter to be sure.
2. Measure both supply nodes (+/-) to GND to make sure there are no direct shorts on the amp board.
If the above two items check out OK, then my best guess would be that the front end op-amp somehow got damaged (over heating or over voltage) and failed.
See the attached picture for the node referenced in (1).
Cheers,
Owen
Everything looks pretty good in the pictures, which points towards a damaged OPA op-amp.
Before replacing it though, there are a few things you can double check to be sure.
1. The VOCM pin via is very close to the supply pin via going to the bypass cap. Make sure there is no solder short between the two. Check for continuity with a meter to be sure.
2. Measure both supply nodes (+/-) to GND to make sure there are no direct shorts on the amp board.
If the above two items check out OK, then my best guess would be that the front end op-amp somehow got damaged (over heating or over voltage) and failed.
See the attached picture for the node referenced in (1).
Cheers,
Owen
Attachments
Hi Owen:
Many thanks for your help. I got it to work!!!
As you suspected, there was a short between C34 to one of the via close to the OPA1632. I should have spotted this problem after your first response - I was measuring the connectivity points and comparing the working channel to the non-working one. I must have missed this one - the cap and the via are so close together that I actually only spotted it after doing the measurement under a magnifier - the tip of the meter probe is literally larger than the gap
. Sorry for wasting your and gusp's time on such a obvious problem.
I am listening to the WIRE driven by the Buffalo II/IVY front end through my HD650 and really enjoying it. I am going to try my LCD 2 later.
I will post the finished product later (everything in a chassis, etc.). Unfortunately I accidentally fried my Placid HD BP PSU during the process and have to wait for a new kit to be delivered and built.
This WIRE headphone amp has a very significant meaning to me personally. If I botched it up and could not complete it, it would be a regret for the rest of my life.
Again many thanks to you and gusp for both the wonderful kit and the help and support!
Many thanks for your help. I got it to work!!!
As you suspected, there was a short between C34 to one of the via close to the OPA1632. I should have spotted this problem after your first response - I was measuring the connectivity points and comparing the working channel to the non-working one. I must have missed this one - the cap and the via are so close together that I actually only spotted it after doing the measurement under a magnifier - the tip of the meter probe is literally larger than the gap
. Sorry for wasting your and gusp's time on such a obvious problem. I am listening to the WIRE driven by the Buffalo II/IVY front end through my HD650 and really enjoying it. I am going to try my LCD 2 later.
I will post the finished product later (everything in a chassis, etc.). Unfortunately I accidentally fried my Placid HD BP PSU during the process and have to wait for a new kit to be delivered and built.
This WIRE headphone amp has a very significant meaning to me personally. If I botched it up and could not complete it, it would be a regret for the rest of my life.
Again many thanks to you and gusp for both the wonderful kit and the help and support!
Yes...
It's in the works right now. I will be offering all variants in a new layout that is designed to fit in an extruded chassis.
I'll be offering bare PCBs, completely assembled PCBs, and likely a fully assembled product style version.
Stay tuned here for a link in the coming weeks.
Cheers,
Owen
It's in the works right now. I will be offering all variants in a new layout that is designed to fit in an extruded chassis.
I'll be offering bare PCBs, completely assembled PCBs, and likely a fully assembled product style version.
Stay tuned here for a link in the coming weeks.
Cheers,
Owen
Thanks Owen and all! I am real happy that I got the WIRE working too.
It's too early to even give an impression yet. I am going to let it burn-in a bit first. Up till now, I have been mostly listening to the Kevin Gilmore's Dynalo (AMB PCB build) configured to single-end but using two separate two-channel PCB's. I really like the sound - it's my reference among many other amps I have access to. I have difficulty getting the balance configuration to work (using each stereo board as a single channel but only one differential input and gain stage). I've received some tips from Kevin but have not actually tried them yet.
Here is what my "work bench" looks like. The huge PSU for the IVY is a Speedo from the now defunct DIYZONE and will be replaced by the Placid HD BP. I replaced the TRS on the Cardas cable on the HD650 to a 4-pin XLR as you can see in the picture.
Best!
It's too early to even give an impression yet. I am going to let it burn-in a bit first. Up till now, I have been mostly listening to the Kevin Gilmore's Dynalo (AMB PCB build) configured to single-end but using two separate two-channel PCB's. I really like the sound - it's my reference among many other amps I have access to. I have difficulty getting the balance configuration to work (using each stereo board as a single channel but only one differential input and gain stage). I've received some tips from Kevin but have not actually tried them yet.
Here is what my "work bench" looks like. The huge PSU for the IVY is a Speedo from the now defunct DIYZONE and will be replaced by the Placid HD BP. I replaced the TRS on the Cardas cable on the HD650 to a 4-pin XLR as you can see in the picture.
Best!
