CheersI don't own a balanced source yet, so never properly looked at the in's & out's of it. That could be my next, next-project
Possibly a Twisted Pear COD & IVY III feeding a BAL-BAL > HD650s ... hmmm!
For some light background reading on audio interconnection check this paper by Henry Ott - http://www.hottconsultants.com/pdf_files/Audio Interconnections.pdf and Linear Audio Volume 5 has an article by Bruno Putzeys also that is quite good reading and has some background on audio system grounding.
Owen: For SE input to the BAL-BAL would you connect the gnd to -ve input?
Hi Stammheim,
From what I can see, it looks like the PSU section is all correctly soldered, so you should be getting a proper +/-15VDC on the big electrolytics at the output of the regs. If you can measure to check it would be a good idea.
I can see that C3 and C4 are not correctly soldered and you have a cold joint on the left side of each.
Are R10 and R11 populated on the other side of the board? How do the joints look?
If it's hum you're getting, then my best guess is a cold joint on one of the resistors in the front end, so re-solder each of them and let the iron dwell a little longer to make sure solder flow on both the part and the pad.
As for the input, it needs to be wired between GND (the middle pad on the BAL input) and the separate solder lug labelled as SE on the board.
I marked everything up on the attached picture. Please re-check all your joints in the yellow circles, and re-solder the ones in the red circles.
If you can see any gold left on a soldered pad, there's a good chance you have a cold joint.
Let us know how it goes, and please post a pic of the other side if possible.
Cheers,
Owen
From what I can see, it looks like the PSU section is all correctly soldered, so you should be getting a proper +/-15VDC on the big electrolytics at the output of the regs. If you can measure to check it would be a good idea.
I can see that C3 and C4 are not correctly soldered and you have a cold joint on the left side of each.
Are R10 and R11 populated on the other side of the board? How do the joints look?
If it's hum you're getting, then my best guess is a cold joint on one of the resistors in the front end, so re-solder each of them and let the iron dwell a little longer to make sure solder flow on both the part and the pad.
As for the input, it needs to be wired between GND (the middle pad on the BAL input) and the separate solder lug labelled as SE on the board.
I marked everything up on the attached picture. Please re-check all your joints in the yellow circles, and re-solder the ones in the red circles.
If you can see any gold left on a soldered pad, there's a good chance you have a cold joint.
Let us know how it goes, and please post a pic of the other side if possible.
Cheers,
Owen
Attachments
I just finished testing 1 of 4 LPUHP amps, set for SE mode 15db of gain. Using my crappy test speaker everything seemed fine. Putting the driver up to my ear headphone style, with the volume muted, or the input unpluged, I have to strain my eardrum to hear a faint hum. Still need to check for DC offset.
The other 3 are almost ready to test as well, just need to mount the LME heat sinks on them. I hope they check out O.K. as well. I am not sure if I will get to it tonight though.
The other 3 are almost ready to test as well, just need to mount the LME heat sinks on them. I hope they check out O.K. as well. I am not sure if I will get to it tonight though.
I don't know.
They are too close to the lme heatsink to get a finger in the almost non existent gap. The side facing out is warmer (finger method) than a normal capacitor sitting in normal airstream.
It appears to me that the cap is running warm because it is so close to a warm to hot heatsink.
A cap that runs at 80ºC at the hottest part of the surface might be OK, if we know that the internal temperature is lower than that. Particularly if the majority of the surface runs at a temperature substantially below 80ºC.
But how do we measure the internal temperature of our electrolytics?
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Well, I soldered and checked everything twice, but same result. I also noticed that the voltage regulator is getting hot after only few seconds. It's the side, where Owen's fix is. I mean the shorted C6-pad. Could this be the failure? How can I check if it's still shorted?
Edit:
OK, C6 is shorted to the heatsink-screw on both sides, so it's shorted. Gonna try to scratch a little...
Edit2:
Fixed shorting, only one side of C6 has connection to GND. But: Problem ist the same!
Edit:
OK, C6 is shorted to the heatsink-screw on both sides, so it's shorted. Gonna try to scratch a little...
Edit2:
Fixed shorting, only one side of C6 has connection to GND. But: Problem ist the same!
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Hi Stammheim,
Can you check the following voltages for me (don't leave the unit on too long if the reg is getting hot)
1- The DC voltage on both bulk caps as indicated yesterday in red. This will tell us if the rail voltage is alright. Should be +/-15VDC.
2. Output to GND DC voltage. This should be less than 1mV.
3. To check the cuts in the board, please see this post:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-33.html#post3741079
If you have continuity between the indicated sides of the caps, and the output, then the cuts have been shorted.
You should not see a short circuit between the V- rail and the output!
Regards,
Owen
Can you check the following voltages for me (don't leave the unit on too long if the reg is getting hot)
1- The DC voltage on both bulk caps as indicated yesterday in red. This will tell us if the rail voltage is alright. Should be +/-15VDC.
2. Output to GND DC voltage. This should be less than 1mV.
3. To check the cuts in the board, please see this post:
http://www.diyaudio.com/forums/vend...-here-bal-bal-se-se-lpuhp-33.html#post3741079
If you have continuity between the indicated sides of the caps, and the output, then the cuts have been shorted.
You should not see a short circuit between the V- rail and the output!
Regards,
Owen
None of those resistance measurements sound quite right, so the caps must be holding a small charge which is messing with the meter.
Either way, it doesn't sound like it's shorted or it would measure a short.
Can you set up the meter in advance to measure across the speaker output (use alligator clips or wrap some wire around the probes) set the multimeter to measure DC, and plug in the amp briefly. Check the DC on the output.
If you see a negative voltage in the range of 1 to 15VDC, then the output is likely shorted to the - rail.
Perhaps a better picture of both cuts would help as well.
I'm starting to run out of ideas though.
Regards,
Owen
Either way, it doesn't sound like it's shorted or it would measure a short.
Can you set up the meter in advance to measure across the speaker output (use alligator clips or wrap some wire around the probes) set the multimeter to measure DC, and plug in the amp briefly. Check the DC on the output.
If you see a negative voltage in the range of 1 to 15VDC, then the output is likely shorted to the - rail.
Perhaps a better picture of both cuts would help as well.
I'm starting to run out of ideas though.
Regards,
Owen
I never did any smd work until I started playing with Owen's projects. Before soldering parts on the boards I would check each part, capacitor, resistor etc for the correct value. I would then solder in one part and then do several continuity tests on the circuit board to check if the part was soldered in properly and no shorts or opens existed. So far everything has worked first time. Then I would make changes to the boards to suit my particular needs. Sometimes slower is faster.
Hi Guys,
Just wanted to clarify that I got everything sorted with Stammheim offline.
He was using the same phase of the transformer output on each AC input which effectively short out one of the regulators (the positive one).
This serves as a nice reminder to everyone that it is imperative to use a proper dual secondary transformer and to fully float both AC inputs! A center-tapped transformer will not work with these amplifiers.
I will draw up a diagram when I get the chance to show the external connections and how they need to be made for additional clarity.
Hopefully Stammheim can report back when he gets both unit back up and running.
Thanks to everyone for their help and suggestions.
Cheers,
Owen
Just wanted to clarify that I got everything sorted with Stammheim offline.
He was using the same phase of the transformer output on each AC input which effectively short out one of the regulators (the positive one).
This serves as a nice reminder to everyone that it is imperative to use a proper dual secondary transformer and to fully float both AC inputs! A center-tapped transformer will not work with these amplifiers.
I will draw up a diagram when I get the chance to show the external connections and how they need to be made for additional clarity.
Hopefully Stammheim can report back when he gets both unit back up and running.
Thanks to everyone for their help and suggestions.
Cheers,
Owen
Good advice, I to work methodically and check as I go, but maybe not after each component. Also have a small tub of Rosin Flux which I brush onto the pads and components helping the solder to flow better.
My LPUHP parts should arrive on Friday... now trying to think up novel ways of casing them Converting the HD650's to balanced sounds straight forward enough. Might see if there's enough room in the case to convert my Pioneer DV-757Ai to balanced out. The I/V stage is Balanced to SE.
Good to hear you were able to help out Stammheim and get him back on track
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Hi guys,
OK, my failure. But one board was not fixed enough, so it had a shorted connection, which was not enough scratched. For people with a similar failure, try to measure as Owen wrote above!!!
I have another issue: Both boards work fine, when they have an own transformer. I just wanted to use only one transformer for both boards, but one board is humming then. I tried different connection-possibilities, but no success. Any idea here??
Anyhow: The listening-experience is really fine. Tested vs. the SA-50 and SA-98E is really audible diference, much more precisely, seem to recognize more details. So I'm happy with it to activate my AMT's...
Thanks and REALLY sorry for support :-D
Stammheim
OK, my failure. But one board was not fixed enough, so it had a shorted connection, which was not enough scratched. For people with a similar failure, try to measure as Owen wrote above!!!
I have another issue: Both boards work fine, when they have an own transformer. I just wanted to use only one transformer for both boards, but one board is humming then. I tried different connection-possibilities, but no success. Any idea here??
Anyhow: The listening-experience is really fine. Tested vs. the SA-50 and SA-98E is really audible diference, much more precisely, seem to recognize more details. So I'm happy with it to activate my AMT's...
Thanks and REALLY sorry for support :-D
Stammheim
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Here is a picture.
Instead of using a positive regulator chip and a negative regulator chip, opc used two negative regulator chips. But they are very very good negative regulator chips, better than the positive compliment, and you don't loose anything wiring it up that way. But the two secondaries have to be completely isolated, not center tapped.
So you shouldn't have any continuity (infinite ohms) on your ohmeter when measuring from the two secondary wires for the positive regulator to those for the negative regulator (transformer not connected to the circuit yet, of course).
Attachments
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Here is a picture.
Instead of using a positive regulator chip and a negative regulator chip, opc used two negative regulator chips. But they are very very good negative regulator chips, better than the positive compliment, and you don't loose anything wiring it up that way. But the two secondaries have to be completely isolated, not center tapped.
So you shouldn't have any continuity (infinite ohms) on your ohmeter when measuring from the two secondary wires for the positive regulator to those for the negative regulator (transformer not connected to the circuit yet, of course).
Yes I know about the negative regulators, Owen wrote about the fantastic result using this regulators. But it should be no barrier to use two amps with one transformer.
The transformer himself is OK and powering each amp fine, but only one connected.