I'm stuck with testing my O2 (built from jds-labs kit) - the resistance measured all fine (R10, R11, R15, R18 are 1.3 Ohm instead of 1 but it seems like not a big deal).
The DC voltage measurement (AC plugged, amp is on, U2 installed, the rest isn't) reveals problems though: U2 and U3 are totally wrong (I use DIP sockets).
For example U4 pins measured as -0.42 -0.4 -8.96 instead of expected -11.8 -10 -11.8
The VDC at D5, D1 is also wrong.
Any ideas what could be causing it? Where should I look into?
I've checked components polarity and shorts - everything seems to be fine and clear.
The DC voltage measurement (AC plugged, amp is on, U2 installed, the rest isn't) reveals problems though: U2 and U3 are totally wrong (I use DIP sockets).
For example U4 pins measured as -0.42 -0.4 -8.96 instead of expected -11.8 -10 -11.8
The VDC at D5, D1 is also wrong.
Any ideas what could be causing it? Where should I look into?
I've checked components polarity and shorts - everything seems to be fine and clear.
Have you worked your way through the fault-finding guide I put together ?
Its in post #1 but the link is here,
http://www.diyaudio.com/forums/head...eadphone-amp-diy-project-189.html#post3806667
How about not so easy fix?
Could you point me towards some attempts to fix that?
There is nothing straightforward. One possibility would be to permanently link out the switch and fit a single switch to act on the comparator directly. A simple logic on/off with a pushbutton could be designed too. The comparator would have to be replaced with a micro power device, the LED voltage reference also replaced with a micro power alternative. The resistors would need recalculating and scaling upwards to minimise current draw when off.
So not easy... its a major rework of the power supply.
It might be possible to design a small add on to mute the output for a few seconds at power on and to give a quick mute at power off but again, its not a quick option. Its a serious bit of design to get it right.
Honestly I'd probably just use a good software resampler for such exotica and downsample to something more common - anything beyond 96k is way overkill for audio anyway. The optimized SoX resampler for Foobar2k, for example, gives essentially perfect quality at depressingly low CPU usage (about 1% for 44.1 --> 96 on this 6-year-old machine - those who were around in the olden days will remember somewhat different figures). You just need to make sure that you've got a bit of headroom in case the material is a bit on the hot side mastering wise.
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It makes no difference if batteries are not used. In or out, they do nothing.
Stumped on channel balance
Hello, I've recently completed my o2 and I'm having a little bit of a channel balance problem. Some of the mids sound like they're coming at me through a tube.
I've followed the guide posted here as well as looked over NwAvGuy's troubleshooting guide and discovered that my s2 leg was touching the via.
After I fixed that I was able to complete the test guide here without any fails and regained some of the balance, but not all of it.
I know it's been stated that measuring onboard resistances doesn't mean anything, but I noticed that my r20, and r14 read 10k in board, and my r5 reads 230k.
Can you think of any other reasons why I might be getting channel balance problems?
Thank you!
Hello, I've recently completed my o2 and I'm having a little bit of a channel balance problem. Some of the mids sound like they're coming at me through a tube.
I've followed the guide posted here as well as looked over NwAvGuy's troubleshooting guide and discovered that my s2 leg was touching the via.
After I fixed that I was able to complete the test guide here without any fails and regained some of the balance, but not all of it.
I know it's been stated that measuring onboard resistances doesn't mean anything, but I noticed that my r20, and r14 read 10k in board, and my r5 reads 230k.
Can you think of any other reasons why I might be getting channel balance problems?
Thank you!
OK, first thing then is to lift both C13 and C14 where they go to the wiper of the pot and "swap" the connections over so that the wiper that fed C13 now feeds C14 and vice versa. If the fault swaps over then the problem is in the front end.
You can't read R5 in circuit but there won't be a problem in that area if the rails are up and correct.
It may well be worth you rechecking around that via that had the problem.
You can't read R5 in circuit but there won't be a problem in that area if the rails are up and correct.
It may well be worth you rechecking around that via that had the problem.
Thanks, I've missed it at a first glance. It's actually very similar to "official" troubleshooting guide although there U2 is installed and in your case it isn't - should this make any difference for measuring regulators?
Anyway, I've measured and found that I've got wrong DC readings around D1 but not D5:
D1 -0.28V (12V expected)
D1-stripe -0.46V (11.8V expected)
D5 -11V (-11.8V expected)
D5-stripe -11.16V (-12V expected)
By "stripe" I mean the end of diod with the stripe on it. I've checked again and both D1 and D5 are installed correctly and voltage before regulators is correct as well (22.78V and -22.68V respectively). So according to your post it should be "regulators themselves". Could you help me to figure out what could be wrong with them? Where should I look for faults and what else could I measure to narrow it down further?
I'm also puzzled that D5 readings are correct while D1 id faulty - what could be causing such assymmetry?
You need to carefully check that there is continuity from D3/C2/C4 (where you have the measured and correct plus 22 volts) to the regulator input (pin 1). If you measure the voltage on the actual regulator pin, be careful not to short it to the adjacent pins. Also check that pin 3 of this regulator goes to D1 anode (non stripy end).
There is not much else it can be really other than a break in continuity. Check carefully and report back with your findings
There is not much else it can be really other than a break in continuity. Check carefully and report back with your findings