Hi Marcel. I hope all is well.
Today I'm expecting a delivery containing the parts I need to complete the population of the main DAC board and I anticipate finishing the assembly this weekend.
I'm now starting to think about testing/power-up etc. Any thoughts on a strategy? Unfortunately I don't have access to an oscilloscope at the moment; I don't own one and I will be unable to access the one I usually utilise (along with its owner who 'supervises' me) because of the Covid situation.
Today I'm expecting a delivery containing the parts I need to complete the population of the main DAC board and I anticipate finishing the assembly this weekend.
I'm now starting to think about testing/power-up etc. Any thoughts on a strategy? Unfortunately I don't have access to an oscilloscope at the moment; I don't own one and I will be unable to access the one I usually utilise (along with its owner who 'supervises' me) because of the Covid situation.
Thanks Marcel - some more homework!
The parts were delivered today so I'm ready to wield the soldering iron at the weekend.
One other thing I've changed on the project is to go with balanced output via XLR connectors as it gives me the option of adopting it more generally in the future. In the immediate term I'll use some XLR to RCA cables to hook up to my amps.
The parts were delivered today so I'm ready to wield the soldering iron at the weekend.
One other thing I've changed on the project is to go with balanced output via XLR connectors as it gives me the option of adopting it more generally in the future. In the immediate term I'll use some XLR to RCA cables to hook up to my amps.
A productive afternoon 
The main PCB is now fully populated, I've installed the XLR sockets and connected them up to the filter boards and I've almost finished hooking up the IEC mains connector and on/off switch.
Regarding grounding - the chassis obviously has a safety ground connection to the IEC connector - I've installed one of my usual Broskie ground lift boards (capacitor/rectifier/resistor in parallel) to connect the DAC ground to the safety ground - just need to sort out the best place to connect the main board to it.
Getting very close now so hoping I can soon take delivery of the NOS valves I'm being loaned.
The main PCB is now fully populated, I've installed the XLR sockets and connected them up to the filter boards and I've almost finished hooking up the IEC mains connector and on/off switch.
Regarding grounding - the chassis obviously has a safety ground connection to the IEC connector - I've installed one of my usual Broskie ground lift boards (capacitor/rectifier/resistor in parallel) to connect the DAC ground to the safety ground - just need to sort out the best place to connect the main board to it.
Getting very close now so hoping I can soon take delivery of the NOS valves I'm being loaned.
They're big 400V Arcotronics caps - I soldered them underneath the board otherwise I won't be able to get the top of the chassis on.
Stand By For Action!
Everything is now hooked up and ready for testing. All being well I will receive the six valves this week so next weekend...
In the meantime, I've done some very limited testing;
No magic smoke!
Incidentally, I grounded the main board (to the chassis safety ground, via a Broskie ground lift arrangement) with a connection to the + side of C126, (C126 is where I've made the regulated B+ supply connection).
Nothing I can do until I get the valves now so a time for patience.
Everything is now hooked up and ready for testing. All being well I will receive the six valves this week so next weekend...
In the meantime, I've done some very limited testing;
- I inserted a single valve and powered up the filament supply - it glows and I measure 6.24VDC.
- I've powered up the 5V power supply and DAC circuits - I measure 4.97VDC
- With just the filaments and 5VC circuits energised I connected the DAC to the network - it was 'seen' by HQ Player and I was able to 'play' a track (@DSD128) without any apparent glitches.
No magic smoke!
Incidentally, I grounded the main board (to the chassis safety ground, via a Broskie ground lift arrangement) with a connection to the + side of C126, (C126 is where I've made the regulated B+ supply connection).
Nothing I can do until I get the valves now so a time for patience.
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Well, you could check if it produces orange light. If it does and relay U26 does what it is supposed to do, you should get 85 V +/- 2 V across C118 or across R85. It's an 85 V reference with respect to the -300 V line, so with respect to ground you get roughly -300 V and -215 V. The start time of the 85A2 can be anything from a few dozen microseconds to many seconds, depending on the brand of 85A2 and to some extent on the amount of ambient light.
Well, first things first - it works and I've listened to some music; more precisely, it worked and I listened to some music for a few minutes!
So, the story so far;
Last evening I had a big scare. Fairly late on the temptation to plug the valves in got the better of me so I reinstalled the main board and powered up the 5V and filament supplies all OK. I was just about to flick the switch of the B+ when luckily I had this really scared feeling - turns out I had connected the B+ supply the wrong way round. Don't mess when you're tired!
Anyway, after a good nights sleep I resumed this morning.
Checked and double checked! Powered up the filaments and 5V sections and verified that HQ Player was seeing the device and I could 'play' tracks (DSD128) - all OK.
Powered down and hooked up the headphone amp, set volume to mute and started powering up again and got music tracks 'playing'. Switched on B+, quickly checked the voltages and all seemed OK. Put on the headphones and gradually turned up the volume - music!
I listened for maybe 3 minutes (about a track's length) and then started to hear some noise, which gradually increased. Now no music just a loud buzzing noise.
I've powered everything off for now to have a think and get advice. I'm assuming a component has failed at this point, whether that has led to a domino affect we'll have to see.
So, some trouble-shooting to do. My first thought is to leave it for an hour and see if it works when everything is cool, though I have a low expectation in that respect, and, assuming that is a negative, then to start comparing voltage measurements against the schematic (with the valves out to start with).
Any thoughts Marcel?
So, the story so far;
Last evening I had a big scare. Fairly late on the temptation to plug the valves in got the better of me so I reinstalled the main board and powered up the 5V and filament supplies all OK. I was just about to flick the switch of the B+ when luckily I had this really scared feeling - turns out I had connected the B+ supply the wrong way round. Don't mess when you're tired!
Anyway, after a good nights sleep I resumed this morning.
Checked and double checked! Powered up the filaments and 5V sections and verified that HQ Player was seeing the device and I could 'play' tracks (DSD128) - all OK.
Powered down and hooked up the headphone amp, set volume to mute and started powering up again and got music tracks 'playing'. Switched on B+, quickly checked the voltages and all seemed OK. Put on the headphones and gradually turned up the volume - music!
I listened for maybe 3 minutes (about a track's length) and then started to hear some noise, which gradually increased. Now no music just a loud buzzing noise.
I've powered everything off for now to have a think and get advice. I'm assuming a component has failed at this point, whether that has led to a domino affect we'll have to see.
So, some trouble-shooting to do. My first thought is to leave it for an hour and see if it works when everything is cool, though I have a low expectation in that respect, and, assuming that is a negative, then to start comparing voltage measurements against the schematic (with the valves out to start with).
Any thoughts Marcel?
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Just thinking about this a bit more, as the noise started quietly and then gradually increased is it a reasonable assumption to think that it's likely to be a passive component overheating, or just plain faulty, as I imagine active components, like the small devices in the clocking etc. would fail suddenly?
Anyway, getting ahead of myself - need measurements first.
Anyway, getting ahead of myself - need measurements first.