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Hooked it all up and we get a fault light on the 3e board.
So I had to RTFM to work out what was wrong. The website gave me the impression the board took single ended and balanced inputs. It only does the former as per the pic below.
The board itself just says short IN- to GND for SE mode, which I did for both channels. Grok agreed, but it's way more complex than that and involves breaking the warranty.
You can buy SE to balanced converter boards but they need their own PS and that's just not on.
So I'll find another TPA3255 amp that takes an SE input, which is basically the AD9833's PGA chip output format.
Grok recommended this board, adamant it was a really good solution. It isn't in this case.
Grok is wrong a lot of the time. I even gave Grok a copy of the board's PDF manual and it still didn't assimilate it properly, claiming it could read it but it completely missed section 5.5.
I'm actually not that annoyed. Just enjoying sorting it out and pretending I can solder. Which I suck at.https://uploads.tapatalk-cdn.com/202...5d57a54b68.jpg
https://uploads.tapatalk-cdn.com/202...32096f69c6.jpg
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I hardly understand a thing in this thread, Justin, but it is strangely addictive and I admire your dedication to the cause! Well done, that man!
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I think it's basically a mess, Alex.
When I get something going I'll probably just put how to make one in a separate thread.
Fundamentally I am convinced it really isn't that difficult to make given instructions and will probably work with other AC motors I would imagine.
It's just an engineering problem and as usual what takes all the time is finding the simple solution.
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That 3e audio module can be bridged to give about 480 Watts. So I will buy another and make a couple of monoblocks rather than sell it. Maybe. My Luxman pre has balanced outputs.
Meanwhile, I have ordered a £20 TPA3255 board from Amazon but it won't be here for a couple of weeks.
https://amzn.eu/d/76lT9uk
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1 Attachment(s)
The TPA3255 board turned up. The good thing is the output is the 22V we are looking for on both channels. And it doesn't get hot or even warm in this test config.
Both are in-phase despite the 22uF 50V bi-polar cap across the +ve output terminals of the amp's left and right channels.
Grok reckons you need to connect the motor to get the phase shift to appear. Tried that and nothing. Unsure why, but it could be that the on/off switch on the motor housing has gone, or the motor windings are bust.
Will do some motor winding resistance / switch testing. I long suspected the switch was knackered along with the old power supply. I used to spend ages just pressing it on/off until it would eventually start. Eventually obviously it ceased to work altogther.
I should have tested the motor windings before starting this escapade really but I'd be very surprised if it is busted.
Each channels as different Y scalings to make them not overlap in the scope trace below.
Attachment 31560
https://uploads.tapatalk-cdn.com/202...d45480402d.jpg
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Grok and ChatGPT reckon the low output impedance of the amp stops the phase shift from happening.
The switch and motor are OK.
Getting close just needs a bit more playing around.
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Must get back on the case here. I think I destroyed an AD9833 board by mistake, which was annoying...
The problem is tricker to get to actually work in practice than concept says it should be IMHO.
Plus dodgy cheap components that arrive with zero instructions in jiffy bags with literally no decent protection makes it hard to have any faith they are actually fault free.
Even the scope and software behaves irrationally and requires resetting from time to time.
That said, I really haven't spent any more than a couple of hours on it since my last post.
Sent from my CPH2653 using Tapatalk
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Got back on the case today. Not looked at it much since the last post, though I did figure out that I had destroyed an AD9833 so ordered another.
Got it going with about 5 hours of solid effort listening to Circles Around the Sun - Interludes for the Dead and other material by them. Just the ticket for a cool, steady workflow in a chilled out mood.
Still needs finalising but the motor spins with good torque. Result. Not played a record yet while away from that.
Needs a change in cap value for phase shift optimisation. It's around 100 degrees at the moment. TBH not sure what the optimal value is maybe somewhere around 60 to 90 degs. Could do with the Pabst motor spec haven't really looked for it yet.
Will say more in due course. Just pleased the basics are sorted:)
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OK bit of tweaking and I managed bang on 90 degree phase shift (the XY round circle shows that). That phase shift gives optimal torque for the Pabst (confirmed via various searches).
Oven thermometer reckons it's running at about 50 degC after half an hour of running the motor.
This is as good as it's going to get, so just need to make what you see nice and tidy.
It's actually a simple build once you know what to do, which is the tough part.
Will post construction details and software at some stage.
I am convinced this is a good if not a very good solution.
https://uploads.tapatalk-cdn.com/202...1af16a5691.jpghttps://uploads.tapatalk-cdn.com/202...4a6ae0f47a.jpghttps://uploads.tapatalk-cdn.com/202...a56d729fb8.jpg
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Looks alright I reckon.
I should probably have shortened and heat shrinked the mini-XLR connections to be tidy but TBH I know those connections are very solid and will be fine for decades.
A lot of manufacturers use 24VAC 50Hz dual phase motors. This design should work with them, but may require some tweaking.
Examples: Dual, Rega, Avid, Clearaudio, Basis Audio, Origin Live, Project etc etc.
https://uploads.tapatalk-cdn.com/202...b66ef0d1fb.jpg
