So you guys that have your transformers, any chance we could get a pic to see how they fit on the pcb, since we've only ever gone off measurements? I mean 99% confidence that they are fine and hopefully won't be too long till a box arrives at qusp's joint with mine in it but I've been pretty keen to see them on a pcb for a while now 
perfect, thanks for the pics neb001: just as planned and visualised, it actually fits better than the one in the BOM, looks like..well..like it was made for it lol but I was given 2 can sizes to chose from that were close and I got out adobe illustrator and couldnt believe our luck. the other choice was a black can which is cooler, but it would have hung over the edges ~5mm and was a touch risky wrt the caps. it would have allowed us to go up to 30-35va, but not enough payoff for the risk, as 25va is just right already.
feel free to connect the primaries into the holes on the PCB, but we (hochopeper and I) decided that we would just connect them directly to IEC/relay rather than cutting traces and theres no reason you guys cant do that as well. the secondaries are just as planned too, hovering just near the holes for the stock tx secondaries while still being long enough when trimmed to be manipulated into place. all in all pretty happy with that, love it when a plan comes together..well..theres one aspect of the plan that persistently refuses to come together......
feel free to connect the primaries into the holes on the PCB, but we (hochopeper and I) decided that we would just connect them directly to IEC/relay rather than cutting traces and theres no reason you guys cant do that as well. the secondaries are just as planned too, hovering just near the holes for the stock tx secondaries while still being long enough when trimmed to be manipulated into place. all in all pretty happy with that, love it when a plan comes together..well..theres one aspect of the plan that persistently refuses to come together......
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cool, glad they are all arriving safely. the replacement resistors arrived too and ive been just plodding through snipping the strips any time I get a spare moment. i'll make an effort to get the majority done sans keratherm by the end of the week as hochopeper and I will get together on the anzac day holiday.
without knowing the heatsink situation its hard to go ahead and cost/buy packing materials, but i'll just have to bite the bullet this weekend I think so we can all get on with our builds and then maybe send the heatsinks separately as one bulk shipment to the US, considering the amp will run fine without a sink for most people that should work and people can get going and just bolt it on when ready.
without knowing the heatsink situation its hard to go ahead and cost/buy packing materials, but i'll just have to bite the bullet this weekend I think so we can all get on with our builds and then maybe send the heatsinks separately as one bulk shipment to the US, considering the amp will run fine without a sink for most people that should work and people can get going and just bolt it on when ready.
Might just be the morning grogginess but I'm not understanding what you meant by "rather than cutting traces." Why would you need to cut a trace?
although now we have 230v single primary we can just use 2 of the holes if we wanted, I like the idea of connecting direct better anyway and will just use a high current snap connector.
sorry Ben, I should have been more specific,m I should have known being a member of the greater Americanus genus like opc you wouldnt think outside the continent haha (joking). see he forgot to provide for jumpers to set series or parallel connection for the primaries and without getting a custom TX we would have had to cut traces if we wanted to connect to the board
sorry Ben, I should have been more specific,m I should have known being a member of the greater Americanus genus like opc you wouldnt think outside the continent haha (joking). see he forgot to provide for jumpers to set series or parallel connection for the primaries and without getting a custom TX we would have had to cut traces if we wanted to connect to the board
Correct... the PCB with the XFMR on the BOM would have required trace cutting to work with 230V.
With the custom unit, there should be no need to cut traces if you really want to wire it to the PCB, but I see absolutely no reason to do this if you already have nice long flying leads directly off the transformer. Just solder those to your favorite IEC plug and you're off to the races.
Also, don't forget a fuse!
Cheers,
Owen
With the custom unit, there should be no need to cut traces if you really want to wire it to the PCB, but I see absolutely no reason to do this if you already have nice long flying leads directly off the transformer. Just solder those to your favorite IEC plug and you're off to the races.
Also, don't forget a fuse!
Cheers,
Owen
haha indeed, but I thought these chips endured perpetual short circuit?
yeah well we'll be switching this remotely using relays via the MCU which will switch, sequence and monitor all 4 balanced channels of dac and amp using a Beaglebone, so for sure there'll be fuse/s somewhere
its all good Owen, you just threw this thing together onto a spare space on the panel didnt you? little did you know it would sell out in minutes across the globe and spawn the inaugural professional product. have you got a name for the company yet?
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I know you edited the post away, but more importantly, do you guys actually call them crocodile clips down there?
If so, that's the single funniest thing I've heard all night
They're alligator clips!
Cheers,
Owen
I'd call them alligator clips normally but qusp isn't the first I've heard call them a crocodile clip.
I thought 'redickulous' was pretty funny actually too. qusp is on fire today!
ok guys in the TX GB, just be aware when testing the boards of the voltage after the bridge. if you do as I do, you'll build up the PSU section first, test and set voltage before moving onto stuffing the amp section. I did this for one channel last night and we were waaay into off peak power period, so the grid wasnt loaded either. anyway I got just over 28vdc after the bridge, which is inline with the no load spec on the transformer spec sheet of 20.7vac. thats fine, but just be aware that the main electrolytic caps are only 25v. once there is even a small load on the transformer it drops down to ~24-25 and as opc said they are electrolytic caps, they dont just fall over instantly as soon as the voltage rating is breached like polymer caps.
when Richard specs a tx at 16v under full load, thats what he means, which dos mean it will be slightly higher when idle. I confirmed with Owen that everything on the board will cope with this, the lme49990 will run at its stated max of +/-18vdc indefinitely and just get a little warm and the buffer will handle up to +/-20vdc so we're safe at 18. if you are really concerned you could go down to the 3900uf main caps, but theres really no need. even the bom transformer will be over the 25vdc when totally unloaded.
so either be reasonably quick when presetting/testing the PSU section before moving on (I really suggest you do this rather than just stuffing the whole board) just load the output of the regs with a suitable resistor or LED, like a pair of 10W 47R resistors in parallel for each rail, for a 23.5R load or 18v/23.5 = 766ma which is right on the transformers rating. you could go easy on it by using 1 x 20W 33R (545ma @ 18v 9.81W each reg) resistor for each rail, but may as well test the tx and psu are capable of their max.
when Richard specs a tx at 16v under full load, thats what he means, which dos mean it will be slightly higher when idle. I confirmed with Owen that everything on the board will cope with this, the lme49990 will run at its stated max of +/-18vdc indefinitely and just get a little warm and the buffer will handle up to +/-20vdc so we're safe at 18. if you are really concerned you could go down to the 3900uf main caps, but theres really no need. even the bom transformer will be over the 25vdc when totally unloaded.
so either be reasonably quick when presetting/testing the PSU section before moving on (I really suggest you do this rather than just stuffing the whole board) just load the output of the regs with a suitable resistor or LED, like a pair of 10W 47R resistors in parallel for each rail, for a 23.5R load or 18v/23.5 = 766ma which is right on the transformers rating. you could go easy on it by using 1 x 20W 33R (545ma @ 18v 9.81W each reg) resistor for each rail, but may as well test the tx and psu are capable of their max.
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