yep thats about the size of it
well i cant really get a quote from him without interest, he has to work up a custom quote for a custom build, it will have non standard pinout, non-standard core for the size etc, it'll take time and i dont want to ask him without knowing there is interest
there was a couple
i dont think an offboard transformer should be considered as an option for the custom case, it would compromise the design too much.
quite a lot, i dont think we should even bother about the topside of the board, but rather get a custom diecut for the bottom, thats where the heat is, not the epoxy bodies on the top; if the bottom is properly taken care of there will be no need for anything on top, but doing the top properly would be a pita by itself and IMO not worth the trouble
but you are right, we really do need to hear from HYPERTUNE, who has been quite notably silent, i'll shoot Mark an email a bit later for an update
Hi Guys,
I'd like to apologize to my 230V friends, I have no idea what I was thinking when I wired it up like that. I was in such a hurry to get it finished, that I think I looked at it and in my head was thinking "if you need 230V you can just buy a 230V transformer" which is obviously non-sense.
A pair of jumpers on the board would have alleviated this issue...
So here's what I propose:
1. Buy the dual 9V output and just put 240V across the primary in parallel. This would need to be thoroughly tested by someone is AUS, as there's a chance it will saturate the core of the transformer. The actual voltage isolation isn't an issue as the primary is already adequately isolated for 240V, and the change in voltage on the secondary is negligible when it comes to insulation capacity. This would give you dual 18V outputs, so you might need to change over to 35V caps on the primary, but the combination of heavier gauge copper on the secondary and more voltage would mean you'd probably get better voltage regulation and more power output.
Digi-Key - TE2257-ND (Manufacturer - L01-6361)
2. Cut the end of the board off just past the two secondary inputs on the board, and mount a transformer to the chassis base where the old board used to be. This would allow the use of a larger transformer (50VA) in the same space the board mounted one used to occupy. I use a shear to cur boards, and it leaves a perfect edge if you're careful.
3. Buy a small 25 VA non-potted toroid and just mount it through the bolt hole on the board:
Digi-Key - 237-1326-ND (Manufacturer - VPT30-830)
The above will work, but if you can find one that is taller and not as large a diameter, then that would be better.
4. Mount a much larger toroid off-board and just wire it in the way you need it.
5. Have a custom toroid made that is potted and has the correct pinout. I'm not sure how reasonable this is with the smaller numbers here, but if you can find someone to do it, then go for it!
If someone is willing to test #1 then I'll pay for a toroid, but it will have to be proper test that looks at the current waveform on the primary. We should be able to see if it's saturating the core based on the profile.
For the heatsinks, I would probably suggest sticking to the top of the board, and not the bottom. The thermal resistance through the PCB is probably worse than it is through the packages, but the larger surface area probably makes it better overall. The real target needs to be the top copper plane on either side of the buffers. That means the heatsink proposed by HYPERTUNE really is the best proposal, and will be more than enough to keep the heat in check.
I would still strongly suggest a good TIM and would be interested in a few strips of the keratherm. It would be best to apply a strip across each row of devices, and another strip across each copper plane on the edge of the board. Use thin material that has high compliance for best results.
If you really want to go all out, perhaps HYPERTUNE could also machine an aluminum bottom plate/sink with threaded holes so that the heatsink could be bolted down onto it, sandwiching the devices between two hunks of aluminum. This would definitely be the best thermally, but requires more machine work and more TIM.
Cheers,
Owen
I'd like to apologize to my 230V friends, I have no idea what I was thinking when I wired it up like that. I was in such a hurry to get it finished, that I think I looked at it and in my head was thinking "if you need 230V you can just buy a 230V transformer" which is obviously non-sense.
A pair of jumpers on the board would have alleviated this issue...
So here's what I propose:
1. Buy the dual 9V output and just put 240V across the primary in parallel. This would need to be thoroughly tested by someone is AUS, as there's a chance it will saturate the core of the transformer. The actual voltage isolation isn't an issue as the primary is already adequately isolated for 240V, and the change in voltage on the secondary is negligible when it comes to insulation capacity. This would give you dual 18V outputs, so you might need to change over to 35V caps on the primary, but the combination of heavier gauge copper on the secondary and more voltage would mean you'd probably get better voltage regulation and more power output.
Digi-Key - TE2257-ND (Manufacturer - L01-6361)
2. Cut the end of the board off just past the two secondary inputs on the board, and mount a transformer to the chassis base where the old board used to be. This would allow the use of a larger transformer (50VA) in the same space the board mounted one used to occupy. I use a shear to cur boards, and it leaves a perfect edge if you're careful.
3. Buy a small 25 VA non-potted toroid and just mount it through the bolt hole on the board:
Digi-Key - 237-1326-ND (Manufacturer - VPT30-830)
The above will work, but if you can find one that is taller and not as large a diameter, then that would be better.
4. Mount a much larger toroid off-board and just wire it in the way you need it.
5. Have a custom toroid made that is potted and has the correct pinout. I'm not sure how reasonable this is with the smaller numbers here, but if you can find someone to do it, then go for it!
If someone is willing to test #1 then I'll pay for a toroid, but it will have to be proper test that looks at the current waveform on the primary. We should be able to see if it's saturating the core based on the profile.
For the heatsinks, I would probably suggest sticking to the top of the board, and not the bottom. The thermal resistance through the PCB is probably worse than it is through the packages, but the larger surface area probably makes it better overall. The real target needs to be the top copper plane on either side of the buffers. That means the heatsink proposed by HYPERTUNE really is the best proposal, and will be more than enough to keep the heat in check.
I would still strongly suggest a good TIM and would be interested in a few strips of the keratherm. It would be best to apply a strip across each row of devices, and another strip across each copper plane on the edge of the board. Use thin material that has high compliance for best results.
If you really want to go all out, perhaps HYPERTUNE could also machine an aluminum bottom plate/sink with threaded holes so that the heatsink could be bolted down onto it, sandwiching the devices between two hunks of aluminum. This would definitely be the best thermally, but requires more machine work and more TIM.
Cheers,
Owen
ahh of course, i was 'thinking' the heat was being sunk to the ground pour, but the tabs of the buffer are live which is the top and then the middle ground and the bottom neg, so of course the bottom will have more thermal impedance, we just need to try and interface with the top copper as well as just the epoxy parts as Mark and you have suggested. i was never suggesting not using Mark's sink, it would be silly to turn such a great offer down, i was just still thinking out loud since we dont have any final design from him yet that it would be better to sink to the bottom and turn the entire unit upside-down, so the fins are at the top; this of course is a fools errand in light of your assertion
Hey Mate, look dont worry i know this was a last minute thing adding it to the plates for the board-house on a whim without an announcement and i'm sure you didnt expect it to continue the theme of selling out in 24hrs.
So Owen: of your options, due to myself and i'm not sure anyone else on this side of the pond having the gear you mention to test core saturation, although i suppose it could be spiced i would think it a pretty complex model.
due to this fact, this actually makes me lean towards the custom trannie or regrettably offboard, but i really want to keep the self contained goodness of the design. Richard will do a small order no worries, he specializes in one off custom orders so a small group will be no problem at all. He over-sizes the cores, but he also models and thoroughly tests his products and supplies a certificate of the pot testing, insulation testing, load and no load testing, duty cycle, efficiency etc all on an individual basis, very thorough and i have no doubt that he will be able to tell me if this is viable without passing step one.
so i'll contact him tomorrow and i guess i'll get in contact with HYPERTUNE to see where hes at and discuss what might be the best way forward WRT to TIM from Keratherm; then i'll send off an enquiery to them as well. so you are interested in enough material for all 4->6 of your amps?
Hey Mate, look dont worry i know this was a last minute thing adding it to the plates for the board-house on a whim without an announcement and i'm sure you didnt expect it to continue the theme of selling out in 24hrs.
So Owen: of your options, due to myself and i'm not sure anyone else on this side of the pond having the gear you mention to test core saturation, although i suppose it could be spiced i would think it a pretty complex model.
due to this fact, this actually makes me lean towards the custom trannie or regrettably offboard, but i really want to keep the self contained goodness of the design. Richard will do a small order no worries, he specializes in one off custom orders so a small group will be no problem at all. He over-sizes the cores, but he also models and thoroughly tests his products and supplies a certificate of the pot testing, insulation testing, load and no load testing, duty cycle, efficiency etc all on an individual basis, very thorough and i have no doubt that he will be able to tell me if this is viable without passing step one.
so i'll contact him tomorrow and i guess i'll get in contact with HYPERTUNE to see where hes at and discuss what might be the best way forward WRT to TIM from Keratherm; then i'll send off an enquiery to them as well. so you are interested in enough material for all 4->6 of your amps?
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but i ask again, who might be interested in custom trannies from sumR? pricing is hard to tell, but quite reasonable compared to some ive seen. for a fully potted 50VA 240vac-> 2 x 25vac with oversized core in a can with solid core leadouts (i'm silly like that) this usually goes for ~40 now given these will be slightly smaller and a smaller core i would expect them to be slightly less or maybe the same as that due to the pernickety order as one offs, this is about the same, or like 5 dollars more than the ones at digikey, so if we get a group of 30+ of 2 different types the amount should be less, plus he likes the exposure =)
i cant say with certainty, but i just want to get some expressions of interest and it seems noone is coming forward so maybe with this info they will, you guys arent really giving me much to work with at all with any of the orders to be honest.
I rate his work higher than or equal to plitron for less money
i cant say with certainty, but i just want to get some expressions of interest and it seems noone is coming forward so maybe with this info they will, you guys arent really giving me much to work with at all with any of the orders to be honest.
I rate his work higher than or equal to plitron for less money
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I agree that Richard does very nice work. I have used his transformers in several projects and never had a problem. And his pricing is reasonable as well, especially the shipping (to the States anyway, no idea about Aus). Anyway I am definitely interested in the trafo, 115/120 VAC though. Are you specifiying dual primaries so it will work everywhere or just going for the 240 volt version?
Thanks mate, yeah i knew you were interested, but it seems most of the GB, even the about 50% of it that posted here when i opened the thread have vanished for the last week since it was opened and leading up to the point where the PCBs are arriving this concerns me, as i simply dont have the time or desire to carry on with it if theres nothing in it for me; might sound selfish, but i'm very time poor, particularly at the moment. if bugger all people are interested we would be better off just sorting ourselves out.
as for the TX, due to the problem discovered on the PCB with 220-240v operation, there will have to be either 2 models specified from Richard, along with finding out if Owens suggestion will actually work without saturating the core, get a fully custom unit with a non-standard pinout, or we all get the same order from him and those that need to put the primaries in series will have to hack the PCB
as for the TX, due to the problem discovered on the PCB with 220-240v operation, there will have to be either 2 models specified from Richard, along with finding out if Owens suggestion will actually work without saturating the core, get a fully custom unit with a non-standard pinout, or we all get the same order from him and those that need to put the primaries in series will have to hack the PCB
I'd be interested in a pair of the 230V primary transformer from SumR. I'm somewhere on the fence between custom transformer and opc's Option 3 stated above.
For me, Option 3 is more a fall back position if price of the custom transformer is going to compromise me being able to buy the rest of the gear for this build.
qusp, I think setting a min threshold for each module of the GB (active, passive, enclosure/heatsink, transformer) is very reasonable. If we don't meet minimum interest to achieve a reasonable discount it is up to the individual to sort out their own requirements.
The advantage of the modular GB idea is any one module can be dropped if it becomes no longer viable.
At the prices stated in this thread I can't understand why anyone with pcbs who seriously wants to build this amp wouldn't be wetting themselves with excitement over this GB. Unless perhaps everyone already has a stash of most of the components necessary. In which case personally I'd still be jumping on these prices if just to replenish stock of components used in this build.
For me, Option 3 is more a fall back position if price of the custom transformer is going to compromise me being able to buy the rest of the gear for this build.
qusp, I think setting a min threshold for each module of the GB (active, passive, enclosure/heatsink, transformer) is very reasonable. If we don't meet minimum interest to achieve a reasonable discount it is up to the individual to sort out their own requirements.
The advantage of the modular GB idea is any one module can be dropped if it becomes no longer viable.
At the prices stated in this thread I can't understand why anyone with pcbs who seriously wants to build this amp wouldn't be wetting themselves with excitement over this GB. Unless perhaps everyone already has a stash of most of the components necessary. In which case personally I'd still be jumping on these prices if just to replenish stock of components used in this build.
If you specify the primary side of the transformer to have wire leads rather than fully pcb mount you can hook up mains however you want.
Hi Guys,
I will probably end up with my LPUHP in a common enclosure with the "Wire Amp" modules. I'm still happy to machine billet enclosures for those that want them if a design were agreed upon.
I'm guessing it's best for now to just make the heatsinks as originally planned, with mods and additions as suggested by Owen. I should get my boards in the next couple of days and will finalize the heatsink design then.
qusp: I'll follow the leader (you) as far as the GB is concerned. Whatever you decide, I'm in.
I will probably end up with my LPUHP in a common enclosure with the "Wire Amp" modules. I'm still happy to machine billet enclosures for those that want them if a design were agreed upon.
I'm guessing it's best for now to just make the heatsinks as originally planned, with mods and additions as suggested by Owen. I should get my boards in the next couple of days and will finalize the heatsink design then.
qusp: I'll follow the leader (you) as far as the GB is concerned. Whatever you decide, I'm in.
ditto
well given it will be a separate order it doesnt nessecarily have to happen at exactly the same time. it will take a couple of weeks for Richard to produce the order anyway, particularl if he has to order in custom cores or mounting arrangements.
perhaps bcg27 could take delivery and send out to save on shipping; as canada post shipping is pretty pricey and a bit slow internationally, certainly from Richard i have found its the only thing that stops me using him for everything. that way bcg27 could test his before passing them on as well. given he also has a previous relationship with sumR this seems a good idea to me; if that is acceptable to bcg27 of course
yep i think thats the best way forward, the digikey order for passives and actives would happen concurrently, but they would be treated as separate GB's
indeed, i think thats the best way forward
me neither, its odd that so many have not shown their faces since the beginning and even at the beginning only just over half the pcbs have been matched with interest in parts. given the change of the landscape even the passives gb might need to be rethought and maybe just us aussies and NZ people band together, it might even slip down my list of priorities tbh now there is decisions to be made regarding the case
yeah i'll mention this to Richard, if i'd known i might have got opc to use his board shear and chop it off so i can just use the potted 50va sumR trannies i already have
ok i'll just count you in for the options and keep you in the loop regarding the transformer solution. in light of the above, heatsinking and enclosure overall needs a rethink from my end, installing in with my other amps is not an option and not even desirable as initially i'm just running 2 way so the power amp will be a fairly compact 4 channel balanced amp, with the view to 3 way plus sub, but thats a way off. whatever the enclosure is it will be small and since now it looks like I wont have to worry about what others want, it'll probably be a bit out there.
so i'll send through some queries for Richard at sumR about the TX and i might send a group reminder PM out to all of the members of the GB to see if we can get a better idea, i dont want to put together a small gb and then find people straggling into this thread surprised and disappointed that they missed out, but if the response is not overwhelming, without having to cater for everyone, i will probably go by a different schedule and space the orders out a bit.
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Should work for me if it comes out to be cheaper that way. When the design gets hammered out ask Richard for the weight and I can get a shipping estimate for US to Aus to see if it will save any money.
I did receive my boards.
I'm favoring a single transformer, shielded, off board for 2 amps. $17.50 + Shipping
Antek - AS-0515
http://www.antekinc.com/pdf/AS-0515.pdf
I'm favoring a single transformer, shielded, off board for 2 amps. $17.50 + Shipping
Antek - AS-0515
http://www.antekinc.com/pdf/AS-0515.pdf
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nope, i'm making little monoblocks, if not i would be doing something like that, but with a custom trannie from Richard
so you are getting the audio grade with the electrostatic shield and then powering 2 amps with it connected in parallel?
hmmm
ahh thats right, the shield is for capacitive coupling from primary to secondary. still if i was housing both these amps together i would at the very least give them dedicated secondaries. nice trannies for the money those though
so you are getting the audio grade with the electrostatic shield and then powering 2 amps with it connected in parallel?
hmmm
ahh thats right, the shield is for capacitive coupling from primary to secondary. still if i was housing both these amps together i would at the very least give them dedicated secondaries. nice trannies for the money those though
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Wouldn't you need 4 secondary windings for a single tx supplying 2 amps?
I'm still doggedly sticking to the miniature monoblock with qusp!
I'm still doggedly sticking to the miniature monoblock with qusp!
The transformer you linked only has dual secondaries though. Wouldn't you need one with quad secondaries if you want it to power two channels? Unless you plan to hook the secondaries up in parallel to the two boards.
I understand there may be benefits to "mono" configuration. I don't think the compromise is so great. They have suitable transformers for mono blocks...they don't meet the size constraints for on-board use.
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I would actually prefer both channels in a single enclosure. A bit bigger transformer, maybe 80-100 VA with quad 16-17 VAC secondaries would be my ideal transformer for this build I think.
a transformer with 4 secondaries does not need to be huge at all. not dual mono technically, but close enough. this is for a dual differential dac for all but the main analogue (IV) supplies
haha funny that we all jumped on him with the same thing in a matter of 3 minutes
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I want to express my interest in participating in the group buy.
I am in the US (Los Angeles).
Sorry I did not post earlier, I was kind of waiting for things to firm up, but now realize that makes it hard for you guys to plan. Funds are also kind of tight, but if I don't do the group buy, the boards may sit around for a long time.
Thanks to you guys for organizing this.
Randy
I am in the US (Los Angeles).
Sorry I did not post earlier, I was kind of waiting for things to firm up, but now realize that makes it hard for you guys to plan. Funds are also kind of tight, but if I don't do the group buy, the boards may sit around for a long time.
Thanks to you guys for organizing this.
Randy
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