Prune said:
Mr. Rollins' original A-X is water-cooled, if I recall correctly.
I used fans in mine. It's great. I used a 12V 120mm fan, and a PWM fan controller. The controller keeps the sink at just the right temperature, and the fan is never audible. Somewhere on these forums I posted the schematic for the fan controller.
The obvious advantage of fan cooling is you amp can be much smaller. Mine isn't much larger than The Art of Electronics, to give you some idea. There's no good rules about fan cooling, but the efficiency will obviously be higher than passive airflow heatsinks, and you can also use heatsinks that would be totally inappropriate for passive cooling (thin, closely spaced fins, for example).
I sometimes use the simulator tools at r-theta.com
pulse sorce to aleph-X or my BZLS ??? 
Hi, if I wanted to build 100 W (two channels) output Aleph-X, how many of these heatsinks would I need:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=31489&item=3865817801&rd=1
?? (I don't know how to work out the maths)
What if I use a (slow) fan?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=31489&item=3865817801&rd=1
?? (I don't know how to work out the maths)
What if I use a (slow) fan?
Heatsinks
Hi I am building a 100 aleph..........with the calcs I did a while back
and not knowing full theremal spec......I recon you would need to double your heatsinks........for the min passive setup......this would still run hot..........mine was working out at approx 45degC
you should'nt really go much above that ........ as touching for over 3 seconds could result in a burn...........
Fan cooling makes a big difference the tunnel could also protect from inadvertent scalding........so temps could go higher............
I recon your sinks may just cope with fan assistance................. however fan failure and the extra complexity (dont forget you would need a fan overun on switch off) + noise are issues you would have to live with/overcome. I think the quietest fans out now run at approx 20dB............
(I would go for extra heatsinks + copper busbars to fix fets on.
Good luck
Hi I am building a 100 aleph..........with the calcs I did a while back
and not knowing full theremal spec......I recon you would need to double your heatsinks........for the min passive setup......this would still run hot..........mine was working out at approx 45degC
you should'nt really go much above that ........ as touching for over 3 seconds could result in a burn...........
Fan cooling makes a big difference the tunnel could also protect from inadvertent scalding........so temps could go higher............
I recon your sinks may just cope with fan assistance................. however fan failure and the extra complexity (dont forget you would need a fan overun on switch off) + noise are issues you would have to live with/overcome. I think the quietest fans out now run at approx 20dB............
(I would go for extra heatsinks + copper busbars to fix fets on.
Good luck
You mean two of the eBay item I referred to (one per 100W channel)? And if I use a fan, I can use just one of these (half for each channel)?
Also, about grounding: do the heatsinks need to be insulated from the rest of the case? If not, the extra surface would provide more cooling. I plan to use a rackmount chassis with the heatsink fins facing inwards, fan blowing through tunnel configuration, and connected to the case so the whole thing is like a heatsink.
What VA rating transformers are you using, D3? Also, other than size, I'm still not clear why I should use a toroidal over EI core transformer, especially when the EI gives better mains noise isolation. And, how many output devices are you using?
Also, about grounding: do the heatsinks need to be insulated from the rest of the case? If not, the extra surface would provide more cooling. I plan to use a rackmount chassis with the heatsink fins facing inwards, fan blowing through tunnel configuration, and connected to the case so the whole thing is like a heatsink.
What VA rating transformers are you using, D3? Also, other than size, I'm still not clear why I should use a toroidal over EI core transformer, especially when the EI gives better mains noise isolation. And, how many output devices are you using?
Heatsinks
I was refering to you proposing to use 1x 12x5x1 heatsink per channel ie 2 in total.
The above will be very hot....passively cooled you will need to double surface area..........therefore I would say a min of 4 sinks required for a 100w stereo amp.....
Re fans I would use at least 2 120mm fans running @ low speed
...you would need to create some sort of tunnel.....and use the two fans to blow through.........
I am using 1000va transformers, from air link...........however if you can afford it go for fully encapsulated quality 'piltron' with a min of 1000va. (I think Mr Pass uses something like 2000va)
I am using eight devices per channel.........these will be fixed to copper bus bars directly............the bus bars will be isolated from sink by 'silpad' conductive insulator.
Do not under estimate the heat from these amps!!!
I was refering to you proposing to use 1x 12x5x1 heatsink per channel ie 2 in total.
The above will be very hot....passively cooled you will need to double surface area..........therefore I would say a min of 4 sinks required for a 100w stereo amp.....
Re fans I would use at least 2 120mm fans running @ low speed
...you would need to create some sort of tunnel.....and use the two fans to blow through.........
I am using 1000va transformers, from air link...........however if you can afford it go for fully encapsulated quality 'piltron' with a min of 1000va. (I think Mr Pass uses something like 2000va)
I am using eight devices per channel.........these will be fixed to copper bus bars directly............the bus bars will be isolated from sink by 'silpad' conductive insulator.
Do not under estimate the heat from these amps!!!
1000 VA per 100 W channel? Why so large? I plan on using a regulated supply, so wouldn't say 700 VA be enough? BTW, can you recommend a source for these busbars? And which of the two output device options discussed here are better for a 100 W amp?
Note: I don't have M$ Office, so I can't use the spreadsheet (the current version of OpenOffice does not import it properly).
Note: I don't have M$ Office, so I can't use the spreadsheet (the current version of OpenOffice does not import it properly).
Tranny
You misunderstand 1000va in total....for 2 channels.........in theory you can get away with 750va just..........best to have some headroom......
For Busbars in UK contact:-
Paul Bird
Metelec Ltd
Copper & aluminium conductor suppliers
Vulcan Industrial Estate
Leamore La
Walsall
WS2 7BZ
United Kingdom
Walsall companies
Telephone, fax and web
Tel: (01922) 712665
Fax: (01922) 710919
(paulbird@metelec.co.uk)
http://www.metelec.co.uk
My busbars are 50x12.5x250mm cost approx £10 each + vat + postage....these are good they lower your fet junction temprature by nearly 40% making amp more reliable.
You misunderstand 1000va in total....for 2 channels.........in theory you can get away with 750va just..........best to have some headroom......
For Busbars in UK contact:-
Paul Bird
Metelec Ltd
Copper & aluminium conductor suppliers
Vulcan Industrial Estate
Leamore La
Walsall
WS2 7BZ
United Kingdom
Walsall companies
Telephone, fax and web
Tel: (01922) 712665
Fax: (01922) 710919
(paulbird@metelec.co.uk)
http://www.metelec.co.uk
My busbars are 50x12.5x250mm cost approx £10 each + vat + postage....these are good they lower your fet junction temprature by nearly 40% making amp more reliable.
Prune said:
Good Luck!
You are going to need it.A regulated supply for a 100w class a amp is a whole project unto itself plus you will have a lot of extra heat to dissipate.
Maybe you should just buy the whole stock this guy has and start from there!
Kidding aside I would go the traditional route and use two or four of those heatsinks per channel.I think the air tunnel variation is going to be a pain in the behind although if you do a search I remember a very nice project here where somebody made a beautiful stereo aleph 5 that way but not with your type of heatsink.
I think barrredboss cuts heatsinks to requested length and I also suspect he may have 10inch wide heatsinks.I would say that based on my calculations you will need a minimum of four 10 inch wide x 12inch long heatsinks per channel to be safe.If you want to save space you could make a chassis with these heatsinks all around like the original Pass Aleph series.
Edit: By the way I don't know what speakers you have but I find IMHO that in most cases people overrate their needs believing that they need lots and lots of watts.You will be surprised at what a small difference there is between a 50w and a 100w amp assuming real world speakers and average listening room.However there is a huge difference in cost and outlay between those two amps when we are talking about class a operation.So it pays in this case to be less "enthusiastic" about your wattage needs.
PSU
Look life's complicated enough as it is ...........just go for a simple PSU with a good stout level of capacitance..........it's a bit like an American V8 engine verses Small high reving multivalve europian engine.
U should get ripple really low.....with some good caps. I'm using
6x63,000 micro farad caps ............
Look life's complicated enough as it is ...........just go for a simple PSU with a good stout level of capacitance..........it's a bit like an American V8 engine verses Small high reving multivalve europian engine.
U should get ripple really low.....with some good caps. I'm using
6x63,000 micro farad caps ............
