Member
Joined 2002
Other than the 0R47 Source resistors and current sense resistors there's no need for anything bigger than 1/4W, which would buy you a lot of space. For reference, the DIY Chip Amplifier Kits, PCB's, Components and Information. mini Aleph board is 3.5" x ~2.25". It uses small format through hole resistors, but allows for use with several Aleph configurations.
+1 on omit heat sinks and fuses. If you are planning to use this as a universal Aleph front end, maybe leave heat sinks.
I'd use a single 100-220 uf cap to decouple each rail rather than the multiples. IMHO, multiple caps don't buy you much if anything.
Why just one SMD part? There was a SMD board that was supposed to be very good, but there's plenty of room on your board for a through hole voltage reference.
You might try to get Q3 and Q5 back to back or at least side by side to allow thermal coupling which helps maintain DC offset.
+1 on omit heat sinks and fuses. If you are planning to use this as a universal Aleph front end, maybe leave heat sinks.
I'd use a single 100-220 uf cap to decouple each rail rather than the multiples. IMHO, multiple caps don't buy you much if anything.
Why just one SMD part? There was a SMD board that was supposed to be very good, but there's plenty of room on your board for a through hole voltage reference.
You might try to get Q3 and Q5 back to back or at least side by side to allow thermal coupling which helps maintain DC offset.
Firstly thanks on the advice on thermal coupling, that one should have poped right out at me.
I'm aware the heatsinks, are not totaly required, its, just that there was space for them in this configuration, so I recconed they would add to the longevity of the amp.
The series of caps (100uf each was a compromise to get some decoupling in the few milimeter available to the side of the fuses, it was said the fuses are not required? Can I be dumb and ask why?
Lol, @ the SMD part, its juts what would be most easy for me to get. seeing that I have to dosh out for matched input pairs. It also went in easry in the layout and just sort of hung around, easy enough to fix.
About the high wattage resistors, the packages I chose for that output row, where some will get very hot, were not chosen as much for dissipation rating but for least amount of value shift due to high temperatures from adjacent hot components. Do you think it is a wasted effort?
The other reason for the larger board is individual power traces for all V+. V- and GND traces and an onboard signal and power groundstar.
I can't find that pic of their mini A, according to the description it is a main amplifier board and also has an output board....?
I'm aware the heatsinks, are not totaly required, its, just that there was space for them in this configuration, so I recconed they would add to the longevity of the amp.
The series of caps (100uf each was a compromise to get some decoupling in the few milimeter available to the side of the fuses, it was said the fuses are not required? Can I be dumb and ask why?
Lol, @ the SMD part, its juts what would be most easy for me to get. seeing that I have to dosh out for matched input pairs. It also went in easry in the layout and just sort of hung around, easy enough to fix.
About the high wattage resistors, the packages I chose for that output row, where some will get very hot, were not chosen as much for dissipation rating but for least amount of value shift due to high temperatures from adjacent hot components. Do you think it is a wasted effort?
The other reason for the larger board is individual power traces for all V+. V- and GND traces and an onboard signal and power groundstar.
I can't find that pic of their mini A, according to the description it is a main amplifier board and also has an output board....?
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As for rail fuses, it's sort of a redundant thing. If your mains fuse is properly sized, it will blow in the case of a major fault in the amp. If it makes you feel better, then by all means leave them.
Only the 0R47 may generate heat. The others in that row are gate stoppers (221R), protection circuit (no effect on sound when properly chosen values are used) and the bootstrap for the ACS. There may be some temperature related effects on stoppers and bootstrap, but you can lay out the board to keep them away from heat producing parts. The 0R47s will likely dissipate less than a watt, and not get particularly hot.
If you use a little bit of double sided, why not go full out and pack it in a bit? Or were you planning on using jumpers rather than traces on the top side? Rework R3 to be the jumper.
Only the 0R47 may generate heat. The others in that row are gate stoppers (221R), protection circuit (no effect on sound when properly chosen values are used) and the bootstrap for the ACS. There may be some temperature related effects on stoppers and bootstrap, but you can lay out the board to keep them away from heat producing parts. The 0R47s will likely dissipate less than a watt, and not get particularly hot.
If you use a little bit of double sided, why not go full out and pack it in a bit? Or were you planning on using jumpers rather than traces on the top side? Rework R3 to be the jumper.
I value your input and will give it some thought, erm yes, I was planning to use some jumpers, I did not see enough reason in the board to go double layer, not that its a problem, I can make both. I make all my own double layer SMD prototypes down to soic and 0603, I'm layzy and a bit of an obsesive perfectionist, if I get the wrong ideas in my head, they stick like snot to a jersey... I once read this paper on thermal distortion, and the long and the short of it was, more thermal mass and dissipation equaled less distortion. Crazy idea, I know.... but it does no harm as far as I can tell.
Yes, Aleph is a bit strange SE with working load (CCS) that partly acts as an amplifying partner.
Right, it's far less than that - we are talking amp's efficiency, not the Aleph's "current gain" 😉
This is getting pretty OT, but I don't follow you on this. You are saying that doubling the available output current without increasing the overall current draw does not double the amps' efficiency. How did you come up with that?
Best, Bill
Member
Joined 2002
the mini aleph didn't have a output board, the a30 board did because you could build the mini a or a30 ( and other's with the board )
Member
Joined 2002
Original aleph mini
recent smd version of the mini a
a30 & mini aleph board
An externally hosted image should be here but it was not working when we last tested it.
recent smd version of the mini a
An externally hosted image should be here but it was not working when we last tested it.
a30 & mini aleph board
An externally hosted image should be here but it was not working when we last tested it.
I agree, there's enough reading available on this subject, no need to repeat it...
The red one is quite nice, colour aside. A shame it wont fit nicely on a 3" sink, unless it has the mounting rails, but then it juts out in to the case. I'm kind of toying with a few "small" amps trying to decide which one I would use in a triamp setup, and this includes the enclosure which is at such an advance stage of design, I'd rather not start over.
edit, that red one might work nicely if I swing the output pair 90 degrees to go lengthwise off the boards.
edit, that red one might work nicely if I swing the output pair 90 degrees to go lengthwise off the boards.
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Member
Joined 2002
the mini a smd isn't available any more, however you can get the through hole version still.
You could also mount the output fets with a small piece of short wire, like i did with revision 1, or use a piece of l bracket 1/4" thick mounted to fets and heatsinks.
J
Yup, have done the L bracket thing before, as well as the wires, it is not what I'm after this time though, I want it to all look neat and not like all the other stuff I made.
What would a PSU for one of these look like?
What would a PSU for one of these look like?
Member
Joined 2002
the best for the mini a' is the crc, you can buy the psu board and mini a bord from briangt.com
Jason
I will risk sounding like a broken record as I have endorsed this so many times but that MiniA power supply board from BrianGT is the best value out there. The board is beautiful and very stout. Its a nice layout and easy to put together and its a good all around power supply. I have used it as a chip amp supply, a LDR attenuator supply and a headamp supply. Not because they need something like that but just because its easy to throw together and you know its going to work well right off the bat. If I could redesign it I would turn the two inside rectifiers sideways so that its easier to replace them. I had one burn for some reason and had to remove the heatsinks which are obviously not easy to heat up enough to desolder.
Member
Joined 2002
I'm ordering 2 more boards soon, to rebuild my mini a's psu's and go back to the crc
