Another MoFo
#46 Re: Another MoFo
When I finally do a MoFo build (I still have many of the parts and have only sold on surplus items I don't need) I have a pair of single rail SLB power supplies. SLB (Smooth Like Butta) is a cap multiplier supply with an active rectifier - got them on a DIY Audio group buy.
As I mentioned previously on Steve's thread, my driver stage will be based on a pair of 4P1Ls. One day!
As I mentioned previously on Steve's thread, my driver stage will be based on a pair of 4P1Ls. One day!
Sorry, I couldn't resist!
- pre65
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#47 Re: Another MoFo
Just out of interest Ray, what were your thoughts on the heatsinks ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#49 Re: Another MoFo
If on the other hand you're asking about the sizing of the heatsinks, you need to be more specific as the amount of heat to be dissipated will depend on your power supply voltage and what standing current you'll be using.
If you read Michael Rothacher's original document he tells you his recommendation for heatsinking based on the voltage/current parameters he used - page 17.
Ray
If you read Michael Rothacher's original document he tells you his recommendation for heatsinking based on the voltage/current parameters he used - page 17.
Ray
Sorry, I couldn't resist!
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#50 Re: Another MoFo
Yes, in general I appreciate all that, and I have at least 5 different options to think about.
I just wondered if YOU had settled on a particular way to go in that direction.
If not, don't worry.
I just wondered if YOU had settled on a particular way to go in that direction.
If not, don't worry.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#51 Re: Another MoFo
I saw your post on the DIY Audio MoFo thread,,,
You should keep R6 as it gives an easy way to measure your standing current - Ohms law again, handy little beggar! If you omit it you must put a link in its place otherwise your MoFo will not be connected to the power supply.
Regarding the MOTs, these quotes are from little eddy's MoFo thread, Regarding the MOTs (same as the ones you have);
You should keep R6 as it gives an easy way to measure your standing current - Ohms law again, handy little beggar! If you omit it you must put a link in its place otherwise your MoFo will not be connected to the power supply.
Regarding the MOTs, these quotes are from little eddy's MoFo thread, Regarding the MOTs (same as the ones you have);
and using those same MOTs;little eddy wrote: ↑Thu Mar 21, 2019 9:39 pm I went and tested a few and these had the lowest DCR of what I tried, around 2R. I'm sure these tested at above 100mH so no issue with bass response.
The one thing I would suggest is that the MOT eats up voltage and available power so if you want more than say 12W, I would suggest a transformer higher than 18V if conventionally aspirated.
little eddy wrote: ↑Thu Mar 21, 2019 9:39 pm I have a supply voltage of 21.7V to the pcb, so running with 1.7A I have just under 13W output. Dissipation is theoretically 31W. I would really like to run at say 2A so should really have bigger heatsinks than the 0.53 C/W ones I bought, hence me looking at the cpu heatsinks with fans.
Sorry, I couldn't resist!
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#53 Re: Another MoFo
Thanks Ray.
I'd been thinking about a 24V supply and biasing around 2.5A.
I've ordered a 5W R6 now, although I will probably use the MOT terminals to set the bias, now I know how to do it properly.
I have two huge heatsinks 300mm x 200mm x 70mm, and I have no doubt they would cope. BUT, because of the directions of the fins they have to sit 300mm high (as they did on my 50W single ended Mosfet (puck) amp) and that is not conducive to good design.
What I had considered was cutting each one in half, then they are 200mm wide and 150mm high, and using one each side of each monoblock connected by a cross piece of 100mm x 100mm x 6mm alloy angle. The cross piece would have a 6mm plate welded each end so as to bolt to the heat sinks with a 100mm x 100mm x 0.5mm heat conducting pad. The Mosfet would sit on the crosspiece.
https://www.ebay.co.uk/itm/1pcs-100mm-x ... Swo4pYlcjL
Before I go to that extreme I'll use my 3rd (slightly damaged) full size one on a breadboard mock up.
That's the thought for today (it's Sunday now) but as ever with me, things may change.
*
I'd been thinking about a 24V supply and biasing around 2.5A.
I've ordered a 5W R6 now, although I will probably use the MOT terminals to set the bias, now I know how to do it properly.
I have two huge heatsinks 300mm x 200mm x 70mm, and I have no doubt they would cope. BUT, because of the directions of the fins they have to sit 300mm high (as they did on my 50W single ended Mosfet (puck) amp) and that is not conducive to good design.
What I had considered was cutting each one in half, then they are 200mm wide and 150mm high, and using one each side of each monoblock connected by a cross piece of 100mm x 100mm x 6mm alloy angle. The cross piece would have a 6mm plate welded each end so as to bolt to the heat sinks with a 100mm x 100mm x 0.5mm heat conducting pad. The Mosfet would sit on the crosspiece.
https://www.ebay.co.uk/itm/1pcs-100mm-x ... Swo4pYlcjL
Before I go to that extreme I'll use my 3rd (slightly damaged) full size one on a breadboard mock up.
That's the thought for today (it's Sunday now) but as ever with me, things may change.
*
Last edited by pre65 on Sat Jun 27, 2020 12:50 am, edited 2 times in total.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- pre65
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#54 Re: Another MoFo
Other options could be one, or other of these two, but I'd rather not use fans.
https://www.ebay.co.uk/itm/Heatsink-Uni ... 1438.l2649
https://www.ebay.co.uk/itm/Heatsink-Uni ... 1438.l2649
https://www.ebay.co.uk/itm/Heatsink-Uni ... 1438.l2649
https://www.ebay.co.uk/itm/Heatsink-Uni ... 1438.l2649
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
- Paul Barker
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#56 Re: Another MoFo
On fans, if you run the fan at lower voltage you can get them quiet.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
#57 Re: Another MoFo
Give me passive cooling everyday, it's simple, it works, it's silent and there's nothing to go wrong.
Sorry, I couldn't resist!
#58 Re: Another MoFo
I have pc fans on my motor home fridge and cupboard enclosure, they have run continuously and have proved very reliable over the last few years. I'm not into pcs but I don't remember lots of fan failures when I was.
The pc fans on my mofo are virtually silent at just under 5volts, take no space (they are mounted over a hole in the chassis) the circuit board is mounted directly on top of them, so the heat flows vertically, mine where around a fiver each, the amp is cold, even after last night's 6 hours running
In my limited experience so far, theres alot to like about them
My adjustable dc to dc converter, about £2 ebay, makes adjusting them to 'just enough draught' is great
The power supply is a miniature wall wart that plugs into a small caravan type 13amp socket mounted internally, I had all the parts.
Works a treat.
The pc fans on my mofo are virtually silent at just under 5volts, take no space (they are mounted over a hole in the chassis) the circuit board is mounted directly on top of them, so the heat flows vertically, mine where around a fiver each, the amp is cold, even after last night's 6 hours running
In my limited experience so far, theres alot to like about them
My adjustable dc to dc converter, about £2 ebay, makes adjusting them to 'just enough draught' is great
The power supply is a miniature wall wart that plugs into a small caravan type 13amp socket mounted internally, I had all the parts.
Works a treat.
The tube manual is quite like a telephone book. The number of it perfect. It is useful to make it possible to speak with a girl. But we can't see her beautiful face from the telephone number
#59 Re: Another MoFo
I was just expressing a preference, not criticising, Steve...
Last edited by Ray P on Sat Jun 27, 2020 11:23 am, edited 1 time in total.
Sorry, I couldn't resist!
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#60 Re: Another MoFo
Indeed Paul. I had fans on the 50W Mosfet amp, and running from a bench power supply I could turn the voltage down so they ran quiet but still did a good enough job.Paul Barker wrote: ↑Sat Jun 27, 2020 8:56 am On fans, if you run the fan at lower voltage you can get them quiet.
I went for a good quality (Arctic) fan quite big ,(5.5" square) so I got enough volume of air without high revs.
IF by any chance,(when on test) the big heatsink proves to be inadequate then I still have the fan option.
The huge 50W amp is being broken up so things like heatsinks, fans, inductors in the power supply etc can, and will be, reused.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)