Hi all,
I have the parts to beuid an F6, sans toroid. But the standard 4U enclosure will not meet with my wife's decorating approval. The amp will go in the living room and there is no place to put it without it looking obtrusive.
I have plenty of places I can put a 2U high unit out of sight and still provide for good ventilation.
So, I was thinking to make two 2U monoblocks but with the output MOSFETs connected to their own heat sinks on each side of the chassis. It will look like a lower profile steroo amp but actually be a monoblock.
Questions: What are the issues in doing this? I'd have to run wires to the SD and G pins from the board to each MOSFET on each side. Probably 4~6 inches for each run. Will this be a problem?
Any suggestions?
Has anyone tried ths?
Many thanks for your help.
I have the parts to beuid an F6, sans toroid. But the standard 4U enclosure will not meet with my wife's decorating approval. The amp will go in the living room and there is no place to put it without it looking obtrusive.
I have plenty of places I can put a 2U high unit out of sight and still provide for good ventilation.
So, I was thinking to make two 2U monoblocks but with the output MOSFETs connected to their own heat sinks on each side of the chassis. It will look like a lower profile steroo amp but actually be a monoblock.
Questions: What are the issues in doing this? I'd have to run wires to the SD and G pins from the board to each MOSFET on each side. Probably 4~6 inches for each run. Will this be a problem?
Any suggestions?
Has anyone tried ths?
Many thanks for your help.
If you do this (and I am not recommending it), the gate resistors should still be located
at the gate pin of each device.
at the gate pin of each device.
audiosteve,
A couple of options before you resort to "flying leads" for your MOSFETs.
Will 3U height work for you? AFAIK some folks have built F6 clones with 3 chassis.
Another though that comes to mind is some form of active cooling that can pull / blow the heat away.
Flying leads for MOSFETs is not a particularly popular build technique; I have seen diyA member xrk971 do it for other projects (not an F6 clone).
I am also thinking, even with flying leads, a sole MOSFET placed in the middle of a narrow and low height heat-sink - would it manage to conduct enough heat from a single point?
A couple of options before you resort to "flying leads" for your MOSFETs.
Will 3U height work for you? AFAIK some folks have built F6 clones with 3 chassis.
Another though that comes to mind is some form of active cooling that can pull / blow the heat away.
Flying leads for MOSFETs is not a particularly popular build technique; I have seen diyA member xrk971 do it for other projects (not an F6 clone).
I am also thinking, even with flying leads, a sole MOSFET placed in the middle of a narrow and low height heat-sink - would it manage to conduct enough heat from a single point?
I have built an F6 in a 120mm tall chassis, here: https://www.diyaudio.com/forums/pass-labs/166784-pictures-diy-pass-amplifier-369.html#post4818715
It's hot but it works well. Also read the advice to put spacers between panels, should make a big difference
It's hot but it works well. Also read the advice to put spacers between panels, should make a big difference
I have been toying with a smaller profile class A (possibly a taller cube profile, but only 260mm wide). I've been looking for heatsinks from Brimingham Aluminium (you must have similar suppliers in the US), mainly as they have a useful online calculator to show the effectiveness of their different extrusions:
Aluminium heatsink |heatsinks | BAL Group Ltd
I reckon the 4ux300mm case heatsink is good for about 0.345C/W per side, based on roughly similar heatsinks' published figures. I'm pretty sure I've read 0.6C/W per device as a figure on one of Nelson Pass' manuals for the F series amps, which seem fairly similar the F6 one of the cooler running designs I believe.
So based on all my shifty assumptions 2U is 89mm, less 3mm for covers overlapping the heatsinks, you have 83mm of heatsink height available. Something like their 1633HS profile (83mm length gives 0.309C/W in free air) would be sufficient cooling on one side only (for the 2 devices).
Heatsinks: 1000 Series - 1633HS | BAL Group Ltd
You would need some very creative packaging to get it all in, if trying to do the whole amp in one chassis you would have 170mm or width taken up by heatsinking alone!
Aluminium heatsink |heatsinks | BAL Group Ltd
I reckon the 4ux300mm case heatsink is good for about 0.345C/W per side, based on roughly similar heatsinks' published figures. I'm pretty sure I've read 0.6C/W per device as a figure on one of Nelson Pass' manuals for the F series amps, which seem fairly similar the F6 one of the cooler running designs I believe.
So based on all my shifty assumptions 2U is 89mm, less 3mm for covers overlapping the heatsinks, you have 83mm of heatsink height available. Something like their 1633HS profile (83mm length gives 0.309C/W in free air) would be sufficient cooling on one side only (for the 2 devices).
Heatsinks: 1000 Series - 1633HS | BAL Group Ltd
You would need some very creative packaging to get it all in, if trying to do the whole amp in one chassis you would have 170mm or width taken up by heatsinking alone!
You could mount the heatsinks as the 'top-face' of your case and emit the heat that way and keep case dimensions flexible - it's 'been done' before!
Perhaps two enclosures instead of one? Allows for different aesthetic approaches and heat management. Going mono has it's benefits on top of that.
Thanks for all the suggestions. Great input. Please contiue to coment of you have any thoughts on this. Cheers!
If this helps, my standard M2 lives in a Modushop 3U 300cm enclosure. It stands on top a open shelf, with space all around. In winter it's just warm. In summer (35ºC) it gets hot, but I can touch heatsinks 5 seconds.
Crikey hot, using Nelson's words. My amplifier is almost one year old, one summer on it and 0 problems.
I think my enclosure is the smallest possible without fans. If yours is smaller, maybe look a Babysitter.
Victor
Crikey hot, using Nelson's words. My amplifier is almost one year old, one summer on it and 0 problems.
I think my enclosure is the smallest possible without fans. If yours is smaller, maybe look a Babysitter.
Victor
That's good data. Thanks Vitorio. Unfortunately I need to put my amp(s) under a credenza. 2U at best and I'll have to be sure of the space around it. I'm still sorting through all the ideas. I'm now leaning towards 4 chassis. Two for the amps and two for separate power supplies of 200VA each. The amp chassis would use 5U by 300 mm heatsinks placed flat, as if they are the top lid. I think that can work OK. That would be very low profile with generous heatsink area. But I'm still thinking about it.
audiosteve,
A heatsink placed flat will have a height of 40-50mm including fins. If 2U is the goal, it's still gonna be tight... And a heat-sink placed flat on the top will have a little less efficiency vs one with fins in vertically oriented.
Interesting challenge you have. Fan cooled doesn't appeal to you? 🙂
A heatsink placed flat will have a height of 40-50mm including fins. If 2U is the goal, it's still gonna be tight... And a heat-sink placed flat on the top will have a little less efficiency vs one with fins in vertically oriented.
Interesting challenge you have. Fan cooled doesn't appeal to you? 🙂
Last edited:
If 2U you really should add a fan. A Noctua running at 1/2 speed will be silent.
3U 400mm will be fine for passive cooling, but that assumes having space above/below the sinks for natural convection to work.
3U 400mm will be fine for passive cooling, but that assumes having space above/below the sinks for natural convection to work.
The DiyAudio heastsinks are 40 mm = 1.6 inches and I'd use the 5U size to compensate for horizontal placement. That leaves 1.9 inches to mount the board nuder it for 3.5" total. I have about 4.5 inches to play with. Tight but possibe.
I might also build small supports for the credenza legs that look good and will raise it an inch or two to give me more room.
I'm not a fan of having a fan unless it can be totally quiet? Do you know of any? Another thought. I am building some smallish transmission lines that would do well to have a void in the base to raise the tweets to ear level, Perhaps I can build the amps in there.
Still sorting it out but getting good ideas from the hive mind while dong it.
Thanks!
I might also build small supports for the credenza legs that look good and will raise it an inch or two to give me more room.
I'm not a fan of having a fan unless it can be totally quiet? Do you know of any? Another thought. I am building some smallish transmission lines that would do well to have a void in the base to raise the tweets to ear level, Perhaps I can build the amps in there.
Still sorting it out but getting good ideas from the hive mind while dong it.
Thanks!
Heatsinks are about heat transfer. They have to move the heat from the transistor to the metal of the heatsink to the air.
They must have airflow around them.
Mounting heatsinks fins facing up decreases their efficiency by 40-60% (!!!) depending on power.
They must have airflow around them.
Mounting heatsinks fins facing up decreases their efficiency by 40-60% (!!!) depending on power.
A tip on finding out what might qualify as "silent".
Google "how loud is it in a silent room".
Then check Noctua fan decibel levels and compare. For 2U you are looking at fans with a diameter of 80mm or less. Bigger diameter fans can move more air at lower speeds.
Google "how loud is it in a silent room".
Then check Noctua fan decibel levels and compare. For 2U you are looking at fans with a diameter of 80mm or less. Bigger diameter fans can move more air at lower speeds.
Last edited:
I have a Noctua NF-A14 ULN, Ultra Quiet Silent Fan, 650 rpm, and with amp off, I have to look to see if the fan is on. It takes 10°C off my F6.
Thanks for all the input. I've settled on this. Cut to 2U height it should work well.
300x83x88 mm.
I'll probably configure as two monoblocks.
ABL Heatsinks
It can be prdered from the RS United States website althogh it is shpped frm the UK.
300x83x88 mm.
I'll probably configure as two monoblocks.
ABL Heatsinks
It can be prdered from the RS United States website althogh it is shpped frm the UK.