Yep.
The Gold Cube also employs 4 MOSFET power devices. The case of the Gold Cube consists of 2 halves, each a chunk of solid brass that was milled-out.
(there are/were a few comparable monaurals of other manufacturers, but the Goldmund GC resembles your plan most)
As long as wall thickness is around 1/6'' or more, and thermal transfer/contact across the entire amp case is guaranteed.
I'd add a thermal breaker, glued to the wall of the case, to shut down the amp when case temperature crosses the hazardous line. (e.g. a 50C thermal switch)
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I face the same problem - after a never ending limbo of seeking aluminium in small quantities that guarantees perfect decorative anodization.
This is only manageable if you order 3 tons directly from the forgery with factory certificate - this is what the manufacturers do.
Alloys from traders can have imperfections because sources -forgeries- are unknown. Above all, those imperfections can only be seen AFTER anodization, not before.
So I want to use brass. It can be also painted (of course not there where heat needs to be dissipated).
In case anyone wants to suggest this:
Painting aluminium professionaly needs a special surface treatment called passivation. This adds cost. Or I meet someone from Boeing.
Brass can be painted right away.
Now to my project is a class A/B Amp with DAC.
The brass side panels are very thick:
Almost 5/8" (15mm) for the Power Transistors 2SA1695 / 2SC4467, maximum output power is 80W into 4ohms.
I fact, the Amp it is a resurrected Nakamichi IA-3 amp with better parts and toroidal tranformer, if someone wants to check data. Surprisingly good sound.
As far as I remember, voltage was around 32V.
A heatsink will still be added on the outside of the side panel, it was always part of the original design that was based on aluminium.
I will only change material, not the finished design.
But infortunately the extruded heatsinks that are part of the cabinet/case can not be obtained in copper, remember
galvanic series.
Thus it will still be black anodized aluminium, galvanically isolated from the brass panels. Thus the heat has to cross some junction between brass and aluminium, like mica.
Surface of the side panel is about 34 square inches (0.022m2) without heatsink. (Hope i did the math correctly)
But the amp has also a Buffalo DAC built in with Placid power supplies.
They disspate a lot, but for the transistors, heatsinks like the SK104
SK 104 50,8, Extruded heatsinks for PCB mounting, Heatsinks f.cool, Fischer Elektronik
are normally used. Inside a -closed- cabinet
But I would mount the transistors of the Placids (one single / one dual) on the baseplate. Six TO-220 trannies, four of them laid out in a square of about 5"x2"
Thickness of the bottom plate is about 1/5" (5mm), but surface is rather big:
147 square inches (0.095m2), with thermal connection to the side and front panels
Doable?
BTW, Thermal conductivity / λ (W/(m*K) between the Aluminium alloy (AlMg3) and brass are not that big, at least compared with copper:
Brass: 109 -121
Aluminium (AlMg3):140-160
Copper, pure: 401
Copper normally traded: 240-380
But on the other hand if I understand things correct:
Assuming I would use heatsinks of exact same size (and surface),
Thermal conductivity tells me that the transistors would run 39 degrees centrigrade hotter with the best brass alloy compared to the best aluminium alloy?
But anyway, with the thickness and surface given before, would a brass cabinet be doable?
All the best,
Salar
This is only manageable if you order 3 tons directly from the forgery with factory certificate - this is what the manufacturers do.
Alloys from traders can have imperfections because sources -forgeries- are unknown. Above all, those imperfections can only be seen AFTER anodization, not before.
So I want to use brass. It can be also painted (of course not there where heat needs to be dissipated).
In case anyone wants to suggest this:
Painting aluminium professionaly needs a special surface treatment called passivation. This adds cost. Or I meet someone from Boeing.
Brass can be painted right away.
Now to my project is a class A/B Amp with DAC.
The brass side panels are very thick:
Almost 5/8" (15mm) for the Power Transistors 2SA1695 / 2SC4467, maximum output power is 80W into 4ohms.
I fact, the Amp it is a resurrected Nakamichi IA-3 amp with better parts and toroidal tranformer, if someone wants to check data. Surprisingly good sound.
As far as I remember, voltage was around 32V.
A heatsink will still be added on the outside of the side panel, it was always part of the original design that was based on aluminium.
I will only change material, not the finished design.
But infortunately the extruded heatsinks that are part of the cabinet/case can not be obtained in copper, remember
galvanic series.
Thus it will still be black anodized aluminium, galvanically isolated from the brass panels. Thus the heat has to cross some junction between brass and aluminium, like mica.
Surface of the side panel is about 34 square inches (0.022m2) without heatsink. (Hope i did the math correctly)
But the amp has also a Buffalo DAC built in with Placid power supplies.
They disspate a lot, but for the transistors, heatsinks like the SK104
SK 104 50,8, Extruded heatsinks for PCB mounting, Heatsinks f.cool, Fischer Elektronik
are normally used. Inside a -closed- cabinet
But I would mount the transistors of the Placids (one single / one dual) on the baseplate. Six TO-220 trannies, four of them laid out in a square of about 5"x2"
Thickness of the bottom plate is about 1/5" (5mm), but surface is rather big:
147 square inches (0.095m2), with thermal connection to the side and front panels
Doable?
BTW, Thermal conductivity / λ (W/(m*K) between the Aluminium alloy (AlMg3) and brass are not that big, at least compared with copper:
Brass: 109 -121
Aluminium (AlMg3):140-160
Copper, pure: 401
Copper normally traded: 240-380
But on the other hand if I understand things correct:
Assuming I would use heatsinks of exact same size (and surface),
Thermal conductivity tells me that the transistors would run 39 degrees centrigrade hotter with the best brass alloy compared to the best aluminium alloy?
But anyway, with the thickness and surface given before, would a brass cabinet be doable?
All the best,
Salar
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I always have a fan on my guitar amp designs.
The heat sink is right inside the enclosure on a pcb.
The enclosure I use has plenty of vent holes to get a good air flow through it.
Adding a fan does make noise though, unless you have one that is speed controlled via feedback.
I have a Marshall 100 watt amp with a tiny fan on a heat sink about 30mm by 30mm.
For some reason they use cheap fans and they don't last very long.
I had to replace mine.
The heat sink is right inside the enclosure on a pcb.
The enclosure I use has plenty of vent holes to get a good air flow through it.
Adding a fan does make noise though, unless you have one that is speed controlled via feedback.
I have a Marshall 100 watt amp with a tiny fan on a heat sink about 30mm by 30mm.
For some reason they use cheap fans and they don't last very long.
I had to replace mine.
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