That wasn't intended for you to answer QUSP, I used your link to just generally point out something to the readers
The point is that people who want higher power might be interested in knowing and welcome that tidbit of data
220W is by no means extremeFairly normal really amongst all my friends with not particularly efficient floor standers in say a 10 foot by 14 foot room. It does no harm to have some headroom and a bigger better PSU often confers better transient response.
Our 100W per channel integrated amp has 80,000uF and a 500VA. It beats 200W per channel amps. A pal with one recently took it to a high end shop to evaluate another amp and speakers he was looking to buy. The dealer commented how it beat that amp retailing at £2500 (or maybe it was £5000, I've forgotten, but it's equalled £5000 amps before). The decent PSU is in no small part responsible for this and it's why higher power amps often sound better than lower power ones.
well i'm afraid i do have to answer you then, because i don't think that 200w will be a problem at all for the larger of the 2. i guess it depends how you set the idle current
also, why is it that you always seem to talk like 'the borg'? talking of yourself in the plural
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
The Hi-Fi cottage industry 'we' run / ran is a joint operation. I'm usually testing and developing with other people. I use 'we' to show that it's not just my opinion but that of more than just me. I'm not the most technically informed of us so have to refer to the specific memory banks of others
Last edited:
sorry i'm not trying to belittle/ridicule you above, don't take it that way, i just prefer carrying on a conversation with one person and their opinions, not someone who calls in the weight of other opinions not present as well for backup. maybe its unintentional, but I've noticed you do it a lot.
anyway back to the thread. i'm only shooting for 150-200WPC and i feel pretty confident that even the smaller of the 2 will cope with 200w if not left with no signal for extended periods and the larger of the 2, the mf30-100 or mf35-100 without problem as long as the thermal coupling is good. plus i don't mind silent fans, i have quite a few silent pc fans that i will enslave if needed. but i'm guessing you object to them and thats cool, each to their own i guess
anyway back to the thread. i'm only shooting for 150-200WPC and i feel pretty confident that even the smaller of the 2 will cope with 200w if not left with no signal for extended periods and the larger of the 2, the mf30-100 or mf35-100 without problem as long as the thermal coupling is good. plus i don't mind silent fans, i have quite a few silent pc fans that i will enslave if needed. but i'm guessing you object to them and thats cool, each to their own i guess
Last edited:
........testing and developing with other people, often at customers on their systems, of whom I have / had several running in / testing items for me on-going for which they get upgrades and parts at cost.
I need to know what 'we' do sounds good on many different systems, not just mine.
Anyway, if kept saying 'I' this and 'I' that people would think I was big headed and a know it all, which I'm not. The more one knows, the more one realises there is to know.
Regarding the heat sink basal thickness, you can just buy and try. Build it up and use a thermocouple probe to sense the temperature on the devices. It will probably be fine. Just that I and my colleagues like to run them cooler Lower r on, lower output Z, might be better sound. I've not tested to see if I can hear the difference that a cooler mosfet makes, if any, but our sinks do feel farily hot at only 45°C and they are fairly large. It's not uncommon to use 100mA per pair which will make the sinks hotter, but 60mA might be OK. I've not heard it for myself they apparently can sound less good if too low a quiescent is used. IIRC my Halfer DH200 used 150mA per pair and my Meridian 605 use 80mA. My colleague was using 100mA in the 1990's but turned it down to 80mA without noticeable degradation he said. He didn't like the amount of heat they were giving out and felt the sinks were too hot. He's aiming for 40°C as the curve of resistance vs. temp looks better to him at that.
I measured the devices on a mosfet amp with a 300mm by 75mm sinks with a very thick base, maybe 20mm, but the mosfets are on a bar which is bolted to the main sink. The main sink is just warm but the devices; as much as 60°C. They have reduced the maximum power at that temp. I forget the numbers, but 75°C = something like halving the output power. You'd have to look it up, or someone who knows can add it here
I and my colleagues ( ) parallel a four pairs of them and use a whopping PSU to get the lowest output impedance we can. Why spoil that with a high die temp?
Of course, if you're going to use these alfets, they are 'double die' aren't they? So you can half the number of pairs for the same output Z and maybe half the heat. So that's all good.
Can I ask were you get the surface mount Vishay bulk foils? Thanks. I use the VSH from Michael Percy but like you I might like to use surface mounts on the headphone board.
I need to know what 'we' do sounds good on many different systems, not just mine.
Anyway, if kept saying 'I' this and 'I' that people would think I was big headed and a know it all, which I'm not. The more one knows, the more one realises there is to know.
Regarding the heat sink basal thickness, you can just buy and try. Build it up and use a thermocouple probe to sense the temperature on the devices. It will probably be fine. Just that I and my colleagues like to run them cooler
Lower r on, lower output Z, might be better sound. I've not tested to see if I can hear the difference that a cooler mosfet makes, if any, but our sinks do feel farily hot at only 45°C and they are fairly large. It's not uncommon to use 100mA per pair which will make the sinks hotter, but 60mA might be OK. I've not heard it for myself they apparently can sound less good if too low a quiescent is used. IIRC my Halfer DH200 used 150mA per pair and my Meridian 605 use 80mA. My colleague was using 100mA in the 1990's but turned it down to 80mA without noticeable degradation he said. He didn't like the amount of heat they were giving out and felt the sinks were too hot. He's aiming for 40°C as the curve of resistance vs. temp looks better to him at that.I measured the devices on a mosfet amp with a 300mm by 75mm sinks with a very thick base, maybe 20mm, but the mosfets are on a bar which is bolted to the main sink. The main sink is just warm but the devices; as much as 60°C. They have reduced the maximum power at that temp. I forget the numbers, but 75°C = something like halving the output power. You'd have to look it up, or someone who knows can add it here
I and my colleagues (
) parallel a four pairs of them and use a whopping PSU to get the lowest output impedance we can. Why spoil that with a high die temp?Of course, if you're going to use these alfets, they are 'double die' aren't they? So you can half the number of pairs for the same output Z and maybe half the heat. So that's all good.
Can I ask were you get the surface mount Vishay bulk foils? Thanks. I use the VSH from Michael Percy but like you I might like to use surface mounts on the headphone board.
Last edited:
I've started thinking about a chassis for my amps. Previously I was thinking of fitting all 8 channels in one large chassis, but I think I will build them as 4 separate stereo amplifiers instead. This will give me more flexibility in future.
My goals are to make the chassis as compact as possible whilst still providing adequate heatsink area. With this in mind, I thought about the possibility of using the lid and base of the chassis to act as an extension of the main heatsinks.
I did a quick model based around the assumption that I'll use an SMPS, and probably mount the amp modules sideways, with the input towards the rear.
Any thoughts on this approach?
My goals are to make the chassis as compact as possible whilst still providing adequate heatsink area. With this in mind, I thought about the possibility of using the lid and base of the chassis to act as an extension of the main heatsinks.
I did a quick model based around the assumption that I'll use an SMPS, and probably mount the amp modules sideways, with the input towards the rear.
Any thoughts on this approach?
Attachments
Nice drawings Can you get extrusions or castings like those?
If the sinks are thin and the output devices are toward one end, that end tends to be hot and the other end cool and not helping much to dissipate. That's when a thick base is needed. As I said earlier, Meridian 605 has a 22mm base and they are still quite a bit hotter at one end.
My personal preference is to have short speakers leads and long interconnects as that way around has always sounded better to me, with big speakers though. But can easily hear the effects of 2 metre speakers cable with mid size speakers with a 6 inch Kevlar bass/mid so I expect they will be better too with minimal speakers leads. Save for those people who use a longish thick stranded cable to give them a warmer (though 'muddy') tonal balance when their system would sound too thin to enjoy otherwise.
Mono blocks do mean twice the PSU and more case costs. But if these SMPS's are lowish cost then 8 boxes is more affordable. And they'd be small too, that determined by the heat dissipation required. So in that respect are you using one pair of Alfets or two pairs per amplifier board? And what quiescent and peak output?
You might also get better channel separation / stereo / clean sound / transient response with one SMPS per board. That perhaps won't be known until someone / people try it.
Can you get extrusions or castings like those?If the sinks are thin and the output devices are toward one end, that end tends to be hot and the other end cool and not helping much to dissipate. That's when a thick base is needed. As I said earlier, Meridian 605 has a 22mm base and they are still quite a bit hotter at one end.
My personal preference is to have short speakers leads and long interconnects as that way around has always sounded better to me, with big speakers though. But can easily hear the effects of 2 metre speakers cable with mid size speakers with a 6 inch Kevlar bass/mid so I expect they will be better too with minimal speakers leads. Save for those people who use a longish thick stranded cable to give them a warmer (though 'muddy') tonal balance when their system would sound too thin to enjoy otherwise.
Mono blocks do mean twice the PSU and more case costs. But if these SMPS's are lowish cost then 8 boxes is more affordable. And they'd be small too, that determined by the heat dissipation required. So in that respect are you using one pair of Alfets or two pairs per amplifier board? And what quiescent and peak output?
You might also get better channel separation / stereo / clean sound / transient response with one SMPS per board. That perhaps won't be known until someone / people try it.
Last edited:
I'll be CNC machining the components so don't need extrusion or casting.
I'm only planning on running one pair of fets per board. My woofers and subwoofers are 4 ohm and with Cristi's new SMPS I will probably chose something around 50-55V. This might be pushing the pair of fets a little, but I will probably run quite low quiescent current on the woofer/subwoofer amps to help keep them cool.
Mid and tweet amps will only see 8 ohms, and I might go for a lower voltage. For these I will push the bias as far as required for best results (Assuming temp doesn't become an issue)
I'm not too worried about sharing one SMPS between 2 amps, as they won't be sharing left and right channels.
I'm only planning on running one pair of fets per board. My woofers and subwoofers are 4 ohm and with Cristi's new SMPS I will probably chose something around 50-55V. This might be pushing the pair of fets a little, but I will probably run quite low quiescent current on the woofer/subwoofer amps to help keep them cool.
Mid and tweet amps will only see 8 ohms, and I might go for a lower voltage. For these I will push the bias as far as required for best results (Assuming temp doesn't become an issue)
I'm not too worried about sharing one SMPS between 2 amps, as they won't be sharing left and right channels.
HYPERTUNE:
Very nice work on the chassis! I like the symmetrical layout, and the way you've kept the power section shielded from the amps. Using the shield as a heat spreader on the top of the output devices is also a clever idea, and will definitely help to keep even pressure and might even dissipate a little heat if you use a thermal conductor between the top of the fets and the shield.
As for orientation of the amp itself, I don't really think it makes much of a difference overall. You're talking about a difference in cable length of about 2 inches which is nothing compared to the several feet needed outside the enclosure. If anything, it would probably be best to keep the inputs as far from the AC inlet as possible, which would probably mean orienting the boards with the input to the back and the outputs to the front. This also allows you to get the fets as close to the middle of the heatsink as possible.
On that note, Ian is correct about using a decent size base for the heatsinks, especially if you mount the fets way off centre. There are diminishing returns on that though, and once you hit a certain thickness, there's not much sense in going any further. Same applies to fin length.
As for the crosshatch top and bottom, I think it would provide a huge amount of passive cooling capacity if you can thermally bond it to the side sinks in an effective manner. The cross hatch pattern would definitely encourage convection cooling, so it's just a matter of getting the heat into those parts.
Care to trade chassis for a few amplifier kits? Send me a note and we'll see if we can work something out!
Cheers,
Owen
Very nice work on the chassis! I like the symmetrical layout, and the way you've kept the power section shielded from the amps. Using the shield as a heat spreader on the top of the output devices is also a clever idea, and will definitely help to keep even pressure and might even dissipate a little heat if you use a thermal conductor between the top of the fets and the shield.
As for orientation of the amp itself, I don't really think it makes much of a difference overall. You're talking about a difference in cable length of about 2 inches which is nothing compared to the several feet needed outside the enclosure. If anything, it would probably be best to keep the inputs as far from the AC inlet as possible, which would probably mean orienting the boards with the input to the back and the outputs to the front. This also allows you to get the fets as close to the middle of the heatsink as possible.
On that note, Ian is correct about using a decent size base for the heatsinks, especially if you mount the fets way off centre. There are diminishing returns on that though, and once you hit a certain thickness, there's not much sense in going any further. Same applies to fin length.
As for the crosshatch top and bottom, I think it would provide a huge amount of passive cooling capacity if you can thermally bond it to the side sinks in an effective manner. The cross hatch pattern would definitely encourage convection cooling, so it's just a matter of getting the heat into those parts.
Care to trade chassis for a few amplifier kits? Send me a note and we'll see if we can work something out!
Cheers,
Owen
The heatsinks I've drawn there have a base of 10mm and fin height of 40mm. Anything you see there is very much open to suggestion and those models are more of a proof of concept at this stage.
I'd be glad to make an extra chasssis for you. Might be an idea to pick a nice compact IEC connector with fuse and switch. Any preferences? Also let me know whatever plugs & binding posts you'd like.
I'd be glad to make an extra chasssis for you. Might be an idea to pick a nice compact IEC connector with fuse and switch. Any preferences? Also let me know whatever plugs & binding posts you'd like.
great stuff mate!! very interesting. so will use annealed shields? or doesn't this matter if you use solid material cnc from solid block?
machining from solid can never be cheap.............I can say that it is certainly not the most cost effective way to make a chassis
That is the way they made the skins for the Concorde structure.