On a slightly more scientific note. Cold 19-20C. After 1/2 hour 34C. After 1 hour 43C. After 90 minutes 47C. After 2 hours 52C. Last night was the hottest ever at 4 hours with the temp being 57C. The power supply for my Bulgin switch circuit is the same voltage as the fans pictured below require so all I have to do is mount them and I'm all set. My first attempt at temperature control will be to build a small bracket that will mount the fans on the back of the amp just in front of (but not touching) the back fins. I'm going to use the two existing screws on each side of the back plate to secure these brackets.
Regards,
Dan
Regards,
Dan
F5 is a true ClassA amplifier.
It will run in ClassA all the way upto it's Maximum ClassA current. All amplifiers abide by that rule.
The F5 will drive an 8r0 test load in ClassA due to the maximum ClassA current being adequate to meet the current demand of that 8r0 load.
It will run in ClassA all the way upto it's Maximum ClassA current. All amplifiers abide by that rule.
The F5 will drive an 8r0 test load in ClassA due to the maximum ClassA current being adequate to meet the current demand of that 8r0 load.
can't say i have noticed that. only the transformers is getting a little hotter when i push it hard.
it will use the quiescent current to power the speakers + the ekstra it draws over that?
i cant see that it dissepate all quiescent and only power the speakers with some of the ekstra power it draws?
Dan,
can you fit a temperature switch that will delay the fans' turn on until the sinks reach or exceed ~50°C?
can you fit a temperature switch that will delay the fans' turn on until the sinks reach or exceed ~50°C?
Based on this information I'm hoping my two small fans will keep me in the safe zone.
Regards,
Dan 🙂
If you run the fan at rated voltage it will be noisy.
Buy a quiet fan and just reduce its voltage and speed until it is doing its job.
They're not difficult to mount, wall plugs will often do, then you can try it without spoiling the finish.
A gentle "waft" of air will improve efficiency notably, especially as you have horizontal heatsinks.
Buy a quiet fan and just reduce its voltage and speed until it is doing its job.
They're not difficult to mount, wall plugs will often do, then you can try it without spoiling the finish.
A gentle "waft" of air will improve efficiency notably, especially as you have horizontal heatsinks.
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Yes. I've already picked one out. And, since these are surplus sinks they are full of pre-tapped holes. I don't even have to drill and tap a hole to mount the thermal switch.
Regards,
Dan 🙂
DW, you have more than adequate heatsinks for standard F5, judging by the picture. Standard F5: ~~1.3A idle current per channel.
But: You *HAVE TO* turn the heatsinks upside so that the natural air convection can strip the heat off the fins. No, you cannot compare your fins (long & dense) with factory-made F5, they are totally different (custom) fin config.
Next; safety - With heatsink temp going as high as 57 Centigrade, and considering that your ambient temp is quite low, you are looking at guaranteed temp run-off and self-destruction. As is, the hot air between the fins is going nowhere, or at least not getting out of Dodge nearly fast enough. The speed of the air exchange IS the cooling.
As far as I can see, the bottom of that case is shut solid? Make sure you have a few vertical air-streams through the case; your capacitors will be very grateful. Drill many holes in the bottom and top cover.
But most importantly, turn the HS upside!!! I know, I know - not what you had in mind in terms of aesthetics.
The only other option that you have is to lower the idle current. Bias it down to 0.4V across the resistor and you'll probably be OK.
Listen to it. Push your speakers to as much as you normally would and decide if the amp sounds any different to you with lowered idle current.
If not, close the (perforated!) lid, it's all good.
No, not the 25W Class-A any more (15W maybe, the rest goes to A/B), but who cares if your speakers are happy and your ears do not object?
Some practical rules of thumb:
- Assume that temp. that you measure on the heatsinks is half of device junction temp;
- do not expose the output devices to more than 1/2 of max rated temp for long periods of time.
- make sure you have a good contact of the device(s) and the HS - touching screw/washer that holds down the FET should feel no more than barely warm, if that. All FET heat should move onto the heatsink and not raise the temp of the plastic/epoxy package itself.
Just my 0.16 ZAR.
My speakers only need about 1W to churn all the SPL that I need, so my next "Summer Version" F5 will be a heavily downsized one using 2 pairs of K2013/J313 at 800mA idle current per channel. Maybe even only one pair @ 400mA. 😉 (Thanks Papa for the most customisable topology ever, thanks Juma for the ready-to-wear K2013/J313 version!)
But: You *HAVE TO* turn the heatsinks upside so that the natural air convection can strip the heat off the fins. No, you cannot compare your fins (long & dense) with factory-made F5, they are totally different (custom) fin config.
Next; safety - With heatsink temp going as high as 57 Centigrade, and considering that your ambient temp is quite low, you are looking at guaranteed temp run-off and self-destruction. As is, the hot air between the fins is going nowhere, or at least not getting out of Dodge nearly fast enough. The speed of the air exchange IS the cooling.
As far as I can see, the bottom of that case is shut solid? Make sure you have a few vertical air-streams through the case; your capacitors will be very grateful. Drill many holes in the bottom and top cover.
But most importantly, turn the HS upside!!! I know, I know - not what you had in mind in terms of aesthetics.
The only other option that you have is to lower the idle current. Bias it down to 0.4V across the resistor and you'll probably be OK.
Listen to it. Push your speakers to as much as you normally would and decide if the amp sounds any different to you with lowered idle current.
If not, close the (perforated!) lid, it's all good.
No, not the 25W Class-A any more (15W maybe, the rest goes to A/B), but who cares if your speakers are happy and your ears do not object?
Some practical rules of thumb:
- Assume that temp. that you measure on the heatsinks is half of device junction temp;
- do not expose the output devices to more than 1/2 of max rated temp for long periods of time.
- make sure you have a good contact of the device(s) and the HS - touching screw/washer that holds down the FET should feel no more than barely warm, if that. All FET heat should move onto the heatsink and not raise the temp of the plastic/epoxy package itself.
Just my 0.16 ZAR.
My speakers only need about 1W to churn all the SPL that I need, so my next "Summer Version" F5 will be a heavily downsized one using 2 pairs of K2013/J313 at 800mA idle current per channel. Maybe even only one pair @ 400mA. 😉 (Thanks Papa for the most customisable topology ever, thanks Juma for the ready-to-wear K2013/J313 version!)
I hooked up one of the fans in the picture to a 9 volt battery and it 'seemed' to move quite a bit of air and was virtually silent. I think I'll start out at full voltage to measure the total cooling affect. After I determine that I think I'll put a pot in series to see what speed offers the best returns.
I think I'm going to ignore repeated and good advice to go vertical on the heatsinks. I think the fans (if they work) are going to be the best solution for me since they are hidden and will only be used part-time.
Another postive to this is................I'll probably build an F6 and I've learned some good 'thermal' lessons in building my F5. 😀
Regards,
Dan
You really are wasting valuable heatsink efficiency with horizontal heatsinks.
How many of us have to tell you to turn them through 90 Degrees.
Even the genuine Pass amps have 45 degree angles on their huge sinks.
How many of us have to tell you to turn them through 90 Degrees.
Even the genuine Pass amps have 45 degree angles on their huge sinks.
I'll repeat myself again. Going vertical is excellent advice. In this particular situation I consider adding fans a better compromise that cutting and reconfiguring my case.
Experience is a great teacher. Even bad experiences are valuable. I was well aware going into this project that my design might have some shortcomings but I was willing to take that risk. I'm going to ventilate the top and bottom plates and add the fans on a thermostatic switch that closes around 45C. After that's all done I'm going to have the best amp I've owned to date.
Regards,
Dan 🙂
The fans will generate the air flow that help the sink to work.
If you are going to use fans anway it doesn't make too much differnce which way they are orientated as long as you have an air flow over the fins.
Purists will argue that silence is better, that can only be achieved by natural air flow. Slow running fans are almost silent too.
Good Luck.
If you are going to use fans anway it doesn't make too much differnce which way they are orientated as long as you have an air flow over the fins.
Purists will argue that silence is better, that can only be achieved by natural air flow. Slow running fans are almost silent too.
Good Luck.
A pot in series is not a good way to ensure reliable motor starting.
It is liable to stall with a low voltage across the motor and it will slowly cook. Ant that implies a high voltage across the pot which will also cook.
It is liable to stall with a low voltage across the motor and it will slowly cook. Ant that implies a high voltage across the pot which will also cook.
You could set up a simple thermistor based temp controller, similar to what is in the F5, and decide exactly what temps you want the fan to maintain. I could draw a diagram if you like. You could pull off you rail and would have ne need for special setup other than tiny board with 2 pots(1 might do), two thermistors (one might do)s, and a fet. Guy just showed it to me. Very simple and clever. To Andrews point, the fan is controlled by the fet acting as a currdnt sink, with its Vgs controlled by pots and thermistor.
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Initial installation will be full voltage at full speed. After I collect temperature data I'll go from there. I really see only two scenarios. One being that the fans are so efficient that they lower the HS temperature to the point where they cycle on and off. Or, they just keep the HS at a safe level. Only time will tell and I will post the results here. If you really want to get technical I have a SPL meter so I can measure fan noise one meter from the amp. I can't see it being anything more than negligible.
Regards,
Dan 🙂
Regards,
Dan 🙂
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