Sanken MLE20
Yep.
A-S2100 - Integrated Amplifiers - Hi-Fi Components - Audio & Visual - Products - Yamaha United States
Yep.
A-S2100 - Integrated Amplifiers - Hi-Fi Components - Audio & Visual - Products - Yamaha United States
An externally hosted image should be here but it was not working when we last tested it.
Plus the earlier released S3000 model.
7 grand for a 100W stereo amp, with 2 MOSFET power devices per channel, amusing times.
1-2 weeks ago I posted pictures of my ExtremA amplifier build and some of you commented about the amplifier itself (Class A - AB issues, dissipation, etc...) and since it is not really the place to comment about the design, I was wondering if you could join the ExtremA thread and help me and some other users experiencing some type of oscillation that could be causing the emitter resistors of the Sanken to heat up pretty much (80+ Celcius). I believe Jacco and some others know about the design and could potentially help?
Here's the thread
http://www.diyaudio.com/forums/solid-state/96853-extrema-class-strikes-back-53.html#post4426326
SSassen is not replying to any massages or thread anymore... So your help would be greatly appreciated.
Thanks in advance
Do
Here's the thread
http://www.diyaudio.com/forums/solid-state/96853-extrema-class-strikes-back-53.html#post4426326
SSassen is not replying to any massages or thread anymore... So your help would be greatly appreciated.
Thanks in advance
Do
At the 100W quiescent condition, by your words.
You posted that the heatsinks are at 50C, when you bias to 65W class A.
Which is around 2A quiescent current (3 emitter resistors in parallel)
~2A times 24.5Vdc rails times 4 makes ~196W dissipation.
50C minus 19C ambient makes a temperature increase of 31 degrees.
31 divided by 196 makes ~0.16 C/W for the heatsinks on one side of your amp case (~0.32 C/W for a single heatsink)
For the 100W condition, you said quiescent current is around 2.75A (4 emitter resistors in parallel)
2.75 times 24.5Vdc times 4 makes ~270W idle dissipation per channel.
270W times 0.16 C/W makes 43 degrees above ambient.
At 19C ambient, a heatsink temperature of 62C.
270W dissipation per channel is 67.5W per device.
The die of the Sanken device heats up at a rate of 125/200 per watt dissipation.
67.5 times 125/200 makes ~42 degrees.
Judging from the pictures of your amp, it appears you are using mica insulators.
At 67.5W dissipation per device, those may add up to 20 degrees to the total.
Means that for the 100W class A condition, the dies of the power devices would be at some 125C.
Idle dissipation of an emitter resistor will be in the range of 1/2 watt.
For a Vishay CPF-3, 1/2 W means a temperature rise of 25C above ambient.
Ambient at that location will not be at 19C however.
Your amp board is mounted to a heatsink with a temperature of 62C, the heatsinks will heat up the board, the board makes temperature of the emitter resistors go up.
You can easily expect something in the order of 35C minimum, would make temperature of the emitter resistors 60C at best.
Secondly :
you mounted the MT200 devices at the closest position to the board, shortest lead length.
Shortest distance between a solder pad for the power device leads and a solder pad for an emitter resistor is less than half an inch.
But if the device leads are connected/soldered to a die which is at 125C, the leads will be really hot as well.
Width of the trace from emitter lead pad to emitter resistor pad is in the order of 120mil. Heat will travel very fast over that half inch stretch.
Moral of the story :
your power amp does not need to oscillate for the emitter resistors to reach 80C.
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[Careless whisper playing in the background] Lyrics:
"There's no comfort in the truth
Pain is all you'll find"
Jacco. remember that this is a bridged thing.
but the end result will be the same anyway
the chassis is good for a 2x50W class A amp as i stated earlier.
there is no way this sinks kan handle 2x100W class A no matte witch way they are pointed a F5 turbo v2 would be perfect Project for this case
but the end result will be the same anyway
the chassis is good for a 2x50W class A amp as i stated earlier.
there is no way this sinks kan handle 2x100W class A no matte witch way they are pointed
a F5 turbo v2 would be perfect Project for this case
Thanks Jacco! This makes total sense
Now I just wish I could lower the power rails by 2-3 volts and adjust the emitter resistor accordingly but I don't know of an efficient way to do so without generating more heat and adding a CRC like config to the PSU won't make me drop 2-3 volts..
Thanks
Do
Exchange the mica insulators for Keratherm red, use two emitter resistors in parallel, and you'll be fine.
Going over 50W class A is difficult with a 4-device output stage (it's a balanced power amp, not bridged)
(I've built mine as monoblocks, with blown high performance heatsinks inside the case, three 80mm latest generation pc fans on top of each, 0.05 C/W)
Going over 50W class A is difficult with a 4-device output stage (it's a balanced power amp, not bridged)
(I've built mine as monoblocks, with blown high performance heatsinks inside the case, three 80mm latest generation pc fans on top of each, 0.05 C/W)
My bad, I meant 2A (three 1R resistors in parallel)
My g/f can be very distracting when I type.
An MT-200 has the largest mounting surface of all regular power transistor packages (2.5 times a TO-247)
Kerafol 86/82 has a thermal resistance which is 1/4th of mica, or less.
For MT-200 devices which are biased to serious idle dissipation levels, it's the ideal insulator material.
Dropping the quiescent current by 25% lowers temperature of the die by 23C, not counting the insulator.
A switch from mica to Keratherm brings die temperature under 90C.
65W class A is less than 2dB down from 100.
That 5U HiFi2000 amp case is surprisingly good, at $250 even more so.
With a dissipation of 200 watt at 50C, it's good for 80-90W in class A for a standard PP output stage design.
The good thing is that electricity is quite cheap in Canada compared to Europe. It won't be for long though before they start being pigs and charge us more even though we "own" one of the largest hydro-electricity company in the world!
Hydro-Québec at a Glance | Who Are We? | Hydro-Québec
Anyways, it is a very efficient chassis but keep in mind that I have added lots of metal to the heatsink to spread the heat evenly across the two heatsinks, and it does work pretty good!
This is a 1/2" (12.7mm) thick plate bolted pretty hard as you can see, using stainless steel mechanic screws (the ones on the pictures are not the final screws). I don't know if just the heatsinks alone would have been that good.
Ciao!
Do
Hydro-Québec at a Glance | Who Are We? | Hydro-Québec
Anyways, it is a very efficient chassis but keep in mind that I have added lots of metal to the heatsink to spread the heat evenly across the two heatsinks, and it does work pretty good!
This is a 1/2" (12.7mm) thick plate bolted pretty hard as you can see, using stainless steel mechanic screws (the ones on the pictures are not the final screws). I don't know if just the heatsinks alone would have been that good.
Ciao!
Do
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the question is how are the thermal coupling between the sinks and that plate? you will lose some watts there. the sinks them self are 10mm baseplate, wich mean they can spred the heat of a radius of 100mm from the devises.
but you do have more serious trouble to pay atention to than this. make the amp work as it should before you think about this.
but you do have more serious trouble to pay atention to than this. make the amp work as it should before you think about this.