Nice setup there Meper, this is purely a prototype setup and as such, has been great for testing. Installing the amp PCB and MOSFET into the heatsink CPU cooler is a 30 second operation with a hex screw driver. I can’t imagine how slow this would have been had I used a traditional case for development.
Next step is for a proper amp PCB and single rail cap Mx layout. Then it can be beautified and put in some sort of chassis. The open air extruded rails look quite nice.
I am planning on using a new compact cap Mx (MrEvil type) with a new integrated active bridge using LT4320 and a pair of SMT dual N channel MOSFETs that will allow up to 5amps with almost no heat output (no heatsink needed).
I have "only" 3A bias. With 26 VDC this is about 80W in heat. It is what the heatsink can take (approx. 54 C). The choke can take much more but I am very satisfied so far with the sound and the BA3-pre is a good match. It takes 1/2 - 1 hour of heating up before the sound quality is at maximum. Good to hear that your plan is to make a final version of the MoFo!
I salvaged 3 of these heat sinks quite a while ago. What are the chances? I can just remove all other devices except one and solder on to what is remaining of the leads. I believe the IRFP250 devices are OK. Hopefully the heat sink is large enough.
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Looks like the heat sink will work, especially for a 19v version.
They appear to be a couple inches thick. Vertical is best or fins pointing up on top of the case.
They appear to be a couple inches thick. Vertical is best or fins pointing up on top of the case.
Just a note that almost any undersized heatsink can be augmented substantially to about 10x nominal capacity with a small silent Noctua fan. You won’t hear it but it may be a good option for those not wanting to buy a bigger heatsink.
Finally up and running in full stereo with MOAMOFO. Currently operating at 36Vdc rail, 4.35A bias current, and driven by Melbourne Preamp. Once I upgrade the power supply trafo on the Melbourne to +/-28v (currently 24.5v), should be good for almost 50w into 6.8ohms. Right now in main listening room and driving very inefficient (82.4dB sensitive) but superb sounding transient perfect ScanSpeak 10F/Dayton RS225 FAST speakers. There is an abundance of power and no sense of strain. Sounds wonderful.
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If you are adventurous, you could cut all three heat sinks in half, screw 3 of them vertically into an aluminum plate at least 5mm thick of equal dimensions,
to use like a traditional case as you see in the store.
This would work well if you are using external laptop power supplies.
to use like a traditional case as you see in the store.
This would work well if you are using external laptop power supplies.
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You could get almost 50wrms into 6.8ohms as shown above. Although I am using 300VA toroidal trafo and cap Mx.
SMPS rated for 5A usually don’t like to operate continuously at the max rated power. I will take a look at the meanwell but would be better to run a 10A rated one at 5A.
I removed that part of my post, because I could not remember of if it was Parts Express or Marlin P Jones' site.
I agree about the power usage.
I agree about the power usage.
This is 36V ~10A SMPS by Meanwell and is $37 but has a small fan. If replaced by Noctua, could be made very quiet. Ideally needs to be about 39v to allow 2v drop through cap Mx for soft start and cleanup.
LRS-350-36 MEAN WELL USA Inc. | Power Supplies - External/Internal (Off-Board) | DigiKey
LRS-350-36 MEAN WELL USA Inc. | Power Supplies - External/Internal (Off-Board) | DigiKey
I know that cap multipliers have been talked about a lot in different threads, but is there a reference for them? Seems to be arguments as how to best implement them.
Is there a basic starting point to accomplishing a workable circuit?
thanks,
Vince
Is there a basic starting point to accomplishing a workable circuit?
thanks,
Vince
are the chokes used for HID discharge lamps also gaped
maybe the 400W HID 230v could be used for the MoFO?
maybe the 400W HID 230v could be used for the MoFO?
There are several cap Mx threads. The ones that work well with a big Class A amp need to have adjustable voltage drop of circa 1.3v to 2.5v. Using a simple MOSFET like the standard Juma Easy Peasy one has 4v drop and that is just too much excess heat burned off.
The ones I have tried and work include the JasonKeutermann MrEvil cap Mx, and the Mark Johnson / Prasi BJT cap Mx.
They are in these threads.
Simplified MrEvil / PMI Capacitance Multiplier
Juma's Easy-Peasy Capacitance Multiplier
The ones I have tried and work include the JasonKeutermann MrEvil cap Mx, and the Mark Johnson / Prasi BJT cap Mx.
They are in these threads.
Simplified MrEvil / PMI Capacitance Multiplier
Juma's Easy-Peasy Capacitance Multiplier
I have a problem. I have constructed two amps as per the recommended boards, components including the 193T's. I am using a same spec Dell power supply.
I have biased them as recommended. Voltage across the inductor is 1.10 vdc
Problem is no sound output. I have done some basic measurements. DC voltage in is 19.75 vdc. Voltage across the transistor is as follows. Gate 5.41 vdc, Drain 19.75 vdc, Source 1.10 vdc.
Suggestions please
I have biased them as recommended. Voltage across the inductor is 1.10 vdc
Problem is no sound output. I have done some basic measurements. DC voltage in is 19.75 vdc. Voltage across the transistor is as follows. Gate 5.41 vdc, Drain 19.75 vdc, Source 1.10 vdc.
Suggestions please
Badge, Do you have any pics of your build?
Did you look at output cap orientation?
Did you look at output cap orientation?
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Sometimes connecting reverse polarity from source gives no sound. You have proper bias current so it should work. Listen to your source first on another device to make sure it is generating signal. The source needs to be able to drive 8Vpp just to get 1wrms output. What’s your source?