Good question!Sweet! Congrats Thimios! I do not see any pots mounted so truly an adjustment free amp. What is DC offset?
Offset=0mV,no pots!
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Congratulations, Thimios!!
Another good amp under your belt!
This thread is almost now at 300 pages. My Golly, I never expected it to be so popular, I would like to thank X, JP, and your wonderful DIYers busy at your workbenches..... thanks to all of you, it makes me feel pretty good, sitting at the **** of the world downunder.
Hugh
Another good amp under your belt!
This thread is almost now at 300 pages. My Golly, I never expected it to be so popular, I would like to thank X, JP, and your wonderful DIYers busy at your workbenches..... thanks to all of you, it makes me feel pretty good, sitting at the **** of the world downunder.
Hugh
Congratulations indeed, Thimios!
Hugh,
I'm not at all surprised, my alpha 20 is a fantastic amp!
Cheers,
Gable
Hi to all, X and Hugh
What would happen if I use two pair power mosfet, the same type you guys use with the CPU cooler just to divide the heat transfer between the two set power mosfet on my passive heatsink. The reason I do not want to give up on this 50W project I have too many amplifier cases from 50W up to 100W for class A amplifier, I decided I will dismantle my DIY Aleph X 120W per channel 7A total bias per channel. Too much power consumption. Same time I have several lowish class A projects like USSA5, First Watt M2, and I still a pair Hiraga class A stuffed PC boards. In one word If I m interested to upgrade the amplifier to get out more power like 50W. Otherwise, it will be one out of many 20-25W amps. We use one or two amps mostly if we go with passive speakers. I do not need one more 20W type. Same time I dismantle the 120W all Class A-AX and cancel the Aleph 2 amplifier. My issue even the high power mosfet will not work with a passive heatsink. I will try to double up the number of power mosfet. You all know those mosfets aren't cheap but I have to try it I do not see other option. If that solution or any other will not work I may give up the Alpha 20W even do I have all the parts to build it. At least until spring.
Greetings
What would happen if I use two pair power mosfet, the same type you guys use with the CPU cooler just to divide the heat transfer between the two set power mosfet on my passive heatsink. The reason I do not want to give up on this 50W project I have too many amplifier cases from 50W up to 100W for class A amplifier, I decided I will dismantle my DIY Aleph X 120W per channel 7A total bias per channel. Too much power consumption. Same time I have several lowish class A projects like USSA5, First Watt M2, and I still a pair Hiraga class A stuffed PC boards. In one word If I m interested to upgrade the amplifier to get out more power like 50W. Otherwise, it will be one out of many 20-25W amps. We use one or two amps mostly if we go with passive speakers. I do not need one more 20W type. Same time I dismantle the 120W all Class A-AX and cancel the Aleph 2 amplifier. My issue even the high power mosfet will not work with a passive heatsink. I will try to double up the number of power mosfet. You all know those mosfets aren't cheap but I have to try it I do not see other option. If that solution or any other will not work I may give up the Alpha 20W even do I have all the parts to build it. At least until spring.
Greetings
Agree, this is an amplifier for beginners!
Can't go wrong, no exotic parts, not many parts, ideal in one word!
Thanks Hugh, thank you xrk for the offer, thank you jp for this excellent pcb!
I will go now for the second chanel.
Regards.
You can do it of course just match your MOSFETs. It’s DIY and worst thing is you melt a few $2 IRFP240/9240’s.
Hi
Talking about the same size mosfet you guys use in the BB. Only I will use 2 pairs for better heat transfer. Unfortunately, those are not $2 value mosfets.
How you see I do not want any cheap solution, I would love to make somehow this work even do those mosfets cost me a lot.
Greetings
Hi Gaborbela,
Matching those $20 IXYS is not economically feasible. Maybe you can try using a thick 12mm copper plate circa 75mm x 100mm (or larger) to help spread the heat laterally from the MOSFET to a larger area on your aluminum fins. Almost like using 6 heatpipes of CPU cooler to get heat to fins for the fans to blow - except here to radiate via fins. Bolt the copper plate to the aluminum fins with good heatsink compound, and of course, bolt the copper plate to the Alpha BB PCB with the ceramic insulators and good heatsink compound. That should work, I think. Drill and tap four holes on the copper plate to match the CPU cooler mounting holes on the Alpha BB PCB (you have lots of options). The copper plate is not cheap, and drilling and tapping it is not easy (copper breaks drill bits and tap bits like crazy if you are not an experienced machinist - I suggest hiring a machine shop to fabricate the 4 plates) - but easier and less expensive than buying 50 to 100 of the big IXYS MOSFETs to match them.
Matching those $20 IXYS is not economically feasible. Maybe you can try using a thick 12mm copper plate circa 75mm x 100mm (or larger) to help spread the heat laterally from the MOSFET to a larger area on your aluminum fins. Almost like using 6 heatpipes of CPU cooler to get heat to fins for the fans to blow - except here to radiate via fins. Bolt the copper plate to the aluminum fins with good heatsink compound, and of course, bolt the copper plate to the Alpha BB PCB with the ceramic insulators and good heatsink compound. That should work, I think. Drill and tap four holes on the copper plate to match the CPU cooler mounting holes on the Alpha BB PCB (you have lots of options). The copper plate is not cheap, and drilling and tapping it is not easy (copper breaks drill bits and tap bits like crazy if you are not an experienced machinist - I suggest hiring a machine shop to fabricate the 4 plates) - but easier and less expensive than buying 50 to 100 of the big IXYS MOSFETs to match them.
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Second chanel when first chanel sing but hot heatsink temperature is 57 celcius(room temperature =20 celcius.
With those really huge heatsinks (they look like USA Heatsink ones from Jeff?) it is 57C? What is the bias current through the MOSFET? 57C is is about right if your sink is sized right on the edge. But should be similar to first channel.
Yes, I have used a pair of back-to-back electrolytics to make a non-polarized cap at C111 and it works fine.
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Tomorrow very likely I will start stuffing the Alpha PC boards.
I just found 4 of this in my box while I was searching for some components, this was designed for F5 X and will be never finished so those audio Toshibas free for use.
I will have to contact Danny let see if he willing to run some simulation before I butcher up that old project.
If I blew up those mosfets I care less those already soldered...
I just found 4 of this in my box while I was searching for some components, this was designed for F5 X and will be never finished so those audio Toshibas free for use.
I will have to contact Danny let see if he willing to run some simulation before I butcher up that old project.
If I blew up those mosfets I care less those already soldered...
Attachments
X,
Are you still running your Alpha 20W with the lower gain using the 15K resistor?
I finally finished my preamp and I’m going to start on the Alpha. I ordered the Easy-Peasy Cap Mx to use with Alpha and the FW M2C. I figured I could switch out the amps to get a little different flavor. Also, I’m using a AnTek with 20v secondaries. It sound work nice with the Cap mx since I will lose a couple of volts.
Thanks for the help,
Brad
Are you still running your Alpha 20W with the lower gain using the 15K resistor?
I finally finished my preamp and I’m going to start on the Alpha. I ordered the Easy-Peasy Cap Mx to use with Alpha and the FW M2C. I figured I could switch out the amps to get a little different flavor. Also, I’m using a AnTek with 20v secondaries. It sound work nice with the Cap mx since I will lose a couple of volts.
Thanks for the help,
Brad
I gave my Alpha 20 to JPS64 and can’t remember what gain setting I have on there. I think it is the lower one though as I was driving it with an Aksa Lender Preamp for volume control so did not need so much gain. I plan to build another set one of these days. Having the Alpha BB and Hugh’s 35w Omega sort of made it not necessary to have a lower power Alpha.
In the Easy Peasy cap Mx thread there is a new Mark johnson BJT cap Mx design that I am using with the M2. It works great and lower dropout voltage. Adjustable dropout between 1.3v and higher (prob up to 4v or so). You might try that too. Only using a pair of 10mF smoothing caps after the rectifier. Enough for 1.5amp low ripple current with 2v dropout.