I think your fan must be the same size than your copper heatsink as tall and wide. Or you must make some adapter so all the air force to go true the heatsink. Like these, see the plastic at Dell. I have two Dell computers. Dell CPU Heatsink Optiplex GX620 330 740 745 755 E521 J9761 D9729 Mini-Tower OEM | eBay You have not much room there so the 2 fan option may be better. Two fans next to each other. That one fan like how is in the picture is not enough. Just an advise
Especially summer time if you run the amp several hours it will get fried. I forget to mention your fan must take fresh air from outside of the enclosure!
Attachments
Better mains for audio equipment. Tune up a bit.
Higher harmonics reduce much quicker in amplitude.
Sound will be clearly different.
Hi Tonza,
A good system, BUT it requires not one, but TWO transformers, and the third transformer for the step down for the secondaries. This will work beautifully, and remove a good deal of the grunge and the DC on the mains, but the power supply on any amp is the most expensive part and you are suggesting almost tripling the cost.
The idea of a good engineer is to do what any layman can achieve, but at ten times lower cost......... something to think about!
Now, to end on a positive tone, how is your ALPHA coming along and do you have any thoughts on the sound quality?
Ciao,
Hugh
A good system, BUT it requires not one, but TWO transformers, and the third transformer for the step down for the secondaries. This will work beautifully, and remove a good deal of the grunge and the DC on the mains, but the power supply on any amp is the most expensive part and you are suggesting almost tripling the cost.
The idea of a good engineer is to do what any layman can achieve, but at ten times lower cost......... something to think about!
Now, to end on a positive tone, how is your ALPHA coming along and do you have any thoughts on the sound quality?
Ciao,
Hugh
This is a dc test only!
As it is important to send pictures here, I got it to about there nJust played around with input shorted, dc of course. Try a few hexfet next & see if it will behave as amp. Used what I have not the best build but.....
We can increase parallel fets in your ltspice or Danny's we can get it stable to smaller loads even under 1 ohm, no problem. But the res. 0.27 & better be tight tolerance in ltspice world.
Zalman cooler used to get a Ati Radeon graphics card to 44 max 50 Celsius. The heat pipe is with 3 fan92mm could not handle the heat as well the card was heavyly overclocked so summer is coming and se push pull is a thingy to have.
I gave some thought on the protection system, at mega nano does not cut it.
We need m16 or even a m32 a cisc microcontroller.
We can use c compiler but true bit heads want assembly.
I wrote a paper can, t find it now.
USB loader firmware updater
with a graphical op interface system.
Hdmi output for this. So it is more enjoyable for end user.
RTOS for the protection sections
Uv meter from luxman style.
Fft display, in 3d of course
The preamp front all the connections we at daily basis.
As we are on it a option of filter types, do we need room corrections? lower free freq desired,
Where is that paper can't, find it.
Wonderfull result...it is an Aksa tuned?
Very good....Aksa is already wonderfull...tuned can be even better as Hugh
has not all that time free to be tuning once and once again.....and we can
extract some more juice from every fruit....but a question always remains.
Sonic quality....have increase too?.... it may be possible an yes as answer..but
sometimes not.
I hope one original unit was saved in order to compare.
Sorry if i am talking foolishes..i have not readed all thread.
regards,
Carlos
Very good....Aksa is already wonderfull...tuned can be even better as Hugh
has not all that time free to be tuning once and once again.....and we can
extract some more juice from every fruit....but a question always remains.
Sonic quality....have increase too?.... it may be possible an yes as answer..but
sometimes not.
I hope one original unit was saved in order to compare.
Sorry if i am talking foolishes..i have not readed all thread.
regards,
Carlos
That heatpipe CPU cooler should be more than enough to cool the MOSFET. It might be the Kapton tape you are using. A while back, I think it was Maty Tinman or was it Jontuin? Whom recommended the ceramic insulator pad. That pad is about 8x better than a 1mil Kapton tape. So you may just need to switch to at least using silicone pad like Keratherm etc.
Welcome aboard, Carlos! Your DX was the very first discrete Class AB that I built what seems like ages ago but maybe 2 years and 32 amps later now. It’s still a great amp.
I still have my original zero prototype on veroboard for the Alpha as well as the first Alpha 20 on PCB. The mod I made was on the larger B.B. PCB. It’s easy to go back as I left the parts in place but disconnected one leg.
the fan is the same size as the heat sink and i have two fans, one for each side ( one for every two heatsinks), but the problem is not the fans, the problem is small box and no room for air circulation, as you read in my previous post when i remove the top the temperature stays at 90 to 100F which is good enough in Texas heat.I think your fan must be the same size than your copper heatsink as tall and wide. Or you must make some adapter so all the air force to go true the heatsink. Like these, see the plastic at Dell. I have two Dell computers. Dell CPU Heatsink Optiplex GX620 330 740 745 755 E521 J9761 D9729 Mini-Tower OEM | eBay You have not much room there so the 2 fan option may be better. Two fans next to each other. That one fan like how is in the picture is not enough. Just an advise
Especially summer time if you run the amp several hours it will get fried. I forget to mention your fan must take fresh air from outside of the enclosure!
i think my solution is either a bigger box and/or a box with at least aluminum bottom plate so the heat can be spread out and cooled.
Thanks
A.
Thanks Danny for reminding me and sorry I forgot it was you. Those pads do indeed work marvelously well on my Alpha BB. They do require a heatsink compound paste though so not as eat as paste-free silicone. But the results are quite good. With my Alpha BB and the CPU coolers running on 10% minimum speed, the aluminum clamp bar on the MOSFET never goes above 38C and the heatsink temp is 27C so that air coming air is hardly even warm.
Got my ALPHA 20 running today - playing tunes with it in my system as I type. Will share listening impressions within a couple of days hopefully.
Some details of the build:
- Running at 1.95mA bias settings (R131 .33 Ohm, R132 2 x 0.33 Ohm in paralllel)
- Offset is 0.1mV and 4mV
- No trimmers used only resistors as per recommended values
Thanks to all who have contributed!
Some details of the build:
- Running at 1.95mA bias settings (R131 .33 Ohm, R132 2 x 0.33 Ohm in paralllel)
- Offset is 0.1mV and 4mV
- No trimmers used only resistors as per recommended values
Thanks to all who have contributed!
Hi X,
No sorry needed.
Yes, those ceramic alumina isolators are very good.
I use them for all my builds.
Those soft paste-free silicone pads are more used in automated processes when it's difficult to add grease,
but us DIYers can do this, taking the best ceramic isolators and add a little grease
Well done Zman !
Didn't you use 3x0.33ohm for R132 ?
See this post for correct resistor values.
for R132 0.165r and R131 0.33r you need for R128 960r
Added 0.11ohm combinations:
Code:
| R131 | R132 | R128 | |
| source | sensor | ccs-fb | bias | speakers
--------|--------|--------|--------|--------|--------------
Alpha20 | 0.33 | 0.12 | 680 | 1.95A | 8R 5-6R dips
Alpha20 | 0.33 | 0.11 | 640 | 1.95A | 8R 5-6R dips
Alpha20 | 0.44 | 0.12 | 510 | 1.46A | 8R 6-7R dips
Alpha20 | 0.44 | 0.11 | 480 | 1.46A | 8R 6-7R dips
Alpha4R | 0.27 | 0.12 | 860 | 2.38A | 4R 3R dips
Alpha4R | 0.27 | 0.11 | 790 | 2.38A | 4R 3R dipsWell I changed to mica, I have a few keraterm but need to find them why is silicone geese better than gel thermal conducting foils?Hi X,
No sorry needed.
Yes, those ceramic alumina isolators are very good.
I use them for all my builds.
Those soft paste-free silicone pads are more used in automated processes when it's difficult to add grease,
but us DIYers can do this, taking the best ceramic isolators and add a little grease
Danny are you building a passive crossover for the bass section cabinet…?
What geese do you use Wakefield witch one?
Thank you all for the kind words!
Danny,
I went with the initial bill of material recommendations for 1.95 A bias - 0.33R for R131, 2 x 0.33R for R132. Understand that you did some further simulations and came up with combinations for other biasing options - thank you and will look into those.
Vunce,
Trying to sneak in some late night listening (actually early morning) - can't crack up the volume too much. My speakers are Carreras by Paul Carmody. Using the Salas DCG3 preamp, Subbu V3 DAC.
Initial impressions are very positive. The separation of voices and instruments is very good. Vocals are clear and have emotion; speech intelligibility is very good, you can easily make out the multiple voices in a chorus - but in no way do the vocals sound forward or shouty. Midrange detail is top notch - listening to a prog track by Virgil Donati and the nuances in the track are coming across nicely:
YouTube
Sound stage is wide and has nice depth. Treble is smooth and detailed. I am finding the bass powerful sounding and articulate. The Carrera sensitivity is 81-82 dB, so not ideal for a 20 watt amplifier, but I am not finding the ALPHA 20W lacking at moderate volumes in any way.
A BIG Thank you to Hugh for sharing this design with the DIY community, and xrk971 and JP for their continued efforts!
Danny,
I went with the initial bill of material recommendations for 1.95 A bias - 0.33R for R131, 2 x 0.33R for R132. Understand that you did some further simulations and came up with combinations for other biasing options - thank you and will look into those.
Vunce,
Trying to sneak in some late night listening (actually early morning) - can't crack up the volume too much. My speakers are Carreras by Paul Carmody. Using the Salas DCG3 preamp, Subbu V3 DAC.
Initial impressions are very positive. The separation of voices and instruments is very good. Vocals are clear and have emotion; speech intelligibility is very good, you can easily make out the multiple voices in a chorus - but in no way do the vocals sound forward or shouty. Midrange detail is top notch - listening to a prog track by Virgil Donati and the nuances in the track are coming across nicely:
YouTube
Sound stage is wide and has nice depth. Treble is smooth and detailed. I am finding the bass powerful sounding and articulate. The Carrera sensitivity is 81-82 dB, so not ideal for a 20 watt amplifier, but I am not finding the ALPHA 20W lacking at moderate volumes in any way.
A BIG Thank you to Hugh for sharing this design with the DIY community, and xrk971 and JP for their continued efforts!