panos29 said:
Don’t be disappointed about the response, this happens to anyone now and then.
I did have a look at your results and part of the answer is probably given here:
http://www.diyaudio.com/forums/showthread.php?postid=179872#post179872.
The measurements were done with a resistive load, but I’ll try to add some capacitance.
Don’t you think 1-2uF is a bit much?
Some recent experiments learned that adjusting the bias to a certain point is quite important.( in my amp)
Here’s what I did:
I connected a sinewave 1Khz. Because my amp is not clipping symmetrically, the upper part of the waves clips sooner than the lower part, I increased the power till the lower part was just not clipping. Of course the upper part was already flat.
Then I started trimming the bias on both sides till both halves didn’t clip anymore.
The funny part is that there is only one point were the bias is optimal. Increasing it results again in clipping on the upper part. Also the lower part can be pushed much further without showing a flat clip line. It rather shows distortion, but clips much later, no matter what bias point I set.
It’s quite a hassle to remount a pot in place of the active current source regulator but it will have to be done.
All this is said by Grataku in earlier posts, but sometimes it takes a long time and much reading to fully understand what really happens in practice.
Measuring the power just before clipping gives 30.6Vac RMS with an 8ohm resistive (16 X 8R2 50W wirewounds in series-parallell) load: 117WRMS. It could be a bit inductive after all.
Hugo – back to the bench…
Netlist said:Just to let you now...in case you get bored.
The battery has arrived
/Hugo
I noticed that Madrigal is using similar caps in their most recent amps.
http://www.marklevinson.com/image_library/index.asp?categoryID=6&productID=7
http://madrigal.harman.com/image_library/marklevinson/383PS_lo.jpg
Peter Daniel said:
Can’t be bad then. Those amps look awesome. Can’t get enough of the pictures…
Edwin Dorre said:looks great to me....
Well then, the new PSU is up and working.
The hum is (almost) completely gone. When listening very close to the speaker, I can hear a very tiny amount of hum.
Measurements reveal 1.8mV AC. I definitely can live with this.
The voltage is now +/-30V. The AC meters on the variac show 1.9A on 227V.
Thanks again guys.
/Hugo
Peter
Before there were 4 caps, each 68.000µF. Total: 272.000µF
Now I have 6, each 47.000µF. Total 282.000µF
Making it a CRCRC filter does the main improvement.
The R's do the trick I believe.
Over the first caps I measure 355mV AC.
The second shows 81mV AC and the third 25mV AC. This results in 1.8mV differential AC at the outputs.
The sound, to me, is the same as before. There's no way to go back to the old setup to do an A/B test.
/Hugo
Before there were 4 caps, each 68.000µF. Total: 272.000µF
Now I have 6, each 47.000µF. Total 282.000µF
Making it a CRCRC filter does the main improvement.
The R's do the trick I believe.
Over the first caps I measure 355mV AC.
The second shows 81mV AC and the third 25mV AC. This results in 1.8mV differential AC at the outputs.
The sound, to me, is the same as before. There's no way to go back to the old setup to do an A/B test.
/Hugo
Those are stand offs used to connect another small board with 2 fuses http://madrigal.harman.com/image_library/marklevinson/383OH_lo.jpg
In time I received some request by mail to post a schematic of my amp.
I’m pretty well satisfied now with the trimming results so here we go.
Anyone, feel free to add more reply or recommendations.
The power supply schematic is here:
http://www.diyaudio.com/forums/showthread.php?postid=194297#post194297
Thanks again to all for the large interest and great amount of tips all over the place.
/Hugo
I’m pretty well satisfied now with the trimming results so here we go.
Anyone, feel free to add more reply or recommendations.
The power supply schematic is here:
http://www.diyaudio.com/forums/showthread.php?postid=194297#post194297
Thanks again to all for the large interest and great amount of tips all over the place.
/Hugo
Attachments
How difficult is it to solder onto the solid copper bar? Did you have
to set up some kind of jig to hold the bar in place while you
soldered on the components? Point to point looks so nice! I'm
going to have to give it a try soon.
Another old question, but do the resistors in the power supply
heat up the capacitors too much? or do you have something
between the caps and the where they're mounted?
Is that the star ground in the upper right hand corner of the picture?
Great job! inspirational
moe29
to set up some kind of jig to hold the bar in place while you
soldered on the components? Point to point looks so nice! I'm
going to have to give it a try soon.
Another old question, but do the resistors in the power supply
heat up the capacitors too much? or do you have something
between the caps and the where they're mounted?
Is that the star ground in the upper right hand corner of the picture?
Great job! inspirational
moe29
Thank you Moe
When you look at the lower copper wire you can see that I wrapped the wires from the big resistors around it.
They then held them in place very easily.
The upper and mid bar was not much of a problem too.
I plied the legs of the mosfets first and let the bar rest on those
plied feet.
Soldering is not a problem at all.
Just have enough patience too let the bars heat up.
Don't be afraid to heat things up, they will have to get used to it anyway
About the PSU R's:
They are 0.1ohm so they hardly dissipate anything.
The alu plate is slightly warm.
There is nothing between the plate and the caps but they stay
cool enough. I guess around 30°C.
Here's another picture of the star ground. The centre tap of the transformer goes directly to the centre point of the caps.
From there a big wire goes to the small signal board.
/Hugo
When you look at the lower copper wire you can see that I wrapped the wires from the big resistors around it.
They then held them in place very easily.
The upper and mid bar was not much of a problem too.
I plied the legs of the mosfets first and let the bar rest on those
plied feet.
Soldering is not a problem at all.
Just have enough patience too let the bars heat up.
Don't be afraid to heat things up, they will have to get used to it anyway
About the PSU R's:
They are 0.1ohm so they hardly dissipate anything.
The alu plate is slightly warm.
There is nothing between the plate and the caps but they stay
cool enough. I guess around 30°C.
Here's another picture of the star ground. The centre tap of the transformer goes directly to the centre point of the caps.
From there a big wire goes to the small signal board.
/Hugo
Attachments
I can’t wait to see more AlephX’s arise.
If with picture we can inspire more people to build and show their work I would be happy to post a few more.
What about an AlephX gallery?
Like the PassDiy galleries?
I was thinking about it the other day but as I don’t know how to set up a site we maybe have to wait for someone to do this.
/Hugo
If with picture we can inspire more people to build and show their work I would be happy to post a few more.
What about an AlephX gallery?
Like the PassDiy galleries?
I was thinking about it the other day but as I don’t know how to set up a site we maybe have to wait for someone to do this.
/Hugo
Thanks Hugo!
i'm finishing my Aleph 2's and the pictures of your power supply
have given me some ideas on how to finish mine.
I just got a pair of the Aleph-X boards a few weeks a go, so i
guess that project will be done in the near future. I think with
the projects i've built so far i have some experience to tackle the
AX.
m.
i'm finishing my Aleph 2's and the pictures of your power supply
have given me some ideas on how to finish mine.
I just got a pair of the Aleph-X boards a few weeks a go, so i
guess that project will be done in the near future. I think with
the projects i've built so far i have some experience to tackle the
AX.
m.
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