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Aleph-X Compact PCB Group Buy

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#101
PeterLeest said:
Hi Bruno,

I received the boards, very nice, thank you.

In post #65 attached circult, VR101 is 50K, however, I found in another link, the VR is 200 ohm. it could be to typo error.

http://www.kk-pcb.com/alephx.html

For the rectifier board, what is the value of R & C (example C1 & R1) ? Also, do you intend to use MUR30 (MUR3020WT) or MUR1560 for the Aleph-x ?

regards.
Click to expand...

Hi all,

it's true, the value of VR101 is wrong, as it has been pointed out also in This Thread

Here's a copy of my answer to that:
"Hi all,

that is the schematic I posted on the Aleph-X PCB group buy thread.
It is directly taken from KK's Site and I've just redrawn it to create the PCB.
Now, the value of VR101 is wrong (my BIG mistake! :bawling: ), it really must be 200 Ohms, as Grey pointed out. I apologise for this mistake.

As for R103, the value of 360 Ohms is exactly the same as on the original schematic I mentioned above. I do not know if it makes too much of a difference with Grey's original value of 330 Ohms.
With VR101 set to 0, the equivalent value of the parallel of R103 and R104 is 203.85 Ohms with R103=360 and 193.875 with R103=330 Ohms.
With VR101 set to 200 Ohms, the equivalent total resistance is respectively 255.53 and 249.1 Ohms.

I leave to the experts (I'm not one) to judge whether it's preferrable to set R103 to 330 Ohms or to leave it as it is. As far as I know, several Aleph-X have been already built following this schematic and they work..."

Here's the corrected schematic.

Cheers,

Bruno
 

Attachments

#103
PeterLeest said:

For the rectifier board, what is the value of R & C (example C1 & R1) ? Also, do you intend to use MUR30 (MUR3020WT) or MUR1560 for the Aleph-x ?

regards.
Click to expand...

Hi all,

the exact values of R & C on the rectifier boards depend on the diodes used, as well as on the transformer. A commonly used starting point is R=100 Ohm, C=100 nF.

Jim Hagerman (Hagtech) wrote a nice tutorial about "snubbers": Snubbers

As for the diodes, it depends on how much power you want to squeeze from your amp. For a low output power (20-30 W), MUR1560 will be enough, otherwise better use MUR3020WT or equivalent.

Cheers,

Bruno
 
#106
Hi lscangus,

the source resistors are calculated as follows:
R=0.5V/Bias current in each FET.

This is a nice tutorial.

And this spreadsheet will help you calculate all the important parameters of your Aleph-X.

Cheers,

Bruno

P.S.: Lately I've been very busy with professional and private matters, and I had to put aside my hobbies (including this one) a little bit. Please bear with me, I will try to answer all your questions as soon as I can, but please, do not get upset if I happen to disappear for a day or two every now and then...
 
#108
Carondimonio said:
Hi lscangus,

the source resistors are calculated as follows:
R=0.5V/Bias current in each FET.

This is a nice tutorial.

And this spreadsheet will help you calculate all the important parameters of your Aleph-X.

Cheers,

Bruno

P.S.: Lately I've been very busy with professional and private matters, and I had to put aside my hobbies (including this one) a little bit. Please bear with me, I will try to answer all your questions as soon as I can, but please, do not get upset if I happen to disappear for a day or two every now and then...
Click to expand...



What do you mean by 0.5V/bias current?

Angus
 
#113
Hi Angus,

the real supply voltage will probably be a few volts lower when loaded, say 18-19 V. This is the voltage you should take into account when calculating the output power.
As for adjusting the supply voltage to a lower, desired level, you could use for example a resistor (with adequate power dissipation) between two filter capacitors, improving also the ripple. Just bear in mind that you will waste some power...

Cheers,

Bruno
 
#114
Carondimonio said:
Hi Angus,

the real supply voltage will probably be a few volts lower when loaded, say 18-19 V. This is the voltage you should take into account when calculating the output power.
As for adjusting the supply voltage to a lower, desired level, you could use for example a resistor (with adequate power dissipation) between two filter capacitors, improving also the ripple. Just bear in mind that you will waste some power...

Cheers,

Bruno
Click to expand...

thank you very much.

So, what is the VR on the board for?

Angus
 
#118
eapavant said:
vr1 sets the bias of Q3, vr3 sets the bias of Q8, vr2 is used to control absolute dc offset. this page might help some.

http://www.facstaff.bucknell.edu/esantane/movies/aleph-x.html

He has lots of good info all in one place about the aleph-x.
Click to expand...

So, all the components i need is written on the Aleph-X compact PCB, and i do not need any other adjustment to the value of the components except the resistor on the fets board. and that resistor is 0.5/BIAS per fets.

So i am using 8A as my BIAS and i am using 8 fets per channel. so it will be 1A per fets. so.. 0.5/1, = 0.5Ohm. is it right?

I am using about 17V as my rail voltage. so is it better off using IRFQ044?

Angus
 
#120
Update

Hi all,

just a quick update:
the new rectifier boards have already been shipped to me, I should receive them in a couple of days. Once I get them, I will check them thoroughly and then, if everything's OK, I'll forward them to all the members who ordered them/got the wrong ones.

One more thing: I still have some Aleph boards available...

Cheers,

Bruno
 
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