AX100 100W Aleph-X Monoblocks

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L

Luke

Member
Joined 2001
why so many output fets?

Hi Graeme,

Ive been following this thread for a while and i just reread it all tonight.

If I ever build my aleph-x Ill be following this thread, it looks like youve made it easier for us not so experienced diyers. This project is abit intimidating.

I do have one question, I worked out your outputs are running at about 15watts dissipation. From memory I think Nelson runs things at 25 watts per device. Isnt it easier for the jfet front end to drive less gates?
Do you think using your schematic with 25 volt rails and 12 outputs with 6 amps bias would work ok with your jfet front end.


cheers arthur
 
G

gl

Member
Joined 2003
Hi Arthur,

I'm always happy to hear that what I've done is useful to others.

The 15W number for 540ma of bias through each MOSFET is what I calculate as well. I chose a number that is lower than the typical Nelson number because my heat sink design is not as efficient as the typical PassLabs heat sink design.

I assume that when you say 12 outputs and 6A of bias that you mean a monoblock single channel amp with 12 output MOSFETs and 12 Aleph CCS MOSFET's and 500ma of bias through each transistor? If that's the case then I would say that the dual JFET front end would probably work.

Cheers,
Graeme
 
L

Luke

Member
Joined 2001
The 15W number for 540ma of bias through each MOSFET is what I calculate as well. I chose a number that is lower than the typical Nelson number because my heat sink design is not as efficient as the typical PassLabs heat sink design.
Click to expand...

Ah I thought that might be the case, I luckily have some quite chunky sinks.

I assume that when you say 12 outputs and 6A of bias that you mean a monoblock single channel amp with 12 output MOSFETs and 12 Aleph CCS MOSFET's and 500ma of bias through each transistor? If that's the case then I would say that the dual JFET front end would probably work.
Click to expand...

Yes thats what I mean. I would be tempted to try mosfets first just to realise what the fuss is about with these jfets:)
 
S

space2000

Member
Joined 2008
gl said:
Here is the schematic.

The circuit is essentially the original Aleph-X as shown in the schematic at the beginning of the Aleph-X thread. I have retained the original part numbering. All of the changes made have been discussed by others at various times in various threads. There is nothing new here. The original circuit has simply been reworked to provide an amplifier appropriate to a specific requirement.


The following changes were made:

1) Rail voltages were increased to about 26 - 27V. The CLC type supply uses 68KuF/50V - 1mH - 68KuF/50V filters on each rail. The inductors are Madisound Sledgehammers. Yes they probably are saturating - but they look so cool. There is a great deal of discussion on the Aleph-X thread about sagging transformer secondary voltages under heavy load. I did not experience this. The transformers have a slight soft buzz that's only audible up close.

2) The output device complement was changed to 20 IRFP240's per monoblock or 5 transistors per quadrant and bias was initially set to .5 amps per transistor for a total of 5 amps. These were matched to within .01V in sets of 10.

3) Output source resistors were set to 1 ohm @ 1% to help equalize the dissipation on each output transistor because of the separate heatsink plates. They are 2W Ohmite NI wirewound types chosen because they were one of the better and less expensive units in the catalogs.

4) The CCS sense resistors R2, R3, R42, and R43 were changed to .47 ohms because I had a pile of them. Extra resistors r50, R51, R52, R53, R54, and R55 were added.

5) R16 and R30 were changed to 220K to give a gain of 26dB with a balanced input.

6) Pots V1 and V3 were adjusted and then they and the original 47K resistors were swapped for single fixed values. 82K gives 500ma of bias per device @ 13W of dissipation. 100K gives 540ma per device.

7) R12 and R34 were adjusted for 50% CCS AC current gain. I used the NP method given in the Aleph-X builders thread. First, 475 ohm resistors with 1K pots in series were substituted for R12 and R34. R12 and R34 were then disconnected and with a 100Hz sine wave input the AC voltage across R6 and R41 was measured. R12 and R34 were then reconnected and the pots adjusted so that the AC voltage across R6 and R41 drops to half it's former value. The R12 and R34 pot/resistor networks were removed and measured and fixed resistors substituted. The measured value was 853 ohms and I created this with 634 ohms + 221 ohms which I had on hand, otherwise the closest 1% value is 845 ohms.

When NP describes this process he states that the input level should be set to give 16VRMS across an output load resistor. I couldn't get anywhere near this value without serious clipping. The highest unclipped value I could get was 12V measured with an AC voltmeter. At first I thought something was wrong because this appeared to be way too low. But after I thought about it I figured that with a rail to rail voltage difference of 54V I would start seeing clipping at 48V under ideal circumstances. With the CCS gain at zero I would lose 50% of the current at clipping so the clipping point drops by half. Add to that I was using an unbalanced input so half again. So 12V output at clipping was probably correct.

8) 4.75K MacMillan resistors were added. This resistor value is for me the one big mystery in the circuit. Like it says in the WIKI this value is traded off against the value of the output grounding resistors. Common mode performance is traded off against DC offset performance.

If I had the opportunity to request one breadcrumb from NP it would be the corresponding MacMillan values for the 100 ohm output resistors in the XA series.

9) Several other resistor values were changed in accordance with NP breadcrumbs scattered around in the Aleph-X and Aleph-X builders thread.

10) R21 was deleted.

11) R14, R17, and R31 were increased because of the higher rail voltages.

12) 4.7uF PP input caps and 100K resistors were added to the inputs.

13) 220uF caps were added to each rail on the PCB. A 4.7uF cap was added across D1. These changes were made because similar parts appear in the photos of the XA160 and XA200 that have been posted here or included in various magazine reviews.

14) The rectifier bridges are individual IXYS FRED type soft recovery diodes. There are two bridges in each amp for the two center tapped transformer secondary windings. The outputs of the bridges are paralleled at the first filter cap. This seems to work fine.


Whenever possible individual ground wires were run to a single star ground. There are three ground connections to the PCB: one to each group of input (+ and -) related grounds and a third which collects the power supply connections including the CCS. The RCA jack is insulated from the chassis and its ground pin is connected to pin 3 of the XLR and then pin 3 of the XLR has a separate wire back to the star ground. The star ground is connected to a frame ground (near the IEC inlet) through a CL60. The IEC inlet ground is connected to the frame ground.

I copied the input filtering scheme from the Aleph 60 more or less. Next time I will buy a filtered inlet regardless of what it costs!

I hope that some of this information is helpful to the next builder. If anyone sees anything wrong here please post.

Regards,
Graeme L.
Click to expand...


hi,

i saw your circuit design. i want to follow this circuit as i can arrange easily all mosfets. i have question about input and output connection.

i can see there are in and out have (+) and (_) .

which should be atching to the the CD and speaker?

should i connect Cd into (+ ,GND) and speaker to the (+, GDN)?

my cd player is non inverted.
as i have done aleph-3 there are only + and GND to out and input.

thanks.
michael
 
S

space2000

Member
Joined 2008
gl said:
Here is the schematic.

The circuit is essentially the original Aleph-X as shown in the schematic at the beginning of the Aleph-X thread. I have retained the original part numbering. All of the changes made have been discussed by others at various times in various threads. There is nothing new here. The original circuit has simply been reworked to provide an amplifier appropriate to a specific requirement.


The following changes were made:

1) Rail voltages were increased to about 26 - 27V. The CLC type supply uses 68KuF/50V - 1mH - 68KuF/50V filters on each rail. The inductors are Madisound Sledgehammers. Yes they probably are saturating - but they look so cool. There is a great deal of discussion on the Aleph-X thread about sagging transformer secondary voltages under heavy load. I did not experience this. The transformers have a slight soft buzz that's only audible up close.

2) The output device complement was changed to 20 IRFP240's per monoblock or 5 transistors per quadrant and bias was initially set to .5 amps per transistor for a total of 5 amps. These were matched to within .01V in sets of 10.

3) Output source resistors were set to 1 ohm @ 1% to help equalize the dissipation on each output transistor because of the separate heatsink plates. They are 2W Ohmite NI wirewound types chosen because they were one of the better and less expensive units in the catalogs.

4) The CCS sense resistors R2, R3, R42, and R43 were changed to .47 ohms because I had a pile of them. Extra resistors r50, R51, R52, R53, R54, and R55 were added.

5) R16 and R30 were changed to 220K to give a gain of 26dB with a balanced input.

6) Pots V1 and V3 were adjusted and then they and the original 47K resistors were swapped for single fixed values. 82K gives 500ma of bias per device @ 13W of dissipation. 100K gives 540ma per device.

7) R12 and R34 were adjusted for 50% CCS AC current gain. I used the NP method given in the Aleph-X builders thread. First, 475 ohm resistors with 1K pots in series were substituted for R12 and R34. R12 and R34 were then disconnected and with a 100Hz sine wave input the AC voltage across R6 and R41 was measured. R12 and R34 were then reconnected and the pots adjusted so that the AC voltage across R6 and R41 drops to half it's former value. The R12 and R34 pot/resistor networks were removed and measured and fixed resistors substituted. The measured value was 853 ohms and I created this with 634 ohms + 221 ohms which I had on hand, otherwise the closest 1% value is 845 ohms.

When NP describes this process he states that the input level should be set to give 16VRMS across an output load resistor. I couldn't get anywhere near this value without serious clipping. The highest unclipped value I could get was 12V measured with an AC voltmeter. At first I thought something was wrong because this appeared to be way too low. But after I thought about it I figured that with a rail to rail voltage difference of 54V I would start seeing clipping at 48V under ideal circumstances. With the CCS gain at zero I would lose 50% of the current at clipping so the clipping point drops by half. Add to that I was using an unbalanced input so half again. So 12V output at clipping was probably correct.

8) 4.75K MacMillan resistors were added. This resistor value is for me the one big mystery in the circuit. Like it says in the WIKI this value is traded off against the value of the output grounding resistors. Common mode performance is traded off against DC offset performance.

If I had the opportunity to request one breadcrumb from NP it would be the corresponding MacMillan values for the 100 ohm output resistors in the XA series.

9) Several other resistor values were changed in accordance with NP breadcrumbs scattered around in the Aleph-X and Aleph-X builders thread.

10) R21 was deleted.

11) R14, R17, and R31 were increased because of the higher rail voltages.

12) 4.7uF PP input caps and 100K resistors were added to the inputs.

13) 220uF caps were added to each rail on the PCB. A 4.7uF cap was added across D1. These changes were made because similar parts appear in the photos of the XA160 and XA200 that have been posted here or included in various magazine reviews.

14) The rectifier bridges are individual IXYS FRED type soft recovery diodes. There are two bridges in each amp for the two center tapped transformer secondary windings. The outputs of the bridges are paralleled at the first filter cap. This seems to work fine.


Whenever possible individual ground wires were run to a single star ground. There are three ground connections to the PCB: one to each group of input (+ and -) related grounds and a third which collects the power supply connections including the CCS. The RCA jack is insulated from the chassis and its ground pin is connected to pin 3 of the XLR and then pin 3 of the XLR has a separate wire back to the star ground. The star ground is connected to a frame ground (near the IEC inlet) through a CL60. The IEC inlet ground is connected to the frame ground.

I copied the input filtering scheme from the Aleph 60 more or less. Next time I will buy a filtered inlet regardless of what it costs!

I hope that some of this information is helpful to the next builder. If anyone sees anything wrong here please post.

Regards,
Graeme L.
Click to expand...


hi,

i saw your circuit design. i want to follow this circuit as i can arrange easily all mosfets. i have question about input and output connection.

i can see there are in and out have (+) and (_) .

which should be atching to the the CD and speaker?

should i connect Cd into (+ ,GND) and speaker to the (+, GDN)?

my cd player is non inverted.
as i have done aleph-3 there are only + and GND to out and input.

how about the voltage? can i apply 29vdc on it? is there any things need to be change?

thanks.
michael
 
S

space2000

Member
Joined 2008
Zen Mod said:



considering what type of questions you asking.........

you are not ready for X amp ;

spend two weeks at least in reading related threads ......... go to Papa's site and download EVERY pdf you can .......... and read ;

point is that you learn something building amps , not just to have amp .
Click to expand...


Hi,

*This reminds me, one person says don’t open often any new thread, go to the related thread to ask. now, I got this. *

At first I have to say I am not an electronics engineer. If I am expert, I wouldn’t ask any question here, I would answer questions. This is the reason to ask this kind of stupid question here. May be it’s odd question to you or too cheap question to you. I just asked question and you replied to me go and read “this and that” you are not ready for X amp”. I am really very much disappointed about your writing.
 
T

tryonziess

Member
Joined 2007
Space2000, The Aleph circuit and Aleph-X circuits are not your standard run of the mill designs. Though the Aleph is user friendly the Aleph-X circuit can be quite difficult to tame.
The question you asked concerning the hookups has to do with balanced and single ended amplifiers.
It would save you much money and headache to take Zen Mods suggestion to heart.
I am by no means expert in this field and started out with a few chip amp builds and progressed to some nice Leach amps. I will build the A-75 design before tackling the aleph-X.
Some of the very much experienced builders on this forum have had good luck with the X but they know how to tweek the little things and know when things are not right.
Good Luck Tad
 
Magura

Magura

Member
Joined 2003
class-a-labs.com
space2000 said:



Hi,

*This reminds me, one person says don’t open often any new thread, go to the related thread to ask. now, I got this. *
Click to expand...


This person, whom happens to be me, wrote:

"Once you've read the ENTIRE AX thread, AND the WIKI, come back and ask questions, and we will all gladly help you out"


Now considering I gave you that advice yesterday, you either read very fast, or haven't done diddly ?

Zen Mod gave you a sound piece of advice as well, so no reason to be disappointed in him.
Considering the questions you ask, I'd say he is pretty much spot on.

There are more half built AX projects laying around that you'd care to know of, all leaving somebody between 1500 and 2000 usd poorer and pretty disappointed.
These are mostly a product of beginners, whom thinks they can deal with taking on a difficult project.......
Just here in Denmark, I guess half of the AX amps attempted (if not more than that), ended up like that.
I have spent some time getting some of them up and running, and some has been abandoned by the builder.

Magura :)
 
macka

macka

Member
Joined 2001
Space 2000

Dont be offended by these posts.

This project is not difficult to get going.

Pm me if you have any specific questions

I might even mail you some Jfets to try.

I have a nice stash of 2SJ109 and 2SJ074 but not for people with big egos and bad attitudes...they are bad for diy audio.

A number of people have had issues running single ended unbalance input (even expierenced people)

You need to capacitively couple the +- inputs and ground the - input otherwise there will be issues with dc offset.

I would suggest looking at Chef's UGS power project which is probably a better amplifier and has more stable bias and offset characteristics.

Ian
 
S

space2000

Member
Joined 2008
Hi,

Thanks to all.


friends, i am not here to search for any offend or to write any odd language. here many firends are visiting like me. they are just hobbiest and some even never touched soldering iron but they all like to see amp and still trying to make if they can in there life time. i feel all of you are very much healpful as i got help form somewhere arround here, like "Dx carlos" helps me lots, Thanks to carlos. asking question is not offend dear friends as long it is not personal.

enough to write this....i am really soory for this cons...

About Aleph-X, i was misunderstood about the input and output when i read the thread. i should be able to make aleph-x....soon i will show you. only problem is now input and output, how i am going to connect or is there need any preamp to drive - + Gnd?


thank you for your help.
michael
 
R

RoboMan

Member
Joined 2006
Hi Michael,

I think most people in this forum are willing to help. Please don't have hard feelings.

Frankly speaking, I do agree with Zen Mod that you are not ready to build the Aleph-X yet (as you said "I am ready ..." in another thread). Here are my suggestions:

1. I would say Aleph-X is a relatively complicated project. May be it is not too complicated to build if you use ready-made PCB etc., but it takes a lot of work to make it work properly. You also need to know thoroughly how each part works in case you need to do any trouble-shooting.

2. Aleph-X is based on Aleph circuit. It is like putting two Aleph circuits to form one. The output is connected to the outputs of the two circuits (no ground for the speaker). So I would suggest you to study or even build an Aleph before starting with Aleph-X.

3. All Aleph versions are very similar and that is the beauty of the design. If you increase the power supply voltages and increase the number of output MOSFET, you can get higher output power, provided you have enough heatsink and everything are within the limit of the parts. There are Excel spreadsheets in the forum to let you find out how much output under what conditions for both Aleph and Aleph-X. You will be thrilled by the current required by Aleph-X.

4. For all Aleph amps, there is a special circuit called "Aleph Current Source" patented by Mr. Nelson Pass. (See Zen-ver2.pdf from http://www.passdiy.com/articles.htm and other posting in this forum.) This circuit improves the efficiency of the amp but will introduce huge distortion if over set. I would suggest to disconnect this part until you are sure everything works properly.

In short, I would suggest you study all postings about Aleph-5 and Aleph-2 before going to build Aleph-X.

Hope this will help, no offence!
 
S

space2000

Member
Joined 2008
hi,

Thanks for your valuable information. first i made aleph-3. it was working so well, i even can't believe my self. i adjusted very well as i have seen no distortion at all. i was operating on my 30vdc, 10 amp. heat was well control as i made the heat sink. i was surprised with the sound quality. actually before i made aleph-3, i was thinking for aleph-x. i realized it is bit critical so i made first aleph 3 as some one recomended, many Thanks to them, it was for learning about aleph amp too. Then eventually i was thinking i should try aleph-x too. They are quite similar.

Aleph-X? Today i have just made it. now still in checking if there is any error. it is prototype circuit just to see how its works. when i powered, it was working completly, i even played song from dvd, but there are some distortion sound coming as it is still not yet check for errors, just born new baby...ha...ha..i just used single two pcs mosfets each side. i matched all of them as it should be.

if you have any suggestion pls write. i love to listen your comments.

Picture Note: this is only for testing purpose so its msy...i just worked and took pic of it. it is original pic no fake at all.

best regards
michael
 
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