Hello Carpenter, what is the rated output of the Aelph X design you are duplicating into 8 ohms? Does it incorporate 24 output devices 12 + 12?
Controversy aside will it sport a Pass labs Clone creditation in the silkscreening?
Anthony
Controversy aside will it sport a Pass labs Clone creditation in the silkscreening?
Anthony
Pass labs clone?
Hi Anthony,
Our little Aleph X only has 4 power transistors in mono form. If you want to upgrade to a hefty 24 output transistors, then be my guest. Wow, what a monster that would be! I'm quite satisfied with the twenty five watts or so that Grey's current design delivers. For the moment, I'm running Nelson's original 10 watt Zen and it is more than capable of making my ears ring with my JBL 2446 driven paper mache horns. It's hard for me to imagine another amp sounding as sweet as my little Zen.
I was planning to label the pcb with "Aleph X Clone" in the silk screening. Does everyone think this is adequate? In addition, perhaps it should also read "Pass Labs". I'll be more than happy to follow the general consensus. Since we're on the topic of giving credit, I think Grey's name should be present as well. If not for him, this thread and our Aleph X conversations wouldn't exist. We could at least get him to blush a bit.
John Inlow
Hi Anthony,
Our little Aleph X only has 4 power transistors in mono form. If you want to upgrade to a hefty 24 output transistors, then be my guest. Wow, what a monster that would be! I'm quite satisfied with the twenty five watts or so that Grey's current design delivers. For the moment, I'm running Nelson's original 10 watt Zen and it is more than capable of making my ears ring with my JBL 2446 driven paper mache horns. It's hard for me to imagine another amp sounding as sweet as my little Zen.
I was planning to label the pcb with "Aleph X Clone" in the silk screening. Does everyone think this is adequate? In addition, perhaps it should also read "Pass Labs". I'll be more than happy to follow the general consensus. Since we're on the topic of giving credit, I think Grey's name should be present as well. If not for him, this thread and our Aleph X conversations wouldn't exist. We could at least get him to blush a bit.
John Inlow
What about input coupling caps? Nelson recommends them and using in his design. Would be nice to make provision for somebody who would like to use them on a board.
Peter, you little stinker!
I'm never going to get this thing done! Are the input caps truly necessary and if so, where and what value?
John Inlow
I'm never going to get this thing done! Are the input caps truly necessary and if so, where and what value?
John Inlow
Here are some tips from Nelson Pass (I collected out of this thread) regarding the board. It seems like the input caps are not essential but help stabilize the DC offset. But if you using any of Pass' preamps, it's been taken care already, since the outputs are capacitively terminated.
Quoting Mr. Pass:
"I recommend capacitive input coupling for this circuit
unless you can be assured of equal DC impedance
sourcing both inputs, otherwise you get thumps and
higher differential DC offset.
I'm not afraid of the DC input, but there are simply too
many complaints in the field when we don't have them.
For low offset, the circuits wants to see similar DC
source impedances on both + and - inputs.
Now here's a little layout tip for lowest noise in X
amps:
Make all the parts location and wiring identical in
layout AND location between the two halves of the
circuit. That way all the noise pickup is identical between
the two halves of the circuit.
For example, on the XA200 the outputs of the two halves
are found next to each other on both sides of the amplifier,
and the traces going to and fro are identical, one on the
top, the other on the bottom of the board.
The XA200 turned out not to need the compensation
capacitor on the NPN transistor controllling the current
source, nor does it need a lag capacitor on the N channel
gain devices. The remaining compensation cap, 5 pF in
parallel with the feedback loop resistor, is being eliminated
with a board layout revision.
Ref Q4, R15, R16, you simply set the values up so
that you don't blow up the negative output stage, so
I set them fairly high, and it takes a short to ground
to trigger it. In the Aleph X, you don't need them at
all if you can be certain of not shorting to ground, as the
positive current sources will set a limit for you."
End of quote.
Quoting Mr. Pass:
"I recommend capacitive input coupling for this circuit
unless you can be assured of equal DC impedance
sourcing both inputs, otherwise you get thumps and
higher differential DC offset.
I'm not afraid of the DC input, but there are simply too
many complaints in the field when we don't have them.
For low offset, the circuits wants to see similar DC
source impedances on both + and - inputs.
Now here's a little layout tip for lowest noise in X
amps:
Make all the parts location and wiring identical in
layout AND location between the two halves of the
circuit. That way all the noise pickup is identical between
the two halves of the circuit.
For example, on the XA200 the outputs of the two halves
are found next to each other on both sides of the amplifier,
and the traces going to and fro are identical, one on the
top, the other on the bottom of the board.
The XA200 turned out not to need the compensation
capacitor on the NPN transistor controllling the current
source, nor does it need a lag capacitor on the N channel
gain devices. The remaining compensation cap, 5 pF in
parallel with the feedback loop resistor, is being eliminated
with a board layout revision.
Ref Q4, R15, R16, you simply set the values up so
that you don't blow up the negative output stage, so
I set them fairly high, and it takes a short to ground
to trigger it. In the Aleph X, you don't need them at
all if you can be certain of not shorting to ground, as the
positive current sources will set a limit for you."
End of quote.
Hi Peter,
I've checked the schematics on the balanced outputs in my TDM X-over and know for a fact that the outputs are using caps. In my case they appear to be 100 uf/25 volts.
What this boils down to is me not wishing to stop forward momentum in the creation of the pcbs. Should someone require coupling caps, they can stand them up on axis along side the input resistors and solder one end of the resistor to one end of the cap. Of course, if too many diyers want the change, then change is what they'll get. The problem is, I've already started the process of obtaining factory approval for my artwork.
John Inlow
I've checked the schematics on the balanced outputs in my TDM X-over and know for a fact that the outputs are using caps. In my case they appear to be 100 uf/25 volts.
What this boils down to is me not wishing to stop forward momentum in the creation of the pcbs. Should someone require coupling caps, they can stand them up on axis along side the input resistors and solder one end of the resistor to one end of the cap. Of course, if too many diyers want the change, then change is what they'll get. The problem is, I've already started the process of obtaining factory approval for my artwork.
John Inlow
Not yet ready!
What this boils down to is me not wishing to stop forward momentum in the creation of the pcbs.
That's alright we will fix it in the next revision boards that we will design.
Fred
What this boils down to is me not wishing to stop forward momentum in the creation of the pcbs.
That's alright we will fix it in the next revision boards that we will design.
Fred
Peter Daniel said:
Could be for a soft-start, no? In my a-x power supply I run the secondaries into resistors until the capacitor bank voltage comes up to 12V, triggering a normally-open relay to short out the resistors. The one on the Pass Labs PCB doesn't look much like a power relay though.
Could be for ext. switching the amp.
Didn´t Nelson wrote that they switch off only
the amp and not transformer incl. powersupplycaps.
So they want to eliminate formatting current in the cap.(This cause the bad sound when "heating" up the amp). Or so??
😉 Andreas
Didn´t Nelson wrote that they switch off only
the amp and not transformer incl. powersupplycaps.
So they want to eliminate formatting current in the cap.(This cause the bad sound when "heating" up the amp). Or so??
😉 Andreas
I forgot !!
Of course the didn`t Switch all the power with
this relais. But the could use MosFet for doing this. When driving them totally open they show
only little resistance and so little dissipation.
Andreas
Of course the didn`t Switch all the power with
this relais. But the could use MosFet for doing this. When driving them totally open they show
only little resistance and so little dissipation.
Andreas
We've got to start somewhere
Hey Fred,
I want to get the ball rolling. At 12 dollars per board, I don't think the first generation pcb is going to cause anyone to go broke. What is gleaned from the first experience can be passed forward.
Since there's a working prototype out there, why should we not pursue the current concept and begin to enjoy the fruits of our collective labor? If someone discovers a worthy improvement, they may offer the group a redesign and the gratis of their skills. I'm NOT seeking to win a popularity contest, I just want to own and listen to an Aleph X. Beings that all my hard earned dough goes into the home I'm building, ownership of Nelson's handiwork is unlikely to come into my possession. Perhaps you would care to offer the group a better pcb and the follow ups that go with this endeavor.
John Inlow
Hey Fred,
I want to get the ball rolling. At 12 dollars per board, I don't think the first generation pcb is going to cause anyone to go broke. What is gleaned from the first experience can be passed forward.
Since there's a working prototype out there, why should we not pursue the current concept and begin to enjoy the fruits of our collective labor? If someone discovers a worthy improvement, they may offer the group a redesign and the gratis of their skills. I'm NOT seeking to win a popularity contest, I just want to own and listen to an Aleph X. Beings that all my hard earned dough goes into the home I'm building, ownership of Nelson's handiwork is unlikely to come into my possession. Perhaps you would care to offer the group a better pcb and the follow ups that go with this endeavor.
John Inlow
There is a relay on the original XA board. I was wondering what it's used for?
Hmmmm. It seems to be connected the the current source for the front end diff pair.
I suppose it could be related to the power sequencing for🤐...............🤐* with respect to the output stage current sources. Don't worry about it as you know how Nelson sticks all kinds of extra parts in his designs. 
Besides I knew nobody would be irresponsible enough to go offer PCBs to less knowlegable people than themselves without fully understanding the circuit in term of power up and power down transients, short circuit protection, and protection from short circuits from one of the outputs to ground. 
I'm sure they tested it during power up and fault conditions also.
I wouldn't worry about it for one minute.
It probably is not important.
It will be fine,
Fred
*I'm sorry. I guess Grey would have inserted bla, bla, bla here.
Didn't he say something about blowing up his prototype during testing. Grey........... where are you? You were the one who started all this weren't you?
Hmmmm. It seems to be connected the the current source for the front end diff pair.
I suppose it could be related to the power sequencing for🤐...............🤐* with respect to the output stage current sources. Don't worry about it as you know how Nelson sticks all kinds of extra parts in his designs. Besides I knew nobody would be irresponsible enough to go offer PCBs to less knowlegable people than themselves without fully understanding the circuit in term of power up and power down transients, short circuit protection, and protection from short circuits from one of the outputs to ground. I'm sure they tested it during power up and fault conditions also. I wouldn't worry about it for one minute. It probably is not important.It will be fine,
Fred
*I'm sorry. I guess Grey would have inserted bla, bla, bla here.
Didn't he say something about blowing up his prototype during testing. Grey........... where are you? You were the one who started all this weren't you?
I don't think the first generation pcb is going to cause anyone to go broke.
........or buying new drivers for thier speakers in the event of some overlooked failure mode
"Since there's a working prototype out there"
Who's? I can think of a dozen very important questions to ask him/her,
Do you mean Grey's?
Sorry,
Fred
........or buying new drivers for thier speakers in the event of some overlooked failure mode
"Since there's a working prototype out there"
Who's? I can think of a dozen very important questions to ask him/her,
Do you mean Grey's?Sorry,
Fred
What the heck?
I don't recall Grey mentioning any blown speakers........
Fred, are you trolling, or, are you attempting to be a wet blanket? If you're truly concerned, wonderful. You appear to be very cautious, have you had an unhappy experience with an unstable amplifier?
Hey wessol, can you hook you X up to a cheap pair of drivers and describe to us what occurs?
John Inlow
I don't recall Grey mentioning any blown speakers........
Fred, are you trolling, or, are you attempting to be a wet blanket? If you're truly concerned, wonderful. You appear to be very cautious, have you had an unhappy experience with an unstable amplifier?
Hey wessol, can you hook you X up to a cheap pair of drivers and describe to us what occurs?
John Inlow