I played the Aleph X on scary soundlevels and now things are clearly better. The JLH sounded restrained (I have only 85 db speakers) and the Aleph X has much more power without loss of quality.
Grataku, I don't want to switch back to my JLH but for me it's important to be critical about improvements. Some audiophiles hear always improvements even if it's not an improvement at all.
Macka, I totally agree!! It's a JLH on steroids.
Grataku, I don't want to switch back to my JLH but for me it's important to be critical about improvements. Some audiophiles hear always improvements even if it's not an improvement at all.
Macka, I totally agree!! It's a JLH on steroids.
EI Transformer for Aleph-X
I have a chance to purchase 2- 12.5 volt 8 amp tramsformers for cheap. Will 8 amps be enough for the 4.5 amp current draw of the A-X?
Will an EI trans. need slow blow or regular fuses?
I want to use one trans. for each channel.
thanks
Vince
I have a chance to purchase 2- 12.5 volt 8 amp tramsformers for cheap. Will 8 amps be enough for the 4.5 amp current draw of the A-X?
Will an EI trans. need slow blow or regular fuses?
I want to use one trans. for each channel.
thanks
Vince
I think that 200VA (12.5 *8 *2) is possible, but the rails will be to low if you'r planning to use a CRC type of filter in the powersupply.
macka said:
Hi,
That's the same impression I have for the JLH for ESL version compare with the JLH 1996 version.
Even though I was in the group buy for the X Aleph PCB I feel that I am still too green to build the X now. I am still waiting for all the dust to settle first and have a list of proper direction/instruction to follow. Right now it is still too many options, to many variations thus too confusing.
But for the JLH ESL it is very simple for me to understand and follow it.
Best Regards,
Chris
VR Adjustment/ Proper Setup
How do I adjust VR1,2 &3? Do I start with a zero setting or midway setting to be safe?
If I'm using a volt meter, am I looking for off-set at the output or am I setting the current draw?
V1 and 3 work in tandum, but what does V2 do?
Any help?
Thanks,
Vince
How do I adjust VR1,2 &3? Do I start with a zero setting or midway setting to be safe?
If I'm using a volt meter, am I looking for off-set at the output or am I setting the current draw?
V1 and 3 work in tandum, but what does V2 do?
Any help?Thanks,
Vince
I did the following:
Measure the voltage drop over R5 and R40 and adjust these values with vr1 and vr2. (for the std version you're looking voor 0.5 volt)
To adjust the absolute off-set measure between +out and ground and reajust vr3 to get 0 volt.
mvg,
Taco
Measure the voltage drop over R5 and R40 and adjust these values with vr1 and vr2. (for the std version you're looking voor 0.5 volt)
To adjust the absolute off-set measure between +out and ground and reajust vr3 to get 0 volt.
mvg,
Taco
Granted, I don't have a schematic here at my elbow, but I seem to recall drawing things such that V1 & V3 were the pots that controlled the output bias. V2, I think, was the pot for the input differential current source.
Strictly speaking, the current source pot is the only one that's necessary. Set it such that the output measures more-or-less 0V to ground with no signal. This is your absolute DC offset. Small amounts of offset won't hurt anything, since the speaker won't see it. Large amounts of offset still won't hurt anything, but will begin to cut into available power. This is pretty much the same thing that Taco said.
The pots for the two halves of the output can be used to run the bias up and down, making the amp run hotter or cooler. It will effect sound quality. This also gives you the option of having more bias current on hand in order to handle a lower impedance load. These pots will also allow you to adjust out minor amounts of relative DC offset (i.e. measured from one ouput terminal to the other, as opposed to measuring to ground). If you're using well-matched sets of devices (match across the amp--current source to current source and output to output), you can skip the output pots entirely if it makes you happy. I just put 'em in there to guild the lily.
Nominal voltage drop across the Source resistors is .5V, but there's plenty of leeway. Just make sure that you set them to the same bias on both sides.
Although some people get all hot and bothered at the thought of toroids, some damned fine sounding amps have been built with EI transformers. The type of transformer isn't going to influence what kind of fuse you use. That's going to be more a question of how much capacitance you've got in your power supply. The turn-on surge is the booger. The fuse needs to last long enough to charge the caps without blowing. Given that the Aleph-X is a pretty constant load once it's running, you're home free once the amp turns on successfully. Any significant amount of current over idle indicates a problem and should pop the fuse.
Grey
Strictly speaking, the current source pot is the only one that's necessary. Set it such that the output measures more-or-less 0V to ground with no signal. This is your absolute DC offset. Small amounts of offset won't hurt anything, since the speaker won't see it. Large amounts of offset still won't hurt anything, but will begin to cut into available power. This is pretty much the same thing that Taco said.
The pots for the two halves of the output can be used to run the bias up and down, making the amp run hotter or cooler. It will effect sound quality. This also gives you the option of having more bias current on hand in order to handle a lower impedance load. These pots will also allow you to adjust out minor amounts of relative DC offset (i.e. measured from one ouput terminal to the other, as opposed to measuring to ground). If you're using well-matched sets of devices (match across the amp--current source to current source and output to output), you can skip the output pots entirely if it makes you happy. I just put 'em in there to guild the lily.
Nominal voltage drop across the Source resistors is .5V, but there's plenty of leeway. Just make sure that you set them to the same bias on both sides.
Although some people get all hot and bothered at the thought of toroids, some damned fine sounding amps have been built with EI transformers. The type of transformer isn't going to influence what kind of fuse you use. That's going to be more a question of how much capacitance you've got in your power supply. The turn-on surge is the booger. The fuse needs to last long enough to charge the caps without blowing. Given that the Aleph-X is a pretty constant load once it's running, you're home free once the amp turns on successfully. Any significant amount of current over idle indicates a problem and should pop the fuse.
Grey
GRollins said:
I have seen very different source resistors voltages in the Aleph series, and would like to know how they can be choosen, since the voltage drop seems to influence both maximum current deliverable from the current source and current gain: am I right?
Cheers
Andrea
Nuthin' to it...
Assume (though it's not cast in stone) a .5V drop across the resistor. The rest is just Ohm's Law:
.5/I=R
Where I is your target current.
Just don't kill your MOSFETs. Keep one eye on the SOA chart and leave plenty of elbow room.
Grey
Assume (though it's not cast in stone) a .5V drop across the resistor. The rest is just Ohm's Law:
.5/I=R
Where I is your target current.
Just don't kill your MOSFETs. Keep one eye on the SOA chart and leave plenty of elbow room.
Grey
Thank you for reminding me Ohm's law 😉 , hovever I wanted to know if 0.5V is better than 0.25 or 0.35... surely we can't exceed 0.65V because the BJT would jump right in, is the higher value chosen to give a bit more of local feedback thus stabilizing the DC current?
Cheers
Andrea
Cheers
Andrea
Andrea,
If the NPN (Q3) doesn't turn on, then nothing's going to happen. Keep in mind that the base is getting some of its go-juice from the positive rail via V1/R11, etc., not just the voltage drop across R5. This tends to tilt the balance a bit away from just the pure voltage sensed at the Source resistor (R5). (Part nomenclature from my original schematic, left hand side.)
If you try to increase the Vbe of the NPN above .65V then it will tend to squeeze the output MOSFET (Q1) until the current drops back down and a nice balance is achieved, with Q3 riding herd on Q1.
The nominal .5V across the Source resistors is just a convenient value. Want to set it to .4V? Be my guest. It's not magic. The sum of V1 and R11 will determine what the voltage actually turns out to be. Without them, it would set to the Vbe of Q3. When I first started putting the prototype together, I kept it pretty starved for current because I was using smallish heatsinks and couldn't afford the heat. Given that I was using something like 20 ohm load resistors for testing purposes, I didn't need the full boat current capability anyway.
There's plenty of latitude in the selection of the Source resistors. That, coupled with the other reistors hanging off of the NPN base (and pots, in the case of the Aleph-X) allow a lot of adjustment. You can go to infinity with V1/R11 and their mirror images on the other side if you want. Bias current will increase, the Vbe across the NPN will settle at .65V or so, and the amp will lean more towards its cousin, the Zen. Call it a Xen, if you like. X-ed Zens would be a nice project. Somewhat less efficient, but still a worthy idea.
Grey
If the NPN (Q3) doesn't turn on, then nothing's going to happen. Keep in mind that the base is getting some of its go-juice from the positive rail via V1/R11, etc., not just the voltage drop across R5. This tends to tilt the balance a bit away from just the pure voltage sensed at the Source resistor (R5). (Part nomenclature from my original schematic, left hand side.)
If you try to increase the Vbe of the NPN above .65V then it will tend to squeeze the output MOSFET (Q1) until the current drops back down and a nice balance is achieved, with Q3 riding herd on Q1.
The nominal .5V across the Source resistors is just a convenient value. Want to set it to .4V? Be my guest. It's not magic. The sum of V1 and R11 will determine what the voltage actually turns out to be. Without them, it would set to the Vbe of Q3. When I first started putting the prototype together, I kept it pretty starved for current because I was using smallish heatsinks and couldn't afford the heat. Given that I was using something like 20 ohm load resistors for testing purposes, I didn't need the full boat current capability anyway.
There's plenty of latitude in the selection of the Source resistors. That, coupled with the other reistors hanging off of the NPN base (and pots, in the case of the Aleph-X) allow a lot of adjustment. You can go to infinity with V1/R11 and their mirror images on the other side if you want. Bias current will increase, the Vbe across the NPN will settle at .65V or so, and the amp will lean more towards its cousin, the Zen. Call it a Xen, if you like. X-ed Zens would be a nice project. Somewhat less efficient, but still a worthy idea.
Grey
I believe we will be referring to that as ZV6. 😎GRollins said:
By the way, what shall we do to celebrate hitting 300,000?
Nelson Pass said:
Don't speak too fast, Nelson.
If you announce that ZV6 will be out for the 300 000 views, the 3 000 views to go could be done faster that you think, and also faster that you could post the article 😀
Grey, you are right, the voltage across the source resistors is just one of the characters that play in defining the BJT's point of work, hopefully it's not the main one 
In my next channel I'll use higher values resistors, just to see what changes if I get closer to 0.5V..
Cheers
Andrea
In my next channel I'll use higher values resistors, just to see what changes if I get closer to 0.5V..
Cheers
Andrea
The Zen Variations series was the result of prompting by Edjam said:
Dell of AudioXpress, who wanted to bundle the articles into
a book. He has been waiting patiently for nearly 2 years, and
we are trying to have it by Spring.
Of course anyone who wants to download the pdf's on to a
CD is welcome as far as I'm concerned.
My only problem will be 2 more projects that would top the
ZV6, which promises to be the jewel in the crown.
Don't forget your old articles too!
Nelson, I'd like to ask that you include not just your Zen articles, but everything you've written. DIY Opamps, Single ended Class A, Cascode Amp Design, the A40, the A75, Construct a Class A Amplifier, Citation 12, etc...
EVERYTHING! It's all so valuble and chock full of useful information that even the owner's/service manuals for the Alephs or the X series all have nuggets of wisdom that cleared up years of lies perpetuated by the audio industry.
Throw in the kitchen sink, Master. I'll buy it.
-Erik.
Nelson Pass said:
Nelson, I'd like to ask that you include not just your Zen articles, but everything you've written. DIY Opamps, Single ended Class A, Cascode Amp Design, the A40, the A75, Construct a Class A Amplifier, Citation 12, etc...
EVERYTHING! It's all so valuble and chock full of useful information that even the owner's/service manuals for the Alephs or the X series all have nuggets of wisdom that cleared up years of lies perpetuated by the audio industry.
Throw in the kitchen sink, Master. I'll buy it.
-Erik.