Aleph X for high impedance speakers?
I recently bought a set of AKG K1000 headpspeakers. I like them enough to keep them. They seem to be very unforgiving to source quality and amp quality. Right now I'm driving them with an Adcom GFA555 and a pro Sony converter. This combo sounds pretty good, but I was wondering if I could adapt two of my Aleph X boards to drive the K1000. The impedance of the K1000 is in the 120 Ohm range. I would like to get about 20-30W output capability in this load. The spreadsheet for calculation of the power goes only to 12 Ohm. I did hack it to allow me to input 120 Ohm as impedance. I was wondering if the results will be sound. I'm coming up with about 45V for rail voltage and 0.6A - 1A bias for 20W-30W output. Dissipation in the 13W-18W range per each of 4 Fets. Would it work, or is the spreadsheet not reliable for higher impedance loads? Is the circuit optimal for those kinds of voltages/bias?
Thanks
I recently bought a set of AKG K1000 headpspeakers. I like them enough to keep them. They seem to be very unforgiving to source quality and amp quality. Right now I'm driving them with an Adcom GFA555 and a pro Sony converter. This combo sounds pretty good, but I was wondering if I could adapt two of my Aleph X boards to drive the K1000. The impedance of the K1000 is in the 120 Ohm range. I would like to get about 20-30W output capability in this load. The spreadsheet for calculation of the power goes only to 12 Ohm. I did hack it to allow me to input 120 Ohm as impedance. I was wondering if the results will be sound. I'm coming up with about 45V for rail voltage and 0.6A - 1A bias for 20W-30W output. Dissipation in the 13W-18W range per each of 4 Fets. Would it work, or is the spreadsheet not reliable for higher impedance loads? Is the circuit optimal for those kinds of voltages/bias?
Thanks
One resistor volume control ?
Another stupid question from a novice of analogue electronics :
Assuming that I have balanced inputs, would a variable resistor of say 10R to 1M connected across the cathodes of D3 & D5 on Grey's schematics be effective as a volume control ?
If not, could one of the experts kindly explain.
And if yes, any drawbacks ?
Many thanks.
Patrick
Another stupid question from a novice of analogue electronics :
Assuming that I have balanced inputs, would a variable resistor of say 10R to 1M connected across the cathodes of D3 & D5 on Grey's schematics be effective as a volume control ?
If not, could one of the experts kindly explain.
And if yes, any drawbacks ?
Many thanks.
Patrick
tomchaoda said:
You might want to take a look at this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=37262
/Hugo
Trying to run the Zener via an opamp?
Hmmm.
Why?
A servo for this circuit need not be complicated. I whipped one up using (as I recall) two MPSA18s instead of an opamp. I never bothered posting it in the Aleph-X thread as no one seemed very interested. I believe someone else did post one, though. It should be fairly early in the thread. If you can't find it, I'll see if I can find a hardcopy of my schematic for the servo. After losing my hard drive this past winter, I'm having trouble finding some things.
Grey
Hmmm.
Why?
A servo for this circuit need not be complicated. I whipped one up using (as I recall) two MPSA18s instead of an opamp. I never bothered posting it in the Aleph-X thread as no one seemed very interested. I believe someone else did post one, though. It should be fairly early in the thread. If you can't find it, I'll see if I can find a hardcopy of my schematic for the servo. After losing my hard drive this past winter, I'm having trouble finding some things.
Grey
servo
Chad had disclosed the servo with 2 transistors without detail
http://www.diyaudio.com/forums/showthread.php?postid=378520#post378520
Anyone can provide the details
thanks
Chad had disclosed the servo with 2 transistors without detail
http://www.diyaudio.com/forums/showthread.php?postid=378520#post378520
Anyone can provide the details
thanks
The servo will only serve to correct the DC offset between output and ground. This is not at all important because it is the same on both sides of the speaker (just like in the SOZ) and doesn't really have any effect on things unless it's really extreme. The worst you'll face is that one rail will clip before the other.
If you're talking about DC offset from one speaker terminal to the other, then a servo will do nothing to help this problem. There are several possible causes. If you disconnect the inputs and the DC offset is still there, then it's possible that the MOSFETs in the input differential aren't matched closely enough. If all is well until you hook up a source, then you're facing another possibility--leakage of DC from the source (I just had this happen to me--thought it was the amp going nuts, but in reality it was a piece of test equipment belonging to a friend of mine that was passing DC). Small amounts of kind of DC offset can be cured by using the pots I added to the Aleph current sources, but it's best to actually track down the problem and cure it.
Make sure that the amp is adjusted properly, then figure out which kind of DC offset you've got. The next step is to see if it's coming from the source or the amp itself. With a little bit of detective work, you can limit the number of things that might be causing the DC and set out to fix it.
Grey
If you're talking about DC offset from one speaker terminal to the other, then a servo will do nothing to help this problem. There are several possible causes. If you disconnect the inputs and the DC offset is still there, then it's possible that the MOSFETs in the input differential aren't matched closely enough. If all is well until you hook up a source, then you're facing another possibility--leakage of DC from the source (I just had this happen to me--thought it was the amp going nuts, but in reality it was a piece of test equipment belonging to a friend of mine that was passing DC). Small amounts of kind of DC offset can be cured by using the pots I added to the Aleph current sources, but it's best to actually track down the problem and cure it.
Make sure that the amp is adjusted properly, then figure out which kind of DC offset you've got. The next step is to see if it's coming from the source or the amp itself. With a little bit of detective work, you can limit the number of things that might be causing the DC and set out to fix it.
Grey
dc servo
thr differential dc op offset are only 7 mv and 20mv for 2 channels.
only absolute o/p offset varied from hot to cold (4v to 0v)
i am worry for 0.4v offset at the ip . So i want to install the dc servo.i want direct coupling with my preamp.
As i am not an electronic enginner , i dare not to experiment too
much,
so i ask asistance here
Thanks alot
thr differential dc op offset are only 7 mv and 20mv for 2 channels.
only absolute o/p offset varied from hot to cold (4v to 0v)
i am worry for 0.4v offset at the ip . So i want to install the dc servo.i want direct coupling with my preamp.
As i am not an electronic enginner , i dare not to experiment too
much,
so i ask asistance here
Thanks alot
I'm a bit out of this
Dear All,
I have only just found the www.passdiy.com site ... but there is no mention of Aleph-Anything as a DIY there. The only mention I see of the Aleph series is as defunct fully manufactured products at the www.pass.com site.
What is the situation please? Are Alephs still available as kits and what exactly were they?
I actually was thinking of putting together a Zen IV (Penultimate Zen) after I had priced out the pieces - or rather two of them (4 channels) so I can make my own speakers with an active crossover.
Anyways, all help gratefully received,
George.
Dear All,
I have only just found the www.passdiy.com site ... but there is no mention of Aleph-Anything as a DIY there. The only mention I see of the Aleph series is as defunct fully manufactured products at the www.pass.com site.
What is the situation please? Are Alephs still available as kits and what exactly were they?
I actually was thinking of putting together a Zen IV (Penultimate Zen) after I had priced out the pieces - or rather two of them (4 channels) so I can make my own speakers with an active crossover.
Anyways, all help gratefully received,
George.
Arthur,
If your DC offset at the output is below 100mV, you have nothing to worry about. 4V absolute offset when the amp is cold isn't going to hurt anything since the speaker doesn't see it.
DC offset at the input (I'm assuming that's what you mean by "ip") is much more easily dealt with by using DC blocking caps if it's a problem.
George,
The Aleph was a production amplifier which was discontinued a few years ago. The X series is currently in production. The two concepts can be used together, which leads to the production XA series, and a humble little project I put together a while back. Don't confuse the Aleph-X project with the real thing, but it works and that's a start.
The Alephs were never available as kits. The schematics are available at www.passlabs.com, but you'll need to do a bit of work to put them together. Not that it can't be done, mind you. I've got two pairs of Aleph 2s, a Mini-A (with boards that MikeW was kind enough to run up--my prototype was point-to-point), not to mention the odd Aleph-X and a few other little experimental knick-knacks that I play with when I have time.
The Zens are fine project amps, and better documented than the Alephs in the official sense. For unofficial documentation on the Alephs, poke around here.
The X amps are doable, and I've taken a few steps in that direction, but it's not a high priority with me at the moment. The best source for help on that topology is Petter's X-100 thread.
Grey
If your DC offset at the output is below 100mV, you have nothing to worry about. 4V absolute offset when the amp is cold isn't going to hurt anything since the speaker doesn't see it.
DC offset at the input (I'm assuming that's what you mean by "ip") is much more easily dealt with by using DC blocking caps if it's a problem.
George,
The Aleph was a production amplifier which was discontinued a few years ago. The X series is currently in production. The two concepts can be used together, which leads to the production XA series, and a humble little project I put together a while back. Don't confuse the Aleph-X project with the real thing, but it works and that's a start.
The Alephs were never available as kits. The schematics are available at www.passlabs.com, but you'll need to do a bit of work to put them together. Not that it can't be done, mind you. I've got two pairs of Aleph 2s, a Mini-A (with boards that MikeW was kind enough to run up--my prototype was point-to-point), not to mention the odd Aleph-X and a few other little experimental knick-knacks that I play with when I have time.
The Zens are fine project amps, and better documented than the Alephs in the official sense. For unofficial documentation on the Alephs, poke around here.
The X amps are doable, and I've taken a few steps in that direction, but it's not a high priority with me at the moment. The best source for help on that topology is Petter's X-100 thread.
Grey