LOL. Ok Paul. Point taken!... but if we just substitute "participant" for "guy" it sounds ok, right?
Er...uh, hi.
Someone wrote me a note saying Himself was looking for me.
(Gracious me! Talk about embarrassing...I feel like I'm on stage, but don't know what songs we're supposed to play tonight...will somebody at least tell me what key we're in so I can fake it? [Failing that, will someone cue me in on what the current topic is so I won't look like a fool yakking about MOSFETs, when everybody else is talking about building an A-X with tubes.])
(Oops. Maybe I shouldn't have said that.)
The Year From Hell continues. I'll try to get with you folks either tomorrow or Thursday if the stereo gods permit.
Hope Santa brings you all plenty of parts to play with. Someone please remember to feed Rudolph...he's partial to chocolate chip cookies.
Grey
Someone wrote me a note saying Himself was looking for me.
(Gracious me! Talk about embarrassing...I feel like I'm on stage, but don't know what songs we're supposed to play tonight...will somebody at least tell me what key we're in so I can fake it? [Failing that, will someone cue me in on what the current topic is so I won't look like a fool yakking about MOSFETs, when everybody else is talking about building an A-X with tubes.])
(Oops. Maybe I shouldn't have said that.)
The Year From Hell continues. I'll try to get with you folks either tomorrow or Thursday if the stereo gods permit.
Hope Santa brings you all plenty of parts to play with. Someone please remember to feed Rudolph...he's partial to chocolate chip cookies.
Grey
Hey dude, whazzup? Welcome back. You should be getting something from us sorry it won't be for Xmas. 😉
Grey told me it's ok to forward his mailing address (I sent him some FETs a few months back). Should I contact hifiZen or grataku, or somebody else?
He's had a tough year, folks, and it hasn't stopped yet. But I think he'll be back soon.
He's had a tough year, folks, and it hasn't stopped yet. But I think he'll be back soon.
I'm sure the subject of PCB and heatsinks will comes up once in a while in many of Grey's 1000 words posts.
Grey - Good to see a post from you!!!
The place has seemed a bit empty without you around...
The year from hell is almost over...hold on!!!
Hope the holidays are enjoyable for you...
Welcome Back!!!
The place has seemed a bit empty without you around...
The year from hell is almost over...hold on!!!
Hope the holidays are enjoyable for you...
Welcome Back!!!
Hooray!
Welcome back, Grey!
Santa has promised many of us nice A-X boards to play with
in the New Year. (Something about the workshop being
busy...) In the meantime, he asked that I first practise
by building a Mini-A. So that's what I'll be doing over the
holidays.
Cheers,
Dennis
Welcome back, Grey!
Santa has promised many of us nice A-X boards to play with
in the New Year. (Something about the workshop being
busy...) In the meantime, he asked that I first practise
by building a Mini-A. So that's what I'll be doing over the
holidays.
Cheers,
Dennis
wife and hifi
hi Christoph,
i have a hifi-compatible wife. she doesn`t matter at all, when i`m spending about 500Euro per month for diy equipment.
Others go to the bar, every evening...and when they come back, the wife has nothing to laugh...
500 Euro per month does not attak our monthly budget for living -at all.
by the way, have you experiences with Manger speakers?
you can mail to me, private,
Ralf
cocolino said:
hi Christoph,
i have a hifi-compatible wife. she doesn`t matter at all, when i`m spending about 500Euro per month for diy equipment.
Others go to the bar, every evening...and when they come back, the wife has nothing to laugh...
500 Euro per month does not attak our monthly budget for living -at all.
by the way, have you experiences with Manger speakers?
you can mail to me, private,
Ralf
Hi,
Here's a new thread: Aleph X - high power version.
http://www.diyaudio.com/forums/showthread.php?s=&postid=100486#post100486
It was started for the reason of it's title and I think it will be very relevent to a lot of us out here. I suspect a lot of people will be considering upgrading their Aleph 2's to X alephs, what with 700 boards out there!! I myself have the transistors, and toroids for Aleph 2 's but would like to switch over to an X but need to know about voltages etc.
Here's a new thread: Aleph X - high power version.
http://www.diyaudio.com/forums/showthread.php?s=&postid=100486#post100486
It was started for the reason of it's title and I think it will be very relevent to a lot of us out here. I suspect a lot of people will be considering upgrading their Aleph 2's to X alephs, what with 700 boards out there!! I myself have the transistors, and toroids for Aleph 2 's but would like to switch over to an X but need to know about voltages etc.
It's alive!!!
Well, I finally fired up my first channel of Aleph-X built on the beta board last night and did some testing and measurements. This is where a variac comes in real handy!
In any case, I have a few points to make:
1. be sure to match FETs. I decided to try building one without any matching, just to see if the amp could be adjusted to within acceptable parameters, and found this was not the case. My first channel has 140mV of offset between the + and - outputs that I can't get rid of. I suspect a matched diff pair would go a long way toward fixing this.
2. make sure the rectifiers are mounted on a decent heatsink. I used a short length of aluminum L-channel (maybe 2.5" of 1.5x1.5" channel) which is not quite sufficient. The rectifiers are running a bit hotter than I would like.
3. if you plan to operate at low power levels, you should use the HH current source (ZVP mosfet with LM329 reference), and connect the LM329's feed to the negative rail. In this configuration, I could successfully operate the A-X down to 9V rails or even less (7V, actually), but I don't recommend going below that. I'll have to do some more thorough exploration of the amp's headroom at those supply voltages, but I imagine that below about 9V rails, you'll see limitations on the diff pair which affect the output, and prevent full output swing from being achieved.
For my test, I used the HH current source, sans FET (I had no J501 or SST505 available). R19 and R29 were changed to 10K each, and the output mosfets were biased at 2.5A per side for a total of 5A bias. At that bias level, and the full 11.5-12V rail voltage, the amp really sizzles... I fear this monster will kick out more heat than my EL34 tube amp! 🙁
But, I can say this: Pink Floyd and Sade sound superb through my little 3" full-range test speaker. I can't wait to build the second channel, fix the offset problem, and start listening through proper speakers. But that will have to wait till January when I'm back from vacation...
Well, I finally fired up my first channel of Aleph-X built on the beta board last night and did some testing and measurements. This is where a variac comes in real handy!
In any case, I have a few points to make:
1. be sure to match FETs. I decided to try building one without any matching, just to see if the amp could be adjusted to within acceptable parameters, and found this was not the case. My first channel has 140mV of offset between the + and - outputs that I can't get rid of. I suspect a matched diff pair would go a long way toward fixing this.
2. make sure the rectifiers are mounted on a decent heatsink. I used a short length of aluminum L-channel (maybe 2.5" of 1.5x1.5" channel) which is not quite sufficient. The rectifiers are running a bit hotter than I would like.
3. if you plan to operate at low power levels, you should use the HH current source (ZVP mosfet with LM329 reference), and connect the LM329's feed to the negative rail. In this configuration, I could successfully operate the A-X down to 9V rails or even less (7V, actually), but I don't recommend going below that. I'll have to do some more thorough exploration of the amp's headroom at those supply voltages, but I imagine that below about 9V rails, you'll see limitations on the diff pair which affect the output, and prevent full output swing from being achieved.
For my test, I used the HH current source, sans FET (I had no J501 or SST505 available). R19 and R29 were changed to 10K each, and the output mosfets were biased at 2.5A per side for a total of 5A bias. At that bias level, and the full 11.5-12V rail voltage, the amp really sizzles... I fear this monster will kick out more heat than my EL34 tube amp! 🙁
But, I can say this: Pink Floyd and Sade sound superb through my little 3" full-range test speaker. I can't wait to build the second channel, fix the offset problem, and start listening through proper speakers. But that will have to wait till January when I'm back from vacation...
PS - the amp appears to be stable with 10pF for C2 and C8, though I haven't assualted it yet with nasty loads and test signals. I won't get to that until January either...
Matching the input differencial
I matched the input mosfets by a regular method, but when placed them in a circuit the drop on drain resistors (392 ohms) was different. So I decided to run the input stage separately (witout outputstage) and do some tweaking. I found out that the best way to match the input mosfets is in a circuit and I was switching prematched fets untill I got the same drop on drain resistors (which were 0.5% tolerance).
The only way (known to me) to adjust DC offset is by changing bias of the output stage and I didn't have any trouble with achieving low values. My offset stays at 3mV permanently.
The 200ohm trimmer in HH CCS is useful to adjust absolute DC value.
I matched the input mosfets by a regular method, but when placed them in a circuit the drop on drain resistors (392 ohms) was different. So I decided to run the input stage separately (witout outputstage) and do some tweaking. I found out that the best way to match the input mosfets is in a circuit and I was switching prematched fets untill I got the same drop on drain resistors (which were 0.5% tolerance).
The only way (known to me) to adjust DC offset is by changing bias of the output stage and I didn't have any trouble with achieving low values. My offset stays at 3mV permanently.
The 200ohm trimmer in HH CCS is useful to adjust absolute DC value.
Sounds like the right approach to me. I was a bit disappointed to find that I could only effect a few tens of millivolts of offset change by adjusting the output CCSs. In retrospect, it's obvious that feedback will tend to nullify the effect of any changes within the loop, but I was still surprised at just how much I could vary the idle current on one side without seeing any significant change in offset. Indeed it appears that the diff pair mosfets need to matched (actually, paired) in a circuit which duplicates the operating conditions of the diff pair. Both pinchoff voltage and transconductance probably play a role here, and the latter is not directly measurable in the usual single-transistor static matching circuit. So, matching 9610s for diff pairs will be first construction item on the list after vacation.
I didn't have any trouble at all, however, setting the absolute DC offset very near zero.
I didn't have any trouble at all, however, setting the absolute DC offset very near zero.