Vince,
I'd estimate a final rail in the vicinity of 18 or 19 volts. This is actually close to where I was running my Mini-A at full power (I was holding it down to 15V rails with a Variac).
The transformer will be warm to the touch, but not too bad. What you'll need to watch is your device dissipation, which will be on the order of 38W/device. Make sure you've got plenty of heatsinking if you're going to run them that hot.
Grey
I'd estimate a final rail in the vicinity of 18 or 19 volts. This is actually close to where I was running my Mini-A at full power (I was holding it down to 15V rails with a Variac).
The transformer will be warm to the touch, but not too bad. What you'll need to watch is your device dissipation, which will be on the order of 38W/device. Make sure you've got plenty of heatsinking if you're going to run them that hot.
Grey
One more question before I order!!!
Grey, one more question. I reread all your posts here and I was just wondering exactly what you meant. By increasing R11 to 220k ohms, do I still need to increase R18 and 19 to .33 ohms?
It won't hurt to buy all them right now, but when I go to put this thing together, I want to use the correct values for R11, R18 and R19.
Thanks for putting this together. Let you know how it turns out.\
Sorry to be so think headed about this!
Vince
Grey, one more question. I reread all your posts here and I was just wondering exactly what you meant. By increasing R11 to 220k ohms, do I still need to increase R18 and 19 to .33 ohms?
It won't hurt to buy all them right now, but when I go to put this thing together, I want to use the correct values for R11, R18 and R19.
Thanks for putting this together. Let you know how it turns out.\
Sorry to be so think headed about this!
Vince
PCB Layout?
Grey Yoo Da Mann! really nice circuit, a lot of these babies will be built, any chance of the pcb layout being made available for us idle/incapable/software-less types.
Mozfet.
goodstuff57@hotmail.com
Grey Yoo Da Mann! really nice circuit, a lot of these babies will be built, any chance of the pcb layout being made available for us idle/incapable/software-less types.
Mozfet.
goodstuff57@hotmail.com
Contrary to what some have supposed, I don't know Nelson personally. We live on opposite sides of the continent. This is a clever ploy on his part to keep me from showing up at the Pass Labs plant with my offbeat ideas and a hastily scratched out schematic.
The fiend.
The scoundrel.
However, his days are far more productive without me getting underfoot, I'm sure. I had no idea that the Zen would be getting the Aleph treatment when I began the Mini-A. It's just something that my curiosity drove me to do.
(Hey, fellas...want a Mini-X?)
Moral of the story: Don't ever stir Grey's curiosity. Bad idea. <i>Very</i> bad idea.
My intent is/was not to steal Nelson's thunder. I just like playing with this stuff.
Okay...on to the questions, with apologies to anyone I miss and to everyone (yes, Vince, I mean you) who's been waiting.
Vince--When it comes to setting the bias, think of R18 & 19 as the coarse adjustment, and R11 as the fine-tuner. I'm short of parts (read: money) and have to do what I can with what I have on hand. I've got a few .47 ohm 2W resistors, and a goodly selection of 1/2W values, but I don't have .33 ohms on hand. So I made-do. In your case, use the .33 ohm (or .36 or .39 or...) resistors and fiddle R11 until the bias is where you want it.
hifi--I think you'll find that +-6V rails are a bit light. The 9V Zener in the front end won't come up, for instance. That's not to say that you couldn't reconfigure the current source, though...
mozfet--No PCB at present. I may get around to doing one at some point in the future, but at the moment, I'm hip-deep in alligators and don't have time. Gawd, I wish I had someone I could palm some of this stuff off on. "Minion, today I want you to work up a PCB for the Mini-A." In the meantime, I'll just keep dreaming of a day when I can get to my ideas while they're hot.
carpenter--Grafting a balanced front end onto the Mini-A shouldn't be all that difficult. Yes, as Vince pointed out, I believe someone has already done it, at least on paper.
Koy--Q5 is the protection circuit. It senses the current going through R19 via R17 & R13 (they form a voltage divider that sets the trigger point). Should the amp experience a short, the current through R19 increases, which increases the voltage drop seen at the base of Q5, which switches on and limits drive to Q7. Or at least that's the way I read it. I haven't tested the poor thing with a screwdriver--just don't have the heart (or the time).
So many ideas...so little time.
Did I mention the Difference Engine?
Hagrid: "I shouldn't have said that!"
Or how about the...
I'd better stop while I'm ahead. I can't even keep up with what I've got on the burner now. (<i>Grumble, grumble...mutter, mutter...</i>)
Grey
The fiend.
The scoundrel.
However, his days are far more productive without me getting underfoot, I'm sure. I had no idea that the Zen would be getting the Aleph treatment when I began the Mini-A. It's just something that my curiosity drove me to do.
(Hey, fellas...want a Mini-X?)
Moral of the story: Don't ever stir Grey's curiosity. Bad idea. <i>Very</i> bad idea.
My intent is/was not to steal Nelson's thunder. I just like playing with this stuff.
Okay...on to the questions, with apologies to anyone I miss and to everyone (yes, Vince, I mean you) who's been waiting.
Vince--When it comes to setting the bias, think of R18 & 19 as the coarse adjustment, and R11 as the fine-tuner. I'm short of parts (read: money) and have to do what I can with what I have on hand. I've got a few .47 ohm 2W resistors, and a goodly selection of 1/2W values, but I don't have .33 ohms on hand. So I made-do. In your case, use the .33 ohm (or .36 or .39 or...) resistors and fiddle R11 until the bias is where you want it.
hifi--I think you'll find that +-6V rails are a bit light. The 9V Zener in the front end won't come up, for instance. That's not to say that you couldn't reconfigure the current source, though...
mozfet--No PCB at present. I may get around to doing one at some point in the future, but at the moment, I'm hip-deep in alligators and don't have time. Gawd, I wish I had someone I could palm some of this stuff off on. "Minion, today I want you to work up a PCB for the Mini-A." In the meantime, I'll just keep dreaming of a day when I can get to my ideas while they're hot.
carpenter--Grafting a balanced front end onto the Mini-A shouldn't be all that difficult. Yes, as Vince pointed out, I believe someone has already done it, at least on paper.
Koy--Q5 is the protection circuit. It senses the current going through R19 via R17 & R13 (they form a voltage divider that sets the trigger point). Should the amp experience a short, the current through R19 increases, which increases the voltage drop seen at the base of Q5, which switches on and limits drive to Q7. Or at least that's the way I read it. I haven't tested the poor thing with a screwdriver--just don't have the heart (or the time).
So many ideas...so little time.
Did I mention the Difference Engine?
Hagrid: "I shouldn't have said that!"
Or how about the...
I'd better stop while I'm ahead. I can't even keep up with what I've got on the burner now. (<i>Grumble, grumble...mutter, mutter...</i>)
Grey
I agree, Nelson. Seems to me that I read once that one of them writes the crowd scenes, because he's better at that, and the other writes the one-on-one scenes. I don't remember which is which, but I'd be willing to bet that it's Niven that writes the smaller scale stuff; generally the backbone of any story.
The newer stuff with Barnes...I dunno...
Grey
The newer stuff with Barnes...I dunno...
Grey