Aleph 2 setting
Variac,
I am clearly not understanding the circuit yet really, but looking at the formulars of William, I understand now that the dissipation of 245 Watt must include the current sources (he has doubled the dissipation, so one part for the output mosfet, the other for the current source I guess). If this is true, the values for the aleph 2 obviously could be:
voltage 22 volts
bias 5,8 amps
ac current gain 50%
number of fets 12
Peak current 5,8 amps
power 8 Ohms 100,0 watts
power 6 Ohms 100,9 watts
power 5 Ohms 84,1 watts
power 4 Ohms 67,3 watts
power 2 Ohms 33,6 watts
Dissipation 255,2 watts
Dissipation per fet 21,26666667 watts
Or with minimum dissipation:
voltage 22 volts
bias 5 amps
ac current gain 50%
number of fets 12
Peak current 5 amps
power 8 Ohms 100,0 watts
power 6 Ohms 75,0 watts
power 5 Ohms 62,5 watts
power 4 Ohms 50,0 watts
power 2 Ohms 25,0 watts
Dissipation 220 watts
Dissipation per fet 18,33333333 watts
William ?
Best Regards
Variac,
I am clearly not understanding the circuit yet really, but looking at the formulars of William, I understand now that the dissipation of 245 Watt must include the current sources (he has doubled the dissipation, so one part for the output mosfet, the other for the current source I guess). If this is true, the values for the aleph 2 obviously could be:
voltage 22 volts
bias 5,8 amps
ac current gain 50%
number of fets 12
Peak current 5,8 amps
power 8 Ohms 100,0 watts
power 6 Ohms 100,9 watts
power 5 Ohms 84,1 watts
power 4 Ohms 67,3 watts
power 2 Ohms 33,6 watts
Dissipation 255,2 watts
Dissipation per fet 21,26666667 watts
Or with minimum dissipation:
voltage 22 volts
bias 5 amps
ac current gain 50%
number of fets 12
Peak current 5 amps
power 8 Ohms 100,0 watts
power 6 Ohms 75,0 watts
power 5 Ohms 62,5 watts
power 4 Ohms 50,0 watts
power 2 Ohms 25,0 watts
Dissipation 220 watts
Dissipation per fet 18,33333333 watts
William ?
Best Regards
Would it help any if I said that building a bridged amp (such as the Aleph-X) is simply a case of building two smaller amps--each with 1/4 the power you require. If you intend to build a 100W amp, you'll end up putting two (heavily biased...which is where most people go wrong) 25W amps back-to-back.
I'm in the middle of writing a story, and thought I'd take a break. Decide on a target wattage (100? 150? 200? Into what load?) and I'll try to get back over here the next time I take a break.
Grey
I'm in the middle of writing a story, and thought I'd take a break. Decide on a target wattage (100? 150? 200? Into what load?) and I'll try to get back over here the next time I take a break.
Grey
GRollins said:
Grey, would would you recommend for aiming for 150W into a steady 4 ohm load?
--
Brian
Chris, no problem. If this is your method of learning, that's OK. Mine is different. I want to ask my questions. If they are stupid, well great ! Than it should be very easy to answer them. When I look at the viewing counter of this threat, it seems that some people share the same interest / questions with us here. If no one starts to ask, why than have a forum ?
BTW I smoked a couple of amps, but that's OK as finally most of them survive these days. I personally come more from the tube fraction, so SS was not my cup of tea, but the Aleph-X seems to interesting...and if I smoke again some things, well...that's part of the learning experience. No risk, no fun.
By the way: Let's not have philosophical discussions / flame wars or any of this stuff in this threat at least. Let's stay with the subject. So, do you have a content question or answer ?
BTW I smoked a couple of amps, but that's OK as finally most of them survive these days. I personally come more from the tube fraction, so SS was not my cup of tea, but the Aleph-X seems to interesting...and if I smoke again some things, well...that's part of the learning experience. No risk, no fun.
By the way: Let's not have philosophical discussions / flame wars or any of this stuff in this threat at least. Let's stay with the subject. So, do you have a content question or answer ?
Grey, great to have you here
I would agree to Variac: Let's go for an Aleph-X which can be easily generated from an Aleph 2, so the questions is how much can we get out of 12 Mosfets / channel without changing heatsinks etc. If the dissipations calcs above are right, we talk about 100 Watt into 6 ohm with some stability around it (so that power is not cut in half immediately with half of the impedance).
Best Regards & THanks for your help
I would agree to Variac: Let's go for an Aleph-X which can be easily generated from an Aleph 2, so the questions is how much can we get out of 12 Mosfets / channel without changing heatsinks etc. If the dissipations calcs above are right, we talk about 100 Watt into 6 ohm with some stability around it (so that power is not cut in half immediately with half of the impedance).
Best Regards & THanks for your help
So Grey,(a pleasure to hear from you....) Instead of a target wattage, we have a target of 12 mosfets per ch and Aleph 2 heatsinks!!
With enough bias to make it sound goooood!
With enough bias to make it sound goooood!
Blitz said:
No; that's not right. It is pretty much an Aleph output stage, so the current source provides the current to bias the output transistor(s). Therefore, (of course) that current flows through both the current source transistors and the output transistors.
The dissipation is basically the bias current times the voltage across the two transistors, which is pretty much the differential rail voltage (V+ - (V-)).
About how much you can dissipate with X number of transistors, keep in mind that Mr. Pass's "standard" is about 25 watts for his commercial offerings. (Aleph 2 dissipates 300 W. 300/12=25 W per device). But on the Zen amp (Zen 4) they dissipate 40W each. (40V rail and 2A bias; two transistors in series dissipating 80 W total). I think I've seen him comment that he figures about 50Watts as his upper limit for home projects where it's ok if one fails every once in a while.
So maybe that's some help.
Merry Christmas. El Pipo tomorrow!
No problem Blitz,
Glad that you asked those questions that I have in mind too. I do not really care how much power I am going to get for the Aleph-X. What I want to know is ;
1/with using 2 11"X11" heatsink per channel what are the maximum number of output devices I can have, share the load
2/ and I want to limit the heatsink to around 50 degree C max.
3/ with speaker load of nominal 8ohm to 6ohm.
So how do I work this backward to (per channel)
1/ get the suitable current bias per device and hence total Iq ?
2/ what rail voltage requires?
3/ what size/spec transformer is suitable?
4/ when adding more devices, do I have to do anything with R8,R10,R37 and R39 assuming I am going to replicate the devices as Q1a, R7a, R5a and so on...(Grey's schematic).
5/ I know someone has mentioned how to set this up to run unbalanced, but I am confused by the different methods, can a schematic for that part of the circuit post/draw here?
6/ How about the Ian's resistors, can a schematic post here, I am not sure where I should connect them? Oh what value should they be for the above parameters?
7/ regulate PSU or multiplier? or where can I find a tube rectifier schematic to use instead of those $5 35A surplus bridge recticfier, any advantage using tube rectifier?
Any comments is appreciated.
Regards,
Chris😎
Glad that you asked those questions that I have in mind too. I do not really care how much power I am going to get for the Aleph-X. What I want to know is ;
1/with using 2 11"X11" heatsink per channel what are the maximum number of output devices I can have, share the load
2/ and I want to limit the heatsink to around 50 degree C max.
3/ with speaker load of nominal 8ohm to 6ohm.
So how do I work this backward to (per channel)
1/ get the suitable current bias per device and hence total Iq ?
2/ what rail voltage requires?
3/ what size/spec transformer is suitable?
4/ when adding more devices, do I have to do anything with R8,R10,R37 and R39 assuming I am going to replicate the devices as Q1a, R7a, R5a and so on...(Grey's schematic).
5/ I know someone has mentioned how to set this up to run unbalanced, but I am confused by the different methods, can a schematic for that part of the circuit post/draw here?
6/ How about the Ian's resistors, can a schematic post here, I am not sure where I should connect them? Oh what value should they be for the above parameters?
7/ regulate PSU or multiplier? or where can I find a tube rectifier schematic to use instead of those $5 35A surplus bridge recticfier, any advantage using tube rectifier?
Any comments is appreciated.
Regards,
Chris😎
Chris,
THanks for your questions. Certainly I can't answer them all as I need to learn some more, here some of my comments:
- Heatsinking: I guess more tech. spechs are need of the heat sink you have in mind. William, your heat-sheet would be great ?
- TUbe-rectifying: Great idea, but these in general are made for high voltages and low currents. THerefore, You can have in theory some for the driver stage (Counterpoint did that, but they had a triode (6922) as well in the driver stage). But I believe you can't separate the driver stage-rail from the output stage in an Aleph. There are other ways to get SS-Diodes calm. I have a nice article on how to filter anything out, which I can send you after christmas.
- Choke-Input will help you in two respects: Less noise from the transfomer / diodes and you can come along with a smaller transformer to obtain the same / better sonic results. Quiet common in tube gear, but a good choke costs money, therefore not oftenly seen these days.
- Bias and voltages should be easy to calculate with Williams sheet.
- Transformer secs I would simulated with PSU-Designer to be sure (depends on the diodes and filtering you want to use) (www.duncanamps.com )
- There have been quite a bit of discussion around regulated supplies but with 5 Amps to regulate this might be not very practical (and series regulators are anyhow not good for audio)
THanks for your questions. Certainly I can't answer them all as I need to learn some more, here some of my comments:
- Heatsinking: I guess more tech. spechs are need of the heat sink you have in mind. William, your heat-sheet would be great ?
- TUbe-rectifying: Great idea, but these in general are made for high voltages and low currents. THerefore, You can have in theory some for the driver stage (Counterpoint did that, but they had a triode (6922) as well in the driver stage). But I believe you can't separate the driver stage-rail from the output stage in an Aleph. There are other ways to get SS-Diodes calm. I have a nice article on how to filter anything out, which I can send you after christmas.
- Choke-Input will help you in two respects: Less noise from the transfomer / diodes and you can come along with a smaller transformer to obtain the same / better sonic results. Quiet common in tube gear, but a good choke costs money, therefore not oftenly seen these days.
- Bias and voltages should be easy to calculate with Williams sheet.
- Transformer secs I would simulated with PSU-Designer to be sure (depends on the diodes and filtering you want to use) (www.duncanamps.com )
- There have been quite a bit of discussion around regulated supplies but with 5 Amps to regulate this might be not very practical (and series regulators are anyhow not good for audio)
Even I have in mind to modify my Aleph 2 (actually it’s a 1.6) into a 100W (down to 2 ohms) Aleph-X. I’ll use the new (X) front-ends, the 12 PowerMosFets (IRF240) as already installed, will have new 1,000VA transformers with 2x 18VAC and 6 capacitors of 47,000µF each in a CRCRC configuration. The bias will be some 7A, which means each transistor handles about 27W (1.2A) and the total dissipation will be 320W. To get the expected 0.5V over the source resistors, I’ll change these resistors (Aleph 2 = 1R) into 0R39.
Merry Xmas to all of you - jens
Merry Xmas to all of you - jens
Running behind (what, you're surprised?), so I'm doing this on the fly...
Okay, let's postulate that you want to rebuild a pair of Aleph 2s into an Aleph-X of some reasonable wattage. I'm sure you'd probably like it if the power came out about the same, right?
Looks as though the rails will need to be +-22.7V.
You'll be putting three pairs of devices on each side, for a total of twelve for the entire channel.
(You <i>are</i> building monoblocks, aren't you?)
If you were to assume a purely resistive 8 ohm load, you could use a .82 ohm Source resistor for each MOSFET. We're assuming that the nominal voltage across the Source resistor will be .5V, the way Nelson did it in the Alephs. Remember that any number of other things will influence that number, not least of which being heat.
However...
Since there aren't that many purely resistive 8 ohm speakers out there, let's throw in some more bias by reducing the Source resistor value. This will keep our circuit from current limiting if the impedance drops a little bit. The .82 ohm resistors would give you a bias (again, assuming .5V across the resistor) of a bit over .6A per device. Seeing as how it's Christmas, let's heat the house 'for free.' Let's use .47 ohms for the Source resistor. This will give a bias of about 1A per device. Given that the rails are 22.7V, we'll be looking at around 24 or 25W dissipation per MOSFET (i.e. the same as an Aleph). Dissipation at idle will be just south of 300W per chassis, so plan accordingly. A 500VA transformer would do the job with good ventillation--possibly even a fan--but I'd rather go for a higher VA rating just to be sure. At least 600VA, perhaps even 750 or 1kVA. The power draw will be pretty close to DC, even under load, so you don't need to get as funky with the power supply as you would with a class AB amp. That's not to say that you can't use an elaborate circuit, just that it's not as critical. Power supplies just love delivering DC; it's when you ask a DC supply to deliver AC that it gets twitchy.
Since you're developing the same amount of heat, you can use the same heatsinks you were using for your Aleph 2s.
Whether you can use the same output devices is another question, though. You'll be running half the voltage and twice the current, so you'll be hitting a different point on the SOA chart. Keep your wits about you.
Your nominal output power will still be 100W, which won't hurt your feelings, I'm sure.
There will be other things that need adjusting, but there are two loaves of fresh bread coming out of the oven, and they're calling my name. I'll try to get back with some other values tomorrow.
Grey
Okay, let's postulate that you want to rebuild a pair of Aleph 2s into an Aleph-X of some reasonable wattage. I'm sure you'd probably like it if the power came out about the same, right?
Looks as though the rails will need to be +-22.7V.
You'll be putting three pairs of devices on each side, for a total of twelve for the entire channel.
(You <i>are</i> building monoblocks, aren't you?)
If you were to assume a purely resistive 8 ohm load, you could use a .82 ohm Source resistor for each MOSFET. We're assuming that the nominal voltage across the Source resistor will be .5V, the way Nelson did it in the Alephs. Remember that any number of other things will influence that number, not least of which being heat.
However...
Since there aren't that many purely resistive 8 ohm speakers out there, let's throw in some more bias by reducing the Source resistor value. This will keep our circuit from current limiting if the impedance drops a little bit. The .82 ohm resistors would give you a bias (again, assuming .5V across the resistor) of a bit over .6A per device. Seeing as how it's Christmas, let's heat the house 'for free.' Let's use .47 ohms for the Source resistor. This will give a bias of about 1A per device. Given that the rails are 22.7V, we'll be looking at around 24 or 25W dissipation per MOSFET (i.e. the same as an Aleph). Dissipation at idle will be just south of 300W per chassis, so plan accordingly. A 500VA transformer would do the job with good ventillation--possibly even a fan--but I'd rather go for a higher VA rating just to be sure. At least 600VA, perhaps even 750 or 1kVA. The power draw will be pretty close to DC, even under load, so you don't need to get as funky with the power supply as you would with a class AB amp. That's not to say that you can't use an elaborate circuit, just that it's not as critical. Power supplies just love delivering DC; it's when you ask a DC supply to deliver AC that it gets twitchy.
Since you're developing the same amount of heat, you can use the same heatsinks you were using for your Aleph 2s.
Whether you can use the same output devices is another question, though. You'll be running half the voltage and twice the current, so you'll be hitting a different point on the SOA chart. Keep your wits about you.
Your nominal output power will still be 100W, which won't hurt your feelings, I'm sure.
There will be other things that need adjusting, but there are two loaves of fresh bread coming out of the oven, and they're calling my name. I'll try to get back with some other values tomorrow.
Grey
I always like some extra bias, but I should point out that
the reactance (phase angle) of the load has nothing to do
with the selection of bias point. As long as the absolute
impedance is the same as a resistive load, then the bias figure
for that resistive load will be adequate.
A point I have always intended as a thread unto itself, it is
a fact that amplifiers usually have less distortion into reactive
loads than resistive loads of the same absolute impedance.
With a resistive load, the amplifier is called upon to deliver
maximum current at the same time as maximum voltage. This
means that the output devices max out for current just as the
voltage across them is at a minimum - a double gain hit on the
gain of the devices.
With a 90 degree reactive load, maximum current occurs when
the voltage across the device is at quiescent ( value of one
supply rail ) and so the gain of the device is higher and more
linear, and the distortion is lower.
It's true that for AB type amps driving a reactive load results
in more dissipation, but were talking DIY here, not some wimpy
plastic and tin commodity. Class A amps? They just laugh at
reactive loads. The worst case for them is idle.
In any case, when I see discourse on reactive loads and how
tough they are, I just smile.
Merry Xmas.
the reactance (phase angle) of the load has nothing to do
with the selection of bias point. As long as the absolute
impedance is the same as a resistive load, then the bias figure
for that resistive load will be adequate.
A point I have always intended as a thread unto itself, it is
a fact that amplifiers usually have less distortion into reactive
loads than resistive loads of the same absolute impedance.
With a resistive load, the amplifier is called upon to deliver
maximum current at the same time as maximum voltage. This
means that the output devices max out for current just as the
voltage across them is at a minimum - a double gain hit on the
gain of the devices.
With a 90 degree reactive load, maximum current occurs when
the voltage across the device is at quiescent ( value of one
supply rail ) and so the gain of the device is higher and more
linear, and the distortion is lower.
It's true that for AB type amps driving a reactive load results
in more dissipation, but were talking DIY here, not some wimpy
plastic and tin commodity. Class A amps? They just laugh at
reactive loads. The worst case for them is idle.
In any case, when I see discourse on reactive loads and how
tough they are, I just smile.
Merry Xmas.
Thanks Grey, this confirms my calculations. Am I right, that I get even 100W on 2 ohms if the bias is ~1,2A each, which means the source resistors should be .42 ohms (.39 next available)?
50W-Aleph X
Hi oll ... I would like to builld 50W Aleph X...I have 24 IRFP240 so I can use 3 pair of mosfets on ich side ,but I think that my heatsinks could only take 2 pairs on each side( for total of 8 per chanell ) ...
Is it posibile to get 50 W with 2 pairs of mosfet on each side and at what voltage ... do I nead to change some resistors ???
I'am not EE so please give me some advice ...
It would be nice if some one could write some doc about what we have to do if we would like to build 25,50,75,100W Aleph-X version ( what resistors to change,what transformers to use ... )
Thanks
Josip
Hi oll ... I would like to builld 50W Aleph X...I have 24 IRFP240 so I can use 3 pair of mosfets on ich side ,but I think that my heatsinks could only take 2 pairs on each side( for total of 8 per chanell ) ...
Is it posibile to get 50 W with 2 pairs of mosfet on each side and at what voltage ... do I nead to change some resistors ???
I'am not EE so please give me some advice ...
It would be nice if some one could write some doc about what we have to do if we would like to build 25,50,75,100W Aleph-X version ( what resistors to change,what transformers to use ... )
Thanks
Josip
Jessica Rabbit stared in horror at the stream of yellow-green liquid jetting towards her...
"It's <i>diiip!</i>," she screamed.
(...what I wouldn't give to be stranded on a remote island with that woman, 'toon or not...but I digress...)
Phase rotations don't scare me. Impedance dips do. Nasty, slimy, hungry little things that scuttle around and eat all my precious power.
("<i>Ah, my Precious!</i>" he whispered, caressing the heatsink with his fingers. "<i>We wants it, we needs it...</i>)
If you're Nelson, with speakers that will comb your hair (think the old Maxell ads, hair streaming back) at thirty paces on a single watt, you can afford to feed the dips a stray morsel of power. Don't forget, the man builds thousand watt amps for a living--though if I read the signs aright, the ones he has at home are far, far smaller. Me? I'm running upper eighties for efficiency, resistive (hence a flat impedance curve--okay, okay, the RD-75s have an RCL notch filter, but let's not get picky) from 70Hz up, so I don't have to worry about such things except with the subs. But I prefer to leave some margin for impedance dips, just because.
I've always had this sneaking suspicion that Z-dips are responsible for peoples' assessments that certain amp/speaker combinations 'aren't dynamic.' At low volumes, everything's all right, but turn it up and the poor amp runs out of current because it's all being sucked into this black hole at the (I guess I should specify a relatively broadband problem for clarity's sake...) dip, leaving little for other frequencies when someone does something rude like whack a drum.
(Nelson, you've got more experience at this than I do, and more test equipment to investigate these things. Comments? I'm just running this as one of my philosophical musings, perhaps with insufficient data.)
Is the fault that of the amp designer or the speaker designer?
Yes.
Each should make allowances for the other. Since we're talking amps, here, it's up to us to plan for inconsiderate speaker designers. (Old driver-safety ad: Watch out for the <i>other</i> guy! Probably only makes sense to folks here in the US over <i>mumble</i> years of age. [Actually, I'm 45--not that bad, as these things go--unless you're seventeen, in which case it's worse than the far side of the moon. Inconceivable to live so long.])
Besides, even if the speaker doesn't have a black hole, more bias sounds good.
And it gets chilly down here in the basement in the winter. I'll take all the 'free' heat I can get.
Grey
P.S.: More on parts values later. I've got to find the confounded schematic so I can talk semi-intelligently about what to change. Worse yet, my mind is on other things...namely turning the preamp circuit I've been threatening to post into a universal gain module suitable for other projects. And I had another idea for a story this afternoon, and I haven't even finished the other one yet. Yikes!
"It's <i>diiip!</i>," she screamed.
(...what I wouldn't give to be stranded on a remote island with that woman, 'toon or not...but I digress...)
Phase rotations don't scare me. Impedance dips do. Nasty, slimy, hungry little things that scuttle around and eat all my precious power.
("<i>Ah, my Precious!</i>" he whispered, caressing the heatsink with his fingers. "<i>We wants it, we needs it...</i>)
If you're Nelson, with speakers that will comb your hair (think the old Maxell ads, hair streaming back) at thirty paces on a single watt, you can afford to feed the dips a stray morsel of power. Don't forget, the man builds thousand watt amps for a living--though if I read the signs aright, the ones he has at home are far, far smaller. Me? I'm running upper eighties for efficiency, resistive (hence a flat impedance curve--okay, okay, the RD-75s have an RCL notch filter, but let's not get picky) from 70Hz up, so I don't have to worry about such things except with the subs. But I prefer to leave some margin for impedance dips, just because.
I've always had this sneaking suspicion that Z-dips are responsible for peoples' assessments that certain amp/speaker combinations 'aren't dynamic.' At low volumes, everything's all right, but turn it up and the poor amp runs out of current because it's all being sucked into this black hole at the (I guess I should specify a relatively broadband problem for clarity's sake...) dip, leaving little for other frequencies when someone does something rude like whack a drum.
(Nelson, you've got more experience at this than I do, and more test equipment to investigate these things. Comments? I'm just running this as one of my philosophical musings, perhaps with insufficient data.)
Is the fault that of the amp designer or the speaker designer?
Yes.
Each should make allowances for the other. Since we're talking amps, here, it's up to us to plan for inconsiderate speaker designers. (Old driver-safety ad: Watch out for the <i>other</i> guy! Probably only makes sense to folks here in the US over <i>mumble</i> years of age. [Actually, I'm 45--not that bad, as these things go--unless you're seventeen, in which case it's worse than the far side of the moon. Inconceivable to live so long.])
Besides, even if the speaker doesn't have a black hole, more bias sounds good.
And it gets chilly down here in the basement in the winter. I'll take all the 'free' heat I can get.
Grey
P.S.: More on parts values later. I've got to find the confounded schematic so I can talk semi-intelligently about what to change. Worse yet, my mind is on other things...namely turning the preamp circuit I've been threatening to post into a universal gain module suitable for other projects. And I had another idea for a story this afternoon, and I haven't even finished the other one yet. Yikes!
Definitely goes both ways.GRollins said:
I used to wonder what all the fuss was about Watt/Puppies
until I hooked up an X600. Then I decided that both Alephs
and Wilsons were at fault. 😉
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