BobEllis said:
This calculation ignores the inverse transconductance of the
Mosfets and limited gain of the npn circuit, so it is a first order
approximation. From experience, the actual gain will be less
than this calculation, which is why I always prefer to measure
the current ratios through the resistors.
😎
Heat sink question
A friend of mine is building an Aleph X. He's got four square heat sinks that he can arrange as two longways pairs, forming a long tunnel with a fan at one end. Or, he can place them side by side with pairs facing one another and put a spreader between the fan and this wider, shorter tunnel.
Which arrangement would be preferable?
A friend of mine is building an Aleph X. He's got four square heat sinks that he can arrange as two longways pairs, forming a long tunnel with a fan at one end. Or, he can place them side by side with pairs facing one another and put a spreader between the fan and this wider, shorter tunnel.
Which arrangement would be preferable?
SY,
I vote for the shorter arrangement. Longer heatsinks get cumulatively hotter towards the end and you get a notable difference in temperature from the first device to the last one.
One of the big heasink sites (Aavid, maybe?) has a nifty calculator for online determination of degree/Watt ratios for a given extrusion profile. It's fascinating to play with. If I recally correctly, the effectiveness of the heatsink falls off fairly rapidly after the first six or eight inches. Forced air helps, of course, but the general concept remains.
These amps with really, really tall heatsinks may look neat, but they don't work too well towards the top.
Grey
I vote for the shorter arrangement. Longer heatsinks get cumulatively hotter towards the end and you get a notable difference in temperature from the first device to the last one.
One of the big heasink sites (Aavid, maybe?) has a nifty calculator for online determination of degree/Watt ratios for a given extrusion profile. It's fascinating to play with. If I recally correctly, the effectiveness of the heatsink falls off fairly rapidly after the first six or eight inches. Forced air helps, of course, but the general concept remains.
These amps with really, really tall heatsinks may look neat, but they don't work too well towards the top.
Grey
I can see that for convection cooling, but does forced-air change that scenario?
Sorry for the dumb questions, I'm a tube guy.
Sorry for the dumb questions, I'm a tube guy.
Intrigued by the question I found this very informative page from Rod. It's stunning what amount of good info is collected there.
http://sound.westhost.com/heatsinks.htm
/Hugo
http://sound.westhost.com/heatsinks.htm
/Hugo
Forced air will reduce the differential, but it will still be there. The air entering the heatsink will be cool. It will accept a certain amount of heat from the heatsink based on the difference between the ambient temperature and the temperature of the heatsink. By the time the air has reached the far end of the heatsink it will be warmer--possibly even downright hot--and will not accept as much heat, leaving the tail end of the heatsink hotter.
Convection, obviously, is just a low speed case of forced air cooling. The air heats, the density decreases, and the air rises, thus starting the air flow. Using a fan isn't really different other than the volume of air moving past per unit of time. And that's the crux of the matter. It's going to boil down to how much air you intend to move. A little bit of increase is reasonable because you can keep the fan noise down to a level that we as audiophiles regard as acceptable. To get the air flow higher you'll have to generate more noise. Granted, the temperature differential between the leading and trailing ends of the heatsink will drop, but you'll pay a price in noise.
Is there any way you can do a mockup of the output stage--tie the output devices to the bias circuit but ground the signal inputs--and test the heatsinks both ways? That way you'd know for sure.
Grey
Convection, obviously, is just a low speed case of forced air cooling. The air heats, the density decreases, and the air rises, thus starting the air flow. Using a fan isn't really different other than the volume of air moving past per unit of time. And that's the crux of the matter. It's going to boil down to how much air you intend to move. A little bit of increase is reasonable because you can keep the fan noise down to a level that we as audiophiles regard as acceptable. To get the air flow higher you'll have to generate more noise. Granted, the temperature differential between the leading and trailing ends of the heatsink will drop, but you'll pay a price in noise.
Is there any way you can do a mockup of the output stage--tie the output devices to the bias circuit but ground the signal inputs--and test the heatsinks both ways? That way you'd know for sure.
Grey
Test block mock-ups are superbly useful. But I think the challenge is the mechanics rather than the electronics in this case. Or it would be for me (metalworking-challenged)- hopefully the builder can run a mill better than me.
Hi,
one big difference between convection and forced air cooling is the way of the airflow. Without fan it is laminar, with a fan turbulent. Turbulent flow can take away a lot more heat from the sinks.
William
one big difference between convection and forced air cooling is the way of the airflow. Without fan it is laminar, with a fan turbulent. Turbulent flow can take away a lot more heat from the sinks.
William
Aleph-X Group Buy
Hi guy's 😉
Anybody who know anything about as if there will be a group buy soon for the Aleph-X Rev 1.0 boards made by hifiZen.
I am very interested in building an Amp by means of the Aleph-X
NOT the ones i have seen here made by kristian.
Best regards
analogair
Hi guy's 😉
Anybody who know anything about as if there will be a group buy soon for the Aleph-X Rev 1.0 boards made by hifiZen.
I am very interested in building an Amp by means of the Aleph-X
NOT the ones i have seen here made by kristian.
Best regards
analogair
Aleph-X PCB Film or Anything so i can make me some boards
Hi Again Guys ;-)
Yet another request.
Do any of you guys or girls have a film or anything, so i will be able to make me some PCB's for an Aleph-X
I my self are trying to redraw some pics i found of some boards called Rev 1.0
I will gladly post them when done, but it will take a large amount of time before i'm done.
Which is the reason for my request.
Best regards
analogair
Hi Again Guys ;-)
Yet another request.
Do any of you guys or girls have a film or anything, so i will be able to make me some PCB's for an Aleph-X
I my self are trying to redraw some pics i found of some boards called Rev 1.0
I will gladly post them when done, but it will take a large amount of time before i'm done.
Which is the reason for my request.
Best regards
analogair
Re: Aleph-X PCB Film or Anything so i can make me some boards
What about the ones Kari has for sale?
Anthony
analogair said:Hi Again Guys ;-)
Yet another request.
Do any of you guys or girls have a film or anything, so i will be able to make me some PCB's for an Aleph-X
I my self are trying to redraw some pics i found of some boards called Rev 1.0
I will gladly post them when done, but it will take a large amount of time before i'm done.
Which is the reason for my request.
Best regards
analogair
What about the ones Kari has for sale?
Anthony
Aleph-X Boards
Coulomb, i was under the impression that the ones kari has for sale, only goes in a group buy ?
Best regards
änalogair
Coulomb, i was under the impression that the ones kari has for sale, only goes in a group buy ?
Best regards
änalogair
Re: Aleph-X Boards
Oh, I mention it as I thought he had extras, youcan always email him.
Anthony
analogair said:
Oh, I mention it as I thought he had extras, youcan always email him.
Anthony
I remember someone posted a schamatic of an A-X amp with feedback (in addition to the x-feedback) to reduce the absolute DC offset but I cannot find it now. Could anyone point me to it? I also wonder how well did the approach work.
OK, I know I am asking something that has been covered before, but I have tried searching and haven't really made progress that way.
What are the recommended values for C7, C8, C9, C10 if they are used, because I think I need to use them?
After two weekends of troubleshooting my non-functional monoblocks, I found my wiring error (somehow forgot that if the wire layout doglegs left when viewed from the top, when you flip over the perfboard to solder on the bottom side, the dogleg must now go right ... DOH! 🙄 that'll teach me to spurn PCB's in favour of perfboard for a one off project) and finally got the amps powered up and functioning ... sort of!.
Before I get into teh problems, I am using exactly the circuit layout from the hifi-zen / netlist schematic, with the LM329 as a voltage reference and resistor loading to bias it to ~8mA, and I have not yet inserted C7-10 into the circuit. Also, I replaced R1+R4 with a single 56 ohm 5watt resitor (same for R44+R45).
The first problem is that I am getting about 0.2V relative offset. I matched all the transistors, but somehow forgot to match the critical source resistors, so I know what I need to do there.
The second problem is a little more problematic. As I vary the differential pair bias current to set the absolute offset, if the outputs are within +/- 3.5V of ground the circuit goes unstable, and I get motorboating from the cheap pair of speakers I use for testing, and the lower the magnitude of the absolute offset the faster the frequency of motorboating. At higher or lower absolute offsets the output is silent, and the circuit behaviour is stable. Also, the lower the bias to the better the stability.
Thus, I believe I need the C7-C10 caps for stability. Any suggestions for appropriate values?
Cheers, Terry
What are the recommended values for C7, C8, C9, C10 if they are used, because I think I need to use them?
After two weekends of troubleshooting my non-functional monoblocks, I found my wiring error (somehow forgot that if the wire layout doglegs left when viewed from the top, when you flip over the perfboard to solder on the bottom side, the dogleg must now go right ... DOH! 🙄 that'll teach me to spurn PCB's in favour of perfboard for a one off project) and finally got the amps powered up and functioning ... sort of!.
Before I get into teh problems, I am using exactly the circuit layout from the hifi-zen / netlist schematic, with the LM329 as a voltage reference and resistor loading to bias it to ~8mA, and I have not yet inserted C7-10 into the circuit. Also, I replaced R1+R4 with a single 56 ohm 5watt resitor (same for R44+R45).
The first problem is that I am getting about 0.2V relative offset. I matched all the transistors, but somehow forgot to match the critical source resistors, so I know what I need to do there.
The second problem is a little more problematic. As I vary the differential pair bias current to set the absolute offset, if the outputs are within +/- 3.5V of ground the circuit goes unstable, and I get motorboating from the cheap pair of speakers I use for testing, and the lower the magnitude of the absolute offset the faster the frequency of motorboating. At higher or lower absolute offsets the output is silent, and the circuit behaviour is stable. Also, the lower the bias to the better the stability.
Thus, I believe I need the C7-C10 caps for stability. Any suggestions for appropriate values?
Cheers, Terry