PSU calculation
Please try somebody to explain:
In the thread and on the WIKI-page as well are simultanously indicated two programs for particular calculations, AXE-1 and PSU Designer II (this one inside the AXE-1, too).
Now, my question:
What would explain the difference regarding the transformer voltage, which in my case is 9.85 V true RMS w/o load and some 9.5 V @ 5,7 A, measured practically, wich appairs enough for 12.7 V rail in the spreadsheet and for only 10.2 V by the PSU-program (C-only, Bridge 25 rectifier and 250 mF capacitors).
The difference is over 20% and being near the lower rail limit is disturbing a bit...
Please help to understand,
Laci
Please try somebody to explain:
In the thread and on the WIKI-page as well are simultanously indicated two programs for particular calculations, AXE-1 and PSU Designer II (this one inside the AXE-1, too).
Now, my question:
What would explain the difference regarding the transformer voltage, which in my case is 9.85 V true RMS w/o load and some 9.5 V @ 5,7 A, measured practically, wich appairs enough for 12.7 V rail in the spreadsheet and for only 10.2 V by the PSU-program (C-only, Bridge 25 rectifier and 250 mF capacitors).
The difference is over 20% and being near the lower rail limit is disturbing a bit...
Please help to understand,
Laci
Understanding the AXE spreadsheet
Hi
I am trying to figure out how to size my Aleph-x and dont understand the following numbers that I get when I plug in the voltage and bias into the spreadsheet. Can someone please explain what is going on here?
When I use a bias of 4 amps I get a set of RMS Power into 8,4 and 2 ohm loads but if I change this to 5 amps, the change in RMS power is disproportionate...??
If my speakers are 6 ohms, would it be better to use the 5A bias rather than the 4amp?
Voltage 16
Bias 4
Ac current gain 50%
Number of fets 8
Peak current 4
Power 8 Ohms (RMS) 49
Power 4 Ohms (RMS) 32
Power 2 Ohms (RMS) 16
Dissipation for one channel 128
Dissipation per fet 16
Transformer secondaries standard 11.84
-----------------------------------------------------------------------
Voltage 16 V
Bias 5 A
Ac current gain 50%
Number of fets 8
Peak current 5 A
Power 8 Ohms (RMS) 49 W
Power 4 Ohms (RMS) 50 W
Power 2 Ohms (RMS) 25 W
Dissipation for one channel 160 W
Dissipation per fet 20 W
Transformer secondaries standard 11.84 V
Hi
I am trying to figure out how to size my Aleph-x and dont understand the following numbers that I get when I plug in the voltage and bias into the spreadsheet. Can someone please explain what is going on here?
When I use a bias of 4 amps I get a set of RMS Power into 8,4 and 2 ohm loads but if I change this to 5 amps, the change in RMS power is disproportionate...??
If my speakers are 6 ohms, would it be better to use the 5A bias rather than the 4amp?
Voltage 16
Bias 4
Ac current gain 50%
Number of fets 8
Peak current 4
Power 8 Ohms (RMS) 49
Power 4 Ohms (RMS) 32
Power 2 Ohms (RMS) 16
Dissipation for one channel 128
Dissipation per fet 16
Transformer secondaries standard 11.84
-----------------------------------------------------------------------
Voltage 16 V
Bias 5 A
Ac current gain 50%
Number of fets 8
Peak current 5 A
Power 8 Ohms (RMS) 49 W
Power 4 Ohms (RMS) 50 W
Power 2 Ohms (RMS) 25 W
Dissipation for one channel 160 W
Dissipation per fet 20 W
Transformer secondaries standard 11.84 V
Hi Laci,
One difference is that with a bridge rectifier (full-wave rectification) two diodes are in the AC path causing a voltage drop of 2 X 0.7 Volts = 1.4 Volts instead of the the asumed single diode ((dual-) half-wave rectification, 0.7 Volt drop) in the spreadsheet.
Furthermore it is stated in the spreadsheet that losses in the filtering are not accounted for in the used calculation.
Use the transformer voltage as indicated in the spreadsheet as a rough estimate for the transformer voltage and calculate a more exact value with PSU-Designer wich is much more elaborate (and includes losses in the filtering) than the simple formula used in AXE-1.
One difference is that with a bridge rectifier (full-wave rectification) two diodes are in the AC path causing a voltage drop of 2 X 0.7 Volts = 1.4 Volts instead of the the asumed single diode ((dual-) half-wave rectification, 0.7 Volt drop) in the spreadsheet.
Furthermore it is stated in the spreadsheet that losses in the filtering are not accounted for in the used calculation.
Use the transformer voltage as indicated in the spreadsheet as a rough estimate for the transformer voltage and calculate a more exact value with PSU-Designer wich is much more elaborate (and includes losses in the filtering) than the simple formula used in AXE-1.
Dual PSU / single diode voltage drop
Laci,
You kind of "double use" the already present "other" secondairy winding of a dual (pos. and neg.) supply for the second diode.
So you only need one transformer with one centre-tapped winding (or two secondairies connected together) and 4 diodes (or one 4 diode-bridge) to create a dual (pos. ad neg.) supply.
It's a common "trick" used in many dual voltage powersupply circuits.
You save one diodebridge and a 0.7 Volt voltage drop in this way.
The drawback is that it only works with a common "0-Volt" / Ground.
Look on the net and you will find examples/diagrams.
Good luck with your Aleph(X) experiments.
Laci,
You kind of "double use" the already present "other" secondairy winding of a dual (pos. and neg.) supply for the second diode.
So you only need one transformer with one centre-tapped winding (or two secondairies connected together) and 4 diodes (or one 4 diode-bridge) to create a dual (pos. ad neg.) supply.
It's a common "trick" used in many dual voltage powersupply circuits.
You save one diodebridge and a 0.7 Volt voltage drop in this way.
The drawback is that it only works with a common "0-Volt" / Ground.
Look on the net and you will find examples/diagrams.
Good luck with your Aleph(X) experiments.
Byteboy!
Thank you once again: I omitted to think to that solution!
You are perfectly right; the remaining disappaired 1.8 V (the 2,5 V difference between the mentioned two methods minus your discovered 0.7 V) is others' duty to be explained...
I am going to realise the A-X at the original power level and 4 x IRF604 (TO-220) per channel only. Their tranconductance is more close to the usually used TO-247 types than the 540's. The Cgs is also lower. As I could procure 36 from them second hand and very cheap, by rotation I hope I'll be able to select good quartets for low offset values.
Also, for the aimed power level the 44 x 12 000 uF shall be more than enough. The only one transformer is my main problem: it is over 500 VA (enough as power for stereo), made for inverter use (12 V primaries and 230 V output), and although very heavy and well finished, in reverse mode 2 x 9.85 V only. With huge capacitor batteries I thought, however, at more rail voltage than 10.2 V (powered totally with only 5-5.5 A; at this level the measured AC was, as mentioned in my first post, 9.5 V). At this value the whole project can break down. It were much better for me with by the AXE-1 promised 12.7 V...
And your opinion: would have any advantage to split the existing capacitors in 4 instead of 2 blocks (separated rail batteries for L and R channels)? If yes, going farther on would have an ameliotating effect putting separated diodes (after your topology) for them (nodes on the trafo instead of rectifier output)? Or both of theese are with no or minor effect?
(For my pleasure to use the existing transformer I drop the monoblocks.)
Regards,
Laci
Thank you once again: I omitted to think to that solution!
You are perfectly right; the remaining disappaired 1.8 V (the 2,5 V difference between the mentioned two methods minus your discovered 0.7 V) is others' duty to be explained...
I am going to realise the A-X at the original power level and 4 x IRF604 (TO-220) per channel only. Their tranconductance is more close to the usually used TO-247 types than the 540's. The Cgs is also lower. As I could procure 36 from them second hand and very cheap, by rotation I hope I'll be able to select good quartets for low offset values.
Also, for the aimed power level the 44 x 12 000 uF shall be more than enough. The only one transformer is my main problem: it is over 500 VA (enough as power for stereo), made for inverter use (12 V primaries and 230 V output), and although very heavy and well finished, in reverse mode 2 x 9.85 V only. With huge capacitor batteries I thought, however, at more rail voltage than 10.2 V (powered totally with only 5-5.5 A; at this level the measured AC was, as mentioned in my first post, 9.5 V). At this value the whole project can break down. It were much better for me with by the AXE-1 promised 12.7 V...
And your opinion: would have any advantage to split the existing capacitors in 4 instead of 2 blocks (separated rail batteries for L and R channels)? If yes, going farther on would have an ameliotating effect putting separated diodes (after your topology) for them (nodes on the trafo instead of rectifier output)? Or both of theese are with no or minor effect?
(For my pleasure to use the existing transformer I drop the monoblocks.)
Regards,
Laci
If I understand your last questions correctly:
It makes no difference if you use 4 separate diodes or a diode-bridge rectifier, exept maybe that a particular (better quality) diode could have a little lower voltage drop (say 0.6 Volt instead of the 0.7 Volt for an average diode-bridge rectifier) which in your case could only help, being so "close to the edge"......
It is usually thought that separate power-supplies for different channels/amplifiers is better because (heavy-) load variations for one channel do not influence the other channel in that way.
But since you would be feeding the two capacitor banks for the two stereo channels from the same secondairy winding (using separate diodes) the advantage will indeed be limmited.
One other thing worth mentioning is that the MOSFETs you intend to use shoud be suitable/designed for this low supply voltage.
Somewhere in the forum it is mentioned that eg. the IRFP044 is better suited to be used at lower supply voltages of abt. 12-15 Volts than eg. an IRFP9240 which should be operated at abt. 25 Volts.
You should check this with the specs of your MOSFET's.
It makes no difference if you use 4 separate diodes or a diode-bridge rectifier, exept maybe that a particular (better quality) diode could have a little lower voltage drop (say 0.6 Volt instead of the 0.7 Volt for an average diode-bridge rectifier) which in your case could only help, being so "close to the edge"......
It is usually thought that separate power-supplies for different channels/amplifiers is better because (heavy-) load variations for one channel do not influence the other channel in that way.
But since you would be feeding the two capacitor banks for the two stereo channels from the same secondairy winding (using separate diodes) the advantage will indeed be limmited.
One other thing worth mentioning is that the MOSFETs you intend to use shoud be suitable/designed for this low supply voltage.
Somewhere in the forum it is mentioned that eg. the IRFP044 is better suited to be used at lower supply voltages of abt. 12-15 Volts than eg. an IRFP9240 which should be operated at abt. 25 Volts.
You should check this with the specs of your MOSFET's.
I'm back!
Hello all, its been a while, but i'm finally back... i've had a busy last couple of months and hopefully plan on finishing my AX! (heheh)...
Refresher:
My amp was troubleshooted by chad and a couple others, i was told my input stage was working correctly, but my output stage wasn't troubleshootable until i used a real Power supply (instead of this 1 amp bench psu)...
My first question: With default part list parts (values etc), how many amps will *one* board pull? Build a second power supply for each channel or one with double the power capabilities of the first... I read back, i might do a CLC filter with one of the Hammond choke's that someone (chad?) suggests... how many volts get lost over the CLC network? over the bridge rectifier? Thanks alot!
Thanks in advance to my dumb questions, i want to get this thing running!
Brad
Hello all, its been a while, but i'm finally back... i've had a busy last couple of months and hopefully plan on finishing my AX! (heheh)...
Refresher:
My amp was troubleshooted by chad and a couple others, i was told my input stage was working correctly, but my output stage wasn't troubleshootable until i used a real Power supply (instead of this 1 amp bench psu)...
My first question: With default part list parts (values etc), how many amps will *one* board pull? Build a second power supply for each channel or one with double the power capabilities of the first... I read back, i might do a CLC filter with one of the Hammond choke's that someone (chad?) suggests... how many volts get lost over the CLC network? over the bridge rectifier? Thanks alot!
Thanks in advance to my dumb questions, i want to get this thing running!
Brad
Lieber Byteboy!
C'est magnifique!
You became my external intelligence... I would feel better in the opposed situation.
Have you already seen such solutions by A-class projects? Or this will be a prototype? Don't take it bad, it doesn't disturb me, only to know. The idea is marvellous, modifying it a bit I can eventually change my mind and start for a higher powered version (having 4 pieces of 0.3 C/W heatsinks). Anyway, I will see practically the real measured values with a simple C filter, and if the PSU-program gave the "good" result (too low rails), will transfigure the PSU. Where come in your simulation the 50 mOhms for the capacitor batteries from?
And the former question again: as the ripple voltage in the example after the first RC is already low, wouldn't be an even better solution after the multiplier to split the rails in two parallel RCs (R+60 mF each) for L+R channels?
Best regards,
Laci
C'est magnifique!
You became my external intelligence... I would feel better in the opposed situation.
Have you already seen such solutions by A-class projects? Or this will be a prototype? Don't take it bad, it doesn't disturb me, only to know. The idea is marvellous, modifying it a bit I can eventually change my mind and start for a higher powered version (having 4 pieces of 0.3 C/W heatsinks). Anyway, I will see practically the real measured values with a simple C filter, and if the PSU-program gave the "good" result (too low rails), will transfigure the PSU. Where come in your simulation the 50 mOhms for the capacitor batteries from?
And the former question again: as the ripple voltage in the example after the first RC is already low, wouldn't be an even better solution after the multiplier to split the rails in two parallel RCs (R+60 mF each) for L+R channels?
Best regards,
Laci
The 0.05 Ohm was a guess, just to have the program going, you will have to check that with the specs of the actual capacitors you have. This figure could even be lower.
As for the separate banks for left and right channels, like I already said in the previuos answer, I think the effect will be limmited, since you will feed them off of the same secondairy winding.
But you can and should try this, that's what makes this hobby so interesting!!
I have no further experience with voltage doubling in high current applications and Class A and don't know if this is done before, as far as I know I've not seen this on the forum before.
You might be right that you are on new territory here .......
One good thing might be that Class A draws a fairly constant high current, which I think could be a good thing for dimensioning a high current voltage doubler.
I hope other members can and will comment on this.
One other thing is the impedance of the speaker you have or intend to use.
With the 10.2 Volt supply you will be (voltage-) limmited to low speaker impedances, say 4 Ohms or so and lower, to generate a reasonable power into.
Did you check the specs of your MOSFET's for low voltage use?
Anyway, keep us posted about any progess you make!!
Succes with your experiments!!
As for the separate banks for left and right channels, like I already said in the previuos answer, I think the effect will be limmited, since you will feed them off of the same secondairy winding.
But you can and should try this, that's what makes this hobby so interesting!!
I have no further experience with voltage doubling in high current applications and Class A and don't know if this is done before, as far as I know I've not seen this on the forum before.
You might be right that you are on new territory here .......
One good thing might be that Class A draws a fairly constant high current, which I think could be a good thing for dimensioning a high current voltage doubler.
I hope other members can and will comment on this.
One other thing is the impedance of the speaker you have or intend to use.
With the 10.2 Volt supply you will be (voltage-) limmited to low speaker impedances, say 4 Ohms or so and lower, to generate a reasonable power into.
Did you check the specs of your MOSFET's for low voltage use?
Anyway, keep us posted about any progess you make!!
Succes with your experiments!!
Aleph X
Dear All,
There is anybody that have patience for me??
I have realized the first Aleph X High power version with 8 IRF044's for side channel and 22 Vcc power supply, and I will found the following problems..
1. The Aleph is symmetrical and the output plus side seems to work in a right way for me is possible to set the DC offset and the absolute DC offset.
2. BUT, if i check the OUT_minus right side I have the following behaviour:
@. On the gate the Voltage measured is the same of VCC power supply.
@. On the OUT_minus speaker I get 17 Vcc and on resistor of 33 ohm became very hot.
@. On the source tesistor I got 0 Volt and no 0,5 Vcc for example like as in the left side of my amplifier.
Please Help me
Franco
Dear All,
There is anybody that have patience for me??
I have realized the first Aleph X High power version with 8 IRF044's for side channel and 22 Vcc power supply, and I will found the following problems..
1. The Aleph is symmetrical and the output plus side seems to work in a right way for me is possible to set the DC offset and the absolute DC offset.
2. BUT, if i check the OUT_minus right side I have the following behaviour:
@. On the gate the Voltage measured is the same of VCC power supply.
@. On the OUT_minus speaker I get 17 Vcc and on resistor of 33 ohm became very hot.
@. On the source tesistor I got 0 Volt and no 0,5 Vcc for example like as in the left side of my amplifier.
Please Help me
Franco
Aleph X
Hello at ALL
We have a very noise problems on Aleph-X, I hope You have more seconds to dedicated on my questions, and give me a light for solve it.
1. I have realized a couple of Aleph X, with 8 IRFP044 for each channel, and 22Volt of power supply and a 0,39 ohm like as source resistor.
2. When I turn on the power aplifier with a stabilized power supply I see at 11 Volt a 3 A of consuption, than my power supply goes in a limitation 3 amper per side +/-22Vcc.
3. Other, on the output +/-I got 5 Vcc at 11 Vcc.
4. Meanwhile in the other amp. the beahaviour is different I've half side like as OUT PLUS that work properly, infact 2,5A, is possible to set the BIAS to 0Vcc, while the OUT_MINUS when is supplayed my power supply goes in limitation, and I got on the gate resistors OUT minus the 22 Vcc instead of 4,5 Vcc like as in the other side.
5. About the consuption I'm expected 2.70 A per side.
6. The mosfet are matched following Your article we have put the same VGS for branch, e.g. I have 4x4,17, 4x4,23, ecc.. And for bjt I have founded a MPSA18 the same common transistors used in the Aleph amp.
7.Now I don't know what's up in my aplifier,
If You have a little Idea is appreciated
Best Regards
Franco
Hello at ALL
We have a very noise problems on Aleph-X, I hope You have more seconds to dedicated on my questions, and give me a light for solve it.
1. I have realized a couple of Aleph X, with 8 IRFP044 for each channel, and 22Volt of power supply and a 0,39 ohm like as source resistor.
2. When I turn on the power aplifier with a stabilized power supply I see at 11 Volt a 3 A of consuption, than my power supply goes in a limitation 3 amper per side +/-22Vcc.
3. Other, on the output +/-I got 5 Vcc at 11 Vcc.
4. Meanwhile in the other amp. the beahaviour is different I've half side like as OUT PLUS that work properly, infact 2,5A, is possible to set the BIAS to 0Vcc, while the OUT_MINUS when is supplayed my power supply goes in limitation, and I got on the gate resistors OUT minus the 22 Vcc instead of 4,5 Vcc like as in the other side.
5. About the consuption I'm expected 2.70 A per side.
6. The mosfet are matched following Your article we have put the same VGS for branch, e.g. I have 4x4,17, 4x4,23, ecc.. And for bjt I have founded a MPSA18 the same common transistors used in the Aleph amp.
7.Now I don't know what's up in my aplifier,
If You have a little Idea is appreciated
Best Regards
Franco
A L E P H X
After 3 days, I have found why my Aleph X didn't worked.
1. main problem it has been the MPSA 18, with resistors R11 & R33, I replace them with 4,7K, and the MPSA with BC550C.
2. Now I'm able to set the dc offset with a 2,5 A per side of consumption.
3. I'm wondering why I see on the source resistor minus side for e.g. that give me 350 mV, while the plus side is 70 mV circa. I have checked also that the amplifier works, or maybe now it's sound.
4. Is possible that there is among the 8 044's some not matched?
5. Whay if I touch the resistor R11 & R33 the offset is not stable? it is correct, also I've put a 1nf between CB.
6. Last, Why is some conditions if I have a very good DC Offset the consuption goes under 1A.
Thanks in advance for You suggestions
After 3 days, I have found why my Aleph X didn't worked.
1. main problem it has been the MPSA 18, with resistors R11 & R33, I replace them with 4,7K, and the MPSA with BC550C.
2. Now I'm able to set the dc offset with a 2,5 A per side of consumption.
3. I'm wondering why I see on the source resistor minus side for e.g. that give me 350 mV, while the plus side is 70 mV circa. I have checked also that the amplifier works, or maybe now it's sound.
4. Is possible that there is among the 8 044's some not matched?
5. Whay if I touch the resistor R11 & R33 the offset is not stable? it is correct, also I've put a 1nf between CB.
6. Last, Why is some conditions if I have a very good DC Offset the consuption goes under 1A.
Thanks in advance for You suggestions