HI
Me again , now I did adjust all 3 trim pot to the another end and that lower the power around 6A .
But I have another problem to .I have 2.7V offset when the amp cold , and when it warm up it goes down until 1.8V .
Al the mosfets were matched , transistors were matched .
I don't know what else I can do .
Tomorrow I will use a 12mF Sollen capacitor on the speakers terminal to see at least if it works . Now is to late to try .
Please HELP me so I can finish the amp .It cost me at least $1000CA the parts , and twice that much the work to put it together .
It look nice but that s it unfortunately .
Regards
Me again , now I did adjust all 3 trim pot to the another end and that lower the power around 6A .
But I have another problem to .I have 2.7V offset when the amp cold , and when it warm up it goes down until 1.8V .
Al the mosfets were matched , transistors were matched .
I don't know what else I can do .
Tomorrow I will use a 12mF Sollen capacitor on the speakers terminal to see at least if it works . Now is to late to try .
Please HELP me so I can finish the amp .It cost me at least $1000CA the parts , and twice that much the work to put it together .
It look nice but that s it unfortunately .
Regards
Hi Gabor,
This is a follow up on William's post. If the 2.7V to 1.8V
offset you're getting is from out+ to ground or out- to ground
(ie. absolute offset) then there's nothing to worry about.
(In fact, it seems reasonably good.)
The offset that your speakers will see is the relative offset,
ie, the voltage you measure between the out+ and out-.
What are you getting there?
Cheers,
Dennis
This is a follow up on William's post. If the 2.7V to 1.8V
offset you're getting is from out+ to ground or out- to ground
(ie. absolute offset) then there's nothing to worry about.
(In fact, it seems reasonably good.)
The offset that your speakers will see is the relative offset,
ie, the voltage you measure between the out+ and out-.
What are you getting there?
Cheers,
Dennis
HI
Thanks for the answer .
When I turn on the amplifier I have 2.7V offset between the speaker terminal , between the + & -
When the amplifier warms up the offset goes done to 1.8V .
These problem exist at both channel.
I dont know what I can do , all the power mosfets were matched by Kristijan , but I double matche them . All 8 mosfet mesure inside100mV.
All the drives mosfets and transisors were mathed by me .They has the same value .
Would you please help.Can I try to connect the amplifier to the speakers using a 10uF capacitor .
At least to see if it works .
Regards
Thanks for the answer .
When I turn on the amplifier I have 2.7V offset between the speaker terminal , between the + & -
When the amplifier warms up the offset goes done to 1.8V .
These problem exist at both channel.
I dont know what I can do , all the power mosfets were matched by Kristijan , but I double matche them . All 8 mosfet mesure inside100mV.
All the drives mosfets and transisors were mathed by me .They has the same value .
Would you please help.Can I try to connect the amplifier to the speakers using a 10uF capacitor .
At least to see if it works .
Regards
HI
I'm sorry , I forget to let you know when first I powered up the amp I had over 6V offset .
Now I adjust the trim pot in the middle one (200R) to another end and the offset now 2.7V when the amp cold .
Or 1.8V when the amp warms up.
The problem now I can't adjust more to bring done the offset close to 0V .
I adjusted the another two trim pots to to another end because the bias was very high .
At first the amp draw 7A but now after I adjust the 50K trim pots to another end it draws 5.5A.
I think that is OK , my problem right now the high offset .
Regards
I'm sorry , I forget to let you know when first I powered up the amp I had over 6V offset .
Now I adjust the trim pot in the middle one (200R) to another end and the offset now 2.7V when the amp cold .
Or 1.8V when the amp warms up.
The problem now I can't adjust more to bring done the offset close to 0V .
I adjusted the another two trim pots to to another end because the bias was very high .
At first the amp draw 7A but now after I adjust the 50K trim pots to another end it draws 5.5A.
I think that is OK , my problem right now the high offset .
Regards
HI
Unfortunately more bad news . Today morning I turned on the amp and after a couple minutes the transformer started to buzz .
It give a sound like when is over loaded . Only one channel connected to the power supply . But with both channel does the same .
I use 1.5KVA 2X18V transformer from Plitron .
I still don't know if the 6A is it to much measured between the power supply and the pc board on the positive .
Can some one please let me know .
If that is correct I have to call Plitron to discus the transformer .
Please help !!!!
Regards
Unfortunately more bad news . Today morning I turned on the amp and after a couple minutes the transformer started to buzz .
It give a sound like when is over loaded . Only one channel connected to the power supply . But with both channel does the same .
I use 1.5KVA 2X18V transformer from Plitron .
I still don't know if the 6A is it to much measured between the power supply and the pc board on the positive .
Can some one please let me know .
If that is correct I have to call Plitron to discus the transformer .
Please help !!!!
Regards
Hi,
if the offset you see is between plus and minus. What offset do you have between +out and ground and -out and ground?
You have to set this absolute offset to zero first. Before doing anything else.
Then match the bias for both halves by measuring the voltage drop over the power fet source resistors and make it equal
You´ll have to adjust the absolute offset everytime you change the bias!
If the diff offset stays that big your input dif pair isn´t matched well enough. Are they thermally coupled?
A buzzing transformer is not unusual (but not nice).
William
if the offset you see is between plus and minus. What offset do you have between +out and ground and -out and ground?
You have to set this absolute offset to zero first. Before doing anything else.
Then match the bias for both halves by measuring the voltage drop over the power fet source resistors and make it equal
You´ll have to adjust the absolute offset everytime you change the bias!
If the diff offset stays that big your input dif pair isn´t matched well enough. Are they thermally coupled?
A buzzing transformer is not unusual (but not nice).
William
HI
I tried to adjust the bias but the best I can do is 1.8V after the amp warms up .
When is cold it is around 2.7V .
I want to know how much power draw each side , I afraid because the way to high power it will blow up.
Now the transformer buzz , unfortunately so loud I can't leave the power on .
It give the same sound like when you turn on the amp and charges the capacitors for a couple second .
These happen after 5 minutes and the noise is continuous , and I tested bot side one by one and it the same problem .
I will go over on the board second time if I can find some problem .
All the power mosfet were double matched ,by Kristijan and by me .
I think the 6A is way to much , measured between the board and the power supply on the positive .
IF I'm right it supposed to be 3A at the + and 3A at the - .So all together 6A .
If the power way to high it destroy everithig .
Please somebody let me know what is the correct power ...
Regards
I tried to adjust the bias but the best I can do is 1.8V after the amp warms up .
When is cold it is around 2.7V .
I want to know how much power draw each side , I afraid because the way to high power it will blow up.
Now the transformer buzz , unfortunately so loud I can't leave the power on .
It give the same sound like when you turn on the amp and charges the capacitors for a couple second .
These happen after 5 minutes and the noise is continuous , and I tested bot side one by one and it the same problem .
I will go over on the board second time if I can find some problem .
All the power mosfet were double matched ,by Kristijan and by me .
I think the 6A is way to much , measured between the board and the power supply on the positive .
IF I'm right it supposed to be 3A at the + and 3A at the - .So all together 6A .
If the power way to high it destroy everithig .
Please somebody let me know what is the correct power ...
Regards
HI
I tested the offset between the ground and + it is over 5V .
Between the ground and the -2.7V .All these when the after a couple minutes when the amp is still cold .
No no longer possible to leave the power on to warm up the amp because the transformer start buzz very loud .
Now I'm going to remove the pc boards and look for possibility of mistakes .
If I find that good news , if not unfortunately that will be the end of the AX .
Regards
I tested the offset between the ground and + it is over 5V .
Between the ground and the -2.7V .All these when the after a couple minutes when the amp is still cold .
No no longer possible to leave the power on to warm up the amp because the transformer start buzz very loud .
Now I'm going to remove the pc boards and look for possibility of mistakes .
If I find that good news , if not unfortunately that will be the end of the AX .
Regards
Gaborbela, go to ebay and purchase a cheap variac. They're under a hundred dollars and worth every penny you spend for the peace of mind they give you!!!
You're writing makes you sound like you're in panic mode. If that's the case, then STOP. Rest your mind. Take a couple days off and gently mull over the schematics and the concepts that make the AX work. Go back to square one if you have to. Read as many post as you can in the AX threads.
Check your pcb for stray wire filaments, blobs of solder, etc. Do an unpowered check of the resistance of one side of the pcb against the other to see how well they match. Check one pcbs resistance readings against the other channel as well. Record these readings and then ponder.
John
You're writing makes you sound like you're in panic mode. If that's the case, then STOP. Rest your mind. Take a couple days off and gently mull over the schematics and the concepts that make the AX work. Go back to square one if you have to. Read as many post as you can in the AX threads.
Check your pcb for stray wire filaments, blobs of solder, etc. Do an unpowered check of the resistance of one side of the pcb against the other to see how well they match. Check one pcbs resistance readings against the other channel as well. Record these readings and then ponder.
John
Hi all,
I've been building a pair of aleph-x's over the past few weeks and have got a problem.
First off, I'm aiming for 40-50W into 8ohm, i got ~16V rails, 4A bias, 4 fets per amp, 2*12VAC transformer secondaries on a 300VA transformer for each amp with 100,000uF caps per rail which is all working very well. I've designed my own circuit board and chassis consisting of 2 large heatsinks that run both lengths of the case sides, see quick picture of it here
Powering up I can adjust the bias just fine and have 4.4v over the 0.22ohm source resistors, but then the problem I'm having is that I cannot fix the absolute DC offset with the 3rd pot, both sides measure ~ -15.5V for the entire travel of the pot. I've replaced the differential input and current source fets thinking it is probably them, which didn't help. All parts were hand matched very well
Is there anything I can measure to see what it could be?
Thanks,
Dan
I've been building a pair of aleph-x's over the past few weeks and have got a problem.
First off, I'm aiming for 40-50W into 8ohm, i got ~16V rails, 4A bias, 4 fets per amp, 2*12VAC transformer secondaries on a 300VA transformer for each amp with 100,000uF caps per rail which is all working very well. I've designed my own circuit board and chassis consisting of 2 large heatsinks that run both lengths of the case sides, see quick picture of it here
Powering up I can adjust the bias just fine and have 4.4v over the 0.22ohm source resistors, but then the problem I'm having is that I cannot fix the absolute DC offset with the 3rd pot, both sides measure ~ -15.5V for the entire travel of the pot. I've replaced the differential input and current source fets thinking it is probably them, which didn't help. All parts were hand matched very well
Is there anything I can measure to see what it could be?
Thanks,
Dan
Hi Dan,
-15.5 volt means the output fets are completely open. This means that the current through the current source is too high.
You can measure it by looking at the voltage over the drain resistors from the input fets.
Try to raise the value of the resistor parallel to the 3th pot and turn the pot to max resistance.
This should do the job.
William
-15.5 volt means the output fets are completely open. This means that the current through the current source is too high.
You can measure it by looking at the voltage over the drain resistors from the input fets.
Try to raise the value of the resistor parallel to the 3th pot and turn the pot to max resistance.
This should do the job.
William
Hi David,
the McMillan´s:
they are connected between the outputs (+ and -) and the sources of the input diff pair (R46 R47)
they are between 2k2 and about 10k
they form a feedback loop
suppose the outputs absolute output becomes positive. Now the current through the diff pair will become higher and the voltage over the drain resistors (R23 / R25) becomes higher.
Now the output fets will open up a bit (Rds gets lower) and the dc voltage at the output becomes lower.
It works the same way the other way round.
I tried different R´s starting from 2k7 and ending up with 10k. The higher the value is the better the sound quality will be and the higher the absolute dc startup value.
hope this simplistic explanation helps,
William
the McMillan´s:
they are connected between the outputs (+ and -) and the sources of the input diff pair (R46 R47)
they are between 2k2 and about 10k
they form a feedback loop
suppose the outputs absolute output becomes positive. Now the current through the diff pair will become higher and the voltage over the drain resistors (R23 / R25) becomes higher.
Now the output fets will open up a bit (Rds gets lower) and the dc voltage at the output becomes lower.
It works the same way the other way round.
I tried different R´s starting from 2k7 and ending up with 10k. The higher the value is the better the sound quality will be and the higher the absolute dc startup value.
hope this simplistic explanation helps,
William
toroidal
It seems everyone uses a toroidal power transformer for the Aleph x
My intention is not to start a debate between EI and toroidal but simply what are the advantages besides low EMI.
Also it seems I am having a difficult time finding a suitable toroidal
I need 300va @ 12-0-12. I know of victoria Magnetics, are there any other good suppliers ?
J
It seems everyone uses a toroidal power transformer for the Aleph x
My intention is not to start a debate between EI and toroidal but simply what are the advantages besides low EMI.
Also it seems I am having a difficult time finding a suitable toroidal
I need 300va @ 12-0-12. I know of victoria Magnetics, are there any other good suppliers ?
J