Yesterday, I looked an another No3. Millennium for dc-offset (no any input, without any load on output, amp was warming very well).
Curiously, has the same behaviour like yours.
Left channel - (25-26) mVdc
Right channel 6-7 mVdc
Of course there is no any concern about left channel, it is under of 50mVdc, but this difference probably caused from differential section (not same pairs to BC550c/BC560c).
Have you measure the quiescent current?
Curiously, has the same behaviour like yours.
Left channel - (25-26) mVdc
Right channel 6-7 mVdc
Of course there is no any concern about left channel, it is under of 50mVdc, but this difference probably caused from differential section (not same pairs to BC550c/BC560c).
Have you measure the quiescent current?
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There are three ways to obtain lowest value of the unwanted DC offset at the output:
1) additional offset servo
2) selecting the input transistors of identical Vbe
3) introducing of a potentiometer between the input base leads and supply voltage (good regulated - without significant hum)
A fourth way would be to avoid a dc coupled signal pad.
To archive this it is necessary among other things the remove of the transformer secundary windings from GND. Unfortunately only possible without trouble, if there is a dual monaural power supply include two independend main transformers.
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The Aaron No3 Millennium is not a DC coupled amplifier.
The transformer secondary windings are not connected to chassis.
One channel gives excellent output offset.
The other channel gives a higher output offset that varies with Rs. This is not a servo problem nor is it a non selected Vbe issue.
The transformer secondary windings are not connected to chassis.
One channel gives excellent output offset.
The other channel gives a higher output offset that varies with Rs. This is not a servo problem nor is it a non selected Vbe issue.
Obviously you have the complete schematic (in the schema of post #1 I can not find connecting of the transformer leads).
Can you upload this?
BTW - GND and chassis has not necessarily identical potential. But speaker GND and transformer secundary winding GND mostly uses the same potential. Thus there are mostly DC coupling between loudspeaker and amplifier.
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Not easy.
The back of the amplifier has the double insulated ClassII concentric squares symbol.
But, on the inside the IEC socket clearly has the PE connected directly to Chassis.
Neither the Speaker Return, nor the Audio Ground, nor the Signal Return, are connected to chassis and as a result these same are not connected to Ground/Earth/PE.
The back of the amplifier has the double insulated ClassII concentric squares symbol.
But, on the inside the IEC socket clearly has the PE connected directly to Chassis.
Neither the Speaker Return, nor the Audio Ground, nor the Signal Return, are connected to chassis and as a result these same are not connected to Ground/Earth/PE.
I see. This is usual here in Germany (otherwise there comes up so called ground loops). When I say "GND" (= ground or mass, the inverted T icon), I don't mean the chassis resp. the mains earth. "GND" means for me the GND behind the secundary side (by Naim Audio mostly realized as star point on their PCB)
Chassis and mains earth means two additional lines (one shorter and one even more shorter) below the inverted T icon.
If speaker return and the return of the secundary windings have the same potential, I asume dc coupled loudspeaker. Consequence is, that I must have a relay contact for DC protect or there is the risc of damaged speakers in error case.
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If German manufacturers are doing this then German interpretation of ClassII is quite different to UK interpretation.
As far as I have learned, all double insulated or ClassII equipment must NOT be connected to PE.
Here in the UK, properly supplied ClassII equipment that has the IEC socket uses only the two pin version of the socket and the cable plug has the third pin receptacle blanked off. These modified bits of hardware to to prevent inadvertant miss-connection to mains of IEC socketed equipment.
As far as I have learned, all double insulated or ClassII equipment must NOT be connected to PE.
Here in the UK, properly supplied ClassII equipment that has the IEC socket uses only the two pin version of the socket and the cable plug has the third pin receptacle blanked off. These modified bits of hardware to to prevent inadvertant miss-connection to mains of IEC socketed equipment.
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I don't understand, what the safety requirements for power supply/transformer insulation class (class II or double insulated electrical appliance) have to do with the kind of loudspeaker coupling to the power amp output (DC coupling/AC coupling) ?
I would say, we are "Off-Topic".
My advices by post #22 I obviously need not to be take back.
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You asked questions that appeared to be unrelated to what we were discussing.
I did my best to answer or point out why I couldn't answer those off topic questions.
I did my best to answer or point out why I couldn't answer those off topic questions.
Yesterday, I measured the quiescent current.
It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mV quiescent current.
I done an acoustic and lab test and I think so, that the best is btw 6-15mV dropping!
I tried until 130-140mV quiescent.
Final, I set up to ≈ 50mV quiescent current.
(I have a pcb with revision Ver.1.1)
It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mV quiescent current.
I done an acoustic and lab test and I think so, that the best is btw 6-15mV dropping!
I tried until 130-140mV quiescent.
Final, I set up to ≈ 50mV quiescent current.
(I have a pcb with revision Ver.1.1)
Andrew, although I do not understand what mixing unit.
I wrote:
"It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mV quiescent current"
I mean that, there was a dc drop voltage on emitter resistor (0.22 Ohm) about 7.2mV.
Quiescent Current=0.0072/0.22≈35mV
Totaly, I set up the QC at 50mV, it is 10+mV about.
I would appreciate if you measure the QC at your amp.
Procedure of measuring
1) Very well warming and playing for 30 min in stress mode (1/3 of amp power for 30 min. I used a dummy load 8 Ohm for this testing)
2) Without any input or output load, I measured across the 0.22 emitter resistor (5W) of MJ15003 or MJ15004) the dropping dc voltage.
I wrote:
"It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mV quiescent current"
I mean that, there was a dc drop voltage on emitter resistor (0.22 Ohm) about 7.2mV.
Quiescent Current=0.0072/0.22≈35mV
Totaly, I set up the QC at 50mV, it is 10+mV about.
I would appreciate if you measure the QC at your amp.
Procedure of measuring
1) Very well warming and playing for 30 min in stress mode (1/3 of amp power for 30 min. I used a dummy load 8 Ohm for this testing)
2) Without any input or output load, I measured across the 0.22 emitter resistor (5W) of MJ15003 or MJ15004) the dropping dc voltage.
Sorry Andrew, you have absolute true.
Ι wrote the same unit (mV) for current and voltage! Twice the same wrong!
Now I understood, why you write me before "You are mixing up units of measurement"
I correct my previous message to the right:
Yesterday, I measured the quiescent current.
It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mA quiescent current.
...
Finaly, I set up to ≈ 50mA quiescent current.
(I have a pcb with revision Ver.1.1)
I would appreciate if you measure the QC at your amp, Andrew.
Ι wrote the same unit (mV) for current and voltage! Twice the same wrong!
Now I understood, why you write me before "You are mixing up units of measurement"
I correct my previous message to the right:
Yesterday, I measured the quiescent current.
It had a drop voltage on emitter resistor about 7.2mV... ≈ 33mA quiescent current.
...
Finaly, I set up to ≈ 50mA quiescent current.
(I have a pcb with revision Ver.1.1)
I would appreciate if you measure the QC at your amp, Andrew.
Hi,
~1mVdc at cold start up.
Rising to ~8mVdc after 20 mins warm up.
Take care. I blew another channel just touching +IN (the same channel that had the odd output offset). This is the second time.
Before it blew, I found that the collectors of the outputs had 1.1mVdc between them (~+-0.5mVdc ref output).
The good channel showed just 0.1mVdc flickering towards 0.0mVdc occasionally.
~1mVdc at cold start up.
Rising to ~8mVdc after 20 mins warm up.
Take care. I blew another channel just touching +IN (the same channel that had the odd output offset). This is the second time.
Before it blew, I found that the collectors of the outputs had 1.1mVdc between them (~+-0.5mVdc ref output).
The good channel showed just 0.1mVdc flickering towards 0.0mVdc occasionally.
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Thanks for the reply, Andrew.
You wrote me "Take care. I blew another channel just touching +IN (the same channel that had the odd output offset). This is the second time."
1) You meaning the signal (+) input with the phrase "+IN". And what was the equipment that touched "+IN"?
2) Had you a blew on fuse or transistor output (MJ1500Χ)?
I had 2-3 times fusion blew, when the rca male (+) of interconnect cable touched the rca female input (-) when the amp was on and I tried to find the rca input in darkness.
I use a T4A fusion.
You wrote me too "...I found that the collectors of the outputs had 1.1mVdc between them (~+-0.5mVdc ref output).
The good channel showed just 0.1mVdc flickering towards 0.0mVdc occasionally."
I remember the words of a friend who has serviced an Aaaron No3. Millennium before, that this amp had some problems with current.
I will ask him to explain better, maybe to help us.
You wrote me "Take care. I blew another channel just touching +IN (the same channel that had the odd output offset). This is the second time."
1) You meaning the signal (+) input with the phrase "+IN". And what was the equipment that touched "+IN"?
2) Had you a blew on fuse or transistor output (MJ1500Χ)?
I had 2-3 times fusion blew, when the rca male (+) of interconnect cable touched the rca female input (-) when the amp was on and I tried to find the rca input in darkness.
I use a T4A fusion.
You wrote me too "...I found that the collectors of the outputs had 1.1mVdc between them (~+-0.5mVdc ref output).
The good channel showed just 0.1mVdc flickering towards 0.0mVdc occasionally."
I remember the words of a friend who has serviced an Aaaron No3. Millennium before, that this amp had some problems with current.
I will ask him to explain better, maybe to help us.
Amp blown.
I had forgotten what I had done when it was days old.
Did the same thing again, after it has been lying on the shelf for about 3years. I didn't dare connect it to speakers for fear of taking them out as well.
Touched +IN to measure the input voltage with my DMM.
I had forgotten what I had done when it was days old.
Did the same thing again, after it has been lying on the shelf for about 3years. I didn't dare connect it to speakers for fear of taking them out as well.
Touched +IN to measure the input voltage with my DMM.
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