I have always wonder about in wich mode the speaker operating switch should be at when setting the 16mV.
It´s somewhat confusing looking at the specs and then at the procedure.
Is it 16mV in 4 Ohm Mode and 32mV in 8 Ohm mode?
It´s somewhat confusing looking at the specs and then at the procedure.
Is it 16mV in 4 Ohm Mode and 32mV in 8 Ohm mode?
The procedure is as clear as mud to me 😀
The 4/8 ohm setting simply alters the main rail voltage to the outputs and ideally should make no difference to the result. The higher rail setting which I assume is the 8 ohm setting will cause the output stage to run hotter. If the current drifts or drifts more in one setting than the other, then that can be levelled at the design of the amp.
There are some 100 ohm's shown on the circuit connecting the output transistor emitters and as configured serve no purpose so perhaps these are the 100 ohm's mentioned. Perhaps the idea is to get an average current for the parallel pairs of outputs by using the junction of the 100 ohm's as the test points.
A value of 32 mv across each 0.27 ohm sounds a plausible value and would give a current of 118 milliamps per pair. That would fit with the theory but is what they intend. Assuming you have not altered the original settings then I would first see what you actually have across those resistors.
The 4/8 ohm setting simply alters the main rail voltage to the outputs and ideally should make no difference to the result. The higher rail setting which I assume is the 8 ohm setting will cause the output stage to run hotter. If the current drifts or drifts more in one setting than the other, then that can be levelled at the design of the amp.
There are some 100 ohm's shown on the circuit connecting the output transistor emitters and as configured serve no purpose so perhaps these are the 100 ohm's mentioned. Perhaps the idea is to get an average current for the parallel pairs of outputs by using the junction of the 100 ohm's as the test points.
A value of 32 mv across each 0.27 ohm sounds a plausible value and would give a current of 118 milliamps per pair. That would fit with the theory but is what they intend. Assuming you have not altered the original settings then I would first see what you actually have across those resistors.
Thanks for the reply.
I can´t find my notes on what i initially measured but it was a lot more than 32 mV in 8 Ohm mode.
For now i´m using 32 mV in 8 Ohm mode to my 6 Ohm JBL XPL200´s and it seems fine.
It would still be nice to know what mode to use for setting and what voltage to set.
I can´t find my notes on what i initially measured but it was a lot more than 32 mV in 8 Ohm mode.
For now i´m using 32 mV in 8 Ohm mode to my 6 Ohm JBL XPL200´s and it seems fine.
It would still be nice to know what mode to use for setting and what voltage to set.
As I mentioned earlier, the 4/8 ohm mode only alters the rail voltage to the output stage and you should in theory find the bias current (the voltage across the 0.27 ohm resistors) should not alter in either position. The current should be independent of rail voltage.
What might happen with the mode switch is that the higher rail voltage will cause higher dissipation in the output stage and that in turn will generate more heat. That heat may be a factor in the current drifting (if it does, but it may not).
Ultimately if the amp is correctly designed the current is independent of rail voltage and temperature, however many amplifier designs do not meet goal.
What might happen with the mode switch is that the higher rail voltage will cause higher dissipation in the output stage and that in turn will generate more heat. That heat may be a factor in the current drifting (if it does, but it may not).
Ultimately if the amp is correctly designed the current is independent of rail voltage and temperature, however many amplifier designs do not meet goal.
Earlier setting "by the book" to 16 mv the average voltage dropped from 16 mV to 12 mv, switching to 4 Ohm mode from 8 Ohm mode.
Lower voltage at emitters means lower bias current, or am i missing something?
That is why i´m asking for advice what mode to use for setting and what voltage to set, because is see a difference between the 4/8 Ohm modes.
It was the same issues with my PM665vxi where the (faulty) manual said to set bias to 28 mV in 8 Ohm mode the confirm setting at the emitters to 50 mV. That would not happen in 8 Ohm mode. Setting the bias to 28 mV in 4 Ohm mode would give 50 mV at the emitters in 8 Ohm mode.
I guess the manuals for Citation 22 and PM665vxi has caused a lot of new vocabulary and grey hair for non-pros like myself.
I have looked into a lot of H/K manuals from this era and have found others being correct, or at least easier to understand.
Lower voltage at emitters means lower bias current, or am i missing something?
That is why i´m asking for advice what mode to use for setting and what voltage to set, because is see a difference between the 4/8 Ohm modes.
It was the same issues with my PM665vxi where the (faulty) manual said to set bias to 28 mV in 8 Ohm mode the confirm setting at the emitters to 50 mV. That would not happen in 8 Ohm mode. Setting the bias to 28 mV in 4 Ohm mode would give 50 mV at the emitters in 8 Ohm mode.
I guess the manuals for Citation 22 and PM665vxi has caused a lot of new vocabulary and grey hair for non-pros like myself.
I have looked into a lot of H/K manuals from this era and have found others being correct, or at least easier to understand.
It is the voltage across the 0.27 ohm resistors that is the direct indicator of bias current. Very important you understand the 'across' statement.
It is just ohms law, I=V/R If you have 16mv across one of the 0.27 ohm resistors then you have I=0.016/0.27 which is 0.059 amps or 59 milliamps.
If the output transistors are well matched then each voltage across each 0.27 ohm should be within say 20% of each other.
Where the confusion in their procedure comes from (as far as I can see) is the instruction to 'add a 100 ohm as in the figure'. What figure where 🙂 and then mention of test points which I can't see on the circuit.
Thanks, i know Ohms law.
When i have 16 mV in 8 Ohm mode which across one of the .27 Ohm resistor it gives 59 mA.
Put the switch to 4 Ohm mode lowers the voltage to 12 mV which across one of the .027 Ohm resistors it gives 44 mA.
For the Citation 24 the manual says:
And here are the specs for Citation 22 again:
When i have 16 mV in 8 Ohm mode which across one of the .27 Ohm resistor it gives 59 mA.
Put the switch to 4 Ohm mode lowers the voltage to 12 mV which across one of the .027 Ohm resistors it gives 44 mA.
For the Citation 24 the manual says:
And here are the specs for Citation 22 again:
That sounds like a normal effect of simply reducing the supply voltage. Ideally the amp should be immune to that effect but as I mentioned, many are not.
The 8 ohm setting runs the amp at higher voltage. If you don't need the full power then using the 4 ohm setting gives the amp an easier time because of the lower voltage. It will run cooler.
{You will also find if you listen to the amp that you probably cannot hear any difference even if you reduce the bias to ridiculously low levels such as just a milliamp or two... it's true, try it 🙂)
🙂 how indeed.
First thing I would do is adjust it with no speakers attached because any DC offset will pull a small DC current through either an upper or lower pair of 0.27 ohms. That skews the result.
If I was really curious, I would set the bias by the official procedure and then immediately measure across each 0.27 ohm and calculate the actual current and see what it actually comes out at.
Having set the bias I would see if using the amp on the 4 ohm setting covered all my power needs... and I'm sure it would because most of our listening is done at surprisingly low levels.
Give this a try, you might be surprised:
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
First thing I would do is adjust it with no speakers attached because any DC offset will pull a small DC current through either an upper or lower pair of 0.27 ohms. That skews the result.
If I was really curious, I would set the bias by the official procedure and then immediately measure across each 0.27 ohm and calculate the actual current and see what it actually comes out at.
Having set the bias I would see if using the amp on the 4 ohm setting covered all my power needs... and I'm sure it would because most of our listening is done at surprisingly low levels.
Give this a try, you might be surprised:
https://www.diyaudio.com/community/...h-voltage-power-do-your-speakers-need.204857/
Thanks, ok then I will keep the 32 mV that I adjusted to in the 8 Ohm mode, until i know better, and use the 4 Ohm mode playing my 6 Ohm XPL200.
That would keep the heat somewhat lower, and save some on the electricity bill.
And you are correct, the power meter on my Citation 22 seldom, if ever, reaches 2 Watts.
That would keep the heat somewhat lower, and save some on the electricity bill.
And you are correct, the power meter on my Citation 22 seldom, if ever, reaches 2 Watts.
Guess my math was somewhat off.
The "factory" 16 mV setting (if in 8 Ohm mode?) is over two transistors and therefor over two emitter resistors, 16 mV / .54 Ohm is 30 mA and in 4 Ohm mode 12 mV / .54 Ohm is 22 mA. Seems a bit too low?
I did some testing and found setting 32 mV in 8 ohm mode gave 24 mV in 4 Ohm mode, adjusting to 16 mV in 4 Ohm mode gave 21 mV in 8 Ohm mode and adjusting to 16 mV in 8 Ohm mode gave 12 mV in 4 Ohm mode.
12 mV / .54 Ohm is 22 mA which maybe is somewhat low, so i guess i will adjust to 16 mV in 4 Ohm mode and leave it there to be "safe" at 30 mA.
Thoughts on this?
The "factory" 16 mV setting (if in 8 Ohm mode?) is over two transistors and therefor over two emitter resistors, 16 mV / .54 Ohm is 30 mA and in 4 Ohm mode 12 mV / .54 Ohm is 22 mA. Seems a bit too low?
I did some testing and found setting 32 mV in 8 ohm mode gave 24 mV in 4 Ohm mode, adjusting to 16 mV in 4 Ohm mode gave 21 mV in 8 Ohm mode and adjusting to 16 mV in 8 Ohm mode gave 12 mV in 4 Ohm mode.
12 mV / .54 Ohm is 22 mA which maybe is somewhat low, so i guess i will adjust to 16 mV in 4 Ohm mode and leave it there to be "safe" at 30 mA.
Thoughts on this?
Thoughts are that firstly you will not hear any difference between all the different values so don't stress over that.
How can I put this nicely 🙂
I'm surprised it varies so much between the 8 and 4 ohm settings but that doesn't mean there is a problem, it just means the designer didn't make the design immune to bias current vs supply voltage changes. The only thing the 4/8 ohm setting does is select different tapping's on the mains transformer to give different rail voltages.
The currents themselves seem very low for a high quality design... by that I mean that somewhere closer to 80 milliamps per pair of output transistors would be closer to the ideal value. That kind of current generates quite a bit of heat and you have have two output pairs per channel, four pairs altogether. So pretty hot. That kind of 'compromise' in having lower bias currents than optimum usually suggests the heatsinking in the amp is not large enough and is commonly seen in more mainstream amps to keep overall costs down. Lower than optimum bias also means it runs cooler and is more reliable.
Ultimately you have to accept it is how it is. Set the bias as per the recommendation and enjoy 🙂
How can I put this nicely 🙂
I'm surprised it varies so much between the 8 and 4 ohm settings but that doesn't mean there is a problem, it just means the designer didn't make the design immune to bias current vs supply voltage changes. The only thing the 4/8 ohm setting does is select different tapping's on the mains transformer to give different rail voltages.
The currents themselves seem very low for a high quality design... by that I mean that somewhere closer to 80 milliamps per pair of output transistors would be closer to the ideal value. That kind of current generates quite a bit of heat and you have have two output pairs per channel, four pairs altogether. So pretty hot. That kind of 'compromise' in having lower bias currents than optimum usually suggests the heatsinking in the amp is not large enough and is commonly seen in more mainstream amps to keep overall costs down. Lower than optimum bias also means it runs cooler and is more reliable.
Ultimately you have to accept it is how it is. Set the bias as per the recommendation and enjoy 🙂