Just a note to builders.
Do not just blindly use trimmers for R7 and R8. Know the reasons for MAYBE wanting to use them. Ultimately you would want to use fixed resistors here. If this is not explained clearly in the BOM document, please let me know to remove any ambiguity.
Do not just blindly use trimmers for R7 and R8. Know the reasons for MAYBE wanting to use them. Ultimately you would want to use fixed resistors here. If this is not explained clearly in the BOM document, please let me know to remove any ambiguity.
Actually, DO use one on R7 as a matter of normal procedure -- It is the DC offset adjustment.
Don't use one unless you need it on R8.
Don't use one unless you need it on R8.
yup
mini is just matter of PSU voltage and Iq , and (accordingly) needed hardware (xformer , htsnks)
mini is just matter of PSU voltage and Iq , and (accordingly) needed hardware (xformer , htsnks)
2SK1530 Bias
My aleph J with toshiba 2sk1530 is working, but the bias is to high.
The voltage drop at the source resistors doesn´t go lower than 550mV.
I use 2K potentiometers for bias and offset.
I also tried a 5K potentiometer for bias, but bias is still not getting lower.
The offset is allmost zero, but the temperatur is to high and i would prefer a voltage drop of 450mV as recomended.
My F5 is working fine with 2sk1530, 2sj201, so i didn´t expect any problems.
Do you have a hint what i have to do?
My aleph J with toshiba 2sk1530 is working, but the bias is to high.
The voltage drop at the source resistors doesn´t go lower than 550mV.
I use 2K potentiometers for bias and offset.
I also tried a 5K potentiometer for bias, but bias is still not getting lower.
The offset is allmost zero, but the temperatur is to high and i would prefer a voltage drop of 450mV as recomended.
My F5 is working fine with 2sk1530, 2sj201, so i didn´t expect any problems.
Do you have a hint what i have to do?
Did you use a jumper in place of R6 if you are using a 2K pot for R8?
EDIT: Scrap that idea. It should not cause a problem on the biasing.
EDIT: Scrap that idea. It should not cause a problem on the biasing.
Thanks for your response.
I didn`t use R6 and R30.
It seems that the adjustment range is to small for toshiba lateral Fets,
but why doesn`t it help to use 2K or 5K Potis?
I didn`t use R6 and R30.
It seems that the adjustment range is to small for toshiba lateral Fets,
but why doesn`t it help to use 2K or 5K Potis?
I assume you did use a 100k pot for R27A, as well as using a link at the R27 position.
EDIT: Please measure the current resistance over R27A pot.
EDIT: Please measure the current resistance over R27A pot.
There is a 68K resitor and no pot for R27.
I didn`t want to experiment with the current gain this time.
It shouldn`t change the bias, does it?
I didn`t want to experiment with the current gain this time.
It shouldn`t change the bias, does it?
Last edited:
OK, maybe we will have to see what inpact using the Toshibas will have on the the R values in the circuit as the Vgs is lower, as well as the max current of each device. I am not an expert on the AJ, so maybe Choky, 6L6, Buzz and the Others can help here.
Yes, i guess some people successfully tried the toshibas in the aleph J, so eventually there is help here.
The point i didn´t understand was, with 2K pots i reached 550mV at the end of the range of the pots. So i thought 5K would help me, but the bias didn´t go any lower with them, their might be a limit here?
Haha, i could use some pc cooling vents on the amplifier and hope the toshibas will last.
Thanks for your help.
The point i didn´t understand was, with 2K pots i reached 550mV at the end of the range of the pots. So i thought 5K would help me, but the bias didn´t go any lower with them, their might be a limit here?
Haha, i could use some pc cooling vents on the amplifier and hope the toshibas will last.
Thanks for your help.
R8 = Input pair bias adjust
R7 = DC offset adjust
R27 = Aleph CCS current gain, but also will set the output stage bias
Replace the resistor on R27 with 100k pot and you will be able to adjust the bias.
Or use a different value resistor until you get the desired bias.
R7 = DC offset adjust
R27 = Aleph CCS current gain, but also will set the output stage bias
Replace the resistor on R27 with 100k pot and you will be able to adjust the bias.
Or use a different value resistor until you get the desired bias.
6L6 thats interesting, so i use a voltmeter for R27, to a least get the left and right channel at the same current gain?
Do i have to lower or to rise R27 to get lower bias, so that i just move the adjustment range of R8 in the right direction?
So i might for example use 50K or 100K for R27, if i don`t want to use pots.
Do i have to lower or to rise R27 to get lower bias, so that i just move the adjustment range of R8 in the right direction?
So i might for example use 50K or 100K for R27, if i don`t want to use pots.
"Or use a different value resistor until you get the desired bias."
So i guess lower R27 means lower bias?
So i guess lower R27 means lower bias?
Jim
This is the thing that bugs me about this circuit that I can't understand. I always thought that the bias of the output stage can only be determined by:
1. The value of R7 and the current flowing throught it via Q1
2. The current flowing through Q3
My understanding is/was that the CCS only regulates current through the output stage as the current demand changes.
This is the thing that bugs me about this circuit that I can't understand. I always thought that the bias of the output stage can only be determined by:
1. The value of R7 and the current flowing throught it via Q1
2. The current flowing through Q3
My understanding is/was that the CCS only regulates current through the output stage as the current demand changes.