I have 25 units mine all rank 6. But can work for 10mA or less for CCS as lower device without derate the mA?
I can buy rank 7 to use for minimum 15mA of CCS so can't need to measure the Idss?
For example if I need a CCS of 8mA is enough a lower device with 8mA Idss or the cascode drifts the value, if so how much?
I can buy rank 7 to use for minimum 15mA of CCS so can't need to measure the Idss?
For example if I need a CCS of 8mA is enough a lower device with 8mA Idss or the cascode drifts the value, if so how much?
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You must to use higher IDSS device, than required current.
Rank 7 -theoretically- granted that FET working in 15mA CCS or gyrator.... but I always measure such parameters.
Rank 7 -theoretically- granted that FET working in 15mA CCS or gyrator.... but I always measure such parameters.
Yes I always mesure the CCS or gyrator but will be good to know the difference expressed in mA to work at the desired mA.
Set the CCS to 9mA, CCS Vin 300V anode B+ 90V but can go up or down changing Vin CCS with the SSHV2??
SSHV2 is the shunt regulated PSU.
SSHV2 CSS must be set to -for example- 10..15mA higher than load (for example 2x9mA for both channel). The "spare" current multiplied with the required voltage (300V) dissipating on SSHV2 shunt FET.
If you know the load current, set the SSHV2 CCS 15mA higher than load, and set it 300V with SSHV2 potentiometer.
IMHO 300V it's too high if Ua anode voltage only 90V.
B+ optimal value is ( Ua + required swing peek + 30V spare voltage ), so if it's a preamp, 150V as B+ is enough.
SSHV2 CSS must be set to -for example- 10..15mA higher than load (for example 2x9mA for both channel). The "spare" current multiplied with the required voltage (300V) dissipating on SSHV2 shunt FET.
If you know the load current, set the SSHV2 CCS 15mA higher than load, and set it 300V with SSHV2 potentiometer.
IMHO 300V it's too high if Ua anode voltage only 90V.
B+ optimal value is ( Ua + required swing peek + 30V spare voltage ), so if it's a preamp, 150V as B+ is enough.
I'm sorry for my bad English Bela, the CCS at the SSHV2 is set ok, SSHV2 can go down or up the Vout no problem, the problem is that between the SSHV2 an the 7N7 tube I use a cascode CCS set to 9mA each channel but can't ajust the anode B+ of each triode because it's fixed to circa 90V and using the SSHV2 the anode voltage don't go up?
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No.
CCS loaded, fix biased stage has constant anode voltage, independent from B+ fluctuation/changing.
BTW 90V is too low as -3V 9mA operating point.
CCS loaded, fix biased stage has constant anode voltage, independent from B+ fluctuation/changing.
BTW 90V is too low as -3V 9mA operating point.
Yes, I want 150V for B+ at anode, there is something wrong?
I tried several tubes but always same 90V B+ at anode....
I tried several tubes but always same 90V B+ at anode....
Try to test these tubes at 300V B+, -3V, and 16k8 (10k+6k8) resistor.
The estimated anode voltage about 148V.
The estimated anode voltage about 148V.
Bela, tried with 5K6 resistor, 200V B+ and 150V at anode was OK.
Now tried 2 Sics + 150R direct between cathode & ground in place of battery bias and works also OK 150V anode ·3V grid 9mA.
Now tried 2 Sics + 150R direct between cathode & ground in place of battery bias and works also OK 150V anode ·3V grid 9mA.