Help CCS for 1.33mA

[merlin el mago]

OK I will left the gain as is. Worth the work, I will improve the SQ changing components.

 

[trobbins]

With respect to a simple ccs, there are current regulator diodes with 100V rating that come in a range of current settings (can put two in series if voltage margin is needed).

I've used seriesed 1N5289 with a LED indicator to span 10-600V energised status.

If you don't have them to hand, then they may be a bit expensive to buy in.

 

[merlin el mago]

@artosalo, now is sounding well, what resistors values R3 / R31 to increase a little bit the gain without affecting the bias of output tube?

 

[artosalo]

Add C3 and change R2 to 1k8. Then gain is 12 dB.

 

[merlin el mago]

Thank you artosalo the SQ is very high with the headphones Sennheisser HD 600

 

[merlin el mago]

LND150 is for sure better for low currents. However, you could try this:

@artosalo
Could I try for 7N7 in place of 47K in your 6AS7 OTL headphone amplifier?

 

[artosalo]

7N7 as CCS ?

 

[merlin el mago]

No, in place anode resistor as active load.

 

[stocktrader200]

I'm using a 2N5401 for a 1.5ma current source. works great up to 160v

 

[artosalo]

No, in place anode resistor as active load.

You could make a mu-follower.
The Valve Wizard -Mu Follower

 

[merlin el mago]

As attached schematic? I guees I need to reduce the B+ 170V to 100V for the CCS?

 

[merlin el mago]

Or change the resistors, but how to calculate?

 

[artosalo]

I gues I need to reduce the B+ 170V to 100V for the CCS?

No, just adjust the current you want with the 2k potentiometer at the source of DN2540.
Then, with R2 you can adjust the anode voltage of 6SN7 as you want.

 

[merlin el mago]

To adjust I will use trimmers, once adjusted I will change to fixed resistors, thanks for support artosalo and have a nice week-end.

Another question what's the best load line for 7N7 in V & mA?


Felipe

 

[Merlinb]

Low current, high-Z CCS from my book.

 

[merlin el mago]

Hi Merlin, I can't source J309 trough hole only SMD but can source J107 it's OK?

 

[Merlinb]

Hi Merlin, I can't source J309 trough hole only SMD but can source J107 it's OK?

Yes, that will work. You will need to adjust Rs to get the current you need.

 

[merlin el mago]

Thank you. How to adjust voltage, like artosalo schematic?

 

[merlin el mago]

No, just adjust the current you want with the 2k potentiometer at the source of DN2540.
Then, with R2 you can adjust the anode voltage of 6SN7 as you want.

What happens if I change Ua & Ia of 7N7 to the grid bias of 6AS7?

 

[hego]

Low current, high-Z CCS from my book.

Felipe, I use this schema... but with lnd150 cascode for ECC83 and only Ia 0.8 mA !!!!!

It works fine.

Because the ECC83 have a high internal resistence I use de "mu" ouput for low Z adaptation.Genial.

Cheers