vintage tube I/V from the year 1960

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#23
Franz G said:


This is absolutely normal with vintage gear!

I will try the above descripted idea with 6C45p: 45mA/V will result in input Z of something about 22 ohm.

Disadvantage: a second tube needed for the cathode follower, as the 6C45 is not a double triode.

Franz
Click to expand...


Franz

Have you looked at the required anode resistor ? ith 45 mA/V and 4mA peak current you already have 4V peak with 1 k-ohm

Zout then is yet low, no need for follower.....

The 6C45 needs decent bias though, 20 or 30mA.

succes
 
#25
hi,Franz

the 1st half of ECC88 is a current transmitter,so the 68 ohms resistor is not for I/V ,just is the bias resistor like what Guido Tent said.

the parallel of 10K and Rp of the 1st half ECC88(sorry,I don't know the value of Rp,cause I am not tube guy.....but in my mind, it should be much higher than in the common-cathode state) is for I/V,and the Vout=2ma*Riv

enjoy your DIY

X.G.
 
#26
Franz G said:


Not exactly, but I think about 30mA and a anode resistor between 6.6 - 8.3K should do the job.

It is good luck, as I have some 6C45 in my sparebox...

Kind regards
Franz
Click to expand...


Hi Franz,

But do you agree that 6k8 will give a lot of gain ?

6C45 is a fun tube. use grid stopper by the way........

If the cathode voltage isn't in the cirrect range, you can adapt the bias applying different (from zero) grid voltage. Decouple well.....

succes
 
#27
But do you agree that 6k8 will give a lot of gain ?
Click to expand...

What operating point would you choose?

6C45 is a fun tube. use grid stopper by the way........
Click to expand...

... of course! I use already 6C45 as driver for my 300B amp.

First, I complete my DAC and then, in a few days or weeks, I begin to experiment in this direction.

Greetings
Franz

P.S.
Cathode of a 300B as I/V converter here: http://www.tubecad.com/march2001/page6.html
 
#28
Guido Tent said:



I assume you connected it to the current output of the TDA1541 inside the 650
Click to expand...

No, I take it from the cinch output, the only change in the CD650 is 1.8k to 2.7ohm.
Maybe it is not good to have such small signal running through the analog filter and along the muting transistors but it was only a test for the box.
 
#30
Bernhard said:


No, I take it from the cinch output, the only change in the CD650 is 1.8k to 2.7ohm.
Maybe it is not good to have such small signal running through the analog filter and along the muting transistors but it was only a test for the box.
Click to expand...


In that case I am comfortable, in any other case this looks like a weird way of hooking things up.......

Hum may be reduced by inserting a full wave bridge.

cheers
 
#38
Hello

I'm working too on a valves I/U. But I want 0v on input, to avoid stressing my dac wich is based on ad1865.

This is just ideas on paper for the moment...

V1=160V
V2=8V

I : 6ma in first tube, 7ma in CF

Tl431 for negative voltage regulation and as ccs reference.

The 15k resistor on the anode of the first tube gives 15V for 1ma full scale on the ad1865.

The simulation works.
 

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#40
Hello

The diodes keep the grid voltage constant and negative.

In fact, the grid is referenced to the negative voltage with the two diodes (a zener and a normal one : better thermic coeficient).
The negative voltage is referenced to the ground by the tl431.
Like this, the grid is referenced to the ground.
As my input has to be 0V, I have to maintain the grid to a constant negative votage.

I could also put a battery on the grid...

Philippe
 
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