hi.
I'm trying to connect a V-out DAC (2.5v) to a tube grid of 6n6p in SRPP
I know I have to use an input capacitor to block the 2.5v DC coming from the DAC chip and then I need to use a voltage divider (Gs and Rg on the attached drawing) to determine the correct signal voltage output.
... the question? is there any formula to calculate it?
do I need to take the tube amplification into account?
let's say I want to get the signal output on the level of any CD player 2v on the other side of the tube what resistors should I use for the l-pad? (Gs and Rg).
could you please let me know how to set the desired voltage level?
thank you
I'm trying to connect a V-out DAC (2.5v) to a tube grid of 6n6p in SRPP
I know I have to use an input capacitor to block the 2.5v DC coming from the DAC chip and then I need to use a voltage divider (Gs and Rg on the attached drawing) to determine the correct signal voltage output.
... the question? is there any formula to calculate it?
do I need to take the tube amplification into account?
let's say I want to get the signal output on the level of any CD player 2v on the other side of the tube what resistors should I use for the l-pad? (Gs and Rg).
could you please let me know how to set the desired voltage level?
thank you
Attachments
No need for a capacitor, or for Rg.
Instead, increase Rk1 by an amount 2.5V/Ia (Ia is the nominal anode current).
Instead, increase Rk1 by an amount 2.5V/Ia (Ia is the nominal anode current).
But do consider the need to protect the DAC chip: uses a series current-limiting resistor, and a zener clamp, for example.
cool, thanks, so basically change the operating point to bias the tube by -2.5v more and remove input cap, great! but still no answer to my question.
how to determine the voltage output level for example to be as most Cd players around 2v.
?
The gain of 6N6P SRPP is about 14-15.
What's the output AC voltage (RMS) of the DAC chip? Do you actually need any gain?
What's the output AC voltage (RMS) of the DAC chip? Do you actually need any gain?
The signal output will be about zero, as the circuit stands - the upper section is not connected correctly.
If you mean to draw an SRPP, look for example at Merlin's tutorial, and re-draw the circuit. Merlin shows how to calculate, while you are there.
http://www.valvewizard.co.uk/SRPP_Blencowe.pdf
If you mean to draw an SRPP, look for example at Merlin's tutorial, and re-draw the circuit. Merlin shows how to calculate, while you are there.
http://www.valvewizard.co.uk/SRPP_Blencowe.pdf
yes, I have seen that, you probably mean to take the output from the upper anode instead of taking it from the upper cathode?
what I would like is to avoid to high output level, I would like to keep it on CD player level around 2v or something between 2-3v
I found on Lampizator's blog a page where he suggests using 47k grid stopper resistor and 10K shunt resistor and that supposed to give 3v output level, but why?, how is this calculated?
There's no way you can get 2.5VRMS from WM8740 itself.
Are some external active components involved? Otherwise it's 1VRMS at max.
ahh, yep sorry I missed that mistake,..its a downloaded image from google, ..please skip that, it doesn't have to be srpp, it can be a common cathode follower or anode follower,....its the calculation that im after.
That's the point of my question though.
If you're getting 2VRMS out of DAC (for which you need external differential amplifier, since the DAC chip itself has two paraphase output at 1VRMS each), you don't need amplification at all and therefore don't need an SRPP. Dividing the output voltage and then amplifying it back to the original level is counterproductive - it just adds noise. Just use the cathode follower instead.
If you have substantially less then 2VRMS coming out of DAC, you'll need some amplification indeed. And since you've wondered about the exact resistors values to get to desired voltage, you'll have to provide the data I've asked for, otherwise no one won't be able to help you.
OK, fair point, I will want to use cathode follower as per your suggestion, using 6n6p tube and the datasheet of wm8740 I previously posted, is that enough detail to set the desired output voltage and calculate the input resistor value?
yep, that's the ohms law right?,..that's what you get after L-PAD before the signal enters the grid, I'm talking about signal level on tube output.
yes, I forgot, cathode follower aint amplifier.
that's why I was asking how would that be calculated for an srpp or anode follower.
let's say the DAC output is 1v and I want 2v at the tube output?
any formula for that?
that's why I was asking how would that be calculated for an srpp or anode follower.
let's say the DAC output is 1v and I want 2v at the tube output?
any formula for that?
No.
You still haven't told us DAC's output voltage in your application.
If you're using just one of the paraphase outputs of the DAC chip (and I assume that's the case given +2.5VDC at the output), you'll only get 1VRMS signal, so you need 2x amplification and the cathode follower won't do the trick.
You may use that 6N6P SRPP with 7:1 divider at the input (Gs=6*Rg, Gs+Rg>10kOhm), but that's very noise-inducing solution.
Or you may use some way to increase the signal 2x before the cathode follower - opamp-based differential buffer as per WM8740 datasheet, or signal transformer (1:2 with DC blocking cap before it if using just one of the paraphase outputs or 1:1 without cap if using both outputs), or whatever.
hi,
I don't have any application going on at the moment, it's just a theory, trying to understand how to calculate or set the tube output voltage level.
so I just made up a scenario of srpp, 1v output from the chip, and 6n6p tube to get the signal amplified to 2 v, as you would get from most CD players, that's just a scenario.
and asking if there is a formula for it.
I will look at/analyze the formula that you have sent, and another question once you have mentioned bringing the output voltage higher by opamp and than use cathode follower, so what about if I use another tube as anode follower instead of the opamp and after that a cathode follower to keep it tube kosher, so I would still need my formula to calculate the desired voltage output of the anode follower stage.
hope that makes sense.
thank you all for the answers and clues.
I don't have any application going on at the moment, it's just a theory, trying to understand how to calculate or set the tube output voltage level.
so I just made up a scenario of srpp, 1v output from the chip, and 6n6p tube to get the signal amplified to 2 v, as you would get from most CD players, that's just a scenario.
and asking if there is a formula for it.
I will look at/analyze the formula that you have sent, and another question once you have mentioned bringing the output voltage higher by opamp and than use cathode follower, so what about if I use another tube as anode follower instead of the opamp and after that a cathode follower to keep it tube kosher, so I would still need my formula to calculate the desired voltage output of the anode follower stage.
hope that makes sense.
thank you all for the answers and clues.