Hii all!
I'm trying to build a 811-3 SE amp, and here is "my" preamp.
It has a gain of about 25 with a load of 1Meg (the grid resistor I'm planning on using).
As I'm a complete newbie I'd appreciate the help from all you gurus here...
Do you guys think it will be enough, or will I need an extra cathode follower stage (or something else I haven't thought about...)?
Is it possible to use a IT with this design ?
Thanks
-Miguel
I'm trying to build a 811-3 SE amp, and here is "my" preamp.
It has a gain of about 25 with a load of 1Meg (the grid resistor I'm planning on using).
As I'm a complete newbie I'd appreciate the help from all you gurus here...
Do you guys think it will be enough, or will I need an extra cathode follower stage (or something else I haven't thought about...)?
Is it possible to use a IT with this design ?
Thanks
-Miguel
Attachments
Hi,
Is that a 500V B+ you're using?
If that's the gridleak resistor of the first stage of your amp then it's way too high.
Cheers,
Is that a 500V B+ you're using?
It has a gain of about 25 with a load of 1Meg (the grid resistor I'm planning on using).
If that's the gridleak resistor of the first stage of your amp then it's way too high.
Cheers,
yap ... I'm thinking about using half of 500-0-500 supply needed on the power stage. It seemed simpler... Is it a bad idea ?Is that a 500V B+ you're using
Not quite sure I understand what you mean... The 1Meg is the resistor from the grid of the 811-3 of the power stage to B-. Perhaps I need an extra 100ohm resistor before the grid: ?If that's the gridleak resistor of the first stage of your amp then it's way too high.
100r
from pre >-----####-----(Grid
|
#
# 1Meg
#
|
v
B-
Just to make about 150V drop so I dont fry the 6n1pwhat is the purpose of the unbypassed 15k R18 resistor?
-Miguel
Just to make about 150V drop so I dont fry the 6n1p
In that case you should bypass it with a cap from the upper anode to gnd.
As Frank hinted 1M is too much, especially if you intend using fixed bias. Try 200k as max value. I also don't see how are you going to get enough gain - you need something like 90v at the 811 grid if i am not mistaken.
But if I do I loose about half the gain ... Why do you say that I must bypass it ?In that case you should bypass it with a cap from the upper anode to gnd.
The svetlana datasheet typical usage section has 3 scenarios:you need something like 90v at the 811 grid if i am not mistaken
130Vpp grid drive with -65V fixed bias and 450V plate
30Vpp grid drive with -165V fixed bias and 800V plate
280Vpp grid drive with -65V fixed bias and 450V plate
I was aiming for the second one, but now that I think of it it may be a typo... The grid drive voltage is quite low compared to the others Gotta work out the maths of this one
If you want the upper tube to act like a follower, eliminate the plate resistor. Then, since you're taking output from the cathode of this tube, you're basically getting CF behavior. You should have fairly low Zo ( not as low as a true follower). Also, depending on what you're driving, I think the 5u could become a 1u.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
- Home
- Amplifiers
- Tubes / Valves
- 6n1p pre with active load