what do you tube gurus think about this?
- Thread starter hifi
- Start date
Topology seems to be OK. At the expense of incurring your wrath, I have to say that it is not my cup of tea.
I guess, the purpose of this preamp is for use in a band and when the band is not playing you would like to play CD or radio through your stage amp. Am I correct?
Why do you need to raise the cathode voltage on the input tube? I am referring to the 47K resistor. If you remove this resistor, then you may not need the 10nF input capacitor. I do not prefer cathode followers in general unless you want to run long cables from the preamp.
Mohan
I guess, the purpose of this preamp is for use in a band and when the band is not playing you would like to play CD or radio through your stage amp. Am I correct?
Why do you need to raise the cathode voltage on the input tube? I am referring to the 47K resistor. If you remove this resistor, then you may not need the 10nF input capacitor. I do not prefer cathode followers in general unless you want to run long cables from the preamp.
Mohan
Micke,
I agree with both of the previous posts:
--Drop the cathode follower at the input. There are a number of reasons to use a follower, but for the life of me I can't think of one to justify the use of one as an input buffer. One at the output is fine. (Incidentally, I'd consider raising the 100k at the output to 1M--it's there to drain DC off the back end of the coupling cap at turn-on, which is fine, but it will also be in parallel with the Zin of the amp/crossover and constitutes an unnecessary load.)
--Omit the cap for the cathode. The gain will drop when you do so, but you'll not only avoid an electrolytic, you'll pick up a bit of local degeneration (aka feedback) which will reduce distortion. These days, you don't really need a lot of gain in a preamp.
Grey
I agree with both of the previous posts:
--Drop the cathode follower at the input. There are a number of reasons to use a follower, but for the life of me I can't think of one to justify the use of one as an input buffer. One at the output is fine. (Incidentally, I'd consider raising the 100k at the output to 1M--it's there to drain DC off the back end of the coupling cap at turn-on, which is fine, but it will also be in parallel with the Zin of the amp/crossover and constitutes an unnecessary load.)
--Omit the cap for the cathode. The gain will drop when you do so, but you'll not only avoid an electrolytic, you'll pick up a bit of local degeneration (aka feedback) which will reduce distortion. These days, you don't really need a lot of gain in a preamp.
Grey
hifi said:
I guess you meant 6c41c ?
Here is couple of links I have bookmarked.
http://www.mclink.it/com/audiomatica/tubes/6c41.htm
http://www.tubes.ru/techinfo/GlassTubes/6s41s.html
Argo
6cc41
Hello,
why don´t you ask the seller, Gintaras Sakemas is always helpful. Think he can scan the original data sheet for you.
Good Luck,
Regards from germany,
Reinhard
Ad on: Look at www.tubes.ru, glass tubes and then
6N2P. You find the 6CC41. Looks very similar to a 12AX7. Little higher transconductance and internal shield at pin 9.
Reinhard
Hello,
why don´t you ask the seller, Gintaras Sakemas is always helpful. Think he can scan the original data sheet for you.
Good Luck,
Regards from germany,
Reinhard
Ad on: Look at www.tubes.ru, glass tubes and then
6N2P. You find the 6CC41. Looks very similar to a 12AX7. Little higher transconductance and internal shield at pin 9.
Reinhard
Apparently it's a near ECC83 equivalent.
Use TDSL for all your tube data questions..
http://www.duncanamps.co.uk/cgi-bin/tdsl3.exe/searchform
Use TDSL for all your tube data questions..
http://www.duncanamps.co.uk/cgi-bin/tdsl3.exe/searchform
Take that back....for stereo you need 1 ECC83 (1/2 per side) and 2 ECC82s (1 per side). The 7247 is 1/2 each. For a nice SE EL84 stereo amp design check out the Eico AF-4. I am building this with 1 12AX7 and 1 12AU7 instead of 2 7247s, leaving the tone controls out and adding a choke and larger caps in the power supply. Note that the signal goes through the 12AU7 side if the tube first. The copy I have of this is too large to post here.
