You may find this a stupid question, but i'm strugling with it....
i'm busy designing an amp with el84 SE, now i found out that i will bias it at -5v, thus needing a max. signal of 10v (14,14v pk-pk)
if i'm correct line-out of a cd-player is 1,7vpk-pk , needing a gain of 8,3.
but all tubes i found will....with an input of 1,7 give out way too much voltage swing (usually 20-50v), if i increase rk they will go into non-lineair regions...
is the trick just to place a resistor behind the input pot which will REDUCE the input before amplifying it???
what current does a cd player produce(max)???
hope someone can enlighten me a bit
i'm busy designing an amp with el84 SE, now i found out that i will bias it at -5v, thus needing a max. signal of 10v (14,14v pk-pk)
if i'm correct line-out of a cd-player is 1,7vpk-pk , needing a gain of 8,3.
but all tubes i found will....with an input of 1,7 give out way too much voltage swing (usually 20-50v), if i increase rk they will go into non-lineair regions...
is the trick just to place a resistor behind the input pot which will REDUCE the input before amplifying it???
what current does a cd player produce(max)???
hope someone can enlighten me a bit
sorry, thought the datasheets worked with rms voltages.....
ok, 10v it is pk-pk.....i'd really like to get it running withouth feedback first....feedback will cost some more winternight studying.......
do i have to calculate the input from the cdplayer as if it were coming from another tube
signal -> Rg -> cgk ??? a resistor in series with the signal(rg->cgk) would set a ratio for decreasing the input signal thus risking frequency attenuation through cgk
(see attached picture)
i hope i explained myself a bit......
ok, 10v it is pk-pk.....i'd really like to get it running withouth feedback first....feedback will cost some more winternight studying.......
do i have to calculate the input from the cdplayer as if it were coming from another tube
signal -> Rg -> cgk ??? a resistor in series with the signal(rg->cgk) would set a ratio for decreasing the input signal thus risking frequency attenuation through cgk
(see attached picture)
i hope i explained myself a bit......
Attachments
@sy.... yeah i know, but it was used as an example, it's a different amp....
what does the 68K resistor do?? is this the ' input- reducer' and by placing such a resistor, do i have to take in acount the input impedance of my first tube or can i just use ohm's law to drop some voltage before entering the first tube??
what does the 68K resistor do?? is this the ' input- reducer' and by placing such a resistor, do i have to take in acount the input impedance of my first tube or can i just use ohm's law to drop some voltage before entering the first tube??
ah....thanks....
so thats why 1,7v pk-pk dropped only to 1,6983v pk-pk.......
Then rephrasing the question:
With a tube as sensitive at it's screen as an el84.......how do you drive it by a pre-amp tube....???
1. reducing at input (how??? voltage-divider????< practical setup????)
2. using a tube to de-amplify??
3. use a tube with very low mu (6n1p mu=8,5) ???
sorry for being unclear.....it's just so much info working out a schematic and finding all sorts of little problems that i lose oversight sometimes
so thats why 1,7v pk-pk dropped only to 1,6983v pk-pk.......
Then rephrasing the question:
With a tube as sensitive at it's screen as an el84.......how do you drive it by a pre-amp tube....???
1. reducing at input (how??? voltage-divider????< practical setup????)
2. using a tube to de-amplify??
3. use a tube with very low mu (6n1p mu=8,5) ???
sorry for being unclear.....it's just so much info working out a schematic and finding all sorts of little problems that i lose oversight sometimes
kathodyne said:
3. use a tube with very low mu (6n1p mu=8,5) ???
6N1P mu=33 like ECC88, 6DJ8
Consider ECC82/12AU7 mu=17
Hitting myself
i was so fixed on this one problem that i overlooked something as simple as the input pot and it's value.....
simulated it with a circuitprogram and it turns out you can set ratios to the input voltage!! how could i've been so stupid to completely overlook this????
well i got my answer now!!
.....reducing gain with feedback looks interesting but really i should be able to get it working without before i will be able to use nfb..i just don't know how to use/implement it....
i was so fixed on this one problem that i overlooked something as simple as the input pot and it's value.....
simulated it with a circuitprogram and it turns out you can set ratios to the input voltage!! how could i've been so stupid to completely overlook this????
well i got my answer now!!
.....reducing gain with feedback looks interesting but really i should be able to get it working without before i will be able to use nfb..i just don't know how to use/implement it....
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