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hey to all from bombay, india....
haven't been to his forum in a while, but started looking back here recently.
a friend has commissioned an amp build from me. he wants a cleanish sound that can get nice and gritty too, with a fair amount of tonal flexibility. he would like to achieve a good driven tone without using any pedal distortion and is averse to more modern heavier sounds.
after the (surprising!) success of my first original design, i thought about thinking of a new one again, along the lines of vox and fender (and i believe Dr. Z or divided by 13 had some similiar aspects? cant remember now) . the topology i have planned out is:
- 2 input stages - bright triode (1/2 12AX7) and bight/dark adjustable pentode (6SJ7)
- a switch that lets you select between each channel discretely, or both channels with the input links or the triode channel cascading into the pentode channel
- a cathode follower (marshall values, probably, maybe 56k instead of 100k to reduce the overall gain) and marshall tonestack, master volume.
now comes the big question -
i wanted to design an end stage that is as flexible as possible. as i am ordering a custom wound transformer, specifications can be met easily.
i want the power stage to accept any of the following tubes:
-EL84 (noval socket will be wired in parallel)
-6V6 and variants (6F6, 6K6 etc.)
-6L6
-EL34
from my experience with my last build, EL34 does not work with a 5k output tap (i used a 6CA7 and smelled heated plastic, so i turned off the amp immediately - no damage was done). my last build involved a 5k:8E OT, and a 470R cathode resistor.
so this time, to eliminate any chances of frying something, i've decided to order the OT with the following specs and use a DP4T switch to change he primary as well as the cathode resistor (of course, only when the amp is turned off!):
Primary:
5k-4k-2.5k-0 (EL84/6V6-6L6-EL34 respectively?)
Secondary:
0-4-8-16 ohms
Power Handling: 15W
the PT will be: 250-0-250, 100 mA and 3.15-0-3.15 3A
will these specs be ok in your opinion for running even a 6CA7 in full tilt (which i doubt will ever happen, seeing that the man is more of a bedroom player)?
EDIT: apparent enough from the above description, but forgot to mention - single ended class A operation, inspired by the champ and also the allen class act. i don't want it to be underbiased though - the other build i spoke about has a 470 ohm 20W resistor as the cathode resistor, irrespective of whether 6L6, 6K6, 6F6 or 6V6. tried EL34 but the PT didn't have the current reserves, i think
haven't been to his forum in a while, but started looking back here recently.
a friend has commissioned an amp build from me. he wants a cleanish sound that can get nice and gritty too, with a fair amount of tonal flexibility. he would like to achieve a good driven tone without using any pedal distortion and is averse to more modern heavier sounds.
after the (surprising!) success of my first original design, i thought about thinking of a new one again, along the lines of vox and fender (and i believe Dr. Z or divided by 13 had some similiar aspects? cant remember now) . the topology i have planned out is:
- 2 input stages - bright triode (1/2 12AX7) and bight/dark adjustable pentode (6SJ7)
- a switch that lets you select between each channel discretely, or both channels with the input links or the triode channel cascading into the pentode channel
- a cathode follower (marshall values, probably, maybe 56k instead of 100k to reduce the overall gain) and marshall tonestack, master volume.
now comes the big question -
i wanted to design an end stage that is as flexible as possible. as i am ordering a custom wound transformer, specifications can be met easily.
i want the power stage to accept any of the following tubes:
-EL84 (noval socket will be wired in parallel)
-6V6 and variants (6F6, 6K6 etc.)
-6L6
-EL34
from my experience with my last build, EL34 does not work with a 5k output tap (i used a 6CA7 and smelled heated plastic, so i turned off the amp immediately - no damage was done). my last build involved a 5k:8E OT, and a 470R cathode resistor.
so this time, to eliminate any chances of frying something, i've decided to order the OT with the following specs and use a DP4T switch to change he primary as well as the cathode resistor (of course, only when the amp is turned off!):
Primary:
5k-4k-2.5k-0 (EL84/6V6-6L6-EL34 respectively?)
Secondary:
0-4-8-16 ohms
Power Handling: 15W
the PT will be: 250-0-250, 100 mA and 3.15-0-3.15 3A
will these specs be ok in your opinion for running even a 6CA7 in full tilt (which i doubt will ever happen, seeing that the man is more of a bedroom player)?
EDIT: apparent enough from the above description, but forgot to mention - single ended class A operation, inspired by the champ and also the allen class act. i don't want it to be underbiased though - the other build i spoke about has a 470 ohm 20W resistor as the cathode resistor, irrespective of whether 6L6, 6K6, 6F6 or 6V6. tried EL34 but the PT didn't have the current reserves, i think