ARC SP16 preamp Clone
- Thread starter Adams_Leo
- Start date
Your on the right track, below is an example of a similar setup using 6SN7’s this arrangement sounds fabulous, if you want to stick to 9-pin tubes I would use a 6CG7, use a MOSFET as a sub for the cathode follower.
And LM334 as a ccs.
The gain is adjustable as well.
Attachments
Quite agree, I see one problem on first glance with their scheme, the first triode needs a coupling capacitor after the 300K load resistor, over time their would be a tendency for the circuit to start motor boating!
Huge difference in tubes, two different beasts, the 12AX7 requires much more feedback to achieve a reasonable gain for a line stage, and the 6SN7 is a much more linear tube to boot.
You definitely could use a tube for ccs, but you would have an additional heater supply, and a much larger negative bias to worry about and I don’t know if it would perform, or sound any better!
Last edited:
Looks like something I might try. Couple of questions.
- Do you know the HV supply needed?
- No load resistor in the first triode?
- What is the gain?
Thanks.
Its also a diferential schematic, it doesn't need a resistor the CCS fixes the operating conditions of that triode, the gain depends of the tube, with a 6sn7 will be like 10 (I'm guessing
) the HT something like 100-200V (IR820 has a rupture voltage of 200V Max) you can use a DN2540/IRF710/FQPF3N60...You may look for a low Crss miller capacitance in those something like ~50 pF or lower if you use a higher capacitance one it will have a low slew rate or may oscilate with ease
Last edited:
I’m running them at 250VDC, the first triode is basically a cathode follower. The gain can be set from about 12dB to about 18dB, depending on the ratio of the feedback. I think the variable resistor should be around 25K instead of 10K.
The 334 is set for a 10mA cathode current.
Last edited:
I read somewhere that the 6SN7, 6SL7 internal structure was symmetrical, unlike the 12AX7. Stated they sound better?
I have heard the Octal Cornet and it was very nice. A lot of neat design features.
I also like 6DJ8 and 2SK170/417a phono stages.
BTW, I'm not promoting or knocking anyone's design, just thinking out loud.
I hope the original poster is finding what he is looking for.
I have heard the Octal Cornet and it was very nice. A lot of neat design features.
I also like 6DJ8 and 2SK170/417a phono stages.
BTW, I'm not promoting or knocking anyone's design, just thinking out loud.
I hope the original poster is finding what he is looking for.
I wouldn’t worry, we should think critically about others designs! I don’t like a 12AX7 in a line stage, for one is the higher impedance one has to work with even using one as a cathode follower. It doesn’t mate well with low impedance SS amplifiers.