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ARC SP16 preamp Clone
ARC SP16 preamp Clone
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Old 19th November 2019, 03:56 PM   #11
Francois G is offline Francois G  United States
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Originally Posted by denny9167 View Post
Your on the right track, below is an example of a similar setup using 6SN7’s this arrangement sounds fabulous.
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.
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Old 19th November 2019, 08:17 PM   #12
maton00 is offline maton00  Mexico
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Quote:
Originally Posted by Francois G View Post
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 by maton00; 19th November 2019 at 08:23 PM.
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Old 20th November 2019, 12:48 AM   #13
Adams_Leo is offline Adams_Leo  China
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Originally Posted by cygnus x1 View Post
How about a 6SL7 (as in the Octal Cornet)?
6SL7 is similar to 12AX7,but the size is bigger.
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Old 20th November 2019, 11:55 AM   #14
denny9167 is offline denny9167  United States
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Quote:
Originally Posted by Francois G View Post
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.
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 by denny9167; 20th November 2019 at 11:58 AM.
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Old 20th November 2019, 03:49 PM   #15
cygnus x1 is offline cygnus x1  United States
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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.
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Old 21st November 2019, 06:06 PM   #16
denny9167 is offline denny9167  United States
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Quote:
Originally Posted by cygnus x1 View Post
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 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.
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Old 22nd November 2019, 08:31 AM   #17
baudouin0 is offline baudouin0
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The DN2530 MOSFET for 1039 is the best match. The DN2540 may be a little low on current unless you adjust the resistor.
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Old 22nd November 2019, 09:08 AM   #18
analog_sa is offline analog_sa  Europe
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ARC SP16 preamp Clone
It is unreasonable to expect that a real device would not need the current adjusted.
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Old 22nd November 2019, 12:21 PM   #19
baudouin0 is offline baudouin0
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Totally true with FETs - however there is no adjustment provided. I may be the 1036 is supplied for a certain pinch off. DN2530 seems to have a high pinch off in simulation although is not clear from the datasheet. The simulation models are from microchip website.
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Old 22nd November 2019, 12:36 PM   #20
analog_sa is offline analog_sa  Europe
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ARC SP16 preamp Clone
It is much more likely ARC have sets of selected fets that go together with a resistor. I believe i have seen an extra set of parallel resistor pads in some of their amps for this purpose.
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