Akikido LSA/HPA 9-Pin or Akikido Octal which one? - diyAudio
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Old 17th November 2009, 11:26 PM   #1
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Default Akikido LSA/HPA 9-Pin or Akikido Octal which one?

If you were going to build a preamp and these two were your only choices, which one would you build?

I'm thinking of building both, but like some opinions especially from those that have built either or both.
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Old 18th November 2009, 02:56 PM   #2
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First: it is not akikido, but Aikido. Second: impossible to say which is best, but surely the noval version is more flexible as there are way more noval double triodes than octal double triodes. Third: maybe one can move this thread to the tubes/valves forum?
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Old 19th November 2009, 05:00 PM   #3
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If I could afford NOS 6-volt octals, I'd build the octal one

Or just wire it to 12V heaters, use 12SN7s/12SX7s instead.
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Old 22nd December 2009, 07:13 PM   #4
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Quote:
Originally Posted by atwageman View Post
If you were going to build a preamp and these two were your only choices, which one would you build?

I'm thinking of building both, but like some opinions especially from those that have built either or both.
Hello,
Which one did you ultimately go with? Would appreciate an update when you have time.

Thanks!
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Old 4th January 2010, 03:21 PM   #5
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I love the 6CG7 9-pin. It's a great tube. It's cheap, too. (see 12AU7 vs 12BH7 vs 6CG7)

If you don't have any "audio nervosa" and you know your target application, then build the Octal and use the 6SN7.

I believe the 9-pin with the 6CG7 is equivalent. The 9-pin version is cheaper, opens the opportunity of adjusting the gain by choosing a wider variety of input valves, and allows adjusting the output impedance by choosing the output valve.
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Old 6th January 2010, 12:26 PM   #6
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Originally Posted by Kashmire View Post
I love the 6CG7 9-pin. It's a great tube. It's cheap, too. (see 12AU7 vs 12BH7 vs 6CG7)

If you don't have any "audio nervosa" and you know your target application, then build the Octal and use the 6SN7.

I believe the 9-pin with the 6CG7 is equivalent. The 9-pin version is cheaper, opens the opportunity of adjusting the gain by choosing a wider variety of input valves, and allows adjusting the output impedance by choosing the output valve.
Thanks for the input. I am hoping to pair it with an F5 clone for now. Maybe it would be a better option to go for the octals instead of the 9-pins if I would be using different amps with the pre, perhaps?
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Old 6th January 2010, 08:32 PM   #7
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I am hoping to pair it with an F5 clone for now.
The FirstWatt series generally don't have industry-standard gains. Thank goodness! The F4 is the ultimate expression of non-compliance, having no (unity) gain.

With the Octal Akikido, your linestage will be either operating with a fixed gain of the 6SN7, or you will be searching for NOS tubes that offer different gain values (that's what Tube Depot or Partsconnexion is for).

With the Novel (9-pin) version, you'll have a huge selection of valves to choose from, if you want to tweak the preamp as you try different power amplifiers.

For example, I have changed the driver tube in my EL84 power amp several times. When I was using it with my iPod, it needed a 12AX7. Used as my primary power amp in my "main" system (where it is now), even a 12AT7 provided too much gain, and it's operating on a 12AU7. I'll probably swap it for a 12BH7 just for grins. However, each tube swap requires disassembly to change the cathode resistor and plate resistor. Ugh! I don't know how often you are willing to do that. If you don't envision taking apart your line stage to optimize the preamp/power amp interaction when you switch power amps, you may be happier sticking with a single configuration.

In my case, I am using a Kinergetics KPA-1 (solid stage) linestage, so I am modifying the power amp to fit the preamp. Like the tail wagging the dog?

Gain poisoning is a real issue with my system. I am using a Theta DAC (digial to analog converter), which has really high output. My Musical Fidelity DAC's output is also a bit high. The KPA-1 preamp adds some additional gain, so the signal voltage that reaches the power amplifier's input is high. Add the efficient Triangle Acoustics speakers, and the power amp hardly needs any voltage gain of its own. It just needs to convert the high-impedance input voltage to low-impedance output voltage.

In fact, a Pass F4 with no gain works reasonably well, because the Theta/KPA-1 combination delivers enough voltage!

So here is a question back to you: how much gain does your linestage really need? What is your source (i.e. CD player or external DAC), and what is the efficiency of the loudspeakers attached to the F5?

p.s. I plan on eventually replacing the KPA-1 with a buffered stepped attenuator or TVC (transformer volume control).
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Old 7th January 2010, 05:22 AM   #8
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Thanks for taking the time and your extensive reply, it did give me a better understanding of that to look for. I'd still have to read up a bit to make sense of a few more things, perhaps.

As far as the tweaking goes, I should be OK with a resistor swap everytime I change the tube to match the amp. If it's just going to be a resistor and nothing else, would a pot with 3 resistors of the needed values work here if I decide on the types of tubes I need before-hand?

The sources would be a universal DVD player, a DAC and possibly a phono amp sometime down the line. The 2 speakers I have in mind have 85dB and 91dB sensitivities respectively.

Thanks again for your time and assistance, appreciate it much.
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