Unfortunately, I find very little information about Aikido, as an output stage for the DAC (directly to the power amplifier), which I would like to build in balanced version and which has an impedance < 100 Ohm at the output, so to speak in buffer function. I found a table (attached) in the Broskie documents, in which some constellations appear, which make this possible. But approximately only with 9-pin tubes. For octal tubes, which I would like to use, only the type 6AS7 is to be found (B+ 100V), which however is accompanied by a very high current (Ik 100mA).
Can anyone tell me if there is a range of values that makes it possible to use octal tubes? With: B+ of 150V, lower Ik value and Zo < 100 Ohm. Otherwise I have to start with Noval tubes. But again, I can't find any values that would meet the requirement.
Does anyone have a tip?
Can anyone tell me if there is a range of values that makes it possible to use octal tubes? With: B+ of 150V, lower Ik value and Zo < 100 Ohm. Otherwise I have to start with Noval tubes. But again, I can't find any values that would meet the requirement.
Does anyone have a tip?
What is the input impedance of the amplifier? Surely if it is a power amplifier it's input impedance will be 10k or more?
Thanks Schmitz77. I was afraid of that. Another constellation to get the Noval values even lower?
Need Help eliminating hum on a Aikido headphone amp
Octal valve, low output impedance for headphones - might give you a clue on how to use one.
Octal valve, low output impedance for headphones - might give you a clue on how to use one.
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if low Zout is your priority, perhaps use some feedback. It will also improve psrr, reduce distortion, and improve channel balance.
I did... But he doesn't answer.
But i can also go with Noval tubes. 5687 or 6H30 are good ways to go. The measurements after the setup will show whether this can be further optimized in my sense. Maybe somebody has a concrete tip, who has done it like this before...
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The practical solution will follow theory.
A power amplifier will likely have no lower than 5k ohm input impedance, but let's say yours is something very unusual and has a super-low input impedance of only 1000 ohms
According to theory, the ratio of source to load impedance should be 1:10. Down to 1:5 would be fine as well, but since you want the output impedance of your source to be as low as possible, let Zsource:Zload = 1:10.
Zload = 1000
1000/10,000 = 100
Zsource = 100
From your Aikido preamp, Zout = 100 ohms should do ya.
Zout for a cathode follower should be about 1/gm
Choose your output tube to have gm of 10mA/V at the chosen operating point.
A high gm twin-triode will do that for you. Use 6DJ8/ECC88, 5687, 6N6P or 6N30P with a healthy amount of anode current and you should be happy.
🙂😀
A power amplifier will likely have no lower than 5k ohm input impedance, but let's say yours is something very unusual and has a super-low input impedance of only 1000 ohms
According to theory, the ratio of source to load impedance should be 1:10. Down to 1:5 would be fine as well, but since you want the output impedance of your source to be as low as possible, let Zsource:Zload = 1:10.
Zload = 1000
1000/10,000 = 100
Zsource = 100
From your Aikido preamp, Zout = 100 ohms should do ya.
Zout for a cathode follower should be about 1/gm
Choose your output tube to have gm of 10mA/V at the chosen operating point.
A high gm twin-triode will do that for you. Use 6DJ8/ECC88, 5687, 6N6P or 6N30P with a healthy amount of anode current and you should be happy.
🙂😀
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What do you mean? Please look at the attached table. 5687 is one way to go with Noval tubes in Broskies papers. My question was, if there is a way with Octals. It is not.
I think someone somewhere said that a pentode makes a better current source and a better cathode follower than a triode. So, because the second stage of the Aikido amplifier is a combination of a constant current source and a cathode follower, wouldn't it be better to make the cathode follower stage with a dual pentode?