I want to build a line-stage between my iPod/iPad headphone out and an Adcom GFA-545II. The reason for a preamp is to add some tube warmth.
I use an Aikido in my main system (6sn7s with a B+ of around 400v), so the thought of another Aikido for my iPod/Adcom combo could be good.
So, I was thinking of the 12vac Aikido.
Which tube version would people recommend - 6DJ8 or 12AU7, the former offers higher gain, but I wonder if I really need that much gain anyway?
I'd appreciate thoughts, comments, etc.
Charlie
I use an Aikido in my main system (6sn7s with a B+ of around 400v), so the thought of another Aikido for my iPod/Adcom combo could be good.
So, I was thinking of the 12vac Aikido.
Which tube version would people recommend - 6DJ8 or 12AU7, the former offers higher gain, but I wonder if I really need that much gain anyway?
I'd appreciate thoughts, comments, etc.
Charlie
It's doubtful that you need any gain at all. The line amp only needs to drive 100k.
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Tubes do not inherently sound "warm". It's bad tube designs that may sound "warm", because of second order distortion, treble cutoff, high output impedance...
The 12vAC Aikido design is pretty horrible by my standards, I would stay away from it.
Although it probably has too much gain for almost any system, the proper Aikido was designed to provide good sound reproduction. A 12V version would find this impossible, so if you want a mild FX box don't bother to use a complex circuit. Just do what the Chinese do: have a very badly biased cathode follower.
With regards to tube warmth, I know that it is due to distortion, but when listening to my Aikido/Aksa combo the music never feels "sterile." This is not the case with my pure classA op-amp headphone amp. Hence a touch of 2nd order distortion.
Ok, so a cheaper Chinese buffer that I could upgrade output caps on, tweak, etc.
How do folk like the $50 or so Little Bear pre's?
Charlie
Ok, so a cheaper Chinese buffer that I could upgrade output caps on, tweak, etc.
How do folk like the $50 or so Little Bear pre's?
Charlie
i was in the same boat as you couple of months back. I am a total newbie when it comes to tubes/ DIY electronics. I choose to play with the 12vac due to its low voltage. My set up was a DAC + adcom 545 mkii. I went with the 18v/ 12au7 version and i can say that i have been extremely pleased with the output so far. The harmonic restoration that the linestage provides is very impressive. The sound is very neutral, the sound stage improved and the bass got tighter. It felt somehow the music and vocals balanced themselves in a way that music was more enjoyable than before. The adcom can be a bit sterile but with the aikido it was even better sounding than my accuphase
Vincent77
would you care to elaborate why its a horrible design and what would you recommend instead? thanks
While I have nothing to contribute as far as what design you should use....
Here is some interesting information about Music, MP3's and your Brain.
MP3 Music: No Longer Connected to Your Brain? - Create Digital Music
I refuse to listen to MP3's, or any compressed form of music.
We all try so hard to reproduce some music for our ears and intern, create an emotion of feeling happy and then plug in terrible MP3 players with tons of missing data.
At the very least go with some form of lossless format if you are not doing so already.
Here is some interesting information about Music, MP3's and your Brain.
MP3 Music: No Longer Connected to Your Brain? - Create Digital Music
I refuse to listen to MP3's, or any compressed form of music.
We all try so hard to reproduce some music for our ears and intern, create an emotion of feeling happy and then plug in terrible MP3 players with tons of missing data.
At the very least go with some form of lossless format if you are not doing so already.
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KATARIAT, answers to your Aikido 12Vac questions
The first thing you should probably do is check your filament and B+ voltages.
Measure filament voltage across C10 and adjust R11 (the one sort of beside C10 and C11) so you have between 44 and 50 volts. If more than 50 you'll get premature tube failure if less than 44 the tubes will run too "cool" and might not sound so good..
Once this is adjusted measure B+ (high voltage) across C11 this is nominally 120 volts but anything between about 100 and 130 should be OK.
Note that adjusting the filament voltage will also affect the B+ (and vice versa) as they both come from different taps of the same supply.
Re: Tube Rolling
1. Be sure to get at least 24 hours (48 is even better) on new tubes before evaluating their sound qualities. Break in DOES matter.
2. Be careful mixing and matching tubes in a Aikido 12Vac as all the tube filaments are in series and mismatched tubes might have different voltage draw.
3. As far as new tubes go Broskie likes the JJ ECC802 (it's a Euro 12AU7 designation). I've had decent luck with some of the Electro-Harmonix tubes so a set of their 12AU7s might be worth a try.
Send me a private email if you like.
Regards, Steve
The first thing you should probably do is check your filament and B+ voltages.
Measure filament voltage across C10 and adjust R11 (the one sort of beside C10 and C11) so you have between 44 and 50 volts. If more than 50 you'll get premature tube failure if less than 44 the tubes will run too "cool" and might not sound so good..
Once this is adjusted measure B+ (high voltage) across C11 this is nominally 120 volts but anything between about 100 and 130 should be OK.
Note that adjusting the filament voltage will also affect the B+ (and vice versa) as they both come from different taps of the same supply.
Re: Tube Rolling
1. Be sure to get at least 24 hours (48 is even better) on new tubes before evaluating their sound qualities. Break in DOES matter.
2. Be careful mixing and matching tubes in a Aikido 12Vac as all the tube filaments are in series and mismatched tubes might have different voltage draw.
3. As far as new tubes go Broskie likes the JJ ECC802 (it's a Euro 12AU7 designation). I've had decent luck with some of the Electro-Harmonix tubes so a set of their 12AU7s might be worth a try.
Send me a private email if you like.
Regards, Steve
I merged Steve Morley's thread with this one since the questions it was intended to address are in this thread. 
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