[tomb]

The Tube Store has them, or claims to have them, anyway.
http://www.thetubestore.com/Tubes/12A-Types/12AJ6

I have 14 of them and saw that they were supposedly compatible, I will try them out and post results, I also have 12ae6 and 12fm6 so I will try to compare them all.

You guys are right and I was wrong.

I was going from memory and mixed it up with the 12FT6. That's the unicorn. I mentioned it on this page, but not on the other Millett Hybrid pages, for some reason - maybe because I thought there was no point in pursuing a unicorn:

There is also the 12FT6 tube, with an amplification of 15, but I can find no one who can substantiate whether it actually existed.

http://diyforums.org/MiniMAX/MiniMAXtubes.php

The problem with the 12AJ6 is that the amplification factor is 55! It's probably un-usable in a headphone amp. This is detailed here:
http://diyforums.org/MOSFET-MAX/MOSFET-MAXtubes.php

 

[scottie4442]

I know the 12aj6 are not good for headphone, but thought they might work well for small 8 ohm speakers. I am researching any changes that need to be made to the mosfet max so that these work, some people have said that they clip off at low volumes, not sure if this is after trying them or if they have looked at the specs and are making this call.

 

[tomb]

By all means, give them a try.

Clipping is the danger, though. With that kind of gain, you will quickly exceed the voltage available to the buffer.

 

[scottie4442]

I am researching how to get more voltage to the buffer circuit, especially with out hitting the tube with more voltage.

 

[addseo1118]

Nice to see your posts. Thanks for sharing here. 

 

[NuClear235]

I have now big problem:
When I am changing the volume with Alps pot so I hear SCRATCHING in sound.
I tried:
-change tubes (12AE to 12FK)
-change pot (I thied 6 pots, different values too /5k/22k/50k/100k)
problem still is it here!
 
Did not have the same problem anybody here, please?

 

[DingoSmuggler]

  I have now big problem:
When I am changing the volume with Alps pot so I hear SCRATCHING in sound.
I tried:
-change tubes (12AE to 12FK)
-change pot (I thied 6 pots, different values too /5k/22k/50k/100k)
problem still is it here!
 
Did not have the same problem anybody here, please?

This sounds like there is DC current across the pot, which would be due to the DC-offset from your source.
A film cap on each left & right input leads, before the pot will AC couple them, and should get rid of the scratching.
2.2uF would be my preferred value for a 50k pot, but anything between 1uF and 10uF will do the trick.

 

[NuClear235]

It makes scratching sound  when is not connected at input any source...
So where is DC voltage from ?

 

[DingoSmuggler]

  It makes scratching sound  when is not connected at input any source...
So where is DC voltage from ?

Well I'm all out of ideas now. Good luck eliminating this gremlin.

 

[NuClear235]

When I insert capacitor after pot, so is problem gone. But is it another capacitor in signal way.

 

[tomb]

When I insert capacitor after pot, so is problem gone. But is it another capacitor in signal way.

 
Yes, but as we discussed in e-mails, what is between the pot and the source? (Answer: nothing) Why would a capacitor after the pot stop the scratching?  If it's DC, then where is it coming from if not from the source?  You stated you didn't even have a source connected.  I suspect that may be the issue, but I can't explain why.

 

[NuClear235]

Solved: I bought new tubes and scratching is gone.

 

[tomb]

Glad to hear the new tubes solved it! 

 

[mik000000]

i am sure this has been covered in this thread, but i cant find it.
 
if i dont want to use a wallwart, all i need is a 24vac transformer to feed the max board directly? i understand i would be risking adding noise from the transformer.
thanks

 

[tomb]

  i am sure this has been covered in this thread, but i cant find it.
 
if i dont want to use a wallwart, all i need is a 24vac transformer to feed the max board directly? i understand i would be risking adding noise from the transformer.
thanks

If you want to put the transformer in the same case, then yes - you run the risk of adding noise.
 
If you simply purchase a 24VAC transformer, put it in a box, then use leads to connect it to the Millett MAX, then no - there is no difference from the walwart.
 
P.S. It's quite possible that you can locate a 24VAC transformer within the same case as the MAX and have it just as noise-free, it's just that it becomes a trial and error procedure to find out what distance/position results in low-noise.