[minya]

I'm in the process of building a Millet Hybrid tube amp (well, the waiting-for-the-parts process...) and I had some questions for the tube freaks out there.

The recommended tubes on the parts list are 12FM6 or 12AE6A from AES. The 12FM6 was out of stock when I checked - and I'm guessing still probably is...

I'm guessing these tubes aren't any good either, because they're cheap. The tube socket on the parts list is a "7 pin mini". Are there better tubes I could get (say, in the $10-$15 price range) that are easily available? I know NOTHING about tubes.

- Chris

 

[mekanoplastik]

First…I am not a tube guru but I hope you don’t mind me trying to help…

PPL stated in this thread ->http://www4.head-fi.org/forums/showt...0&pagenumber=1 “…12AE6 were designed for long Life in car radio use and the 12AV6 was intended for low cost table radios in the home ” This to me makes sound like it is an ok tube

(I have no idea about tubes either..)

Check this database -> http://hereford.ampr.org/cgi-bin/tube?tube=12FM6 they have some “Preferred Substitutes” for each tube and a whole lot of info about tubes….

Or you can try asking Mr.Millet himself, he seems to be a very nice guy when it comes to respond questions...

I am also in the process of building one and I love the idea of buying different models of tubes, lets see if a real guru shows up

m.

 

[minya]

Quote:

Originally posted by mekanoplastik First…I am not a tube guru but I hope you don’t mind me trying to help…

Certainly don't.

Thanks for those links. I'm going to go through 'em and see what I can find...

- Chris

 

[Wodgy]

These tubes are cheap because they're relatively unpopular, and thus undiscovered by the masses. Cheap doesn't necessarily mean low quality, for instance the 12SN7 is exactly the same as the 6SN7, just at a higher filament voltage, but they're about one sixth the cost, just because 6SN7's are more popular.

The most popular low voltage tube right now is the 6GM8, but it's also the most expensive (and unfortunately since Welborne decided to use it in one of their preamps it's about to get even more popular). Pete probably chose not to use that tube because of the cost. (I bought several 12AE6s and 12FM6's for the price of a single 6GM8.) This amp isn't designed to use the 6GM8 anyway, so don't bother trying it. In the AudioXPress article, Pete reports better distortion numbers for the 12AE6A, so don't worry too much if you can't find the 12FM6.

 

[minya]

Quote:

Originally posted by Wodgy These tubes are cheap because they're relatively unpopular, and thus undiscovered by the masses. Cheap doesn't necessarily mean low quality, for instance the 12SN7 is exactly the same as the 6SN7, just at a higher filament voltage, but they're about one sixth the cost, just because 6SN7's are more popular.

Thanks for the input, Wodgy. I ordered 2 12AE6A's since they were so damn cheap. I figure even if they're poor tubes, they're good to start with, and I can't go wrong.

But for anyone else reading, could they recommend a tube that mellows the high end (i.e. makes it less harsh) and emphasizes the mids/lows? That's what I'm looking for. If anyone knows a low-priced tube that fits these specs I'd be grateful.

Thanks,
- Chris

 

[elrod-tom]

Please let me know what kind of results you get with this project. I'm trying it myself, but won't be able to work on it for a couple more months. It LOOKS like it will be pretty easy to do (knock wood...knock wood...)

Mr. Millet strikes me as a pretty nice man. I e-mailed questions re) availability of the board and questions about optimizing for Grado 225's, and he offered helpful suggestions. At the time, I didn't know that he was THAT Pete Millet. He's like a rock star in the headphone amp industry!!

Good luck.....

 

[gdahl]

The 12AE6 is a pretty interesting tube. Most of the popular 9-pin tubes are dual triodes, but the 12AE6 (7-pin) has one triode and two diodes, which would normally be used in a radio's detector circuit. As mentioned before, it is designed to work at very low voltage, using a battery supply. Accordingly, the filament also draws very little current.

The plate curves look very good for this tube, and reveal excellent linearity in its intended operating region. Of course it can't swing many volts, and it must drive a very high impedance.

The 9-pin dual triodes that everybody uses (12AX7, 6DJ8 etc.) all the time generally use a supply voltage somewhere between 90 and 250 volts. The 12AE6 is happy with a supply of 14 volts, and its maximum plate voltage is 30!

If you are designing something with tubes that is intended to plug into the wall, there aren't many good reasons to use a tube like this. But if you want to use a battery supply, it is definitely worth serious consideration. I looked at a couple of other low-voltage tubes of similar configuration, and found their characteristics more compromised (higher plate resistance, mainly). Apparently Mr. Millet is pretty smart.

From the 12AE6's characteristics, I would be a bit surprised if it didn't have a bit of the mellowness on top that you are looking for.