[Killercrush]

Hi fellow DIYers !

I got a pair of NOS CBS Hytron 7318, wich is a 12AU7 equivalent and I was wondering if there was any topologies that uses a pair of these with some Fets a la Melos style ?

Thank you !

Julien

 

[tomb]

The closest DIY amp is maybe the SOHA, which uses a single 12AU7 variant coupled to an opamp output stage. Steinchen has some add-on discrete buffers designed that will take the place of the opamp, but has not offered them in a Group Buy yet.

JRossel sells the SOHA in kits on his Glass Jar Audio website.

 

[ericj]

Why two 12au7's? They have enough gain that running two triodes in series would be way too much gain, and with a solid-state output, there's no reason to parallel the triodes.

There's also a 12au7 version of sijosae's multi-hybrid design.

 

[jbloudg20]

I was working on this exact thing, but never got to a prototype phase.

 

[headphonejunkie]

Quote:

Originally Posted by Killercrush /img/forum/go_quote.gif Hi fellow DIYers ! I got a pair of NOS CBS Hytron 7318, wich is a 12AU7 equivalent and I was wondering if there was any topologies that uses a pair of these with some Fets a la Melos style ? Thank you ! Julien

Hopefully steinchen's buffer will be close to a melos. The JISBOS buffer is a Jfet input stage and a Bipolar output stage.

 

[Killercrush]

What about this ?

http://www.siteswithstyle.com/VoltSe...eadphones.html

 

[headphonejunkie]

Looks interesting. You are going to have to get a bottlehead foreplay to do that though.

 

[Killercrush]

Also found this :

http://www.tubecad.com/2007/06/blog0111.htm

Look at the bottom of the page.

 

[headphonejunkie]

Now that really looks neat. I almost built an aikido headphone amp but backed out at the last moment.After I bought the boards. I may want one of those too. I have to see how the jisbos will sound first since I already have a SOHA.

 

[dsavitsk]

Quote:

Originally Posted by Killercrush /img/forum/go_quote.gif What about this ? http://www.siteswithstyle.com/VoltSe...eadphones.html

The schematic about half way down the page is essentially the same as the Less-pressivo. You could run the two sides of each tube in parallel and it should work okay. The 12AU7 would not be my first choice (and to tell you the truth, I can't think of a project for which the 12AU7 would be my first choice) but it should work okay.


Quote:

Originally Posted by Killercrush /img/forum/go_quote.gif Also found this : http://www.tubecad.com/2007/06/blog0111.htm Look at the bottom of the page.

You'll need a second pair of tubes, unless you want a mono amp.

 

[jbloudg20]

Quote:

Originally Posted by dsavitsk /img/forum/go_quote.gif The schematic about half way down the page is essentially the same as the Less-pressivo. You could run the two sides of each tube in parallel and it should work okay. The 12AU7 would not be my first choice (and to tell you the truth, I can't think of a project for which the 12AU7 would be my first choice) but it should work okay. You'll need a second pair of tubes, unless you want a mono amp.

Since we are on the topic of the less, what tube do you recommend?

 

[Killercrush]

Quote:

Originally Posted by dsavitsk The 12AU7 would not be my first choice (and to tell you the truth, I can't think of a project for which the 12AU7 would be my first choice) but it should work okay.

Technically, the CBS Hytron 7318 tubes are not 100% exactly like 12AU7, do a search on Tube Asylum and you'll see. It's the best 12AU7 variant ever.

 

[jbloudg20]

Quote:

Originally Posted by Killercrush /img/forum/go_quote.gif Technically, the CBS Hytron 7318 tubes are not 100% exactly like 12AU7, do a search on Tube Asylum and you'll see. It's the best 12AU7 variant ever.

Which is akin to being the smartest dumb person.

 

[Killercrush]

Quote:

Originally Posted by jbloudg20 Which is akin to being the smartest dumb person.

?!?... I just read that a few times, even from a few fellow head-fiers, Zanth and Biggie both owns a pair.

 

[dsavitsk]

Quote:

Originally Posted by jbloudg20 /img/forum/go_quote.gif Since we are on the topic of the less, what tube do you recommend?

There are a lot that will work well, and the best choice will depend on the headphones you use and the output transformers. If you are okay with running the two sides in parallel, then 6N6p, 6H30p, 6DJ8, 12AT7, 12AU7, 12AY7, 6N1p, 5687, 7199, 6SN7, etc ... The list can go on for a long time -- though on a budget the 6N6p is hard to beat.

For single tubes, 6C45, 5842, 6688, 7788, C3g, C3m, EL84, 6CL6, ... (pentodes need to be triode strapped)

As I say, what you need to do is find the tube with the plate resistance (rp) that is low enough for your phone/transformer combination, which basically means that tubes like the 6SN7 or 12AU7 are really only appropriate for high impedance phones.