Line-Stage Opinion Question

[JPeitzman]

Hello All,

I have decided it is time to pick out and build a tube line stage. I know there has been much debate over this, and I have read a lot of the other "pick me a preamp" threads. I have a short list of designs I am thinking about along with some questions on long-term projects. I will start with a list of what I am thinking, going in order of favorite to least favorite:

1. 5687 Preamp ( http://www.diyparadise.com/simplepreamp.html )
2. 6SN7 Preamp ( http://www.geocities.com/northbirdten/line_stage.htm )
3. Something involving the 12B4
4. 6T4 SRPP ( circuit by Poinz)
5 . Something else

The 5687 caught my eye because 1. it is simple... very simple, and 2. The Tube Depot has Tung-Sol 5687's on sale for $10 (though I have never ordered from them). The 6SN7 is a very close second because I have a couple handfuls of RCA 6SN7's laying in my tiny little tube box. I have heard good things about the 12B4 so that is why it is on the list. The 6T4 is up because Poinz seemed to like it in another thread, I am not a huge SRPP fan but there is a first for everything and I am open minded. Otherwise I am open to suggestions!

Before anyone shouts 10Y or 26, these are projects I have slated in my long-term projects notebook. I have this along with a C3g or 310A driven 300B, something large using a handful of my 12 and growing 807 stock, and I LUST after an amp utilizing the Telefunken EL156 . Anyways I have a couple questions for the DHT / IDHT preamp builders out there.

1. I an in the process of laying out (on paper) a choke-loaded 26, can the 10Y by choke-loaded or does it prefer a output Xformer?
2. How does the 27/56/76/264B(I have two, that's why I ask)/244A/ect... compare to the 26/10Y?
3. Any other suggestions for tubes of this class or are the 10Y/26 pretty much IT.

Thanks!
Cheers,

James

[Eli Duttman]

James,

The gain structure the rest of your equipment needs, should (IMO) strongly influence your choice.

The medium mu 5687 and 6SN7 may wind up giving you a "hair trigger" volume control. OTOH, the low mu 12B4 might be exactly what the rest of your stuff needs.

[JPeitzman]

Good point, and definitely something I need to consider. The eventual 26 or 10Y will be paired with the 300B or the like. But the line-stage I am looking to build now will be general use. Basically it will be used with all my amps and it will travel too. I do plan on building more than one of these, most of the circuits are simple enough and I have most of the parts in my junk box/basement somewhere. I do have a couple quick questions though:

1. What are some general thoughts on a Line-Stage that is ½ 6SN7 or 6SL7 or something similar with a 6SN7 White-Cathode Follower slapped onto it? Much of an advantage over 6SN7 with ½ traditional grounded cathode and the other ½ cathode follower?

2. I am not that new to tubes but at the same time I am still a youngin'. The thing I am wondering though is if there are any advantages, say in the 5687 circuit, to using both halves of the 5687 in parallel? I know there can be some advantages when it comes to SS stuff, example a parallel string of JFET's, but I don't know about tubes.

Thanks

James

[JPeitzman]

Another question for the tube guru's: In whatever design (s) I chose to use I had planed on using a L-C-L-C or similar power supply setup. I am also am planing on trying out the Janus Shunt Regulator or some other similar tube regulator. What I am wondering is with say the Janus Shunt do I have to have the L-C-L-C before the shunt or does the Janus by design take care of enough noise that you just need a L-C or C before the reg and maybe a C after?