• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Line-Stage Opinion Question

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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 :rolleyes:

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 :devilr: . 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.


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.


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?
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