Pentode Reccomendations Please for 3W Practice Amp.

[Glennjeff]

Could some of you good folks point me in the direction of a pentode that has a plate dissipation of 2 to 4 watts.

Am working on a dedicated guitar preamp and want to use a 2 - 3 Watt push pull power amp as part of the overdrive section.

A couple of watts would also be plenty for practice amp / tracking purposes.

The plan is to capture the overdriven power amp sound in a preamp and also to have an amp that can be hard overdriven at a aurally non destructive room level.

[kagliostro]

An EL95 is too big ?



2 tubes in AB PP - B+ @ 200V load 10K = 4.1W

if it is too big may be a 5902 ?

http://www.mif.pg.gda.pl/homepages/frank/sheets/141/5/5902.pdf

http://jjs.at/electronic/class_ab_subminiature.html



Franco

[JB]

I've had good success running EL91's either single ended or a push pull pair.  Plentiful, cheap, sound good!

I get 1w or so single ended, maybe 4W PP.

[SILVERGUN]

Copied from a hi-fi site:
6CL6: This tube can be very sweet and easy in its presentation, it gives the impression that it plays music effortlessly. It is articulate and detailed but not as much as other pentodes, which could be a good thing. It has very good instrument separation abilities, and is dynamic. Compared to some pentodes it can sound soft, and polite in its presentation. If the output transformer primary impedance is too high, it can sound aggressive and perhaps a tad harsh, but never super harsh. The largest downside to this tube is its small size and thus it power output abilities, but it can be operated above its rated maximums and this does not seem to severely limit its life expectancy. I have tried at least 10 different brands, and some are more articulate, and others sweeter, but in general the above is the way they all sound. This tube will typically give you 2 to 3 watts of output power in pentode mode. This tube is also very forgiving in its impedance matching as well. The strong point of this tube is that it lacks nothing to any great degree. It does nothing exceptionally well but everything on an equally high level to where it is one of the best over all balanced pentodes made. It makes a great Spud amplifier because it will reach full wattage at less than 1vac of input, with no feedback.

[eleventeen]

Is a 6AQ5 too much? Those are really cheap. (in the US)


ed: Yes, a 6CL6 is also a sleeper of a tube. Probably even cheaper than 6AQ5.

[SILVERGUN]

And don't miss the 6BM8
You get a triode thrown in there with the pentode.

[PRR]

You can always use a big-tube in a small-tube job.

Like I am using 4,200 pound rope with a 900 pound winch. My wallet is strained, but not the rope. (Later I will use the tractor and the 4200 rating will be needed.)

6AQ5 is effective and thrifty.

If you have conditions for one type (such as Franco's 200V 10K 4.1W), but not that type, if you can find something similar it will probably give about the same result. I'm sure 6AQ5 will work in 5902 conditions (and not be over-rating). Adjust bias to get about the same idle current.

[SILVERGUN]

You can always use a big-tube in a small-tube job.

6K6GT sounded good to me with some overdrive at 'low' voltage...if you're cool with going octal

[bert123]

The following thread for Lo Watt Push/Pull  amp schematics (with pentodes) has some of info that may help you.

http://el34world.com/Forum/index.php?topic=12526.0

[Paul1453]

The guys have covered most all the good ones already.   

Another octal like silvergun suggested is the 6F6.   

So many choices, so little time.   

[Glennjeff]

Thank you all very much.

Will try out 6CL6, ECL84, ECL82(6BM8) and 6AU6  initially as their curves look the best for the classictone 3W transformer (25kOhm) that is coming.

Want to run everything at the limit of specs as that seems to be the rock and roll rule of thumb.

Will put the project up here as it develops.