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JandG 2nd January 2007 03:03 AM

SE 6sn7 amp....
I recently aquired a 6sl7 into 6sn7 amp & replaced the thimble sized OT's with some out of a Sony RTR, re-wired & installed a 100k pot & all the usual jack, post etc... installed it in my bi-amped OB system w. B200's & dang............this thing is wonderfull,..ran thru a bunch of my amps, to make sure..beat every one of them, including 300B , believe it or not. So now I want to build one with all nice parts. this one has small amount of hum, etc.. So does anyone have a schematic, for a amp using 6sn7 as the output in SE..? I will by top quality trannies & such, I gotta do, this thing is ugly & crazy, crazy good...I have looked all over the net, & haven't found one that was not for anything but head phones & odd OT's..If you have a idea on building one of these please let me know, so I can build it. I don't want to copy this one. I want one with better Power supply & etc.... This would be my 1st non kit build..I mod & restore, that has been about it.. time to build some.Thanks , J & G

Alastair E 2nd January 2007 11:00 AM

'SN7 SE..
The SN7 wasn't normally used as an O/P tube to drive a speaker to my knowlege, so I guess schemes for it as such will be rare!

You may look around the web, for 'Micro-Power' triode schemes, that use 9 pin tubes like the ECC series, or even 5687 type schemes--maybe worth a try...

At a wild guess, its probably both sections strapped out parrallel, with the SL7 driving the grid. I reckon the +B probably around 300V maybe good for around 2-3W, not really sure.

It may be a good idea to 'reverse engineer' your existing equipment by drawing out the scheme as its built. At least then you have something to work to. The hum present is probably PSU related, or possibly layout/earth-loop issues maybe due to your mods for I/P etc.

The 'SN7 is a great and fairly neutral sounding tube, normally used for drivers and cathode-follower line-drivers etc...:D

JandG 2nd January 2007 11:47 PM

The original builder sent a hand written schematic.
with unit,but some of the value's are hard to read. but I can always just get that from amp itself. Yes 300v is correct, actually I think it says 288v, & about 4w he said when fed a signal & about 2 watts with music. I stayed up way late last night listening to this & looking at all my expensive tube amp shaking my head. It really does beat them that volume level which is low, but basically a normal listen level @ 9' I want to do a nice PSU with chike filter & such & use a tube rectifier. The layout of this thing is all wrong & way to tight, so I will do it correct when I do the build. amp seems dependable. & very few parts. The attraction I have to this amp is HUGE. So I definatley am going to build a proper one. Here is a pic of the ugly critter.

tinitus 3rd January 2007 01:44 AM

I like your setup:)

I am not a tube expert - but 6SN7 and 6DN7 looks very alike to me

Always wondered about this little "giant killer"

BTW... doesnt Bottlehead use it too, in their SEX amp

But I guess it will need a tubepre with lots of gain

mach1 3rd January 2007 03:22 AM


this thing is wonderfull,..ran thru a bunch of my amps, to make sure..beat every one of them, including 300B , believe it or not.
If you have the right speakers, I have found that good flea power SETs have a magical quality that eludes all other amplification. I have spent lots of time and money trying to upscale that magic to more powerful amps, with varying degrees of success.

If you have an amp that 'does the biz' in your system, I agree with Alastair's suggestion that you reverse engineer a copy and use that to experiment on. With an Rp of around 7.5k, you would be looking at opts of at least 18k. You may be able to find some nice linestage opts on ebay that offer 8 or 16 ohm outputs in addition to the 600 norm.


JandG 3rd January 2007 04:22 AM

I am new to amp tube building but have
modded & messed with them for years. I have only took up seriouse hrs & hrs per week every in the last 3 years. still have not done a complete non-kit build, but sure I can do it no problem. Cool thing is about this little SET amp is that there are NO audiophile approved parts in it,, actaually I have caps in other amps that would buy 4 of what I have into this amp. the coupling caps are ceramic disk.. pure crap in my book, & bad PS, BAD layout, trannies to close to PT etc... very sloppy wiring latout etc...& still this is the best amp @ its volume range which is much louder than you would think, I have ever heard in my life so far. I have a Scott 299b, 300B in PP, a crazy nice 6l6PP, and many others..this lil thing sucks you in like I never have encountered,..I have a SEP modded Siemens/Klangfilm mono's that are good, but they just don't have what this does. I rotated all my amps over & over again this weekend & allways the same results..So Conclusion is , that low wattage SET is for me in my low volume listening adventures, thing is also,,that I don't know if I can go back ..If you know what I mean.. I am sure many SET people encounter this,,I am just thrilled to have it. I will build another using much better parts & such, I have losta of Vitamin Q & all kinds of parts, just not many OT's or PT's . I need to stock up. The OT's I installed are rumourned to be Tamura from a Sony RTR. & I think are 5k -8ohm also with a 600ohm tap, which I have no clue what that is for.. line..? mmmmmmmmm I might try to score another set of the Sony RTR OT's, as they seem to be very fine sounding..I am soon to purchase everything from Tube Cad to help me in my adventures. these crazy low part count SET amps have something going for them.I am a big fan of simple for audio. simple seems to allways take me on the good road, complex allways take me down expensive wrong turns. Hence small SET, B200's in OB, w/NO FILTERS... only Bass augmentaion in OB @ 80hz down

DrDeville 3rd January 2007 07:15 AM

How About A Schematic?
Hey JandG,

You've certainly piqued my interest--I'm a 6SN7 fan, and getting into SETs. Your amp might be perfect to run my tweeters.

Could you post a schematic? I'm hoping that the circuit is simple, and that won't be too much trouble. (batting eyes charmingly).

Oh, and I highly recommend John Broskies software. I have TubeCAD, and love it.



Zoran 3rd January 2007 09:12 AM

6SN7 is great tube...
I read somewhere that RCA stuff used some laboratory audio SE amplifier 0.7W output power with 6SN7 tube...
I think that was Olson when seting up famos RCA LC1 speaker...
The problem is output transformer, which has to be of very high prmary inductance (internal resistance of the 6SN7 is near 7K).
rough estimations is 250H... Imagine the capacitance...
Anyway, for those who want try tube shows best results at very high anode voltages near maximum of 450V...
For low-power amps maybe the better solution is 1.8W SE 10Y
amp with still demanding but less complex OT...

cliffhiker 3rd January 2007 12:17 PM

Bob Danielak has a paralleled 6SN7 SE amp on his web page.. though with a different input tube.

JandG 3rd January 2007 01:44 PM

I will post the schematic earlly next week.
I won't be able to get it scanned till monday or tuesday of next week, I will post it then.It is hand written & not the clearest, but most is legable.

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