Another Single Ended High Gainer

[Cygnus X1]

I built a third, or second, whichever way one wants to count.
They are all different, based on the same concept-a single ended high gain low volume amp voiced towards a plexi cranked.

The outstanding feature with single ended builds is that they retain touch sensitivity (raw tone), and have the cathode driven EQ like tone stack.

I did some different things with this build.
The prototype is a doghouse power section-the one thing I watch for in high gain builds is NOISE. It did OK. I play this amp almost all of the time, as it is just sitting there on my bench corner and not taking up much space. 'Tis ugly tho.

Second one was much more physically attractive, but I built it on on a linear fashion on a black turret board. It was noisier, and I decided to go with a single 6SN7 power tube. Very sweet, prolly 2 watts? But not quite as "touch sensitive" dialed down as the prototype.

Welp, back to square one, with a bit of Dumble style.
(I went back to the original power tube and am using a 6550.)
I used the same large chassis as the second, and mounted the entire power section except one
stray cap, perpendicular to the stand alone preamp board. Shiznitz!
It is whisper quiet...NO hum, no buzz (not that I ever had a problem with buzz, just some radio interference).
And I think it helps the touch even more.
The gain is incredibly smooth.
It's not a Dumble, but it has a tone I have never heard-not coloration, just smooth. And much more headroom.

Another oddity-I built the boards on high temp Lexan.
From what I can see-these will take 300 degrees.
I had a snafu on the little diode board and had the iron set to 40 watts, and wrestled on a thick eyelet joint for a bit too long. It ended up pulling the eyelet, with only a little damage to the Lexan.
A fishboard would have weeped some bad stuff!
The plastic held up fine. I pressed another eyelet in and it was good.
[img:450:617]http://img235.imageshack.us/img235/4098/cygnussel23.jpg[/img]

[M Fowler]

Very cool Cygnus X1 and I bet a lot of fun to build and play through.

6SN7 huh.


Mark

[Cygnus X1]

Thank you, Mark.
You ought to build one of these!


Yes, that second one was 6SN7GTA or GTB.

I wish I could just use that one as a plug and play option, but it's an entirely different pinout and setup.

This one takes a whole galoot of tubes from a 6V6 to a 6550 without biasing.

The PT is plenty hefty enough to take the current draw.

[Phil_S]

6SN7 is a dual triode and you are discussing single-ended amps. Did you only use one section, did you parallel the two sections, or is it push-pull? What did you use for the output transformer?

Nice work in those pictures. Any sound clips for us?

[Structo]

Can you show some bigger pictures?

Looks like a nice build but I can't make out much from those pics.

Got a schematic to show us?

[Cygnus X1]

I wired the 6SN7 to run parallel.

Next time I use a 6SN7 as a power tube, I will try a push pull configuration. That amp (and build) is long gone.

This schematic is the basic AX84, shown with a KT88.
I am running a 6550 in it.
I wasn't very clear about that-sorry.
Most all of the tone is in the preamp.
I have all my drawings and notes in Autocad.

Link to the schem:
http://www.ax84.com/static/sel/AX84_SEL_080729.pdf

[Phil_S]

I recently finished a 6SN7 PP amp. I used two in parallel (which allows for me to pull one). I did this because I'm told the optimal plate load from the OT should be 22.5K. Two in parallel makes it half that. I used a recylced 9K OT and it sounds great. I understand that triodes will tolerate a range of primary R well. This amp is pretty much all clean. I imagine it takes pedals well. I only have one pedal, original Marshall Bluesbreaker, and I'll have to dig it out and see. These tubes are cheap as all get out. I bought what appears to be NOS on fleebay for under $5/tube shipped.

The amp I built is basically your typical Fender input/tonestack through a 6SL7, concertina PI through a 6AQ7 (half a 6SL7, why waste a section?), and the two 6SN7's. Don't be afraid to push the voltage. As I recall, I started out too low and went through 3 or 4 PT's, ending up with a 340-0-340 that is pushing into the mid 400's for the power tubes. They seem to like it and design spec says it will take 450.

I went all octal because I recycled a chassis and the donor was already punched. Here it is:
http://home.comcast.net/~psymonds/6SN7amp.htm

[M Fowler]

Phil,

Kool amp and I enjoy seeing some point to point going on there, nice.

Mark

[Phil_S]

Thanks, Mark. But, really, I cheat with terminal strips on the PTP thing. I'm hardly a purist. BTW, the split wiring on the filament string is because the PT I started with had two wimpy 6V windings and it was a feeble attempt to split up the load. It wasn't quite enough juice, though the B+ was actually not too bad. I ended up with the PT and OT from an Arkay FL-10, which ran a pair of 6V6. This project was just done on a whim, on the cheap, with lots of used parts.

Cygnus: sorry to hijack your thread.

Phil

[Cygnus X1]

No problem-looks cool!

I have a few all octals that I need this info for.
I haven't done much with octal preamp tubes except that Tweed Deluxe 5C3 I just finished. The reputation for the 6SC7's, 6SN7's are that they are noisy.

I either was blessed with good tubes, or the build was good enough not to show it-tapping the tubes gave up less microphonics than I usually get with noval 12XXX types. And no problems with hiss or buzz above normal either.

I actually liked the tone of the all octal 5C3 better than the 5E3! Blasphemy, I know (amongst the purists). It had a warmer tone, more like a Gibby GA5.

[M Fowler]

Cygnus X1,

I bought my 6SC7 and 6SN7 tubes last week for a 5C3 build but it will have to wait until later too many builds going on. Using Tony Z's point to point method on this one.

Will be interesting to see how noisey the point to point wiring is.

Mark

[Phil_S]

The reputation for the 6SC7's, 6SN7's are that they are noisy.

I think this is true of new production tubes, but old ones are likely to be OK. That is why I went to eBay. At the price I paid, I figured that I couldn't get hurt too badly. All in price on a pile of 6SN7's was between $3 and $5 per tube. As we all know, eBay really isn't "the place" to buy tubes, but sometimes it works out.

[M Fowler]

I went to the tubestore the 6SC7 NOS was $9.95 and the 6SN7 $12.95

I was wrong I bought these to build an old style tweed bassman amp not the 5C3.

Mark

[Cygnus X1]

Very cool.
I went with a very tightly packed eyelet board for the 5C3.

I am thinking STRONGLY about a '59 Bassman build.
5F6A-but I would have to buy a GZ34 recto and 5581's.

I have the iron for it in a Masco PA amp running cathode biased 6L6's. I might just go ahead and try it with those
and a 5U4GB.
Oh, and the octals-it has 2x6SC7's and a 6SJ7 pi.
"Bassman?" I don't know-but it will be close.

And from the sound of that 5C3 I have high hopes.
It should be good!

[M Fowler]

Cygnus X1,

Keep us posted on your progress sounds like fun.

I am using Tino Zottola Book Vol. 1 building a 5B6 chassis early Tweed Bassman. It uses 5U4, 6SC7, 6SL7, and 2 x 6L6. PT is 700v ct, 6.3v, 5v.
OT is 4k to 6.6k will work 50w. The chassis is all point to point.

I like his books vol. 1, 2, & 3. I am not going to build all of his projects but there are many that I do plan to build.

Mark