Triodes

[davidwpack]

Ello! Have any of you guys built an amp with triodes such as the 300B or 6AS7G? I've found some old radio schematics but not concerning guitar amplification. I found one using 6SN7 in the preamp. I wonder if simply wiring in a volume and tone would make for a descent sounding amp.

[shooter]

simply wiring in a volume and tone

the 500k acts as volume, for audio a TS for me is "optional" most anything you plug in is already EQ'd, either in the studio, or on the device.  That schematic has no NFB so adding stuff isn't a big deal.  Most audio amps have some pretty complicated NFB that you don't want to add stuff too.

[Ed_Chambley]

Sigmund Sound, here http://siegmundguitars.com/soundking.html


He bulds a 300B Push Pull.  On an SE 300B most times you will not want to build with NFB if you desire is HiFi and intend to listen to Billie Holliday for instance.  Increased reflected impedance is generally preferred.  Reference some HiFi groups.  I prefer Octal preamp tubes and use them often for guitar amps, especially low watt old National and Valco Circuits.  Great blues amps.


Since this is a geetar forum, if you build a KT88 or 6550 or el34 or 6L6 Push Pull and make it switch to triode (what amp makers sometimes call a stupid half power switch which should be called a half tone switch, I digress) with cathode bias, you will not get much difference.  Not enough to justify burning up a set of 300B tubes.  I did it once and cried.


But, if you have a pair of 300B just laying around, very few do, git you some big ole iron and have at it.

[Ed_Chambley]

6Sn7 is a lower gain, but nice sounding tube.  I prefer this as a Phase inverter sometimes.  I use more 6SL7 iin preamps.  Sort of like a really thick sounding tube like old 12Ax7 white letter RCA before the tube redesign limited the second harmonic.


Using the 6SL7 I get more even order harmonics. 

[davidwpack]

Thanks guys! I am interested in doing something quite different from my other builds. I've never built an amp with anything but an LTPI either. I had an amp (Silvertone maybe?) that used 6sn7s and I remember liking it. It still might be in my closet, I'll have to dig around later.

[TIMBO]

Hey mate, this might be of interest.
http://el34world.com/Forum/index.php?topic=19150.msg213198#msg213198

[Ed_Chambley]

Hey mate, this might be of interest.
http://el34world.com/Forum/index.php?topic=19150.msg213198#msg213198

Thanks, it is to me.  I got some 2A3 I need to do somethng with.

[PRR]

> doing something quite different from my other builds. I've never built an amp with anything but an LTPI

There are tons of known-good guitar amps which don't use the LTP. Suggest you explore other g-amp topologies.

The 300b is VERY expensive. And IMHO much too "mellow" for guitar. Suggest you wire any ordinary 6V6/6L6/EL_4/etc amp, add a triode switch, and see if it rocks, has the bark and bite that naked steel strings "need". If it is truly your thing (maybe your tone is pure gold right off the pickup), the audio pentodes triode-strapped get you 98% of the way to the "great power triodes" at 1/10th the cost, to a point where you can decide to empty-out your wallet (or not) for 300b.

_I_ think the 6080/6AS7 is a lame thing, probably whacked-out in 10 minutes after a 5-martini lunch. To my eyes, they put a grid in an old rectifier. Apparently twice: Bench's study shows two very different types of these tubes, bent and more-bent.

[davidwpack]

Timbo: hey how'd that amp turn out? Did you like it?
Ed: yeah those Seigmund amps is what got me looking into triodes. They have some YouTube clips.
PRR: hey, that's what I mean about something different. I'd like to try pentodes for the preamp, maybe a cathodyne PI and some kind of output tube I've never tried. Maybe not all those changes in the same amp. I don't know. Sovtek has a 2A3 that's around $40. Could be worth it maybe? I'm still in the considering stages of building something else and was curious about triodes. Thanks everybody!

[TIMBO]

Hey mate, I was very surprised with the overall sound and tone.
The build was really about getting it working again.
Even finding a working field coil speaker was a blast.

I don't think it's gig worthy but well worth it in the end.

[66Strat]

I was playing around with the idea of building a pair of PP 6B5 Triode amps. I got the idea from the Rockola juke box amp. My idea was to graft a paraphase phase inverter on the front end using either a 6SL7 or a 6SN7. Using a 6SL7 for the paraphase, an input signal of about 1 volt should be sufficient to drive the amp to full power of about 15 Watts. The 6SN7 would require more input signal. But a 6SJ7 operating at conservative parameters would provide the 6SN7 paraphase with more than enough gain to push the 6B5 triodes into overdrive, if wanted. But who would want that?

Anyways, here's how I would approach a guitar amp using the 6B5 tubes. Also attached is the Triadyne datahseet to provides insight into the operation of the tube.

[davidwpack]

Awesome! Thanks. Were you considering incorporating any type of tone stack or anything?

[66Strat]

No tone stack. Just Volume and Top Cut Control. For my purposes, in this type of application, I would keep it simple and forgo a tone stack. However, a multi-position switch could be used to switch in different coupling capacitors to change the voice of the amp.

My original idea was to build a pair of mono-blocks to plug a DAC or CD player into. But I decided that I would obtain better results using EL34s or 6L6s. This is where I landed for the monoblocks using 6L6s in pentode mode. I plan on building these later in the year.

[davidwpack]

Right on! Thanks for the schematics!