6Y6GT experiment by bonehead amp works.

[DummyLoad]

fooling around on the breadboard with 6YGT for low(ish) volt amp - Y? because i can... they are cheap, i'm cheap, and i'm bored.  iron is edcor GXSE10 2.5K to 8Ω and hammond 450VCT PT. 

sounds OK, just not as good as i'd hoped with the preamp i married it to. it does make about 6W. gonna swap the 6AV6 for 12AX7 and cascade for more gain. 

i am cooking the 6Y6 plate at about a calculated 15 watts - spec-sheets say 12.5W max and seems to be ultra conservative. running G2 at about .4 watts (2.3mA at idle and hits at 9mA peaks running full tilt with hard strumming, so ≈1.8-ish watts for g2 and marginally out of spec. meh! live on the edge.     

schema with telemetry attached for your viewing (or ridiculing) pleasure. 

--pete

EDIT - Rev 4.0a  is final - posted in reply #30.

[shooter]

nice, but I have none, you doing 6BQ6 next, I have lots 

[DummyLoad]

nice, but I have none, you doing 6BQ6 next, I have lots 

say whut? did i just get volunteered? 

--pete

[shooter]

 

naw, well unless you want, hell I'd even send you a couple untested on my dime 

[DummyLoad]

dew ewe have 6CD6G/GA? also remarked as "7867 - Audio Tube", wink, wink, wink!   

built one of thems in geetar amp. sounds really good, but EF86 gets cantankerous. 6267 from GE seem to hold up - i think those are cherry picked telefunky/w. german though, so price is bonkers for anything stamped "w. germany".

those two below look like hillbilly relation...just sayin'.

http://www.nj7p.org/Tubes/PDFs/Frank/127/6CD6GA.pdf

https://frank.pocnet.net/sheets/127/7/7867.pdf

--pete

[shooter]

got 6 of these that someday i'll get a socket n top cap for n try out.
https://www.tubedepot.com/products/6je6c-6lq6

[DummyLoad]

got 6 of these that someday i'll get a socket n top cap for n try out.
https://www.tubedepot.com/products/6je6c-6lq6

do you have the 40W variants - 6LF6 / 6LV6 / 6LW6?

6LX6 is a compactron type of the novar type you posted. seems to be easier to source comapctron sockets.

--pete

[shooter]

nope, these all came from a guy that stopped by my barn sale.  swapped me 2 5 gallon buckets of tubes for some of my old junk 

I threw out 1.5 buckets worth, but that left ~ 30 audio/guitar tubes.
I have somewhere a schematic workup of a audio stereo PA, but for some reason I keep building guitar amps 

[DummyLoad]

this revision is a lot of fun! $3.50 output tube makes some impressive guitar tone. 

BB makes hacking so much easier.

https://www.dropbox.com/sh/am7teczzw893nzg/AADdd0EGDfwVswnokdWLZdLka?dl=0


--pete

[shooter]

You are the BB master, IIRC, SG built a pretty good one also, mines the trailer trash version 

[PRR]

25L6 is one of the few for-SE Audio tubes. (6Y6 is industrial 25L6.)

[DummyLoad]

25L6 is one of the few for-SE Audio tubes. (6Y6 is industrial 25L6.)

ok, so that explains the tolerance to the total abuse i'm bestowing on my experiments' example. i have left it idling for over 4 hours and not even a hint of red-plating at ≈15W calculated pdiss. IR thermometer indicates peak plate temp at about 260°F


--pete

[DummyLoad]

this version is by far the most fun and refined?    cantankerous, but it can be dialed in to suit and is relatively quiet in spite of insanely high gain.

trimmed back on 6Y6 g2 supply - was adding a fizz to high notes when full up. i can run the master full up with that annoying artifact.

added some more filters to help stabilize & for RF management. still, though, when cranked up enough (usually beyond usable gain levels) it does have a propensity to become a 6W-ish AM detector.   

--pete

[PRR]

....at ≈15W calculated pdiss. ....

It was a few days ago but I interpreted the telemetry as 13W Pdiss. I'm not going to split the hair 12.5/13.

[DummyLoad]

last telemetry i posted in Ver5.0 schema: 245 Vp - 20.7 Vk @ measured 66mA Ik = 14.8W - close enough to 15W to call it 15W? 

--pete

[shooter]

cantankerous

Is that from the 6AU6?  I found them very cranky when I did a 3SE as a PA.  Nice sound, crunchy, Marshall-ish at < 10W

[DummyLoad]

cantankerous

Is that from the 6AU6?  I found them very cranky when I did a 3SE as a PA.  Nice sound, crunchy, Marshall-ish at < 10W

yes, from 6AU6 PREAMP tube - they are fairly microphonic. increase screen supply voltage (reduce Rg2 value) to push gain down to manageable level.


as with any preamp pentode, it takes some fiddling to get it dial in.


--pete

[shooter]

fairly microphonic

Yup, same when used in a PA setting, and I used 3!!  Drove it with a 6SN7.  went through my build notes; very heavy impedance mis-match from driver to PA, signal went from 55vpp to like 6! I lern't about cathode followers n fixed it 
NOT worth repeating.  was "designed" as a small tube audio amp <2W. doubling as a practice amp at ~4w screaming.

reduce Rg2 value

good to know, I had 1k at each tube.
was fun learning though, a special thanks to HBP especially for hanging in there circa '14

amp on top my built cab for a pair of 8" audio Nirvanas, sadly I needed to turn 'em into groceries 

[bmccowan]

Hmm - I have a couple of 6W6s hanging around and was thinking of doing something similar but with octal preamp. Lower wattage than the 6Y6 I think.

[PRR]

> close enough to 15W to call it 15W? 

I may have allowed for G2 power. I may have just figured too fast. And 9% wall drift would put it a little under or considerable over. This last fact may have been taken into account in dimensioning the better grade of 6Y6. Between reckless designers and careless users, it is better to put another cm of plate in the bottle than to have a lot of unhappy returns.

[DummyLoad]

Hmm - I have a couple of 6W6s hanging around and was thinking of doing something similar but with octal preamp. Lower wattage than the 6Y6 I think.

build same PS as in rev5 - use 5K 10W SE output transformer. should get agout 3.5W output.

when you build add a 1Ω 1W resistor in series with the pin 4 (g2) and g2 supply - measure voltage across 1Ω and 1mV = 1mA you know the drill. watch screen current under full power - try to keep that around or under g2 max rating.   


--pete

[PRR]

And..... 12.5W is a Design Center rating. If you don't own a meter, aim for that.

6V6 is allowed 16.6% more under Design Max rating, but YOU have to check what's really happening. Applying that fudge to 12.5 gives 14.6W.

And this is statistics. You may run a 6Y6 regulator in factory gear that runs 24/7 and never gets attention. You might like >2000 hour life. Going 10% over might be 1500 hour life (tho you'd have to burn-up hundreds of 6Y6 to get such good averages). If you have to send a $50/hour worker up the Jefferies Tube to change a 6Y6, short life sucks. But you work cheap and can change your own tube. And >1000 hours is a lot of playing. You'll probably build three more amps before this one quits.

[shooter]

If you don't own a meter, aim for that

gonna guess Pete has the top shelf ones already 

[DummyLoad]

If you don't own a meter, aim for that

gonna guess Pete has the top shelf ones already 

 ºº
  º
  ºº

 

--pete

[PRR]

> Pete has the top shelf ones

But if RCA/GE/Mullard waited for well-equipped Pete to order 13 million tubes a year to pay their rent and salary, they'd still be waiting. Tube makers had to guide the dumb designers/users also. Before 1960 many radio makers did not have a good meter, or just winged-it, or used parts 'like' everybody else was using.

Design Center leaves a considerable safety margin.

By 1960, TV and missile designers were asking "What can I really get away with?", and (some) had sophisticated measurement systems. With Design Maximum, safety margin was made their problem.

[shooter]

By 1960, TV and missile designers were asking

I was on a ship 3yrs, 4 guided missile radars, fired a total of 6 "yearly" qualification missiles.  Of the 6;
1 failed to acquire the beam and self destructed
1 failed telepathy reply n the gunners mate n I "manually" blew it, we hit the drone n qualified   
1 just went til spent n splashed in the ocean
3 did as designed 

[bmccowan]

Pete, thanks for the info on the 6W6 - I'll set that aside for a rainy weekend.

[DummyLoad]

lose the bypass cap & bypass switching on V2 (second AF amp / tone recovery) and swap V1 rg2 from 1M to 470K. that is what works best overall. still if you push too hard it can be made to squeal.

YW, bmccowan - 

--pete

[DummyLoad]

acrosound published a PP UL plan that used 6Y6G - surely they read the datasheets, and simply paid not much attention to the screen & supply voltage stated limits. based on the acrosound plan attached; they indicate a PS delivering 275V B+ to OT, so about 260-ish V to the plates and slightly more to screens.
 
doesn't seem like it would be a reliable setup, unless published 6Y6G specs were downrated grossly so as not to compete with higher cost tubes.   

interesting layout - esp. the phase inverter: looks like a cross coupled type.


--pete

[PRR]

> 260-ish V to the plates

With cathode resistor, it is "only" 222 V to plate (and screen).

I also have the idea that 6Y6 may have been being dumped about that time.

[DummyLoad]

stepped back to rev. 4.0, all triodes - added nfb and took care of a HF osc. issue beyond my hearing range with VR1 past 1/2 up, solved with C9. so now at ver 4.0a 

this is very likely to end up in a chassis of sorts. still has an unused triode - maybe add steve's tremelo and wobble pin 7 of v2.   

--pete

[shooter]

steve's tremelo and wobble pin 7

good idea, another;  add a "V1b" and blend the 2 1/2s.

[ALBATROS1234]

try a 6G6/G thats a nice sounding tube for this scenario.