SE 6L6 VS parallel SE 6V6

[TurboGuitarMelton]

Which would have more volume? (Loudness/power)


Single ended 6l6


Parallel Single Ended 6v6


According to what I know and have read it looks like the 6l6 will be about 12w if biased right and the PSE 6v6s are close to 9w.


Ot classictone 40-18031 (15W)
PT classictone 40-18027 (100ma)

Between a single ended 6v6 and a parallel single ended 6v6 power section I notice little to no volume difference and twice the amount of tubes... Would the 6l6 make the loudness difference more apparent?

The whole reason I ask is that Im once again having issues with my parallel SE champ build and am thinking about just converting it to 6l6. There seems to be lots of issues with trying to get the parallel single ended to work in a cramped 5f1 chassis. It intermittently drops in volume and comes back if I play the guitar louder. Its weird. Only happens once and then doesnt happen again until I turn off the amp and turn it back on. I have troubleshooted this amp to death and am ready to seek a simpler/proven design.

[bmccowan]

I do not think you would notice a big difference in volume between the parallel 6V6s and a single 6L6. I do however sympathize with not having much room in the chassis, as I too have had a difficult time with lead dress etc. when trying to squeeze too much into a small chassis. Makes troubleshooting a pain. I think it'd be pretty easy to rewire the power tubes for the single 6L6; but I suspect that you may not be solving the problem. For a guide, if you search for schematics for Dave Hunter Two-Stroke you will find 2 versions - one for parallel 2/6V6 and one for a single 6L6. (no comment on DH taking credit for designing an amp that Gibson and others built years ago)
I have two Gibson parallel 6V6 amps (GA-8 and GA-9) both sound great - no loud clean though.
Why not get a bigger chassis - the one Doug sells would work great for such an amp; lots of room to work. And if you do not like the amp, you will have room to go another route.
Also - looking at your earlier posts on this amp - you are running much higher B+ than Gibson had in these amps - not a cause of problems, but can make it more difficult to get it right IMO.

[TurboGuitarMelton]

I think it'd be pretty easy to rewire the power tubes for the single 6L6

And that's the main reason why I am thinking of doing it. Not to mention, Id like having the tube rectifier. I have a 5y3 on hand and my little power supply thing (SS rectifier and extra RC filter) I have in there makes me nervous... Its sitting right over the PT on a terminal strip. Makes getting in there to troubleshoot super annoying..


I am happy with the tone/volume level of the PSE 6v6s over the single 6v6 of my stock 5f1. If a SE 6l6 would give me more (even if only a tiny bit more) volume Id be one happy camper.
 

[shooter]

Id like having the tube rectifier.

save it for PP builds, In xSE you want rock solid SS power supply.  "sag" can be had with under-rated OT, where core saturation is a thing, think 5F1.

If you're "starting over", skip ahead n just go for the big bottle choices.  2 12XX7s and a KT88 WILL be LOUD, have tone to spare, there are probably 5-10 examples we've built here.
A 6L6 is a good tube, I went down your road, started with a 5C1 6V6, went pSE, moved to pSE GA-8, then went to pSE 6L6 GA-8.  Then I did a KT88 SE, never going back, except for big bucks 

[DummyLoad]

i have had no issues with ||SE: have an amp built in 2006 that's been running with lop-sided 6V6s since built - that was done on purpose for tone. also have a ||SE EL34 built in 2014 that's also still running trouble free.

agree, single would be more reliable; fewer parts, but i don't think that the issues with your amp are due to simply being in a parallel SE configuration. e.g., your amp has other issues, could be design/layout or could be intermittent part(s) fail. lastly are you sure that the cut-out isn't be due to HF oscillation at a frequency you can't hear?


--pete

[echuta13]

I agree with the big bottle idea, but I also think you should consider the idea of going with the most efficient speaker you can.  What is the efficiency of your current speaker? 

[PRR]

Just wire two Octal sockets. Common cathode resistor (probably 270r). Stuff with one 6L6 or two 6V6, as desired.

If PT can support the heater load, one EL34 even 6550 will work, all the same values, no great difference of power. Cork-sniffers may find many "tone" differences across the tubes.

(If you have cats, or children with paperclips, you should fill the empty Octal.)

[bmccowan]

Back to one of your original issues; I was just reading some pages on Cascade Tubes https://www.cascadetubes.com/the-rebuild/- (good site for audio projects) and saw this quote by Matt - its right on point regarding working on a chassis that is too small,

And finally I learned that there is no virtue in forcing myself to work in small boxes. I am convinced that I will never again build a tube project on such a small chassis. There is no need. At times, working on this amp was more of a chore then a relaxing past time simply because I was having trouble seeing what I was doing. And, above all else, I want to enjoy what I do. Life is simply too short to be frustrated when you don’t have to be

Similarly, I got no joy from trying to work in an AO-35 chassis - big difference when I robbed the iron and put them in a reasonably sized chassis.

[SILVERGUN]

Which would have more volume? (Loudness/power)

Single ended 6l6

Parallel Single Ended 6v6

One part of this equation is the ability to drive the 6L6 harder than you could drive the 6V6

For me, this equates to a much louder end product

[shooter]

another part of the equation is the ability of the PA tubes to swing a larger signal.  If Plate volts stay the same and drive signal increases, you increase distortion of that signal.  If B+ is higher, you alow more "clean swing" before distortion.

This becomes a zero sum gain in SE because as B+ goes up current goes down since load "resistance/impedance" stayed constant.  So you re-bias and B+ comes down and and and eventually you exceed plate dissipation enough to shorten tube life.

[PRR]

If plate and screen voltages stay similar/same, 6L6 6V6 EL34 will all need very-similar drive.

The BIG drive is needed when you run the big tubes in push-pull (with low idle current) and jacked screen voltage.

[TurboGuitarMelton]

Sorry for the delay! Ive been moving this past week.


I changed to the 6l6 and I gotta say I like it more! Was a super quick job. Less moving parts and my weird issue with the fizzling out sound is gone. It may have been layout or the power circuit?


I also notice a substantial increase in headroom and bass response. Where the amp used to break up on 7 it now stays cleaner up to 9. Volume seems to be more too. Not by much but by a little bit over the PSE 6v6s. Definitely is noticable over the SE 6v6.


 I am also using the 12ax7 over the 12ay7 so the power section is bring hit a little harder. Everytime I tried a 12ax7 in the normal SE 6v6 champ I found that above 9 it totally falls apart and sounds terrible. The 6l6 helps things stay together.


I usually try to give myself lots of room to build. The main reason I ran into this issue is because I had this chassis that fit the cab and I wanted to use it without having to spend too much extra cash. But I see where that got me.
 

[shooter]

 

I can see a KT88 or bigger in your future 
while you're saving up tip money from playing the new amp, look at some of the SE designs DummyLoad has done on his climb to pretty good amp creator 

[tubeswell]

I like SE 6L6 amps.


(BTW, as a rough rule of thumb guesstimate, you can figure an SE amp output power rating of about 0.4 x the rated plate dissipation of the tube if you have the tube optimally operating in centre bias class A into the optimum load resistance. For a 30W 6L6GC, this is about 12W. For a 6V6, this is just under 5W. For 6V6 || 6V6, 9.5W)

[pdf64]

...For a 30W 6L6GC, this is about 12W. For a 6V6, this is just under 5W. For 6V6 || 6V6, 9.5W)

I think we should beware of treating design max ratings the same as design centre; design max ratings put the onus on the equipment design engineer to derate the tube to accommodate whatever supply and component variation is appropriate.
As that's outside that scope of techs / owners, I think it best to stick to (as you have done) the design center rating of 12 watts for 6V6, but assume a design center rating of ~26 watts for 6L6GC.

I think this RCA application note is the final word on the design centre - design max system definitions http://www.one-electron.com/Archives/RCA/RCA-AppNotes/RCA%201939%20AN-105%20A%20Change%20in%20Maximum%20Ratings%20of%20Receiver%20Tubes.pdf

[66Strat]

I believe that there were actually three rating systems; Absolute Maximum, Design Center, and Design Maximum with Absolute Maximum being the oldest.
http://www.one-electron.com/Archives/RCA/RCA-AppNotes/RCA%201958%20AN-174%20Design-Maximum%20System%20for%20Rating%20Electron%20Tubes.pdf

However, I do believe that the Design Center ratings would be the best to use, especially with new production  tubes. Adhering to Design Center Standards would certainly help to extend tube life. I suspect that current tube manufacturers are referencing Design Center ratings and using them as absolute maximum ratings in the design and manufacture of new tubes. This is just my gut suspicion, but it would help to explain why new tubes are not as robust as they used to be.

[pdf64]

Doh, thanks, that's the one I meant to link to 

[66Strat]

Those different ratings can be very confusing. I noticed the difference between Design Center and Design Maximum ratings when looking at the 6V6 ratings in the RC30 Tube Manual. The plain Jane metal can 6V6, 6V6GT, and 6V6 GTA all had the same plate dissipation rating of 14 Watts. The plate voltage and screen grid voltages were also consistent between the tube types and higher than in earlier tube datasheets that I had seen.

[PRR]

I do not think ABSolute Maximum ratings were published for the tubes we use. They might be released on a Need To Know basis to very important projects, missiles and their computers and servos.

And ABS Max is not in the EIA sheet and may not be the same for all makers. In 1960, RCA might have confidently whispered "All 6V6 made with 500V stuff", while G.E. might have admitted "450V stuff, except at TV peak selling season, when we may have to use 400V stuff". Yes, if you make a Bomark SEX-69 missile controller with 460V on 6V6, you may have to specify "RCA only". Or specify a special non-6V6 number to get the good stuff.

I'll repeat my simple impression. Design Center is for when you hardly look at your actual operating point. When you are making radios as fast as possible with short warranty. You can often reach "good performance" within Design Center. And if that is not enough, you need more than a 13% cheat, you need a bigger bottle. However you can instead consider Design Maximum, BUT check your operating point at every extreme you can anticipate. Got 132V in the badly wired club you play? Will the customer throw 4 Ohm speakers on 8 ohm tap?

[shooter]

Or specify a special non-6V6 number to get the good stuff.

n iirc it's a LONG #
IIRC GE's part numbers were 24 characters but once you understood the cypher
you knew what system, cabinet, rack n board

to the thread;

instead consider Design Maximum, BUT check your operating point at every extreme you can anticipate.

that's what I work from, seems to work well n way easier to remember than 30+ pages of typewriter text 

[pdf64]

I do not think ABSolute Maximum ratings were published for the tubes we use...

The GEC KT66 is a rare exception, 25W design max, 30W abs max https://tubedata.altanatubes.com.br/sheets/084/k/KT66_GEC.pdf

As Aikens 'idle fixed bias AB1 amps at a max of 70% of rated plate dissipation' guideline was seemingly developed around EL34, a 25W design centre tube, I suggest that a lower level would be more appropriate for design max tubes such as 6L6GC, eg 60%.