Stereo SE KT88 power amps for live rig

[SILVERGUN]

I'm considering going back to a preamp/power amp configuration for my live rig. (Mesa Triaxis preamp) http://www.mesaboogie.com/amplifiers/electric/tube-pre-amplifiers/triaxis-programmable-pre-amp/index.html
I played through this for years and got spoiled by the programmability and MIDI functionality. There is nothing like hitting #1 on the floorboard and having everything change all at once.(instead of tap-dancing across multiple stompboxes and amp channel switches)
I'll have a wide variety of music to cover and I really prefer a wide pallet of different tones. When I play live I am playing for me, so it has to sound like what I want to hear. I know the crowd cant tell the difference (Ed).Solid state/modeling is out of the question.
 
I'm also considering building the power amp as a stereo SE EL34 configuration @ approx. 12 watts per side.
Thinking about individual toroids for each channel for PTs (with SS FWB should get me in the low 300s VDC for loaded B+):
http://www.antekinc.com/as-05t240-50va-240v-transformer/
 
And maybe these for OTs:
http://www.classictone.net/40-18031.html
http://www.classictone.net/40-18031.pdf
 
I'm mostly concerned about full output current requirements, because I imagine I'll be running both sides close to full out most of the night with overdrive. The Classic Tone OT is spec'd at 70mA which is right around idle for SE EL34,,right?
- And, I imagine 12+ watts out of an overdriven EL34 pushes much more than 70mA?
- Is OT probably just being conservatively rated and I should be fine or am I risking core saturation and crappy tone as a result?
- Should I just "buck up" and go for something like a Hammond 125GSE (Edcor, etc?)
 
- PTs have a .1 amp (100mA) rating for the HT windings...is that enough?
 
The whole reason to do it this way would be to get the benefit of SE tone (harmonic content) and have a wet/dry mix going through a single 2x12 cab where wet goes into one speaker and dry feeds the other. Power amp would basically be on high output setting all of the time and volume would be controlled by programmable preamp settings. Looking to push EL34s for best sound.
Power amp won't weigh a ton or cost a fortune and power tubes will be mounted horizontally for space savings in a rack/head that I will build. Triaxis/one rack effects processor/power amp all in one head cab.
 
Thanks for reading and thanks in advance for the help. This project will come together pretty quickly once I iron out the bumps and commit.
 

[SILVERGUN]

OK, gave it some more thought and realized I am creating my own current problem by keeping the B+ that low.
Maybe we use these and wind up around 440VDC unloaded
This model reduces available current from the PT to 80mA (this is the 50VA product line)
http://www.antekinc.com/as-05t320-50va-320v-transformer/
 
Next step up would be 100VA product line and is a significant size difference. But I'm seeing 2 separate 350V windings.
Would it be a good idea to use the second winding as a dedicated screen supply?
http://www.antekinc.com/as-1t350-100va-350v-transformer/
 
I guess I need help thinking clearly.

[jjasilli]

Phillips tube chart for single tube class A shows 265 supply voltage > 250 Plate volts; screen + plate draw @ idle is 80 - 115mA depending on configuration.  If you run a quality 70mA tranny @ 50% over spec, that's 105mA, so you're maybe on the edge.


BTW my SE Champ & PP Princeton (latter since sold) sounded identical to me.  I never heard the presence or absence of the second harmonic.

[Ed_Chambley]

I think the TriAxis is a great preamp and I have a similar setup I used for years.  When covering lots of material it is either this or carry 4 amps and 50 pedals.  I have a Rocktron Voodoo Valve I use when asked to play where I may have to cover Van-Halen and Haggard.  Southern folks are like that. That being said, I used to use a Marshall 50/50 which is a stereo 50 watter with ERL34's, but I it is rare that I could get it loud enough to enjoy the EL34 in Push Pull.

What I do now is very similar when I use the Rocktron.  I built a SE EL34 that Dummyload designed.  It is attached and will answer some of your questions.  I do not like it with anything but overdrive/distortion.  Chorus, Delay, verb, basically any modulation pedal doesn't sound quite right.  Too much harmonic content and sort of gets mushy.  But for one side of the stereo it works great.  What I use for the clean side for mixing modulation effects is basically a Princeton.  Basic Push Pull, 2 6v6 with a split load PI, which I find to handle clean well.  I am running a 12AT7 PI tube.

I think you will be very close with 70Ma with a single tube EL34.  I would feel better with a tad more.  The transformer you have linked to may not give you enough headroom to play anything clean at club levels.  That would be my only concern.  It is very difficult to build a clubbing rig to cover all bases, but now days most of the time I am using a processor like the Voodoo Valve or I also have a JMP-1, I am only monitoring myself on stage.  Most sound guys today will prefer a direct line out and the Voodoo has great cab simulation.

I simply consider the clean tone first since it is the most difficult to me.

I believe JoeJoe has an amp he calls the Cherry Bomb which is a SE EL34 that uses the Hammond transformer.  Maybe he will jump in here.  I did a search and did not come up with it.

Glad to see you are planning to play some.  You are correct, the audience doesn't know generally.  Still, you have to have something that inspires you to play.  As they say "tone is in the hands".    So all you need is hands.

I am not trying to change your mind on anything as I like all my stuff all the way down to my Modded Boss DS-1.  I just thought I would mention the lack of headroom may be an issue, but then again you can always mic up if needed for a larger venue.

[SILVERGUN]

BTW my SE Champ & PP Princeton (latter since sold) sounded identical to me.  I never heard the presence or absence of the second harmonic.

Thanks for the input JJ....I was hoping that was not the case.
I was buying into the SE concept without much hands on experience.
 
I still have a PP Mesa Simul 395 that is a beast and is just too much amp to carry around.
 
 
Ed, did you link the wrong schematic?
 
 

[SILVERGUN]

I used to use a Marshall 50/50 which is a stereo 50 watter with ERL34's, but I it is rare that I could get it loud enough to enjoy the EL34 in Push Pull

That's exactly why I cant use the Mesa 395....overkill and just doesn't sound good when you choke it down to a point where you're not blowing people's hair back.
I was hoping to just run 2- EL34s flat out and that would allow me to get the richness of sound compared to 8- 6L6s being held way back.
 
I like the idea of something designed by DL.

[SILVERGUN]

What I do now is very similar when I use the Rocktron.  I built a SE EL34 that Dummyload designed.  It is attached and will answer some of your questions.  I do not like it with anything but overdrive/distortion.  Chorus, Delay, verb, basically any modulation pedal doesn't sound quite right.  Too much harmonic content and sort of gets mushy.  But for one side of the stereo it works great.  What I use for the clean side for mixing modulation effects is basically a Princeton.  Basic Push Pull, 2 6v6 with a split load PI, which I find to handle clean well.  I am running a 12AT7 PI tube.

I guess there is another solution in there...
 
A mixed power amp where one channel is setup to enhance dry and the other to handle wet.
?

 
 
 

[Ed_Chambley]

Sorry, I did link the wrong schematic.  I think this is the one.

[Ed_Chambley]

What I do now is very similar when I use the Rocktron.  I built a SE EL34 that Dummyload designed.  It is attached and will answer some of your questions.  I do not like it with anything but overdrive/distortion.  Chorus, Delay, verb, basically any modulation pedal doesn't sound quite right.  Too much harmonic content and sort of gets mushy.  But for one side of the stereo it works great.  What I use for the clean side for mixing modulation effects is basically a Princeton.  Basic Push Pull, 2 6v6 with a split load PI, which I find to handle clean well.  I am running a 12AT7 PI tube.

I guess there is another solution in there...
 
A mixed power amp where one channel is setup to enhance dry and the other to handle wet.
?

This is the way I always play, even when playing at home.  I have tried loops and like them for some things, but to me nothing beats 2 amps.  If I am playing a traditional country gig, I use the AC15 for my OD side as it is so easy to push it into distortion and a Princeton Reverb that handles clean and modulation effects.  I do like the AC15 Vibrato, but it works well with overdrive.

I prefer it so much that I even have what I call my mini-stack.  That is a Champ on top of a 6 watt Gibson.

[terminalgs]

stereo SE EL34 configuration @ approx. 12 watts per side.

I was hoping to just run 2- EL34s flat out and that would allow me to get the richness of sound compared to 8- 6L6s being held way back

I don't think there is anyway to get 2 EL34's to do the job of what 4 (or even 8) 6L6's would do.   If this is a gig rig, don't you want at least 40-50W in each channel?


If you are trying to save weight, 6L6s over EL34s save you PR iron weight.   A shared PT would save weight too..  Is two bandmaster 2x6L6 pairs w/ OTs too straight forward?   2 12AT7's 4 6L6's, two OTs, and maybe one big PT for showman/twin?


If that's too much weight and output, then I'd scale it down to four 6v6's, 2 smaller OTs and one smaller PT..

[SILVERGUN]

Ithink this is the one

OK, thanks...I can see where that might only be good for OD
 
I was thinking something much simpler, like a parallel 12AU7 pushing a single EL34 per side (?)
The Triaxis can put out a pretty hot signal so I'm thinking the AU7 can handle that without clipping and "maybe" swing enough signal to get the ELs going?
 
 

[SILVERGUN]

I don't think there is anyway to get 2 EL34's to do the job of what 4 (or even 8) 6L6's would do.   If this is a gig rig, don't you want at least 40-50W in each channel?

This won't be like my gig rigs of the past. I'm tired of being too loud and we will be doing classier tunes at restaurant/bar volumes.
It's much more important that it sounds really good to me. Read above where Ed and I talk about having a high power amp and throttling it back,,,just comes off sounding dead/flat.

If you are trying to save weight, 6L6s over EL34s save you PR iron weight.   A shared PT would save weight too..  Is two bandmaster 2x6L6 pairs w/ OTs too straight forward?   2 12AT7's 4 6L6's, two OTs, and maybe one big PT for showman/twin?

All that "would be" OK, but I would probably just wind up using my 395 at that point
 
My original thought was that I "might" get better sound by smoking 2 EL34's ...and I also thought SE would be buying me something in the tone department.
 
How about SE KT88s?
 

[DummyLoad]

ed, that schematic that looks like a PP output stage and not a SE?


--pete

[SILVERGUN]

ed, that schematic that looks like a PP output stage and not a SE?

We got him fixed up DL.....too much preamp in the correct one he posted though  (see reply #7)
 
Got anything for SE big bottle power amp with simple big swing drive stage?
 
Or, wanna talk me out of it?...or into anything else
 
2 separate 1x12" combos that are just setup as power stages aren't out of the question either
 

[SILVERGUN]

Here's a thrown together proposed mockup for each channel...
 

[Paul1453]

That seems nice and simple and easily meets my KISS principle.   

Everything is labeled except the first two resistors at the top.   

Oh, and the cathode resistor on the EL34.

[PRR]

> an overdriven EL34 pushes much more than 70mA?

If the load is correctly chosen, ideally the current does not increase from idle to utter clipping.

With real tubes and conventional audio amp design, current goes up 10%-20%. EL34 will be on the high end of that range because the (useless) screen current goes way up when plate is slammed low.

I do think that any reasonable SE amp is a home (no drummer) amp, can be much heavier than a P-P amp, and doubling-up may hurt your back more than it helps the music. As jjasilli says, if you are gonna slam the piss out of it, the 2nd is totally drowned-out by the 3rd. P-P will make 3rd lighter and cheaper than SE.

Literal 12W is not a reasonable expectation for a gig-worthy SE EL34. That assumes 40% efficiency and running 30.0W Pdiss. I had a hard time matching B+ and load to get 13W out of 6550 working at 39W Pdiss. Yes, at high THD it was 17W, and totally-bent-square it was 21W out, but IMHO an audio amp should be rated for "clean", with overdrive more-or-less assumed.

[SILVERGUN]

That seems nice and simple and easily meets my KISS principle. 
Everything is labeled except the first two resistors at the top. 
Oh, and the cathode resistor on the EL34.

Thanks for having a look Paul.
I needed these guys to help me fill in those blanks...

But PRR just gave me some priceless clarity. His scientifically formed opinion is exactly what I was looking for.
Even though it wasn't what I wanted to hear.
He's got me leaning towards 2 small PP power amps, maybe built into their own 1x12" cabinets (just to lower the number of trips back and forth from my truck)

[Willabe]

Hi SG! 

I know you have a preamp already but Tubenit (and Geezer) built several low powered PP K biased amps that you could maybe just nab the power section? Because of the K bias they would settle in by themselves.
 

They were able to change the rectifier tube (5Y3/5V4/GZ34?) to change B+ and with that change the power tubes (6K6/6V6/6L6GB?) to get a little less/more power. 

[SILVERGUN]

So if I move towards PP I'll probably use the Mesa 50/50 as a template.
But to reduce output I'll drop the B+ and go with cathode biasing....maybe even build in VVR (based on your opinions)

I'm also still thinking about changing the input stage so that it will be less likely to clip the big incoming signal.
How do you like that parallel AU7 stage on my SE schematic?
On the load line that would appear to take a huge input signal with a 300V supply, 22K plate load and 2.7K cath R

My question would be if there is enough gain there for it to make sense?.....and is there any chance it will improve the performance with the Triaxis?
In the past I could never get the Triaxis output dual pot past 3 without seeming like I was overloading the inputs of the Simul 395

[SILVERGUN]

Hi SG! 

I know you have a preamp already but Tubenit (and Geezer) built several low powered PP K biased amps that you could maybe just nab the power section? Because of the K bias they would settle in by themselves.
 

They were able to change the rectifier tube (5Y3/5V4/GZ34?) to change B+ and with that change the power tubes (6K6/6V6/6L6GB?) to get a little less/more power.

Thanks Brad,
Thats how I'm leaning now but probably SS rect with VVR to play around with B+

[terminalgs]

I think you want NFB, a cathodyne or LTPI, a pair of 6L6s and a 20W deluxe OT (on each channel). look at an Ampeg Gemini output section or a BF Bandmaster output section. for me, the cathodyne is a fav for such a project b/c the first stage is an gain stage, and you can easily set the input impedance where you want to match your pre-amps (without thinking much about it...) and no fooling with a coupling cap.. (like you'd do with an LTPI)...

[Paul1453]

I'm also still thinking about changing the input stage so that it will be less likely to clip the big incoming signal.
How do you like that parallel AU7 stage on my SE schematic?

I'm still a newbie here, so.
I was looking at a few simple PP 6L6 circuits to try out.
That is when I first noticed any parallel pre-amp tube wiring.
I'm not sure what is accomplished by this, but in the circuits I was looking at they were only using 3 of the 4 stages available in 2 pre-amp tubes anyway.

I also have picked up on the fact that Hi-Fi tube amps tend to use a 6DJ8/6922 where the guitar amps go with 12A_7 varieties instead.
I know they want very low THD numbers from their amps compared to ours.
I don't know if that 6DJ8/6922 is a tube to be considered in achieving your goals or not.   

[shooter]

PRR just gave me some priceless clarity

He is correct, fwiw, I built a SE that I *ballparked* for KT88, 6550 and EL34, the KT won out.  it's running at 93% max, yields about 16W clean, 23 dimed.  My son uses it for light jazz in a up-scale restaurant.  I used a Hammond 25w UL OT.

[silverfox]

If your not opposed to using a SS PA or powered speakers with a small mixer- I've recently been pondering the viability of PRR's 1/3 watt amp design somewhere on this Forum and coupling it to a 600 ohm matching transformer so that the output could be lined to a mixer. I haven't looked at this much yet so maybe it's a Hare Brain Idea.

Here is one link that popped up: http://el34world.com/Forum/index.php?topic=12454.msg115958#msg115958

silverfox.

[DummyLoad]

attached is a 35W/ch amp using EL34.

B+ called for in datasheets is 375V and Ra-a at 3.4K. here we have slightly higher B+ but we also have slightly higher Ra-a so should be a wash. idle current is 346mA or thereabouts.

i really need to bread board it, but i'm confident it'll work. should fit in 3U rack chassis 16"-17" deep.

a couple of stringers: 1) need to hash NFB value. 2) considering adding a presence control rather than fixed NFB. 

assuming we need higher input sensitivity, we swap V1 for 12AT7 or 12AX7 & replace V1 plate Rs w/ 100K & change R3 to 22K 1/2W.

the power iron is buckish, but hey, at least it's world power-grid friendly and anti-green.

if y'all see any errors, please post up. i'm sure you will... 

--pete

[tubenit]

Pete,

That looks to be a great amp!  You always come up with fantastic ideas.  Bravo.

Silvergun, nice to see you on the forum!

With respect, Tubenit

[SILVERGUN]

attached is a 35W/ch amp using EL34.

Thanks for that DL.!!...looks great and maybe I'll put one channel on my board first
 
I'm leaning more towards 2 separate cabs with one power amp channel and a 12"er in each...basically "powered speakers"
 
 
 

[SILVERGUN]

Pete,

That looks to be a great amp!  You always come up with fantastic ideas.  Bravo.

Silvergun, nice to see you on the forum!

With respect, Tubenit

Yeah he does....
 
And thanks T...It's good to be seen...you guys are the best...all of you

[DummyLoad]

attached is a 35W/ch amp using EL34.

Thanks for that DL.!!...looks great and maybe I'll put one channel on my board first
 
I'm leaning more towards 2 separate cabs with one power amp channel and a 12"er in each...basically "powered speakers"

good to see you back, SG.

that changes things with the power supply. considerably. back to the drawing board... 

--pete

[DummyLoad]

see attached - PT, diodes, caps, and misc. power rail R values changed, changed choke. for 120V/60Hz only option use hammond 272HX.

--pete

[SILVERGUN]

THANKS again Pete!
 
To save some dough and use some stuff I have on hand I'll probably use Doug's stout chassis(s) and 2 PTs I have laying around.
They are 240VAC secondaries (no CT)@ 570mA and it only takes a slight mod to get them in the hole that's already there, and I've got 2 separate filament xfmrs.
So that should put unloaded B+ around 350ish, and it shouldn't budge much. With that lowered B+ I imagine we will enjoy the availability of all that current capacity. (?)
 
I also have a Hammond 1760L OT that's looking for a home 50watts @ 4.2K into 4/8/16 (we can mismatch to half the pri. if you suggest)
 
I'm thinking about using a different OT for one and maybe doing one pair EL34 and one pair 6L6 (or KT88 for fun)

Thanks again for all of your hard work and please don't spend too much time on me until I make up my mind.
But ALL input is much appreciated and taken into consideration. I think this will be a great use for those chassis.
 
Does anyone think I will hear a benefit if I set them up for two different output tube types?
 

[pompeiisneaks]

Question,

I'm still pretty new, so take that with a grain of salt :)

If you're going for a lower output, why not try a tube like the EL84?  I think they're each about 7 Watts max if done right, so for two in P-P it would be 14 Watts, and you could dial that down just like you're talking about.

Or do you just prefer the tone of the tubes you're working with/talking about better?

~Phil

[SILVERGUN]

Question,

I'm still pretty new, so take that with a grain of salt :)

If you're going for a lower output, why not try a tube like the EL84?  I think they're each about 7 Watts max if done right, so for two in P-P it would be 14 Watts, and you could dial that down just like you're talking about.

Or do you just prefer the tone of the tubes you're working with/talking about better?

~Phil

Yeah, I just prefer the bigger tube tone...and I don't really need to go too quiet...it's a fine line between too loud and drowned out
And like PRR mentioned, I will still need to get over a drummer...that got me thinking about 30w in stereo
 
In the end, I might just drop a few db's by using less efficient speakers...we'll see

[pompeiisneaks]

ahh makes perfect sense. 

My AC30 with 4 of the EL84's in p-p has some spank to it, but I do know the EL34's have a bit more than that as well. :)

I'm still learning about what kinds of tonalities each of the tubes have and when might be a time to use tube X.

~Phil

[DummyLoad]

with only 330V B+, perhaps you should consider a quad of 6V6GT. they don't sizzle like the EL84 and they are IMO, a smoother sounding tube than the 6L6Gx family. drive requirements are about 2x that of the EL84. IMO, in this scenario, fixed bias provides best tone.


drive 3.8k load (marshall 50W OT) with 4 6V6GT loafing at 330V you'll make ~30W. big tube sound with 4 little(r) bottles. use all octal toobz including preamplifier... 6SN7 LTPI and 6SN7 1st gain stage.


--pete

[SILVERGUN]

with only 330V B+, perhaps you should consider a quad of 6V6GT. they don't sizzle like the EL84 and they are IMO, a smoother sounding tube than the 6L6Gx family. drive requirements are about 2x that of the EL84. IMO, in this scenario, fixed bias provides best tone.


drive 3.8k load (marshall 50W OT) with 4 6V6GT loafing at 330V you'll make ~30W. big tube sound with 4 little(r) bottles. use all octal toobz including preamplifier... 6SN7 LTPI and 6SN7 1st gain stage.


--pete

Uh-oh...option overload... I'm gonna give it some serious thought and try to stick to one solution...I already had the AU7s pulled out onto the bench for excitement (those I have here...6SNs will cost me and have to get here)
 
I'm not locked into those transformers for this job, so if B+ needs to be higher for best results with 6L6/EL34, I might just invest....
 
I'm gonna take a couple days and get the board up and running and see where I am.
I'm slowly talking myself into the idea of mixing one side 6L6 and the other EL34 and then just see which does the dry/wet better than the other
 
I am pretty convinced now about these as just separate little power amps in the stout chassis, because I sat one on my thiele cab and it fit perfectly with the width of that cab....I already have the plywood cut for an identical cab so I'm thinking of mounting (or temp mount) or piggybacking these to the top of those cabs and just finish off the tops with a wood cap. (or robot helmet, etc..)....(kills 2 with 1....solves the cabinet issue and makes my decision for me)...they will be heavy but not tooo bad.
 
Maybe leave the Eminence EM12 in one for the wet ,,and then figure out the speaker for the dry by trying them out  together?..(good spot for a Creamback? jojo?)
Please stop me if I go too far off topic DL..................
 

[SILVERGUN]

Now that I've looked at that pic I'm starting to think that I could just try that little Deluxe Champ Reverb, and make a "power amp in" and switch the preamp tubes to AU7s.
Try that for one side with an EL34 in place of that 6V6 and just hear it.....hmmm
 
There's plenty of current avail. on that amp because I used those same PT and fil. transformers I mentioned earlier
It also has the Classic Tone 15W OT,,,so  maaaaybe I'll see what happens with one side SE and the other PP??
 
...sorry DL...I ain't done thinkin yet
 
 
Ed, in your wet/dry rig, do you run your wet amp 'just as loud' as your dry amp?...or do you think it might be OK to have a SE side wet that is not as loud as the PP dry side?

[Paul1453]

Silvergun, you are starting to sound like me.   

I want to make this, or maybe that, or what if I combined all three?   

I'm just kidding you.   

But I did think you started out looking for a SE output sound?  No???

If you are wanting SE that can compete with drums, that kind of narrows things down to a bigger bottle output tube.  Right?
No EL84 or 6V6 SE output is going to work.

Then your preference of the sound of the output tube is probably more important than the max watts you can get from it.
Do you know if you like the sound of the EL34 better than a 6L6 or one of the other big output tubes?
If you know that you want SE output and that you like the sound of the EL34 best, then you can focus in on those designs to get the sound you're looking for.  Maybe 
 

[jjasilli]

I play in small to medium size bars & venues.  I find a PP small bottle amp to be way to loud.   I agree that the drums rule the volume range.  But if the drums are scaled to that size venue, then IMHO a Deluxe Reverb, e.g., is overkill.  If the drum set is too big (loud), then no one in the venue will be able to hear themselves think.  This may depend if you're putting on a concert, or providing more low key entertainment.

So, I agree with Silvergun that a stereo SE amp putting out a combined total of 12 - 20W can work fine. 


Harmonic density aside, stereo SE amps with big bottles can do that.  (Personally I'd like to go with KT-88's, but what the heck.)

[SILVERGUN]

Silvergun, you are starting to sound like me.   
I want to make this, or maybe that, or what if I combined all three?   
I'm just kidding you.   

You got me Paul...there's always some truth to joking and I see where you're coming from...
Hopefully this will be a one shot deal for me and I can get back to actually playing guitar instead of talking about sound....
 
I started out thinking that I 'might' want to do SE, but after some input from the gallery (of very talented and knowledgeable folks) I have reconsidered..
But as we move through the thread I realize that the extent of possibilities is only limited by my imagination and desire to push.
 
There are a couple of things that we have resolved:
- I will use 2 of Doug's Stout chassis (I already have 1 here)
- I have backed away from the stereo SE (rackmount) idea and am leaning more towards 2 individual power amps with different qualities
- I've never heard 6V6s do what I want so I'm sticking to either 6L6, EL34, or KT88 (because I have them on hand), and probably 12AU7s as driver tubes because of their ability to handle big signal (and I've got some nice ones here)
 

[Ed_Chambley]

^ +1
Even if you have a drummer, most places are not going to allow the drummer or band to get loud these days.  For instance, I play small place every other weekend pretty much.  The drummer is either using brushes of just letting the sticks drop.  In this case a Princeton Stock can be too loud.  The ONLY time I get to ever use big bottle amps anymore is outside festival gigs, and even then I don't really need to.  I like to tho as I don't get a chance to often to use them outside my amp room.

I don't know where you will be playing, but most Bars these days around town are 5,000 sq foot or less.  Stop by guitar center and plug into a Deluxe Reverb in the middle of the store and turn it up to about 5 where it should be played and see how pissed everyone in the store gets.

This is the problem with trying to build a rig that will work everywhere.  For instance, if I play at the Brickhouse which is a Restaurant that turns to a Bar at 10 pm.  Playing starts at 9.  The first 2 sets are played at background volumes and traditionally all the ballads are played during dinner time.  After the "family" crowd leaves and the average age becomes thirtysomethings and old drunks, then we can rock.  Even then my amps sit behind plexiglass.

We also have a set of Roland V Drums and use them to play Irish Restaurant and I am using my mini stack which is a 6 watt Gibson and a Tweed Champ.  I only know of 3 places in my area that have live music where the venue is large enough to use a 50 watt amp.

When the venue is large enough for bigger amps they usually have a sound system and you can mic up.  For instance, I went to see Marty Stewart who IMO has one of the best tones in Country.  It was at The Smokey Mountain Theater and he was using a Princeton and Kenny was using a deluxe.  There you can walk right up to the stage and Kenny's Deluxe was on 4 with Bass on 2 and treble on 6 and Marty's Princeton was on 6 with the Bass almost off and Treble on 7.

I have experienced about the same.  I have also seen when bands turn up too early, people leave and they do not get hired anymore.  In the 70's and 80's things were different as clubs were larger and music was louder.  I just mentioned the I focus on getting a great clean tone and live with the fact that my overdrive is going to come from a pedal and or a small preamp tube.

I have seen it too many times.  Just last weekend at a club called mixers group of aging long haired won't let go of the 80's come in and setup to play.  During the third song I saw the lead player turn up his 50 watt Peavy and within minutes the Drummer and Bass Player jumped up as well.  The second guitar player was using a 7 string with a Crate Blue Voodoo and a full stack.

I do not know what the 4th song they played was because the people I was with were not willing to take the punishment and scream at each other to hear.

All this being said, I have had problems using 2 SE amps and not having enough headroom.  That is why I mentioned this.  Of all the stuff I have to gig with the vast majority of the time is it is the AC15 and Princeton.  El84's and 6V6's do not sound as good as 6L6's and EL34's to me either, but I do get called back to play whereas I can assure you the band I saw last weekend will not.  They are called Broken Glass.

Just thought I would share my experience with current gigging.  I believe jjasilli has found the same to be true.  If I lived in Austin or Memphis things may be different.

[SILVERGUN]

I play in small to medium size bars & venues.  I find a PP small bottle amp to be way to loud.   I agree that the drums rule the volume range.  But if the drums are scaled to that size venue, then IMHO a Deluxe Reverb, e.g., is overkill.  If the drum set is too big (loud), then no one in the venue will be able to hear themselves think.  This may depend if you're putting on a concert, or providing more low key entertainment.

So, I agree with Silvergun that a stereo SE amp putting out a combined total of 12 - 20W can work fine. 


Harmonic density aside, stereo SE amps with big bottles can do that.  (Personally I'd like to go with KT-88's, but what the heck.)

Thanks for stoping back JJ...
I'm thinking it might be cool to do 1 SE KT88 and 1 PP 6L6/EL34 with VVR
 
But since I can only build one amp at a time I will lay out the SE idea on my smaller breadboard and see where that gets me.
At some point I realized that this is why I built those boards in the first place, and I cant get attached to one circuit on the BB and allow it to block me from moving on....they should also be able to give me some real world volume answers. (it would be pretty funny to see a breadboard sitting on top of my speaker cab next to my drummer)
 
I'm gonna need help choosing a "best" OT and figure now is not the time to be cheap....Hammond 125GSE for KT88 (or what?)
 
Is it super silly to do low B+, high current?...like SE KT88 with 330V B+
 
...very loosely based off of the numbers below and whatever you guys can give me
 
 
 
 
 

[SILVERGUN]

Just thought I would share my experience with current gigging.  I believe jjasilli has found the same to be true.

Thanks for all of that Ed...it has been quite some time since I've been out there, and the goal with this band is to not annoy people.
 
JJ mentioned "low key entertainment" and that's where I want to be, but I think reality will force something more like "moderate key entertainment"
We won't be a party band and I won't be covering VH....more smokey blues, soul, some classics....lounge 'y
 
I have already been in negotiations with my drummer to soften the hitting, deaden the kit, and I already have him surrounded in a movable Plexiglas surround...next step might be "adjusted" sticks (there seems to be some different options out there), last ditch effort will be an electronic kit.
 
The good news is, I plan on limiting this to one night a month in one or 2 clubs that I can choose from. So the rooms will really dictate the outcome.
 
My adventurous spirit tells me to see what an SE KT88 sounds like. (something like shooter's reply#23)
 
I'm wondering what ideal conditions will be and what kind of drive I will need to get one cooking (?)

[SILVERGUN]

Slightly off topic but proof that I do remember how to use my scope and meter:
 
I took that little amp in the picture and measured output wattage...
(I used an 8 ohm resistive load on the output. I connected a scope and a true RMS meter across the load. I have the amp set with volume and tone controls maxed. I put in a .5V signal and test at 400hz. I raise the gain control on the amp until the output waveform is at max amplitude, just as it starts to flatten out on the peaks. I take the voltage reading from the meter and calculate watts as voltage squared divided by 8 ohms. )
 
That came out to 5.5VAC x 5.5 = 30.25 / 8 (ohms) = 3.78 watts
new JJ 6V6S
Operating conditions at that output:
303VDC plate to K
298 screen to K
37 VDC across 1K cath. resistor @35mA
11W pdiss (?)
8K primary with 8 ohm load on 8 ohm tap
 The point of this experiment was: 
- to show you that this is not all talk
- to show you the 'relative' expected voltages if I wind up using one of these PTs
- AND to try out the KT88,,,but the problem there was that I also realized that this amp does NOT have the 15W OT in it, so it will not work for the quickie big bottle experiment.   
 
And then I plugged it into a speaker cab to see just how loud 4 watts can be.... And, I did come to the conclusion that an SE KT88 operating around 15W ish clean "should be" plenty loud for this application....(and I can highlight that with a more efficient speaker if needed).   
Before I buy an SE OT...any thoughts??...anyone want to donate one to science? (I'll post a 'wanted to buy' over on Doug's buy/sell/trade)   
If I'm being really silly with the low B+ please say so, and I'll get over it, and we can move on. I'm imagining that it's a good way to keep the max. output down. (and again, I have these PTs here, and they can handle the current) But I guess we should resolve B+ before we try to pick primary K   
I don't see any internet archived operating conditions for KT88 @ 290V plate ....is that because no one is dumb enough to do it?

[Paul1453]

I tend to be all over the map with my amp ideas.   

No harm in trying different ideas out on the breadboard, though.

If your not building something for a paying customer, there is no rush.

Take your time and explore your ideas.  You might discover something new that the rest of us will be interested in.   

[DummyLoad]

it will work.

with 6550/KT88 @ 300V you'll need about a 2K load. 2.5K is close enough and will work.

i have a one-electron UBT-2. it's 4.8K at 4/8/16 or 2.4K at 8/16/32. since you built the cabinets for us at such a great price, for you 25 bux plus ship if you want it. i have several so it's nothing that'll be missed. if your transformers are 240V sec. then you should see about 335VDC unloaded. loaded around 310V. MAX idle current through UBT-2 is 120mA - use caution! 

http://www.one-electron.com/Trans/UBT2_10.pdf

--pete



EDIT: added 6550 single tube parameter from GE spec. sheet.

[pompeiisneaks]

I don't see any internet archived operating conditions for KT88 @ 290V plate ....is that because no one is dumb enough to do it?

Here's me trying to sound smartish... From the datasheet on the KT88, the max anode voltage is 800, and from the one I found 250 is average plate.  The datasheet also shows that the most voltage you'd want to push is about 400V at a -4 V bias point.  I would bet that -4 is way too cold of a bias to do you good per my understanding of bias...

If I understand some about design and spec sheets, 290 V should be perfectly fine if the typical is 250V:

http://free-hosting.infodiv.com/audiotube/power_tetrode/power_tetrode0034/kt88-jj2003.jpg

or are you talking more of some advanced topic I don't yet understand :)

Ignore me if I'm off in left field lol

~Phil

[SILVERGUN]

i have a one-electron UBT-2. it's 4.8K at 4/8/16 or 2.4K at 8/16/32. since you built the cabinets for us at such a great price, for you 25 bux plus ship if you want it. i have several so it's nothing that'll be missed. if your transformers are 240V sec. then you should see about 335VDC unloaded. loaded around 310V. MAX idle current through UBT-2 is 120mA - use caution! 

http://www.one-electron.com/Trans/UBT2_10.pdf

--pete

SOLD
I sincerely appreciate that offer and I would be have to be pretty slow to not take you up on it.
That thing is BADASS!
 
If for no other reason than I cant perform any experiments without an OT
 
I'll catch up with you on PM and Paypal
 
In the meantime I gotta get a parts order going......

[SILVERGUN]

If I understand some about design and spec sheets, 290 V should be perfectly fine if the typical is 250V:

http://free-hosting.infodiv.com/audiotube/power_tetrode/power_tetrode0034/kt88-jj2003.jpg

or are you talking more of some advanced topic I don't yet understand :)

It's my own lack of experience with SE and KT88 that is creating my line of questioning.
 
Won't know how it truly sounds until I hook it up. And that's gonna be the important part....numbers/schmumbers