It's raining here.......

[Willabe]

I had attached the filament wires and then bent the tabs back to get them out of the way.......REALLY BAD IDEA, because it snapped right at the bend!

Now you know. Those pins aren't made to be bent like that. At 1st I just thought you had a bad 1.

And now you know to check the socket from the top side if you still can't get heater voltage.

Your building a library in your mind filled with hands on experience, that cost, time. Such is life.

Your being to hard on your self.


                  Brad        

[sluckey]

Have you fired this up yet?

[SILVERGUN]

Have you fired this up yet?

Not since the socket went....
I didn't realize that the ceramic sockets would fit right into the same holes I punched for the Belton's (the Belton holes are bigger, but the ceramic sockets have these little wrap around wings that seem to fit the hole OK)

I was so mad that I had to back off. 

I'm hoping to have both sockets replaced tonight.

[SILVERGUN]

WOW!!!
IT IS ALIIIVVE!!!!!!!!!!!!!
 

Very little issues to overcome....
Big, bold, bad-ass....better than it was on the breadboard, because I'm not competing with noise...

I can't stop playing it long enough to type anything of any real substance,,,but I'll say this...
Our concerns have been erased!
I'll plan on doing some recording tomorrow night 

[SILVERGUN]

I snapped this pic on the way out the door, from my phone so my wife could see what the "problem" is... 
Sorry it's out of focus 

sluckey, you can see where I mounted the relay directly behind the front panel switch,,,,and the footswitch jack is right there on top as well so all of the wiring was pretty tight....

I'm very excited about how this turned out!.....and a little surprised 

Still some work to be done,,,but the sound is there

[Tone Junkie]

Bravo SG congrats on the good looking amp.      I love a good high gain amp so I'm green with envy.
Bill

[sluckey]

I never doubted you for a minute. Actually looks very good. That little Hammond is really stuffed! Good job.

[Ed_Chambley]

 


Nice work.  Lots of preamp tubes and I will bet none are for reverb or tremolo.


I agree, you have a ;ot crammed in that chassis.  A couple of speakers and you will have the Fire Cube.


I truly love El34's.  Great Job!!!

[SILVERGUN]

THANKS GUYS!!

There's that moment when you flip the standby switch and you have a moment of silence because you haven't moved any of the controls off of zero,,,and then slowly you bring up each control until you have a sound,,,and then you turn the important ones towards 10 and wham,,,the moment of truth.

Well, it works,,,, so I can get to work figuring out where I made a couple small mistakes....we'll talk about those in a bit...

I'm working on cleaning up the schematic, and scanning in my sloppy, scribbled layout pages, that I wouldn't suggest anyone else follow.....
I've got 2 boards in there,
One that's directly over the preamp tube sockets, as a "power board", with holes cut out around the preamp tubes, where the plate supply comes in and the cathodes go to ground...
And the a "signal board" where everything else is mounted...
Pics coming in next post.

Nice work.  Lots of preamp tubes and I will bet none are for reverb or tremolo.

I agree, you have a ;ot crammed in that chassis.  A couple of speakers and you will have the Fire Cube.

It's only been a short amount of time ,,,but you know me....
Although I do like reverb and tremolo,,,they weren't called for here,,,so that left me plenty of room for high gain...

"Fire Cube" sounds like a good name....maybe I'll mount a fire extinguisher in the bottom of the cabinet. 

[SILVERGUN]

I realize that this is all out of order, and maybe I should eventually make a new thread,,,

But here's a shot of the "signal board" for anyone who's curious....

I have adopted the technique of wrapping the component leads around the turrets, for a mechanical connection, and leaving the tops of the turrets open for inserting wires....it just works for me

Under the board pic I attached my hand drawn layout for that board....it was full size so I had to paste it together and reduce the size to get it to fit, but I think it's ok and pretty accurate....
Sorry for the scribbled mess,,,but that's as far as I go with my graphic design at this point. 

EDIT--I had to crop it down to fit under the file width limit.

[jojokeo]

  SG, I've been down after a little shoulder surgery and find this thread with great interest, amusement, and enjoyment. Just what I needed as I'm just beginning to hold a guitar & a soldering iron again.  All the regs have showed up with their 2cents too and the diamonds in a goat's ass is hilarious. Too bad that little Diago amp had to be out there. I love it. Ed, classic - (what the heck does he have scheming now?). Also, it appears SG & Ritchie are playing nice aside from corncobs?  warms a person's heart. Willable you kept the focus of this thread going well, I'll take a hotdog and a beer please! And Samardjia too while you're at it. I live the land of Trout and Pujols  and we could use a young gun like him.
I've had the ol' filament issue before and is why the pre-checking as you go is always a good practice isn't it? Stitch in time...but you were sort of double hoodwinked with that cheap-ass pin design. The extended OT wiring can carry lots of current and mess things up but doesn't appear to be an issue!? You really did something here SG in thinking outside and inside the box which I really appreciate and applaud, not that you need my approval or anything.
So one of my big questions is does this have any semblance to your holy grail Bogner Ecstacy pre in it? Inquiring minds wanna know. I also didn't see but one potential voltage divider aside from the pots of course so wondering if you've tried the split plate load resistor technique or not? Sorry, I've been a bit out of the loop as it's been a little hectic the last couple of months but I still drop in for a couple bottom turns when I can peeking through the green room.

[SILVERGUN]

You really did something here SG in thinking outside and inside the box which I really appreciate and applaud, not that you need my approval or anything.

And I really appreciate your praise my friend....there's no way that I'd be this far along without your initial help and direction, and I truly THANK YOU for all of your help and support on and off the forum. Thanks for taking the time out of your life to share this gift with me.....priceless!

So one of my big questions is does this have any semblance to your holy grail Bogner Ecstacy pre in it? Inquiring minds wanna know. I also didn't see but one potential voltage divider aside from the pots of course so wondering if you've tried the split plate load resistor technique or not?

Yes and yes...Bogner is in there and I did try the split plate load stuff, but it's not in this design...

The schematic is coming just as soon as I can get it cleared up and looking like something I would want to look at.
It took 2 months of on and off tweaking, with the help of a couple of local players to get this to where it is, so the schematic had to be reverse engineered from the resulting breadboard layout......
And it was noisier than a room full of soccer moms when it was on the breadboard,,,so I was a little scared about trying to jam it in this box....
So that's when I got the big idea to separate the boards, and try to separate the preamp tube current from the signal....and just give myself more room to work.....that's where some of my "innovation" bit me in the ass, because I spent more time trying to not make a mistake, while not following any other template.

But we got here, and now it's just finishing touches...
There are a few small problems to overcome, but it's got the monster tone, and it is gonna fly.
This is as far as I could imagine anyone would ever need to push gain, and I'm still shocked that what comes out of the speakers doesn't mush up or get "blocked"
The clean channel is based on the 5E3, but also shares the 'tubenit style' active effects loop which adds some gain... so it's hard to call it clean at all....but that's ok, because 'she' doesn't care...it would actually qualify as high gain for most guys that consider a half-cranked T-wreck as high gain....
I did LED cathode bias on the one triode that is dedicated to the clean channel, and that LED is mounted near the input and also acts as a standby power indicator....when you take the amp out of standby, the 1.7v drop across that LED causes it to light and that's how she'll know it's time to ROCK!
(thanks to sluckey, Merlin, tubenit, HBP,  etc., etc.,)

This project started because I took the Sovtek/Bogner head into a local store and a couple of the guys were raving about it....
But this girl kinda stood back, and said it wasn't her thing.....too bright, not enough gain  , not enough d'jent (look it up, it's an actual word)
And I asked her to show me what she meant, and she plugged into a Marshall JVM series and proceeded to rip my face off....and my BIG MOUTH opened,,,and I said "Yeah, I can do that" 

So I researched the 'Greatest Metal Amps' and "borrowed" every single schematic I could find and stared at them for about a week...and thought to myself "You could do that".....and that's when the breadboard came in very handy 

The high gain channel is a culmination of everything I have "learned" 
It is VERY bass heavy, and shares a modern NFB 'contour' control that compresses everything and tightens it up to the point of feeling like a completely different amp at one end of the dial to the other.

If you've ever wanted to push the outer limits of the highest of high gain, with no pedals in front.....this might be it. 
It would be very easy to bring some highs back in if it turns out to be too dark.

Also, it appears SG & Ritchie are playing nice aside from corncobs?

Yup,,, Ed, sluckey and Willabe vouched for him so now he's OK 

[Willabe]

I know he's just hiding in the bushes until I post a sound clip....then we'll see how "nice" things are.

I don't think that's true, I think he's been very encouraging to you and has been complementing your work and ideas. He's for you and your builds.

And Ed, he's just goofin around with you a little. He's in your corner too.


                Brad      

[sluckey]

And Ed, he's just goofin around with you a little. He's in your corner too.

We all are. But when you step that far outside the box you gonna get a little ribbin' from people who like you.

[SILVERGUN]

he's been very encouraging to you and has been complementing your work and ideas. He's for you and your builds.

We all are. But when you step that far outside the box you gonna get a little ribbin' from people who like you.

I know,,,and I'm very lucky that you guys have accepted me and ALL of my "Philly" ways

Check the edit,,,,some day I'll learn when to 'leave well enough alone' the first time 

Rib-away 

I knew this was gonna work all along.....

[Willabe]

We all are. But when you step that far outside the box you gonna get a little ribbin' from people who like you.

Yes, much better said!


         Brad     

[Willabe]

WOW!!!
IT IS ALIIIVVE!!!!!!!!!!!!!
 

The main chassis turret board and wiring looks great! And it fly's!

Very Nice!


               Brad     

[Willabe]

SG, I've been down after a little shoulder surgery and find this thread with great interest, amusement, and enjoyment. Just what I needed as I'm just beginning to hold a guitar & a soldering iron again.   

Glad your feeling better jojo and yes, I agree, very nice thread.     

SG took a chance at thinking outside the box and did manage to land on his feet.            

Nice work SG!     

I'll take a hotdog and a beer please!

You got it! You know in Chgo, mustard, NO ketchup!

But, wait, what, no Cracker Jacks? You do know there's a prize in every box?         

And Samardjia too while you're at it. I live the land of Trout and Pujols  and we could use a young gun like him.

Nice, our best pitcher, come and pick our bones please.                  


                  Brad        

[Willabe]

Hey SG, now that the amps sounding fine and flying high, has it stopped raining there yet?

Bet it has.   


                 Brad     
           

[TIMBO]

BLAH BLAH BLAH  YEAH YEAH very nice ............................

TUNES man TUNES, SG...SG...SG............................

[Willabe]

BLAH BLAH BLAH  YEAH YEAH very nice ............................

TUNES man TUNES, SG...SG...SG............................

                 



                Brad     

[Ed_Chambley]

Ok great, I cannot see much in your drawing.  Tonestack looks very Marshall like, but is that a 68K slope?  Cathode driven?


What is your OD circuit and where are you inserted?  Is the OD switchable or simply part of the dirt channel?  I assume 12AX7 to 12AX7?


What EL34 plate voltages?

[tubenit]

SG,

You've done a VERY cool thing here with this build!  Coloring waaayyyyyy outside the lines and with success.  Bravo!

Look forward to sound clips.

With respect, Tubenit

[jojokeo]

SG - you're too modest and deserve all the accolades. Nobody can just short-cut their way through all of the things involved, the learning, the learning process (aka school of hard knocks), etc. it all takes a lot of time and dedication unless one has the non-volatile RAM memory of a CPU chip? So take all the credit deserved for not just learning at a rapid pace but while adapting & improvising along the way too!

Sluckey hit the nail when he described it perfectly as a breadboard amp or was it "Old McDonald's Farm"? To me it's more like Young Frankenstein since it's rather Abby Normal in it's building but since it was made for young woman it seems more fitting as the Bride of Frankenstein or simple Frankenbride? Even go with lightening bolts running across each side of the cab (see photo)? But call her whatever you want SG...I'd love to eventually hear this thing being played by the lucky red hot female shredder of which you speak of??? That would be really cool.

Willabe - definitely no Ketchup or Catsup or whatever red stuff unless maybe it's Tabasco or some other hot sauce??? Now we're talkin' gourmet dogs??? I've been eating Craker Jack since I was knee high to a grasshopper but the surprise inside ain't what it used to be. I've heard speculation that the Cubbies are going to be sellers soon with Jeff's name being dropped but you never know? Epstein is no dummy and could get a few quality guys in return.

[SILVERGUN]

SG,
You've done a VERY cool thing here with this build!  Coloring waaayyyyyy outside the lines and with success.  Bravo!

THANK YOU Sir,
You have been a HUGE influence on me and my desire to not just take the easy path.
I have learned a TON by reading your threads and questioning everything.....and because of that, this is much more enjoyable for me than if I was to just build a couple kits and be done.
This is now a lifetime hobby that I can plan to take into retirement,,,even if that is 20 years away 

Ok great, I cannot see much in your drawing.

Sorry,,, that was just meant to show you what was on that board,,,and how I work off of chicken-scratch drawings

I'm still working on the preamp schematic, but I'm very close.....it will take care of most of your questions.
Haven't even started the power amp page, but the only thing special there is the NFB filter circuit, which is connected to the 'contour' control, and is a serious scooping device.OD channel is a tweaked Bogner, all 12AX7, cathode driven tonestack, 68K slope......nothing really all that special, except a 470K resistor between the treble pot and the OD volume, that is worth noting....
I'm not sure exactly how it works but it definitely cuts some highs and seems to change the overall dynamic between the treble and bass controls.
It was one of the tweaks I found to cut some highs that she didn't want.


I wrestled with grill cloth for about an hour last night, so I didn't get anything recorded,,but I plan to dedicate some time to it tonight,,,TIMBO 

Here's another shot of some high quality chicken scratch from early in the process  (just for laughs  )

[SILVERGUN]

Hey SG, now that the amps sounding fine and flying high, has it stopped raining there yet?

Bet it has.   

You know,,,that's been one of the toughest parts...
Spring has sprung, and it has been very difficult for me to stay inside and get this done,,,even if it is after work.

Sometimes I'm here working alone and thinking "I'm the only idiot in the world who is doing THIS right now"

But then I saw what Ed, lego and sluckey have been up to and that has helped fuel the fire....

[SILVERGUN]

Here's a pic,, and my last known drawing of the power board layout....a couple values changed since this drawing, including the LED cath. for V1b (not pictured)....I replaced the 10uf/ 2.2K cath. on the second stage with the red LED that Doug sells in the little chrome housing.

I just figured you guys would find this stuff amusing, if nothing else 
 
Again,,,I would not try to duplicate this, because I was fixing things on the fly, so this is definitely a "one off"
If I had to do it again, I would put the grid leak resistors on the power board, and attach the grid stoppers right to the socket pins without using turrets.
THAT might actually be a cool thing to try.

This board makes the amp very difficult to work on, and whoever has to replace a preamp socket is gonna want to pull my jersey up over my head and take a 5 minute major. 

[Ed_Chambley]

Here's a pic,, and my last known drawing of the power board layout....a couple values changed since this drawing, including the LED cath. for V1b (not pictured)....I replaced the 10uf/ 2.2K cath. on the second stage with the red LED that Doug sells in the little chrome housing.

I just figured you guys would find this stuff amusing, if nothing else 
 
Again,,,I would not try to duplicate this, because I was fixing things on the fly, so this is definitely a "one off"
If I had to do it again, I would put the grid leak resistors on the power board, and attach the grid stoppers right to the socket pins without using turrets.
THAT might actually be a cool thing to try.

This board makes the amp very difficult to work on, and whoever has to replace a preamp socket is gonna want to pull my jersey up over my head and take a 5 minute major. 

Very nice.  I like monster amps.  What you say we take the baby and hit her will about 30db of boost for about an hour or so, just to hear it roar.

[SILVERGUN]

What you say we take the baby and hit her will about 30db of boost for about an hour or so, just to hear it roar.

Geezz....As is, I can't even get the Master past 3 without crying for my mommy....last night I sat and dialed it around with the Master on 1 and I got some ringing today.
WE ARE OLD!, and this is a young man's (girl's) amp..

There is no need for any boost in front of this thing....if she says it doesn't have enough gain.....NO,,,,she wouldn't possibly 

I am looking forward to trying a 10-band MXR EQ in the loop....I think that will make for a nice EQ'd solo boost when she needs to step out front, and fill in some of the mids she scoops out for heavy rhythm riffing.

[Ed_Chambley]

What you say we take the baby and hit her will about 30db of boost for about an hour or so, just to hear it roar.

Geezz....As is, I can't even get the Master past 3 without crying for my mommy....last night I sat and dialed it around with the Master on 1 and I got some ringing today.
WE ARE OLD!, and this is a young man's (girl's) amp..

There is no need for any boost in front of this thing....if she says it doesn't have enough gain.....NO,,,,she wouldn't possibly 

I am looking forward to trying a 10-band MXR EQ in the loop....I think that will make for a nice EQ'd solo boost when she needs to step out front, and fill in some of the mids she scoops out for heavy rhythm riffing.

I am speaking in terms of testing with the boost.  See how well she holds together.  I have a sort of kind of JCM 800 thingy with 4 of those el34.  The one I mentioned having loads of plate voltage.  I put a 18db in front and ran it wide open and she held on for about 5 minutes and started frying bacon and I had to let it cool a bit.  Has all really high end stuff in the build.


Remember, I have an amp room so volume is no biggie  I put off building one for years, but I have to say it is one of the best pieces of music gear I own.


I am interested in the overdrive.  Did you get it mostly from a Bogner Ecstasy?  I really like real Bogner amps.  Everything about them.  Just very versatile and do not really sound like anything else.  First amp I ever heard that had a great clean that would get a great overdriven tone and everything in-between.


I guess everyone wants to make a good living, but I always hate to see using the Bogner name on a Line 6 amp.  I like Line 6 products, don't get me wrong, but the 2 design ideas are worlds apart and sound like it too.


You mentioned a 5E3 for the clean.  I do not really see it.  What did you mean?


And lastly, don't you think it would be easy to put a tube reverb in the chassis?

[Stankfut]

Hey, I've been following you build for a while, and the anticipation is killing me!!!! Need to hear how she sounds!

[SILVERGUN]

1) I am speaking in terms of testing with the boost.  See how well she holds together.  I have a sort of kind of JCM 800 thingy with 4 of those el34.  The one I mentioned having loads of plate voltage.  I put a 18db in front and ran it wide open and she held on for about 5 minutes and started frying bacon and I had to let it cool a bit.  Has all really high end stuff in the build.

2) I am interested in the overdrive.  Did you get it mostly from a Bogner Ecstasy?  I really like real Bogner amps.  Everything about them.  Just very versatile and do not really sound like anything else.  First amp I ever heard that had a great clean that would get a great overdriven tone and everything in-between.

I guess everyone wants to make a good living, but I always hate to see using the Bogner name on a Line 6 amp.  I like Line 6 products, don't get me wrong, but the 2 design ideas are worlds apart and sound like it too.

3) You mentioned a 5E3 for the clean.  I do not really see it.  What did you mean?

4) And lastly, don't you think it would be easy to put a tube reverb in the chassis?

1) I'm not quite there yet....although I never would of thought to run it that hard.
I would expect it to fail with that kind of abuse....and that's kinda why I was thinking of lowering voltages across the board.

2) Actually, my interest in Bogner came from one of his recent Line 6 products, that was labeled the Bogner Alchemist....
I took it into the iso. booth at GC and loved the overdrive....but after reading more about it, decided against buying it because of the problems that people were having with service, and I hated the idea of it being a joint venture with Line 6.
And that's what cemented in my brain the idea of wiring whatever I could find of his,,,,and that's where the Ecstacy experiments came from,,,and that's what eventually led me to this.
Before that, I had only heard his name and never was fortunate enough to plug into any of his products....

But,his overdrive is my overdrive. I'm not delusional enough to believe that I could do it any better....I just take his stuff and tweak it to my taste.
This amp is derived from what I learned from the Ecstacy experiments and what I gathered from a couple Ubershall schematics.....mostly Uberschall.
I just had to decipher them and strip them down to a useable form.

3) I just tacked the simple 5E3 clean on there as a simple clean channel, because I didn't have enough room for anything more,,,and why not include a proven winner?  ....you'll see it on the schematic
I used the pot layout and tone cap connections from sluckeys Tweed on his website, and just added a master before the effects loop.

4)  ....yeah?,,and while I'm at it I could add some tremolo?...
     I could just tack on a couple more terminal strips?,,,and maybe another chassis?,,,and mount the reverb tank on the back?...

Hey, I've been following you build for a while, and the anticipation is killing me!!!! Need to hear how she sounds!

Thanks Stank,,,,,It's tough to get a good sound with this much power....it's just crushing the input of my recorder 
I'm getting there....

[SILVERGUN]

One of the problems that I was having, was a poorly designed bias circuit....
I left myself a little short on available voltage and had to fix it before I could apply full input voltage...

Up until last night I was still only feeding it about 100VAC because I didn't have enough bias voltage at my disposal. I got it wrong the first time.
So I replaced the 10K bias pot (bad idea for this build), to a 25k pot and added a little resistance to ground (from 47K to 68K), and it gave me a much wider, usable range of adjustable voltage.

So I was able to apply full 120vac and that took the plates to 510VDC and the screens right to 500V (with the bias at 35mA), and played for a while.
The increased voltage brought out all of the growl in the EL34s and they held up for the limited amount of time that I was able to sit there and play.

I'm still thinking of putting a bucking xfmr in there, but I'll need a little more time with it to see how well different tubes respond.
And if you guys tell me those numbers are too high, then I'll listen.

I also still need to finish mounting the chassis and speakers in the cab and finish off a back panel with some labeling, warnings and instructions.

So there is still plenty to do....
I didn't mean to give the impression that it was finished....just that it is a working amp with no real major problems at this time.

[jazbo8]

So I was able to apply full 120vac and that took the plates to 510VDC and the screens right to 500V (with the bias at 35mA), and played for a while.
The increased voltage brought out all of the growl in the EL34s and they held up for the limited amount of time that I was able to sit there and play.

Whoa?! And the tubes survived with 510V plate and 500V screen into 3.6k? I assume you have some screen grid resistors... Is the Eg2 of 500V measured before or after the resistor? I'd like to plot the loadlines to see what's happening...

[SILVERGUN]

Hey jaz,,,welcome aboard....
I was just thinking about you because I forgot to mention your LED bias help...THANKS!

Whoa?! And the tubes survived with 510V plate and 500V screen into 3.6k? I assume you have some screen grid resistors... Is the Eg2 of 500V measured before or after the resistor? I'd like to plot the loadlines to see what's happening...

I tend to just throw round numbers out there to "ballpark" stuff so guys have an idea of where I am...I'll get a more accurate reading for you later, but those are pretty close.

I have 1K screen resistors and the 500V measurement I gave you was after the resistor,,, at idle

Thanks, as always, for your help and input!

I was also still considering putting in a dropping resistor in series with the choke, between the plate and screen nodes......?

[jazbo8]

Hey jaz,,,welcome aboard....
I was just thinking about you because I forgot to mention your LED bias help...THANKS!

I tend to just throw round numbers out there to "ballpark" stuff so guys have an idea of where I am...I'll get a more accurate reading for you later, but those are pretty close.

I have 1K screen resistors and the 500V measurement I gave you was after the resistor,,, at idle

Thanks, as always, for your help and input!

I was also still considering putting in a dropping resistor in series with the choke, between the plate and screen nodes......?

Yeah, really late to the game, I thought you guys were talking about baseball...   Glad to see the LED bias worked for you. I was just reading Aiken's post way back on AX84 on the Marshall 100W load lines, and noted that someone mentioned that there was a lot of sag from idle to full power, as much as 100V on the plate and 125V on the screen! If you used the Marshall irons, then I would expect similar amount of sag, but still the tubes are under great stress - by design! It would be interesting to take some accurate readings while you still have it open on the bench, we know the idle voltages, now try slamming it and see how low the plate and screen can go, to see how the power supply's doing under full load. But I must say I am very afraid that something may be blown, so be very careful - crank it up slowly, and make sure the tubes do not redplate - they are already under great stress (I think).

[SILVERGUN]

Yeah, really late to the game, I thought you guys were talking about baseball...   Glad to see the LED bias worked for you. I was just reading Aiken's post way back on AX84 on the Marshall 100W load lines, and noted that someone mentioned that there was a lot of sag from idle to full power, as much as 100V on the plate and 125V on the screen! If you used the Marshall irons, then I would expect similar amount of sag, but still the tubes are under great stress - by design! It would be interesting to take some accurate readings while you still have it open on the bench, we know the idle voltages, now try slamming it and see how low the plate and screen can go, to see how the power supply's doing under full load. But I must say I am very afraid that something may be blown, so be very careful - crank it up slowly, and make sure the tubes do not redplate - they are already under stress (I think).

Sounds good jaz...
It probably is time to give the speakers and my ears a rest and get some good old-fashioned scientific evidence going.
After 5 today I can get it plugged into a dummy load and give you some real time numbers.

Just for the record,,I used the 100 watt PT with a 50 watt'ish design (2-EL34), to purposefully avoid sag and leave plenty of power supply headroom.

Also for the record, while I had the input voltage down around 100VAC and had low 400s on the plates I went super hot with the bias (because I didn't leave myself enough -V in my initial design), and they held up @ 55mA each,, long enough for me confirm everything else was working OK

Other power supply accomodations include 2- 500uf / 500V (for 250uf / 1000V) first stage filter caps, followed by 2- 250uf / 500V (for 125uf / 1000V) screen node caps...

Sorry for the lack of schematic...I'm workin on it.

[Willabe]

I used the 100 watt PT with a 50 watt'ish design (2-EL34), to purposefully avoid sag and leave plenty of power supply headroom.

Other power supply accomodations include 2- 500uf / 500V (for 250uf / 1000V) first stage filter caps, followed by 2- 250uf / 500V (for 125uf / 1000V) screen node caps...

That's why you have 510dcv on the plates and 500dcv on the screens.

Only half the expected load on the PT and (way) oversized B+ filter caps at the 1st node (plate) and 2nd node (screen).


                    Brad   

[SILVERGUN]

That's why you have 510dcv on the plates and 500dcv on the screens.

Only half the expected load on the PT and (way) oversized B+ filter caps at the 1st node (plate) and 2nd node (screen).

Yup,,,no surprise. 
I was curious how it was gonna look under load,,,and I'm Ok with that,,for now
On the bench PS I was feeding the bridge 350VAC, and coming out in the high 490's......and there's no sag in my bench PS either

Part of the "metal" designs include very stiff power supplies and oversized caps...as well as stressed out power tubes at stupid-high voltages.

That's why I'm here....cause I've got you guys to bring me back into an acceptable range of stupid-high 
So far, my only guideline for a max rating is a glowing red bottle...which I haven't seen, YET

Once I post something,,,please don't keep the sound clips on my permanent record,,,,,it's just me doing an impression of me, if I were a metal-head 
Any true metal guitarist would call me a poser and toss my work in a pile with the Hansen twins.. 

I'm real curious to see jazbo's load lines....

[Willabe]

So far, my only guideline for a max rating is a glowing red bottle...which I haven't seen, YET

There's a little more to it then just red plating.

Speaking overall the higher the B+ plate (and screen) dcv the less current you can run through a tube.

But when you get up to the limits of a tubes B+dcv you can have ark over/internal shorts between the different elements inside the tube.

This can/will probably happen/be more risky with new production tubes as they don't seem to be as robust overall as opposed to tube golden years production.

The internal materials seem to have been stronger in the old tubes and were aliened better? They also seemed to stay in alignment better with hard use and rougher handling? Heat weakens metal.     

Not a guarantee you will have an internal short but I think the risk is greater.


              Brad                        

[SILVERGUN]

So far, my only guideline for a max rating is a glowing red bottle...which I haven't seen, YET

There's a little more to it then just red plating.

Speaking overall the higher the B+ plate (and screen) dcv the less current you can run through a tube.

But when you get up to the limits of a tubes B+dcv you can have ark over/internal shorts between the different elements inside the tube.

This can/will probably happen/be more risky with new production tubes as they don't seem to be as robust overall as opposed to tube golden years production.

The internal materials seem to have been stronger in the old tubes and were aliened better? They also seemed to stay in alignment better with hard use and rougher handling? Heat weakens metal.     

Not a guarantee you will have an internal short but I think the risk is greater.

I do get the power ramifications (higher voltage, less current)....it's the only part of this audio stuff that crosses over into my day job, so it's been a little easier to assimilate 
And with this design, less current is gonna be OK.. BUT, it comes with the adverse effect of raising the B+ voltage slightly

I'm skating just over the line of the published screen voltage spec of 500VDC......some types post 450VDC as max.


So, in this case,,,assuming I'm stuck with new production tubes into the future, I'll mark you down as a proponent of dropping B+ 

[jazbo8]

Be afraid, very afraid... Here are two charts for you to consider: left - load line at idle, right - load line assuming 100V sag on the plate and the screen grid voltages. As scrary as these charts look, they are actually very similar to the Marshall 100W load lines that Aiken did, may be that's part of the magic with these amps?! If you have an even stiffer supply than the Marshall, then the situation is even worse, I am not sure how long the EL34s can last under such condition.


Note the Po of 109W shown on the left chart is for the ideal condition, with zero supply sag at full output, clearly that it can not be achieved with the tubes (they will melt) or the OPT (it will be cooked). And the right chart shows if the supply sags, then the amplifier is essentially operating in pure Class B!

[SILVERGUN]

Thanks jaz,
I'm not sure that you picked up on the fact that I'm only running 2 - EL34 into that load...?
It looks like those curves are for 4 tubes at 109 watts output??

OK, I've read your post 10 times and stared at those charts and read some of what Aiken wrote.....

How are hundreds of thousands of JCM800s running perfectly fine for 30 years and not eating tubes like french fries?

[SILVERGUN]

OK jaz,
Here's some real world numbers for you...
I can't believe my eyes 
I dropped my supply voltage back to 110VAC just to cool things down a bit and wound up with 464V plates and 460V screens
I've got 1 meter hooked up to the OT CT and another meter hooked up to one side EL34 screen

I also dropped the idle bias current to 20mA just to help(?)...

I applied a 1K signal and pushed the Master volume to about 1/2 (probably about 70% of full), with an 8ohm dummy load on the 8 ohm tap
The plates dropped to 438V
The screens dropped to 422V

Here's the crazy part that coincides with what Aiken was talking about...
One side jumped to 106mA  and the other side jumped to 58mA
That's 44 watts dissipation on one side and 24 on the other!!

No red plating after 5 minutes   

I switched the tubes and the jump was evened out (a little better) to:
71mA on the side that was 106
55mA on the side that was 58

So it sounds like one of the tubes just takes the beating better     

And I had the mids scooped out (which includes most of that 1K signal).....when I brought that into the mix it was like a flame-thrower and I was seeing plate currents up near 150mA (for a split second, before I turned it right back down)

I'm gonna try a couple different loads and record those numbers, just to see what we can learn.

[SILVERGUN]

Changed to a 5ohm load and got:
96mA on the side that was 71 (we'll call it side A)
66mA on the side that was 55 (we'll call it side B)

Changed to a 24ohm load and got:
57mA on side A
37mA on side B
And with the 24 ohm load it took a lot more signal input to get the same sag result

I just needed to do that to visually confirm theory, and to catch up with the idea of needing to increase my primary impedance for this application...
Or just mismatch in the right direction, and mark the speaker out for the adjusted impedance....

Just to sleep at night knowing that I'm not melting any innocent ELs....
I am not concerned with max output,,,but I am concerned with max. reliability

During all of my testing I did not see red plating for 1 second.   

Thanks again for all of your help jaz!....thought provoking and steering me in a better direction!
 

[SILVERGUN]

So it turns out that I prefer the sound of an EL34 being pushed towards meltdown....
Guess I'm not the first.
 

I plugged a 16 ohm cab into the 8ohm tap and lots of that great crispy, crunchy, sizzling zip was gone....

So now what?....be "nicer" to the EL34s?

What was that Jim said about KT88s? 
If I switched to a bigger tube I'd have to change the OT to handle it.....ehhh 

Back to the bench...
I know what you're thinking...isn't this what the breadboard is for? 
Please don't say it...

I assumed that because there were millions of amps slowly destroying EL34s out there, that this was an OK idea........

[SILVERGUN]

So I went back out, and just acted like I didn't know anything about numbers, or loadlines, or jazbo, or dissipation....

And nothing traumatic happened...
No fuses blew, no tubes got red, no one died......
8 ohm speaker load into the 8 ohm tap with 110VAC input and 460 V plates
And even though I was monitoring over 100mA of cathode current while I was playing at approx. 40% output, it didn't stop me from getting some stuff recorded...

So I will edit that down and at least you'll get to hear how it sounds now before I chicken out and do something safe to delay the onset of the inevitable disaster.
 

[SILVERGUN]

Oh,,, and here's the preamp schematic....
I'm hoping there are no errors, and I will continue to look it over as I finish up Page 2

The amp's name is the AK47,,, as it was partially derived from it's humble beginnings as the bastard child of a once innocent Sovtek Mig 50,,,
it's ability to mow down anything in it's way,,,and part of a joke that I can't tell...

I apologize in advance for anyone who may be offended by the use of the name of a soviet military weapon,,,,,but please remember this is only the name of an amp, and the cold war has been over for 30 years.

I honestly don't mean any dis-respect to any military personnel, and I truly hope none is taken.

[PRR]

> That's 44 watts dissipation

No.

The rise in current from 20mA to 106mA goes along with pushing *power* into the *load*.

Much of the voltage and current in-to the tube passes through to the load.

How much? You need to measure the power OUT. You also want to monitor it, see if it is nearly maxed-out or clipping absurdly. (Which means you need a tone generator, not an axe.)

The 106/58mA suggests that one of the tubes (or driver) is sick, you are far past clipping (most amps do not clip symmetrically), or you are using an asymetric signal (which adds confusion).

Plate currents in a "50W" should be larger than ~~60mA. The Philips 1969 sheet shows 2*120mA for 55 Watts out at 425V supply (400V at anodes) and 3.4K load.
http://www.mif.pg.gda.pl/homepages/frank/sheets/010/e/EL34.pdf

Assume Philips knew something. 400V*(2*120mA) is 96 Watts IN-to the amplifier. They saw 55 Watts out of the amplifier. The difference, 41 Watts, is lost in the tubes, mostly in the plates. Two tubes, so at full power we have 20.5 Watts dissipation per plate.

The maximum dissipation is usually at part-power, often near half power. (This is why serious audiophiles objected to the FTC's 1/3rd-power test... it is nearly worst-case, will never be approached in "clean music".)

[SILVERGUN]

Thank you very much for keeping an eye on me PRR.
Your words are comforting at the least....I knew there had to be a sensible explanation and I knew I couldn't possibly be right. I was gonna have trouble sleeping tonight without your explanation.

Of everything that I have learned, this is obviously my weak spot.

The 106/58mA suggests that one of the tubes (or driver) is sick, you are far past clipping (most amps do not clip symmetrically), or you are using an asymetric signal (which adds confusion).

I think it's a combination of a sick tube,, dealing with a square wave...

This was my test pair, and when I swapped in a fresh set I saw more even results, even though I didn't record any.

Your supervision is priceless and gives me the confidence to move forward after being paralyzed by my own ignorance.

THANK YOU,,,AGAIN!