Finished my EL34 Beast Champ

[theundeadelvis]

I finally finished my Beast Champ build. Cabinet took forever (because I'm not at all a woodworker), but it I'm happy with how it turned out. Great sound too! Tons of rock tone (maybe too much, I may try a different preamp tube). Fun simple build. I call it Scraps, because it was built completely with spare parts and scrap wood. Another build that was successful thanks to help from this awesome forum!

[dwp]

Nice handle!!!!

Build looks great too, just original enough....Am soon to embark on my own woodwork endevour, got the tools, and not the experience. Yours gives me some ideas, thanks for sharing

[plexi50]

Real nice! Is this PP or SE?

[loogie]

Clips.

[theundeadelvis]

dwp - The handle is my favorite part to. I have no woodworking experience really, but from what I've done, patience is key. Every time I'd get in a rush, I'd screw something up.

plexi50 - it's single-ended (love that touch sensitivity).

loogie - I got rid of all my recording gear unfortunately. I may shoot a video, but the sound won't be stellar from through camera mic.

Thanks for the compliments.

[tubenit]

Very nice looking build! I like the woodworking.

With respect, Tubenit

[Fresh_Start]

The woodworking looks fine - especially for someone who claims no expertise!  Love the handle.

Would you mind posting voltages for the power tube plate, screen grid and cathode?

Also, what's the primary impedance for your OT?

I'm just about finished with drawings for a single-ended EL-34 amp & would appreciate the info.

Cheers,

Chip

[dwp]

hey how's the metal grille on the speaker cab? that is metal, yes? you tried with and without? get some dampering action? how did you control the buzz?
(spill).....lol

[theundeadelvis]

Tubenit - Thanks!

Fresh_Start - the next time I pull it apart, I'll try to remember to get you some voltages (they may be posted over at sewatt.com). Here's the layout I used:


dwp - I didn't notice any damping by the metal grill, but I also don't have the best ear for those things. What I've done in the past with cane grills (and will do for this amp) to control the buzz is cut small pieces of rubbery kitchen cabinet shelving padding, and strategically glued it in the areas where the grill vibrates enough to buzz.

[phsyconoodler]

Nice Beast bud!

  Thge writing on your layout looks like you wrote for old horror flics!

[bigdaddy]

Great looking amp!!!!

[John]

That is so cool!

[phsyconoodler]

I think they should put the layout on schematic heaven   34F2A
  
  I love simple amps that throw out gobs of attitude.

  With a handle like 'theundeadelvis' i want to see your picture 

[nastyoldtech]

Man that looks sharp, I bet it sounds as good as it looks. Good job! Is it me or does it look a little like this little guy here?   :happy11:

[birt]

great looking amp!

[theundeadelvis]

Thanks everyone!

psychonoodler - I actually didn't do the layout. I can only wish my hand writing was horror movie cool (or legible for that matter).

[jojokeo]

Ditto on looking good & handle - it really caught my eye. Is the speaker a 12", what kind, and open or closed back?
*Something to consider - if it's got too much "rock" or gain, you could add feedback simply enough w/ a switch on the back that may be easier than switching tubes (to keep from having to open things up) when gigging different places or situations.

[theundeadelvis]

jojokeo - thanks for the kind words. It's an open back cab with a 10" WGS Veteran. Sounds pretty good. I like your idea about adding the negative feedback. I may have to look into how to implement that.

[jojokeo]

Two resistors and a switch - really simple. Check the Champ/Vibro Champ original circuit/layout and there's many other amps you can check out also. You can play w/ the amount of feedback to suit your tastes by changing the resistor/divider you create. Think of the ratio range being anywhere from around 20:1 upto 50:1 - the lower the ratio the more the effect that's created, ie - lower output and lower gain being a cleaner and more linear sound.

[nastyoldtech]

Or even wire up that NF on a pot for everything in between? Cool mod. I call it my country western/rock n roll mod. Turn it one way and it's a little bit country, and the other way it's a little bit rock n roll!

[jojokeo]

Or even wire up that NF on a pot for everything in between? Cool mod. I call it my country western/rock n roll mod. Turn it one way and it's a little bit country, and the other way it's a little bit rock n roll!

Great idea, you could also use a push pull pot for removing it out of circuit to keep it fully original or a high value pot could acheive a close approximation but the range sensitivity may not be too good? Sounds like fun testing/experimenting time.

[theundeadelvis]

So, if I'm right (which I very well may not be), I would insert a switch, wire, and resistor from the speaker jack to pin 8 of the preamp tube (or the turret on the board where pin 8 is connected)? Is this correct? Thanks again guys!

[Fresh_Start]

Although the NFB ties directly to the cathode of the second triode in the 5F2-A, your second triode has a cathode bypass cap.  Take a look at the Vibro Champ.  There's a relatively small resistor between the cathode's resistor/cap combination and ground.  The NFB is tied to the junction of that resistor and the resistor/cap combo you already have.  I think this is because the "top" of the cathode bypass cap is at AC ground (IOW AC just passes through it), so you need a resistor between that point and ground to create a voltage divider.

There's a pretty big difference in the amount of NFB between the Tweed (5F2-A) and the Blackface (AA764) circuits.  Tweed is 22K/1,500 producing 6.4% NFB (it's a voltage divider).  BF is 2,700/47 producing only 1.7% NFB.  (That's roughly 14:1 vs. 57:1 the way jjk thinks about it.)  The Blackface cabinet was 10% bigger in volume (14 x 17 x 7-1/2) vs. Tweed (13 x 14-1/2 x 8-7/8).  I'm guessing that the speaker and output transformer were better as well, requiring less NFB to tame the beast

A pot might help you dial in the value(s) you want, but a switch between two resistors or on/off is easier and finding a 1k or 2.5K pot might be a hassle.

Hope this helps,

Chip

[rzenc]

finding a 1k or 2.5K pot might be a hassle.

Pick 1M lin pot - standard part - solder 1K, 2K5...whatever you like, to the outer lugs. this will place overall resistance to be slightly less than your resistor due to parallel resistors arrengment.


Rq=[(R₁*R₂)/(R₁+R₂)]

Hope this helps,
With Respect,
Best Regards.

Rzenc

[Shrapnel]

Rq=[(R₁*R₂)/(R₁+R₂)]

LOL... not trying to be confusing here, but... it's interesting that there are two forms (formulas) to the same problem, with only two resistors.

The one you gave, which only handles two resistors in parallel: R_q=[(R₁*R₂)/(R₁+R₂]

AND the the one that will handle up to an absurd number of resistors in parallel: R_q=  1/[(1/(R₁)+(1/R₂)  ... +(1/R_n))]

Either one works for just two resistors though, so go for whichever formula/algorithm you are most familiar with.

[aryasridhar]

Tubenit - Thanks!

Fresh_Start - the next time I pull it apart, I'll try to remember to get you some voltages (they may be posted over at sewatt.com). Here's the layout I used:


dwp - I didn't notice any damping by the metal grill, but I also don't have the best ear for those things. What I've done in the past with cane grills (and will do for this amp) to control the buzz is cut small pieces of rubbery kitchen cabinet shelving padding, and strategically glued it in the areas where the grill vibrates enough to buzz.

Great Amp, Looks really nice.....Great Job on this one.....I am also planning to build a tube amp and the layout that you provided is of great help, would you be able to tell me what kind of transformer you used and what are the connection types?

If you have one, I would like to get the parts list, even though they are in the layout......If possible.

Thanks in Advance

[theundeadelvis]

aryasridhar - I don't have a parts list, because I built the amp from leftover parts I had. I know the power transformer was from Musical Power Supplies (decent and cheap!), and the output transformer is a Hammond 125ESE. If there's anything else I can help you with, let me know! It sounds awesome!