Built my own amp during holidays

[phsyconoodler]

Hi Guys,
  Hope everyone had a great Christmas!
I finally got around to building my own amp during the holidays.It started off as an 18 watt Plexi circuit but I quickly decided 18 watts would not be enough so I changed the PI to a rel Plexi's and added a pair or 6L6's.I wanted use EL34's but the PT can't handle the filament current.(3A)
  I installed it into a princeton-sized chassis and a 1-12 combo cabinet.I used a Fender Bassman OT.I used parts I had on hand so it's a bit of a bastard.
   I also didn't have any good speakers except for this Eminence PA woofer on hand so I used it.Well,I was pleasantly surprised by the tone of this speaker!It has all the highs,mids and bottom end one could ask for.
  I played it at a couple of jams and it takes pedals extremely well.It sounds best with single coils because of the PA style speaker,but humbuckers with pedals sound killer good.
  I don't have a faceplate and may just leave it with 'dymo' tape letters.This amp is loud,has great tone and is more than enough for mid-large jams.
 I'll get some pics as soon as I can.
  Finally an amp for ME!

[panhead]

"Finally an amp for ME!"

Merry Christmas
 

[jjasilli]

Better keep it rough looking or someone's sure to insist on buying it!  

[phsyconoodler]

Yeah that's always been the issue in the past.This one stays with me!

 And of course you know I can't just leave it alone;I'm planning a trainwreck style extra gain stage for fun.
This one is cathode biased but I'm also going fixed bias.Just ran out of parts while she was going together!

[Platefire]

I enjoy that too and haven't done it in a long time. You sit around thinking doing a mental amp part inventory and realize you got enough spare parts to build an amp and just go for it. That's what I call adventure on the Great Amp High Seas. Pictures Please. We wanta see the little red headed freckel face step child !

[DummyLoad]

 

[phsyconoodler]

Yeah,yeah I know. Picture this: Oversized Princeton Reverb cabinet(taller) Marshall Green tolex,Wheat colored grille cloth.A 150watt PA speaker(which actually sounds great),input,volume,treble.mid,bass and master,2-12AX7's,2-6L6's,fixed bias with bias pot on the back panel.
  It is a modified plexi circuit,long tailed pair PI,with negative feedback.4.7uf bypass caps,.022uf coupling caps,100k plates,100k slope resistor,820/4.7uf on second triode cathode,470k inter-stage attenuation.
  Look at the 18watt plexi layout on the Brown-note site.It's that with plexi PI.
I'm adding more gain on V1 tonight and see what it sounds like.
  Pictures pending........

[DummyLoad]

Pictures pending........

awaiting pending...  :clock:   

[topbrent]

  It is a modified plexi circuit,long tailed pair PI,with negative feedback.4.7uf bypass caps,.022uf coupling caps,100k plates,100k slope resistor,820/4.7uf on second triode cathode,470k inter-stage attenuation.

  Look at the 18watt plexi layout on the Brown-note site.It's that with plexi PI.
I'm adding more gain on V1 tonight and see what it sounds like.
  Pictures pending........

Is this the 18watt "plexi" layout you were referring to?

Did you go with a plate fed tonestack as shown in the layout? 

http://www.brown-note.com/schematics/18WPlexi-Layout.jpg

[drumslinger2000]

dude...congrats on the build! 

[phsyconoodler]

Hey Topbrent,
   It's just like the layout except I made the PI the same as a plexi,and used a 47uf bypass cap on V1,pin 2.It fattened it up considerably from the 1uf that's on the layout.I punted the sag resistor,and used a 50/50 cap can(just because I had it).I also used 10k dropping resistors to get the voltages in line more with a plexi.
  I punted the plexi negative feedback I put in because it sounds best without it.It's fixed bias right now.I like it better than when it was cathode biased.It is the perfect clean/on the edge amp and it thrives on pedals like my modded BD 2 and a Marshall Bluesbreaker II.
  I tried a Jensen C12N,sucked bad,a old Alnico,not enough punch,a Mesa Clestion 90 watt speaker,lacked definition,and settled on an Eminence woofer(not sure what the hell it is) that has a great range.It's cone and spider move freely like a bass speaker but it only has a 2" voice coil.It sounds really good.
  The tone stack is very responsive,I really like it.However,I may add another tube and go closer to the real plexi layout with the cascaded extra gain or maybe add a trainwreck style gain stage.Maybe I'll leave it alone and be happy it works so well with pedals.
  This circuit would be killer good with a quad of EL84's I bet.

[phsyconoodler]

Ok,here are a couple of pics.I'll take the chassis out and show the insides later today.

[phsyconoodler]

Inside pics.Lots of room for mods! HeHeHe!

[phsyconoodler]

one more.

[DummyLoad]

niiice! 

:glasses9:

[Willabe]

Yeah, very nice. You guys are realy good at scratch builds. Realy nice work phsyconoodler.

Have one ?, whats that white plastic (?) rectangle shaped block, over by the OP tubes? A set of terminals? Just something you had layin around or do you use it often in scratch builds? Just wondering.       

         Thanks,      Brad 

[phsyconoodler]

That's a terminal strip I added when I decided I wanted to go fixed bias.I ran out of the old style terminal strips.No I would not use that in a customers amp,it's my own stuff and this one didn't cost me a dime.I used parts that were not being used I had laying around collecting dust.

[Platefire]

I'm a green freak and love the green tolex. So are you happy enough with the PA speaker that it will stay? I don't know how you set up the master volume but think it's a good idea---for trimming down the PP 6L6's for a smaller room. If you sell this one, We gonna string you up!   Platefire

[Tone Junkie]

Man i just love good amp porn    sounds like fun amp to play with.
Bill

[TIMBO]

I agree, the green looks the part and the aluminium faceplate also looks great. You said you used a woofer,do you know what its frequency range it is as i have a couple my self ( both rated at 50w) Keep up the good work

[phsyconoodler]

I played it last night at a jam and it was pretty damn good.The speaker is staying unless I find something better.Maybe a G12-65 might be better,I don't know.All I know is this one sure lacks nothing right now.
  I had the volume at 2 and was told to turn down,so it's plenty loud.
I like the master because with single coils you turn it all the way up and it stays fat and with humbuckers you turn the master down a bit so it takes away the boominess.
   I'll send a message to Eminence with the part # of the speaker and get some details on it.
I'm still adding a footswitchable gain stage to it so I can get my lead tone from the amp without pedals.Don't get me wrong,this amp LOVES pedals but I like the tone of the amp so much I want it all in the amp.It doesn't do the singing sustain like a D style amp but it has tone out the wazzoo. When I get some cash I'm swapping the PT for one that can handle EL34's because that's what I wanted top begin with.I like the bite from '34's.
  I did find out that it is best tilted towards the player or off the floor.It's such a small size that it can get pretty directional.Lifted off the floor it was pretty damn nice.I also didn't have to play anywhere near as loud to hear it.

[plexi50]

Nice build* Happy New Year!!!