One small step at a time OR my 18 watt Marshall build

ezietsman · 2011-04-06T21:41:41+00:00

So I've decided to build an amp. A twin channel 18 watt amp based loosely on the 1974x Marshall from the 60s. The first channel will be more or less the same as the original 18 watt's, just a volume and tone knob and very little gain from the preamp, all the drive will come from the two EL84s in the power section. The second channel will have Gain, Treble, Mid, Bass and Master Volume. This will be a higher gain channel with more preamp drive than the normal channel. Befiore you ask, the gain knob and pot will go into the lo input on the second channel, as I won't be needing that input ? Instead of having a power switch like all other amps (design flaw), mine will have a switched pot that switches it on and off (duh!) as well as control the loudness of the amp by varying voltages to the power amp and phase inverter. So I'll be able to get proper power section drive at any volume. To get things rolling, I present the first component of my amp, its also the only one I have at the moment. THE PLEXIGLASS FACEPLATE! more to follow...

ezietsman

Here's some more piccies!! yay!!

Isolated star ground point, made from ruler, two solder terminals and a piece of copper wire.

The MOSFET all gooped up, ready to be bolted to the chassis. The chassis acts as a heatsink, the goop is heatsink paste. The MOSFET is part of the VVR (Power scaling)

EL84 sockets completely wired

Phase inverter socket. A 12AX7 goes in here

Two preamp tubes' sockets. 2 more 12AX7s. The shielded input wires are not connected yet, my input jacks have not arrived yet.

Almost there... Just a few more wires to get connected and some careful checking then I can fire 'er up.

ezietsman

Getting close to the end now. Just need to pick up the input jacks from the Post Office when they arrive (prob here already), then the moment of truth. Here's some more piccies in the meantime.

Reason #497 why beer drinking is advantageous.

VVR. Yes, 3 resistors, one zener diode, a mosfet and a pot. Every valve amp should have this. Total cost of parts is probably R50.

Can capactor. Yes its old fashioned. But this is how 18 watts are built. Deal with it ?

Speaker jacks. 4, 8 and 16 Ohm.

ezietsman

And a little dress rehearsal.. HT5 on top for scale.

singemonkey

Keep the awesome rolling. It ain't an amp til it has hot bottles in it ?

Danny-B

This is just too awesome. Makes me want to do something similar...can't wait to see it completed!

ezietsman

So, I powered it up today. It DIDN'T explode! Yay!! What is more is that it works as advertised. One channel full of vintage rock and roll, The Rev Willy G would SO play this channel ?, the other channel a fire breathing monster, it hums a bit, will fix that asap. I managed to wire up the VVR control the wrong way so it is loudest on 0 and quiet on 10. Will fix it tomorrow. Just need that cab now...

The Monkey played it too, his thoughts may be more accurate since I'm obviously biased a bit here. It IS loud as balls, my ears hurt now (had to test it on 10 you see) and it is very touch sensitive, more than any other amp I've played, you can go from ZZ Top heavy drive to pristine cleans by adjusting the guitar's volume knob. Its great. No, Its AWESOME.

Finished chassis, yay!

Happy Valves ?

Jack-Flash-Jr

Can't wait to hear it! Think it'll be ready for a stage test run in R'bosch on thursday night? (if you wanna of course!)
ps. I would have left "0" as max vol. as in "dude, if it's this loud on 0 I don't wanna hear 10" ?

Hammeron

You a frikkin' genius!

Manfred-Klose

cool build, only went through the thread now.

I am going to do a similar project to this.
but i'm thinking more in the line of the marshall 20watt.

I'll have a look at your pre amp gain mod, thanks ?

are you going to run an AB switch into the amp ?

ezietsman

You may want to come and try this one first. The 18 watts are widely believed to sound better than the 20 watts in every way. What gain mod are you referring to?

Manfred-Klose

What gain mod are you referring to?

i read something on the 2nd or 3rd page about something you did on the second channel, cant remember what it was, i'll go back and have look.

thanks i'll make a turn sometime to come and try it out.
i'll bring my earplugs with

singemonkey

I have to have one. It's as simple as that. I have never played an amplifier that sounded better - at any volume - and was so sensitive to touch/volume control. I'd just decided to readvertise my SG. After playing it through that amp I'm wondering if that would be insane.

It has that classic late sixties sound. Not just a crude facsimile like I get out of my pedal, but true beanotone, sleepytime-time off cream live, or (especially with the SG) that Mick Taylor sound off Ya yas (even though that was an ampeg).

When I asked EZ to put that thing on max, fired up a note with vibrato and listened to it turn into perfectly controlled feedback... that was probably the best moment I've ever had with an electric guitar and an amplifier since a day, long before Hammeron was born, that I first played an amplified guitar at my buddy Gareth's place.

As EZ notes, there are issues with the higher gain channel. But you can hear it's doing what it's supposed to do. I wouldn't need that myself, but for most people who do any higher gain stuff it'd be a fantastic feature. Two amps in one kinda deal.

Anyway, as you may have figured, I was pretty smitten with it. Congrats EZ.

[deleted]

I can attest to the fact that it didn't explode and it really IS loud as balls, but we're talking golden syrupy, chocolate-salted Chef-style balls here...lol! I believe the volume knob goes all the way up to 11 too... ?

singemonkey wrote When I asked EZ to put that thing on max, fired up a note with vibrato and listened to it turn into perfectly controlled feedback... that was probably the best moment I've ever had with an electric guitar and an amplifier since a day, long before Hammeron was born, that I first played an amplified guitar at my buddy Gareth's place.

That was very, very cool... 8)

ezietsman

Here's the amp, in its housing, being 'tested' some more. HT5 is at the back (sans the HT5 bit), I'm using its speaker for now.

18 watts of awesome.

FenderBender

Awesome! Well done E.
It's gonna rock on those Marshall cabs at DLK Studios! Just make sure Manny doesn't swap out the chassis while you're not looking ?

Manfred-Klose

We tested the 18watt at my place today.

i am fairly impressed with the 18watt it cleans up nicely and can get pretty high if you want to.

thanks for ewald,singe,cowbell and greame, for a unplanned jam, was fun.

FenderBender

Yo the EZ18 kicks ass on that Slash 4x12! At one stage I thought the roof was going to come down ?

Well done EZ, you did a sterling job. Try rolling/changing tubes to see if you can drop the hiss on the superlite channel (IIRC).
Was great seeing you and MCB again.

Singe, it was great to meet you!

Manny, shot for your time and space. That Yamaha of yours was hard to put down...

singemonkey

Very cool meeting you guys. I've yet to meet a gfsa'er I didn't like. ?

Amp sounded very different through that 4x12. Way too loud for a start ?

ezietsman

Thank you Manfred for letting us let rip. I think that was the loudest I've ever played any amp, and I don't think I'll repeat it without plugs soon. My ears are still hurting. I'm not sure the 4x12s are the best cabs for this amp, its not strong enough to make the speakers drive so it sounds a lot cleaner than it does through my HT5's G10N-40, they're also a bit bright for my liking. I'm keen to hear the amp through the G12H30s in the cab that should be coming my way soon.

singemonkey wrote Very cool meeting you guys. I've yet to meet a gfsa'er I didn't like. ?

Amp sounded very different through that 4x12. Way too loud for a start ?

WAY too loud. Damn, I knew the amp was loud but that surprised me a bit. No gig today will need that amount of volume, I don't think most drummers can hit the drums hard enough to keep up with that ?

I'll try and record some clips when I have my cab, I know someone with a SM57 ?

Jack-Flash-Jr

Quit amp teasing me. I demand a listen!

« Previous Page Next Page »