Marshall 20w build

[M Fowler]

I had this Ceriatone 20w faceplate sittting around for 2 years along with all the parts in stock so I decided to put this sweet little bugger together.

Nice harmonics in an 18-20w Marshall.

Turretboards.com blank chassis/PT 290-0-290 and MC 18w Marshall OT 8K. Followed the Ceriatone layout and 2061 schematic. Changed up the board to a more logical layout to me at least.

Mark

[Colossal]

Really nice work Mark! Bet it sounds great!

[Decko]

JA Mod?

Just kidding!

Awesome....Looks great!

Danny

[M Fowler]

Thanks guys this was a fun project.

JA mods

Can you spot the JA mods

Hey I forgot to install my EL84 wire tube retainers, I better do that.

I am going to use this same PT/OT pair for an upcoming K19 build.

[Randy Magee]

Great looking build Mark! How does the 20 watt sound as compared to an 18 watt? A little faster amp I assume since it has a SS rectifier...

[M Fowler]

Thanks Randy, the thing is yes there is the SS verses tube rectifier thing going on but also this is a Bass amp so the circuit is different. Take the 330uf bypass cap on V1 and the differences in the PI circuit as well.

I like the lower bass of this amp but still has the harmonic quality about it. The caps and other components are still settling in so it will be a while before I can see all the differences. I still like my 18w tremolo version as well.

Mark

[breakfastbuddy]

looks like R 15 must be wrong value , should be 820R ?

[M Fowler]

looks like R 15 must be wrong value , should be 820R ?

That is a 8k2 they wrote it 8.2k hard to see.

A regular Marshall 18w PI circuit is quite different from the 2061 bass.

Mark

[statorvane]

The available schematics indicate this amp was derived from a PA amp. The 8.2K resistor (R15) is shown here: http://www.drtube.com/schematics/marshall/2019.gif. Same for the 2022, 2017 amplifiers, and I believe also for the 2061.

[johan]

from a tgp thread.
i did this and liked it

"Something simple that makes a surprising difference to making it sound more like a mini Plexi is to split the cathode bias network for the power tubes. Instead of a single resistor and cap, use one per tube (double the value of resistor and cap). This doesn't make it fixed-bias, but it does make it behave more like it tonally, since now each tube's current does not affect the bias point of the other, as is true for fixed-bias."

[joCCe]

Nice build you have there!

Is that 18 awg wire on the board and pots?

Joakim

[M Fowler]

Joakim,

Thanks the wire is 20 gauge pre-tinned stranded PVC mostly topcoat. Some 20ga solid on the input jacks.

Filament wires are also 20ga. same wire stock.

Mark

[joCCe]

Joakim,

Thanks the wire is 20 gauge pre-tinned stranded PVC mostly topcoat. Some 20ga solid on the input jacks.

Filament wires are also 20ga. same wire stock.

Mark

Thanks for the info, Mark

Joakim

[Tone Junkie1]

Nice looking build Mark you always seem to have something cool in the amp stand.
Bill

[M Fowler]

Thanks Bill,

I collect parts, whether chassis, cabs, transformers or faceplates.

This one started off as a faceplate I got from a guy on the Metroamp Forum about 2 years ago. Every once in a while I would look at it and say I need to build that 20w amp.

Mark