No Longer in development

GIJoe

Ok I have a valve special soon to be coming in the post and a G12H30 anniversary on it's way.

What I hope to end up with is a decent sounding amp that looks superb.

I plan to:

Add a tone + master volume (and maybe a few other mods.)

maybe replace the output transfomer (Hammond 125*** seems pretty common, and it would give me a 16 ohm output...)

Build it into a new enclosure and add the new speaker.

I quite like the look of Dr Z amps, so this, I hope, will end up looking like a Maz 18 Jr combo.

First question of the day is the cabinet - Pine or Ply?

Pine is a bit more resonant, and a lot cheaper (certainly compared to void free 'fancy' ply).

Ply is more expensive - (this depends - do I need really high end Baltic birch void free?).

I am going to tolex the cab so surface imperfections are not too critical - any suggestions? 

Just ordered the pine, £28!  A little pricey but I have used it before and it was £1/m less now!

Next question - I am going to rehouse the amp into a new chassis to fit the cab - steel or aluminium?

Ally would be easier to work with, but the local metalworkers recommend steel as it's easier to bend and cheaper.

Update #1

The pine is here - 2 x 2.4m 20mm * 275mm

I think I can scrape by and use the current chassis

The speaker arrived from @muddery

Just waiting in the actual amp now!

Update #2

All the parts have now arrived, I will post a photo soon, I have loads of tolex, enough to cover an additional head and cab!

I replaced the output transformer today with a Hammond 125ESE, massive 15 watter!

GIJoe

Reserved

GIJoe

Reserved

Dave_Mc

Does it need a new enclosure? I thought the epi cabinets for those amps were plywood (though I'm sure it's not the absolute highest quality ply at that price). Unless it doesn't take a 12" speaker in its own cabinet.

Plus red is awesome If it ends up looking like that Dr Z it'll be worth it

GIJoe

Dave_Mc said:

Does it need a new enclosure? I thought the epi cabinets for those amps were plywood (though I'm sure it's not the absolute highest quality ply at that price). Unless it doesn't take a 12" speaker in its own cabinet.

Plus red is awesome If it ends up looking like that Dr Z it'll be worth it

Maybe not.  A 12" would probably fit, but I don't fancy removing all the old tolex and sanding it!

Dave_Mc

Ah right yeah if it doesn't fit easily then that makes more sense. I'd most likely rather have a 12" speaker too in a one speaker combo.

Richardj

Ply is obviously strong, albeit a bit heavy.  Pine will however give a little extra warmth to the tone.  Why not get decent pine, or even a nicer wood like oak or cedar and make it into a more 'furniture' amp?

GIJoe

Richardj said:

Ply is obviously strong, albeit a bit heavy.  Pine will however give a little extra warmth to the tone.  Why not get decent pine, or even a nicer wood like oak or cedar and make it into a more 'furniture' amp?

Nice idea.  I think I want to learn how to tolex an amp along the way though

GIJoe

Next question - see original post.

GIJoe

Update #1!

GIJoe

HELP!

I just replaced the output transformer with a Hammond 125ESE - now there is a constant hum in the background.  Nothing is plugged in, and it does not increase with volume or gain adjustments - could this be a ground loop? @ICBM any ideas? 

goldtop

Probably... the newly installed output TX is picking up the electromagnetic radiation from the mains TX. If the same type/level of hum is also present with no valves in the amp, this is definitely the case.

You may be able to alter the orientation of the new output TX to lower this. Can't remember what one of those Epi chassis looks like.

In general, you should try to keep the axis through the centre of the coils at 90-degrees to each other (mains TX vs output TX). If you post before/after photos we may be able to suggest something.

GIJoe

@goldtop

Quite a big chassis, transformers mounted at right angles to each other.

Before:

PT on left, OT on right.

After: (photo slightly out of date - OT primary leads are now going through a second grommeted hole instead.)