1Q22 Challenge Guitargeek62 amp makeover

guitargeek62

Well it’s been far too long since I got involved properly in one of these. I have a long list of unfinished (and unstarted!) projects, so let’s add one more to it!  

My challenge is pretty straightforwards, I’m going to build a mini-head cabinet to transplant my Marshall Reverb 12 chassis into. The stock combo comes with an internal 8” speaker which hampers the tone, plugging the same amp straight into my G12H creamback-loaded Zilla sounds superbly JCM800-esque and at very usable home volumes, so that’s the way this one will be left!

I’ll see what timbers I can get locally, as a solid cab with a stain/oil finish could be interesting, otherwise I’ll go for simple tolex ply construction in traditional Marshall fashion. 

My stretch goal will be to replace the faceplates with silver/brushed alu ones and turn it into a Jubilee-esque mini-head.

*edit* Current state:

downbytheriver

Nice one! Looking forward to seeing this one 

paulnb57

Watching with interest, I need to do something similar

guitargeek62

Here's my initial list of assumptions, materials and tools for the job - I'm open to suggestions as I'm sure there are other/better ways of doing it!

Assumptions:

• A head cab is theoretically less susceptible to vibration than a combo/speaker cab, so I could get away with reinforced box joints if I wanted to - particularly on a tolexed cab. However, I'll likely finger-joint it instead.
• Head cab will use ¾" thick materials.
• Dimensions and plans will follow that of the original combo, albeit reduced in height.

Materials:

• ¾" ply / walnut, oak, maple, or wenge (I can get the hardwoods easily enough from a local flooring company)
• Silver tolex + adhesive
• White piping
• Fixings
• Mesh grille (rear)
• Custom faceplates x2
• Corners x4
• Handle
• Feet x4
• Beers

Tools:

• Clamps
• MDF for templates
• Straight-edge
• Set-square
• Dovetail saw / dovetail jig
• Router (I only have a basic one these days, but it'll do the job... I think)
• Titebond

What've I missed?  

TTony

guitargeek62 said:

What've I missed? :mrgeen:

Beer for when the job’s done.

guitargeek62

TTony said:

guitargeek62 said:

What've I missed? :mrgeen:

Beer for when the job’s done.

Now corrected!

davros

3/4 inch radius router bit for the corners/edges
Heat gun can help for the tolex

guitargeek62

ICBM said:

[RE: Lead 12] A G10 Greenback sounds great in them - and it's a 16-ohm speaker, very unusually for a solid-state amp. (The Lead 12 was 8-ohm - I don't know why they changed it.) You can actually get a 12" in the cabinet if you're determined!

If you're interested in tweaking the amp part, fit the resistor (R4, 10K) which is missing from the preamp board near the input end - it adds a bit more bottom-end chunk. Why they wanted to take it away I don't know...

@ICBM - I found this again on a Lead 12 thread - do you know if the same applies to the Reverb 12 please? I wouldn't mind tweaking the circuit a smidge too if possible, largely to add a little more treble (perhaps a presence control, somehow?) when running it through a G12H creamback.

I'm also not sure what ohms the 8" speaker was in my 5205 combo, and probably should have checked that before plugging into my Zilla 1x12!  


I've started actually reading the NEETs course as well so that I can begin to understand something about electronics and try to work out what component does what to the signal path.

ICBM

guitargeek62 said:

@ICBM - I found this again on a Lead 12 thread - do you know if the same applies to the Reverb 12 please? I wouldn't mind tweaking the circuit a smidge too if possible, largely to add a little more treble (perhaps a presence control, somehow?) when running it through a G12H creamback.

R4 is missing on the Reverb 12, not the Lead 12. I haven't checked what would need to be done to add treble (no idea why you'd want to even with a dark speaker!) but it must be possible.

guitargeek62 said:

I'm also not sure what ohms the 8" speaker was in my 5205 combo, and probably should have checked that before plugging into my Zilla 1x12!

The 5205 is 16 ohm, I think even in the 8" version. If your Zilla is 8 ohm, be thankful that Marshall overbuilt the amp .

guitargeek62

Cheers @ICBM, and yes - the Zilla’s 8ohm, how stupid of me! I’ll look into ways to mod that too - I don’t think there’s any taps on the transformer, so I guess that’d need to change.

It doesn’t sound particularly dark btw, just needs a but more presence at lower volumes. When it’s cooking a little it sounds superb!