If you want to shop local and are willing to pay a bit for shipping, you can also checkout Ronnies Allbang and Strumit in Joburg, They seem to have a steady flow of old tube amps cruise through their shop - in fact they just
posted a bunch a week ago (I'll add the listing to the bottom of the post). Their facebook is at https://www.facebook.com/RonniesAllbangandStrumit/ if you want to look at pictures.
W.r.t. transformers etc. the mod by @Johnny-B is a fine one and quite nice since it is internal to the amp and nobody can accidentally plug it into the wrong thing in the future. It also doesn't mess with the amps own input circuitry so it is possible to undo the mod quite easily and sell the amp on in an almost "untouched" condition.
If you don't want to touch the amp at all you can look at something like this:
which will allow you to use the 110V amp by plugging into this little boksie, but beware forgetting about the boksie.
So the transformers (whether internal like @Johnny-B did, or external in a boksie) will sort out the 230V->110V conversion but it doesn't sort out the 50Hz->60Hz conversion that you will also need if you wanted to match USA power exactly. In my opinion that shouldn't really matter since the AC gets rectified first thing after it hits the input transformer on the amp, but at a slower switching frequency the internal DC on the amp will have ever so slightly more ripple. I don't think it will be audible but my ears aren't very golden so who am I to say.
If you really want to get around this, there are two ways I can think of - one is to bump the values on the capacitors after the rectifier to smooth out the extra ripple but that means you are digging around vintage amp internals which you might not want to do. The second is to buy a inverter that will generate clean 110V 60HZ AC from a battery which matches the US power exactly. I don't have a part handy, but I would just make sure it is a "true/pure sinewave" inverter if you do decide to go this way.
Ronnies listing below:
Ronnie’s ALL-TUBE January BLOW OUT !!!
In stock & ready to rock...
- FENDER Hot Rod Deluxe, Blonde Limited Edition:
Portable 2-channel 40 watt tube combo powerful enough to gig with. For those classy cleans combined with the saturated overdrive & distortion that Fender are famous for.
- Single 12" Jenson red label speaker.
- External speaker out.
- Pair of 6L6 power tubes and a pair of 12AX7s in the pre amp.
- Made in Mexico.
Price = R10,000.
- FENDER BASSMAN-100 Head & Cab :
A killer mid 70’s Silverface that’s just as great for guitar, Bass & even keyboards. Matching cab has two full range 15" Fender Special-design speakers inside. All original & Excellent working order.
PRICE = R8,000.
- VOX AC30-C2 | British Racing Green | Custom Limited :
With a quartet of EL84 power tubes this legend pumps out 30 watts of pure Class-A British power.
With a pair of 12” G12M Celestion Greenbacks, Normal & Top Boost Channels with Reverb & Tremolo, what a Beast !!!
Price = R12,500.
- H&K – STATESMAN QUAD EL84 :
This 2-channel 40W combo pumps out a range of tones through a 12″ Eminence RockDriver speaker. In spirit and in substance this is the kind of voicing people have been jamming to since the early ’60s.
- Clean + Twang and Overdrive + Boost channels.
- Spring reverb & Serial effects loop.
- Twang and Boost Mode, adjustable Reverb Balance.
- Four EL84 tubes & Two 12AX7 tubes.
Price = R8,000.
- WHARFDALE TCT35 :
A superbly underrated valve amp designed by Marshall’s Steve Grinrod, a real gem.
35W All-valve 1×12″ combo featuring 6L6 tube output which can handle tones from clean country to crunchy blues and more.
Price = R5000.
- H&K EDITION TUBE - 20th Anniversary :
Powered by a classic twin EL84-driven power amp, this dual channel, 20-watt all-tube combo delivers vintage cleans to dirty Rock tones & everything in between. Rockdriver Cream speaker, on-board spring reverb & effects loop.
Price = R4,500.
- IBANEZ IL15 :
A portable 15W Combo for Metal players. More than enough output for midsize venues and recording.
- Genuine Celestion speaker provides timeless tone.
- Separate EQs give you more control.
- Designed for down-tuned metal players.
Price = R4,000.
- ASHDOWN KLYSTRON C210n-500 :
575W Ashdown Klystron is a powerhouse Bass-combo with 2 x10″ speakers & horn. It features a single switchable input for passive and active instruments with a blend of solid state and dual triode tube preamp stages.
- Built-in dual band compressor.
- Onboard Subharmonic generator.
-Tube grind and EQ pre-shape.
- Custom developed Neodymium speakers.
Price = R9,000.