Discuss the stuff that makes your ears bleed.

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BY cholera
#751895
Im looking at a US amp which comes with a fairly decent (apparently) step down transformer. I generally use two amps together which is sometimes sweet and sometimes isnt....I just want to know if introducing a step down transformer into the mix is likely to cause even more hassles.

Anybody chime in on this?
BY godgrinder
#751896
If it's a good step down transformer then that's fine. Also you'd want plenty of spare wattage on the transformer. Say if it's a 100w amp then it's the best you get a 1000w transformer, although 500w would work too especially at home.

Also check if there's a 230V tap on the amp's power transformer (many do), if so you can just get a tech to do a simple rewire for you.
BY godgrinder
#751898
Is it that Rev G triple rec? My 1979 Mark II has voltage selector so there might be a chance the recto has a 230V tap.
User avatar
BY olegmcnoleg
#751904
If you need to pay for a rewind on a 100w amp, that's gonna cost you. 300-400 at a guess.

Otherwise, make sure the step down has a trip switch, not just a fuse. I used a step down for a couple of years on amps I brought from the USA...no drama. A pain to carry an extra transformer to gigs though, and I did used to worry about backup if it blew (which it didn't)
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BY robnobcorncob
#751909
olegmcnoleg wrote:If you need to pay for a rewind on a 100w amp, that's gonna cost you. 300-400 at a guess.

Otherwise, make sure the step down has a trip switch, not just a fuse. I used a step down for a couple of years on amps I brought from the USA...no drama. A pain to carry an extra transformer to gigs though, and I did used to worry about backup if it blew (which it didn't)


I used to gig a Mesa which ran on US Power. One particularly memorable gig involved the step down transformer blowing a fuse just before the first set and me having to play the rest of the gig through a solid state Laney bass amp. Later on in the 3rd set some Women decided to put their bags and coats down on the stage directly on top of my pedalboard at which point two patch cables gave up. At this point I was left with nothing but an average clean tone without a hint of breakup and a lead singer who made us play Enter Sandman as our final song (and on a borrowed EJ Strat no less...). Good times!
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BY jeremyb
#751910
robnobcorncob wrote:
olegmcnoleg wrote:If you need to pay for a rewind on a 100w amp, that's gonna cost you. 300-400 at a guess.

Otherwise, make sure the step down has a trip switch, not just a fuse. I used a step down for a couple of years on amps I brought from the USA...no drama. A pain to carry an extra transformer to gigs though, and I did used to worry about backup if it blew (which it didn't)


I used to gig a Mesa which ran on US Power. One particularly memorable gig involved the step down transformer blowing a fuse just before the first set and me having to play the rest of the gig through a solid state Laney bass amp. Later on in the 3rd set some Women decided to put their bags and coats down on the stage directly on top of my pedalboard at which point two patch cables gave up. At this point I was left with nothing but an average clean tone without a hint of breakup and a lead singer who made us play Enter Sandman as our final song (and on a borrowed EJ Strat no less...). Good times!


:lol:
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BY bender
#751920
olegmcnoleg wrote:If you need to pay for a rewind on a 100w amp, that's gonna cost you. 300-400 at a guess.



Clarry charged me a hell of a lot less than that for my Bandmaster PT rewind. That's only 40watts though.
BY tubeswell
#751924
Rewinding is a waste of money. The amount of iron in PTs made for US voltages is typically about 10-20% less than iron in PTs made for 230 mains voltage that are supposed to deliver the same secondary VA (purely because of production cost reasons). Rewinding is just putting more coils into the same size bobbin in the same iron. This means the iron has to induce more magnetising current than it was designed for, and the result is the PT will run hotter and tend to overheat.

Compare the two sine wave functions in the attached graph. The area under each function curve represents the total power that has to be induced through the core, and the 50Hz-230VAC sine wave has greater area. This means, all other things - like the secondary voltages etc- being equal, a 230V 50Hz PT needs to be bigger to stay cool.

Better to swap the US PT out for a 230 mains PT (if it doesn't already have a mains voltage selector).
Attachments
750px-50Hz60Hz.png
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BY olegmcnoleg
#751930
tubeswell wrote:Rewinding is a waste of money. The amount of iron in PTs made for US voltages is typically about 10-20% less than iron in PTs made for 230 mains voltage that are supposed to deliver the same secondary VA (purely because of production cost reasons). Rewinding is just putting more coils into the same size bobbin in the same iron. This means the iron has to induce more magnetising current than it was designed for, and the result is the PT will run hotter and tend to overheat.



yes, this is true. By rewind, I meant 'have the input transformer remade'. Ryan at The Amp Shop did mine (yes, it was a while ago), which included rebuilding the plates/iron and somehow fitting a bigger assembly back into the amp box. No mean feat on a small Boogie combo! Cost me about $250-300 per amp I seem to remember.
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BY cholera
#752800
Wow. Good info there. Thanks guys. Great story Rob!
The stepdown i got is only 500 watts and it doesnt appear to have a trip, only a fuse. Its a Raggie power co. Transformer. Im going to try it at jam tonight, my next question is this- i run two amps at jams through seperate 4x12s. Given the state of our jam room their is limited power and i usually run both amps and effects off the one 4 plug. Think its all good to keep doing this?
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BY cholera
#752802
By the way being the Triple Rec its a 150 watt amp. The guy i bought it off assures me he used this transformer at gigs for years though. Im just completely new to this so if there is any obvious newbie things to watch out for Id like to know them!
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BY cholera
#752815
I deliberately bought this one because i was keen to give an older two channel model a whirl. Ive owned a 3 channel, it was all good but nothing to write home about. Just going to get sucked into internet hype and try this one. Head and cab was 2k so it was a bit of a bargain i reckon. Cheers though man!