Eddie in a way...told us what he did

[Roe]

I've seen 230+v into the 120v of a 100jh, resulting in 1200v over the stdby switch, 1100v plate voltage and a blown kt66

No: I didn't do this

[julkke]

Feed 120v on the 220v tap and watch the pt primary melt...

........

So guys, don't feed 120v to 220v tap, please!

??????? This is not a problem. 220 into the 120 is very bad, but 120v into a 220v amp is fine. You might not get any sound, but it looks like at least Lodewijk and Evh have gotten sound with voltages this low.

Yes it is. Here are some thoughts of kinda the same thing by Larry: http://forum.metroamp.com/viewtopic.php?f=22&t=13605" onclick="window.open(this.href);return false;

[vh junkie]

The scenario Larry is discussing here is a case where you have (2) 120v primaries side by side:
The 0-120 side has heavier wire and is used for 120v operation.
The 120-240 side(still 120v) has thinner wire and is used for 240v operation by putting it in series with the 0-120v side.

The other posters are suggesting connecting 120v to the 120-240 side (instead of the 0-120 side) to achieve a modest secondary voltage drop because of the added voltage drop on the thinner wire of the 120-240 side.

Larry is saying not to do this because the 120-240 has thinner wire and will over heat.

This has nothing to do with running a 240v wired amp at 120v.

[julkke]

Maybe I havent got it right.. Isn't the 220/240v wire still too thin when feeding 240-0 with 120v? Forget all my posts if I'm wrong here.

[Strat78]

Maybe I havent got it right.. Isn't the 220/240v wire still too thin when feeding 240-0 with 120v? Forget all my posts if I'm wrong here.

I think you are keeping it interesting Julkke, thanks for that, it's good to see that this thread has been taken a little deeper.

[ampSnob]

Maybe I havent got it right.. Isn't the 220/240v wire still too thin when feeding 240-0 with 120v? Forget all my posts if I'm wrong here.

Yeah, they are talking about something pretty different and specific in that thread. VH Junkie pretty much nails it with his description. It's a power transformer hack. Interesting, and worth discussing, but not completely relevant to this thread. Larry's concerns that the wire is to thin and might burn up are completely true, but only in the case of the hack as specified. Having said that, I've read a few threads of people doing this same thing including knowledgable people like Kevin O'Conner. Pushing the PT past its operating limits might be beneficial for tones sake, but from an engineering point of view, it is a bad idea. Enough t2562 have already burnt up without any help so definitely don't do it with an original vintage transformer.

Back to the original topic. The 120v winding does in fact have twice the current running through it than the 220v, therefore it uses thicker wire which is a lower gauge wire. (18awg is thicker than 22awg for example)

The current the transformer draws (off the primary) is determined by how many turns of primary wire there are and the input voltage (and of course the load on the transformer which is sort of a constant in this scenario so we don't have to think about it)
By using more turns of the primary, like using the 220v tap, less current is allowed to go through in every scenario. So the 220v tap will allow less current than the 120v no matter what voltage you put into it. Therefore it can handle 120v just fine with limited sound, or 220 like it's expecting.

So the answer the question, it would be too thin, but it's not used that way. Unless you do the hack like they are talking about.

Thanks for the link, that was a good read

[julkke]

Well thanks for clearing that up. I apologize for giving wrong advice, although it's good from the learning point of view that this was cleared up.

[vanhalen5150]

This discussion sounds similar to the 50w I built using a Classic Tone PT. Both the 120 and 240 had to be wired to the selector switch or you'd overheat the PT.

I agree with YMI5150 about the sound above, its missing bottom end and has a low voltage generated sound like FETSs. Perhaps mic placement or 2 mics would rememdy that?

Don't forget a lot of wall voltage in the 70's was less than 115v.

[Tone Slinger]

1976-1978 era Ed-Tone is basically a stock 100 watt Marshall superlead running on approximately 90v via a variac stepping the USA 120v down. Good 4/12 with some 25 watt celestions and a GOOD sounding strat w/hb'er and a GOOD sounding Explorer clone (Destroyer). Throw in a MXR Phase 90 and a echoplex and your there.
You can approximate his gain and compression at lower volume levels with either a attenuator or ppimv.

So yes, Ed DID tell us what he did.

[Sparky4444]

1976-1978 era Ed-Tone is basically a stock 100 watt Marshall superlead running on approximately 90v via a variac stepping the USA 120v down. Good 4/12 with some 25 watt celestions and a GOOD sounding strat w/hb'er and a GOOD sounding Explorer clone (Destroyer). Throw in a MXR Phase 90 and a echoplex and your there.
You can approximate his gain and compression at lower volume levels with either a attenuator or ppimv.

So yes, Ed DID tell us what he did.

...and some good ears behind the console to make it sound big on tape -- engineering know-how expertise!

[rgalpin]

in the rwtd clip, when it switches to ed's iso, i think you hear a good example of what some refer to as a chalkiness in the vh I tone. by contrast ludjwigck's clip is lacking that chalk but seems to have the right brassy break up and other qualities that backup what he is saying about the setup used in the clip.

i got alittle confused as the discussion went to projecting the technique to a 120v amp variaced to 90-ish.

is the setup used in the rwtd clip a 220 variced to 140?