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Is a 500w step down transformer enough for a Mesa 2:100?

Cron

Inspired
Hi.

I just got a Mesa 2:100 (us voltage) and with it came a step down transformer for Australian voltage rated at 500w.

It does work but the guy i bought it from used the two together but never really gigged or played loud volumes for long periods of time. Will the 500w step down transformer be sufficient for running the Mesa 2:100 at gigs etc?

If it makes any difference i will only be using channel A of the mesa (other channel: gain down, presence all the way up with no load connected..... the manual says to run it this way if only using one side into one cab)

I did get a US furman power conditioner that is running between the Mesa and the step down transformer FWIW and it says the voltage is 124v when playing through the amp (back of amp is marked 120v )

If i do need to get a new one i'd appreciate some advice on how to choose it and what specs and ratings to look for.

Thanks
 

paulmapp8306

Fractal Fanatic
Re: Is a 500w step down transformer enough for a Mesa 2:100

You need wo work out what the 2:100 uses wattage wise. Not what it puts out, but what it actually uses iteslef.

That would ve Volts draw x Amps draw - so while you know the Volts is 120, you need to know what amps its drawing. Anything up to 4 Amps (4x120 = 480 Watts draw)and your fine - more than that and the transformer may run into problems. It probably wont matter too much if your using one or two channels of athe amp.
 

Cron

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

How do i figure out how many amps the mesa draws? Ive got a multimeter and im not afraid to use it..... well maybe a little.

So would the amps go up as i turn the Mesa up? Or would it be a static value?
 

gittarzann

Power User
Re: Is a 500w step down transformer enough for a Mesa 2:100

There should be a value in the specs how much current it draws.

I think it is fused at 6 amps.
 

Cron

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

ok manual says total power consumption is rated 6amps @ 120V. According to paulmapp's calculation 6 x 120 = 720w

So ill need a 1000w step down transformer to be safe?

Just curious: what are the risks if using the 500w one? And if the guy did run it with that 500w transformer should i be worried about the amp being damaged?
 

Cron

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

Bump, id really like to know if a 500w step down transformer would be OK if i dont use the 2nd channel on the amp and the gain is always on 0 on that channel. Getting the 1000w one means i need a bigger rack too so im really hoping i can stick with the 500w one i have.

A Triple Rectifier is fused at 4amps and a 500w transformer is sufficient to run one of those. I spoke to a someone who told me the 6amp rating for the 2:100 would be at full volume, both channels, with a test tone through it... not even a guitar signal. That true?

Anyone?
 

Dpoirier

Power User
Re: Is a 500w step down transformer enough for a Mesa 2:100

Can't really help with your direct question, but have you considered the much simpler approach of reading the label on the back of the amp where it states the maximum power consumption? I have frequently made super complex consumption calculations with other equipment to figure out my UPS needs, and ended up with fairly large numbers, then had a "doh!" moment, and simply added up the "max power" ratings from the back of the gear, and ended up with a more reasonable running total. To date, all my UPS setups have been meeting the needs.

So even if the your calculation of volts (known) times watts (assumed) is leading you to some fuzzy conclusion, I'm sure the "max power" label will give you an absolute maximum which is probably lower than your assumptions. Maybe this will provide you with a simple answer? And if that max power is slightly higher than the 500W you have at your disposal, remember it's a *max* power, and you said yourself you won't use the second channel.
 

Dpoirier

Power User
Re: Is a 500w step down transformer enough for a Mesa 2:100

Ok, one more suggestion: get yourself one of these:
http://www.newegg.ca/Product/Product.as ... 6882715001
... they are well worth the low investment for other purposes, buy in your case, plug your amp into it, crank it up (more than you ever will when you plug into the step-down transformer) and read the actual power consumption.
 

paulmapp8306

Fractal Fanatic
Re: Is a 500w step down transformer enough for a Mesa 2:100

I dont know the messa. Does it have on/off for both channels?

WhatI mean is my VHT 2:50:2 has one on/off switch - and standbys for both channels. In this case the amp uses pretty much the same power whether I use one or two channels. Most of the power is for the transformers, heaters, fans etc - not actually amping the signal. These are using power regardless of if you use one or two channels. Also the "vol" or gain" shouldnt make a difference either. Power amps tend to be at full power all the time - with the vol/ gain adjusting the input sensativity (so reducing the input signal, but still amping it by the same ammount).

A Marshall 9100 on the other hand has on/off and standby switches for each side. In this case you can half the powser consumption by using on channel.

Also, If the amp is fused at 6 Amps, the normal current draw will be less than that.

Can you try the kit first? You shouldnt damage the amp by supplying it will too little power - it just wont work.

FWIW, Ive just checked my VHT (50 watts per side). From the manual For US, 120V 4 Amps (= 480 Watts). for EU, 240 V, 2.5 Amps (= 600 Watts), for Japan 100v, 5 Amps (= 500W). thats the fuse rating. Actual draw (using a multimeter in line in work) - which was the same with one or both channels running, on any gain level - was 400 Watts (give or take a few). I susspect if the Messa is 6a, its going to use around the 600 Watt mark, though thats a guess.
 

gittarzann

Power User
Re: Is a 500w step down transformer enough for a Mesa 2:100

Why not email Mesa and ask them what is recommended ?
 

Cron

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

paulmapp8306 said:
I dont know the messa. Does it have on/off for both channels?

WhatI mean is my VHT 2:50:2 has one on/off switch - and standbys for both channels. In this case the amp uses pretty much the same power whether I use one or two channels. Most of the power is for the transformers, heaters, fans etc - not actually amping the signal. These are using power regardless of if you use one or two channels. Also the "vol" or gain" shouldnt make a difference either. Power amps tend to be at full power all the time - with the vol/ gain adjusting the input sensativity (so reducing the input signal, but still amping it by the same ammount).

A Marshall 9100 on the other hand has on/off and standby switches for each side. In this case you can half the powser consumption by using on channel.

Also, If the amp is fused at 6 Amps, the normal current draw will be less than that.

Can you try the kit first? You shouldnt damage the amp by supplying it will too little power - it just wont work.

FWIW, Ive just checked my VHT (50 watts per side). From the manual For US, 120V 4 Amps (= 480 Watts). for EU, 240 V, 2.5 Amps (= 600 Watts), for Japan 100v, 5 Amps (= 500W). thats the fuse rating. Actual draw (using a multimeter in line in work) - which was the same with one or both channels running, on any gain level - was 400 Watts (give or take a few). I susspect if the Messa is 6a, its going to use around the 600 Watt mark, though thats a guess.

Thanks man! Thats really helpful to know that an amp would draw the same amount of power with 1 or 2 channels pushing a cab or not......might be common sense to some but i was wondering about this.

I also read that the VA rating (120v x 6amps) is usually not exactly the same as the wattage. People think they are the same thing but ive read on 3 different websites that the actual wattage will be less than the VA rating, often as low as 70%. So if the required VA rating is 720 then 70% of that would be 504w...... ( i know im cutting it fine). So that explains why the 500w step down is working Ok.

I did a gig with it tonight.... was hesitant but couldnt get the right step down in time and it worked pretty well. It was a really short set though, and I dont blast away everyone with my stage volume.

The cheap looking chinese transformer was actually giving a spot on reading of 120v (the furman i use between the transformer and the amp has voltage indicator lights). And it wasnt really heating up more than I expected.

As for contacting Mesa, Ive sent them an email about something else and still waiting for a reply. I did speak to the tech at the local Mesa distributor and he said that on peaks in the signal (palm mutes etc) strange stuff might happen if the step down wasnt powerful enough.... when i told him i want to get a 1000w one his reaction was "whoa that would be huge and expensive".... he was actually one of the only techs that didn't say "get a 1000w" from the get go..... 2 others did though.
 

srooijens

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

Cron said:
I also read that the VA rating (120v x 6amps) is usually not exactly the same as the wattage. People think they are the same thing but ive read on 3 different websites that the actual wattage will be less than the VA rating, often as low as 70%. So if the required VA rating is 720 then 70% of that would be 504w...... ( i know im cutting it fine). So that explains why the 500w step down is working Ok.

Actually for the proper size of the step down transformer you would need the (higher) VA rating not the (lower) power consumption.

S.R.
 

Cron

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

Yes well some companies rate their step downs in VA some rate them in Watts.
 

gittarzann

Power User
Re: Is a 500w step down transformer enough for a Mesa 2:100

I don't know why you don't shoot a quick email to Mesa and ask them what they recommend....you are asking something that I am positive they has come up against before.
 

srooijens

Inspired
Re: Is a 500w step down transformer enough for a Mesa 2:100

Cron said:
Yes well some companies rate their step downs in VA some rate them in Watts.

The ones that rate them in watts assume a power factor of one (unless clearly stated otherwise) so actually they're also rated in VA.

S.R.
 

paulmapp8306

Fractal Fanatic
Re: Is a 500w step down transformer enough for a Mesa 2:100

Yep. Pure physics says watts = volts x amps. No getting away from it - its completely accurate.

However, as always real life isnt perfect. There are losses in the system. That means that the volts x amps (va) rating is what you NEED. The Power the amp uses may be less than that - BUT you have to figure in the losses.

However, in this case we dont actually know what the amp draw of the messa is - were justy guessing using the fuse rating and my measurements of a VHT 2:50:2. So while in the ballpark its not going to be accurate. If the 500W transformer worked, then its fine.
 
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