New power supply or voltage transformer?

[arsun]

I will be moving out of the US in a few months to some location with 220V AC voltage. I was not checking the news here in the forum for some time and I remember that there used to be no European power supply for the amp, however I wonder if that has changed and if it can be purchased for a swap (I am assuming there will be some guidelines for this case). The more technical question  is the following: If there isn't such a product, I will buy a voltage transformer for this purpose, something like this: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260366188202&ssPageName=STRK:MEWAX:IT
I wonder what the rating of the transformer should be for a safe operation with the SEX amp.

Thanks.

[Doc B.]

We can supply a 220/240V version of the power transformer used in the S.E.X. kit to replace the 120V one. Best bet is to contact Eileen at queen at bottlehead dot com or call 360-697-1936 and she can give you current pricing. I believe we just got a new shipment in, but I am not always on top of our inventory.

[arsun]

Thank you Doc for the reply. Do I need additional parts or changes in the amp, or is it a simple swap? I will send an email to Eileen right away.

[Grainger49]

The transformer Doc mentions will be perfect for the SEX amp.  The Bottlehead designed transformers will run on 50 Hz with a step down transformer, most will not, these are better designed.  But depending on what else your system consists of you could use something like the linked transformer to power everything except a turntable.  Most turntables have synchronous motors and would require both the transformer and a different pulley.

Exactly what is in your system?  You need to buy a 220/120V step down transformer that allows the whole system to run on 220V, 50Hz power.

[arsun]

Thank you Grainger for your comments. I am only taking my dac and sex amp with me along with my headphones. I cannot carry too many things. I think the dac must have a universal power supply, I need to check it though. A step down transformer will be an easier approach of course, but I am concerned about the quality of the transformer. Can anyone give some information about the requirements of such a transformer? Also, does 220V power supply require any other parts for installation or is it a simple swap?

Thanks again.

[Grainger49]

There are two differences between European power and ours.  The voltage is higher, the current is therefore lower, AND the frequency is 50 Hz rather than the 60 Hz we have here.

Transformers are most properly rated in VA, the product of volts times amps.  Sometimes rated in watts which is close to VA.  The transformers step down the voltage and don't change the frequency.  The lower frequency in Europe can cause more heat in your equipment's internal transformer.  The diodes and power supply caps don't mind the 50 Hz.  Therefore everything down stream will be happy too.

Getting just what you need in terms of VA will mean the transformer runs at the highest rated temperature as it is "Fully Loaded."  So a little extra will be nice.  Buying one that is 5 times more than you need will cause the output to be a higher voltage than you want.  But who would splurge like that?

Power transformers made by a reputable manufacturer will perform well.  Just be certain to get the 220V input plug and a 120V output plug.

[Paul Joppa]

For a step-down transformer, 100 VA or 100 watts is adequate for a SEX amp. I'd estimate that 500 watts is overkill. Anything in that range will work pretty well.

Actual voltages vary a lot - most coutries that us the higher voltage are gradually standardizing on 230v as the target, but +/-15% is not at all uncommon. It's usually on the high side, so we specify our higher-voltage transformers at 240v nominal. You should take your meter with you so you can check the voltage when you get there - specifically the voltage at the SEX amp input, which should be between 110 and 130v. Fortunately the 6DN7 tube is a TV design, pretty robust and unfussy.

Good luck, and post when you get there!

[arsun]

Thank you Paul for your input. I was thinking a transformer with around 250VA rating, so I guess I wasn't off that much . I got a price quote from Eileen for the PT-3 transformer, so I am considering getting one of them, however I haven't made up my mind yet. What I am curious about is the following: Are there any additional changes needed when I swap the 120V power transformer with the 240V PT-3 transformer?  

[arsun]

I am about to order some parts online, I will appreciate if anyone here can clarify for me whether the swap with 240V PT-3 transformer with the 120V one requires any other modification in the amp as well... Thank you.

[Paul Joppa]

I am about to order some parts online, I will appreciate if anyone here can clarify for me whether the swap with 240V PT-3 transformer with the 120V one requires any other modification in the amp as well... Thank you.

No other changes should be needed for correct circuit operation, but some countries have different safety requirements, such as switching both "hot" and "neutral" lines instead of just the "hot" line as in the US. I am not an expert on this subject even within the US, and even though I try to be vocal about the few safety things I am aware of. Do be cautious.