[paba]

Hi all,
my local surplus store has some Dale Tech 3.5 Amp medical isolation transformer units in a nice alu enclosure for what I believe to be cheap $50.
Any use for us audio folks as the start of a AC conditioner project. I have not looked inside yet (I have to buy one for that).
Leakage current <50uA and 5% load regulation, (VA) 385 Max.

Perhaps adding those X2 caps "a la Auricap" and could be something or should I buy two of them and wire them for balanced or perhaps wire two in parallel to double the specs?

Unless you guys tell me this not worth it or 50$ is a rip off.

any comments or advice is welcome
paba

[hmen]

The first thing i would do is ask the people selling them if you could plug one in to see how much noise it makes. Sometimes isolation transformers that aren't made for audio work well electronically but can produce pretty loud humming noise.

[BradJudy]

I'm guessing it's these boxes:

http://cgi.ebay.com/NEW-MEDICAL-GRADE-ISOLATION-TRANSFORMER-IT400E_W0QQitemZ390006927590QQcmdZViewItemQQptZBI_Circuit_Breakers_Transformers?hash=item390006927590&_trksid=p3286.c0.m14&_trkparms=72%3A1418|66%3A2|65%3A12|39%3A1|240%3A1318

Is that your local surplus store's ebay account?

[doak]

The first thing i would do is ask the people selling them if you could plug one in to see how much noise it makes. Sometimes isolation transformers that aren't made for audio work well electronically but can produce pretty loud humming noise.

Amen.  I've tried out a few that buzzed so loudly you didn't want to be in the same room with them.

[doug s.]

i am a firm believer in isolation transformers, especially on digital gear.  put one on your cd transport and another one on your dac.  the ones mentioned here aren't a bad deal, but not necessarily a great deal, either.  a great deal is getting a 2400va isolation transformer for $50 - but in that case, the shipping may cost more!     re: humming, i have only experienced it w/the mondo units, like the 2400va mentioned above.  but, i have found it to be tolerable, and you can reduce it somewhat by damping the unit w/a heavy metal weight, and tightening up the bolts holding the core together.  these are big enough to use on amps.  expensive new, relatively cheap sometimes on ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=200272399199


if you have the room, and a little extra cash, you can get something like this, rated at 3-4a, which will also allow you to bring up wintage tubed gear slowly, to help reform old caps, instead of blowing them:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110309368053


regarding the specific dale tech trannies mentioned here, be aware that you will need a special power cord or adapter, that has a male iec plug instead of a typical 15a wall-outlet plug - look at the female iec receptacles on the unit...  i would recommend something like this instead (also rated 8a):

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=220284364841


doug s.

[paba]

Hi all,

first off thanks for the input.
To BradJudy, same unit but different seller. My place is brick& mortar so no shipping, just driving by car and in canada. that ebay place is San Diego.
to Doug S., yeah I noticed the female plugs, but that should be an easy swap for me to do.

As for humming. never occured to me so I'll see if I can check it out first. I guess shipping a bigger or better unit will be expensive so I rather find local stuff if possible.

The same store also sells so called european transformers 220 to 110 in various wattage 100 to 3000 Watts. Maybe there is a way to back to back two units and do something like a Felicia.

/paba

[Occam]

Paba,

Those 'European transformers' are in all likleyhood autotransformers rather than actual transformers. Autotransformers do not provide galvanic isolation and are generally not appropriate for line conditioning, and definitely not appropriate for a Felicia.
http://en.wikipedia.org/wiki/Autotransformer

An alternative to large bulky iso transformers, especially if you want to isolate multiple digital components from both other digiital and analog components would be appropriate sized diy Felixes -
http://www.audiocircle.com/index.php?topic=50284.0
This is a 'horses for courses' approach where, with the appropriate components, one can choose to trade VA capability (who needs 2400va when one wants to isolate and condition a 25va component) for far stronger filtering.

Regards,
Paul

[ghpicard]

This is a 'horses for courses' approach where, with the appropriate components, one can choose to trade VA capability (who needs 2400va when one wants to isolate and condition a 25va component) for far stronger filtering.

There's another caveat to the 2400va ones and it is that any power transformer has core losses (mostly hysteresis, some eddie current) that are estimated at about 5-10% of its target design power handling capability. All of that goes to heat the core itself and also leads to nonlinear wave distortion.
With a so low consumption (25VA... 250VA) the transformer would be working way out of its designed parameters and thus excess noise, heating and distortion should be expected... after all, a transformer is intended to transform power, not to keep it for itself

[doug s.]

the only reason one may wanna get a huge iso tranny is if you wanna use it for mondo amps.  otherwise, i agree - smaller is better...

doug s.