Modern Stax Amps and Country Voltages

[wower]

This is just a quick question for the more engineeringly minded or another new thread to ignore while everyone is refreshing Boomana's "disturbing" thread:

I have used search and have tried more refined searches of the huge History of Stax thread but have not found a clear answer to my question. I can buy a stax amp in Japan for a good price from an online retailer. What I have concerns about is the unit's 100V voltage setting and what happens when I bring it home. I have gleened from the forum that it's harder to change the voltage on the more modern stax amps, but does that mean it's impossible? Do I just need to take it to the Canadian dealer when I can home? Is it as simple as just opening the unit up?

Thanks!!

 

[spritzer]

Quote:

Originally Posted by wower /img/forum/go_quote.gif This is just a quick question for the more engineeringly minded or another new thread to ignore while everyone is refreshing Boomana's "disturbing" thread: I have used search and have tried more refined searches of the huge History of Stax thread but have not found a clear answer to my question. I can buy a stax amp in Japan for a good price from an online retailer. What I have concerns about is the unit's 100V voltage setting and what happens when I bring it home. I have gleened from the forum that it's harder to change the voltage on the more modern stax amps, but does that mean it's impossible? Do I just need to take it to the Canadian dealer when I can home? Is it as simple as just opening the unit up? Thanks!!

In the good old days Stax used either a special voltage selector switch or transformers with solder tabs with the right internal connections. Then they started to make it harder and harder wiring the 100v units differently and now it is very hard to convert. The primaries are all soldered to a PCB with a specific pattern for each setting and we do not know what they are. The problem is that the gray market dealers do not know either so the amps are stuck at 100v. You could always figure it out by either removing the transformer from the circuit and testing the various combinations or just trusting blind luck. I'm sure that the dealer will not help you or make you pay a small fortune for the conversion.

 

[d-cee]

yeah, that has put me off getting a new driver unit because the voltages cannot be changed easily without a transformer

buying locally would cost me my car and more!

 

[kevin gilmore]

Actually i know every single combination of the circuit board.

Trouble is it does not do any good any more. The 100 volt units
actually have the wires on the 115 volt windings cut off very
close to the transformer. Sometimes the wires are long enough
if you are good enough to solder extention wires back to them.
I've seen a few units with more than 1 inch of wire, those are
very easy. Saw one with .25 inch of wire, that one was tough.

Otherwise you are limited to either 100vac or 200 vac.

A variac set at 100 vac works just dandy and is no more than $50.
Or a 100 watt 115 to 100 vac transformer, about the same price.

 

[wower]

Hehehehe.. funny Gilmore-san himself entered my humble thread: I was going to come back and post that I guess I was stuck with buying the phones here (404s) and getting a 3rd party amp back home because that is where I'm heading one day anyways (the O2 that is). I wanted something solid state which really only leaves the KGSS. I would go the external transformer route but I would need a couple of outlets and they all only come with one outlet (on my budget). There's a used KGSS on audiogon now for $600 which is a steal! Alas the time is not right.. I got my yammy this week.

I take it spritzer's and Kevin's word will finally close the issue on head-fi forever. We at head-fi thank you.

 

[kipman725]

you could simply replace the entire transformer.

 

[wower]

Quote:

Originally Posted by kipman725 /img/forum/go_quote.gif simply

"Simply" being the optimal word there. I wish I could pick up the KGSS on audiogon now. Those things never come up used.

 

[educator]

Quote:

Originally Posted by wower /img/forum/go_quote.gif There's a used KGSS on audiogon now for $600 which is a steal!

That's an auction on audiogon. The final price will probably be much higher.

 

[jcn3]

117V to 100V set-down transformers are so inexpensive. this is the easiest and "safest" way to solve the problem.

 

[spritzer]

Quote:

Originally Posted by kevin gilmore /img/forum/go_quote.gif Actually i know every single combination of the circuit board. Trouble is it does not do any good any more. The 100 volt units actually have the wires on the 115 volt windings cut off very close to the transformer. Sometimes the wires are long enough if you are good enough to solder extention wires back to them. I've seen a few units with more than 1 inch of wire, those are very easy. Saw one with .25 inch of wire, that one was tough. Otherwise you are limited to either 100vac or 200 vac. A variac set at 100 vac works just dandy and is no more than $50. Or a 100 watt 115 to 100 vac transformer, about the same price.

As I haven't peeked inside any of the new amps I don't know whether you can access the windings and replace the wires altogether?

 

[kevin gilmore]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif As I haven't peeked inside any of the new amps I don't know whether you can access the windings and replace the wires altogether?

So far, 2 units, the wires were accessable and replaceable, one unit
was very iffy so i did not try.

It would likely be possible to have a transformer manufacturer make
a custom replacement transformer the same physical size, but it would
likely require a group buy of about 25 transformers, estimated price
about $150 each. You need 2 x 0,100,115 volt primarys, 2 x 275 volt
secondaries, and 1 x 30 volt centertaped secondary for the solid state
units, and an additional fillament winding for the tube unit.

 

[spritzer]

Quote:

Originally Posted by kevin gilmore /img/forum/go_quote.gif So far, 2 units, the wires were accessable and replaceable, one unit was very iffy so i did not try. It would likely be possible to have a transformer manufacturer make a custom replacement transformer the same physical size, but it would likely require a group buy of about 25 transformers, estimated price about $150 each. You need 2 x 0,100,115 volt primarys, 2 x 275 volt secondaries, and 1 x 30 volt centertaped secondary for the solid state units, and an additional fillament winding for the tube unit.

Thanks for the info. I replaced the wires in my T1 and it was very easy to do so I was hoping that stayed the same.

I believe step down transformers are the best option and if anybody it worried about their quality degrading the sound they could always have Audio Consulting build one with silver windings for about 8k$...

 

[krmathis]

Quote:

Originally Posted by spritzer /img/forum/go_quote.gif I believe step down transformers are the best option and if anybody it worried about their quality degrading the sound they could always have Audio Consulting build one with silver windings for about 8k$...

Woah! $8K for a transformer.
I am sure it would sound great. But thats some price tag!

 

[spritzer]

Quote:

Originally Posted by krmathis /img/forum/go_quote.gif Woah! $8K for a transformer. I am sure it would sound great. But thats some price tag!

That's no run of the mill wire or core material there and add that to being done by hand in Switzerland it can get pretty expensive, fast. Still it's a lot for a transformer.

 

[krmathis]

Some useful information in here. Thanks!
Sad to see that Stax make it so difficult to switch voltage on their amplifiers. But its hard to blame them, since they need to protect their western distributors against they grey market import from Japan.