[kevin gilmore]

the stax brick for the srm252 is DC, 12V at rated current, and unregulated. If you get the 100V transformer version and run it on 115, the amp will definitely burn up.
The power brick will also burn up.

if the ifi power brick is also unregulated and was designed for 100V, then it too will burn up the srm252.

what happens is the +/-280V ends up over 310v, the caps are rated at 300v, the power is rated at 5 watts max, the bias current goes up, heat goes up etc...

the srm252 sounds a lot better with a high current regulated 12V power supply (say 1.5 amps)

 

[DJ The Rocket]

do not understand why you would suggest thermal noise in this case.

Because people have so many weird ways of describing things that your description could have referred to hiss. In the same way, how you spell the noise a cat makes, for example, varies based on your native language

 

[JimL11]

So, I looked up the IFi website, and their specs for the power supply are 12volts DC at 1.8 amps. They describe "active noise cancellation" but do NOT state the voltage is regulated. Now, it is common for transformers to have voltage drop 10-15% between no load and full load, so my guess is that with the Stax only drawing 4 watts from the wall (1/3 amp at 12 V), the actual voltage output of the IFi is likely 10% high, which is enough to blow the Stax.

 

[DJ The Rocket]

the actual voltage output of the IFi is likely 10% high, which is enough to blow the Stax

I hear people claim to be using 100V units on American 115V mains without their amps blowing, and that's more than 10% high. I don't remember if they were referring to the 252 line specifically though, and they probably weren't.

 

[JimL11]

I hear people claim to be using 100V units on American 115V mains without their amps blowing, and that's more than 10% high. I don't remember if they were referring to the 252 line specifically though, and they probably weren't.

Well, Stax in general runs their stuff conservatively. It depends on how much over specification of components there is. So for example, the SRM-T1 runs at +320volt/-350 volts nominal and has its primary PS caps specified at 400 volts. Going from 100 volts to 115 volts increases the voltages to +368/-402 volts, A lot of places actually have AC voltages of 120 volts, which increases the power rails to +384/-420 volts. Now, components specified at so many volts maximum can often tolerate a bit more, because manufacturing variations mean that in order for every component sold to tolerate the specified voltage, many of them will tolerate more than the specified max. However, as you might imagine, running a capacitor at more than its specified voltage is not a good practice long term.

So yeah, sometimes people can do dumb things without blowing stuff up, but it's still dumb. And it's plain irresponsible to recommend that other people do the same dumb stuff. People drive around without wearing seat belts also and survive - but that's hardly a recommendation to drive without buckling up.

 

[DJ The Rocket]

Right, I wasn't advocating the practice I just wanted a clarification on what the difference was. Which you provided, thank you

So ~13% over the specified supply voltage works out to ~4-5% over the specified rail voltage?

 

[JimL11]

No, the ratio of supply voltage to rail voltage is 1:1, i.e. 20% high supply voltage results in 20% high rail voltage. You are confusing rail voltage and maximum capacitor voltage. Maximum capacitor voltage is, by design, ALWAYS higher than rail voltage, e.g. for the T1, design rail voltages are +320/-350, capacitor max voltage is 400, so there should always be a safety margin. A competent engineer or builder ALWAYS uses a part that is rated to tolerate more voltage/current/power than the part should ever see in normal service. ALWAYS! The problem is when rail voltage is higher than maximum capacitor voltage - that's when things are liable to fail.

Look at it this way. If you are designing a building to resist hurricanes, you have to presume a maximum wind speed, say, 120 miles per hour. For safety's sake, you design it to resist 137 mph - that's a 14% safety margin - the same as the ratio between 350V rail and 400V rated capacitor. But if a hurricane hits with a max wind speed of 144 mph, which is 20% over your assumed maximum (same as the ratio between 100VAC and 120VAC) but 5% over your designed maximum, the building is likely to fail.

 

[miko64]

the stax brick for the srm252 is DC, 12V at rated current, and unregulated. If you get the 100V transformer version and run it on 115, the amp will definitely burn up.
The power brick will also burn up.

if the ifi power brick is also unregulated and was designed for 100V, then it too will burn up the srm252.

what happens is the +/-280V ends up over 310v, the caps are rated at 300v, the power is rated at 5 watts max, the bias current goes up, heat goes up etc...

the srm252 sounds a lot better with a high current regulated 12V power supply (say 1.5 amps)

To add srm 252 works very well with 12v battery

 

[Tinkerer]

Unregulated stuff is just a pain in the ass when any regulated 12V supply even off an external hard drive with a polarity adapter is a no brainer that just works. Sounds better too.

You can even go full ridiculous and slap a GRLV on as the 12V supply. I've done that.

 

[etiefenthaler]

I believe this is right, but best to check with ohmmeter before powering up
remove 1,3,6
add 2,5

result white,green,brown not attached to anything
orange(ppl) and grey together
power on yellow and blue

internal thermal fuse on yellow and white

Did it yesterday. Amp is working fine now on 230V.
Thanks a lot.

Erich

 

[statfi]

Because people have so many weird ways of describing things that your description could have referred to hiss. In the same way

Good point. Language for audio issues is difficult. Clarity is good.
The problem is still there, essentially not getting worse or better, so I am still open to suggestions. I have cleaned away all the old, rotted foam.

 

[hpeter]

stax drivers HV attracting dust ???
You did not looked on bare drivers i guess.
I did on my lambdas and omegas, there are protector foils, no outside air will come in..
Can we finally put this BS to rest ?

Drivers are assembled in dustless area. http://e-earphone.blog/?p=71193 We had in our factory, similar setup when manufacturing security cameras (optic assembly in dustless area)

 

[hpeter]

the stax brick for the srm252 is DC, 12V at rated current, and unregulated. If you get the 100V transformer version and run it on 115, the amp will definitely burn up.
The power brick will also burn up.

if the ifi power brick is also unregulated and was designed for 100V, then it too will burn up the srm252.

what happens is the +/-280V ends up over 310v, the caps are rated at 300v, the power is rated at 5 watts max, the bias current goes up, heat goes up etc...

the srm252 sounds a lot better with a high current regulated 12V power supply (say 1.5 amps)

this is another example why i hate stax amps.
not a safe design, for that price it should be really damage proof ... But it is NOT.
Shame really!

 

[JimL11]

this is another example why i hate stax amps.
not a safe design, for that price it should be really damage proof ... But it is NOT.
Shame really!

Not sure what your issue is. The amp is perfectly safe if used with its stock power supply at the proper voltage. Take any amp used in the US, plug it into a European socket at twice the voltage and it WILL blow up. Take a curve designed for 30 miles per hour at 120 miles per hour and you WILL crash. Nothing can be made fool-proof because fools are so clever and devious.

 

[DJ The Rocket]

Nothing can be made fool-proof because fools are so clever and devious.

A fool is the most dangerous opponent for a master. Fools in general don't get the credit they deserve.