Phono stage output into SUT output

[Nagraboy]

Seem to have done this by mistake this evening when putting my system back to together. I also had the input of my phono stage plugged into the input of my passive preamp. So I got the input and output of the phono stage the wrong way round. I’ve put it all back together properly now but have harsh distortion. Do you think I’ve destroyed my SUT doing this?

 

[vacuum_tubes]

Potentially, that way it's essentially a step down so you are stepping down the voltage but increasing the current. May be possible to damage the winding by putting too much current through it.

 

[Nagraboy]

Potentially, that way it's essentially a step down so you are stepping down the voltage but increasing the current. May be possible to damage the winding by putting too much current through it.

I’m not sure what happened really. I didn’t send any music signal from the phono stage into the SUT, just the background noise from the phono stage. I wonder if that small signal got back through the SUT and damaged the coils of the cartridge? I did play some music for a few seconds from the cart > SUT, but it was connected to the phono stage output, so perhaps that damaged the phono stage?

 

[vacuum_tubes]

Ah didn't realise the cart was connected as well. Not sure if the cart is damaged, they don't have many windings but do have very very thin wire. I would guess that if the cart windings were damaged it wouldn't work at all on both or one channel. The cart coil wire is so thin It's possible to melt/burn them with a multimeter on resistance test.

Only thing I can think of is to borrow an expendable SUT and cart off someone and swap them in one at a time until the distortion occurs.

 

[Nagraboy]

Ah didn't realise the cart was connected as well. Not sure if the cart is damaged, they don't have many windings but do have very very thin wire. I would guess that if the cart windings were damaged it wouldn't work at all on both or one channel. The cart coil wire is so thin It's possible to melt/burn them with a multimeter on resistance test.

Only thing I can think of is to borrow an expendable SUT and cart off someone and swap them in one at a time until the distortion occurs.

Thanks. I’ve ordered a cheap MM/MC phono stage to eliminate the SUT as a cause. But I can of course also use it with the SUT to eliminate my original phono stage as a cause.

If there’s still noise, I can assume it’s the cart but I do have a 2nd Ortofon SPU to try that idea too.

 

[Barrymagrec]

Depending on the output arrangement of your phono stage you may have magnetised the SUT without damaging the windings. If the problem is the SUT you may be able to de-magnetise it.

Or you may have damaged the phono stage.

 

[Steve Haill]

I managed to burn out one channel of my AT33PTG last week.
I took the cartridge apart after and can confirm that the wires are miniscule.
I could see the break and where it had come adrift from but attempting to resolder it caused the wire to simply melt away as soon as the iron came into contact with it.
So that idea went out of the window. lol
Good luck with your problem.
Hopefully it will turn out to be something that is easy to fix.

 

[40imp]

Barrymagrec, post: 4952905, member: 16918"]Depending on the output arrangement of your phono stage you may have magnetised the SUT without damaging the windings. If the problem is the SUT you may be able to de-magnetise it.

Or you may have damaged the phono stage.[/QUOTE]

Assuming your SUT is mumetal or something similar its not possible to permanently magnetise it by passing a dc current through a winding . See FAQ #17 on the Sowter web site. Might have damaged the phono stage though.