Subsonics and phono stages with active pre... Can this damage pre?

[SMEagol]

Hi all, I have a borrowed phono stage until my nice one in the profile finally arrives, please no summising the brand of the borrowed phono stage but here's the story. My active pre, blew something then failed in the right channel after a large cone excursion in the hand cone. I wasn't aware of any cone flap until it died, which brings me to my next point.

I have two borrowed pre amps, one a transformer based passive, no cone flap at all. The other one a direct wired straight line passive with no transformers, flaps to the full detent of the drivers this combo, not even in time to the music. It seems having transformers or valves in the signal before the power amps minimises this effect

Could this much subsonic suppression by my active pre have damaged it? As I say a big flap on the right channel then my pre blew. Long arm of coincidence? Or has the phonos all guts no glory signal overworked my pre?

Thanks all.

 

[Cable Monkey]

Coupling capacitors stop DC but allow the signal through. If you have a straight wired pre, you have to have coupling caps on the output of the phono or input of the power amp. If not DC can blow things. A transformer pre isolates DC but can be damaged (saturation) regardless so care is needed.

 

[i_should_coco]

Coupling capacitors stop DC but allow the signal through. If you have a straight wired pre, you have to have coupling caps on the output of the phono or input of the power amp. If not DC can blow things. A transformer pre isolates DC but can be damaged (saturation) regardless so care is needed.

Not ate what you mean here, are you saying that DC will damage the transformers through saturation?

I've heard this said before, but I'm extremely sceptical. Soft magnetic materials won't be damaged by DC, just remove the DC and they'll be fine. Of course, very high levels of DC can damage windings, but you'd need quite a lot of current, even for very thin wire.

 

[Cable Monkey]

It is my understanding of a specific issue I have read about but I can't say it is fact. I use a direct coupled phono pre into my passive but I measured millivolts on the output of my amp so it wasn't an issue for me.

 

[anubisgrau]

someone here on wam wrote how S&B told him that he destroyed his TVC with DC.

i can't remember when an audio manufacturer with a serious reputation shoot his knee so precisely.

 

[i_should_coco]

someone here on wam wrote how S&B told him that he destroyed his TVC with DC. i can't remember when an audio manufacturer with a serious reputation shoot his knee so precisely.

Yea, that was the thread I was thinking of. I asked some transformer winders and they reckoned it was bullshit.

 

[f1eng]

Some phono preamps have subsonic filters built in, some don't (or they are switchable). My guess is you have one of each.

The cone flap is normally caused by output from the cartridge at the resonance of its combined effective mass on the cartridge suspension stiffness, so it is more likely to be in time with warps or footfall than the music.

There is fairly spurious output from record players up to around twice the arm cartridge resonance, so a subsonic filter is a PDG idea IMHO.

 

[SMEagol]

Someone commented that part of the transformer on one of my pre's dual mono trannies could have blown, the fact that the board still lights up means nothing. Must admit there was a pong of brimstone which I normally associate with a cooked traffo. All the valves still light and there's no evidence of the vacuums being compromised. Thanks for the words of wisdom chaps. The jury seems out on this.