Tube Pre+ Transistor Power will burn your power Amp. easily?

Not true, so long as the Tube pre is working correctly.

However, there IS a failure mode which will cause this. Tube pre's have hundreds of volts of DC offset. This usually stays inside the pre-amp thanks to an output coupling cap.  I quoteth myself:

Most tube preamps are 2 very nice output coupling caps surrounded by tubes and a bunch of other stuff

If this coupling cap should fail (extremely unlikely with modern FILM caps) then yeah, you have insta-death of the amp.

Tube amps are going to be more immune to this problem but not entirely.  They usually have their own film input caps, and tolerant of high voltages anyway.

Best,

E

Faust 168,

     I agree with your other responses, I think this is not valid but I'm not certain.  I'd like to find out from an expert just to be certain.

    On the one hand, I combined a tube VTL pre-amp with a ss Aragon amp for years and it sounded very good.  I know it's very important to make sure the input impedance of the ss amp needs to be at least 10 times the output impedance of the tube pre-amp for a good match.  But I've never heard of these combos causing harm to the ss amp.

     On the other hand, some capacitors in my ss Aragon amp's power supply leaked after a few years and I had to replace it.  However, I attributed this to the amp being 15 yrs old and not to using a tube pre-amp.  I think I'm correct but am not certain.

     Better safe than sorry,
           Tim

LIttle more:

Not all tube pre's have this minimal risk. For instance, if the output is transformer coupled, or balanced. Most tube pre's are single ended.

If you truly have a vintage pre-amp (before 1980's) then you absolutely owe it to yourself to check the coupling caps (input and output) and replace all with modern film types.  Electrolytics will be failing by now, and older films just didn't sound as good. :)

Best,


E

There have been times when I have seen someone cause issues with a solid state amp being ruined by a tube pre but in every case it was due to turning both the preamp and amplifier on at the same time not allowing the voltages of the pre come up first.

@response34

That IS interesting. Since the caps pass AC, it’s possible a very high voltage ( >> 30V) turn on thump could occur. However, honestly that would damage the amp even if off. It would most likely break through most electrolytic coupling caps and if DC coupled, short several transistors. Of course, if a speaker was connected, things could get even worse! :)

Perhaps what tube preamps really should have is a coupling cap + zener diodes to prevent the possibility of high voltages reaching outside.