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


I used to combine with a tube pre + transistor power with the ideal sound which I prefer. But one of my friend told me recently that such kind of combination will burn out power amp. easily if I use a tube pre.

Is this theory or practice true?


faust168

Short answer = Tell him he’s dreaming!!

Long answer = Tell him he’s dreaming!!

Bet he's a fuser

Cheers George
What utter nonesense; manufactures such as Modwright, Herron , etc sell separates that are tube preamps and solid state power amps

just an Old Wives Tale


Post removed 
Only a problem if you buy them from a white van in the back of the mall parking lot.
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.
I ran a Classe solid state amp with a Modulus 3 tube preamp for 20 years and presently run a Stratos  solid state amp with a Rogue rp5 tube preamp.  Your friend doesn't know what he is talking about.
Thanks a lot for your kind response and opinions. In fact, I use a tube pre. to run a SS power for a very long time without problem. But once upon a time, I turn on the volume to squeeze more power to play the Japanese Taiko (big drum) with more solid bass, one side of the MOS FET had been burned together with one side of speaker (the unit handles the high frequency driver).  Judging on such long time experience, I think it should be no problem to use a tube pre and the SS power. But my friend is a Dr., so I have to respect his professional even though I still regard it should be safe or little risk only. I will hear more opinion from audio dealers. Any way, tks again for your precious suggestions.  
 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.
Some consider me to be an expert... the idea that a tube preamp can do anything to a solid state amp in particular is a myth plain and simple. Coupling caps being old has nothing to do with it. Its just a myth and no matter who is trying to propagate it, its still a myth.

Solid state preamps have coupling caps too and are just as failure prone in this regard as a tube preamp.

Well the fact is that all sorts of things can cause amp-dangerous thumps! This is not a solid state/tubes thing, because solid state preamps can easily make thumps! This is why many solid state preamps often have output muting protection relays. Many tube preamps do as well. But a protection relay is just about guaranteed to mess with the sound, so many preamp designers expect the operator to have some common sense and follow the procedure below:

Its just a matter of being careful- when turning on the stereo, always turn on the preamp first and wait for it to stabilize. Then turn on the amp.

But my friend is a Dr., so I have to respect his professional even though I still regard it should be safe or little risk only.
Apparently this is an example of having a doctorate but still having no clue about what one is talking about. In this case his opinion is just that and its bunk.
atmasphere,
  


    Thanks for your expert validation that tube pre-amps cause no harm to ss amps. 
 

Dear Sirs,


Thanks a lot for your kind response.

Which tube pre has better combination with Accuphase A-47 for pushing Dynaudio Contour 1.3SE.