dumb amp questions!

[Old Bob]

:hey:

good morning!
from my reading, I now believe I know what Class A, push pull, and class B amps are.

OK- I have an integrated tube amp.
beginner questions:

what do my KT 88 tubes do? do they amplify the signal from the "preamp" section of my amp? do they send this signal to the speakers?

what do my transformers do?

what do my capacitors do?

thanks!
best regards,
bob

 

[audio.bill]

Hey Bob,

Remember there's no such thing as dumb questions, we can only share and gain knowledge from each other by asking questions. Your KT-88 tubes are considered output tubes being the final tube stage of your integrated amp. You are basically correct that they amplify the signal from the previous lower level tubes in your amp, generally the lower power tubes in the initial stages are used to amplify voltage and the output tubes are used more to amplify current. Power (measured in watts) is voltage times current, and your speakers need much more current than the lower level input tubes can provide. The signal is then taken from the output tubes and fed into the output transformers, whose purpose is to provide an interface for more efficient coupling of the power output from the tubes to the speakers. The output tube circuit has an impedance that is much higher than that of the speakers they have to drive so the transformer couples the two more efficiently. Capacitors are used in many parts of the circuit but the large ones you're probably asking about are used in the power supply. Such reservoir capacitors are used in power supplies where they smooth and store the DC output of the rectified AC power. Hope that helps to explain things in basic terms, I tried to avoid getting overly technical.

- Bill

 

[Mikado463]

Excellent explanation Bill, I won't say you took the words out of my mouth for while I knew the process you did a much better job of 'translation' to where it can easily be understood !

 

[Old Bob]

thanks! to Mike Bovaird, and audio bill!

here is what Bill said:
A musical signal is AC (Alternating Current - music is a range of frequencies which is an AC measurement). So the signal being output by the amp, going through the output transformers to the speakers is AC. If DC was sent to the speakers it would just result in a POP and likely blown drivers. Those large 500V capacitors store DC which is used to power the output section which amplifies the AC signal to be able to drive the speakers. As the energy from the caps is used by the amp the power supply replenishes them. With such a large impedance mismatch between the output stage of the amp and the speakers, the amp could not effectively drive the speakers (would be a loss of current which is needed). So the output transformers allow a more efficient transfer of power from the amp to speakers. I think that answers your questions. If you'd like to post your questions with my response to your thread it might be helpful to other forum members but I'll leave that to your discretion.

Happy listening!

- Bill