Newbie question: Amplifiers, Volume, Clipping?

Hi Al and Hifihvn: I had a question about tube amp clipping. In the case where the tube amp uses output trannies, if the signal fed to the primary coils in the output trannies clips, what type of output is induced into the secondaries?

Let me elaborate. Al explained that "[c]lipping means that the positive and negative peaks of what would normally be a smooth sinusoidal waveform will abruptly transition to a flat, essentially constant output level corresponding to the maximum positive and negative voltages that the amp is capable of delivering."

So, if the input to the primary coils transitions to a flat non-alternating voltage, is it possible to induce a voltage in the secondaries?? If the answer is no, I would think that the clipping would be expressed as a distorted output wave form, but not necessarily of a type that would damage speakers. I imagine the distortion would sound terrible though.

Alternatively, if the signal fed into the primary coils wildly oscillates as bursts of positive and negative voltage, wouldn't the output voltage still be limited to some extent by the output trannies? I suppose in this case, while the output trannies wouldn't be passing pure DC to the speakers, the widely oscillating signal fed into the primaries could induce bursts of oscillating DC voltage which perhaps in extreme cases might damage speakers.

I ask because I own a 130 wpc tube amp that drives speakers having a sensitivity 89 db and a nominal impedance of 8 ohms. As you might imagine, my rig can get quite loud without having to push the amp. Hence I am somewhat dubious that I clip the amp because my wife would start screaming bloody murder to turn the da** stereo down way before a clip. She's better than any speaker fuse on the market today. I would say she a hyper fast fuse -- a real live wire.

Thanks for the clarification.

Hopefully Almarg will answer these questions. If I would, my answers might be in error, and confusing.

Hi Bruce,

My statement about the output waveform abruptly transitioning to an essentially constant level was not worded as completely as it should have been. The "constant level" will persist only until a tiny fraction of a second later, when the input voltage to the amplifier is alternating in the opposite direction and is no longer demanding that the amplifier put out a voltage that is larger than it is capable of. At that point there will be an abrupt transition FROM that constant level back to the normal sine wave or sum of sine waves that constitute the musical note.

That pair of transitions will occur near both the positive-going and negative-going peaks of the waveform. Hence the tops and bottoms of the waveform will be "clipped off," which is why it is called clipping. In between those extremes, the waveform will be as it should. DC is not involved in any of this.

The output transformer will pass whatever spectral components (frequency components) of that clipped waveform are within its bandwidth, its bandwidth in most cases being much wider than the nominally audible range of 20Hz to 20kHz, and encompassing most or all of the extraneous (and potentially damage-causing) treble energy that I referred to.

Best regards,
-- Al

Almarg, while admittedly I flunked high school physics and can't always grasp your technical discourse, I always enjoy you're posts--they're unfailingly polite, patient, positive and informative. Thank you for being you.

If 96db avg levels are not sufficient ... either get another amp... or more eff speakers!

Why wonder about where you can break them with the volume knob?

Usually, soft clipping in tube amps sounds like fuzzy audio... distortion in other words, but the clarity of the audio begins to vanish and becomes less distinct. Vague. Soft & fuzzy!

The only other item I can figure out here is that the speakers may be fairly eff, but their imp curves are not quite so friendly.

AS OP said already, these items are not a super great match. Well, then... figure out which is the better item, amp or speakers and keep that. Sell the others.

Or .... get OK with listening at lesser SPLs.

Personally, I"ve never twisted the vol dial above 2 o'clock since I turned 17... and blew my first speaker. Ordinarily, if I have to get above the noon mark on my preamp for pretty good levels, I might have a poor match on my hands and I'm figuring something ain't right already.

the days of twisting that knob all the way over are gone for me. I simply will not do it!

Very good luck developing your outfit.