Clipping and the pre amp...


So, as I understand it, clipping occurs when you drive a speaker at close to the amplifiers total output power. Where I lose comprehension on this thought, is when I modify the input to the amplifier. My preamp, an LS25 MKll, in addition to the volume control, has a variable gain switch. The switch is marked with Low, Medium, and High positions. The instructions are to run the preamp with the switch set on the lowest needed position for whatever source you're running at the time. Does it matter then, if I've got the volume turned up high on the preamp, with the gain set to low? Am I more likely to run into clipping as I'm asking the amps to push near their limits to amplify a smaller signal? Or, are the amps not working that hard, as they're not amplifying a big signal to a big volume?

The preamp remembers positioning for you from the last listening session, so it's a set it and forget it thing. I do find the sound more to my liking with the pre amp gain set lower, and the volume set higher.

Or, is this a mute question as it's all related to the speakers? In my case they'd be the Gallo Reference 3's...


The "amplifier stage" is your amp, preamp, and source put together. The more gain your preamp contributes, the less your amp does for the same volume level. So if you turn the gain up on your preamp, the amps won't clip till further up the volume level. It is additive.

The source gain works the same way but adds a twist. If you take CD for instance, you get 2V to start with (roughly) but then very often your preamp won't output that much for your chosen volume level! Many times, a preamp will only attenuate the signal at the volume control and the gain stage won't contribute to anything. Hence the reason passive preamps exist.

This is assuming the volume stage is at the input. When this is the case, you need to have your preamp's volume control work in its "sweet spot." For your preamp, the sweet spot is at the top of its potentiometer (when it's nearly out of the circuit). This is the typical sweet spot location whether you are in the digital or analog domain and is why your instructions say to use low gain and high volume to get the best performance.

The pre-amp does very little except to attenuate (in the case of a 2 V signal) in this sense it is just a volume control. You should avoid clipping in either the pre amp or the power amp. Your S/N will improve if both devices are operating in their comfort zone (away from either end; fully attenuated or maximum output)
this is probably a dumb question.
can someone explain the difference betweeen gain and volume?
Gain describes the increase or decrease of an electrical signal. Volume describes loudness of sound. Increased gain will result in greater volume. Real audiophiles say "SPL" instead of "Volume" :-)
Sounds like a chicken and egg thing. In this case we know, you can't have an increase in the SPL's without increasing the level on your gain or your volume switch/knob.
I guess the answer then is, that if the gain is turned down, and the volume turned up, it's the same thing as if I had the gain on high and the volume at low, to the amplifier. Therefore, no clipping. This seems to be the logical explaination?
Perhaps you are having a problem with the very inexpensive "Dallas" digital chipset used in the ARC. It will overload if driven a highish input signal from a phonostage or digital source. That is why they have LOW-Med-High on the input control. You will also notice that their phonostages only put out max 57.5 gain. The Ref series had one input paded down to 12db gain to avoid the problem of "clipping" the input. Personally, I would never use ANY source component or linestage that attenuates via a digital control. FWIW, the new ARC Linestages no longer have this problem, but are still digital.
Actually, I'm not having any problems at all. I was only wondering, at the beginning of the thread, about the mechanics of clipping.The "overload problem" you mention is one I've not heard of in association with AR gear.
It works well for me though.
I am I guess an Audiophile, though I prefer music lover above that odd sounding audio tittle, but I have never asked anyone to turn up or give me more I out of the club now? :)
Your membership to the club is always guaranteed as long as your dues are paid up. I accept checks, cash, and credit cards.
Seriously though, SPL's are dependent on so many variables. Humidity, elevation, proximity to the speaker. Perceived volume would also be dependent upon these variables, and would include the acuity of ones hearing. What volume wouldn't include was the use of an SPL meter. Seems simpler to have a volume control knob if only for this reason...