amplification

jimlov4

My question is:
If I imput an audio signal (mic line whatever) thru a volume control into any amp I would think I should be able to control the output with the volume control. What I am doing is using an amp as a preamp.:rolleyes:

mhardy6647

Where is your "volume control" coming from? I am a little unclear on what it is you are asking... no, check that. I am completely unclear on what you're asking.

Magic Eight Ball would say... "Ask again."

An "active" preamplifier will provide gain and may provide equalization options (e.g., tone controls and/or RIAA equalization and amplification for records); it also usually serves as an impedance buffer between source and (power) amplifier. A "passive preamp" isn't necessarily an oxymoron, though! A passive preamp provides no gain, EQ, nor buffering - it's usually a variable attenuator (either a potentiometer or a multiply-tapped transformer or autoformer) to reduce the signal level being supplied to the power amplifier. A passive preamp may or may not also include source selection (i.e., several stereo pairs of inputs and a source selector switch to route any one of them through the attenuator to the passive's output).

I use a passive preamp with a source selector and an autoformer volume control - which may be what you're asking about?

These guys (actually this guy, Dave Slagle) builds the AVC that's in mine...
www.intactaudio.com

jimlov4

I see a volume control as the first item in an amp. The signal is across the entire resistor portion and the pick portion is coupled thru a cap to the amp. I am a novice where electronics are concerned but it seems to make sense that a small medium or large signal should be amplified the only difference is how much noise you hear which is controlled by the volume control

John K.

Jim, welcome to Club Polk. If the amplifier has a level or volume control, what occurs is that the amount of incoming voltage is controlled by a variable resistor to let through practically 100% or almost nothing. This amount of voltage is then subjected to the fixed gain(home audio amplification equipment is not gain adjustable), which is typically about 29dB, and which remains the same regardless of whether the level control is near min, about mid-way or near max.

So yes, the amount of output can be controlled in that way. This isn't really using it as a "preamp" however, since by definition there would have to be a section of preamplification, rather than just a level control. The term "passive preamp" used by some makers is a misnomer.

mhardy6647

I used to feel that way, too, but I've drunk the Kool-Ade and would now opine that a "preamplifier" is, quite literally, just something before an amplifier... it does not have to be active (i.e., contain active devices; transistors or vacuum tubes). An AVC and source selector is a completely passive device; one certainly doesn't have to call it a "preamp" - but one may.