Who came up with the term "Passive Preamp?"
The term is an Oxymoron.
If it's passive, it's not a preamp. A preamp is active ... not passive.
The term is an Oxymoron.
If it's passive, it's not a preamp. A preamp is active ... not passive.
It used to be common to use a transformer as a preamp on a moving coil phono cartridge. Moving coils produce very little voltage, but reasonable current. The transformer boosted the voltage. They were expensive, and considered superior to a SS powered preamp. An example below:
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A transformer is not a preamp. A transformer is an impedance matching device.
If the source impedance is low and the load impedance is high, you will get a voltage step-up. Many microphone preamps use step-up transformers on their inputs. The transformers are not, in themselves, preamps.
If the source impedance is low and the load impedance is high, you will get a voltage step-up. Many microphone preamps use step-up transformers on their inputs. The transformers are not, in themselves, preamps.
And the argument is an old one: the point was aired often enough when passive controllers became fashionable in the early 1980s.
In the sense that a passive controller sits at the input to a power amp, it's not necessarily as daft as it seems - "passive pre-amp" rolls off the tongue better than, say, "before-amp box (with knobs)".
It's still pretty daft but marketing has always been a mystery to me.
Look at the word Preamp, what is it short for? "Pre= before" "Amp= amplifier"
It's saying a pre before the power amplifier!!!
The word preamplifier should never have been used in the first place, it should have just been called a Pre.
Make of this what you like, passive pre's should be called Passive Attenuator because the signal goes through nothing active and they only attenuate.
A Buffered Pre is an Active attenuator without gain.
And then you have an Active Pre with gain.
My 2 bobs worth anyway
Cheers George
It's saying a pre before the power amplifier!!!
The word preamplifier should never have been used in the first place, it should have just been called a Pre.
Make of this what you like, passive pre's should be called Passive Attenuator because the signal goes through nothing active and they only attenuate.
A Buffered Pre is an Active attenuator without gain.
And then you have an Active Pre with gain.
My 2 bobs worth anyway
Cheers George
The amplifier in pre amplifier does not mean the pre am amplifies it refers to the box before the amplifier. This does not have to amplify it could simply impedance match or even possibly reduce teh signal if it is high already.
A transformer can be a pre amp too as again it doesnt have to amplify.
For me, the right term is line stage.
It does not only attenuate, it also controls source selection (hard core solutions like georgehifi lightspeed being an exception). Other possible functions might be SE/BAL and BAL/SE conversion, fixed out (tape out) output… Not everyone needs all these functions.
Pre-amplification is not needed today with sources ~ 2VRMS and conventional power amps. Historically, it was needed for sources around 100–300mV and also term "preamplifier" ment that it includes phono stage.
It does not only attenuate, it also controls source selection (hard core solutions like georgehifi lightspeed being an exception). Other possible functions might be SE/BAL and BAL/SE conversion, fixed out (tape out) output… Not everyone needs all these functions.
Pre-amplification is not needed today with sources ~ 2VRMS and conventional power amps. Historically, it was needed for sources around 100–300mV and also term "preamplifier" ment that it includes phono stage.
It's not complicated.
The word preamp, in it's most literal sense, means nothing more than 'before amplifier'.
There is no intrinsic judgement made on the nature of the device, other than that it is designed to be placed before an amplifier.
So passive preamp is not an oxymoron. Nor is active preamp.
It's no more complicated than that 🙂
The word preamp, in it's most literal sense, means nothing more than 'before amplifier'.
There is no intrinsic judgement made on the nature of the device, other than that it is designed to be placed before an amplifier.
So passive preamp is not an oxymoron. Nor is active preamp.
It's no more complicated than that 🙂
In almost all other uses of the term, preamplifier means the amplifier before the main amplifier. Any other box before the main amplifier has a name which reflects its function (e.g. tuning unit, impedance matcher, filter).
Only in audio has the word 'preamp' been redesignated to mean any box before the main amplifier. A better name would be 'volume control with input selector'.
Only in audio has the word 'preamp' been redesignated to mean any box before the main amplifier. A better name would be 'volume control with input selector'.
The trick is to avoid prejudice (= judging in advance) and previous (= occurring before) misinterpretations of the prefix (= attach before) 'pre', and accept that it means 'before'.
Therefor a preamplifier is defined as being before an amplifier. No other intrinsic judgement is made as to the nature of the device.
A phono preamplifier or microphone preamplifier typically have a gain stage to raise the signal to line level. Line level preamps do on occasion, but don't always. In all cases the defining feature is that they are designed to be placed before an amplifier in a signal chain, so they are all preamps.
Just don't call me pretentious..... 🙂
Therefor a preamplifier is defined as being before an amplifier. No other intrinsic judgement is made as to the nature of the device.
A phono preamplifier or microphone preamplifier typically have a gain stage to raise the signal to line level. Line level preamps do on occasion, but don't always. In all cases the defining feature is that they are designed to be placed before an amplifier in a signal chain, so they are all preamps.
Just don't call me pretentious..... 🙂
preamplifier: n. an electronic amplifier used to improve the the signal-to-noise ratio of an electronic device. It boosts a low-level signal to an intermediate level before it is transmitted to the main amplifier. Sometimes shortened to preamp.
Collins English Dictionary, second edition, 1986.
However, I don't always trust technical definitions from general dictionaries (unless they agree with me!).
Collins English Dictionary, second edition, 1986.
However, I don't always trust technical definitions from general dictionaries (unless they agree with me!).
From my 1970 "Modern Dictionary of Electronics"
preamplifier
An amplifier which primarily raises the output of a low-level source so that the signal may be further processed without appreciable degradation in the signal-to-noise ratio. A preamplifier may also include provision for equalizing and/or mixing.
preamplifier
An amplifier which primarily raises the output of a low-level source so that the signal may be further processed without appreciable degradation in the signal-to-noise ratio. A preamplifier may also include provision for equalizing and/or mixing.
It's not complicated.
Have you ever come across a mic. preamp that doesn't have a gain stage?
And if they aren't? (placed before an amplifier in the signal chain)
Have you ever come across a mic. preamp that doesn't have a gain stage?
And if they aren't? (placed before an amplifier in the signal chain)
A passive level control which precedes an amplifier is not a preamp. It's an adjustable attenuator.
A preamplifier is an active device ... not a passive device.
A preamplifier is an active device ... not a passive device.
In this regard I would like to distinguish between resistive attenuators and inductive attenuators.
The resistive attenuator is just a voltage attenuator, whereas the inductive attenuator transforms.
When the inductive control attenuates voltage (volume), it amplifies current at the same time.
You can also look at inductive controls being impedance transformers: when attenuating, the source impedance is pretty much lowered so that inductive controls are very well able to drive long interlinks.
I would say that inductive volume controls being passive preamplifiers is not far beyond reality.
Who cares?
At this stage in the game it doesn't matter what we call things. What is important is that we all consistently use the same language and apply it to the same thing.
As George and others state:
I take the language as meaning anything that is prior to an amplifier. I have a QED "Passive Control Centre", a 6 input (w/tape monitoring) switch box for selecting inputs with passive attenuator in one box.
An MC phono stage can use amplifiers to increase the voltage (signal) to the point where a typical "preamp" (active) can take over. It can also use a transformer. Active pre-amps often use voltage amplifiers to take the signal the rest of the way from (the typically .3 V) there to a power amp. I think George stated also that an active preamp amplifies the signal and then attenuates it.
The concept of a buffer is to allow the output of a "pre-amp" to drive into (perhaps) complex impedances. AFAIK, the concept is much like providing a current capable output stage. I may be wrong, but that's my take on things.
At this stage in the game it doesn't matter what we call things. What is important is that we all consistently use the same language and apply it to the same thing.
As George and others state:
I take the language as meaning anything that is prior to an amplifier. I have a QED "Passive Control Centre", a 6 input (w/tape monitoring) switch box for selecting inputs with passive attenuator in one box.
An MC phono stage can use amplifiers to increase the voltage (signal) to the point where a typical "preamp" (active) can take over. It can also use a transformer. Active pre-amps often use voltage amplifiers to take the signal the rest of the way from (the typically .3 V) there to a power amp. I think George stated also that an active preamp amplifies the signal and then attenuates it.
The concept of a buffer is to allow the output of a "pre-amp" to drive into (perhaps) complex impedances. AFAIK, the concept is much like providing a current capable output stage. I may be wrong, but that's my take on things.
An inductive control does not amplify anything. It's merely a tradeoff between current and voltage. The source (input) impedance of the inductive control remains pretty much the same. The load (output) impedance of the inductive control is reduced.
As a potentiometer reduces the level, the output resistance is reduced (much like the inductive control). That does not make either device a preamp. They are both attenuators.
As a potentiometer reduces the level, the output resistance is reduced (much like the inductive control). That does not make either device a preamp. They are both attenuators.
Wrong!
Once more: the inductive control transforms; when it attenuates voltage, it amplifies current at the same time.
For instance when we have a 100 ohms source (output) impedance of a CDP 10 times (20 dB) attenuated by an inductive control, the source impedance is lowered to 1 ohm (100 divided by 10²), therefore very well able to drive loads.
When we attenuate the CDP signal the same 20 dB by a 10k pot, the output resistance is some 1k.
Your "much like the inductive control" is actually a difference of 1000x...
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