Hello everyone, this is my first post and i'm sure i will offend someone, but can i assure you that i have searched for an answer to this question for about an hour (im on dial up!). All i want to know is - is the most basic of all pre-amps just a log pot with an input and output? Or am i missing something here. If so can someone recommend a good pot? Apologies in advance for my lack of understanding and inability to ever find anything, especially keys.
Hi, welcome to the forum
You are right, a pot with input and output is the simplest. Conventional audio wisdom says a log pot. Some will try to convince you that a linear pot is better; my ears have a log loudness characteristic...
Whether such a simple arangement is satisfactory will depend on a number of factors including impedance, lead length and whether any gain is required. Choice of pot value is important too.
You are right, a pot with input and output is the simplest. Conventional audio wisdom says a log pot. Some will try to convince you that a linear pot is better; my ears have a log loudness characteristic...
Whether such a simple arangement is satisfactory will depend on a number of factors including impedance, lead length and whether any gain is required. Choice of pot value is important too.
hi MPW,
the pot itself can not classify as pre-amp
the word "amp" assumes amplification
amplification happens when signal comming out has higher voltage than signal comming in
the pot can only attenuate the signal, hence classifies as pre-attenuator
properly set up transformer could classify as pre-amp, passive preamp that is
there are quite a few passive preamps out there based on trafo's
some pretty expensive
ed
Indeed there is a sematic inacuracy, but it has got(ten) into our general language, like using the word "battery" for one cell.
Most of us use the term preamp for the control unit prior to the amplifer that is used for controlling it, whether it has gain or not.
Imagine a box with a volume control on it which said "I'm a preamp when my control is at 60 degrees or more, but an attenuator below"
Anyway, don't get confused, just enjoy the banter of the forum.
i did not mean any criticism, i was just thinking out loud
anyway, MPW, best pot is no pot, just stay away
seriously
make it "switching attenuator"
linear or log, does not matter much, just decide input resistance and number of steps
there is ton of web pages about it, just google it
enjoy the music
ed
anyway, MPW, best pot is no pot, just stay away
seriously
make it "switching attenuator"
linear or log, does not matter much, just decide input resistance and number of steps
there is ton of web pages about it, just google it
enjoy the music
ed
In this spirit I have to say, use a decent log volume control. You can put a gain stage in front of it if you want (op amp). Use an op amp, or buffer after the volume control to drive the cable properly. The gain should be around 1 (no gain).
The hard part is the power supply and grounding. An input switch will make this much more useful. After you get this working, you can expand or improve it as your needs dictate.
-Chris
This hit a nerve. I get very annoyed when I hear people that ought to know better refer to a non-active electronic device like a pot a "passive preamp" when "adjustable attenuator" is the correct term. They may argue that any device installed in front of the amplifier may be called a preamp. OK, so a turntable has now somehow become a preamp. In this line of casual dumbed down thinking a resistive attenuator between a power amp and a speaker must apparently be called a "passive power amp". I guess its time for another snake oil outfit to make a bundle marketing simple speaker cables as passive power amps! I mean, you'd expect to pay more for an amp than a piece of wire right!? Backing the car out of the garage on the way to buy an amplifier at a stereo store could also be called a preamp. Rant off.
Glad to see there were some who posted above who also see the stupidity in this.
Glad to see there were some who posted above who also see the stupidity in this.
It's funny how you guys get mad at the interpretation of a word. Literally, pre is the prefix for before and amp is the noun. That means that a pre-amp comes before an amp. Simple as that. If you want to get really technical you should just call it a pre-amp attenuation stage (for a pot or other pre-amp that attenuates the signal).
So, I would agree with those who say that the simplest pre-amp would be a simple resistive divider - it does not matter whether it's two fixed value resistors, a potentiometer, or a switched attenuator.
So, I would agree with those who say that the simplest pre-amp would be a simple resistive divider - it does not matter whether it's two fixed value resistors, a potentiometer, or a switched attenuator.
Careful reading of the original post will show the word pre-amplifier.
Dictionary definition:
pre-
prefix
Definitions:
1. before, earlier
preschool
predate
2. in advance, preparatory
presell
prerelease
3. in front of
premolar
[< Latin prae "in front, before" < Indo-European]
So it never was an amplifier!
Edit: This merely duplicates the last post...
Dictionary definition:
pre-
prefix
Definitions:
1. before, earlier
preschool
predate
2. in advance, preparatory
presell
prerelease
3. in front of
premolar
[< Latin prae "in front, before" < Indo-European]
So it never was an amplifier!
Edit: This merely duplicates the last post...
BWRX said:
Well, sorry, preamp comes from preamplifier (another sloppy shortening of a word), and hey, amplifier is a verb. Something that amplifies. Like a poweramp comes from poweramplifier. Something that amplifies. Or would you suggest that a poweramp is an amp that comes after the power?
But that is not the real problem. The real problem is sloppy use of language which confuses and in some cases completely breaks down any sensible communication. You want proof? These last few posts are the proof. If we would remember and realise that preamp comes from preamplifier, there was no confusion.
Sorry, but having to communicate in several different languages, sometimes simultaneously, and having to make sure I am exactly understood for pain of personal loss leaves little respect for sloppyness.
But the semantic phenomenon is well known. In the UK there used to be (maybe still is) a company called mack that manufactured raincoats. Sure enough, the word mack in the UK is used for raincoat. In Belgium, half a century ago Kodak cornered the photo camera market, and a photo camera in general, whatever the make, was referred to as a Kodak. "Get my Kodak" meant "get my camera".
Jan Didden
Hi janneman,
I agree totally. The fact that the confusion in terms is used to separate people from their money is something that gets me going. I feel the term "amp", short for "amplifier", demands active circuitry. In other words, some kind of power supply (I'll accept batteries) and an active circuit. Even if the voltage gain is |1|, there is current gain.
Passive preamps are flawed. They can not hope to drive the cable even if they are driven from a power amp's output. Well, maybe at 0 attenuation and off (=short, or 0 output). Some power amplifiers are unstable with a high impedance input to make matters worse. So, if you are going to talk tech, then properly understand tech.
Given the physical reality, I don't want to hear from anyone about the sound of a (Grrrrrr) passive preamp
.
-Chris
I agree totally. The fact that the confusion in terms is used to separate people from their money is something that gets me going. I feel the term "amp", short for "amplifier", demands active circuitry. In other words, some kind of power supply (I'll accept batteries) and an active circuit. Even if the voltage gain is |1|, there is current gain.
Passive preamps are flawed. They can not hope to drive the cable even if they are driven from a power amp's output. Well, maybe at 0 attenuation and off (=short, or 0 output). Some power amplifiers are unstable with a high impedance input to make matters worse. So, if you are going to talk tech, then properly understand tech.
Given the physical reality, I don't want to hear from anyone about the sound of a (Grrrrrr) passive preamp
.-Chris
The man asked for pre-amplifier, that's the name of the thread.....though in truth I had not made the distinction between pre-amplifier and preamplifier
Language deveops. Language is not what is written in text books, but vox pops, like it or not. I hate some modern language usage, but you have to accept it or not communicate.
Amplifer, verb? Not in my language.
Language deveops. Language is not what is written in text books, but vox pops, like it or not. I hate some modern language usage, but you have to accept it or not communicate.
Amplifer, verb? Not in my language.
anatech said:
Hi Chris,
Yeah, long time. I still want to continue with you on what we were discussing. Unfoirtunately I have not had a chance yet this entire year to think about audio projects.
Wire with gain and stupid ba star dization of technical terms to make money. OK, gain is often measured in dB and wire begins with the letter W. By golly I think I have it. Let's call this product dBW. That even sounds like a technical term right?!
Rob
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