The Simplest Pre-Amp

[angel]

Originally posted by dhaen
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...

Actually, I'd love to know how you managed to get your ears to follow a log curve. Mine tend to follow an equal-loudness contour, roughly.

Considering how any deviation from this contour will, at least in my case, result in a much more gross distortion than anything an active circuit could produce, I'd say it's all a matter of taste until you somehow find a nice way of adressing this problem..

Seriously, though, it comes down to simple preference and the technical requirements of the upstream and downstream equipment.

[hermanv]

Instead of all this banter about language, let's answer the question.

1. A pot will work; to sound best it will end up being an expensive pot. Alps and Noble are two popular brands
2. You will need two pots or a ganged pot for stereo, more of them for more channels.
3. "Passive" pre-amps typically will still have volume control range left when the amplifier is being overdriven. This is not always true but usually is - i.e. the simple solution is valid and works for most cases.
4. Switched attenuator "passive" pre-amps are generally regarded as being a step up from designs based on pots.
5. Using the best resistors (usually agreed as the Vishay S102/ $11.50 each) and a solid silver switch like those made by Schallco will result in a world class design and will end up costing you close to $500 depending on the box, the number of inputs and the price you pay for good wire and connectors.

Many people once having heard a truly good "passive" pre never look back. I am one of those, I built my own and it sounds glorious.

I bought my supplies from Michael Percy Audio he carries what is needed to build a passive pre to many different cost points, there are certainly other suppliers. A used passive can sometimes be found for less money than it takes to build one. Try "Audiogon" or e-bay search for passive.

Good luck

[anatech]

Hi Rob,

Now, that will sell! We can even colour the sound with the jacket colour! This will help tune the system.

I'm gonna call Belden first thing tomorrow. Can you handle the guys at Alpha?

-Chris

[BWRX]

Originally posted by janneman
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?

Jan Didden

Originally posted by dhaen
Amplifer, verb? Not in my language.

As Jan has mis-stated, and dhaen has pointed out, amplifier is a noun not a verb. Therefore, the explanation for the definition of the word I stated still holds.

Amplify is a verb.

Originally posted by hermanv
Instead of all this banter about language, let's answer the question.

1. A pot will work; to sound best it will end up being an expensive pot. Alps and Noble are two popular brands

That depends on what you deem "expensive" and "sound best". You can get the Alps Blue Velvet pot for $20 from some places. That isn't bad at all for it's good tracking, true logarithmic curve, and good quality. I use one with my little amp3 and it sounds good to me! That's really all that matters anyway

Brian

[resolution]

Simplest preamp - wire with gain!

regards

res

javascript:smilie('')
smile

[sagarverma]

use of good opamps like opa2134 is advised for good sound reproduction.avoid anything lower.i replaced tl072 in most of my circuits that had gain and results were dramatic.
dont go overboard in buying componentslike fancy wires and resistances,connectors etc.they jus inc total cost and provide little or zero sonic improvements.
use quality components but not those things as audio grade wires and all that misleading stuff

make a simple preamp,make an opamp to have gain.see opa2134 datasheet for req ckt.u will b very happy to have built yourself such a nice ckt at the first shot.

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?

great grammatical skills teaching english in elect. forum

[rcavictim]

Originally posted by anatech
Hi Rob,

Now, that will sell! We can even colour the sound with the jacket colour! This will help tune the system.

I'm gonna call Belden first thing tomorrow. Can you handle the guys at Alpha?

-Chris

Chris,

OK, I'm onto Alpha as well as Times first thing tomorrow. As for color you obvioiusly read my mind! By adhering demonstrably to well known laws of physics, red could be used to accent the bass, green would give midrange extra presence and of course blue dBWireTM would be the choice of those looking to add air to a system that sounded too stuffy.

Combining two, or even three colors in a patented matrix ought to work well in waking up even the most expensive speakers! By series connecting different colored sections of dBWireTM in one speaker run even the most stubborn room issues should be tamable!

Seeing the full spectrum enhancement version employing a matrix of the three primary colors as our ultimate offering, obviously the most expensive version, the matrix could be applied at such a high density level that the cable would literally appear white. Might I suggest we call this really good one Zip wire? That sounds really catchy don't you think?

We best hurry this to market before someone else reads this and gets wind of what has to be one of the best hi-end audio accessory product ideas to be conceived of in years! I'll reserve a full page ad in next month's Audiophile too as I have observed that magazine to apparently be the best forum to market such great hi-end audio product ideas as this.

Wow, this is exciting. We're gonna be rich!

Rob

[rcavictim]

Originally posted by resolution
Simplest preamp - wire with gain!

regards

res

javascript:smilie('')
smile

Chris,

We better hurry, they are already starting to figure out our good idea!

Rob

[jan.didden]

Originally posted by dhaen
[snip]Amplifer, verb? Not in my language.

Mea culpa...

But still, it is something that amplifies. If a preamp was something that would come before an amp, all sources CD player, DVD, tuner would also be a 'preamp'. Which I don't believe is the case.

But I agree on your view on language as a living thing. Consider that originally we would say: "this new IC is being shipped to customers as of November". Nowadays the press release simply would say: "this new IC is now shipping". Which is of course a physical impossibility, but yet the meaning is clear. I think. Same with sampling. "This new IC is now available in sample quantities" becomes "this new IC is now sampling" which is only technically correct for an operating sample and hold or sample rate converter or whatever.

Jan Didden

[Christer]

While "passive preamplifier" is a somewhat strange term, it is not unusual with such abuse of language. We also have "zero-Ohm resistors", just to take one example. Such a resistor has most of the properties of a resistor, except the most important one: it lacks resistance! Still, the use of this component is such that the other resistorlike properties are very important and in many aspects it makes sense to call it a resistor, although it is a degenerate case. It is the same thing with the passive preamp. A preamplifier is something that is connected between the sources and the power amp. It usually has a volume control and source selector, and often also tone controls and other features. Traditionally, the preamp includes an amplifier and has gain, which is why it is called a preamplifier. Nowadays, most people use only high-level sources, like CDPs, so there is no need for gain in most cases. That is obviously why people started to skip the amplifier part and kept only the volume control, and often the source selector. While the device no longer has any gain, it still provides the main functions of a preamplifier, you can adjust the volume and often also select source. Logically, it still has the same function as a preamplifier, with one exception: it doesn't amplify the signal! However, if there is no need to amplify the signal, then it doesn't matter. Just like the zero-Ohm resistor has all the properties of a resistor, except one, which is not desired anyway, the passive preamplifier has all the properties of a preamplifier, except one, which is not required. The problem with calling it something else than a passive preamp is that we then need to come up with a good term that encompasses all variations and also gives a fair description of its function. Calling it just an attenautor won't do since it will sometimes also have a source selector and maybe also a buffer. The term to be used must fit all such variations. Any such term would probably be a completely new term, which is unfamiliar and doesn't give any immediate clues to its function, while the term passive preamp does give quite a good idea about what the device does.