Passive or Active preamps = what's your take?

Which sound better ? Passive attenuator or active preamplifier ?

Chicken and egg situation!
It's more on personal preferences and of course how critical listener and purist are you..
I have listened to both, active is my preference...

passive cheap cheap good good. Like that Promitheus TVC unit.

if got extra $$$ and want some extra bling-bling... get active.

Or if u got 2 or more sources (LP and CD, cassette deck, minidisc layer, etc) then no choice must get active unit unless u like to plug and unplug cables just like Borat doing a Grip-Pull Grip-Pull Grip-Pull Grip-Pull ... then success, liquid explosion!

u can get a passive pre with more than 1 input
but cannot tahan the cost, its like better off buying active
its expensive becoz the material being used & rarities factor

habis cerita.

i was surfing around and found this. i thought it would be a good read on this thread. it's from www.ftaudio.com, the website of a hong kong company that makes a highly-rated passive preamp called Little Wonder LW1S2.


Why Passive?
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Most people ask the same question when coming up to try passive. The same question seems never appear to them on using active pre-amp. The answer is as simple as Why Passive = Why Active.

If you look up to the characteristic curves of active components (tube, transistor and FET), the design operating criteria is using the best linear region. In other words, our engineering approach is to assume they are approximately linear. In fact, there is no perfect linear amplification so far. The more active stages we inserted into the circuit, the more non-linear distortion added.

We follow "Simple is beautiful". The Little Wonder implements the shortest signal path where using the best passive elements to preserve the original signal.

Should we ask now, Why Active?


What is passive? Does Passive Control Unit or Passive Pre-amp have gains?

The meaning of passive refers to the equipment itself does not acquire external energy sources.

Can passive element amplify? Yes indeed if it is designed to do so. Passive can have voltage or current amplification, but no power gain. Remember the old day vinyl LP, there are MM and MC cartridges, MC cartridge is a low voltage signal source. To boost up voltage signal amplitude, an MC step-up transformer is used. By definition, MC transformer is a passive voltage amplifier. Passive design involves no active elements as tubes, transistors or FET, no external in-feed energy such as battery, DC/AC power supply.

What is the CD/SACD output signal? In what way we can use Passive Volume Controller?


A CD or SACD player reads digital codes from disc; all binary codes would be converted to analogue signal by Digital to Analogue Converter (DAC). From then on, it feeds to analogue filters and finally into a line stage or a buffer stage. Normally, CD/SACD output is of nominal voltage signal 2V. That comes to a logical conclusion, insert a volume pot in between CD and power amp to control voltage level, and this in fact controlling the sound level.

I wonder if a 2V signal from CD output is enough to drive power amp, should I choose a CD/SACD with a 3V or even 6V output?

No, a signal level more than 3V from CD/SACD output would degrade the sound quality in most system no matter it is using active pre-amp or passive.

I try to design a passive volume control myself, I hook up the CD output to a 100K-1M volume pot, but it sounds harsh, no bass punch and limited dynamics?


Passive Control Unit is never equivalent to just a volume pot. Study with care when you connect a volume pot to the CD output, voltage signal is passing through a series of high value carbon film resistive elements. Ohm’s Law only defines the voltage level across the power amp. It does not tell you how good is the signal. The high resistive elements in the signal path cause a low pass filtering effect and the signal anticipates early high frequency roll-off. From experience, harshness on high pitch means deficiency in high frequency region.
The Little Wonder incorporates an X-coupler to let pass full range audio signal while maintaining very low noise level. The result is obvious, a controllable voltage level with non-distorted signal.

Is Active more dynamic than Passive?


Our claim to “Passive is Dynamic” is about the same as Mr. Columbus claimed the earth is round. The same question asked when The Little Wonder LW1 was reviewed by UHF. Take a minute to read the audio review. We have proved to all our customers that The Little Wonder is equal, if not superior in every dynamic response to most active pre-amps available.

I don’t know if my CD player and my power amp are suitable for passive controller or not?


In general terms, The Little Wonder only requires a standard 2V output from CD/SACD and impedance less than 5K. The power amp input sensitivity under 2V and impedance more than 15K. Home listening is always the way to find out the truth, e-mail to us and try our no frill home trial. We offer 30 days money back guarantee.

What advantages on using The Little Wonder as pre-amp?


On sound quality counts, it is hard to find an active pre-amp that cost 4 times or even more that can match The Little Wonder. The Little Wonder is the biggest steal in the Hi-End market. The new approach to circuit topology with premium grade components account in The Little Wonder gives what you dream of, faithful, natural and truly undistorted sound quality. We care of inner details of music which tells passion and illusion yet that seems never happened on passive before.

Further more, The Little Wonder is always ready to sing, no need to warm up like tube pre-amp taking hours to settle for better sound.

The Little Wonder is energy save. No need for silly price water hose like power cord for pre-amp.

Do we need high efficient speakers when we use Passive pre-amp?


For high efficient speakers, you need lower power to drive the speaker to desired sound level. In this area, we interpret the energy demand is correlated to speaker efficiency. For less efficient speakers, they are much power hungry, it is better to use muscular power amp. The fact is, each power amp specifies input sensitivity, it is the voltage that count. As long as a voltage signal can drive a power amp to full output power, there is no distinction whether the signal is coming from an active or from a passive.

Is a short interconnect needed?


Yes, no doubt impedance would take more effect on passive than active pre-amp simply because there isn’t a buffer stage for passive control unit. There are some rules to follow, try to avoid high resistive interconnects such as carbon fiber, try not to use extra-long interconnects. It is always true that the shorter interconnects, the better result, either passive or active. From our experience, we need not worry anything if the interconnect is within 3m length of high quality cables.


If a CD player or power amp already fitted with volume control pot, do we need passive pre-amp?


Passive is never equivalent to a simple volume pot, my advise is to render power amp input volume pot functionless, either fully turn on the volume pot to max level or internally by-pass volume pot terminals. We know by heart that any extra circuitry along signal path would degrade sound quality. It is now a standard for Hi-End gears nowadays do not equip with tone control circuitry for adjusting bass, treble or L/R balance.

If the CD player have variable output to drive directly power amp, do I need a Passive Control Unit?


There are three types of volume controller in CD players, let us elaborate as follows:

Digital volume controller

In theory, this type of volume control is free from noise distortion, problem of L and R channel unbalance from volume pots and noise inherited from carbon type potentiometer are resolved. I can see digital domain volume would be the mainstream in future. Their only shortcoming is higher price to pay. Since the work is done in digital domain, they need high speed DSP with in-house software programming, ending up large research and development cost. Secondly, how well the implementation will determine how much loss of digital bits.

Analogue Domain Volume Controller

This is equivalent to a CD payer plus an active pre-amp housed in a box. Most important of all, the internal set up guarantee shortest signal path and eliminates the needs of extra interconnect. Though they may cost less than individual CD player and pre-amp together in total, but you lose flexibility in CD player up grade.

Analogue Domain with variable output using volume Pot.

This is the worst design of all, it is commonly seen on low price CD player with fancy remote volume pot. My advice is, avoid using variable CD output. If possible, always turn the pot on full volume. The best result is to use Passive Control Unit or active pre-amp at fixed CD output.

How does volume pot affect sound quality?


Some of you may wonder the significant improvement using shunt resistors over the cheap carbon pot. Well, the truth is the shunt type resistive network design are one of the best analogue volume controller because signal path only passes through two resistive elements. Hence, distortion arises from passive element is the least.
But not all the shunt type volume controller sounds the same, the vital parts are how good is the resistive elements, and what value of shunt design should be implemented in one’s system. Try a value of 50K shunt type and compare with the value of 500K, you would find a huge sonic difference.

Has the digital age resulted in the end of the active /passive pre-amp?


I can answer the question in another way, the Stereophile 1998 component of the year belongs to Conrad Johnson’s ART, a pre-amp costs more than a Japanese car. When CD shows its way back in 1981, we thought LP along with tubes would have finished its golden age. Now, what happen is we realized that valve sound can given us so much musical thought and depth, we would see solid state and tubes exist in both worlds and no one can supersede the other.

Is impedance matching the key point of using active pre-amp?


Many will think impedance matching rules the best matching for pre-amp and power amp. No, that is not true. In fact, impedance will not be matched in voltage transfer. By OHM's law, the voltage across a close path is proportional to the impedance across it. That is why the sending end is low impedance (CD out, pre-amp out) while the receiving end (pre-amp in, power amp in) is of high impedance. It is the mis-match in impedance that sends the voltage along the signal path.

To me impedance matching is important. Passive linestage is limited in a sense that it can take low output impedance source & have to feed a high input impedance amp.

My limited knowledge point to a factor of 10 to 1 for properly matching. I.e. output Z 100 to input Z 1000 to output Z 1000 to input Z 10000.

Problem is, quite a number of solid state amps have pretty low input impedance like 1k0 or 20k

Am I even on the right path here ?

Regards,
Joe Ling

it is important but only one of the many factors of equipment matching.

besides, the term "impedance" has been used like a cliche lately.

There is no golden rule about "10 to 1" matching or even a "100 to 1" or "whatever to whatever" matching.

If anyone is REALLY keen to have an in-depth discussion about "impedance". Better blow the dust off that old textbook and get refreshed on something called "imaginary numbers".

Then one realises that "Impedance" in its true sense doesnt really factor into pre/power links but more for amp/speaker combos instead.
And there is really no true "impedance matching" in audio freqs because nothing really matches-up here.

Impedance matching in its true sense would be more for AC signals operating at really high freqs, like video signals or RF signals. Then impedance matching is really critical and can even destroy equipment if mismatched.

Never heard a passive preamp sound good. For me clearly Active.

Kevin

hmmmisthatright wrote:Never heard a passive preamp sound good. For me clearly Active.

Kevin

Don't be so quick to dismiss them.

Have you heard this particular model of passive pre-amp called "Promitheus Audio" in action before?

http://www.promitheusaudio.com/tvc.htm

A friend of mine drives his Cary 300B monoblocks directly from him Kinergetics Research CD player. No preamp. Sounds like a million bucks!

And Wadia is a proponent of eliminating the pre-amp altogether with their digital domain controlled analog outputs since the 8xx series CD players onwards.

I have this Audio Alchemy DDE V3 with an option to upgrade to digital domain analog outputs with remote control. But now that Audio Alchemy has folded, finding that upgrade kit would be tough.

Hey, there's this Doctor dude who makes a pretty neat passive pre in Malaysia. Euphonics research I think. Pretty affordable. Looks like Holfi. You guys remember this?

http://sites.thestar.com.my/audio/story.asp?file=/2005/6/9/audiofile/09euphonic

Try Bent Audio NOH passive