[Jon L]

This is pretty close:

Hmm, the new Madisound price of $123 on the 10 uF Claritycap MR is not as bad as I suspected 

I've heard both ways, but do you find your B-1 with premium caps to have the "dynamics" that active-preamp-lovers are espousing?

[roymail]

The perception of less dynamics with a passive was not the case with my setup.

It's not my experience, either.  Good point, konut.

I have found that most actives exaggerate dynamics. Most people like this kind of presentation.  With the sorry state of most recorded music, with limited dynamics, this is completely understandable.

I agree again, and I'll add one more.  Many listeners prefer a colored sound.

I always thought the goal was to achieve the same sound you'd get with no preamp at all, an amp with a volume control.  However, that's not the sound that many prefer.  But, I find that sound to be the best for me... spacious, transparent, revealing, honest, refined, non-fatiguing, beautiful sonics.

I'm not saying you can't get "beautiful sonics" any other way... you can!  As they say, pay your money and take your chances.

[avahifi]

I will repeat myself again on this subject.

A passive preamplifier actually is not a preamplifier at all, inasmuch as it does not amplify.  Well - there are some that use some kind of step up transformers, but that is another can of worms.

Essentially a passive preamp is a volume control in a box with some switching functions.

The advantage musically is that it eliminates all active preamp circuit functions, and if the active preamp circuits are not of very high quality they deserve to be eliminated.

The disadvantage musically is that is eliminates all active preamp circuit functions.  Those functions should be designed to provide a easy pure resistive load for the sources to drive, eliminate out of band garbage, drive the sh--- out of all downstream loads no matter how goofy they are, and not screw up in and of themselves.  Lots of designers drop the ball here.

A passive preamp essentially connects your sources directly to the power amp, through the likely significant amount of distributed capacitance of the cables between the source and the passive preamp, its internal load, the distributed capacitance of the cables between the passive preamp and the power amp, and the internal distributed capacitance of the amplifier's input circuits.  Whew!!!  If you wonder what a capacitive load does to the music signal, see all the test results done over the years showing this, they cause a leading edge spike and ringing on the signal, the bigger the load the worse the results.  In addition now that load makes demands on the drive current capability of the source that it likely does not have.

So with a passive preamp you have the distortion of the additional capacitive load on the source, and from taxing its drive current capability.  With an active preamp, you have the distortion of the preamp's active circuits themselves.

Which is worse?  It depends on the quality of the preamp active circuits, the load driving capacity of the source, and the amount of distributed capacitance of the cables.  Your results may vary.   

In general we would suggest short, low capacitance well shielded interconnect cables, sources with excellent current drive capability (a spec not usually talked about) an amplifier with a pure resistive input impedance, and a very very low distortion active preamp line stage providing a resistive input load and high output drive current.

Hope this has not confused you too much.

Frank Van Alstine

[TomW16]

I believe that passive preamps can be part of highly resolving system but as others have already pointed out there are factors that have to be met to make them feasible:

A strong enough signal from the source.
Low output impedance from the source.
High input impedance from the amp.
Short lengths of low capacitance cables

If you respect all of these variables you can put together a VERY resolving system around a passive preamp that does not lack dynamics.

Most consumers don't know or don't want to spend the time looking at the requirements so manufactures provide active circuitry to ensure that the equipment is universal and will play with almost all other manufactures' equipment.  But for those willing to do their homework, passives can be a very viable alternative.

Tom

P.S.  Great, I had to follow Frank with this post 

[konut]

Frank Van Alstine is correct on every point. It is SO much more critical to match the driving output stage, cable electrical properties, and amplifier input stage for successful system integration when implementing passive attenuation and switching. For example, my main driving output stage is a Bryston BDA-1 DAC with a class A, 2.3V output at 50 ohms. 2ft of low inductance ICs to a Creek OBH-12 resistor based passive, split, to a Marchand XM46 high pass filter and sub, then 4' low inductance ICs to monoblock W4S SX-500 amps with an input impedance of 60.4kΩ.
      It is very rare indeed to get lucky with random component selection for passive systems. Active systems, by contrast, are relatively simple to implement successfully.

[roymail]

A passive preamplifier actually is not a preamplifier at all, inasmuch as it does not amplify.

I prefer the term passive attenuator or passive volume control.  I think the term passive preamplifier simply means that the passive device is after the source and before the amplifier, hence, pre-amplifier.

Reviewing all the posts in the thread indicates to me that most have a pretty good understanding of the differences between active and passive volume controls along with their advantages and disadvantages.

[Steve]

I prefer the term passive attenuator or passive volume control.  I think the term passive preamplifier simply means that the passive device is after the source and before the amplifier, hence, pre-amplifier.

Reviewing all the posts in the thread indicates to me that most have a pretty good understanding of the differences between active and passive volume controls along with their advantages and disadvantages.

Another problem one encounters is that the preamplifier active circuitry can usually be designed much better than either the circuitry in the amplifier or the analog stages in the DAC/CD player. Of course there are many distorted/colored sounding active preamplifiers out there that are worse. There are also distorted/colored sounding passive preamplifiers as well.

But if one wants the most accurate/musical sound, then I would suggest going with a superior active preamplifier and eliminate the poor analog stage in the DAC/CD player if possible. And if possible go for a basic amplifier and eliminate the first stage in an integrated amplifier. That way one eliminates two stages of amplification, the DAC/CD analog stage, and the first stage in an integrated amplifier, producing better overall fidelity when matched.

Cheers.

[turkey]

Another problem one encounters is that the preamplifier active circuitry can usually be designed much better than either the circuitry in the amplifier or the analog stages in the DAC/CD player.

Why would this be so?

But if one wants the most accurate/musical sound, then I would suggest going with a superior active preamplifier and eliminate the poor analog stage in the DAC/CD player if possible. And if possible go for a basic amplifier and eliminate the first stage in an integrated amplifier. That way one eliminates two stages of amplification, the DAC/CD analog stage, and the first stage in an integrated amplifier, producing better overall fidelity when matched.

I would think you'd want to improve the output stage of the DAC/CD player so that it can drive the patch cords, wiring, volume pot, etc. in the preamp properly. Then you have a good line stage, and finally a good amp. (Or you could just use a good integrated amp, but you'd still want a good output stage in your DAC/CD player.)

[Steve]

Another problem one encounters is that the preamplifier active circuitry can usually be designed much better than either the circuitry in the amplifier or the analog stages in the DAC/CD player.

Why would this be so?

For a couple of reasons right off hand. First, there is more room for a proper design for total transparency and accuracy. Designing the best, transparent  preamplifier is extremely difficult and takes physical space. Heat may also be a consideration if tube designs are used.

Secondly, eliminating stages lessens/minimizes frequency dependent feedback from stage to stage through the power supply. Not only is the feedback frequency dependent, but also phase shifts occur as well, even into the midrange.

The result is more lifelike music, minimizing distortions.

But if one wants the most accurate/musical sound, then I would suggest going with a superior active preamplifier and eliminate the poor analog stage in the DAC/CD player if possible. And if possible go for a basic amplifier and eliminate the first stage in an integrated amplifier. That way one eliminates two stages of amplification, the DAC/CD analog stage, and the first stage in an integrated amplifier, producing better overall fidelity when matched.

I would think you'd want to improve the output stage of the DAC/CD player so that it can drive the patch cords, wiring, volume pot, etc. in the preamp properly. Then you have a good line stage, and finally a good amp. (Or you could just use a good integrated amp, but you'd still want a good output stage in your DAC/CD player.)

The DAC chip analog output has very very low output Z and is quite capable of easily driving an IC etc. With the DAC/CD player's analog stage gain of only a meager two (approx 1 volt output from the DAC chip), why not let a great active preamplifier do the work of two components, the DAC/CD analog stage and the active preamplifier. In fact, there may be enough gain to possibly eliminate the extra gainstage in the amplifier. Depends upon the gain of the intergrated's first stage.

It is more expensive to use a world class active preamplifier, but eliminating one or two cheap analog stages is worth it imo.


Cheers.

[Niteshade]

The best way to look at passives and actives is as tools. Saying that one is always better than the other is completely impossible.

A parallel question: When does one use a passive or an active amplifier control?

There is no reason to debate which one is better. It's 100% application specific.

Does anyone know the advantages and disadvantages of using these two type of preamp? How would they differen sonically?

Thanks

[Letitroll98]

One then performs sophisticated long term special listening tests to determine the transparency (say of the preamplifier) in absolute terms and make adjustments. Virtually no one does all this because it is so difficult, although superior.

A little off topic, sorry, but refreshing to be on a site where the engineers use listening as the final judge. 

Back on topic, as noted by Niteshade in the previous post these are tools to get to an end, great sound.  I could care less if my preamp is passive or active, I want the purest, most neutral presentation.  My system is an example in that although I like passive preamplification, I'm pushing the technical limits to make it viable.  If I use a lowish output cartridge with the lower gain setting on the phono pre, I'm forced into using the active side of the preamp.  But with the CDP, the pseudo passive side of the PS Audio is much preferred.  All just means to an end.   

[mcgsxr]

I cannot imagine a more synergy dependent piece than the preamp.

I actually don't use ANY anymore - I used to use one, but have gone to directly feeding my tube amp with my modded SB3.

[Steve]

A little off topic, sorry, but refreshing to be on a site where the engineers use listening as the final judge.

I could care less if my preamp is passive or active, I want the purest, most neutral presentation. 

Thanks Letitroll. 
True, it is difficult to find the most neutral and pure. However, for our information, we do know that certain things do limit the quality of a system.

1) Frequency dependent musical feedback, with varying phase shifts, through the power supply. This can occur in either multiple stage preamplifiers or amplifiers. The amount and phase problems concerning feedback, either positive or negative feedback, is dependent upon the number of stages, power supply isolation between stages etc. with a common power supply.

2) DAC/CD player analog stages (after the DAC chip) adversely affect system quality. Maybe some DAC designers would offer outputs directly from their DAC chips. If not one just does the best one can.

Having these two problems guarantee the system is not optimum/accurate as it could be.

MCG, the preamplifier gainstage has simply been installed in the amplifier, or CD player. Good to see you did not overgain your system. 

Cheers.

[Letitroll98]

I agree Steve, or at least people I trust agree as I'm not an EE and don't really know much about circuit design.  My engineer friend from that vinyl site that shall forever go unmentioned in my posts is very concerned with frequency dependent distortions in amplifiers.  I understand the arguments only in a general way so won't try to repeat them here, but they are close to what you are noting, prolly the same.  And all the DIY guys are modding the heck out of my DAC's (the Beresford unit) output stages, so they must be on to something.  Personally I solve problem #2 with the judicious use of a VPI turntable.  For some strange reason it seems to solve all of my digital non-linearities.      

[mcgsxr]

Steve you are correct, the actual pre is a part of the digital player I use.   I had previously used DAC, tubed pre etc, but went with a simple, single source system.

[Steve]

Steve you are correct, the actual pre is a part of the digital player I use.   I had previously used DAC, tubed pre etc, but went with a simple, single source system.

Thanks Gentlemen, and good to see others who are seeing/addressing these problems. The old texts I have studied (i.e. RCA Radiotron Designers Handbook, 1960.) address frequency dependent feedback and other problems.
I think the more we can address the weaknesses in designs, the better off we are. 

Have a great weekend Gents.

[konut]

It is absolutely critical that the analog gain stages be as transparent as possible. Any CD, DVD, or Blu-Ray player, not costing many thousands of $, is going to have a less that stellar analog output that will just pollute the signal throughout the signal chain from then on. I attribute the dissatisfaction of digital formats to this cause. A DAC that addresses the analog signal handling well, isolation from the digital supply, ground plane management, low output impedance, and high gain, will deliver superior performance from any digital source, and will deliver a clean signal to the subsequent gain stages from then on. This is especially important when going passive. 

[Construct]

It is absolutely critical that the analog gain stages be as transparent as possible. Any CD, DVD, or Blu-Ray player, not costing many thousands of $, is going to have a less that stellar analog output that will just pollute the signal throughout the signal chain from then on. I attribute the dissatisfaction of digital formats to this cause. A DAC that addresses the analog signal handling well, isolation from the digital supply, ground plane management, low output impedance, and high gain, will deliver superior performance from any digital source, and will deliver a clean signal to the subsequent gain stages from then on. This is especially important when going passive.

That is absolutely my experience.  Too much emphasis is placed on the power amp.  I have found that a modest, yet sufficiently powerful amp will be elevated more by a quality preamp than attempting to use the best amp with a mediocre preamp.  I could use a passlabs preamp and an adcom power amp to achieve better results than a passlabs x-series amp and a $350 emotiva preamp.

[roymail]

It is absolutely critical that the analog gain stages be as transparent as possible. Any CD, DVD, or Blu-Ray player, not costing many thousands of $, is going to have a less that stellar analog output that will just pollute the signal throughout the signal chain from then on. I attribute the dissatisfaction of digital formats to this cause. A DAC that addresses the analog signal handling well, isolation from the digital supply, ground plane management, low output impedance, and high gain, will deliver superior performance from any digital source, and will deliver a clean signal to the subsequent gain stages from then on. This is especially important when going passive.

Agreed... which is why I have a nicely modded CDP with very transparent output. 

[daniloreyes]

But isn't $123 a bit excessive for a B1 cap?

wow..

By the way how it sounds?