Hi John,
Of course these do not exist, but the interaction of the higher impedance non-buffered version with some input circuits will cause deterioration in S/N and distortion as well. Now you want you look at the magnitude of each. That will depend on the cable, amplifier in question, EMI levels in the area, connectors ... well, you get the idea.
There is no way to say which is going to give you the best results without trying and measuring each time, at different hours of the day and with each component choice. The active version will be much more consistant.
Then, depending on the equipment involved, even if the passive version did deliver lower distortion, could you hear it? Depending on your desire to hear one as better would carry more weight that documented proof.
-Chris
Of course these do not exist, but the interaction of the higher impedance non-buffered version with some input circuits will cause deterioration in S/N and distortion as well. Now you want you look at the magnitude of each. That will depend on the cable, amplifier in question, EMI levels in the area, connectors ... well, you get the idea.
There is no way to say which is going to give you the best results without trying and measuring each time, at different hours of the day and with each component choice. The active version will be much more consistant.
Then, depending on the equipment involved, even if the passive version did deliver lower distortion, could you hear it? Depending on your desire to hear one as better would carry more weight that documented proof.
-Chris
Although it's true that most corporations are only in it for the money, many small businesses are started by people that have a product they believe is a good or valuable idea.
This is very true for small audiophile companies who go out of business in droves. Your view of business is through a very narrow perspective. Many of the companies I used as examples of passive pre-amps are tiny. They’re certainly not opposed to making money but that’s unlikely the sole reason they chose this line of work.
Sometimes people make things because it is a passion. Don’t compare an oil company giant to a little shop on Catalina Island off the coast of California, they are not the same.
Passive pre-amplifiers are not for every situation, but they work and work very well in almost all cases. You keep confusing personal preferences with electronic absolutes. You are welcome to believe that an active stage is always superior, just don’t claim that real world constraints demand active as the only acceptable solution. That is nonsense.
I have been designing op-amp circuits since the old 748 was introduced by Fairchild Semiconductor in the late 60’s. I happen to believe that discrete transistor designs are superior but I don’t tell people that alternatives can not be made to work and should not be pursued. With sufficient effort even op-amps can be useful although many op-amps sound like complete crap.
One reason I am passionate about passive pre-amps is that commercial active pre-amps that sound as good as the better passive units start at $5,000 and go way up from there and fast. I can not afford a Conrad Johnson ART pre-amp ($16,000 I think) but I’ll hold the sound quality of my homebrew against one any day of the week (Yes, I’ve heard the C-J and many others). By using Vishay S102 resistors (at $11.50 each) and a solid silver switch coupled with 5 nines specially annealed silver wire and pricy Cardas connectors I have achieved a level of sound quality that no op-amp I ever heard can equal. It is this sound quality that warrants the small risks associated with the short comings of a passive pre-amp.
So let’s recap: Sources generally have low source impedance, loads generally have a high input impedance, you can capitalize on the difference between these two impedances to make a passive gain control. It works, really, many have done it.
PS: With regard to measurements; no active stage will ever measure better distortion than a passive stage. The active stage requires the passive parts plus a non-linear active device. The passive will win the noise contest unless special environments are introduced. Poorly designed op-amps or power supplies will easily out noise the passive design and even very good designs will have a tough time being equal much less better. The passive will never have shot noise or intermodulation distortion and the noise floor is really equal to the Kelvin noise which is about 120 db below 1 VRMS for a 10K impedance.
This is very true for small audiophile companies who go out of business in droves. Your view of business is through a very narrow perspective. Many of the companies I used as examples of passive pre-amps are tiny. They’re certainly not opposed to making money but that’s unlikely the sole reason they chose this line of work.
Sometimes people make things because it is a passion. Don’t compare an oil company giant to a little shop on Catalina Island off the coast of California, they are not the same.
Passive pre-amplifiers are not for every situation, but they work and work very well in almost all cases. You keep confusing personal preferences with electronic absolutes. You are welcome to believe that an active stage is always superior, just don’t claim that real world constraints demand active as the only acceptable solution. That is nonsense.
I have been designing op-amp circuits since the old 748 was introduced by Fairchild Semiconductor in the late 60’s. I happen to believe that discrete transistor designs are superior but I don’t tell people that alternatives can not be made to work and should not be pursued. With sufficient effort even op-amps can be useful although many op-amps sound like complete crap.
One reason I am passionate about passive pre-amps is that commercial active pre-amps that sound as good as the better passive units start at $5,000 and go way up from there and fast. I can not afford a Conrad Johnson ART pre-amp ($16,000 I think) but I’ll hold the sound quality of my homebrew against one any day of the week (Yes, I’ve heard the C-J and many others). By using Vishay S102 resistors (at $11.50 each) and a solid silver switch coupled with 5 nines specially annealed silver wire and pricy Cardas connectors I have achieved a level of sound quality that no op-amp I ever heard can equal. It is this sound quality that warrants the small risks associated with the short comings of a passive pre-amp.
So let’s recap: Sources generally have low source impedance, loads generally have a high input impedance, you can capitalize on the difference between these two impedances to make a passive gain control. It works, really, many have done it.
PS: With regard to measurements; no active stage will ever measure better distortion than a passive stage. The active stage requires the passive parts plus a non-linear active device. The passive will win the noise contest unless special environments are introduced. Poorly designed op-amps or power supplies will easily out noise the passive design and even very good designs will have a tough time being equal much less better. The passive will never have shot noise or intermodulation distortion and the noise floor is really equal to the Kelvin noise which is about 120 db below 1 VRMS for a 10K impedance.
An active pre can be very transparent, and there's one thing that is really on another league compared to passive: dynamics, scale, soundstage.
You may not have the money to buy one of those expensive active preamps (I also don't), but you can build one.
PS: don't presume that most sources are low impedance.
CDPs with 1k+ output (series) impedance (yes!!!) are very common.
Of course, the solution is in most cases very simple.
You may not have the money to buy one of those expensive active preamps (I also don't), but you can build one.
PS: don't presume that most sources are low impedance.
CDPs with 1k+ output (series) impedance (yes!!!) are very common.
Of course, the solution is in most cases very simple.
Bgt said:
Well then, we now would be discussing what active stage(s), what pot(s), and this would give an endless discussion.
In some situations a passive solution gives very good results, as I said before.
But a good active stage works better for me, in most situations.
It's not only the source, you need to know what's inside the power amp, if there's an input buffer the pot will work fine.
Then what about if you bypass that nasty (very common) input buffer and use a good active pre? Big improvement, most of the times.
Without knowing the insides you can't decide what's best for your system.
What you should not do is to cascade unnecessary active stages.
On that we agree.
Hi Hermanv,
And many fall short in the basics, as history has shown. Many can not support their claims. Most are started by hobbyists who are not well enough versed in circuit design. I've spent my life repairing these. I am not at all narrow minded as some of you know.
I have used and built both types. I am lucky enough to have heard very transparent (and quiet) active pre amps. Whether some of you agree or not is fine. I am very objective, but see every fad and misapplication possible. The best ones are discreet that I've seen.
Your comment about distortion is completely unfounded. You are looking at it in isolation away from the inevitable interactions with some input circuits. There are times you need some current, not directly related to input resistance. As far as noise is concerned, that's a very dangerous viewpoint. All I said was that you have a reasonably high impedance source driving a cable. There is a reason why we don't run turntable leads very far, and your low levels for good S/N run about the same magnitude. The solution is - use a buffer at the turntable. A similar case will hold true. This depends on how much electrical noise there is about.
I really have tried to qualify my comments. Someone starting out will not have the extreme high end equipment, and so a passive preamp is an unlikely choice for quality sound in this case.
I also have been involved in the industry a long time. Service since the Seventies professionally. I routinely service and restore equipment from the Twenties up to current under warranty product. From small companies that have good ideas. Some are still even in business. No, I'm not even close to the likes of people like Nelson Pass, John Curl and many others, but I'd like to think I've learned a couple things over the years. Most important. You must consider the entire system. If something is unknown, design for the most reasonable worst case. An engineer would agree with this I think.
-Chris
And many fall short in the basics, as history has shown. Many can not support their claims. Most are started by hobbyists who are not well enough versed in circuit design. I've spent my life repairing these. I am not at all narrow minded as some of you know.
I have used and built both types. I am lucky enough to have heard very transparent (and quiet) active pre amps. Whether some of you agree or not is fine. I am very objective, but see every fad and misapplication possible. The best ones are discreet that I've seen.
Your comment about distortion is completely unfounded. You are looking at it in isolation away from the inevitable interactions with some input circuits. There are times you need some current, not directly related to input resistance. As far as noise is concerned, that's a very dangerous viewpoint. All I said was that you have a reasonably high impedance source driving a cable. There is a reason why we don't run turntable leads very far, and your low levels for good S/N run about the same magnitude. The solution is - use a buffer at the turntable. A similar case will hold true. This depends on how much electrical noise there is about.
I really have tried to qualify my comments. Someone starting out will not have the extreme high end equipment, and so a passive preamp is an unlikely choice for quality sound in this case.
I also have been involved in the industry a long time. Service since the Seventies professionally. I routinely service and restore equipment from the Twenties up to current under warranty product. From small companies that have good ideas. Some are still even in business. No, I'm not even close to the likes of people like Nelson Pass, John Curl and many others, but I'd like to think I've learned a couple things over the years. Most important. You must consider the entire system. If something is unknown, design for the most reasonable worst case. An engineer would agree with this I think.
-Chris
Without opening commercial products for which many of us paid big bucks, the well made passive pre offers exceptional bang for the buck.
I have never heard limits to sound stage or dynamics from my passive, I've read other posts where the owners thought this was because of the Vishay resistors. I can neither support or deny this.
I am hard pressed to understand why a resistor in a passive pre would limit dynamics but that same resistor in an active stage suddenly does not. I am not saying it ain't so, but it does come awfully close to huh?
I have never heard limits to sound stage or dynamics from my passive, I've read other posts where the owners thought this was because of the Vishay resistors. I can neither support or deny this.
I am hard pressed to understand why a resistor in a passive pre would limit dynamics but that same resistor in an active stage suddenly does not. I am not saying it ain't so, but it does come awfully close to huh?
Hi Hermanv,
I don't know for sure either.
A couple of ideas on this. Output impedance of the source is too high. The output stage will not sound too dynamic. I depends on how it was rated (specs). You may not get what you would expect.
Input non linearity. Some amplifier (or preamp) stages seem to require a "low" impedance source to drive them properly. It seems that a higher impedance shows up these problems. I have heard the difference myself. Test: Put a resistor in series with an active preamp and troublesome amp. As the resistance goes up there will be very little drop in level before it doesn't sound good anymore. This does not happen with most tube amplifiers (hence my comment earlier).
Just a couple thoughts.
-Chris
I don't know for sure either.
A couple of ideas on this. Output impedance of the source is too high. The output stage will not sound too dynamic. I depends on how it was rated (specs). You may not get what you would expect.
Input non linearity. Some amplifier (or preamp) stages seem to require a "low" impedance source to drive them properly. It seems that a higher impedance shows up these problems. I have heard the difference myself. Test: Put a resistor in series with an active preamp and troublesome amp. As the resistance goes up there will be very little drop in level before it doesn't sound good anymore. This does not happen with most tube amplifiers (hence my comment earlier).
Just a couple thoughts.
-Chris
You are starting to grasp at straws, if there is some kind of magic, undefined and unknown interaction you can not rule out that this same interaction will not happen with an active unit.
Turntable signals are in the humdreds of microvolts to 5 millivolt range. Large gains are required as well as extensive frequency shaping to amplify them. This just has nothing to do with discussions about passive pre-amps operating at 2 VRMS.
This site is not only for those just starting out, but that is irrelevant. It will be a rare case where the passive encounters the problems you imply are legion, it is just not so.
As a repair person is it possible that you only see the worst equipment because the good stuff never makes it to your lab leading you to conclude that all equipment is equaly represented by your work samples?
I am an electronic engineer, I think it's kind of clear I don't agree.
Hi Hermanv,
Groan. What are the levels at the input to the amplifier for the finer details? That's my point. You are looking at the wrong end of the gun.
I am not looking at "magic", or grasping at straws. I merely stated that the reason for the effect was unknown to me. I was brave enough to report it honestly. Others have noticed this effect as well. I did give you a test you could try yourself. With your hearing acumen, you should be able to hear this easily.
Yeah I work on junk. Conrad Johnson, Nakamichi, Marantz, McIntosh .. on and on. Oh yeah, it's new. I modify units to solve problems that escape the lab - while talking to the design engineers. Yup, we're working together. Shocking to you I'm sure. I solve basic engineering errors that were created by engineers. Not true but I'll say it. Engineers design the stuff, technicians make it work.
I didn't ask you to agree with me, I know some that do. That's enough for me. I think that you should do some experimenting.
-Chris
Groan. What are the levels at the input to the amplifier for the finer details? That's my point. You are looking at the wrong end of the gun.
I am not looking at "magic", or grasping at straws. I merely stated that the reason for the effect was unknown to me. I was brave enough to report it honestly. Others have noticed this effect as well. I did give you a test you could try yourself. With your hearing acumen, you should be able to hear this easily.
Yeah I work on junk. Conrad Johnson, Nakamichi, Marantz, McIntosh .. on and on. Oh yeah, it's new. I modify units to solve problems that escape the lab - while talking to the design engineers. Yup, we're working together. Shocking to you I'm sure. I solve basic engineering errors that were created by engineers. Not true but I'll say it. Engineers design the stuff, technicians make it work.
I didn't ask you to agree with me, I know some that do. That's enough for me. I think that you should do some experimenting.
-Chris
I did not mean to get personal, a passion for musical truth is good.
I have done many experiments and find that my conclusions dissagree with yours. I know the math allows one to fall near the middle ground of the discusion but I haven't heard a passive have problems like the ones you are concerned about. Have I heard all possible passives in all possible circuits, of course not.
I like short cables, because I think they sound better and since I like good cables they cost less too.
I worry about grounds so my equipment collection might be more immune to problems with passives, but the grounding I use is not extreme or weird just common sense. I have taken my passive to other's homes where they too marvelled at what was possible and set about "fixing" what was wrong with their pre-amplifier chain.
The passive may not be for everyone, but I encourage a trial in your personal system because you will be hard pressed to find a solution at any price that beats this nice simple idea. So I will repeat myself: I have heard nothing at any price that outperforms a well made passive pre (and no, I don't sell them or work for anyone who does). And even though I accept that there might be problems in some systems I personally have never heard these problems.
I have done many experiments and find that my conclusions dissagree with yours. I know the math allows one to fall near the middle ground of the discusion but I haven't heard a passive have problems like the ones you are concerned about. Have I heard all possible passives in all possible circuits, of course not.
I like short cables, because I think they sound better and since I like good cables they cost less too.
I worry about grounds so my equipment collection might be more immune to problems with passives, but the grounding I use is not extreme or weird just common sense. I have taken my passive to other's homes where they too marvelled at what was possible and set about "fixing" what was wrong with their pre-amplifier chain.
The passive may not be for everyone, but I encourage a trial in your personal system because you will be hard pressed to find a solution at any price that beats this nice simple idea. So I will repeat myself: I have heard nothing at any price that outperforms a well made passive pre (and no, I don't sell them or work for anyone who does). And even though I accept that there might be problems in some systems I personally have never heard these problems.
hermanv said:
Are you afraid to open it?
Don't be, you don't know how huge improvements you can make inside, incompetence is everywhere, at every price.
I once opened an integrated Krell.
It was more the parts that I removed than the ones I changed inside.
Input buffer stage=out, next: electrolythic DC coupling caps = out, dac volume control (let it be), electrolythic DC coupling caps (again!!!) = out, OPA2604 op-amps = changed.
Input of power amp: electrolythic DC coupling caps (!!!!) = changed for better ones.
PSU, etc, etc, etc...
Yes, the deam Krell sounded very bad to me in original form (I don't understand the hype), and hey, it was a 6000 Euro amp!
I just made a service to an unhappy friend, he loves the amp now. Not because it's pretty or because it's a Krell. It's because it sounds good.
But a modded Pioneer A400 also sounds good.
Hi Hermanv,
Fair enough. I have tried this.
I have tried some passives with varying results depending on the amplifier. Generally, I find they work best with tube or J-fet based first stages. Some bipolar diff pair type amps will not sound as good without a higher drive current.
If you get a chance, have a listen to a Nakamichi PA-7. They are quiet. Another preamp you may want to listen to is a Marantz SC-9. I am sure there are others.
Funny story. Nakamichi came out with "HTA" series amplifiers. New technology they said. The Marantz 500 used it years earlier. It was simply a class A buffer in front of a bipolar differential pair.
-Chris
Fair enough. I have tried this.
I have tried some passives with varying results depending on the amplifier. Generally, I find they work best with tube or J-fet based first stages. Some bipolar diff pair type amps will not sound as good without a higher drive current.
If you get a chance, have a listen to a Nakamichi PA-7. They are quiet. Another preamp you may want to listen to is a Marantz SC-9. I am sure there are others.
Funny story. Nakamichi came out with "HTA" series amplifiers. New technology they said. The Marantz 500 used it years earlier. It was simply a class A buffer in front of a bipolar differential pair.
-Chris
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