Silly question about passive preamps

[nightflier]

OK, I've seen several passive preamps that have remotes. But if they are passive, how do they control the volume (or switch inputs)? Doesn't that require more power than what is being gleaned from the inputs?

[markw]

When they say "passive", they are refering to any elecrtrical intrusions in, or alterations in the signal path. i.e., no amplification, tone controls, etc.

You can have a motor on a potentiometer to turn it up or down and a solenoid to switch the inputs without affecting the signal path itself.

Now, if someone is offering a digital passive preamp, run, run away as quickly as you can. ;)

[nightflier]

Mark,

With all the tweaks available (brass spikes, chassis damping, wood blocks, etc.) that people say affects the sound, I have to believe that even a very simple motor to drive the volume would be equally audible.

[Feanor]

Mark,

With all the tweaks available (brass spikes, chassis damping, wood blocks, etc.) that people say affects the sound, I have to believe that even a very simple motor to drive the volume would be equally audible.

'flier, people "believe" that all that other crap is audible and no doubt they believe the motor is too. Maybe so in some instances.

Actually for a while I used an Adcom GFP-750 in passive mode. It that had the motor and selenoid; it didn't operate without powering on, so I could never tell for certain whether these things had any effect on the sound.

[markw]

Mark,

With all the tweaks available (brass spikes, chassis damping, wood blocks, etc.) that people say affects the sound, I have to believe that even a very simple motor to drive the volume would be equally audible.Now you delve into the realm of belief and those "some say" people would be well advised to avoid any automation in their preamps entirely as a matter of principle. What they will have is an expensive input selector and volume control.

But, if one wants the conveniences of remote control, they're gonna have to cave on their "no electricity anywhere" principles. Unless, of course, they are in Hogwart's Acadamy.

[Glen B]

I don't know why the high end community has continued to call these devices passive "preamps" ? They don't amplify anything. They are attenuators and should be called passive attenuators or something like that but certainly not "preamps."

[nightflier]

'flier, people "believe" that all that other crap is audible and no doubt they believe the motor is too. Maybe so in some instances. Actually for a while I used an Adcom GFP-750 in passive mode. It that had the motor and selenoid; it didn't operate without powering on, so I could never tell for certain whether these things had any effect on the sound.

This preamp is a case in point. It's supposed to be passive (when activated), but it still requires power to operate. So the question really becomes whether it is really operating in passive mode. I've been following this preamp for some time, and I almost bought one off A-gon not too long ago. It seems to be the best value out there, but is it really a passive preamp?

Regarding the tweaks, I don't think it's all beliefs, especially with components like CD players and TT's that have spinning parts. But even preamps and amps are surrounded by electro-magnetic fields as well as things in the physical environment that affect the sound - even the way a cable is putting stress on a jack can be audible. The best way to discover this is to run the component at high volume with nothing playing. Different tweaks (such as sorbotane feet) will have audible effects. Now whether they are heard when music is playing, is another matter, but then there are also very silent passages in music - the pause between two movements in a live recording when you hear someone in the audience caughing, for example. Now a low murmur from an inadequately damped CD player would be annoying, and whether the sound is real or imagined during the louder passages, the existence of it becomes grating.

You know, I really need to get my hands on that Adcom GFP-750. I want to see how it compares to my active amps.

[Glen B]

Mark,I have to believe that even a very simple motor to drive the volume would be equally audible.

Why would it be ? The motor is only turning the shaft of the potentiometer and is not in the audio signal path. The motor would only be operational during the few moments that one is changing volume.

[Feanor]

This preamp is a case in point. It's supposed to be passive (when activated), but it still requires power to operate. So the question really becomes whether it is really operating in passive mode. I've been following this preamp for some time, and I almost bought one off A-gon not too long ago. It seems to be the best value out there, but is it really a passive preamp?
....
You know, I really need to get my hands on that Adcom GFP-750. I want to see how it compares to my active amps.

Yep, it really is passive in the sense that in that mode there is not amplification of the signal. If I'm not mistaken power is required to control the source selector which is digital. I liked the unit in passive mode alot; I did find is quite bright in active mode however. The main reason I switch to my present SF LINE 1 was (a) to get true balanced output, and (b) just to try tubes which I'd never done before.

As for balance output, in passive mode the 750 is not balanced unless the source is balanced; in active mode, it is balance regardless.

[markw]

Regarding the tweaks, I don't think it's all beliefs, especially with components like CD players and TT's that have spinning parts.I'll take more stock in your beliefs when I see some "passive" CD players, passive TT's (not wind-up victrolas) and passive tuners (not Xtal AM radios) making headway in the real world. In the meantime, I see a lot of this audiophoolery as being analagous (pun intended) to arguing over how many angels can dance on the head of a pin.

[nightflier]

I'll take more stock in your beliefs when I see some "passive" CD players, passive TT's (not wind-up victrolas) and passive tuners (not Xtal AM radios) making headway in the real world. In the meantime, I see a lot of this audiophoolery as being analagous (pun intended) to arguing over how many angels can dance on the head of a pin.

As I was writing my last post, I was thinking that I shouldn't mention TTs and CDPs because someone is going to ask me to name a passive one and well, you're right, there aren't any. But I think you're also confusing the topic of passive preamps and tweaks. Many tweaks do work, and whether they work on passive preamps should be addressed separately.

This is a lot of like testing video components when displaying a test pattern - it's not what this equipment is typically used for, but it sheds some light on the effect of different tweaks. Changing out different ICs and power cables for example, does change the test pattern on the screen. I can't really say that they make audible differences, but I'm going to presume that audibility could also be measured with sensitive computer equipment. While I was testing this out, I also discovered that the quality of connection of the IC to the jack is also visible on the test pattern. I suppose that this follows the same logic that jiggling the cable is clearly visible. So the cables that looked best on the screen also had tighter connectivity. But that's just cables, you might say. OK, I'll continue.

On to those squishy feet - and I'll stick to my experiences with my preamps. Can I hear a difference when I'm listening to music? Not really, but when the volume is at 12 o'clock and nothing is playing? Yup. Now I've also tried the wooden blocks (both my own home-made ones and a borrowed pair of overpriced Cardas ones) and they made no difference. Neither did those fancy brass feet from Mapleshade - which really disappointed me, because they should have, and I wanted them to, after all they were expensive. So I can't really explain why the sorbotane feet made a slight difference, but they did.

I can also say with confidence that decent power conditioning makes a difference both on the test pattern and ever so slightly in the sound department. I'm partial to PS Audio, here, but any brand has worked similarly in my tests, and not just the uber-expensive ones. It makes the biggest difference in video cables, of course, probably eliminating electro-magnetic interference. I should mention that I have yet to find a power cable at any price that has made any difference, as long as it is shielded. I buy the cheapest PS Audio cables and they show me no difference from any other higher-priced one. But, hey' that's my experience.

Speakers are a whole other topic where cables, connectors, spikes, and that blue play-do looking stuff all can make a tiny difference. It certainly isn't the night-and-day, relisten-to-my-whole-collection, my-god-I've-been-born-again, call-the-president, kind of revelation that the sales reps and the paid-for reviewers like to claim. But all these tweaks do make slight differences that together make for a better sounding speaker. And we haven't even started to talk about room treatments. But that's speakers, and they are in a category of their own, so we'll ignore those "tweaks".

And to be fair, there's a lot of things I've tried that have had no effect that I can tell. Cable risers? No effect. Funky magnets around the room? No effect. Fancy solvents to clean connectors? Simple OTC products from the hardware store work just as good. Little green marks on the CDs? Yeah right. CD demagnitizers? Hah! That Gryphon cable zapper thingy? No effect (I actually sold that at twice what I paid for to some sucker who swears by it - good for him). So I can agree that there are some things that may be snake-oil, others that my ears and eyes can't make out, and some that require fancier gear. Fine. But to categorically say that tweaks don't work, that may be a bit much.

So let's get back to passive preamps. Well I'm no engineer, but I'm going to guess that a small power source inside of a dead-silent passive preamp could, maybe, have just enough of an electro-magnetic field that some people out there with golden ears and the fanciest gear could hear it. Consider for example that the pull of an IC's weight can affect the quality of the connection and can be audible (I have heard this). Or that a slight rumble from a more noisy component could be transmitted to the preamp. Or that the tubes in a tube preamp can be noisy. Or that the cleanlyness of the strike plate that the volume control rubs against could be audible? Isn't it fathomable that during a particularly quiet musical passage, perhaps, just maybe, on a cold Wednesday afternoon in mid-winter, when everything is dead quiet in the house, not a creature is stirring... well you get the point.

If you consider, for example, how much research hi-fi companies put into designing quiet volume controls. I'm reminded of the work that Paul McGowan at PS Audio put into designing his volume controls and how it was so important for these to be quiet and durable. I've got to believe that a good passive preamp should be completely passive, and be able to function without requiring power. Of course, that makes a remote pretty much impossible. I stated a thread a while back on digital volume controls, but after researching that, I came to the conclusion that they too have their share of engineering obstacles, and of course, they require power.

So I guess there really can't be such a thing as a passive preamp that has a remote.

[markw]

So I guess there really can't be such a thing as a passive preamp that has a remote.As another poster pointed out,...there is no such thing as a "passive preamp". There's only switches and attenuators in a box. To call that a "preamp" is truly a misnomer.

I hope you enjoy your system as much as I enjoy mine. I stopped over analyzing mine a long time ago and now just enjoy the pretty sounds it puts out. But, trust me on this, I can hear when problems arise. I just don't go looking for them otherwise. That's a slippery slope.

But, this thread was initiated about "passive preamps", not tweaks. How did they get in this discussion anyway?

Changes are just that. Some may be bettter. Some may be worse. I doubt many are in a position to recognize which is which but simply accept any changeas for the better. What's the standard of reference? Personal preference or some solid standard?

As for verifying changes with an O-scope, well, that's akin to selecting an open input, cranking it waaaay up, placing ones ear to the speaker. and then complaining about the noise the equipment generates. If one looks long enough for trouble, one will surely find it, and that's what a lot of floobydust vendors count on.

Room treatments aren't a tweak. They are a fact of like here. And, if one's power is flucuating ot simply dirty, a PC can make a difference. Likewise for cables: no-one has ever defended shoddy construction in cables, have they?

But, this doesn't really prove or disprove that a "passive preamp" withh remote capabilities will significantly (or even audiably) alter the sound. That's still working on the "belief" side of the column. Actually, I think that's the point you were trying to make when you initiated this post.

What does Adcom say about this? Did you check with them?

[nightflier]

I hope you enjoy your system as much as I enjoy mine. I stopped over analyzing mine a long time ago and now just enjoy the pretty sounds it puts out. But, trust me on this, I can hear when problems arise. I just don't go looking for them otherwise. That's a slippery slope.

Amen. And yes, I am one of those over-analytical types and it's a bad habit to have. Maybe I should put on some Miles and relax a bit. Wait a minute, is that a scratch? Or do I need to tweak things a bit. Ah, this hobby.


What does Adcom say about this? Did you check with them?

Good point, I'll see if I can coax a statement out of them. Should be interesting.

[E-Stat]

I don't know why the high end community has continued to call these devices passive "preamps" ? They don't amplify anything. They are attenuators and should be called passive attenuators or something like that but certainly not "preamps."
I think it is just to minimize confusion. They do provide some basic "control" functions, but other than a few transformer based ones that can actually provide some voltage gain, they are indeed simply dimmers. I use a DIY unit using nice parts in the main system. I got there in a convoluted manner.

Originally, I was trying to put together a modest office system. Had speakers, a power amp, and sources, but no pre. So, I went down to Radio Shack and plunked down the princely sum of $15 and bought the parts. Built the unit in a cheap box with two individual pots. Used a couple of Audio Research knobs left over from a faceplate transplant. (Aside: each knob cost more than the attenuator's parts!). It worked fine. Meanwhile, I bought a new CD player that has a 4 volt output. Going through my line stage, I had to limit the gain control between 8:30 and 9:00 for full output. Not ideal, especially for low level listening. So, for grins I put my cheapie attenuators in the main system. Wow! While the Audio Research preamp is a fine unit, it is not perfect. I got better resolution, a wider soundstage (eliminated separation issue with consolidate volume/balance control) and was still able to clip the amp with no gain. Hmmm. I then made a second unit with stepped attenuators, Cardas connectors and JPS Labs wire which made an incremental improvement (though not necessarily in line with the cost differential).

I find it ironic that many of today's preamps are not much more than passive control units having little gain (or really needing much). The Audio Research REF3, for example, has but 6 db of gain using single ended inputs.

rw

[nightflier]

Well my only real experience with a passive preamp was my beloved Monolithic Audio unit. I stumbled on it through eBay and loved every minute I had it in my system. It was also the quietest preamp I ever had in my system. I replaced it because it didn't have a remote, ironically.

But that being my only passive preamp, I don't feel like I am an authority on the subject. I suppose that as long as an active preamp is as quiet as a passive one, it does not really matter. The difficult thing to assess is how quiet it is. I still do my fair share of A/B testing, but with preamps, that involves a lot of configuration shenanigans (like identical sources, amps, and speakers) that probably affect the capabilities of the preamps negatively.