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passive preamp question

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Ron (or anybody)
Can you speak to the question I have about impedance matching in the regular AA?
This question here
Pretty please?

Follow Ups:

Re: passive preamp question carlbecker 06:47:24 01/26/01 (0)
Just for an example I use the Reveille passive with 10k volume controls. My front end is the Reveille phono or a Meridian CD player. I use a VTL Tiny Triode 25 amp with an imput impedance of 100k. I am very pleased with the current setup. If you are after transparency use a passive with proper sources and you haven't added much to the signal. I think the attenuator design and quality is critical to passive performance so get the best you can.
Re: passive preamp question Eric_Str 12:43:15 01/23/01 (0)
I am running a Welborne 10K passive into Apollos.
I also have a Foreplay that I'm figuring out what to do with.
On my best source, a Blue Circle Phono stage (which has lots
of drive), the Passive has more spacial sense, and is just generally a little clearer and better sounding.
On my MSB link dac the Forplay has more body and better bass than the passive. But, again, the passive has more spacial information (especially front to back). However, on 24/96 the Forplay sound noticably better. It has a lot more body and presence.
On my cheap tuner, VCR, and cassette player there is no comparison. The passive sounds dead compared to the Foreplay.
So there you have my experience, which is exactly what Ron W. said. If your source components are up to the task, the passive sounds better. But the less able the source in the current department, the more it needs an active linestage to make up for its deficiency.
Re: passive preamp question Ron W. 11:08:00 01/23/01 (1)
Here's my take on the passive preamp situation.
A passive preamp is just a few extra connectors, one or two switches and an extra set of interconnects in the signal path so there is really no way IT can do much damage to the signal, compared to an active linestage.
When people say they experience a loss of dynamics associated with their passive, I generally look towards their source as the culprit. i.e. their CD player, phonostage, etc. doesn't have the drive capability of a high quality preamp. Most high quality preamps are built with beefy, well designed power supplies...but look under the hood of your favorite $2000 CD player and you may be disappointed in what you find for a power supply.
So I suspect if are loosing dynamics with the use of a passive linestage, even if you could connect the CD player directly to the amp (i.e. bypass the passive) you would still not have the dynamics.
And thus, I've found that with better quality source players one will not experience this loss of dynamics.
So the moral of the story is....if you like passive linestages, then either purchase better source equipment, or break out your chainsaw and modify/upgrade your existing players.
When selecting an attenuator value for a passive, generally, the lower the value the better. If all of your source equipment is solid state with a low output impedance, then go with a 10K. If you have a tube CD player or tube phonostage, then go with a higher value (20-50K) so as not to load down their outputs.
Ron
- OK, so here's the deal Randy Bey 14:19:32 01/23/01 (0)
  *When* I win the newsletter contest I will pony up some extra bucks and go for a Reveille passive, to attach to my Laurel II's, which are attached to my Klipschorns.
  Right now as a source I have a MSB Link III DAC, but that ol' audiophile bug is pointing back at my source. I hope to someday (soon) change to an Audio Note DAC 1.1. This is a tube based DAC and they report that they do not do well with passives. Their request for "impedance" (is that even the right word?) for the passive was 100K.
  Does this mean that I should go active or can I squeak by with a passive?
Re: passive preamp question Chris O 08:26:34 01/22/01 (4)
The minimum rule of thumb is that the source's impedance should be lower than the receiver's impedance. This is why passives impedance are between 300 ohms and 100K ohms. The passive is both a receiver and a source. When dealing with passive attenuators, the main issues to consider are:
A. Required Gain (not an issue, apparently, in your set up)
B. Low resistance/capacitance of the interconnect
C. Relatively short length of the interconnect (under 10 feet)
If these are not issues, the selection of the overall impedance of the attenuation circuit is a tradeoff. 10K is a very popular value for Solid State systems and 50K is more popular for tube systems. This has to do with tube circuits liking to see a higher impedance.
From a subjective standpoint, some people hear less "punchy" bass with passives. This could be due to the extra current available from line amps over what is available from the playback component. There could also be some built in bass reinforcement in certain line amps. On the other end, if you have long "complex" interconnects, there could be some high frequency roll-off.
With a high quality source component, short runs of interconnects and an amp with full output sensitivity of around 1v, you should be very happy with passives. This is especially true with a ladder stepped attenuator like Ron's.
- Re: passive preamp question: A matter of Mood as well mobile homeless 07:52:54 01/23/01 (3)
  First of all, that was an excellent post from Chris O; he did an excellent overview of the whole picture of passives.
  I just wanted to add a few things. Given the perfect circumstances of proper interconnects, amp sensitivity, and your source's ability to drive the signal to sufficient volume, a passive does offer much in relation to transparency and detail.
  What you CAN lose, however, is a bit of the midrange drive and warmth, along with a slight lack of body. Really, it seems to be a tradeoff, depending on mood. I have both passive and active stages. Given the option of a colored, less than transparent, so-so preamp, the passive DOES win out must of the time. It just sounds like the grundge and noise riding along with your signal just vanished.
  However, when comparing the passive to an excellent, transparent, dynamic active preamp, the choice becomes far less clear. In fact, I would have to say that after listening to a passive for awhile and inserting a fine active stage, you are almost shocked at the drive and midrange warmth it adds. Indeed, you almost wonder WHY you ever opted to put the passive in! Alas, the same holds true in the reverse...
  Personally, I like having both and passives are so inexpensive, that it makes sense to either make or acquire one.
  Yet, given the proper resources ($$$), I think an excellent active preamp beats out the passive in full range warmth, drive, body, and even musical detail if really done properly. This seems to especially hold true with a 2A3 SET as the midrange really does nicely with a proper active stage.
  I imagine, as I said before, the Laurels might do well with both. One thing you can do, order a passive from one of the online locations that gives you a 30 day return policy (AA). Consider it an extended audition. If you are not happy, simply return it with a bit more education gained in the process.
  kh
  - Re: passive preamp question: A matter of Mood as well riki 03:40:48 01/28/01 (0)
    This has been an issue I have been wrestling with for months. Overall, we tend to like the sense of proportion provided by an active preamp. Extra gain offered to source signals just seems to me to provide a sense of immediacy that a passive control can almost match, but not quite. I have built from scratch 2 (sorry, 2 from scratch, one kit)different active linestages, and all of them sound quite good to me -- especially the Eric Barbour design that uses a single, subminiature tube. For me, the drawback has to do with the extra noise of an additional power supply. Lowthers in horns tend to be extremely sensitive, and if upstream components are less quiet than desireable, the Lowthers will as faithfully amplify hum and buzz as they will music. And please don't even mention the fact that I might need to look at me grounding scheme. Everything (literally) in terms of shielding and SPG (single-point-grounding)has been tried. Lifting the grounds on the active preamp and one amplifier helped but little. So I am now using a passive control/attenuator. I would like to offer this, though, to those who might like to try a passive approach: Ther is NO NEED to BUY an expensive, already built or kit linestage if you want to get the flavor of a passive attenuator. MAKE ONE! They are easy to build. Get some RCA or BNC jacks (I use BNC) from Radio Shack, as well as a couple of 10K or 100k mono pots (I prefer linear to log taper), some cheap hookup wire, a decent little chassis for $6.00 -- some hardwood trim from a co-teacher at school makes mine look more expensive than it is, as well as a selector switch if you want one. With a couple of hour's work, you can see what a passive does for your system. For me, it provides the opportunity to listen to clean, clear music, without the constant frustration of figuring out how to kill some phantom noise of an active linestage, many of which provide far more gain than what many amps need in order to be driven to full output. Make your own interconnects out of inexpensive, low capacitance (mine measure just 16 pfd/ft.) coax with an all copper (not copper clad) center conductor and braided copper shield, and you are ready to listen to good-sounding music for a very reasonable price. After that, then go out and buy expensive volume controls using fixed resistances.
    I just miss not seeing the extra pair of tubes glow in the dark!
    Erik
  - Re: passive preamp question: A matter of Mood as well Randy Bey 14:27:37 01/23/01 (1)
    I have an OBH-12 coming to try out.
    My big question is how an AN DAC will sound rather than my MSB with a passive.
    - Re: passive preamp question: A matter of Creek Mood as well mobile homeless 20:40:45 01/23/01 (0)
      
      In Reply to: Re: passive preamp question: A matter of Mood as well posted by Randy Bey on January 23, 2001 at 14:27:37:
      
      I have an OBH-12 coming to try out.My big question is how an AN DAC will sound rather than my MSB with a passive.
      Great idea trying out the ole little Creek. I got mine on Ebay for less than $200 and it has surely been worth that for the great remote and excellent sound. That being said, I have heard other passive preamps that sounded better but the Creek is a great little unit. You will get a good idea of the stark difference between the Creek and your NAD, which is an OK sounding piece for what it is but surely not on the same level. Ironically enough, I used an old NAD 3150 as a phono preamp running into one of Stan Warren's early Superphon passive units; did really well at the time, especially when you have NO money to spend!
      Not sure of your concern with the Audio Note DAC. What is the ouput? Most are around 2v or so and that should be fine. Cant remember if you said what it was or not. My Rega Planet is 2v and puts out plenty of volume for most material, and this with the lowly ProAcs - not your super sensitive Klipsch!
      Let us know...
      kh
      ps - See the pic above of the Creek? Notice the all black face without the bright green "Creek" writing? A simple fix here - Just turn the plate around and put the green mess facing the inside. Took 2 minutes and it looks 100 times better.... like a little custom, black, mystery box. Of course, the sound got 200% better....

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