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10-29-2004, 02:06 PM
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500+ Head-Fi'er
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passive preamps, can they work well?
hi gang, i'll be needing a preamp for a new power amp that i'm buying for my speaker rig and i'm not sure what do do about a preamp.
i've heard both good and bad things about passive preamps.
some say it's the purest way to get the signal through, while others say the impedance matching problems cause poor sound.
what do you guys have to say?
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10-29-2004, 03:10 PM
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Headphoneus Supremus:
DarkAngel's a man, baby!
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Join Date: Aug 2001
Location: Shadows of the Night
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If you only want simple system with one source and amp then a well designed passive will work extremely well especially if matched to output/input levels of source/amp.
At Audiogon I got a killer passive LAT (luminous audio tech) with custom dual volume controls (actually variable shunts) and values matched to my gear. Get the caddock resistor upgrade if you try one:
LAT
Here is pix of my custom unit in action, dual volume controls/caddock raised price to $225:
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10-29-2004, 03:10 PM
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Headphoneus Supremus
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Join Date: Aug 2002
Location: Ohio
Posts: 7,990
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I have used passive preamps for years; they can sound great. You just need to be sure your source is capable of driving the interconnect cables and the input impedence of your amp.
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10-29-2004, 03:18 PM
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Headphoneus Supremus
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Join Date: Dec 2003
Location: Toronto, Ontario
Posts: 10,136
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Question: Would the famous 'hot' output of the ART DI/O actually be a benifit with a Passive Preamp?
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10-29-2004, 03:58 PM
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500+ Head-Fi'er
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my source will actually be the Behringer DEQ2496, but with 1.5m XLR to RCA cables from source to preamp so i'm worried about the length of the cables. my preamp to amp cables will be 20cm long.
however, the Behringer has a gain control so perhaps it would be alright. i know its output was quite a bit higher than my Teac cd player's.
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10-29-2004, 04:10 PM
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Headphoneus Supremus
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Join Date: Feb 2002
Location: Seattle, WA
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1.5m cables are too long for use with a passive preamp.
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10-29-2004, 04:26 PM
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Headphoneus Supremus:
Videographus Supremus:
Makes audio cables using super-advanced materials, like "some clear tape" and "some not so clear tape."
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What is a good length of cable then? What happens if the cable is too long?
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My advice to you:
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10-29-2004, 04:27 PM
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Headphoneus Supremus
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Join Date: Dec 2003
Location: Toronto, Ontario
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And are we talking the cable from the source to passive preamp as well as the cable from the passive preamp to the amp?
I'm wondering if my passive preamp with 3 source selector and 3 output selector might be a bad idea now since I wont be able to get the cable lengths short enough... 
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"For a list of all the ways technology has failed to improve the quality of life, please press three."
Moon Audio modded Original CD-2008MK-II / de Almeida Signature Shadow XLR / McAlister Audio Massive Attack / Headphile modded BlackGold recabled AKG K340 OR APureSound V3 recabled Grado RS-1
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10-29-2004, 04:41 PM
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500+ Head-Fi'er
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1.5m is from the source to the preamp. i heard that was not as critical.
i have custom cables from preamp to amp that are about 20cm long.
i'm not sure what to do about those other cables. i'd have to do something custom as well to get as short a run as possible, but does it matter that much?
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10-29-2004, 04:46 PM
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Headphoneus Supremus
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Quote:
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Originally Posted by tomek
1.5m is from the source to the preamp. i heard that was not as critical.
i have custom cables from preamp to amp that are about 20cm long.
i'm not sure what to do about those other cables. i'd have to do something custom as well to get as short a run as possible, but does it matter that much?
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I ran a 1.5m cable from the source to the passive preamp and then a 1.0m cable from the passive to the amp without any problems at all. Runs of cable that are to long and/or high capacitance can roll of the treble. A low capacitance cable will help. How robust the output from your source is has a good deal to do with how well this works too.
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10-29-2004, 05:54 PM
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Join Date: May 2002
Location: Switzerland
Posts: 6,055
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My cables are 30 and 40 cm between source and passive attenuator and 2.30 m between the latter and the power amp. No problem at all and great sound. I got a similar sonic balance with an active preamp (Prehead MkII) -- which proves that this length isn't critical in my setup.
What's important apart from cable length and capacitance is the ratio between source output impedance and power-amp input impedance. It should be as high as possible. My main source, the Bel Canto DAC2, has 20 ohm, the Metaxas Solitaire has 100 kOhm, making a ratio of 2000.That's a huge number. But I also got good results with my Hitachi FM tuner (2 kOhm) and my BEL 1001 power amp (20 kOhm), thus a ratio of 10, with the same cable lengths. But this could indeed be a little close for a perfectly neutral sonic balance.
In my experience nothing beats passive amps in an electrically favorable system when it comes to signal accuracy and sonic purity. In an uncritical environment all «improvements» resulting from an active preamp are in fact euphonic colorations. But one thing must be taken into consideration: the passive variant can be too revealing in certain cases.
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11-01-2004, 07:43 AM
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Contributor  Headphoneus Supremus Thought the last line in Citizen Kane was "nosebud."
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Join Date: Jun 2001
Location: Back to Munich - bye Hannover!
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tomek: How many sources do you intend to connect to your preamp? If it's only one, why not mod your new poweramp and integrate a pot right into it? That would eliminate superfluous transitions and be cheaper than a passive preamp as well...
Greetings from Hannover!
Manfred / lini
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Favs: AKG K240S - "The new Groovalizer" as well as Beyerdynamic DT531 & DT440 - "The old Groovalizer" & "The Funkalizer"
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