Passive Pre-amps

Arfa

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Been having a gander around for a new pre-amp for my setup and have come across a few passive pre-amps. So I gather they're unpowered and basically a very clean source switch. Worth checking out? Have seen an old Mod Squad Line Drive local to me for a ton - bit much or a good price? Reckon it'll sit well behind my C.A. P500 power amp? Have also seen a couple of Creek passive pre-amps too.

 

paulfromcamden

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Good question
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I've been wondering the same thing.

Can anyone also explain what you're actually paying for in a high-end passive pre-amp? It's just a posh volume control and some wire surely?!?

If I was in a position to run a passive pre I might be tempted build something like this:

http://hjem.get2net.dk/aaholm_audio/projects/PasPre/PasPre.htm

 

Papa Lazarou

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You need a power amp with high input gain sensitivity for a passive pre to work well ime. If your amp is designed for an active pre-amp then i would strongly suggest you to stick with those instead. Get it wrong and you'll have a smooth but flat sound lacking in bass and dynamics.

 

meninblack

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paulfromcamden wrote:

Can anyone also explain what you're actually paying for in a high-end passive pre-amp? It's just a posh volume control and some wire surely?!?
My passive pre consists of a printed circuit board, two rotary switches, a twin-gang pot and a few resistors in a nice box. New RRP was £1000.
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paulfromcamden

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meninblack wrote:

paulfromcamden wrote:
Can anyone also explain what you're actually paying for in a high-end passive pre-amp? It's just a posh volume control and some wire surely?!?
My passive pre consists of a printed circuit board, two rotary switches, a twin-gang pot and a few resistors in a nice box. New RRP was £1000.
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shock.gif.7732780fe7e208b945ce79ca96402fca.gif
indeed! But I bet it sounds nice:)

So which are the expensive components? (I'm guessing 'all of them'
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)

 
E

earl of sodbury

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I built one from a diecast box, an Alps pot, acouple of resistors, some silver wire and teflon tubing, a switch and 6 RCA sockets, parts cost about £50 max, I worked the wiring out in my head (and I'm dim about this sort of thing), and when it wasn't perfect I had some great advice from Forumites about making the volume pot a passive shunt: recommended. See: http://www.hifiwigwam.com/forum19/8346.html

churz, eofs

 

Ant

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i use a passive pre that is based on two mutlitapped transformers giving 25 levels of attenuation. To my ears in my system it works well without all the associated issues of resitor based passive pre amps

 

Micke Y

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As Papa Lasarou says they wok fine if your power amp has a high input impedance and sensivety. Like my Audiop Synthesis Decade but I know of other amps which would not suit passives at all.

One strong alternative is the transformer versions that work very good indeed.

cheers

Michael

 

paulfromcamden

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earl of sodbury wrote:

I built one from a diecast box, an Alps pot, acouple of resistors, some silver wire and teflon tubing, a switch and 6 RCA sockets, parts cost about £50 max, I worked the wiring out in my head (and I'm dim about this sort of thing), and when it wasn't perfect I had some great advice from Forumites about making the volume pot a passive shunt: recommended. See: http://www.hifiwigwam.com/forum19/8346.htmlchurz, eofs
Interesting thread - thanks
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Arfa

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Papa Lazarou wrote:

You need a power amp with high input gain sensitivity for a passive pre to work well ime. If your amp is designed for an active pre-amp then i would strongly suggest you to stick with those instead. Get it wrong and you'll have a smooth but flat sound lacking in bass and dynamics.
How high sensitivity would you say is suitable? My P500 is apparently 250mV and has an input impedance of 47K Ohms. But yes, it is intended to go with an active pre amp. That said the local guy with the Steve McCormmack Line Drive said I could audition it first, so I may just cart my power amp down and see what they're like together.

Also spotted a Creek OBH 12, which has a transformer for a remote and would be a nice match for my Creek OBH8SE phono stage - but its only got 3 inputs...
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meninblack

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My Rotel RHB10, which is designed to be used with a passive pre-amp, has an input sensitivity of 775 mV and an input impedance of 30 kohms.

 

Micke Y

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I had an amp that had only 2k ohms input impedance and it not work at all. No bass and no dynamics. Then a few days later I tried a transformer version and it was no problems.

Op amp outputs of CD´s usually have no problem driving a passive pre but some tube will roll off the top end a bit.

cheers

Michael

 

Papa Lazarou

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You could try a TVC passive (transformer volume control). I've tried one of these myself, they can be very good in some systems. Personally i prefer an active pre.

 
E

earl of sodbury

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Check the classifieds, chap selling a DIY unit and open to offers - worth a punt, most DIYers take far more care than mass-produced stuff, and there's really nothing to go wrong in so simple a design.

 

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