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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Passive pre-amp for active speakers
Passive pre-amp for active speakers
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Old 14th January 2018, 02:59 AM   #11
gigigirl is offline gigigirl
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Hi, Look on F/Bay, there are heaps to chose from. Cheers
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Old 14th January 2018, 08:18 AM   #12
sidlauskas is offline sidlauskas  Lithuania
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Quote:
Originally Posted by georgehifi View Post
Watch out, many active speakers have 10kohm sometimes 5kohm input impedance on the input of their amps, courtesy of Class-D. This will cause maybe a voltage divider with the passive, and you loose voltage headroom.
Do you know what the input impedance is of the active speakers not just at 1khz but from 20hz to 20khz just incase there are input cap/s.?

Cheers George
Thank you for your thoughts, George. The impedance of my active speakers is 10k ohms. I can't find any additional information about impedance, so I believe it's at 1khz. The active speakers are Yamaha HS 7's.

The passive preamp I already ordered and waiting for it to be delivered:

Input Impedance: 10 kOhms
Output Impedance (full volume): 0 Ohms
Fixed Attenuation: 0 dB, -10 dB, -20 dB

SMD stepped attenuator is used for this preamp.

The plan was to connect two different phono stages to it:

phono stage 1
Output impedance: 82 Ohms
Maximum output voltage: 9 V

phono stage 2
Output impedance: 200 Ohms
Maximum output voltage: 1.8 V

Is this a good match? Please give me an example how this could be calculated. Thanks!
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Old 14th January 2018, 01:09 PM   #13
adason is offline adason  United States
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I have made myself many passive preamps, nothing to it, just good shielding.
But if you want very small, professionally made one, shiit has one with two inputs, cheap, works well.
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Old 15th January 2018, 06:52 AM   #14
sidlauskas is offline sidlauskas  Lithuania
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Quote:
Originally Posted by adason View Post
I have made myself many passive preamps, nothing to it, just good shielding.
But if you want very small, professionally made one, shiit has one with two inputs, cheap, works well.
I wanted to buy it, but it was already out of stock, so I bought another one. Now I'm scratching my head wondering if it's gonna be a good match to use it with my active speakers where the input impedance is 10k ohms (more info in my previous post). Any advice would be helpful.
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Old 15th January 2018, 07:32 AM   #15
bifor is offline bifor  Italy
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Old 15th January 2018, 08:35 AM   #16
sidlauskas is offline sidlauskas  Lithuania
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Quote:
Originally Posted by bifor View Post
This is what I'm probably looking for. The problem with this one is that it has only 1 input. I'm looking for something with at least 2 inputs.

What do you think guys about this one - Schiit Saga

Last edited by sidlauskas; 15th January 2018 at 08:38 AM.
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Old 15th January 2018, 09:18 AM   #17
rmaudio is offline rmaudio  United Kingdom
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Quote:
Originally Posted by sidlauskas View Post
This is what I'm probably looking for. The problem with this one is that it has only 1 input. I'm looking for something with at least 2 inputs.

What do you think guys about this one - Schiit Saga
Both this and the SPL Volume control are active - not passive.
Okay - the SAGA can be run passive - but if you're paying that sort of money for the tube stage then why would you...?

In any case the 10K input Z of your speakers isn't a good match for any reasonable value of volume pot or switched resistor network (aka Passive Preamp). Go active and buffer.
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Old 15th January 2018, 09:24 AM   #18
scottjoplin is offline scottjoplin  Wales
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The output impedances of the sources are 82 ohms and 200 Ohms, wouldn't a 1k or 2k pot be ok?
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Old 15th January 2018, 09:32 AM   #19
sidlauskas is offline sidlauskas  Lithuania
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Originally Posted by rmaudio View Post
Both this and the SPL Volume control are active - not passive.
Okay - the SAGA can be run passive - but if you're paying that sort of money for the tube stage then why would you...?

In any case the 10K input Z of your speakers isn't a good match for any reasonable value of volume pot or switched resistor network (aka Passive Preamp). Go active and buffer.
I completely understand that they're active, but as I understood there is no other option here than use active. The problem now is that I just can't find what I'm looking for - simple preamp with several audio inputs and volume pot that would fit my active speakers. That's it, nothing else.

Last edited by sidlauskas; 15th January 2018 at 09:34 AM.
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Old 15th January 2018, 09:37 AM   #20
rmaudio is offline rmaudio  United Kingdom
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Quote:
Originally Posted by scottjoplin View Post
The output impedances of the sources are 82 ohms and 200 Ohms, wouldn't a 1K or 2k pot be ok?
Well I was considering the input Z of the active monitors that the OP has given as 10kOhm. I guess you could look at 1K0 pot at a push but it looks like quite a load for the source to drive min at - 909Ohm.

BUT the big problem - that I hadn't taken into account - is that the sources are 'Phono' by which I take it to be the bare output (before RIAA correction) of a cartridge - MM or MC is unstated.
If this is the case then the cartridge needs the correct loading and RIAA response before anything else. Definitely not a 1K0 or 2K0 pot with 10K off the wiper.
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