Hi
I hope to make a passive preamp as a beginners project. I have come across some bits with 2 stepped attenuators and 2 other potentiometer. The attenuators are only 10 step which isn't ideal but its potentially a free way to hear what Passive preamps sound like and learn along the way.
Would these be ok to make a dual mono passive pre?
I hope to make a passive preamp as a beginners project. I have come across some bits with 2 stepped attenuators and 2 other potentiometer. The attenuators are only 10 step which isn't ideal but its potentially a free way to hear what Passive preamps sound like and learn along the way.
Would these be ok to make a dual mono passive pre?
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First, read the below thread on the subject.
http://www.diyaudio.com/forums/anal...osing-potentiometer-passive-preamplifier.html
http://www.diyaudio.com/forums/anal...osing-potentiometer-passive-preamplifier.html
Measure the resistance from one end (the ground end, preferably) to the wiper at each position,
and that will give you an idea of how well it will control the volume.
I'm sorry, but do we have to call these attenuators, “passive preamps”? What's next, calling a hookup coax … a 0 dB passive preamp? They're not amplifying anything! This is annoying.
In my mind, at the very least, a preamplifier must be in the business of
[1] amplifying something, even it is impedance conversion only.
[2] possibly acting as a switching hub for multiple sources to home.
[3] usually incorporating attenuators AKA "volume controls" for convenience
[4] nominally buffering their output to prepare for the next stage - line amp.
[5] almost always incorporating RIAA contouring for phono stages, if included at all.
Better would be to call these things things precision attenuators. And I've got nothing against experimenting with them to your heart's content. RAYMA gives good advice … yet at the core is something as yet unsaid: whatever the value of the attenuator, it must be of high enough resistance (impedance) at all settings so as to not overly load the source connected to it.
That's why you need to measure it.
Now, go have fun!!!
GoatGuy
In my mind, at the very least, a preamplifier must be in the business of
[1] amplifying something, even it is impedance conversion only.
[2] possibly acting as a switching hub for multiple sources to home.
[3] usually incorporating attenuators AKA "volume controls" for convenience
[4] nominally buffering their output to prepare for the next stage - line amp.
[5] almost always incorporating RIAA contouring for phono stages, if included at all.
Better would be to call these things things precision attenuators. And I've got nothing against experimenting with them to your heart's content. RAYMA gives good advice … yet at the core is something as yet unsaid: whatever the value of the attenuator, it must be of high enough resistance (impedance) at all settings so as to not overly load the source connected to it.
That's why you need to measure it.
Now, go have fun!!!
GoatGuy
you had me until "almost always … if included at all"
Yes… that was an awkwardly phrased point. What I meant to say was that no preamplifier will have RIAA contouring unless it has a channel targeted at sourcing a vinyl phono stage pickup. Then it will. Almost must, unless the phono signal train has a separate discrete RIAA “pre-preamplifier”. Sorry about the phrasing. I'm tired.
GoatGuy
If you are not prepared to buy a cheap digital Multi-meter to do your own measuring, then you are about to enter the wrong hobby.
Thanks for those words of encouragement Andrew. It would be very irrisponsible of me to invest in this at the moment as I have far more important financial priorities. If I was in a better financial position would you think I would be trying to create stuff out of salvaged parts?
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