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

Simplest preamp input selection
Simplest preamp input selection
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Old 13th August 2019, 05:26 AM   #1
donovas is offline donovas  South Korea
diyAudio Member
Join Date: Jun 2014
Default Simplest preamp input selection

So Im thinking of mass producing a cheap line level for hobbists here, and was wondering what you found as the simplest solution for input selection.

The preamp will be passive/transformer coupled, so if possible i'd like to keep the input selector passive too (no relays) with the shortest signal path.

I was thinking pcb mount on the same board the RCAs, selector, volume and connect the latter two to the faceplate with 'antennas' (i dunno what to call them. they're basically spring tensioned rods extending thru the chassis from the rear to the faceplate), but i don't know what kind of mounting kits are needed for making the knobs rotate on the faceplate.

help appreciated! thanks!
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Old 13th August 2019, 05:32 AM   #2
ubergeeknz is offline ubergeeknz  New Zealand
diyAudio Member
Join Date: Aug 2018
Arrangements I've seen in oscilloscopes and the like are just a long rod (in case of a rotary control) and are sufficiently held in place by the hole cut in the front panel and a press fit to the control switch or potentiometer. For pushbuttons a cable arrangement like a bicycle gear shift is one I've seen used to good effect, but a push rod arrangement could work if it's a straight ish path.
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Old 14th August 2019, 04:35 PM   #3
Mark Tillotson is offline Mark Tillotson
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Join Date: May 2018
Location: Cambridge UK
These days lots of devices are a lot below line level (phones, ipods, mp3 players), so you
require some gain in a preamp to be able to drive a power amp from these low output devices.

Personally I'd say a reasonable usable preamp needs a gain preset per channel to bring each
to the same line-level. Say upto 15dB of gain per input, then a volume control.
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