Adding line out to Stereomour II

[blue360cuda]

Hey everyone,

Wanted to clean up the stereo rack and make some new custom length interconnects for everything so to not have to keep plugging/unplugging between amps. My idea was to add a line out RCA to my Stereomour 2 to run to a SEX3.0 or other amp/receiver.  The simplest plan was to disconnect the RCA #3 +/- wires from the selector switch tabs and connect them directly to the output tabs of the switch. This would jump the output signal from RCA 1 and 2 sources to the 3rd set of RCAs as a line out before any volume controls.  I ran R3 + to tab A on selector switch, R3- to tab B, L3 + to D and L3 - to C.   Everything made sense and it works fine when I fire it up. I can leave the Stereomour off, run my eros2 into RCA1 and run the RCA 3 as a line out to the SEX for headphone use.  The weird thing that's not making sense to me is when I turn the Stereomour on, if the RCA #3 "line out" is plugged in, with source selector on 1 or 2, it doesn't play anything from the Stereomour to the connected speakers unless I disconnect the RCA 3 "line out" cables.  There must be some part of the circuit I'm overlooking but I can't seem to think of what?     

The other obvious problem with this setup is if I  have the Stereomour on it will play through whatever speakers are hooked up even with the line out so maybe a DPDT selector switch that cuts the signal at the selector into the amp when switching to the line out would be a better option here?  Or a blackbox to split the signal between eros and S2.  I've poked around on the forum and saw a few other guys who tried the same "line out" set up but most of the links were dead for their schematics / layouts. Not sure which would be better sonically (line out v.s. switch box).

Makes me tempted to consider the S2 as a headphone amp as well -  this thing is just so sweet!   Loving it more everyday! 

[Paul Birkeland]

when I turn the Stereomour on, if the RCA #3 "line out" is plugged in, with source selector on 1 or 2, it doesn't play anything from the Stereomour to the connected speakers unless I disconnect the RCA 3 "line out" cables.  There must be some part of the circuit I'm overlooking but I can't seem to think of what?     

Yeah this doesn't make a ton of sense, you just have this cabled up to a SEX amp?

You could send the output of the selector switch to a DPDT toggle switch, then have that either feed the volume control for the Stereomour or send it back to an extra set of RCA jacks (which you could just add in the wood base in a pinch).

[blue360cuda]

Hmm . . . I actually had the SEX downstairs on the bench. Grabbed it and everything works as intended.   My "test" amp was my old Marantz 2270.  I usually use the aux input or tape for hooking up sources.  There must be something weird using the tape input on the Marantz?  I switched to the aux and its actually working on that now too.   The Marantz plays but the S2 cuts out when this "line out" RCA is plugged into the Marantz tape input but all good when using aux.  No idea lol

My ultimate goal would be an extra set up RCAs either connected like I have now but so I can keep 3 source inputs or do the DPDT switch idea.  Does it hurt anything sound-wise to have the line out RCAs "live" all the time and just keep the downstream amp (sex) off unless in use or would the DPDT switch be a better call?

[Paul Birkeland]

You'd just be adding more cable capacitance and a volume pot as a load to whatever is driving the Stereomour.  On paper, the switch offers some benefits, but in reality they may be difficult to hear.

[blue360cuda]

I have an idea how I'd like to wire this but not sure if its a thing or not --     So most of my electrical experience is with cars / motorcycles. When I'd wire something like a kill switch on a vintage bike I'd use a relay and have the switch control the relay v.s. having the 12v go all the way through the switch and back to the coil. I'm assuming from an audio standpoint that less is more with signal wiring and keeping runs as short as possible and away from potential noise sources like the power supply / heater wiring.  Is there an amp circuit equivalent of a relay I could use?  Something where the actual switch wiring occurs near the switch / source and the toggle controlling the switching is remote from that?  I hope I'm making myself clear.   Trying to avoid having to drill extra holes but keep runs as short as I can for the signal input wiring.   

Before I had this idea I picked this one up for the signal wiring ,  It's sealed with gold plated contacts  https://www.mouser.com/ProductDetail/506-MTA206P

Got this one for the 8/16 ohm impedance switch https://www.mouser.com/ProductDetail/506-MTA406N

[Paul Birkeland]

Yes, there are micro relays that are used in situations like these.  The downside to applying them in your application is that they need to be PC board mounted, so you'd have to find a generic board that will do what you want it to, or draw up and order your own board.  You also need a dedicated DC power supply as part of this package.

The relay application for automotive/motorcycle applications is primarily to keep the currents handled by switches extremely small, and therefore the wiring (and fusing) pretty light duty for the majority of the wires running around.  The current involved in a line level signal is extremely low (tens of microamps is certainly realistic), so there isn't much of a concern there.  You'll also see relays used where they can dramatically reduce the amount of superfluous wiring in a preamp (input selection at the input jacks), or as muting device at the output jacks.