DIY Help: Mono output should be stereo

hossman777 · 26th January 2012

Wired up my passive summing box last night. 4 mono channels with 14.3k resistors, 10 stereo pairs with 10k resistors, stereo output with 220 ohm shunt across L-L+ and R-R+.

Hooked it all up, and I've got sound, but instead of stereo, I've only got mono. Soloed a guitar track in my DAW that was going through the stereo guitar bus to a stereo pair on my summer, slid the pan fader left and right in my DAW....When centered, it was a little louder, but there was no left/right, only center.

I point-to-point wired this rather than using parallel bus wire. I'm guessing the mono channels is where I screwed this up somehow.

For the 4 mono channels, I first soldered my resistors to my -/+ xlr pins, then soldered leads from one -/+ to the -/+ of the next one. On the 4th, I soldered leads from the -/+ of the last mono channel to the -/+ of the first stereo pair (Mono 4 - to Left 1 - AND Right 1 -, same for positive). Proper resistors on all XLR pins, no shorts or wires touching that shouldn't be, etc.

This is my first DIY project, and I'm sad to admit that I don't know a whole lot about electronics like this. Can anyone point out what I'm doing wrong? I can upload a picture after work this evening if it'll help.

Ike Zimbel · 26th January 2012

If I'm reading this correctly, I think you are correct that your transition from the mono channels to the stereo ones is where you are having problems. I think you need to have a pair of resistors between the output of the mono group and EACH of L & R buses, otherwise Left and Right are just shorted together by the mono signal.
Best,
Ike

hossman777 · 26th January 2012

Quote:

Originally Posted by Ike Zimbel

If I'm reading this correctly, I think you are correct that your transition from the mono channels to the stereo ones is where you are having problems. I think you need to have a pair of resistors between the output of the mono group and EACH of L & R buses, otherwise Left and Right are just shorted together by the mono signal.
Best,
Ike

Hmm...OK, I think I get it. I'll mess with it as soon as I get home and see if that fixes it.

If not, I'll just skip the mono channels all together. The only real reason I wanted them was to get the extra little bit of separation and clarity from the kick/snare/bass, but I think a stereo bus out would be just fine for those.

Ike Zimbel · 26th January 2012

Just unhook the mono feed from one side and you'll know right away.

hossman777 · 27th January 2012

You're the man Ike. Got it fixed up (switched to two mono inputs, 6 stereo pairs) and it works perfectly. Thanks for your advice!

26th January 2012	#1
hossman777 Gear addict Joined: Apr 2010 Location: Emmett, ID Posts: 458 Thread Starter	DIY Help: Mono output should be stereo Wired up my passive summing box last night. 4 mono channels with 14.3k resistors, 10 stereo pairs with 10k resistors, stereo output with 220 ohm shunt across L-L+ and R-R+. Hooked it all up, and I've got sound, but instead of stereo, I've only got mono. Soloed a guitar track in my DAW that was going through the stereo guitar bus to a stereo pair on my summer, slid the pan fader left and right in my DAW....When centered, it was a little louder, but there was no left/right, only center. I point-to-point wired this rather than using parallel bus wire. I'm guessing the mono channels is where I screwed this up somehow. For the 4 mono channels, I first soldered my resistors to my -/+ xlr pins, then soldered leads from one -/+ to the -/+ of the next one. On the 4th, I soldered leads from the -/+ of the last mono channel to the -/+ of the first stereo pair (Mono 4 - to Left 1 - AND Right 1 -, same for positive). Proper resistors on all XLR pins, no shorts or wires touching that shouldn't be, etc. This is my first DIY project, and I'm sad to admit that I don't know a whole lot about electronics like this. Can anyone point out what I'm doing wrong? I can upload a picture after work this evening if it'll help.

26th January 2012	#2
Ike Zimbel Gear addict Joined: Oct 2006 Location: Toronto, Canada Posts: 455	If I'm reading this correctly, I think you are correct that your transition from the mono channels to the stereo ones is where you are having problems. I think you need to have a pair of resistors between the output of the mono group and EACH of L & R buses, otherwise Left and Right are just shorted together by the mono signal. Best, Ike __________________ -- Ike Zimbel, Zimbel Audio Productions Ltd. Toronto 416-720-0887 "Studio House Calls". Authorized Warranty service for Allen & Heath, Clear-Com, Drawmer, Soundcraft, SPL and Yamaha. Repairs and upgrades to analog audio equipment including: AMEK, dbx, Neve, Neotek, MCI, Soundcraft and more. Ask about our RF frequency co-ordination services! www.zimbelaudio.com

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27th January 2012	#5
hossman777 Gear addict Joined: Apr 2010 Location: Emmett, ID Posts: 458 Thread Starter	You're the man Ike. Got it fixed up (switched to two mono inputs, 6 stereo pairs) and it works perfectly. Thanks for your advice!