Stereo to Mono Conversions

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At North Ridge Community Church in our Worship Center we have a mono system.  Mono meaning that there is no left or right, there is just the one speaker.  Our room doesn’t have a good shape for everyone to get a good stereo feed, so mono it is.

Almost every CD player, computer, MP3 player or media player is in stereo.  On a sound board, to get these media devices connected, you often have to use a stereo channel or two mono channels (one for left and one for right).  With a mono audio system you combine the left and right channels inside the sound board to send to your speakers.

Most churches require a lot of media devices to play from.  At NRCC we have a computer, iPhone/MP3 player, CD Player and DVD player.  If you add that up that is 8 different connections into the board for 4 devices!  If your church has a smaller format audio console, those add up quick and take up your channels!

One way to fix this is by using a stereo to mono summing circuit.  This isolates the left and right signals and then joins them together to form one output that you can send to the sound board.

As we can see in Figure 1, we have our left and right channels.  The easiest way to think of this is, think of an RCA cable.  So you have your red and your white cables.  The pin that sticks out of the RCA is the positive, the part on the outside is the ground or negative.  This circuit takes the positives of both the left and right, puts them through a 1,000 ohm resistor, joins them together and then puts it into one single RCA jack.  This circuit works well, you may loose a bit of volume using this, but it’s nothing a gain adjustment can’t fix!

One way to improve on this is to add an audio isolation transformer to isolate the audio ground.  By isolating the audio ground you remove any chance of ground loops (humming/buzz).

As we see in Figure 2, there is a transformer added into the mix.  This transformer, in a simple way of thinking about it, copies what is on the left side and pastes it on the right side while keeping both sides electrically isolated from each other.

In the photograph above is a old broken “Live Wire Solutions Direct Box SPDI” in which I removed the transformer.  I separated the two 1/4 inch jacks and connected them together via 1k resistors, this goes to the -20dB pad switch, then goes into a 1:1 audio isolation transformer and then gets connected into the XLR connector.  Pin 3 and Pin 1 are connected together on the XLR connector.  Positive is connected to Pin 2.  This box is now converting my stereo feed into a mono feed.

By making cables or small converter boxes you can “sum” the stereo to mono before your mixer and save yourself some channels.  If you have any questions feel free to post below!


ClearSonic IsoPac A Review

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As seen earlier in the blog, we received our drum isolation booth.  I figured I would put up a review on it here.

At North Ridge Community Church we have a very nice acoustic Pearl Custom drum set.  The kit sounds really great and with our drummers they can really make it come alive.  The problem is, that our drum set sits so far forward on the stage, the congregation gets a full ear of drums.  Also to make this a bit more problematic, we mic the drums and put them through the PA.  So when listening to the worship set while in the room your ears hear not only the kit sound but also the sound from the PA.  This makes the sound a bit muddy and hard to decipher where to listen.

Other issues of the acoustic set, is that the stage monitors had to be loud enough to let the musicians hear themselves.  Adding into this, we have a choir that sings in our traditional service.  The choir microphones picked up a LOT of drums and not much choir.  Because of this I had to place 6 microphones onstage to close mic the choir, as you may know, every mic added lowers your gain before feedback in a live situation.  This was problematic for us as we couldn’t get enough volume out of the choir before feedback would induce.

Enter ClearSonic IsoPac A!  This shipped in via 8-9 boxes, the heaviest being 116 lbs!  After opening up all of the boxes and recycling those it was time to build the booth.  The clearsonic panels come assembled and ready to fold out to surround the drums.  They ship with a paper protective cover that you need to peel off.  The manual states that once the paper is removed from the panels you cannot return it anymore.  After removing the paper from the main shield and the upper set of shields you need to place some plastic connectors to attach the upper to the lower set of clearsonic panels.  I got an extra helper to aid me at this point.

After getting all of the clearsonic panels built it was time to setup their “sorber” panels that go behind the drum set.  Once those were in place I moved the drum set into place.  Following the drum set was to wrap the clearsonic shield around the front and sides of the drums.  The sorber lids go on top being supported by two telescoping metal support bars.  Sorber panels attach via Velcro stickies to the clearsonic panels.  After adding the final touch of a fan to keep the drummer cool you are finished!


There is plenty of space within the booth.  It is quoted to be 7 ft wide, 9 ft long and 6.5ft in height.  Because it is a booth that you setup yourself you can fit it into any shape you need to.

Aesthetically it is beautiful.  This is the nicest looking booth I have seen.  Most of the booths that you see are pretty atrocious.  ClearSonic offers this in a light grey and a dark grey version for the sorber panels.  I decided the dark grey to match our color scheme of the church.


Cable routing is easy, there are small 45 degree cutouts between each clearsonic panel.  Also there is the space between the sorber panels and the clearsonic shield.  Along the same topic with cable routing, depending on how much stuff your drummer has setup in there, I found there is plenty of room for normal microphone stands.

Cooling is a large problem and concern with drummers and isolation booths.  The IsoPac A is NOT fully sealed off.  The back part of the booth has about a 1.5ft gap between the roof and the rear sorber panels.  This space as well as a fan makes it quite nice inside.  I added one more fan sitting on the ground to point up towards my drummer.

Upon walking into the booth and closing the sorber panel behind you, it gets very quiet, to the point where if someone is talking outside the booth, you can’t hear them unless they yell.  Playing drums inside the booth is pleasing, the sorber panels do their job of absorbing a lot of the reflections inside of the booth.

Volume savings are amazing.  Before the booth our drum set in the congregation and onstage would get to 95dB easy.  After installing the IsoPac A the dB level is at 70-75dB.  AMAZING!  Onstage we had to put the drums into the monitors for the musicians to keep on time.  Overall stage volume lowered as we were able to drop the volume on the stage monitors.

The choir no longer complains about the drums being too loud on stage.  And I have been able to reduce to 4 microphones for the choir which has allowed me to get 6dB more gain out of the system for the choir.  The bleed into the choir mics has reduced tremendously.

My only complaint about the booth is that it is dark.  To compensate for this we added a small halogen parcan inside to light up the drummer.

Overall for less than $2k getting the benefits of this drum isolation booth was amazing.  Very much worth the cost for this.  Aesthetically pleasing and with huge volume savings are the biggest pros with this.  ClearSonic makes other sizes and products to aid in lower stage volume and isolation of instruments.  Check them out online at


Drum Isolation Booth Installed

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Yesterday some goodies arrived at the church for me. We ordered a Clearsonic Isopac A drum isolation booth from John at Muzeek World. It shipped in multiple boxes the heaviest being 116 lbs!

Setting it up was pretty simple, the most tedious part was removing the paper protection on each of the clear panels. It took two people to get the main shield upright to attach the vertical riser parts. It took us a total of about an hour to get it all setup including moving the drum set in there.

Overall space inside is great. Plenty of room to get the drums setup in there as well as a bit of room to squeeze around to place microphones.

I will be taking some dB readings today at practice to see how much different the drum volumes are on stage and in the congregation. I will revise this post after I get those readings. I imagine there will be a significant lowering in dB on the stage allowing for lower monitor volumes. Drummer inside the booth will be on headphones.

One of the main complaints of our traditional service is that the drums are too loud, and that the choir onstage gets blasted with the drums. Before this booth we had a small drum shield which mildly helped. My complaint is that the drums bled so much into the choir mics that I would get more drum overhead going into the choir mics than I wanted. So I am excited to mix with this booth.

For now here are some photos. By the our church is just finishing up a food drive, so that is why there is a bunch of peanut butter and stuff on the stage.








Furman PowerPort Repair

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I find it amazing how much equipment in an installed venue needs repair. Little things here and there, but they are things that I normally would think I would not find in an installed venue. This is a main example of that. How did the power cable get ripped out of the back of this Furman PowerPort?


The Furman PowerPort is a remote controlled power conditioner that has a 120V AC limit of 20A. These are also called sequencers as you can place a delay time for power up and shutdown. You would do this so that you can turn on and off your entire system with one switch terminal. In a power up sequence you want your sound board, then system processor, then amps to turn on so you don’t get any “POPS” while turning your system on.

Repairing this was no big deal, but I figured that I would post a few photos from inside of it.





Live Mic’ing of an Acoustic Guitar

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North Ridge Community Church has added a smaller service later in the afternoon at 5PM in addition to our two earlier services at 9:00am and 10:30am. The new service is called Live @ 5 and is in our smaller venue called “Ridge Cafe.” The Ridge Cafe has a pretty good sounding system which is in stereo with QSC 3 way speakers and a single 15″ sub on each side. Our main worship center has a mono system so it is always fun to mix in a stereo rhelm.

Our guitarist was telling me that his pickup in his guitar is not picking up his high E string. I told him that was no problem that we would just pick up his acoustic with a few microphones. Which brings me to my favorite mic’ing technique for an acoustic guitar.


I picked two small diaphram condenser microphones, the AKG CK91 which has a cardioid pattern. What I do is make an XY stereo mic configuration but orient it north south instead of left right. I then place this right in between the sound hole and the 12th fret a few inches from the strings. Then on the sound board I pan the two mics right and left. It gives a very surrounding stereo sense when listening to the acoustic.

The idea is that one mic picks up the lower strings, the other the higher strings. When you pan them it puts them in a very nice stereo image. This works really well when doing an acoustic type mix in stereo. I don’t think the stereo imaging comes across as well in a full band setup.

Lastly when you do this you need to make sure to be real careful of feedback. Each open microphone you add on stage the gain before feedback of the system drops. Basically be careful adding too much acoustic in his monitor. The XY stereo mic still behaves as a cardioid pickup so place the monitor in the same location you would normally with a normal cardioid microphone.

I WISH I had a recording of this live, this room doesn’t have a CD recorder currently. But the next time I mic a guitar like this I will make sure I get a recording of it.


Power Supply Woes

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This last week I got the call that our soundboard in our choir practice room took a fiery and smokey trip to heaven and is not working! Turns out that the ac power fuse blew which was then replaced. Once powered on again, sparks, smoke and flames incued.

The board is a Soundcraft Spirit M12 which is a 16 channel board. The power supply was pretty easy to get to after removing 8 screws and disconnecting two wiring harnesses.

I shot the following photos of the power supply which has some pretty good damage. R24 burned a hole through the PCB board. The R27, R35, R36, R45, R47 resistors blackened the board as well as cracked from the heat. L2 boiled the casing and windings. Lastly the filter capacitor 100uF 400V has a hole in the side of it.










I called the Soundcraft USA parts department and they had a power supply module on hand for $137. So that is being shipped to the church and will be replaced and back in service about 1-2 weeks after the incident. It will be interesting to see what revisions they have made on the power supply board in resent years.

Not too shabby of a repair. Pretty simple really. The benefit of this mishap is that I will probably mount this mixer in a portable rack. Along with adding a few amps, wireless mic and a few eq’s will make a portable system for the church to be able to use whenever they need it. Which is something that the facility currently does not have.