The el-cheapo audio mixer, in pics

[tmc]

So here it is, in pics for those who need to see it to believe it.

The diagram (borrowed from someone):

Now the box:

And finally, the guts:

And that's it.

THe parts list:

4 x 1/8" stereo minijack

6 x 10k ohm 1/4 watt resistors

1 x small project box

Plus some solder, a drill, and a couple of beers.

Works perfect. Boostaroo is definitely necessary though, to compensate for the small but noticeable drop in DB due to the resistors. But, with this complete, no worries about back-feeding and potentially screwing up valuable electronics. Well worth it.

The cost? About $12 in parts. You can do it for a hell of a lot less if you avoid Radio Crack, but they were nearby and very convenient, so that's where I went.

 

[Aasland]

Pardon my electonically ignorant questions (I didn't even finish the electronic's merit badge) ... but ...

Wouldn't resistors still allow backfeeding, just at a lower level?

Would it make sense to use diodes instead of resistors to avoid the back-feeding w/o loss of volume?

 

[Fred W]

No. Audio is a low level Alternating Current (AC) signal. The P/N junction of a diode would look like a resistor to it at nominal levels because there isn't enough voltage to forward bias the P/N junction. If you boosted the signal amplitude way up it would only end up rectifying and distorting the audio signal.

 

[Aasland]

Audio is AC ? Really ? I didn't know that. That explains why a diode won't work. Thanks!

 

[Geezer]

Put it inside an Altoid box and save the cost of the 'project box'.

I built one of these a few years ago inside of a shotgun hull (fired shell). As you stated, you need a Boosteroo or other amplifier to overcome the resistance. I found it simpler and cheap enough to simply buy an AmpliRider for 65 bucks. AmpliRider is waterproof and mixes/amplifies up to 3 inout signals.

 

[squeezer]

Sweet little project. Well done.

 

[tmc]

Fred nailed it. I'm no electrical whiz, but I know enough to be dangerous. This is one of the first things I checked out, because a diode, at first, seemed like the correct choice. Alas, it is not!

Geezer, the altoids box is nice and all, but this is much sturdier and for $2.49, not much more expensive than Altoids!

And I did research Amplirider, MixIt, RadarOverRide, etc., and I'm sorry but I'm not sending off $60-$150 for something that cost me less than $35 total. (12.5 for the homebrew audio mix and 20 for the boostaroo revolution) Plus I already had the Boostaroo. Plus it's a lot more fun to build it yourself!!

FWIW, here is the actual RadioShack parts list:

Part#

270-1801 Project Box --------- 1@ $2.49

274-0249 Stereo MiniJack --- 2@ $3.19 (2 per pkg)

271-1335 10k 1/4w resist ---- 2@ $1.19 (5 per pkg)

Subtotal $11.25 + local tax = $12.18

 

[Patriot]

does anyone know something/enough about the J&M JMCB2003 CB system ???

the system comes with a wiring harness with only one aux input 3.5 mm commonly for ipod/mp3 music

I'm to the point I want to add in my Zumo550 (directions and iPhone bluetooth paired to the Zumo) and new recently released Adaptiv TPX radar detector with the aux sound output

J&M sure is proud of their stuff: integrator unit...friggin' $370...cable for Zumo 550 $40 ...cable for TPX $50

the headsets J&M sell for their propietery "amplified" 6pin headsets make we wonder...mixit sells 3.5mm plugs on cables with isolation filters reasonable if needed

"splain to me on a 12th grade level...I'm a mechanical engineer and have never touched, held, or seen an electron so far...and don't get me started with quantum mechanics

I quote:

solving the problem:

or buying a cheap 'Y' cord from an electronics store to connect two devices together. The problem with the 'Y' cord approach is that some devices are not compatible with each other, and one device can damage another by using this type of cord. When you have invested so much money in your equipment, do you really want to take that risk? In addition to compatibility problems, some audio devices simply are not loud enough to be heard clearly while riding.

What devices will work NOT with the Mix-It2?

Certain FM radios don't work with the Mix-It2 when the Mix-It2 is operating off of bike power due to interference by the oscillator in the DC converter of the Mix-It2. I have not found a way to shield this though the problem has only been reported twice, so I presume FM radios are not a common device used with the Mix-It2. Helmet speakers, unless they are rated at 16 ohms or higher, typically will not work with the Mix-It2. Other products require an isolation cable for use with earlier Garmin GPS units (those that do not have MP3 playback nor satellite radio capability), Escort/Bell/Cobra radar detectors but the Mix-It2 does not since it has isolation built into two jacks - all that is required is a mono patch cord.

 

[Aasland]

I didn't have a radar detector, but I had a JMCB2003 and a Zumo and a phone and wanted to make it all work without the $400 in J&M parts. So I contacted these guys:

https://www.cellset.com/Motorcycleitems.html

Explained I was a software engineer (i.e. the kind of engineer who didn't study physics) and what I tried to do and they set me for about $90. Since you're adding a RD it might cost you a little more ... but send them en email, they will prolly be able to help.

 

[tmc]

I know nothing about the j&m, but i do know that the setup I posted above will safely mix your audio sources prior to connection to your single aux-in. Just set your volume levels in order of priority - ie set your radar to LOUD and the others quieter. Beats $350!The folks at Cellset are the ones who made the RadarOverRide which is what I would have bought had I not gone home brew.

 

[MartinH]

For some reason I'm not seeing the pictures.

 

[Patriot]

email from MixIt2 owner John Brown advises the Zumo is problematic and won't work because of the J&M

email from Gary at AmpliRider advises his will work fine, just need an isolation connection cable for the mono Radar Detector

there's no "priorty" circuit that allows one device to "override" another, but I like it that way and can discern each without cutting out

another with separate volume settings...that's how it works now except the J&M has the CB on priority over the aux stuff.

guess need to call Kennedy Motorcycle Items as recommended by Aasland

From: Gary A. <[email protected]>

Date: Wednesday, June 8, 2011 12:12 AM

To: Mike Oliver <[email protected]>

Subject: Re: communication devices advice

Size: 6 KB

Hello Mike,

It's good to hear from you! Thank you for being interested in the

AmpliRider. I am very honored that you would consider this amp to hep combine

some of the devices into a single output.

If you plugged the AmpliRider's output into the JMCB2003's AUX input jack then

that would enable you to mix three inputs through the amp and into that AUX

jack.

You could plug the Zumo, Adaptiv detector, and iPhone (or the MP3 player) into

the amp and this should all work great.

I should mention though, I believe the Adaptive (like Escort, Valentine, and

Bel radar detectors) would need to pass through an isolation transformer in

order to make them compatible with the AmpliRider. This is because it doesn't

have a typical three wire stereo output (left,right,ground), but a mono

ungrounded one instead.

These devices will both work fine connected directly to a speaker but not when

plugged into a conventional amp. I noticed that other companies who build amps

for motorcycle riders have faced this problem too. I offer these isolation

transformers built into a cable for a parts only cost of $15.

The AmpliRider is being offered directly for the price of U.S. $65 and this

already includes the cost to deliver the amp to your address in Metairie by

fully insured, Airmail shipping.

Well keep in touch and let me know what you think Mike. If you have any

questions I will be glad to help you. Thank you once again for being interested

in this amplifier.

Have a nice evening Mike!

From: John A. Brown <[email protected]>

Date: Tuesday, June 7, 2011 3:40 PM

To: [email protected]

Subject: Re: communication devices advice

Size: 3 KB

Hi Mike... that's a lot of stuff! The difficulty I see is

the J&M CB and Zumo/iPhone combo. The problem being: the J&M headset is

needed for the CB, but won't work with the Zumo and the Zumo/iPhone

combo needs one of the BT headsets but won't work with the J&M headset.

The Mix-It2 would combine your TPX (via headphone jack) and MP3 signals

to the J&M. It might be a good start to inquire with J&M about

combining an iPhone/Zumo with their CB - they have the mic and speaker

already, maybe they have a way to integrate those devices also?

John

For some reason I'm not seeing the pictures.

double check you are logged in

 

[Harald]

For some reason I'm not seeing the pictures.

I can't either, but it's due to the firewall here at work that blocks picture downloads from many sites like photobucket. All I get to see are little boxes with red X's in them. :angry: Not sure if that applies to your situation.

 

[puppychow]

My Valentine 1 remote control box is hooked up to the Amplirider without any isolation cables. Works fine. The V1 remote control box has a stereo output line in the front and an mono output line at the back of the box. I used the stereo out line. I passed the output of the amplirider through a Kensington inline audio filter. I get virtually no static or ignition or ground noise.

 

[Patriot]

it occurs to me I'm abusing TMC's informative thread and the efforts he has made with his circuit and advertising it to all of us.

I offer my apologys and maybe it's obvious I should, at least, create a separate thread

 

[Patriot]

I've been mulling over this in relation to purchasing an amplirider or what would work cheap frugally putting all audio into my J&M system and headset.

Today, I purchased all the parts and had it put together to troubleshoot test the mixer with my Adaptiv TPX mono RD, MP3, and Zumo 550.

Well, in addition, I purchased the suggested Kensington inline audio noise filter (Amazon $13) recently which was needed to 12v car charger charge my MP3 while riding and listening.

I also went ahead and purchased from Radio Shack for putting between the mono aux out of the radar detector and the sterio in of the mixer the following:

1/8" / 3.5mm Mono Male to

1/8" / 3.5mm Stereo Female Adapter $2.89

that way, I was sure to get sound to both speakers of the headset

Haven't gone riding with it all yet, but will soon and report

A BIG THANK YOU...

 

[tcfjr]

After trying a Mixit2 and an Amplirider, I've been running a variation of this project from an older Forum post for almost 3 years, and love it. I mix my Zumo and V1 audio into a single output jack; the box sits under my seat.

I really works well, and the price was definitely right.

 

[Bounce]

does anyone know something/enough about the J&M JMCB2003 CB system ???

no, but i know something about J&M. back channel if ya want.