Adding sub whilst keeping Mac

[tehx]

By 5 cables, do you mean 5 x Balanced audio channels (remember 1 balanced channel has 3 wires; +, - and ground) or
5 wires, which would probably be a + and - for one channel and another + and - for a second channel the fifth wire would be a common ground.

[cpitts]

Nah, 5 separate channels. (4 x 3 wires (F + R) + 1 x 2 wires (sub seems to be unbal))

The diagram you've given makes sense for the basic conversion.

But given the possibly unclean signal in the shield wire, why not ground it out first to clean it up? Admittedly, you're instantly heading toward a more complex Bal to UnBal cct. Surely there's that simple setup as it won't require amps, unlike an unbal to bal which needs power and the amp.

Here's the schematic of the plug:

[tehx]

Cheers for posting the HU diagram mate! Ok, so would I be right in assuming this diagram shows the back of the MAC and the terminals / plugs, that directly feed the speakers?

If this is the case then you don't have a balanced transmission system as there is no summing amp on the speaker end to effectively remove noise in the transmission line. The GND is just there to provide some shielding for the cable. The + and - refers to the way the speakers are connected, thus the direction the speakers are driven in. Reversing the + and - will cause the speaker to pull, when it should push and visa versa.

If however these outputs (from the HU) feed an amp (or number of amps) then this would be a balanced transmission system and the schematic would work.

[cpitts]

Nup, that's the plug side of the amplifier. So the round cable is the DIN in (from the HU) and the rectangular Subaru/Clarion plug is the loom side of the amp (out to the speakers).

[tehx]

Also, its best to only ground at one end, keeping a consistent place for grounding across all wiring. By that I mean if its grounded at the HU then all separate runs of wiring should be grounded at the HU and the other end should not be grounded. This will eliminate earth loops which are a big cause of hum.

To reduce hum in an unbalanced system you can use the same wire you would use for a balanced system (two conductors and a shield) by:
*Connecting one of the wires (the same coloured one eg, red) to the centre pin of your RCA, at both ends.
*Connect the other wire (eg, black) to the sleeve at both ends.
*Connect the shield to the sleeve at only one end

Note: This only works if both sides of the cable (devices on each end) are unbalanced. For balanced to unbalanced see the schematic in a previous post.

The most common rule I have come across in the Broadcast industry is to connect the shield at the patch bay end or equipment end if you don't have patch bays installed. Just make sure you keep the same system in place for all wiring.

[tehx]

Cool - cheers for clearing that up. Ok so the bal to unbal circuit (2 resistors) would work across any of the MAC's balanced o/p channels to an unbalanced AMP.

There would be no problems in leaving the MAC AMP to say power the rears and install a separate amp (unbalanced) for the fronts. Just disconnect the wiring (for the front channels) from the MAC's balanced amp, use the resistor network to make those channels unbalanced, then connect to your unbalanced amp to these.

[RAN94A]

lol so now that you guys both understand each other.. you've totally confused me

im sorting of thinking from reading what you've both said... if i wanted to replace and amplify all speakers in the car.. i would require multiple jaycar converters... where as if i wanted to simply replace the amp and the sub.. i would only need one???

is this correct?

[cpitts]

The outputs on the amp will be speaker level - No need to do any conversion if you're going to line level into another amp, just cut and crimp into the next amp.

Yes, doing the simple resistor Bal to Unbal on any of the lines coming out of the DIN cable _should_ make them acceptable to a 'standard amp' with unbal inputs. Btw, with the resistor conversion, how do you find the SQ as a result? Does it damage the signal at all???

And RAN94A,
Leave all your speakers as they are.
Deaden the front doors properly.
Deaden the rear pacel shelf.

Figure out if you _really_ need more power. My system has those mods and it's quite loud now at vol 15 of up to 40 from the Mac and SQ is really quite good with the stock speakers (not that I have them any more), but at least the amp isn't my limit for noise.

[tehx]

The SQ (sound quality?) as such remains the same; just instead of being at +4 (the standard for balanced) you are at -20 (the standard for unbalanced). The resistor network uses a series resistor (R1) and a shunt resistor (R2) to create an attenuator or 'pad' as it's commonly called.

This circuit is exactly the same as a volume pot only the level of attenuation is fixed by the fact that you are using set value resistors. Its like gluing your volume pot in a fixed position. In this case we want +4 to be -20, all the time, so no need make it variable. Control over the volume is driven by the HU's volume control.

A completely balanced system will always sound better particularly in a noisy environment. Adding the attenuator (going to unbalanced) will be no different to using an unbalanced HU in the first instance. If I were to completely replace the Amp I would certainly be looking at replacing it with a balanced one as we have the luxury of balanced O/P's on the MAC. If I had an existing unbalanced AMP, that I found worked well, I would just be installing this with the unbalanced pad and saving some $$. Likewise if a balanced amp costs heaps more, the $1 pad and a cheap unbalanced amp will suffice. Just depends on how pedantic you are about your sound.

It would be good to get some feedback from people who have tried an unbalanced amp. I wonder if Subaru had problems with noise, so they used a balanced system or it's purely being used because it’s the 'premium' system. I suspect the later. If unbalanced works with no noticeable noise, then why pay more for something that's not going to give you any noticeable benefits.

Typically balanced systems are used in studio's where there is lots of equipment generating noise, long cable runs and multiple points of earthing. In the mastering process you want the best possible SNR (signal to noise ratio).

Bit of background: In a balanced system we take the signal at + then invert it and put it on the - so your signal at either + or - will be 180 degrease out of phase to one another. A summing amp at the other end sum's the + and - ( - is inverted as it is fed into an inverted i/p) and the end result will be your signal again (at twice the amplitude). Any noise that is introduced into your transmission line (cable) will result in the same phase (of noise) on both + and - so the effect of the summing amp is to cancel out the noise. In an unbalanced system there is only one signal (the + if you like) so this is why we only place the 'pad' across the + where it will be in phase. The - is not needed.

Thumbs up to noise dampening – good to hear some RL feedback on the results of this too mate. I will be starting here too yea.

[tehx]

RAN94A to answer your question. I assume you want to just add a bigger sub and therefore you need a bigger Amp yea?

If this is the case you have three options - first take a look at the HU diagram cpitts kindly posted.

a) You have an unbalanced amp (the every day amp you see in car stereo systems) and want to connect your MAC to the Amp via the line level inputs (on your amp)
- Take a look at the HU diagram, the round type connector (J101), that connects the MAC to the Amp
- Pin 1 (Woofer -), Pin 2 (Woofer +) and Pin 3 (earth).
- Use the balanced to unbalanced schematic and apply this to these outputs.

b) You have an unbalanced amp and want to connect your MAC to the Amp via the speaker level inputs (on your amp)
- Take a look at the HU diagram, the square type connector (J102), that connects the Amp to the speakers
- Just take pin D to the amp's + and
- pin L to the amps -

c) You have a balanced amp and want to connect your MAC to the Amp via the line level inputs (on your amp)
- Take a look at the HU diagram, the round type connector (J101), that connects the MAC to the Amp
- Pin 1 (Woofer -), Pin 2 (Woofer +) and Pin 3 (earth).
- Wire these to your new balanced Amp: + to +, - to - and gnd to gnd.

If you want to replace all speakers etc just follow the above guide & replace Woofer with whatever speaker you are working with. The three options A, B and C can be followed for every speaker, depending on how you are feeding / connecting your amp(s).

Oh, and no don't bother with the Jaycar Kit. Unless you have tried the 'pad' circuit and found too much noise. Then, you need to be sure the noise is being introduced in the cable run (not amp or HU), only then you may want to think about the Jaycar Kit.
Hope this helps

[Ric]

Edit: This circuit is for a line level (+4) balanced system. Not for speaker wiring (eg. from amp and or HU to speakers)

A better way would be to use both sides of the unbalanced signal to drive a small coupling transformer. You would need five, one for each signal.

You could probably use five of these: http://jaycar.com.au/productView.asp?ID=AA3085
or make up a circuit board with five of these: http://jaycar.com.au/productView.asp?ID=MM2534

[cpitts]

w.r.t SQ (Sound Quality) and noise levels in the base system:

Deadening:
- Deadening the doors properly has SIGNIFICANTLY reduced transient and reflected noise.
- This includes issues such as:
-> resonant bass through the doors
-> resonant mid-bass disruption/cancellation due to internal door cavity reflection
-> high frequency reflection/loss
- Proper deadening gives you a nice flat frequency response right across the spectrum
- Factory speakers still have 'that hiss' but it's drastically improved upon as the reflected portion of it is elimintated.

Replacing front door speakers:
- Removing all factory speakers from the front doors (3 per side - left the above door tweeter in place, just disconnected it)
- Along with the factory speakers were the capacitor freq clamps on each speakers +ve input
- Removed all factory mounting for these speakers (all the plastic mounts)
- Clamped (version 1 remember, proprer cable is installed ready for use when amp is upgraded) signal from the bass unit on the door (seemed to be only signal not frequency clamped!)
- Installed a new 3 way set of speakers and MDF (for bass) and timber mounts (mid/tweet)
- Installed 3 way cross-over network to work with speakers

The result is a clean, noise/hiss free setup on the front with very good, clean sound. The hiss/noise comes from the very poor capacitor network used. Not the head unit, amp or cabling.

[tehx]

Ric's suggestion is a better solution yes! I had a whole box of ex telstra line isolation transformers I put in Jiffy Boxes when I was doing concert / broadcast events using bal to unbal systems and needed line isolation from a passive device.

Me liks yr blog cpitts - the detail in car detailing - unreal! I like the before and after pics - can hardly tell the difference lol. Be sure to PM me if you sell your wheels, thats gonna be one 'pre loved' ride for sure! The paint looks better than when it rolled off the shop floor I bet it sounds a whole lot better too yea.

Must admit a have a new respect for the MAC after seeing the wiring - first time I have encountered a balanced system in a car. It's also good how the main amp is not part of the head unit.