Stereo to 5.1 hafler matrix decoder

[Nordic]

Hey guys, you may have seen that I was working on a veroboard version of Rod Elliot's hafler matrix circuit...

Main goal was to go from stereo to 2.1 without an active crossover... (will do a decent one when I can some day)

I completed the prototype yesterday.
And got the guts together this morning after a few greenies to go plug it in.

I have so far tested the Subwoofer output, and the main Left and right, (the missus is watching a movie now, so I can only test the rest later).

But so far I can confirm, that I can hear no noise added to the main stereo channels, and that the sub output works as specified.... i.e. clean summed output of 2 channels, without crossover attenuation, ready to plug into any commercial sub.

I used NE5532 (hope thats the right no., for the dual one),
it is the first circuit I made with an opamp,
it is the first circuit I made with voltage regulators
And it all works perfectly, you should have seen me pump the air.

I have only one concern, that when I turn the pot for the centre channel level too far, the DC offset on that channel goes from 2.odd milivolt to -15V.... (could this be beause I tested with open inputs)

I will query this with Rod in the next week if it is possible... not connecting a speaker to that one until I know what's up.

DC on the 2 rear channels seems perfectly ok, about 3mv each, at least DC offset for all channel pairs is exactly the same. Just wating for the wife to finish watching her movie, then I'm going to test those 2 channels....

The original Veroboard layout I published has a small error
I attach a corrected one, and will later add the PSU part when I'm less stoned.

basic BOM is as follows
HAFLER:
1 dual opamp (NE5532)
1 x IC socket (for future upgrades)
6 x 100k 1% resistor
4 x 100R 1% resistor
2 x 100uf electolytic caps
get 20 or so pcb mount faston connectors you never want to lead wires offboard directly from veroboard (unless you use solid core)
Some 22awg wire.

PSU:
1 x 2x12V 50VA tranny
1 x 2A+ bridge regulator
2 x 1000uF electrolytic caps
1 x 78L12 regulator
1 x 79L12 regulator
2 x .33uf bypass caps
3 x .1uf bypass caps

Add snubber caps to taste

Please refer to the original schematics when doing the veroboard as you will need to check where to connect the pot, and wich two pins to short on it.

http://sound.westhost.com/project18.htm

[Nordic]

Oi sorry haven't had a chance to get to this again... but I got some feedback...

Firstly an excerpt from my message to uncle Rod.

There is no PCB available so I did it on veroboard (hope it doesn't anger the gods of hifi).
Everything checks out fine, and I have connected all channels to output devices except the centre channel...

The problem is that DC offset on the centre channel climbs quickly as you turn the pot... goes from nearly negligible to -15V, is it because I had nothing on the input? I was scared to short the input... most likely everything works, but I'd hate to blow an amp on that channel simply because I didn't ask about this. Did I read the circuit correct in that the wiper pin of the pot connects with a short to the pin that is connected to ground? I'm never sure how to read diagrammes for pots, even my main amp's volume control is the wrong way around..... at least I'm sure of that.
I got the pin on the 5 o clock position of the pot connected to ground on the hafler...

Rod replied as follows (WOW its a real person!!!!!!!!)

The hi-fi gods are unlikely to be offended by your use of Veroboard, but
you have probably annoyed the gods of something else ;-) It sounds like
you either have incorrect wiring (such as the 'bottom' of the pot going
to negative supply), or considerable leakage on the board.

You read the circuit perfectly, but there is a connection of some kind
between the input resistors and the -ve supply.

I will check this out this afternoon, maybe he is right, I am pretty sure I checked it out real well though. I will do the veroboard layout for the PCB on PC then too... I want to try sticking some more caps on there, as you can see it was realy minimalist.

It also seems strange that it doesn't destroy the opamp if this is the scenario.

Think I will redo the layout for the veroboard on the PC and see if it comes out the same as last time.

Cheers
Nico

[Wynand]

Nordic...

Please keep me posted on your progress. I was looking for something like this too

Will you share your final vero layout? Ps Good Luck!!

[venki]

Please try cleaning the Vero board with the PCB cleaning soln to remove any solder flux. This might help, I had similar problems with the vero board (Which I mostly use). Use a Brush (I use old tootbrush ) to clean .

By the way best of luck for your project. I have tried this before (Dolby simple surround).

Venki.

[Nordic]

I am short on some RCA sockets, and will be a bit broke till the weekend, as I believe my wire finaly arrived from the UK.

Then I will rebuild it, on a new layout I just completed

I need to get to someone with a digital camera to take pics of the mechanical construction of the PSU too.. I think I was pretty clever with the connection to offboard wires... difficult to explain but a picture would do the trick...

I am not too worried about the other channels right now though, all I wanted was a cheap way to connect a DIY sub, and this it does ever so well...

Something else I need to spend some time on is the lowpass filter for this sub...thinking of crossing over at about 80Hz, my sub is good down to about 50Hz, at this stage... Its a Blown Yamaha SW-105 driven by a cheap PC speaker's sub amp and crossover, lol, probably pushes 10Watts through the speaker at max, and quite frankly this is way too much for my room size...turn it down, and it blends right in. I think a good sounding 50W sub will hit the spot just right, provided you never turn it up too much...

Hell Wynand I can do one better and come and show you some time... just got to wait for it to get less hot.

[ThinkCalvin]

That looks sweet

[Nordic]

Worth a shot, I promise, I mean its probably 2 dollars in components...

[lineup]

Originally posted by Nordic
Hey guys, you may have seen that I was working on a veroboard ....
I completed the prototype yesterday.
And got the guts together this morning after a few greenies to go plug it in.

The original Veroboard layout I published
..............

Please refer to the original schematics when doing the veroboard
as you will need to check where to connect the pot, and wich two pins to short on it.

http://www.diyaudio.com/forums/attac...amp=1137318228

Nordic,
Veroboard Rules!

Have to go buy me some veroboards.
Fast and easy way to try your circuits and ideas.
And even good for building your true stuff.



There is way too much fuzz going around about making PCB,
in my opinion.
Most components are not smart enough to know
if they are on a veroboard or somewhere else.

What software can I use to make veroboards layouts like yours?

[Nordic]

Google for Lochmaster

[lineup]

I found lochmaster.
LochMaster 3.0
It is not free.
Is the demo version any useful?