Stereo to Mono (was Re: TECH: Gorf)

[guddler]

[ukvac] Stereo to Mono (was Re: TECH: Gorf)
I thought on the subject of stereo to mono you could just get away with
splicing the two +'s together and splicing the two -'s together to join
the two channels - or is there more than that to it?

Guddler.
PS: Hadn't even considered the ranking lights as I have a mini-myte
which lacks them anyway :O)

----------------------------------------------
Martin White

http://www.guddler.com
Arcade search site with PCB info too...

 

[guddler]

RE: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
Define "a bit naughty"!

Does this mean "you can do it but it'll damage the pcb" or "you can do
it, it's not really the way you SHOULD do it, but in reality it'll be
fine"

:O)

Guddler.

----------------------------------------------
Martin White

http://www.guddler.com
Arcade search site with PCB info too...

> You can do it but it's a bit naughty. A better solution is to use an
> audio isolation transformer. You can get them in RS - something like
> this:

 

[zepromz]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
If you tap the signals before they hit the amplifier board, all you
need do is put a 10k resistor in series on each line, then combine
the outputs and send that to your mono amp.

LEFT CH ------////------
10k |------------- to amp
RIGHT CH ------////------/
10k

Grab the Gorf wiring diagram and follow the wires between the main
pcb rack and the amp board, the 2 audio lines are there to tap into.

At 13:41 21/09/01 +0000, you wrote:
>He he he.
>
>Generally, you shouldn't drive an amplifier backwards, you can blow
>it up (and no, i'm not going into the maths...I probably couldn't
>remember it anyway).
>
>You may be able to get away with it on an unamplified signal if
>there's some resistors in there somewhere to dissapate the load, but
>you may find it'll just buzz a lot.
>
>If you're doing it with an amplified signal, on the other hand...
>
>The best thing to do is have a look on some of the PCBs that have
>stereo output which can also be used mono - I recall there are
>several of these. See how they do it.
>
>D-Type
>
>

 

[guddler]

RE: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
Sadly I wasn't talking about doing this to a Gorf, I'm talking more
general, and in particular I have a board that needs it doing after the
amplification stage :O(

(Amplifier stage on-baord)

However, your info WILL be very usefull for the Gauntlet to Jamma setup
which is still ongoing... Cheers.

Guddler.

----------------------------------------------
Martin White

http://www.guddler.com
Arcade search site with PCB info too...

> If you tap the signals before they hit the amplifier board,
> all you need do is put a 10k resistor in series on each line,
> then combine the outputs and send that to your mono amp.
>
> LEFT CH ------////------
> 10k |------------- to amp
> RIGHT CH ------////------/
> 10k
>
> Grab the Gorf wiring diagram and follow the wires between the
> main pcb rack and the amp board, the 2 audio lines are there
> to tap into.
>
>
>
> At 13:41 21/09/01 +0000, you wrote:
> >He he he.
> >
> >Generally, you shouldn't drive an amplifier backwards, you
> can blow it
> >up (and no, i'm not going into the maths...I probably
> couldn't remember
> >it anyway).
> >
> >You may be able to get away with it on an unamplified signal
> if there's
> >some resistors in there somewhere to dissapate the load, but you may
> >find it'll just buzz a lot.
> >
> >If you're doing it with an amplified signal, on the other hand...
> >
> >The best thing to do is have a look on some of the PCBs that have
> >stereo output which can also be used mono - I recall there
> are several
> >of these. See how they do it.
> >
> >D-Type
> >
> >

 

[zepromz]

RE: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
At 17:50 21/09/01 +0100, you wrote:
>Sadly I wasn't talking about doing this to a Gorf, I'm talking more
>general, and in particular I have a board that needs it doing after the
>amplification stage :O(
>(Amplifier stage on-baord)

Not realy a problem, probe around the amp inputs on the board, cut the
2 required tracks and fudge the resistor "mixer" into the gap you just
made in the circuit. if you use 1/8 watt resistors, you can get it all in on
the back of the pcb. This is assuming you have a 1 or 2 sided PCB,
anything with 8 million layers will of course not work like this...

If you dont wish to cut tracks, your better off goin with Phils advice and
playing with transformers and the like.

 

[marog_uk]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
>Generally, you shouldn't drive an amplifier backwards, you can blow
>it up (and no, i'm not going into the maths...I probably couldn't
>remember it anyway).

If the problem with connecting the two audio outputs together is that you
get current going from one to the other in the wrong direction, couldn't you
just put a couple of diodes in series with the two outputs? If I remember
my school physics (which was a long time ago), I thought diodes only allowed
current to flow in one direction. How about something like this:

Audio Left Output -------- DIODE ----------

|---------Speaker
/
Audio Right Output ------- DIODE ----------/

Maybe it's a completely stupid idea.....but I thought I would ask.

Steve

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp

 

[zepromz]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
At 06:48 02/08/01 +0100, you wrote:
>I don't know if its the same?
> But here goes.... in car audio
>after amplification you can go down to mono by what is known as bridging .
>i.e by taking the + from one channel and the - from the other channel ,but
>this will give you a higher output, if the amplifier is rated at 5 watts RMS
>(stereo) the bridged mono output will be 10 watts,
> This is how car audio users go sub bass.

As long as they have an amp designed to go "tri-mode"

 

[pobtastic]

RE: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
I've got a question audio related.....

I was thinking of plumbing in a mono headphone jack next to the speaker on
the front of my supergun. Now, when you plug headphones into a TV or music
system the speaker 'cuts out' and just plays through the headphones. How do
I achieve this 'switching over' effect???

Answers on a postcard......

Thank you!!

Pobster

 

[cliff_poole]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
Steve,

Remember that this is an AC signal. If you connect a diode to it
you will just clip half of the waveform giving you tremendous distortion.
The easiest solution would be to replace the two diodes in your diagram with
two resistors as mentioned by someone else in a previous reply.

Cliff.

 

[P-Man]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
> I've got a question audio related.....
>
> I was thinking of plumbing in a mono headphone jack next to the speaker on
> the front of my supergun. Now, when you plug headphones into a TV or
music
> system the speaker 'cuts out' and just plays through the headphones. How
do
> I achieve this 'switching over' effect???
>
> Answers on a postcard......
>
> Thank you!!
>
> Pobster

well, what i can tell you is that every arcade board has the power to blow
your headphones. I don't know the precise specs, but arcade baords can put
out a max of anything from 4 to 12 watts. Now, bearing in mind the average
headphone max limit is probably about 500mw, i think one day you could have
your headphones plugged in, and an arcade board with a non-adjusted volume
pot, and *plink* there they go.

the alternative would be to put a resistor or two of the correct value to
limit what gets to the headphones. That's a quick and dirty fix, but i would
think that most sound amps would not like trying to drive such a resistance
and would probably pop too.

just my tuppence worth.

Andy

 

[pobtastic]

RE: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
Well, it was only a thought! )
That's pretty much all I needed to know really - that's its not worth
doing!!!
I have got another question too..... When I lived back in Clacton (not so
long ago) I explained the problem of outputting already amplified sound
through a scart lead into a TV (and consequently blowing the speakers) to
the guy in my local electrical store. He came up with the idea of buying a
'dropper' which takes the signal back down to line level and allows the TV
to re-amplify it itself. I never actually bought anything to go ahead with
the idea because I wanted to look further into it. Andy, you wrote - "most
sound amps would not like trying to drive such a resistance and would
probably pop too." Do you think that using a dropper would also cause
damage to the sound amp??

Pobster

 

[zepromz]

Re: [ukvac] Stereo to Mono (was Re: TECH: Gorf)
Using a resistor is the quickest way to do it. Most expensive headphone
adapter units for stereos without headphones use this approach.
Get down Maplins and grab a 10w wirewound / cement resistor of the
required value. 100 ohm is a good startin point.
Switching, could taken care of by a switching headphone jack.
Only problem is that you cannot combine the two easily.
The best bet would be to hardwire the output to the speaker, and also to
the headphone jack via a 100 ohm series resistor, and have a speaker
on/off switch in the circuit. You dont really need a circuit diagram do you?

At 15:26 23/09/01 +0100, Andy 99pman welburn wrote:
> > I was thinking of plumbing in a mono headphone jack next to the speaker on
> > the front of my supergun. Now, when you plug headphones into a TV or
>music system the speaker 'cuts out' and just plays through the
>headphones. How
>do I achieve this 'switching over' effect???
>
>well, what i can tell you is that every arcade board has the power to blow
>your headphones. I don't know the precise specs, but arcade baords can put
>out a max of anything from 4 to 12 watts. Now, bearing in mind the average
>headphone max limit is probably about 500mw, i think one day you could have
>your headphones plugged in, and an arcade board with a non-adjusted volume
>pot, and *plink* there they go.
>
>the alternative would be to put a resistor or two of the correct value to
>limit what gets to the headphones. That's a quick and dirty fix, but i would
>think that most sound amps would not like trying to drive such a resistance
>and would probably pop too.