[mythtv-users] OT: Re: HDMI_SPDIF directly to reciever

[Alen Edwards]

James wrote:
> OTAlen Edwards wrote:
>>
>>
>> James Lockie wrote:
>>> Alen Edwards wrote:
>>>>
>>>>
>>>> James Lockie wrote:
>>>>> Brian Phillips wrote:
>>>>>  
>>>>>> I think I can say why yours is working correctly.
>>>>>>
>>>>>> Your signal is a purely electrical SPDIF signal.  Even though it's 
>>>>>> not
>>>>>> according to the -0.5 to +0.5 spec, it works because SPDIF is pretty
>>>>>> versatile.  I have driven SPDIF signals successfully with 0V to 
>>>>>> +5V swings
>>>>>> (not recommended, but it produces sound) and I have driven SPDIF 
>>>>>> signals
>>>>>> successfully with 0V to +250mV swings.  Again, not recommended but it
>>>>>> produces sound.
>>>>>>
>>>>>> Brian
>>>>>>     
>>>>> Am I risking frying my motherboard or receiver?
>>>>>
>>>>> _______________________________________________
>>>>> mythtv-users mailing list
>>>>> mythtv-users at mythtv.org
>>>>> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>>>>>
>>>>>   
>>>>
>>>> You certainly are risking frying the receiver.  If that goes, there 
>>>> is a small chance it could take out the MB.
>>>>
>>>> Build the network or buy the adapter.
>>>>
>>>> Allen
>>> Yamaha said my receiver expects 5 volts.
>>> ASRock never answered (that was a month ago).
>>>
>>> There is 0 volts on the RCA.
>>>
>>> Why do I get sound if there is a zero volt signal?
>>> I tested my voltmeter on a battery to verify it works.
>>>
>>>
>> You should read 0 volts with a S/PDIF signal.  They are 0 volts DC and 
>> the AC is too high a frequency for my and apparently your voltmeter to 
>> read.  If  you had a TTL signal, you would register about 2 volts with 
>> the VM set to DC.  If your RX expects 5 volts and your MB reads 0, I 
>> would guess it would work and you won't hurt anything (don't sue me, I 
>> can't pay anyway).
>>
>>
>> Allen
>>
>> .
>>
> I bought a new meter and it says 1.4V DC :-(
> I put a picture up at: http://lockie.ca/test/voltage.jpg but I doubt it 
> is very helpful.
> 
> So if my RX expects 5V (DC?) and it is getting 1.4V DC and I have sound, 
> do I need the circuit?
> TTL is +5V, and SPDIF is -.5 to +.5V so what is my MB outputting?
> 
> 
That is more like it.  This indicates that you have a TTL signal on the 
MB, as I do.  A TTL signal is going to go between almost 0 and something 
above 2 volts, let's say 3 volts.  The signal is going to be low (0 
volts) half the time and high (3 volts) half the time so the DC value 
will measure half way between the two or about 1.5 volts.  This is not 
an exact number but it is not 0 VDC, which is what you would measure 
with a spdif signal.

I would bet that your Rx expects spdif levels of larger than .2 volts 
and less than something.  You say it can take up to 5 volts, which again 
I would double check if I were you.  If that is correct, then you should 
be OK.

When I was faced with exactly this situation, I built the network.  I 
would not be worried about sending too little signal in your situation 
but rather double check that you are not sending too much.  It may be 
just fine, it all depends on the details of the circuits involved.

Allen