SPDIF out - good idea ?

Bernhard · 30th September 2007, 11:19 AM

In a Yamaha player, the output of the digital transmitter IC is connected to 4 parallel ( in-in-in-in out-out-out-out ) 74HC04 inverters via 1 k ohm. On the output there is a 220p cap to ground. This is coupled via 47 ohm and a cap to the output transformer.

That causes the irregular SPDIF square to look like an irregular sawtooth on the input of the inverters.

Any opinions on

- feeding inverters with a sawtooth signal ?
- using parallel inverters ?
- using inverters instead of NAND gates ?

Another Yamaha player with the same digital transmitter IC but 3 parallel 74HC00 Nand gates sounds very different on it's digital output.

rossl · 1st October 2007, 03:51 PM

You can try removing the 220p to ground. I'm not sure why it is there. It may have been put there to solve a EMI emissions requirment.

30th September 2007, 11:19 AM	#1
Bernhard diyAudio Member Join Date: Apr 2002 Location: Munich	SPDIF out - good idea ? In a Yamaha player, the output of the digital transmitter IC is connected to 4 parallel ( in-in-in-in out-out-out-out ) 74HC04 inverters via 1 k ohm. On the output there is a 220p cap to ground. This is coupled via 47 ohm and a cap to the output transformer. That causes the irregular SPDIF square to look like an irregular sawtooth on the input of the inverters. Any opinions on - feeding inverters with a sawtooth signal ? - using parallel inverters ? - using inverters instead of NAND gates ? Another Yamaha player with the same digital transmitter IC but 3 parallel 74HC00 Nand gates sounds very different on it's digital output.

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1st October 2007, 03:51 PM	#2
rossl diyAudio Member Join Date: Nov 2004 Location: Central Ohio	You can try removing the 220p to ground. I'm not sure why it is there. It may have been put there to solve a EMI emissions requirment.