Coaxial vs RCA in audio

[TLS Guy]

I took it that the F7 is the external unit, but external to what I'm not sure as he didn't answer my query on that point.

I am not sure what he is asking.

What he has is a phono amp with a DAC. I am not clear if he has an external DAC as well.

However his FiiO unit converts all analog inputs to Digital before any processing. Then there is a unit that balances both left and right inputs, and then it goes to a balanced volume control, then a buffer amp and then to a balanced headphone amp. It has both balanced and unbalanced headphone outputs. There is also RCA line outs for connecting to a power amp.

So if you have a legacy analog device there are analog line ins, but they go to the DAC. So only native analog units should be connected to the analog line ins, and equipment with digital audio outs should use the digital inputs.

That is as simply, as I can explain it.

 

[lovinthehd]

I am not sure what he is asking.

What he has is a phono amp with a DAC. I am not clear if he has an external DAC as well.

However his FiiO unit converts all analog inputs to Digital before any processing. Then there is a unit that balances both left and right inputs, and then it goes to a balanced volume control, then a buffer amp and then to a balanced headphone amp. It has both balanced and unbalanced headphone outputs. There is also RCA line outs for connecting to a power amp.

So if you have a legacy analog device there are analog line ins, but they go to the DAC. So only native analog units should be connected to the analog line ins, and equipment with digital audio outs should use the digital inputs.

That is as simply, as I can explain it.

Didn't see any mention of a phono stage. He mentioned a cd player.

 

[TLS Guy]

Didn't see any mention of a phono stage. He mentioned a cd player.

His unit does not have a phono stage. I think he was asking the question of if he should use the CD analog outs or the digital. However this guy seems incapable of posing a question intelligently.

If the above is what he is asking then, he should use a digital connection to his headphone amp.

 

[Ivan Ferdinand]

I took it that the F7 is the external unit, but external to what I'm not sure as he didn't answer my query on that point.

Yes, the external unit i meant is the fiio k7.

Look, I want to connect my cd player to fiio k7, and want to use the dac and the headphone out of the k7. What connection do i need?

@TLS Guy

 

[TLS Guy]

Yes, the external unit i meant is the fiio k7.

Look, I want to connect my cd player to fiio k7, and want to use the dac and the headphone out of the k7. What connection do i need?

@TLS Guy

You did not tell us what CD player you have and what connections that has. It takes two to tango buddy. You are parsimonious with your information in the extreme.

If it has an optical or RCA out you need to use either one.

 

[DIBstangguy]

Wow!

 

[highfigh]

RCA is an analog output...it has been processed already by the DAC in your cd player. Your amp doesn't need to do anything.

Coax and optical are pure digital outputs, they bypass the the DAC in your cd player and will use the DAC in your amp.
That is the only reason they are there....to use a different DAC. They are not "higher quality" outputs.

S/PDIF is the digital coax output/input and it usually uses cables with RCA plugs.

 

[highfigh]

If you have problem write a decent answer because is a waste of time then delete your profile here and go wash dishes do something useful if being here is waste of time

Lighten up, Francis! You're the one who came here for answers after NOT reading their manuals.

 

[JerryLove]

It's fiio k7. It has coaxial/optical/usb digital input. I'm just confused whether these digital connection can "activate" the fiio amp as a headphone amp to a cd player. (i want to use the headphone out). Because those are "digital cable" and amp need "analog cable", or maybe I'm just misinterpreting something here. Am i?

You have a USB input. This accepts a digital signal from a source (computer? Phone?) to the K7
You have an optical input. This accepts a digital signal from a source to the K7
You have a coaxial electrical input labeled "coax". This accepts a digital signal from a source to the K7
You have two coaxial electrical inputs colored red and white and labeled "in". These accept single-channel (each) analog signals from a source.
You have two coaxial electrical inputs colored red and white and labeled "out". These provide single-channel (each) analog signals to send to something else (like an AVR).

The digital inputs are interchangeable (there may be some nuance around protocols on USB, but the two others have identical data simply sent over different physical media. These are what you should be using. They use the DAC on your K7 to convert to analog.

The analog inputs are there mostly as legacy. You use them if there's something in your chain with no available digital out. I suppose you could use them if you needed to bypass the K7's DAC for some reason, but no reason comes to mind.

 

[JerryLove]

S/PDIF is the digital coax output/input and it usually uses cables with RCA plugs.

Both the optical and RCA digital connectors are S/PDIF. One uses electrical signals and the other optical; but data packets are the same.

Perhaps that's what you meant and I just didn't parse correctly your statement.

 

[highfigh]

Both the optical and RCA digital connectors are S/PDIF. One uses electrical signals and the other optical; but data packets are the same.

Perhaps that's what you meant and I just didn't parse correctly your statement.

Thanks- I was really responding to "RCA is an analog output" but the additional info re: optical and digital coax being S/PDIF is always good, to add clarity.

 

[Audiophile Heretic]

Either cable can be used to transmit digital or analog signals.

The S/PDIF digital coax cable with RCA connectors transfers a high frequency digital data signal. Digital coax cable should be 75 ohms characteristic impedance terminated with 75 ohms resistance on each end, which is provided by the sending and receiving devices. Digital coax cable is not the same as standard analog coax cable with RCA connectors. Most times you can get away with using analog coax cable to transfer digital audio. The signal is digital data, so the sound quality is determined by the DAC that decodes the data to analog audio.

Analog coax cable with RCA connectors is terminated with low output impedance 100 ohms to 1000 ohms on the source end and high input impedance 20 kohms to 100 kohms on the destination end. Analog audio frequencies 20 Hz to 20 kHz are very low in comparison to digital data, so cable characteristic impedance is usually inconsequential.

 

[Audiophile Heretic]

Chip DAC in cd is 24 bit 192 kHz and if cd player is optional with SACD then his DAC is 32 bit 192 kHz or more the same is with pictures resolution 1080 p picture will look better and a bit sharper on 4K TV instead full hd TV with the same resolution

The sampling rate and bit depth of the digital audio signal carried by the digital audio cable is determined by the digital data stored on the media, not the specs of the DAC in your media player. The DAC in your media player does not process the signal carried on the digital audio cable. I have not heard of any media players that upscale the digital audio signal. I don't believe you can hear a difference between digital audio cables because they don't change the data that they transfer. The DAC that decodes the data to analog audio determines the sound quality. The DAC converting the digital data to analog audio can over-sample and interpolate to produce additional samples to reduce the need for analog filtering. There is where you may hear a difference between the DAC internal to your CD media player and the DAC external to your CD media player.

Now that I think about it, I do own an optical disk media player that will convert SACD DSD to PCM of selected sample rates to drive external DACs that are not capable of decoding DSD audio on HDMI. I consider this a downgrade of the original digital data signal, but I doubt I can reliably hear the difference.

 

[Audiophile Heretic]

I apologize for some less than cordial remarks of some of the Audioholics members who have replied to your original post. I know that Internet forums are filled with trolls waiting to pounce, but that doesn't mean it is acceptable.

 

[Audiophile Heretic]

everything goes through the DAC

DAC is Digital to Analog Converter. If you use the RCA analog outputs of your CD player, the digital data stored on the media is converted to analog by the DAC internal to your player. If you use the RCA S/PDIF coaxial digital output of your CD player, the digital data is not converted to analog by the DAC internal to your CD player, the digital data is passed on the cable to some external DAC downstream for conversion to analog.

 

[Audiophile Heretic]

but what about signal data throughput which cable will carry more information I know already the coax can deliver max 24 bits up to 192khz but what about RCA ???is a analog cable with different signal he can deliver high resolution like that?

This is not really a valid question. There is no concept of "resolution" of an analog audio signal. The analog audio signal has bandwidth that is audible frequency response from some low frequency such as 20Hz to some high frequency such as 20kHz plus or minus some tolerance in dB (which doesn't tell what frequencies the peaks and dips are at, so it doesn't completely describe the sound quality) with some noise level and some distortion level % THD and % IMD. You could argue that the resolution of the analog signal depends on the resolution of the original digital data on the media, which determines analog signal frequency bandwidth and noise and distortion levels. It does not depend on the maximum bandwidth of digital data cables. The bandwidth of digital data cables must be sufficient to transfer the digital data signal. The DAC must be able to decode the PCM or DSD sampling rate and bit depth format encoded on the media or transmitted by the cable.

I should note that S/PDIF optical and coaxial digital audio cables can only transfer PCM digital audio, not DSD. DSD digital data transfer for consumers requires either HDMI or USB cables. The maximum sampling rate and bit depth resolution of PCM optical and coaxial digital audio connections varies between manufacturers and devices, but usually tops out at 192kHz 24bit. Higher resolutions require HDMI or USB. USB connections can be made to the DACs in some CD players, DACs, amplifiers, and AVRs. Some USB connectors allow connecting flash media or SSDs to media readers. Some USB connectors allow computers to send data to DACs.

 

[isolar8001]

Any particular reason you are trying to stir up someone that hasn't posted for a few months, by responding to a post from 3 months ago ?
Surely you have something better to do on a Saturday afternoon.

 

[TLS Guy]

The S/PDIF digital coax cable with RCA connectors transfers a high frequency digital data signal. Digital coax cable should be 75 ohms characteristic impedance terminated with 75 ohms resistance on each end, which is provided by the sending and receiving devices. Digital coax cable is not the same as standard analog coax cable with RCA connectors. Most times you can get away with using analog coax cable to transfer digital audio. The signal is digital data, so the sound quality is determined by the DAC that decodes the data to analog audio.

Analog coax cable with RCA connectors is terminated with low output impedance 100 ohms to 1000 ohms on the source end and high input impedance 20 kohms to 100 kohms on the destination end. Analog audio frequencies 20 Hz to 20 kHz are very low in comparison to digital data, so cable characteristic impedance is usually inconsequential.

The spec for analog RCA is 50 Ohm, and digital 75 Ohm. In practice if you use an analog cable for digital the error rate will increase due to more reflections. However the error rate is usually well within the ability of the error correction so you won't notice. Error correction completely restores that data within significant limits. If the error correction is exceeded there will be drop outs or pops.

 

[Audiophile Heretic]

The spec for analog RCA is 50 Ohm, and digital 75 Ohm. In practice if you use an analog cable for digital the error rate will increase due to more reflections. However the error rate is usually well within the ability of the error correction so you won't notice. Error correction completely restores that data within significant limits. If the error correction is exceeded there will be drop outs or pops.

I don't believe that the spec for analog RCA is 50 ohm. Justify your claim. There is no spec for analog audio cable characteristic impedance. The wavelengths of analog audio signals on cable are between 9 and 9,000 miles.

I agree with your statement about error correction compensating for reflections on cable that is not the correct impedance. Don't digital audio devices also attempt to interpolate values if error correction is exceeded?

 

[isolar8001]

Surely you have something better to do.