Hi.
SPDIF transformer breaks ground loop, but can it distort the digital signal? For example PE-65612NL which I want to buy.
The second option is use Toslink, but in this in this topic is a lot of different opinions and I do not know if it is worth.
SPDIF transformer breaks ground loop, but can it distort the digital signal? For example PE-65612NL which I want to buy.
The second option is use Toslink, but in this in this topic is a lot of different opinions and I do not know if it is worth.
I bought a murrata RF 1:1 for one of my two SB Duet and lazy to implement it to an AB test (with ears)...
Some designs do not use it with sucess as the Subbu DAC.
If one transformer : position have to be nearer to the end of the line (source) than the beginning (streamer, player) or not important ?
Some designs do not use it with sucess as the Subbu DAC.
If one transformer : position have to be nearer to the end of the line (source) than the beginning (streamer, player) or not important ?
As it is not a must, just a good to have safety feature. 1 is enough where ever you like.
I prefer to put the trafo at the receiving end, after the termination resistor. The grounding is important as the S/PDIF link is a means of introducing CM noise into a DAC.
According to the datasheet the pe65612nl is only ok up to 96khz, but has anyone done tests? Murata is more expensive but doesn't have this (apparent) limitation. Lundahl also make a decent one too (more expensive again)...
The easiest solution is to leave for example one input without transformer, because PE-65612NL is up to 7mbps and 192kHz/24bit needs 9.216 Mbps.
192,000 (samples per second) x 24 (bits per sample) x 2 (channels) = 9.216 Mbps.
S/PDIF max bitrate? - AVS Forum
Unless someone checked this transformer with 192kHz/24bit...
192,000 (samples per second) x 24 (bits per sample) x 2 (channels) = 9.216 Mbps.
S/PDIF max bitrate? - AVS Forum
Unless someone checked this transformer with 192kHz/24bit...
Worth reading: The SB3/SPDIF output thread.......
PE-65612 measurement on page 2.
@elektryk
Yes, transformer can distort signal.
Leaking inductance, interwinding capacitance, line impedance, reflection coefficient (return loss) are keywords. And for 192k/24bit, you will need transformer with >100Mhz bandwidth.
In general, if you can't measure it, better leave it out of circuit, it will do less harm.
PE-65612 measurement on page 2.
@elektryk
Yes, transformer can distort signal.
Leaking inductance, interwinding capacitance, line impedance, reflection coefficient (return loss) are keywords. And for 192k/24bit, you will need transformer with >100Mhz bandwidth.
In general, if you can't measure it, better leave it out of circuit, it will do less harm.
I hope it is DA101C 😀
A lot of people don't have the knowledge to implement transformer properly.
A lot of people just don't care, all sounds the same to them.
But why are they building DIY audio stuff, if everything sounds the same??? 😱
Huh, to find a different, maybe better sound...
I was thinking about Ethernet transformers, but they are designed for use with twisted pair differential signal and has additional inductors.
http://i.imgur.com/Mi8SW4o.jpg
How would You propose to properly implement PE-65612NL?
Probably most often will work at 44.1kHz, 48kHz or 96kHz sampling frequency...
I was thinking about Ethernet transformers, but they are designed for use with twisted pair differential signal and has additional inductors.
http://i.imgur.com/Mi8SW4o.jpg
How would You propose to properly implement PE-65612NL?
Probably most often will work at 44.1kHz, 48kHz or 96kHz sampling frequency...
Hi we did not use an SPDIF transformer to keep cost down. Normally I always use those in DACs. I used a hardwired SPDIF transformer on one of my V3 test-DACs because of a GND problem with a specific source. No one can say we don't care, we do care. In many cases the transformers are not needed, especially if the transmitting source has one and one does not want to change the source. In other cases things work out OK without a transformer. Waveform etc. can be much better without transformer compared to using mediocre transformers. Subbu V3 also would need a 192 kHz capable one.
If there is one thing I would implement on a next version (if we would do that) is adding pads for a good SPDIF transformer like Newava S22083. Just to give the possibility for adding one if the situation of the user would ask for that.
BTW the tone of your post could be slightly less pedantic.
Last edited:
According to you : could it be better with a Squeeze-Box (so on the SB side).... say with a 15 cm true 75 ohms like I did. Do you use one with your SB ?
A RF transformer is less expensive than a Vishay SAL cap...
A RF transformer is less expensive than a Vishay SAL cap...
The problem I had was with a Squeezebox Touch if I remember correctly. The transformer should be at the receiving side so at the DAC IMO. I never used such short cabling. 1 meter is the shortest I have. There once was an experienced member here and I took his word for it that SPDIF cabling needed to be 1 meter or slightly more. He had the equipment to test that, I don't. He could also tell me that he washes his SPDIF cables in cola to make them perform better 😉 That is the risk of accepting information that you can't verify yourself.
We are talking about SPDIF transformers not RF transformers. It would help tremendously to use correct names and types on a public forum. It keeps us from confusion and misunderstandings. It does not matter that an SPDIF transformer is cheaper than SAL RPM (it is not as Newava S22083 costs around 6 Euro). It was a choice, just like using SAL RPM was as I had hundreds of them in stock so I could try out as much as I liked 🙂
To be honest I don't use my own DACs at the moment as I tested a DDX amp and stick with it for now. I can't comment on the Touch-V3 combination although my test-V3 with transformer was mostly used with this Touch. It simply can not all be remembered. As said, I would implement one now, I did not have Squeezeboxes when V3 was designed. You can use S22083 at the V3 PCB without problems. The primary side can be wired to a 75 Ohm BNC connector with the necessary passive parts.
We are talking about SPDIF transformers not RF transformers. It would help tremendously to use correct names and types on a public forum. It keeps us from confusion and misunderstandings. It does not matter that an SPDIF transformer is cheaper than SAL RPM (it is not as Newava S22083 costs around 6 Euro). It was a choice, just like using SAL RPM was as I had hundreds of them in stock so I could try out as much as I liked 🙂
To be honest I don't use my own DACs at the moment as I tested a DDX amp and stick with it for now. I can't comment on the Touch-V3 combination although my test-V3 with transformer was mostly used with this Touch. It simply can not all be remembered. As said, I would implement one now, I did not have Squeezeboxes when V3 was designed. You can use S22083 at the V3 PCB without problems. The primary side can be wired to a 75 Ohm BNC connector with the necessary passive parts.
Last edited:
jean-paul, sorry for misunderstanding, it wasn't aimed to you. It was aimed to people, modifying audio gear in all possible ways without basic understanding. And just sticking digital transformer in front will often cause signal degradation. Subbu V3 is fine DAC, I have hear it.
Last edited:
Ok, thank you for that. I will try the murata spidf 1:1 isolation transformer I have already as the Newava was not sourcable at Mouser. Gary send me some month ago a shematic to add a transformer for the Duet we both own. The axial SAL 3.3 uf cost me more than the Newava !
Well very different testimonies about lenght of spidf... My poor understanding with some Marce hints was finally shorther than one meter was said to be better on measurements. But don't know if difference can be heard between both. BTW too short is bad because i discover my Duets were sensible to the PS trafo of the Subbu.... Cost of expensive metal box aluminium or Fe is my limit... and certainly EMC measurement the limit of most diyers as Tools seem to be more than expensive for enthusiast diyers!
I tested two year ago a PowerDAC sold by HIFImeDIY .. very disapointed.... maybe needs some tweak but here as Big Ears said above, simple knowledge of simple diyers is a limit here ! Scope, need learn to read (I mean the language), etc... Not said to be as good as I read on some buzness hifi blogs !
Last edited:
Ah the metal box issue. One of the better advices for DACs is to encase them in a metal case contrary to popular belief that wooden cases are better etc. Wood sounds better indeed with analog stuff but lay your cell phone next to it and you will regret having used a wooden case. I reuse old cases of printer switches, network switches, old video camera chargers, etc. Just have a new front cover cut from aluminium, buy some good black epoxy paint and a bit of work and you have your metal case. I meticulously try to avoid connection of audio GND with PE (disclaimer: only do this when you are the only one operating your stuff, know your risks etc) and on power amplifiers then only the case is connected to PE and audio GND is "lifted: from PE. I always keep audio GND floating with DACs and sources. All connectors, be it SPDIF or L + R are insulated from the metal case. Again, only do this when you are a good craftsman experienced in shielding and in safe mains wiring. People that mount PCB's with 1 screw or melting glue type of DIYers should not try any PE-less devices and even 230 V AC wiring IMO. Safety is in details, not in a hurry to get things done.
Regarding DDX: I would be the first to criticize it if it was not good but I can not seem to be able to remove it from my audio rack. BTW it has an SPDIF transformer 😉
Regarding V3 and an SPDIF transformer: first try it out outside the DAC with a modified cheap 75 Ohm cable. Solder the cable to the transformers primaries and the BNC connector straight on the transformers secondaries at the DAC side. Keep connections short as possible and be wllling to sacrifice this transformer for science purposes. Check if the source has a capacitor in the output, if so you can omit a series DC blocking capacitor at the transformers primary side. A very small metal case around the "open" piece would be best. Measure the signal and check if it has become any better or worse. Then decide how to proceed. Don't let your ears be the first judge.
Regarding DDX: I would be the first to criticize it if it was not good but I can not seem to be able to remove it from my audio rack. BTW it has an SPDIF transformer 😉
Regarding V3 and an SPDIF transformer: first try it out outside the DAC with a modified cheap 75 Ohm cable. Solder the cable to the transformers primaries and the BNC connector straight on the transformers secondaries at the DAC side. Keep connections short as possible and be wllling to sacrifice this transformer for science purposes. Check if the source has a capacitor in the output, if so you can omit a series DC blocking capacitor at the transformers primary side. A very small metal case around the "open" piece would be best. Measure the signal and check if it has become any better or worse. Then decide how to proceed. Don't let your ears be the first judge.
Last edited:
PE of amplifier (CD player, etc) isn't problem, because a lot of factory construction doesn't use it, but almost every computer has and different devices may cause ground loop (and I think that transformer will be helpful here).
Is there any solution to compare quality of SPDIF signal with oscilloscope?
Is there any solution to compare quality of SPDIF signal with oscilloscope?
Just looking at the wave on the scope will give a good indication on whether it is good or bad, but do not try and form correlations between what the square wave will look like and the resultant analogue output because there is none.
As Julf as said above an eye diagram would give more information, these (eye diagrams) are best use with a template that will provide a reference for acceptable signal quality.
Even though you are using a transformer, a lot of noise from the SPDIF source is high frequency and this will often be coupled capacitivly either by the winding capacitance or by the layout so this is something else that needs to be considered. If the HF noise is a problem a capacitivly screened transformer (or better still a planar transformer) will help, or the addition of a ferrite to the incoming signals.
As Julf as said above an eye diagram would give more information, these (eye diagrams) are best use with a template that will provide a reference for acceptable signal quality.
Even though you are using a transformer, a lot of noise from the SPDIF source is high frequency and this will often be coupled capacitivly either by the winding capacitance or by the layout so this is something else that needs to be considered. If the HF noise is a problem a capacitivly screened transformer (or better still a planar transformer) will help, or the addition of a ferrite to the incoming signals.
To state the obvious: S/PDIF is a binary signal in that the transmitted data is either correct or it isn't. Every sample is parity checked; there are no shades of gray. S/PDIF is phase encoded. Ones and zeros are determined by the number of phase changes in a bit period. The wave shape and edges are irrelevant.
- Status
- Not open for further replies.