[regal]

-10dB would give approximately 1/3 Voltage the input V so the reflection would be about 1/6,  still enough that the reflection would not likely be picked up by the receiver.
 
 
Another thing if we are doing these mods I think it makes sense for folks to open their DAC's and make sure the receiving end is 75 ohms,  its common practice for DAC makers to just throw on a BNC connector without the proper termination to the receiver.

 
Quote:

 

 

[mmerrill99]

Quote:

-10dB would give approximately 1/3 Voltage the input V so the reflection would be about 1/6,  still enough that the reflection would not likely be picked up by the receiver.
 
 
Another thing if we are doing these mods I think it makes sense for folks to open their DAC's and make sure the receiving end is 75 ohms,  its common practice for DAC makers to just throw on a BNC connector without the proper termination to the receiver.
 

Thanks for the correction - I thought I was off
Good advice, regal, but I wonder how many are up to the job of doing this, particularly the job of calculating the correct termination.
 
BTW, I could have done with your input on that idiotic thread over on DIYA where I was being accused of casting a slur on e'ee designers precisely on this point - that a lot of SPDIF receiver circuits were improperly terminated. He maintained that a DMM could measure the input impedance & he claimed to be an e'ee?? 
 

 

[regal]

Quote:

Thanks for the correction - I thought I was off
Good advice, regal, but I wonder how many are up to the job of doing this, particularly the job of calculating the correct termination.
 
BTW, I could have done with your input on that idiotic thread over on DIYA where I was being accused of casting a slur on e'ee designers precisely on this point - that a lot of SPDIF receiver circuits were improperly terminated. He maintained that a DMM could measure the input impedance & he claimed to be an e'ee?? 
 

He was probably fresh out of school with no bench or feild experience,  probably not a good school either.  I quit following the thread when he couldn't distinguish a question from a statement.
 
 
What I've seen for termination at the input side of the DAC is almost always a 75 ohm resistor in paralell if no transformers are involved, should be pretty simple (not as convoluted as the transport output side.)

 

[mmerrill99]

Quote:

He was probably fresh out of school with no bench or feild experience,  probably not a good school either.  I quit following the thread when he couldn't distinguish a question from a statement.
 
 
What I've seen for termination at the input side of the DAC is almost always a 75 ohm resistor in paralell if no transformers are involved, should be pretty simple (not as convoluted as the transport output side.)

Yes, full of the surety of his own opinion!
OK, it sounds do-able so.
How are the 1.8V & 5V mods going?

 

[regal]

Not good I built a great separate powersuply with umbilical cord and 5V & 1.8V but tried to fit the Hiface in a tiny separate box, The case I'm using is tiny and allows two 18650 battery holders to sit on top then I can plug it straight into my DAC with out a cable. But when I closed it up it put stress on the wires and one broke off and created a short, fried the DIT.  I'm going to put fuses inline with the batteries.  I need to find some very thin flexible wires.  The MCP regulator works great at supplying a 1.8V output from the 5V.  But I recommend ordering it in the SMD package to replace the silly stock buck regulator.
 
 
 
 
When you use a spearate 5V power supply I imagine you still have to connect it to the USB ground?
 
Quote:

Yes, full of the surety of his own opinion!
OK, it sounds do-able so.
How are the 1.8V & 5V mods going?

 

[mmerrill99]

Quote:

Not good I built a great separate powersuply with umbilical cord and 5V & 1.8V but tried to fit the Hiface in a tiny separate box, The case I'm using is tiny and allows two 18650 battery holders to sit on top then I can plug it straight into my DAC with out a cable. But when I closed it up it put stress on the wires and one broke off and created a short, fried the DIT.  I'm going to put fuses inline with the batteries.  I need to find some very thin flexible wires.  The MCP regulator works great at supplying a 1.8V output from the 5V.  But I recommend ordering it in the SMD package to replace the silly stock buck regulator.
 
 
When you use a spearate 5V power supply I imagine you still have to connect it to the USB ground?
 

Ah, sorry to hear that, Regal. The path of DIY is neither easy nor cheap, as you said before!
 
Yes you still need to have the 5V ground connected to the USB ground.
 

 

[punk_guy182]

Hello all!
 
I just spoke to Kingwa and according to him the BNC socket of the hiFace is not 75ohms but 50ohms. Would a 50ohms BNC attenuator have a better impact on sound quality after all?

 

[ccschua]

Just finish the mod to the hiface. I remove the inductor and connect the 3.3v supply to the right pad. Beside the inductor is a component. Is it ok to short the right pad of inductor with the left pad of the component next to the removed inductor.
 
 
 
 
 
 

 

[mmerrill99]

Yes, I've been wondering about this myself - it looks like it's not a 75ohm BNC connector (as it has white insulation around it's inner connector pin). I haven't really addressed this in my own head yet Matthieu. The correct approach is to really replace the whole output stage of the Hiface with true 75 ohm termination & then apply attenuators. I was intending to do something like this, bypassing (or removing) the SPIF transformer & output connectors for my own output stage configuration but I'm not at that point yet (so please don't ask me to do this for your device )
 
So your question is very prescient - what's best to do with the current set-up? If you have a BNC Hiface then it is presumed that it is to feed a DAC with BNC input. This is assumed to be a 75ohm input but they are often not! So we are in a quandary of mistakes here. How best to work our way through them is the question?  

 

[mmerrill99]

Quote:

Just finish the mod to the hiface. I remove the inductor and connect the 3.3v supply to the right pad. Beside the inductor is a component. Is it ok to short the right pad of inductor with the left pad of the component next to the removed inductor.
 

It would be better if you showed a HD pic of the parts you are talking about but if you mean the brown smd cap to the right of the inductor that you removed then yes, this is electrically connected to the inductor's right pad so you can short between them. But again you really need some pics to show if we are talking about the same thing? There is a HD shot on page 1 of this thread that shows the inductor & the smd capacitor to the right of it. From your pic it looks like you have already wired this up however - how does it sound?

 

[punk_guy182]

Quote:

Yes, I've been wondering about this myself - it looks like it's not a 75ohm BNC connector (as it has white insulation around it's inner connector pin). I haven't really addressed this in my own head yet Matthieu. The correct approach is to really replace the whole output stage of the Hiface with true 75 ohm termination & then apply attenuators. I was intending to do something like this, bypassing (or removing) the SPIF transformer & output connectors for my own output stage configuration but I'm not at that point yet (so please don't ask me to do this for your device )
 
So your question is very prescient - what's best to do with the current set-up? If you have a BNC Hiface then it is presumed that it is to feed a DAC with BNC input. This is assumed to be a 75ohm input but they are often not! So we are in a quandary of mistakes here. How best to work our way through them is the question?  

Please let me know if you can find a way to make it 75ohms. The BNC socket on my DAC 75ohms and I'd like the hiface to match it.
BTW, S/PDIF is a poorly implemented standard and I'd like to see another one replace it that is less vulnerable and better implemented on hardware.

 

[ccschua]

Hi,
 
It works. I saw that Regal also shorted the link for easier connection. I apply solder paste thru out for easier working.
 
Well sound wise it is slight improvement. again in hifi, noticeable improvement is something better than previous setup and it is better than without.
 
Quote:

It would be better if you showed a HD pic of the parts you are talking about but if you mean the brown smd cap to the right of the inductor that you removed then yes, this is electrically connected to the inductor's right pad so you can short between them. But again you really need some pics to show if we are talking about the same thing? There is a HD shot on page 1 of this thread that shows the inductor & the smd capacitor to the right of it.From your pic it looks like you have already wired this up however - how does it sound?

 

[mmerrill99]

Quote:

Hi,
 
It works. I saw that Regal also shorted the link for easier connection. I apply solder paste thru out for easier working.
 
Well sound wise it is slight improvement. again in hifi, noticeable improvement is something better than previous setup and it is better than without.
 

If it's only a slight improvement over stock, this wouldn't concur with Regal or my experience of this mod !
 

 

[digger945]

Quote:

If it's only a slight improvement over stock, this wouldn't concur with Regal or my experience of this mod !
 

Maybe you have much better listening gear than ccschua. Neither one of you have anything in your profiles.
 
I wanted to ask, at what point on the leading edge does the recieving end of your dac trigger high? Somewhere in the 500 to 800mV range?
 
Does the trigger point change if the spdif signal voltage is changed?
 

 

[ccschua]

my dac is audio-gd reference 1, Audiogd CIA-400, Dynaudio Focus 140. Cable is siltech paris and power by a richard company pro 400.
 
very soon I will hook up the hiface with blackcat velose.
 
I compare the hiface to audio-gd cd-7se and it is big difference.
 
Should I consider the 5V mod? how shall isolate the USB 5V supply