Experience with this DIY DAC ?

[McGyver]

thanks

 

[data]

Gee!
looks even more untidy in the pic

They also look a bit smaller in that pic

 

[data]

Success!

Too embarrassed to say where I went wrong, was my bad

Loving these Cinemag transformers

 

[data]

Hay guys
I'm using caps that are marked "102k100" that's .001uf isn't it?

I have 510 ohm resisters on each leg of the primaries with one of these across following.

on the secondaries I have a combination of a 1k resistor and one of these caps for HF filter.

Is this right

I'm looking for a LF cut off at 20hz?

 

[data]

Ignore the above post!
Doesn't matter, these sound fantastic as they are now.

Removed the cap across the primaries too.

(hate not being able to edit instead of messing up a thread with post after post)

 

[gabanyayaya]

is there anybody here have try to mod the psu parts.....like discrete regulator.....shunt or any similar of this dac.....???

 

[McCrackers]

Help with pulse transformer

I'm not sure what, if any, improvement I'll get by doing this but I need some help in installing this pulse transformer. There appears to be a space conveniently provided for this on the board(trafo pinout fits perfectly) but somehow this doesn't seem right. Are these four holes in the signal path or does something else need to be done?
The manufacturer has provided a schematic showing a 0.1uF cap on leg 2 but I'm a bit afraid to proceed without understanding what I'm doing.
Thanks

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[Bill Fuss]

Hey McCrackers,
The cap keeps any dc from getting to the trafo.

There has to be a solder blob or link connecting the primary and secondary PCB traces or the input would not work without a trafo installed. You'll have to find it and remove it to get the trafo in the circuit.

I think we all would like to know if you can hear a difference.

 

[McCrackers]

Hey McCrackers,
There has to be a solder blob or link connecting the primary and secondary PCB traces or the input would not work without a trafo installed. You'll have to find it and remove it to get the trafo in the circuit.

Bill,
This "blob" you speak of - would that be the one on top(pic 1) or the one directly under the coax input towards the front of the board(pic 2)?

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[Bill Fuss]

Actually, there is probably two blobs, one to ground the rca jack to the board and another from the center pin to a DC blocking cap that would lead to the chip input.

 

[gabanyayaya]

I'm not sure what, if any, improvement I'll get by doing this but I need some help in installing this pulse transformer. There appears to be a space conveniently provided for this on the board(trafo pinout fits perfectly) but somehow this doesn't seem right. Are these four holes in the signal path or does something else need to be done?
The manufacturer has provided a schematic showing a 0.1uF cap on leg 2 but I'm a bit afraid to proceed without understanding what I'm doing.
Thanks

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

You need to remove the original onboard digital input first. then remove/disconnect the first blob behind the digital input to the red film cap.

then install pulse transformer next from the digital input.......

this is how i install newava s22083 to my board

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[McCrackers]

You need to remove the original onboard digital input first. then remove/disconnect the first blob behind the digital input to the red film cap.

then install pulse transformer next from the digital input.......

this is how i install newava s22083 to my board

So basically, if I understand correctly, the space with the four pads(holes) is not used at all - am I correct?
The on board digital input is removed and replaced by a coax connector and the pulse transformer is soldered in-line from its input to the board. In the pic I can't quite make out what the yellow wire is doing and I still don't understand why "the blob" needs to be removed.
I didn't get much sleep last night so maybe this will all become clearer tomorrow.

 

[Bill Fuss]

Right now the RCA ground is connected to the board ground and the center pin feeds the chip input. If you want to achieve galvanic isolation, which is the only reason to use a pulse trafo, then both of those connections must be broken.
You should be able to keep the on board jack.

 

[McCrackers]

Thanks guys,
I should be good to go but if anybody else has some good clear pics or additional info please post.

 

[ch33ta]

Hello guys,
I have this DAC with a pair of UTC A-20 transformers, and I got a crazy idea and connected my HD595 headphones directly to DAC output. The sound is absolutely fantastic.
So my question is, has anyone else tried this, and are there any side effects from this setup - wouldn't want to mess up my DAC or headphones...

Thanks

 

[idlehands]

DAC-Headphones - this would be bad at both ends, for the 'phones it would let in DC, and for the DAC there would be an insufficient load( 50ohms) and that may kill the DAC chip.

At the very least you need some extra resistance and to measure the DC.

 

[ch33ta]

DAC-Headphones - this would be bad at both ends, for the 'phones it would let in DC, and for the DAC there would be an insufficient load( 50ohms) and that may kill the DAC chip.

At the very least you need some extra resistance and to measure the DC.

Sorry, my bad, didn't mention the UTC transformers...
It's DAC -> UTC A-20 -> Headphones
So there shouldn't be any DC on the headphones, the only thing left is the load on the transformers, can they drive 50ohm headphones connected directly on the secondary ???

 

[gabanyayaya]

So basically, if I understand correctly, the space with the four pads(holes) is not used at all - am I correct?
The on board digital input is removed and replaced by a coax connector and the pulse transformer is soldered in-line from its input to the board. In the pic I can't quite make out what the yellow wire is doing and I still don't understand why "the blob" needs to be removed.
I didn't get much sleep last night so maybe this will all become clearer tomorrow.

McCrackers


initially the original rca in the digital input is 'attached' to the input cap via the first solder blub at the back AND the empty pulse transformer input next to it is connected via solder track. this is because the DAC is not come with a pulse transformer even though it can be use with one suitable....

you need to remove the original digital rca first....then disconnect the solder blob because you need to reroute the digital input to the pulse transformer THEN output it to the input (input cap) so that the digital signal is 'treated' .............

You can skip the reroute thing if you wish not to use a pulse transformer (and leave the solder blob alone).

one thing to remember if using the pulse transformer is to mind the input output and ground orientation...

 

[Bill Fuss]

Sorry, my bad, didn't mention the UTC transformers...
It's DAC -> UTC A-20 -> Headphones
So there shouldn't be any DC on the headphones, the only thing left is the load on the transformers, can they drive 50ohm headphones connected directly on the secondary ???

Apparently they can. It's not an ideal load but you wont hurt anything.

 

[GerardA]

@ gabanyayaya

Like you say the blob has to be removed to cut the connection from inputsignal to the cap and it will then automatically be connected from input signal to trafo to cap???

Then the inputmass has to be cut from the dac-mass too. Is this done by removing the connector? Like the underside of the printed board and the top are connected by the foot of the inputconnector??

This would explain the problems some people have when they replace the inputconnector with an external one....

Any tips on a good trafo?