Point to point wired dac

Hi Guys,

Sharing a p.t.p hard wired dac using the receiver chip CS8412 which was kindly donated by VT4C. Giving credit to Yeo and VT4C, this is a modified clone dac of the famous Monica1 using TDA1545A dac chip in digital filterless non-over sampling mode.

Overall signal path was kept as short as possible by ensuring the layout of the dac relative to the tube stage is optimized.

Some highlights of the DAC modification include:
1) Point to point wiring using a large copper ground plane and both chips are wrapped with copper foil which are then grounded together.

2) Using very low i/v resistor (330 ohms) from original 2k2. This ensures a very low distortion and clear sound but the output voltage will be very low. A single 5687 tube will be the amplifier.

3) Direct coupling (no capacitor) between the dac's output stage into the tube stage. The tube biasing has been offset to counter the dc voltage that is being fed by the TDA1545 chip. With less 1 cap in the signal path, nuances are reproduced more freely.


Overall lessons learned along the way:
1) The DAC's signature is highly influenced by the i/v resistor. It sounds best and most romantic when using ordinary carbon composite resistor. Never ever use a trimpot hoping to tune that i/v value on the fly. The sound really sucks!

2) Removing that coupling cap between the DAC and tube stage is significant enough not to be ignored.

3) Initially the 5687 tube stage was fed with a simple resistor loaded 10Kohm. The sound still buzzed from insufficient PSU filtering. The buzz was gone when the anode resistor was replaced with a CCS.

4) The grid stopper was initially a 10kohm AllenBradley resistor. There's some kind of warm harshness that I didn't like about it. Replacing it with a simple Dale 1kohm resistor brought good balance between warmth and clean highs.

pictures now...

got the cs8412 chip


wrap it up with copper


TDA1545 chip also wrapped in copper (left)


CS8412 attached to the goundplane


Top side of the goundplane sits the voltage regulators, resistors, capacitors and diode strings.

Top view of the dac. The right blue squares are the trimpot i/v resistor which was later replaced with carbon resistors. To me the carbon sounded most romantic. These trimpots sounded harsh to my ears.


The final dac now attached to the wooden chassis together with its 12v regulator on the left.


Prelim view of the whole assembly.


5687 tube stage with ccs loading.


Dac wiring to the tube stage is short and sweet.


Final touchup.


She's singing now... without any panties

Lovely. I am amazed by the way you "fool around" with all the electrical components like Lego.. envy ur knowledge in all these.

Have u built flea power tube amp before? Thanks for sharing.

Wikin - job well done. dac + tubes = heaven.

Good job ! Not an easy job for digital to be point to point.
Cheers,
Cheah

adrian4454 wrote:Lovely. I am amazed by the way you "fool around" with all the electrical components like Lego.. envy ur knowledge in all these.

Have u built flea power tube amp before? Thanks for sharing.

The concept of audio and lego do have similarities - you're right; they are like building blocks.

Yeah I did a couple of tube amps, not too flea, more like on 5-15w range SE.

cheers

mthoi wrote:Wikin - job well done. dac + tubes = heaven.

Totally agree MT Hoi

cheers

noodle88 wrote:Good job ! Not an easy job for digital to be point to point.
Cheers,
Cheah

It's actually challenging to the eyes and how steady can I remain to hold the iron... age is slowly catching up... haih....

cheers

Wikin wrote:

noodle88 wrote:Good job ! Not an easy job for digital to be point to point.
Cheers,
Cheah

It's actually challenging to the eyes and how steady can I remain to hold the iron... age is slowly catching up... haih....

cheers

Hi!

Don't say that b4 40 years old....




Cheah

noodle88 wrote:

Wikin wrote:

noodle88 wrote:Good job ! Not an easy job for digital to be point to point.
Cheers,
Cheah

It's actually challenging to the eyes and how steady can I remain to hold the iron... age is slowly catching up... haih....

cheers

Hi!

Don't say that b4 40 years old....




Cheah

I kena a bit of accelerated ageing due to excessive building, just lately... just like too much sex is not good for you

cheers

The current sound is organic, warm and a bit dark typical of non-os sound.

Got a bit greedy today so I thought lets push this dac further. Wanted the extra/excessive air factor and instruments to delineate/float better in the soundstage.

Tried a few tweaks and eventually settled on these 2 significant ones that produced the desired sound:

1) Changed the copper wires from dac to tube, CCS to anode, and Anode to Output Caps using thick teflon silver plated copper wire (the pair of red, yellow, blue wires)



2) Bypass the 1kohm grid stoppers from dac output to grid input (the pair of yellow wires)




Float baby, float.... and the instruments do float convincingly. Tonally the silver plated wires brought sweetness and gone is the dark sound. This is much livelier.


cheers

The term CSS stand for: Constant Current Source? Is it correct?

Yes CCS is constant current source, or some call it constant current sink.

Cheers

great job,great taalent.
your steady soldering skill do make a great painting job.

your are my idol,i am now perfecting my soldering skills first.

wahlauyeh wrote:The  term CSS stand for: Constant Current Source? Is it correct?

wo cute dig, this term is too difficult for a layman to understand!
electronics is basically a painting that describe how voltage and current is being worked together in a given time domain.

am i right to the point?