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Dark LED passive filter-I/V stage for NOS DACs

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#122
Hi Abraxilito,
I have built Miro's ad1862 with Ian's fifopi.
Unfortunately sounds didn't came out.
I found the PSU+/- opposite, Yellow led still lit but not sure if it's still ok.
Are there any points to check?
I have no skill to fix it so I am wondering
if I could buy another board without filter coils(it looks safe to me).
Sorry for bothering for noob.
 
#123
tamra - both yellow LEDs are on? Test points are marked on the back of the PCB, a good idea to measure TP6 and TP7 to see if everything's fine. They should be around 7V above GND.

Certainly you can buy a built board minus the filter, that would be roughly half the price of a finished Dark LED module.
 
#132
This thread is about an I/V yes. I am not sure if discrete R2Rs are really suitable for an external I/V converter though. There are two configurations for R2R type DACs - voltage mode and current mode. Voltage mode R2R DACs I would guess are the most common type, these have no need for I/V as they already output a voltage. Current mode R2R DACs do exist but their need for extreme precision in the I/V circuit (the input offset voltage) is problematic. My I/V has a lowish input offset voltage (typically below 5mV) but not nearly low enough for getting the best out of a current mode R2R DAC.

<afterthought>
I would guess there's a possibility to convert a voltage mode R2R DAC into current mode just by adding a series R. That'll do V/I conversion. Its not something I've tried but who knows?
 
#133
PCB arrived this morning.
I had time to listen for while.
Bass is great and sound is so smooth.
Thank you so much.
 

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#135
First listening test with pcb mounted provisionally on a board:
I still have tears in my eyes!!!!! It is so amazing !!!!!!! This is the sound I have been looking for the last decades.
See the picture: left DDPRO Receiver stage from Eric Juaneda. A NOS Receiver. Then the symmetrical DAC with 4x PCM1704. Then Dark LED Filter. On the top the external Masterclock which is still not running well. So tested with the internal clock of the CS-chip. I have to find an alternative for the 5,6 MHz clock. And I will add another power source for the second dark LED. After that follow my two Nelson Pass X150 clones and the speakers are Myro Weidlich 1.3 with Oscar Heil AMT. Ah well the source of the DAC ist CD and Streamer and Trinnov ST that allows to adjust the volume digitally.

Back to the sound: I have listened to many many DAC in my life. But non of them was comparable to this one. This is pure magic.

Look at the 16 KHz sinewave. Everyone using a NOS DAC knows what the Signal is like. Minecraft, just one Lego stone and this is even varying depending on the point of reading. Digital filters like the DF1704 try their best to reconstruct the original shape. I tried all kinds of filters, upsampling etc. But still the sound was not comparable to analog sources. This is the first DAC-concept that sounds like my good old vinyl records.
 

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#136
:up: zille
Right, Dark LED sounds analog indeed (all of Richard's DACs do but this one excells IMO)

May I ask what is the output of your DAC board?
Is it the Iout from the PCM1704 direct, or LP filtered and buffered?
George
 
#138
zille said:
First listening test with pcb mounted provisionally on a board:
I still have tears in my eyes!!!!! It is so amazing !!!!!!! This is the sound I have been looking for the last decades.
See the picture: left DDPRO Receiver stage from Eric Juaneda. A NOS Receiver. Then the symmetrical DAC with 4x PCM1704. Then Dark LED Filter. On the top the external Masterclock which is still not running well. So tested with the internal clock of the CS-chip. I have to find an alternative for the 5,6 MHz clock. And I will add another power source for the second dark LED. After that follow my two Nelson Pass X150 clones and the speakers are Myro Weidlich 1.3 with Oscar Heil AMT. Ah well the source of the DAC ist CD and Streamer and Trinnov ST that allows to adjust the volume digitally.

Back to the sound: I have listened to many many DAC in my life. But non of them was comparable to this one. This is pure magic.

Look at the 16 KHz sinewave. Everyone using a NOS DAC knows what the Signal is like. Minecraft, just one Lego stone and this is even varying depending on the point of reading. Digital filters like the DF1704 try their best to reconstruct the original shape. I tried all kinds of filters, upsampling etc. But still the sound was not comparable to analog sources. This is the first DAC-concept that sounds like my good old vinyl records.
Click to expand...
How nice work!!! Congrats!!

I recently listened to this too, Abraxalitos creations have a special sound... 🙂
 
#139
zille said:
Hi, I use the I out signal from PCM1704. See attached schematic. Nothing special, just the cirquit of the datasheet.
Click to expand...
Thank you zille.
@alexopth1512 has given me two boards of Audio-gd DA-7 boards.
The plan is one of them to be tested with my Dark Led. (the other with a I/V of alexopth1512 design).
I 'll post back when I have news
Happy listening.🙂
George
 

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