AD1865 the best DAC

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#142
analog_sa said:
Same as Jonners i'd be interested in an 1865 board with an I2S converter as my interest in spdif is close to zero.
Click to expand...

Agree, the S/P-DIF does absolutely nothing good for music reproduction IME!

I made an experiment many years ago using a Teac VRDS P700-CD-drive and an external DAC (LC Audio ZAPdac).

Took out BCLK, WCLK and data directly from the drive and re-shaped the signal. Removed the oscillator from the P700 and used only the low-jitter clock in the DAC as master.

I was totally shocked about the improvement! Since then I've only used integrated CD-players (SONY SCD for SACD-playback) but now only interested in the sound of my non oversampling usb dac.

You get tons of bit errors out of old CDs...

So the true DACEND will have to include a USB-interface IMHO. ;-)

Nice project & a nice thread anyway.... ;-)
 
#143
AD1865 is great dac, easy to make , high quality sound

i have sample dac project with ad1865

DSCN3136.jpg



first protype, i use simple regulator for dac, and srpp for iv
DSCF2679.jpg


then i'm replace srpp iv by paraller triode iv
Hnhnh015.jpg


second ver i use shunt regulator for dac board
DSCN2374.jpg




b.r
 
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#144
tivoidethuong said:
AD1865 is great dac, easy to make , high quality sound

i have sample dac project with ad1865

first protype, i use simple regulator for dac, and srpp for iv

then i'm replace srpp iv by paraller triode iv


second ver i use shunt regulator for dac board

b.r
Click to expand...

Great samples, guy. It seems that shunt regulator is the rule of success in efficient power supply for DAC. And parallel triode at I/V stage is a saver for extended bandwidth output.

Suggest you to try the shunt power supply board by Quanghao, the more completed and tested one, with your DAC part to see how things are changing.

On the AC side, can we have a photo of your transformer? Thanks for sharing.
 
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#154
Now im layout new PCb for DAC-end use trasformer for output, all in one PCB, and i change tl431 by many Salas shunt low!

with capital under $ 1000, DAC-end can be compared with any DAC that cost $ 5000. is my thought! and when you've completed it you find difficult to replace the DAC that the present time and the next few years.

Im sure I will take a long time for the best layout
 
#155
quanghao said:
Now im layout new PCb for DAC-end use trasformer for output, all in one PCB, and i change tl431 by many Salas shunt low!

with capital under $ 1000, DAC-end can be compared with any DAC that cost $ 5000. is my thought! and when you've completed it you find difficult to replace the DAC that the present time and the next few years.

Im sure I will take a long time for the best layout
Click to expand...

Do you have a schema of it?
 
#156
regal said:
Why do people keep using SRPP tube outputs on DAC's?

Because people like it. It's simple, easy to build and almost no need to worry to much about the bias when changing tubes. Most important, it gives you a reasonable good sound compared to other circuits in similar investment.

They are push-pull and get very unbalanced with the load (input impedance of the amp.)

What is the meaning of "Very unbalanced with the load"? Why does it is unbalance with the load? Do you mean load mismatched or something else?

I've comapred several tube outputs for DAC's and nothing sounds better with the right tube in a simple grounded cathode. Its SET and with the right tube can power any amp with a reasonable input impedance (40kohm or higher.)


The other issue with the AD1865 is the low output current you are going to use a high resistance I/V resistor which is not good. Best to parallel 4 AD865's to get a higher current and less load on the DAC Chip.

Why a high resistance I/V resistor is not good? V=IR is the Law of Physics. To get the desired level of signal, you can either increase the value of current source or the value of I/V resistor, provided that it's not too big to be affected by the input resistance of the next stage. The input resistance of the tube output stage is greater than hundreds Kohm whic is not a factor.
Click to expand...
 
#157

As far as the load dependance of SRPP read Broski'es article on SRPP. I did a lot of experiementing with SRPP in DAC's and found that a simple 6n6pi or 5842 with output taken from the anode sounds a lot better, just personal experience and Broskie does a good job explaining the why.

As far as bigger I/V resistor there is proof that most R2R DAC sound best with the lowest I/V resistor possible, some claim the AD1865 is somewhat immune but the datasheets are not specific. Basically you want the DAC chip to see the lowest impedance possible, this is why people spend hundreds of hours designing low ohm analog stages for DAC's like Jocko's I/V, etc.
 
#158
regal said:
As far as the load dependance of SRPP read Broski'es article on SRPP. I did a lot of experiementing with SRPP in DAC's and found that a simple 6n6pi or 5842 with output taken from the anode sounds a lot better, just personal experience and Broskie does a good job explaining the why.

As far as bigger I/V resistor there is proof that most R2R DAC sound best with the lowest I/V resistor possible, some claim the AD1865 is somewhat immune but the datasheets are not specific. Basically you want the DAC chip to see the lowest impedance possible, this is why people spend hundreds of hours designing low ohm analog stages for DAC's like Jocko's I/V, etc.
Click to expand...

can you sent the circuit???
thank
 
#159
I used a PCM63 so I used this simple stage with a 47 ohm I/V resistor:

compund-2.jpg


But I am now working with an AD1862 which has similiar +_1mA output as the AD1865,

so I am going for a lower I/V resistor (10 ohms) and a gain stage of 100, output impedance is 800 ohms:

6EW7amp.jpg


Except no output transformer (just CCS like the first stage & OTL 1 uf cap) and the led on the first stage is upside down (I need to correct that), may experiement with cap coupling stages and grid bias on the second stage per Sy's recommendation. I'll report how it works out. I will modify the schematic for DAC output if there is interest. But this gives you the general plan.
 
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