The Pass D1 For Tda1543

[anbello]

Hi stefanobilliani,
i would like to know if it's possible to use 2 o 4 tda1543 in parallel sharing the same i/v d1 stage (i mean the 4 i out of the dacs entering in 1 d1 stage).
Another question: the out of the d1 can directly drive the next stage (a pre or chipamp in my case) or needs some sort of buffering?

Thanks
Andrea

 

[Luke]

anyone?

 

[stefanobilliani]

Hi stefanobilliani,
i would like to know if it's possible to use 2 o 4 tda1543 in parallel sharing the same i/v d1 stage (i mean the 4 i out of the dacs entering in 1 d1 stage).
Another question: the out of the d1 can directly drive the next stage (a pre or chipamp in my case) or needs some sort of buffering?

Thanks
Andrea

Yes you can use that approach , you will need to change some values of resistance to make it work properly . Not sure if you will get improvements , the best thing is to try .
I remember I tryed 2 of them and they did work ok .

Regarding the output driving that there is not a problem at all unless you need more gain .
The output impedance is already low enough , of course I omitted in this thread the use of buffers for semplicity and also becouse , probably , the amps I play with are often buffered at theyr input ( see Zen V4 that includes the buffer at its input and inside the feedback loop ).

 

[Luke]

Hi Stefan,

any idea why mine doesnt play music?

 

[stefanobilliani]

How many 1543 are you using?

 

[Luke]

I am using 2, from the 74hc86 to the dacs is exactly as your schematic.

 

[stefanobilliani]

Ah ok , so you are doing balanced mode . I see you use the I/V resistor , you need 4 of them . Do this test: leve out the Xor ports and check if each Tda works in Single Ended mode . Control also the voltages at the PIN 6,7, 8 . and remember that with the Cascode I/V stage there is no need to control the pin 7( as shown in schematic posted) , while if you use I/V resistors that pin CANNOT be left alone , but there is the need to create a current through it with a resistor , typically 1k ohm or so to ground .

 

[stefanobilliani]

I also experimented to connect pin 7 ( and his resistance ) to a negative voltage , and had very nice results IMHO in terms of dynamics . I mean something like -30 volts .

 

[Luke]

Thanks Stefan,

Pin 7 (vref) is 1.5K, pins 6 and 8 is 2.7K.
I will try and bypass the Xor and try single ended tomorrow, its bed time. Thanks

 

[ChuckT]

Hi Stef,

I am tempted to try the D1 but I have only +/-15V on hand, do I need to half the value for R1 and R2?
And what is the resistance from pin 7 to ground.
Thanks.

 

[Gregje]

Anyone still building these?
I have build one recently and put it into an old Philips CD600.
My PS is built using lm317 and lm337 with 1000uF before and 470uF after the regulators
(this looks like the values used in the original NP D1). Still I have massive hum which is not entirely gone when I use 4700uF before and 3300uF after the regulators. The output voltage is +/-25V (some 4V lost in the regulators)

Can anybody advise?

I also hear some relatively high freq (whitish) noise. Finally I can hear when I move the slider in the head phone amps (ChiMoy and Pellerano's Zen) when connected to this IV converter. The pots are not great quality but still no problem with other sources.

Any hints will be very welcome.

Greg

 

[Gregje]

Ok, the hum is gone. I messed up the PSU. Pretty badly.. This has been sorted out.

The high pitched noise: my original approach was to measure Vref of my particular 1543 chip (which was 2.15V), set this voltage at the source of IRF610 connect and play. This gave me some hiss. So I lowered the sourve voltage to 2.05V and reconnected. This seems to help. Does it make any sense?? BTW they is still some noise (like a tape noise from a cassette player), this might be caused by low gain (I have to crank up the amp quite a lot) Has anybody experienced the noise?

Otherwise it is working. Needs some gain adjustments as I mentioned above. I believe the circut presented at the beginning of this thread is for two 1543 so it has higher gain.
I will play with the drain resistor ( now 820, increase to some 1.2-1.5k), but I am worried that I will need an extra buffer there.

Greg

 

[Gregje]

Hi,

I tried a few more thing. I played with the current through the FET (source resistor) I also tried to increase the drain resistor for the gain. I ended up with 1.5K drain resistor (with 3.3K source). The gain was still not enough. The other worrying thing was the noise which I mentioned before (cassette tape like) which I was not able to eliminate.

The final experiment was to take the IV converted out of Philips cd600 and put it to an old cd190 equipped with tda1541. I have set the Vref to 0 and rock'n'roll. The gain is ok if not too much. Also the noise was gone. Had a nice evening going through CDs yesterday. Do you think it deserves a buffer more like real D1?

I still worries me that I do not understand the noise issue.

Greg