Parallel TDA1541A ... some clarifications required

[skje]

Hello Folks,

Thanks to Torben, i made a TDA1541A based DAC module and integrated it with the CDPRO2M module (using I2S)....and an 6DJ8 based output stage. I'm using Torben's PCB itself for the main DAC board.

http://bygselvhifi.dk/dualdactubefacelift.htm

I have some questions....and any response will be appreciated.

1) The four 180ohms resistor that connects pins 26,27 & 28 with the -18 and +18 pwr supply, runs very hot. It does not blow...but runs very hot . I'm using a 3W resistor. Is this okay .... should it not be a problem.

2) Since the B+ for the tube output stage, connects the signal ground to "chassis ground", the DAC also gets hooked to "Chassis ground".Is it okay to do so ??.

I do get some noise when the tube-stage is connected to the o/p of the DAC module.

3) I'm using the same filter used by Torben in his o/p stage....what is really the price one should expect to pay for this...in time domain.

Regards
SK

[Archwn]

i think they are used to drop the voltage down to +5V. the calculation shows about 1W at this resistor so 3W should be fine. but should it be that hot? the current is around 70mA please check with the datasheet again.

not quite understand item #2 and #3 though

[skje]

Thanks for the response.

Regd. (2) & (3) ...I found the details about grounding....from a doc by guido.

[skje]

I do have another problem....with the measurement on PIN 25.

All measurements on the TDA1541A measures the same as published on the Lesha DAC page. The only exception being that PIN 25 (Left out) measures about 125mv, while PIN 6 (Right out) measures 53mv.



As per Lesha's the measurement on PIN25 is supposed to be the same as PIN 6 (ie., 53mV). I tried various things ...

1) Used only one TDA1541A, the measurement changed to 27mV on PIN 6 and 78mV on PIN 25 (the same problem)

2) I tried another set of TDA1541A. This time the measurement became even worse (54mV on PIN 6 and 178mV on PIN 25)

3) I assembed a new PCB with different set of components...the same results !!

In all attempts - PIN 25 is the only wrong measurement i get !!



wondering what could be the problem ....

(a) Something is wrong with the way i have populated the PCB (or)

(b) is something wrong with my series regulator based on 317 & 337 (or)

(c) are both sets of my TDA1541A faulty !!



Has anyone faced such issue....