TDA 1543 I/V stage education needed!!

[Mad_K]

Many thanks Elso

I'm curious about your bufferstage; do you want to share some details?

Also, a quick question: How does it sound comparing to passive I/V?

 

[Elso Kwak]

IV and Bufferstage

Many thanks Elso

I'm curious about your bufferstage; do you want to share some details?

Also, a quick question: How does it sound comparing to passive I/V?

Hi Mad_K
Funny thing is that I got the passive IV stage never working quite right. I did not get rid of the hum. I also noticed a lack of dynamics with passive conversion, also with the AD1865.
In the schematic below R3= 3k65, c2 = 3n3 and ???= ground. The non-inverting input of the first opamp is not connected to ground but to Vref of the TDA1543. First opamp= OPA604 and second opamp is the discrete buffer. Much to my surprise the OPA604 sounded better than the discrete buffer for IV. I tried almost all conceivable opamps in this position! All caps are 1% polypropylene Philips or BC Components and the resistors are Dale metalfim, yes the well-known brown coloured ones! I am extremely grateful to Audiofanatic letting me to try these resistors! The filter was calculated in a few seconds with Filterpro from Burr-Brown. The third order filter is of the multiple feedback variety and the first pole is in the IV converter. This way I could realise a third order filter with two opamps and an IV converter.
For the buffer stage that is after the IV stage see this thread:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=1794&highlight=

 

[Mad_K]

Interesting Elso, but is the value of the Vref to GND (3K3) resistor on the 1543 independent of the R3 (in your schematic) value?

I was planning to do as per 1543 datasheet, but with 3K3 to GND from Vref; is this correct? (+5VDD)

 

[Elso Kwak]

Resistor on Vref

Interesting Elso, but is the value of the Vref to GND (3K3) resistor on the 1543 independent of the R3 (in your schematic) value?

I was planning to do as per 1543 datasheet, but with 3K3 to GND from Vref; is this correct? (+5VDD)

Hi Mad_K, Yes, the DAC is operating in a virtual ground.

 

[Mad_K]

Well, I tried it and I must say that I LIKE IT ALOT

I used the opa2604 and 1K2/3n3 and 3K3 from Vref. I have about 2,1V on the output.

I will definately make a proper version and experiment with different (single) opamps etc..

All the things I felt the passive IV lacked are now in place; dynamics, bass slam and a generally more interesting/musical presentation

Thank you for the 3K3 value Elso

BTW -if I want more gain; could I just recalculate the R+C value in the feedbakloop, or are there other matthers to consider?
With the 1K2 I figure I get about 1V RMS out.

 

[Elso Kwak]

R and C in IV feedback

Well, I tried it and I must say that I LIKE IT ALOT

I used the opa2604 and 1K2/3n3 and 3K3 from Vref. I have about 2,1V on the output.

I will definately make a proper version and experiment with different (single) opamps etc..

All the things I felt the passive IV lacked are now in place; dynamics, bass slam and a generally more interesting/musical presentation

Thank you for the 3K3 value Elso

BTW -if I want more gain; could I just recalculate the R+C value in the feedbakloop, or are there other matthers to consider?
With the 1K2 I figure I get about 1V RMS out.

Curreently I am using 3k65 and a 3n3 cap as the R & C value.

 

[jean-paul]

Doing things as the datasheet says is in fashion these days

At least it saves n threads about non inverting versus inverting....

Only that -3 dB point at 10 kHz always hurts my eyes Elso.

 

[Elso Kwak]

Doing things as the datasheet says is in fashion these days

At least it saves n threads about non inverting versus inverting....

Only that -3 dB point at 10 kHz always hurts my eyes Elso.

Jean-Paul,
This hurts my eyes, and ears (1kHz, 0dB):

 

[jean-paul]

Despite the ugly looks I have heard DAC's with waveforms like that without remarking much negative ( sonically of course ). I did remark that my efforts of making it better resulted in a less good sounding but better measuring DAC ....

Maybe human ears have a built in integrator ?

 

[Elso Kwak]

Despite the ugly looks I have heard DAC's with waveforms like that without remarking much negative ( sonically of course ). I did remark that my efforts of making it better resulted in a less good sounding but better measuring DAC ....

Maybe human ears have a built in integrator ?

Now what are you going to do about it?
What efforts?

 

[tonitze]

Elso,

can you please explain again how to connect the 3k3 resistor. Is it like this; ground=3k3=vref=non-inverting input

or vref=3k3=non-inverting input and non connecting to gnd?

getting real confused

Thanks.

toni

 

[Mad_K]

ground=3k3=vref=non-inverting input

 

[Elso Kwak]

Datasheet

Elso,

can you please explain again how to connect the 3k3 resistor. Is it like this; ground=3k3=vref=non-inverting input

or vref=3k3=non-inverting input and non connecting to gnd?

getting real confused

Thanks.

toni

Hi Toni,
Yes it is in the datasheet of the TDA1543! They call it a optional resitor and the only omission is they give no value...

 

[tonitze]

Thanks Mads K and Elso. Gonna try it!!

 

[tonitze]

Today I tried removing the 3.3n cap parallel with the feedback resistor on my tda1543 active i/v using op-amp and it sound good. What are these cap for. Is it for filtering or something?
I happen to come across tips by KYW on tda1545a active i/v using op-amp as per datasheet and I applied it on my nos tda1543 and it sound good. Am I doing the right thing here?

Toni.