Single rail, active I/V for TDA1543, TDA1545A

[rbroer]

Michael,

I built it a while ago on vero-board, it's quite easy.
IMHO it sounds better than the active I/V posted in the "simple I/V" threads, but not as smooth as the folded cascode. YMMV.
I used just the raw supply for the positive rail, no need for regulator because of the constant current for the LED/diodes references.

[mihu]

Thank you Rudolf, I´ll try that version. I guess for a TDA1545 I have to replace D5 with a 1N4148, anything else to change? What type of capacitor do you recommend for C1? 100µF is a pretty high value that makes a a "better quality" cap pretty expensive.
How about driving a passive preamp from this stage?

Michael

[rbroer]

Originally posted by Andypairo
how does it compare it with passive I/V?
If I understand correctly the supply is 15V, right?
If I should use a battery for powering it do I risk clipping?
BTW What's the color of the leds?

- read my earlier posts for MY opinions
- I think I used something like raw 18V after the rectifiers
- depends on voltage of battery and value of Riv
- green

Originally posted by mihu
I guess for a TDA1545 I have to replace D5 with a 1N4148, anything else to change?
What type of capacitor do you recommend for C1? 100µF is a pretty high value that makes a a "better quality" cap pretty expensive.
How about driving a passive preamp from this stage?

- don't think any change needed for TDA1545A, except Riv/Civ
- use whatever cap YOU like. I just used 100u for simulations, 2.2u Audyn KpSn in real life.
- well..., try, and let us know

The intend was to keep it simple, active stage with low parts count, just one rail in stead of two, using raw supply.
For really low parts count, one can even ommit casode transistor in the current sink (Q2, D2) and the common base (Q3, D3) as well.

[Terry Demol]

Originally posted by rbroer

- read my earlier posts for MY opinions
- I think I used something like raw 18V after the rectifiers
- depends on voltage of battery and value of Riv
- green


- don't think any change needed for TDA1545A, except Riv/Civ
- use whatever cap YOU like. I just used 100u for simulations, 2.2u Audyn KpSn in real life.
- well..., try, and let us know

The intend was to keep it simple, active stage with low parts count, just one rail in stead of two, using raw supply.
For really low parts count, one can even ommit casode transistor in the current sink (Q2, D2) and the common base (Q3, D3) as well.

Watch out for OP voltage compliance of DAC, In other words,
what is the optimum DC level for dac OP. Your dac feed in point
is sitting at about +2.7V ? Shouldn't this be 0V?

Cheers,

Terry

[Andypairo]

depends on voltage of battery and value of Riv

I use a 12V gel battery.. is this voltage too low?

Cheers

Andrea

[rbroer]

Originally posted by Terry Demol
Watch out for OP voltage compliance of DAC, In other words,
what is the optimum DC level for dac OP. Your dac feed in point
is sitting at about +2.7V ? Shouldn't this be 0V?

As mentioned earlier, this circuit is intended for TDA1543, (TDA1545A as well) with dac output voltage compliance of 1.8V~ Vsup-1.2V

[hifi]

The voltage drop over a led is well defined (because of the single wavelength of the light emitted) so different colour yields different voltage drop.

/micke

[Bricolo]

Originally posted by rbroer


As mentioned earlier, this circuit is intended for TDA1543, (TDA1545A as well) with dac output voltage compliance of 1.8V~ Vsup-1.2V

what should I change to use it with a TDA1541A?

[Andypairo]

Bricolo, at a first glance what you ask is not trivial.

The emitter of Q4 is at a fixed voltage (2Vled - 0,7V), and you should bring that node to a voltage suitable for the DC compliance of the 1541, which is much smaller as I recall.

However, if you bring the Idac node too low the current sink tied to Gnd can't work anymore, hence a negative supply is needed...

Cheers

Andrea

[Bricolo]

Originally posted by Andypairo
Bricolo, at a first glance what you ask is not trivial.

The emitter of Q4 is at a fixed voltage (2Vled - 0,7V), and you should bring that node to a voltage suitable for the DC compliance of the 1541, which is much smaller as I recall.

However, if you bring the Idac node too low the current sink tied to Gnd can't work anymore, hence a negative supply is needed...

Cheers

Andrea

2*2Vled, no?

BTW, what's the normal voltagr for red and green leds?
I measured the 5mm red ones I had: 1.63V, the 3mm green ones: 1.62V