NOS TDA1541 + D1 I/V & output stage

andynor

Member
2020-07-21 7:46 pm
Norway
Have you tried building anything smd? If you have a magnifier and a fine soldering bit it's really not a problem. Just practice and find what works for you. I do the blob one pad - hold the part with tweezers - melt the blob - slide into place - solder the other pad method. I built a D3 no issues. Have a go!
There may be many reasons as to why peppe sez he doesn’t have the means. I suggest we help him if he wants it real bad. You can ship that drek to me, or even better, to OPLDF. I hear he is two weeks on without constructing a new amp. Idle hands is never good :rofl:
 
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Don't want to derail the thread but I meant what I said in an encouraging way. I think a lot of people are scared of smd because they think of terrifying robot pick and place machines, incomprehensible paste masks and ovens from Hades. They don't even consider it because it's scary... but the same rules apply, pad, component, solder. By hand is quite doable for an awful lot of smd packages. Try a practice kit, back to the topic and I'll shut up now 😊
 
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nicoch58

Member
2004-10-06 12:20 pm
Yep Simnon build a lot of tripath smd amp with just ....plus a lot of patient ;)

1663675206060.png
 
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nicoch58

Member
2004-10-06 12:20 pm
As you said, the TDA1541A actually wants see a low impedance load for best performance.

The data sheet (page 7) says, "To ensure no performance losses, permitted output voltage compliance is ±25 mV maximum."

The current output of the chip is +/-2mA, with an offset of -2mA.

So for +/-25mV, maximum, the chip wants to see about 12 Ohm maximum. I'm sure that is why peppennino is interested in the D1's input impedance. :)

But then I load my dac with about 70R IV resistor and enjoy its sound. diyAudio member ecdesigns (John Brown), who has done a lot of work with the TDA1541A, has suggested that up to 150R may be used for IV.

ecdesigns IV resistor

But the D1 circuit is cool. The input mosfet is a current buffer. :)

I may try it but use a lower value for R4 since I don't need 3Vp output.
By Thorsten L. :
The Philips Datasheet is conservative. At AMR we did run extensive tests on that. The TDA1541 can handle more but not a LOT more. 50 Ohm I/V resistance is fine.
Secondly, if you want to stay within the 25mV compliance reliably for all possible output currents of the TDA1541 range you need 5.4 Ohm I/V conversion resistor (0.025V / 0.0046mA = 5.435Ohm).
My original "Adagio" DAC with TDA1541 used approximatly this value of resistance and a 1:15 Step Up Transformer. It also used an SRPP output stage tuned for lowest distortion, due to concerns about some of the ultrasonic "images" produced by the absence of oversampling folding back into the audio range.
 

Ben Mah

Member
Paid Member
2012-05-18 6:36 pm
Vancouver
Yes, I am aware of Thorsten Loesch's recommendations. Note that I currently use an I/V resistor of 70 Ohm.

My first TDA1541A dac that I built many years ago was based on Thorsten's first published TDA1541A dac, the Adagio, with SPDIF input and CS8412. I think I used an I/V resistor of about 20 or 25 Ohm and fed the output to a single ended 5842 output stage.

Years later I built another dac based on Thorsten's recommendations on this diyAudio thread: TDA1541A Veroboard dac

Later I deleted the on-board reclocker and divider and added IanCanada's isolator, FIFO, and clock. The first picture shows this setup with the Veroboard dac at the lower right of the picture.

RyanJ's D3 board is now used in place of the Veroboard dac, and I take I2S directly out from a single board computer to the FIFO and clock. I still use the power supplies on the Veroboard to power the I2S to simultaneous converter and to power some of the IanCanada boards. I/V is my own hand wound 70 Ohm resistors with my preamp providing voltage gain.

I think it sounds really good.:)
 

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nicoch58

Member
2004-10-06 12:20 pm
Yes, I am aware of Thorsten Loesch's recommendations. Note that I currently use an I/V resistor of 70 Ohm.

My first TDA1541A dac that I built many years ago was based on Thorsten's first published TDA1541A dac, the Adagio, with SPDIF input and CS8412. I think I used an I/V resistor of about 20 or 25 Ohm and fed the output to a single ended 5842 output stage.

Years later I built another dac based on Thorsten's recommendations on this diyAudio thread: TDA1541A Veroboard dac

Later I deleted the on-board reclocker and divider and added IanCanada's isolator, FIFO, and clock. The first picture shows this setup with the Veroboard dac at the lower right of the picture.

RyanJ's D3 board is now used in place of the Veroboard dac, and I take I2S directly out from a single board computer to the FIFO and clock. I still use the power supplies on the Veroboard to power the I2S to simultaneous converter and to power some of the IanCanada boards. I/V is my own hand wound 70 Ohm resistors with my preamp providing voltage gain.

I think it sounds really good.:)
nice me too long time on tda nos ,1543 on 2007 and AYAII from 2013
 
Circa 30V

so current in each first section is neg 30V/string of source resistors

that would be 30V/3K3=9.1mA

buffer Iq is - voltage at gate (30V-(9.1mA*R4 deduct 4V)), divide with 1K5 = 8.2mA

gives sum of, say, 18mA per side

36mA entire shebang

xformer at least 56V center-tapped - try to find adequate close standard one

56Vac * 36mA gives 2VA

so 10VA Donut logical choice ........ of course you can use more