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Old 21st September 2013, 02:18 PM   #61
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Default MOSSEN

Green output: MOSS

This is the output I have in mind (1543 Vdd 7V) and the comparison to the standard SEN (with 1543 Vdd 5-6V).

This MOSS I have used before with a triode as cascode. Extremely linear and no overshoot at all. With a triode the Vb becomes some 120-150V.
I used it on TDA1541 and when I 'shorted' the output with an extra 50 ohms there was no effect on the output RMS, so the input impedance is very low.
SEN+MOS-SEN.pdf
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Old 22nd September 2013, 02:54 AM   #62
wa2ise is offline wa2ise  United States
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Quote:
Originally Posted by Flied Egg View Post

Pin 7 is left floating and +3v from a couple of 1.5v batteries is fed to the other two resistors (Pins 6 & 8).
I think I did roughly the same thing when I created a voltage divider from +5V to ground, loading pins 6 and separately pin 8 (left and right channels). The Thevenian equivalent circuit looking like 2 to 3V (depends on the resistors selected) and around 1.3K or so, as an I/V conversion circuit.
Click the image to open in full size.
Click the image to open in full size.
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Old 4th October 2013, 11:51 AM   #63
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Default FFSS

Remember the logo ffss on some of the first vinyl discs?
Full Frequency Stereo Sound.

Well, that is the effect I have now with my latest version of the TDA1543 in a single solution.
Thanks to fliedegg I started to float pin 7, this implies there is no 'extra' current dumped by pins 6,8 and thus the output must float at around the same voltage; ECdesigns uses 3 - 3,2 Volt from lead batteries.

Quote:
Originally Posted by Flied Egg View Post
ECDesigns bias tweak can be found here.

Building the ultimate NOS DAC using TDA1541A

Pin 7 is left floating and +3v from a couple of 1.5v batteries is fed to the other two resistors (Pins 6 & 8).
Leaving the pin floating is indeed a large improvement, the coarseness that is often heard in the TDA1543 is completely gone.

Next improvement I found is that it is best for the high frequencies to buffer the output from the pins 6, 8 before going to the filter.
  • With the filter directly connected to the pins I have noticed the high frequencies are reduced a bit. The sound is very "TDA1541-like", which is not bad by the way.
  • With a buffer in place the high frequencies are all there

I have used a TLC272 opamp, a curious device as it was made for single supply use. I use the same 7 volt as the Vb for the opamp.

This is the marvelous result of the combined filters effect:

audio 48 L1020621.jpg

As you see the whole staircase (stepwise response) is filtered out in a superb way. 4fOS, the main filter has the dip at 175 kHz. I use the opamp in a 2x amplification.

I have played around with the bias voltage; I started at 3,8 V and it can be increased to 4,1 v (which is best to center the output between the voltage rails). The Pin 6, 8 output floats along with this bias (the current source has a 380 kOhm virtual impedance) from 2,9 - 3,2 V DC.

The sound: FFSS of course, and a very tight bass (better than with my TDA1541 S2/SEN) while the highs are sibilant and the crescendo and forte passages have no problem at all. The output cap is critical in this aspect I noticed. It is a pleasure to listen to.
Not as warm (tubey) yet as I would like but not cold at all.
Turning the volume knob all the way - shows no background noise.

So my breadboard is successful up till now.
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Old 4th October 2013, 09:31 PM   #64
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Quote:
Originally Posted by triode_al View Post
Not as warm (tubey) yet as I would like but not cold at all.
I'm not sure that this helps but get my Tda1543's I2S via a CS8412 and after going back through the archives I found that grounding was very important to the final sound.

I therefore have two set ups - one with the analogue and digital grounds merged early on for the nice tubey warmth that helps my electronic music cd's.

The other has the A/D grounds kept separate until a star ground is applied. This gives a nice cold/harsh but alive feel for my 70's rock cd's.

My point is that the final sound is (of course) also affected by matters upstream of the DAC.
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Old 7th October 2013, 10:12 AM   #65
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Quote:
Originally Posted by Flied Egg View Post
I'm not sure that this helps but get my Tda1543's I2S via a CS8412 and after going back through the archives I found that grounding was very important to the final sound.

I therefore have two set ups - one with the analogue and digital grounds merged early on for the nice tubey warmth that helps my electronic music cd's.

My point is that the final sound is (of course) also affected by matters upstream of the DAC.
I found a document on grounding where the idea was to connect as early as possible, the main reason stated for difference between A and D grounds is that the substrate of the chip requests such. In the TDA1543 there is already one pin only. So in effect it has combined A&D.

Quote:
The other has the A/D grounds kept separate until a star ground is applied. This gives a nice cold/harsh but alive feel for my 70's rock cd's.
Assume this is the cdtubed. Just pondering. Might the long distance to the star ground have inductance on the chip? Would decoupling locally have any effect?
Attached Files
File Type: pdf staying_well_grounded.pdf (464.9 KB, 39 views)
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Old 9th October 2013, 07:05 PM   #66
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Quote:
Originally Posted by triode_al View Post
I found a document on grounding where the idea was to connect as early as possible, the main reason stated for difference between A and D grounds is that the substrate of the chip requests such. In the TDA1543 there is already one pin only. So in effect it has combined A&D.

Having had a bropwse around I think this is a peculiarity with the CS8412 and not a general thing.

The chip is rather old so I can't find more info but this site refers to the effect at the bottom of the page.

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Old 11th October 2013, 07:21 AM   #67
Zoran is offline Zoran  Serbia
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triode Al could You post last diagram of output stage you used?
tx
(it is not quite clear tome what You did on the L/R ots pins and Vref pin)
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Old 11th October 2013, 11:26 AM   #68
EUVL is offline EUVL  Europe
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> sen can't have any dc offset on it's input.

Of course it can.
Else how would all these ES9018 builds function perfectly.

And those who insist on wiring SEN to a fixed (instead of floating) supply, or using the same supply for both channels, simply do not understand how the circuit works. They are much better off using the cascoded CEN from Loesch.

Zen -> Cen -> Sen, evolution of a minimalistic IV Converter


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Old 13th October 2013, 08:42 AM   #69
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Quote:
Originally Posted by Zoran View Post
triode Al could You post last diagram of output stage you used?
tx
(it is not quite clear tome what You did on the L/R ots pins and Vref pin)
Here is my last incarnation. Floating pin 7 sounds best. Great thanks!

I-V for single 1543.jpg

I have some further thoughts on the output. Room for further investigation.
As for nowe, I am pretty happy.

I tried the filter (sans the 470 ohms) directly on the output, but this has influence on the highs (not a bad one though).

The filter tested with 510 ohms (35 ohms generator + 470 input) gives - 1dB at 20 kHz; this is only achieved with the 2,7 nF at the output. With 2n7 there, the bridging cap is sensitive and determines the dip (notch); I tested experimentally and found 940-960 was giving me the nulling at exactly 176 kHz.
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Old 13th October 2013, 08:45 AM   #70
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Quote:
Originally Posted by abraxalito View Post
Here's a first stab - its assuming the 1mHs have no frequency dependent losses - a major assumption. The working impedance is 100R, set by the desired corner freq and your inductors.
Having the filter after the buffer I can now easily test this design
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