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Building the ultimate NOS DAC using TDA1541A
Building the ultimate NOS DAC using TDA1541A
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Old 28th September 2018, 02:26 PM   #6531
batteryman is offline batteryman  United Kingdom
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Join Date: Jun 2011
Location: SCOTLAND
Building the ultimate NOS DAC using TDA1541A
Quote:
Originally Posted by poki921 View Post
It not a mystery
The 0.1uF is low impedance for the pin
Itís like a well near your house you wonít seek the water from the lake
Although itís not far away a much bigger
The electronics are lazy as we are.
Quite good analogy. Those lazy electrons can holiday in the 0.1uf caps and the more energetic can relax among friends in the 100uf cans.

On my dual dac pcb I have allowed for both 0.1 and 100uf but if I fit these, the 0.1 will have to be soldered on the underside which is not a problem. (no smt parts, as my hands shake too much and my eyesight is not exactly 20:20 even with reading glasses - its old age!)
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Old 28th September 2018, 02:47 PM   #6532
poki921 is offline poki921  Taiwan
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I can do this favor but I think we’re far away
I’m in Taiwan
Frankly speaking listening is believing
Maybe it’s not so sensitive there,but I doubt it
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Old 28th September 2018, 02:49 PM   #6533
sumotan is offline sumotan  Indonesia
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Join Date: Oct 2013
Well Poki921 if it was local decoupling I would never question it but in this
context the itís working on different duties hence.

Cheers
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Old 28th September 2018, 02:54 PM   #6534
poki921 is offline poki921  Taiwan
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Quote:
Originally Posted by sumotan View Post
Well Poki921 if it was local decoupling I would never question it but in this
context the it’s working on different duties hence.

Cheers
Why not?I don’t get it


IS that the Cext on fig11 here?
http://s-audio.systems/public/upload...s/00046328.pdf

Last edited by poki921; 28th September 2018 at 03:10 PM.
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Old 28th September 2018, 03:08 PM   #6535
sumotan is offline sumotan  Indonesia
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Hi Poki921 Im Taiwanese too. lol
Why not, cause I'm not so sure.
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Old 28th September 2018, 03:21 PM   #6536
poki921 is offline poki921  Taiwan
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Quote:
Originally Posted by sumotan View Post
Hi Poki921 Im Taiwanese too. lol
Why not, cause I'm not so sure.
quiet small world
Did we met before?
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Old 28th September 2018, 03:22 PM   #6537
sumotan is offline sumotan  Indonesia
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D
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Old 28th September 2018, 03:23 PM   #6538
sumotan is offline sumotan  Indonesia
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Donít think so, Iíve been away like coming 12 yrs already.
Yep small world.
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Old 1st October 2018, 11:01 AM   #6539
koldby is offline koldby  Denmark
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A little story on my progress in TDA1541A DAC building.
I modded two Red Baron PCB to accept 50 Hz DEM mod and used them with Ian Canadas I2S to PCM converter in balanced mode and with passive I/V converter. This immediately bettered my, uptil now , preferred DAC with Ian Canadas FIFO and dual clock with isolator and custom designed I/V converter.

I had to dismantle it again as it was kind of a rats-nest construction and I want to put it in a nice box with remote vol. control etc.
So I had a third red baron pcb and I just got two pcb from ryanj with ecdesigns version of a I2S to Simultaneous converter (worked perfectly first time , thanks ryanj!) and I wanted to make a dac I could use , while building the balanced dac (it also needs to have 4 channels, as I want to make a digital corssover for future subs).

The dac was unmodded (besides 1uF acrylic SMD capacitors for DEM decoupling) and had the original single MOSFET I/V converter. Hmmm good but not great. Then I switched to passive I/V converter and I got a step closer, but not enough. I then modded it with 50Hz DEM and , wow, what a difference! This is a very good mod especially when you run the TDA1541A in simultaneous mode... Spaciousness and perspective is much better and the there is black darkness in the space between and behind instruments, so you can easily hear the recorded rooms response to the instruments..
The output from the passive I/V is too low for my amps , and I did not have a good enough preamp to deal with that, so I desided to try to mod. my TDA1543 I/V converter to work with TDA1541A. It was rather an easy mod and now I had plenty of output to my amps. Comparing the passive I/V to the modded active I/V, @ the levels that the passive could obtain, showed that the active was at least on pair with the passive solution. I had to turn down the digital vol quite a lot for the active I/V and I get lesser resolution that way. When I turn up the vol. the active performs even better.

The active showed me, when the digital vol was turn way down, that there was some noise overlaying the weak signals. Most of it was probably quantization noise, but when I added 100nf smd parallel to the 100 uF DEM capacitors, it was reduced, so I would recommend that.

Both the MOSFET I/V and the modded I/V (also a non-feedback circuit) have way lower distortion figures than the passive solution (FFT analyzer result)....Makes one wonder ...........

Concerning the I/V stage: I like MOSFETS and especially JFets as input devices and prefer them to bipolar, but in the event of an I/V converter bipolar are IMHO much better. They shine when they are used as current operated devices (that is their nature).



I hope this can be used as inspiration for others, but it is only my personal observations and of course subjective..
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Old 1st October 2018, 12:19 PM   #6540
batteryman is offline batteryman  United Kingdom
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Join Date: Jun 2011
Location: SCOTLAND
Building the ultimate NOS DAC using TDA1541A
Quote:
Originally Posted by koldby View Post
A little story on my progress in TDA1541A DAC building.
I modded two Red Baron PCB to accept 50 Hz DEM mod and used them with Ian Canadas I2S to PCM converter in balanced mode and with passive I/V converter. This immediately bettered my, uptil now , preferred DAC with Ian Canadas FIFO and dual clock with isolator and custom designed I/V converter.

I had to dismantle it again as it was kind of a rats-nest construction and I want to put it in a nice box with remote vol. control etc.
So I had a third red baron pcb and I just got two pcb from ryanj with ecdesigns version of a I2S to Simultaneous converter (worked perfectly first time , thanks ryanj!) and I wanted to make a dac I could use , while building the balanced dac (it also needs to have 4 channels, as I want to make a digital corssover for future subs).

The dac was unmodded (besides 1uF acrylic SMD capacitors for DEM decoupling) and had the original single MOSFET I/V converter. Hmmm good but not great. Then I switched to passive I/V converter and I got a step closer, but not enough. I then modded it with 50Hz DEM and , wow, what a difference! This is a very good mod especially when you run the TDA1541A in simultaneous mode... Spaciousness and perspective is much better and the there is black darkness in the space between and behind instruments, so you can easily hear the recorded rooms response to the instruments..
The output from the passive I/V is too low for my amps , and I did not have a good enough preamp to deal with that, so I desided to try to mod. my TDA1543 I/V converter to work with TDA1541A. It was rather an easy mod and now I had plenty of output to my amps. Comparing the passive I/V to the modded active I/V, @ the levels that the passive could obtain, showed that the active was at least on pair with the passive solution. I had to turn down the digital vol quite a lot for the active I/V and I get lesser resolution that way. When I turn up the vol. the active performs even better.

The active showed me, when the digital vol was turn way down, that there was some noise overlaying the weak signals. Most of it was probably quantization noise, but when I added 100nf smd parallel to the 100 uF DEM capacitors, it was reduced, so I would recommend that.

Both the MOSFET I/V and the modded I/V (also a non-feedback circuit) have way lower distortion figures than the passive solution (FFT analyzer result)....Makes one wonder ...........

Concerning the I/V stage: I like MOSFETS and especially JFets as input devices and prefer them to bipolar, but in the event of an I/V converter bipolar are IMHO much better. They shine when they are used as current operated devices (that is their nature).

I hope this can be used as inspiration for others, but it is only my personal observations and of course subjective..
Thanks for the write up, always interesting to hear from other 1541 users. My own design of dual sim mode 1541 Dac pcbs for use with IanC's I2Sto PCM interface are on their way from Chinas this week.
I designed it for the 50Hz dem capacitors and there is no onboard I/V as I use Sowter's 9545 transformers. I hope to start listening tests next week.

My 1U dac case will also house a dual Ad1865 and a quad AD1820 dac pcb
for comparison. Ultimately one will be for CD replay and one of the others used with a USB to I2S adaptor for Youtube music video listening. (I will need to connect a few gates together to convert I2S into the pcm the AD chips require)
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