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tda1387 dac pcb "front end"
tda1387 dac pcb "front end"
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Old 29th September 2018, 02:46 AM   #271
stellarelephant is offline stellarelephant  United States
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Sort of OT, but since we are sharing different 1387 boards, I have to say that the Audiophonics board sounds remarkably good. I pulled the Nichicon ES output caps and after trying the usual suspects, settled on some 0.33uF WIMA MKP4, which made a big improvement. They are in parallel with the input caps of my amp, otherwise I couldn't get away with such a small value. I am also using a new OPC regulator to feed the Pi courtesy of Greg Stewart. The detail is great (maybe 8x chips really does help?) and tonality is full and vivid...very satisfying.
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Old 29th September 2018, 02:02 PM   #272
Alexandre is offline Alexandre
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Quote:
Originally Posted by matt_garman View Post
[*] Balanced output: the Soekris supports it out of the box via opamps; you could implement the same fairly easily for the cheap board (or likely buy the equivalent). Going balanced dual mono with Soekris doubles the cost. Also, read Alexandre's comments above on balanced vs single-ended: I'm personally re-considering the need for balanced interconnects.
Matt, thanks for the consideration.

The main point I was trying to make is that doubling up the DACs to make a "balanced" signal (perhaps we should call it differential, or symmetric, rather than balanced) is not the way to go, in my opinion. I find that it alters the harmonic distortion in a non-musical way. It just doesnīt sound as good as a single dac, or two paralleled dacs.


A less important note, balanced actually means balanced impedance. Usually, all you need is one extra resistor to make a balanced signal from a single ended source. Then your receiver should be able to use the difference between hot and cold, and ignore ground noise. Itīs all in that article by Bruno putzeys: the g word


(About harmonic distortion. Some people are paying $7000 for a box that produces some adjustable second and third harmonics. This product is a hit, apparently. Take a look: Vertigo Sound VSM-2 Mix Satellite MK2 - Full Version - Vintage King Pro Audio Outfitter

I tell you, why not use a TDA1543 and passive I/V instead? I think the outcome will be close to the above box used with typical settings. I actually like the 1543 and passive I/V, but I also like the cleaner low distortion active versions I made. It depends on what you listen, and sometimes it is just nice to make a change.)

Thanks,
Alex
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Old 29th September 2018, 03:12 PM   #273
matt_garman is offline matt_garman  United States
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tda1387 dac pcb "front end"
Quote:
Originally Posted by stellarelephant View Post
Sort of OT, but since we are sharing different 1387 boards, I have to say that the Audiophonics board sounds remarkably good. I pulled the Nichicon ES output caps and after trying the usual suspects, settled on some 0.33uF WIMA MKP4, which made a big improvement. They are in parallel with the input caps of my amp, otherwise I couldn't get away with such a small value. I am also using a new OPC regulator to feed the Pi courtesy of Greg Stewart. The detail is great (maybe 8x chips really does help?) and tonality is full and vivid...very satisfying.
I don't think it's offtopic, IMO anything tda1387-related is fair game in this thread.

I've always been curious to try that DAC. I have more tda1387 DACs than any sane person needs (though I suspect Abraxalito has me beat!) There is a very similar one from TeraDak. If you haven't already, take a look at this thread, Improving passive I/V for Pi dac 8 x TDA1387. That's about the TeraDak model. But if you take the time to back out the output schematic for your Audiophonics, there's a chance it might be similar to the TeraDak. If so, that thread demonstrates that the stock output filter may not be optimal.

Don't you mean that your DAC output caps are in series with your amp's input caps?

What is the board on your stack between the RPI and Kali?


Quote:
Originally Posted by Alexandre View Post
A less important note, balanced actually means balanced impedance. Usually, all you need is one extra resistor to make a balanced signal from a single ended source. Then your receiver should be able to use the difference between hot and cold, and ignore ground noise. Itīs all in that article by Bruno putzeys: the g word
Thank you for the clarification. I've always used those terms interchangeably, but I see that's imprecise. It's been a while since I've read "The G Word" (obviously!), it's probably time to re-visit.


Quote:
Originally Posted by Alexandre View Post
I tell you, why not use a TDA1543 and passive I/V instead? I think the outcome will be close to the above box used with typical settings. I actually like the 1543 and passive I/V, but I also like the cleaner low distortion active versions I made. It depends on what you listen, and sometimes it is just nice to make a change.)
When you say "the above box", to which are you referring? We've discussed lots of DACs in this thread.

It's funny you mention 1543. My very first NOS DAC was one of those cheap 4x Muse tda1543 USB-powered DACs. I didn't like it. There's a huge thread on Head-Fi that discusses numerous mods for it. At the time my skill level was lower (not to imply it's high now) so I didn't understand the nature of several of those mods, so only did the absolute simplest. I remember liking it a little bit in some cases, but something I noticed in cymbals really turned me off.

I dismissed NOS until I got the tda1387x8 DAC, and I've been obsessed ever since. I've always wanted to go back and give the 1543 another try, now that I have a little more experience. The only problem is time! Too many projects!
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Old 29th September 2018, 03:58 PM   #274
Alexandre is offline Alexandre
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Matt

Quote:
Originally Posted by matt_garman View Post
When you say "the above box", to which are you referring? We've discussed lots of DACs in this thread.
I meant the distortion box! The one I wrote about. Second and third harmonic generator. I actually downloaded a trial of a plugin that models said distortion box, and listened to the results with my clean DAC. I tell you, a dac with tda1543 + passive I/V has a similar sound to the $7000 distortion generator.

I have to revisit the 1387.

BTW, I get very good cymbals and top end in general by using transformer coupling. Has to do with the filter function of the trafo, certainly. I still havenīt tried a high order filter like Richard does.

-Alex
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Old 29th September 2018, 04:08 PM   #275
Alexandre is offline Alexandre
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The thing about the 1543 is that you have to select chips. There is a lot of variability. I believe John (ECDesigns) has gotten to the bottom of this, he says the MSB is the least accurate of all bits, and only 5% of all tda1543 are really good.

With 1387 you donīt need to worry about this. It uses segmentation, aka sign magnitude, which mitigates any lack of MSB accuracy and the zero crossing problem (all bits change state at the same time during the zero crossing with TDA1543 and 1541).

-Alex
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Old 1st October 2018, 01:54 AM   #276
stellarelephant is offline stellarelephant  United States
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Quote:
Originally Posted by matt_garman View Post
But if you take the time to back out the output schematic for your Audiophonics, there's a chance it might be similar to the TeraDak. If so, that thread demonstrates that the stock output filter may not be optimal.
Looks like the same exact circuit with a slightly different layout, better connectors, and a 4 extra electrolytics. So according to Abraxalito, in addition to some NOS droop correction, there is a 1dB bass boost built in with the stock filter on this board...lol maybe that is why these low value output caps are working out for me?

Quote:
Originally Posted by matt_garman View Post
Don't you mean that your DAC output caps are in series with your amp's input caps?
Well, it isn't what I meant, but I'm sure it is what I should have meant. I have a lot to learn, obviously!

Quote:
Originally Posted by matt_garman View Post
What is the board on your stack between the RPI and Kali?
That's IanCanada's IsolatorPi. To my ears, it makes the Pi a much better player.
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Old 11th October 2018, 12:46 AM   #277
PJN is offline PJN  United States
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Quote:
Originally Posted by matt_garman View Post
It won't really be a mod, just soldering wires directly to pins 1, 2 and 3 of the DAC IC.




No pins for a pot. But I don't see why you couldn't hang one off the output.




Please post your thoughts and impressions when you get it! My (decidedly non-golden) ears say it's pretty decent.


Attached are some better pics.
Hi Matt,

I finally received my "little giant" and had the chance to hook it up for a short listen tonight. It seemed a little unfocused at first, but after I let it burn in for 1/2 hour or so it tightened up nicely. I agree with you, for the money it sounds great. Compared to a PCM1794 EZ dac that I have in the same system and after only a very brief listen without swapping in and out a few times, my impression is that the EZ dac has a lower noise floor, seems more dynamic, and images better. The little giant is smoother/softer around the edges, and doesn't bring as much background ambiance. I preferred my Subbu dac to the EZ dac as it had more detail and lower noise floor to my ears. I want to let is burn in and settle for a few hours before I give it a serious A/B comparison with my other dacs. Besides the EZ dac I have a dual mono Opus dac from twisted pear. But so far for the money it's a no brainer.

Paul
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Old 11th October 2018, 01:26 AM   #278
abraxalito is offline abraxalito  United Kingdom
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If you're interested in ideas for modding the 'little giant' we're talking about it over here : AliExpress AD1865 R2R DAC
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Old 11th October 2018, 01:50 AM   #279
PJN is offline PJN  United States
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I also have one of those on the way also. I've been watching both threads.
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Old 15th October 2018, 11:40 PM   #280
drpro is offline drpro  United States
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tda1387 dac pcb "front end"
A bit late to the build. Anyway finished a TDA1387 balanced DAC. I am using a Pi 3. Volumio is the software I have been using on a Pi, Kali, Piano. That combo works well together.
I am having no joy with this build. I am guessing I may have soldered the ICs incorrectly or overcooked them on the hot plate. Also, when I configure Volumio it asks for which DAC is installed. Quite a few listed, so perhaps that is also a problem.
I have attached photos in showing how the devices are mounted. The first photo closest to the 40pin has them all right reading. Second photo is from the output side.
Any thoughts appreciated.
David
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File Type: jpg TD2.jpg (328.8 KB, 30 views)
File Type: jpg TD1.jpg (270.9 KB, 32 views)
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