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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
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Old 4th October 2017, 04:45 PM   #431
matt_garman is offline matt_garman  United States
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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
Quote:
Originally Posted by DrDick View Post
Tried some of the things you suggest. Connection w/o the case did not gain any profit. Connection via toslink - no sound at all, maybe the toslink input is broken. The board itself looks a bit different from Malefoda's pic.
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Oh, that board is indeed very different than the main subject of this thread. So what I said about RCAs being output-only, and everything else being input, is true only for the main subject of this thread. I am unfamiliar with your board!

Is there a pot (volume control) on your board? If you have a way of controlling volume in some other way (e.g. downstream component, such as integrated amp, or upstream component, e.g. digital/software volume control) - can you try turning the pot all the way up (i.e. full volume)? Pots themselves can sometimes introduce noise.

Another general idea: put a resistor across the signal and ground of each RCA output. Maybe try 100k ohm. (To be clear, you need two resistors, one for left-channel and one for right-channel.)

Is that powered via USB? Or does it take dedicated power input? Another thing to try, if it's powered via USB, is to use USB only for the signal, and provide power from a known good/clean 5V power supply. You can buy pre-made USB cables that do exactly this (they are literally "Y" shaped, where you provide the USB signal into one part of the Y, and 5V power into the other part of the Y). But you can hack up your own pretty easily by looking up the USB pinout reference.

Does that have a headphone output? If so, have you tried it to see if it also hisses?

Do you have a link to the sales listing?
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Old 5th October 2017, 01:49 AM   #432
abraxalito is online now abraxalito  United Kingdom
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That DAC I haven't seen before though I'm fairly sure its from the same vendor. There looks to be a headphone amp IC (the 8pin SOIC) and it has passive I/V rather than opamp. Note that the 620ohm resistors in the passive I/V stage are too high in value - they'll cause clipping about 3dB before digital full scale. Reduce them to 390ohm.
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Old 5th October 2017, 08:19 AM   #433
DrDick is offline DrDick
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Quote:
Originally Posted by matt_garman View Post
Oh, that board is indeed very different than the main subject of this thread. So what I said about RCAs being output-only, and everything else being input, is true only for the main subject of this thread. I am unfamiliar with your board!

Is there a pot (volume control) on your board? If you have a way of controlling volume in some other way (e.g. downstream component, such as integrated amp, or upstream component, e.g. digital/software volume control) - can you try turning the pot all the way up (i.e. full volume)? Pots themselves can sometimes introduce noise.

Another general idea: put a resistor across the signal and ground of each RCA output. Maybe try 100k ohm. (To be clear, you need two resistors, one for left-channel and one for right-channel.)

Is that powered via USB? Or does it take dedicated power input? Another thing to try, if it's powered via USB, is to use USB only for the signal, and provide power from a known good/clean 5V power supply. You can buy pre-made USB cables that do exactly this (they are literally "Y" shaped, where you provide the USB signal into one part of the Y, and 5V power into the other part of the Y). But you can hack up your own pretty easily by looking up the USB pinout reference.

Does that have a headphone output? If so, have you tried it to see if it also hisses?

Do you have a link to the sales listing?
Powered via USB. The idea for a separate power source sounds great. Something like this, I believe? Wholesale USB 2.0 DUAL Power Y Shape to Mini Cable - 1M
A headphone output is there. The noise is there when using it, too.
All in all, this DAC turns out to be a portable version of the stationary one being discussed here. The specs are in the first post: Hoved-fi - Vis emne - Lee Portable L1387 DAC/AMP The selling page
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Old 26th November 2017, 04:10 AM   #434
museguy is offline museguy  Mexico
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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
Dear abraxalito and Matt,
Thought I would move my questions into the TDA1387 thread.


So far I have:
1. Op-Amp Replacement with AD845
2. Removed 2n2 Opamp Feedback Capacitors

Trying to follow along to the TDA1387 mods, seems next is to increase Capacitance Across TDA1387 pin7.

Seems future mods include LC filter, passive IV and removing the opamps.

Thank you for the guidance.
- Mark
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Old 29th November 2017, 10:27 PM   #435
matt_garman is offline matt_garman  United States
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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
Hi Mark, sorry for the delayed reply. At any rate - I don't see an actual question in your post. Did you just want a suggestion on the next steps? Or clarification on a specific mod?
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Old 7th December 2017, 01:56 AM   #436
museguy is offline museguy  Mexico
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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
Default Removing Opamps

Quote:
Originally Posted by matt_garman View Post
Hi Mark, sorry for the delayed reply. At any rate - I don't see an actual question in your post. Did you just want a suggestion on the next steps? Or clarification on a specific mod?
Hi matt_garman,
Thank you for getting back to me.

Have you modded your TDA1387 x8 to remove the opamps ? I believe the attached photos are the work of Malefoda. How does the sound change without the opamps ?

I believe without the opamps it becomes an all discrete DAC.

Thank you,
- Mark

P.S. So far I have:
1. Op-Amp Replacement with AD845
2. Removed 2n2 Opamp Feedback Capacitors
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File Type: jpg Screen Shot 2017-12-06 at 8.50.20 PM.jpg (139.4 KB, 116 views)
File Type: jpg Screen Shot 2017-12-06 at 8.50.33 PM.jpg (129.7 KB, 115 views)
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Old 7th December 2017, 06:30 PM   #437
matt_garman is offline matt_garman  United States
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TDA1387 x8 DAC: let's check its design, mod it -or not-, play music -or not! :(-
Hi Mark,

No, I never modded this DAC to work without opamps. That's partially due to not having as much time as I'd like to work on these things, and also partially having some neurosis for neat and tidy work. I couldn't see any easy way to build the discrete circuit and keep things reasonably contained in the stock chassis. (There's a practical reason too: I have young kids running around, so it's not safe to leave a rat nest of live electrical stuff out where they can get to it.)

I could have moved the PCB into a bigger chassis, but it doesn't have any screw holes.

At any rate, that's a big part of why I designed the front end, so I could easily (and neatly) play with downstream filters, I/V stages, etc.

On your x8 DAC, I would try to add in the extra capacitance on pin7 of the tda1387 chips. At least in my case, I felt that was the one mod that had the most obvious impact, particularly in terms of bass.

Assuming you want to use the original chassis, you'll either have to get small diameter caps to put on the bottom of the board; or you can use bigger caps by soldering directly to the tda1387 chip pins (solder across pin7 (positive lead) and pin4 (ground)).
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Old 9th December 2017, 03:03 PM   #438
sgbb is offline sgbb
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Does anyone think replacing the 12.000 mhz clock with a better one will be beneficial to the SQ?

Best,
Mark
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Old 13th December 2017, 07:06 PM   #439
Malefoda is offline Malefoda  France
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Mark and Mark,
about the XO I am no expert but I don't think so, it's the source selector's IC under these 12MHz.
My DAC still runs opamps, AD845. The tiny boards on my pictured PCB are just tiny opamps adapter boards. But the DAC in the middle of the thread, USB powered, does run without opamp. Sound depends on next step's impedance. In my case bad sound.
Feed it with super clean SPDIF, the CS8416 is not the chip of the century.
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Old 10th February 2018, 09:06 AM   #440
ian21 is offline ian21  England
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Hi music fans,
Is anyone using a raspberry pi as a server with this dac? I cannot get the pi to recognise it over usb, would the hifiberry board the way to go and just use SPDIF?
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