[Sapientiam]

No need to spend hours and hours modding the DAC-AH now with this new offering out of China - http://www.cart100.com/Product/42124644877/
 
With only an hour or so of minor mods this DAC pulls ahead of a typically modded DAC-AH and at a lower price too. We have a thread running on DIYA documenting the on-going modding progress -  http://www.diyaudio.com/forums/digital-line-level/269199-tda1387-x8-dac-lets-check-its-design-mod-not-play-music-not.html

 

[DavidK35]

According to the specs in your link, it is only available in 220v. So what use would that be here in the U.S.?
 
Also in your other thread it seems without a lot of mods the comments are the top end is somewhat ragged.
Doesn't that defeat somewhat the purpose of using a NOS TDA chip in the first place?. I thought they had a vinyl like
non digital/non fatiguing top end?

 

[Zulkr9]

Any instruction or guide on how to mod this dac to passive ? 

 

[EKepa]

Well gentleman, not sure it's a good idea to bump an ancient thread like this one. However it's 2020 now and it must could be hardly beleived back there in 2001 that these DAC-AHs will be for sale, and there will be some enthusiasts modding these DACs
Purchased one recently, quite happy with it, but best is the enemy of good. I must have collected all the info available regarding all possible mods for this small black box. I lean towards passive mod with recap, new resistors, new bridge rectifiers, rcas, and some other minor changes. Have two questions and strongly believe that there is still somebody to help me to find the answer. This is the biggest DAC-AH thread over the Net though.

1. I've seen some folks changed C1 and C2 caps for polypropylenes like Mundorf or PIO ones. Does it make any sence taking into account that these caps are responsible for digital signal?
2. It seems that 18V AC is used only for opamps. Does that mean that I can just cut the two AC wires and completely remove everything on the right side as well (I mean opamps themselves, BR3, C29-30, C38-39 and so on)?

The scheme attached.

 

[zaccio]

Hi EKepa, nice to see some people playing with this vintage DAC yes I think the 18v is for opamps but you should consider the Lampizator mod http://lampizator.eu/LAMPIZATOR/REFERENCES/AH DAC/AHDAC.html it brings this DAC to another level. I connected my tube output stage from the lampucera kit and the result is quite interesting. Now I would like to connect directly in I2s and feed the 1543's with clean battery power. After playing with Havana, LITE 50, ESS 9038q2m time for 1543

 

[]eep]

this little dac has plenty of potential but it's not made very well. I've done some mods on it, and other 1543 dacs. 3 things to notice:

-don't feed the 1543 their Vmax of 8V, stay at 7V for longevity.
-the output stage of the 1543 is very simple: just a 470 Ohm (or 560) resistor between signal and ground. It does not need amplification. The output will be 3V + signal (so signal between 0 and 6V). An output capacitor is just to bring that offset down to 0 (signal + to - 3V) but since most amps usually use an input cap first i find that kind of double. So i leave it out. The only downside is slight crackling when you turn the volume but there is no better cap than no cap (and nothing cheaper). It sounds more open and clear.
-take your signal just after the 1543 chips right next to them (follow pin 5 and 7 for R and L) , they lead to a resistor (iirc after 10y, desolder that and anything after that is disconnected), take the signal before it goes anywhere and lead it straight to the output. Short the output with 470R and you're done. Easy peasy.

I still use my Teradak which is just a better version of a 8x 1543, same mod, and just purchased a Denafrips for at home. It's newer, more versatile, better. But the 8x1543 comes uncomfortably close! So good luck.

 

[zaccio]

I removed the pot as it was not possible to adjust the 3,3v or 3,85v (nothing happens when you turn the screw) and I measured the same 5,8v and 2,2v on the 1543 pins how is it possible?

 

[]eep]

i think because a fixed resistor is deciding the max output of the LM7808 power regulator. 5.8V is low-ish. You might want to take it to 7 for some more dynamics.

I looked op the board, R35 and R36 is where you want to steal your signal from. Desolder them on 1 side next to the chips and go straight to the output. Only apply an R (.. C) and youre done

 

[zaccio]

It's writen LM7808 on the board but I measured 6v on the regulator. I have the possibility to feed by battery the direct connection is R35/R36 ? And I would like to connect in I2s I can see the tracks from the CS8414 controller one is R17 and other R12 but where go the third? (you need lrck bck data and the ground)

 

[]eep]

you need to look up the schematic or whitepaper for the LM7808. The combination of attached resistors determines the output.

https://electronics.stackexchange.c...-do-i-change-the-output-voltage-of-the-lm7805
(or find your own)

R35/36 are at the OUTPUT of the TDA1543. You don't want power on that. Thats where you direct the signal to the output plugs (bypassing the opamps and filter).

 

[zaccio]

changed the regulators it's quite hot now (3,8v) but sound really nice now no more distortions

 

[]eep]

it looks like you got it. I can't tell what you chose as output impedance but you can hear the difference readily if it's not good

 

[zaccio]

yes the difference is there is no more saturations on forte (had to put resistors on output signal before) with the cheap chinese tube output from Lampucera DAC kit it's really nice better than my previous modified Havana, Lite DAC 60 more dense, organic and engaging sound. Will upgrade the tube output later. I understand why Lukasz Fikus from Lampizator find the sound of AH addictive.

 

[]eep]

erm... reads as if you put resistors IN/before the output + where the right resistor value should be a short from +to - (ground). With the right value you shouldn't get any problems in fff. I have a testtrack of a piano intro that instantly reveals any wrong value for the output (especially D/S dac output stages trip over this). track: 'A praya deserta' from the album "Casa" by Sakamoto & Morelenbaum². You'll know in 2s if it distorts.

 

[zaccio]

Before the mods in 6v I had put resistors on output signal now with the 8v mods I don't need any resistors will try to connect by I2s one day if I'm not too lazy...you can get more transparency with I2s I've heard the difference on my ES9038Q2M board