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DAC-AH mini review - Page 2

post #16 of 30

Nice review...

I'm also getting one but a friend is bringing it over from HK. They quoted shipping by air to Los Angeles for $39. In addition, I asked them to have the opamps socketed and they charged me $15. That would make it easier to try a couple of OPA 627 that I have. I also got a extra identical case for $12 and a +- 15V regulator for $9 (you can see all of this in their website). So I plan on moving the transformer to the other case and installing the regulator board to power the analog (opamp) section.

In looking at the schematic, the output cap may be completely removed, if there is no DC coming out of the opamps (in theory there shouldn't as the opamp has a differential input. But better make sure by measuring it. In any case, if the preamp has a input resistance of 50K, then the cap can be replaced by something of smaller value (maybe 1-3 uF) and of better quality. the MSB link DAC (which I currently have) does not have output caps after the opamp.

In reading the AA boards on modding the MSB link DAC, it seems 80% of the benefits can be obtained by improving the analog power and by replacing the opamp. The use of soft recovery diodes is also popular.

Regards,

Guillermo
post #17 of 30

Got my DAC-AH

Got the DAC this week and have been comparing it with a modded MSB link DAC (the mods only include the beefed up PS, increased voltage regulator to 12 V, the OPA627 and vishay output resistor).

First I measured the DC offset at the output of the DAC chips. 7 volts!, so better use an output cap. I used a 1 uF Multicap film capacitor and increased the output resistance to 200K. The only other mod is replacing the opamp to OPA627.

Compare to the MSB, the DAC-AH has a more forward or accentuated midrange (vocals, sax). The base extension seems the same and the high extension is also the same. In other words, I dont hear a roll off of the highs (due to the NON-OS nature) or decreased base due to the lower value output cap that I put in.

Dac-AH does sound more musical (ie dynamic) and the highs seem less gritty. However the differences are small and you have listen carefully. Overall, I am prefering the DAC-AH with the mods I've made so far.

The PS seems to be of good design and good components. Any mods here would be to "lower the noise floor", - not sure how that would sound.

The mod I would like to try is to use a recloking circuit. The only difficult part (aside from building the clock) is to lift pin M0 of the receiver and power it with 5 volts.

Overall, I am very satisfied with this DAC.

Regards,

Guillermo
post #18 of 30
Sounds great, comparable or arguably better than a $450 dac.
post #19 of 30
link to where i can purchase one of these?
post #20 of 30
http://eshop.diyclub.biz

What mods are there to be done to this?
Does it really take months to arrive?

Has anyone heard the DAC-72?
post #21 of 30

Here is a picture

Shown is the new output cap (original was a 22uF electrolitic) and the new opamp in sockets. Original were opa602.


Photo of Mod

Regards,

Guillermo
post #22 of 30
Thread Starter 
Quote:
Originally Posted by glt
Shown is the new output cap (original was a 22uF electrolitic) and the new opamp in sockets. Original were opa602.


Photo of Mod

Regards,

Guillermo

very cool !! i can not wait until i get all the parts i need to do the mods ...

have you tried the 602 vs the 627's ???

also, can you post pics of the power supply


little update about my dac: my dac is now burned in and the sound is smoother than the first time i tried it (i guess you will notice the change as well in a few days !) , i am using a dvd player as transport via toslink , i am really glad the dac has both toslink and coax ...
post #23 of 30
glt: How did the sound change after the OPA627 and multicap upgrade? How would you rank it with other DACs?
post #24 of 30
Quote:
Originally Posted by mekanoplastik
very cool !! i can not wait until i get all the parts i need to do the mods ...

have you tried the 602 vs the 627's ???

also, can you post pics of the power supply

I have not compared the 602 vs the 627. However, they are both build with the same technology with the 627 being of lower noise. I did compare the 627 vs the original basic Motorola opamp in the MSB DAC. The 627 provided a bit more clear (detail) in the highs (in the MSB). Mostly I can't afford hours of detail comparison as I have two young noisy kids and a fishtank running in the background. The 602 is also a pricey opamp at about $8 each compared to $17 for the 627. The mod that DIYclub did for me, adding the sockets for the opamp, included two new 602 and only cost $15 -very cost effective.

The +- 15 V power regulator I got is of basic design and has an opamp configured as an error amplifier to reduce the voltage ripple. As such, I don't think it will benefit the opamps as they are practically immune to low frequency noise. So I guess I won't be using it. What I intend to do is to move the transformer to the other case and replace the bridge rectifier with low noise diodes (but I'll do this later)....
post #25 of 30
Quote:
Originally Posted by chillysalsa
glt: How did the sound change after the OPA627 and multicap upgrade? How would you rank it with other DACs?
With the original cap and opamp, it seemed less detailed at the top end as compared with the modded MSB DAC. After the cap and opmap mod, they are now equivalent. I think most of the changes are due to the capacitor.
post #26 of 30

DAC-AH mods

Hello,

I want to hear ripped music (APE) from my PC with Sennheiser HD600. DAC-AH has to convert, Rega Ear to amplify.
I have no experience in modding. I want to order DAC-AH, but don't know, wether it makes sense to order some mods additionally. Can somewone give me advice? Does DIYclub makes mods?
I've read this thread, but i don't understand everything.

Thanks, tonatona.
post #27 of 30
Quote:
Originally Posted by glt
With the original cap and opamp, it seemed less detailed at the top end as compared with the modded MSB DAC. After the cap and opmap mod, they are now equivalent. I think most of the changes are due to the capacitor.
Did you have chance to compare modded DAC-AH with the Headroom MicroDAC?

Thanks!
post #28 of 30
any other comments and comparo with other monsters dac on the lite dac-ah ?
post #29 of 30
What would be the best possible output caps I could get that is: readily available and reasonably priced(nothing ridiculous)
Have I got this right; in order to bypass the output stage I would remove the opamps and take the signal that goes from the dacs to pin 3 of the opamps ,connect an output cap to this signal and then connect the caps to the connectors?
post #30 of 30
Question for Mekanoplastik. I am in the U.K and want to buy one of these Dac's. I have emailed DIYClub to ask how much postage is to Europe, but I have had no reply. How much was postage to Madrid. The op-amp sockets were $15 extra ?
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