Experience with this DIY DAC ?

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#3,663
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#3,664
Jim Leach said:
OK. I am getting back to this project after a long hiatus.

I am up to date on the reading (my eyes hurt!) and had a couple questions.

1) the Lundhal LL1690s seem to be the favored transformers from several sources, some of whom have tried many flavors. What is the best place to get these babies today?

2) If I understand correctly, I could run balanced OR single ended output. Could I possibly have two sets of connectors on the back of my unit to allow both? If so how?

3) in the case of the transformers, there apparently needs to be filter caps and some resistors as well. I have seen several examples, and at least one person using it 'bare'. What is the current 'state of the art' with regards to the components to be used in conjunction with the transformers?

4) I read something regarding the use of caps rather than transformers for output (but transformers seem to be favored). Are there any advantages to this scheme over the transformers?

5) I am reasonably certain the coax input will be relocated to the rear of the unit (remote of the board). I believe I therefore need a 'proper' RCA connector- i.e. not just a plain old audio one right? What exactly do I need, and where is a good place to get it? (or will an audio one work fine?)
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There really is no proper RCA for digital, they are the wrong impedance, but the manufacturers use them any way. You can switch to BNC or even F connectors if you like, or just use RCAs.

The Lundahl 1690 and the Jensen JT11-DMs or BMs seem to be the top choices, but the Jensens are way cheaper over here.
 
#3,666
The impedance rating has no direct bearing on the sound, the quality of the design and construction has everything to do with it.

Please go to the Jensen website and read the article by Bill Whitlock about audio transformers. Your questions will be answered.

Best, Bill
 
#3,667
milen007 said:
hi guys

i am learning bout LOT. as 600:600 is used in this application. i am wondering what happen if 1k:1k is used? whats the effect to the sound in particular?

thanks in adv

erwin
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Bill is correct about the Jensen article, it is quite useful.

One thing that will probably differ between the two transformers is the inductance in the windings. The consequence is that that depending on the load input impedance (somewhat) and the source output impedance (strongly), you will be creating a high pass filter and reducing the low freq response. Most manufacturers do not list the inductance, so you may need to experiment.
 
#3,668
Bill Fuss said:
There really is no proper RCA for digital, they are the wrong impedance, but the manufacturers use them any way. You can switch to BNC or even F connectors if you like, or just use RCAs.

The Lundahl 1690 and the Jensen JT11-DMs or BMs seem to be the top choices, but the Jensens are way cheaper over here.
Click to expand...

Thanks for that info Bill. Since I am integrating with 'commercial' transport and preamp before and after, respectively, I want this to be 'robust' and able to handle future changes before and after if they occur. Obviously tailoring everything in the chain is best; however I have to be practical for myself as well.

I have no doubt this gizmo will sound so much better than my Aragon D2A (version 1!) so I will be happy!😎

PS a member here has provided me with some Lundahls so I'm going for them! Just a few details to sort out and I'll be sniffing solder fumes!😛
 
#3,669
Hi All. I recently received a completed DAC that is based on this diy project. It came with the dual LME49720HA op-amp installed and with 2 others in reserve : a dual LT1363 and a dual OPA627. I presume the effect of exchanging one op-amp for another would be tonality changes. Can someone point me to a page or link where I could learn of these differences in tone?

Thanks very much.
 
#3,670
msjjr said:
Hi All. I recently received a completed DAC that is based on this diy project. It came with the dual LME49720HA op-amp installed and with 2 others in reserve : a dual LT1363 and a dual OPA627. I presume the effect of exchanging one op-amp for another would be tonality changes. Can someone point me to a page or link where I could learn of these differences in tone?

Thanks very much.
Click to expand...

To be honest the whole op-amp thing is subjective and opinions will vary as much due to equipment and set up as well as musical tastes.

I preferred LME49720HA to OPA627 but don't ask me to use subjective hi-fi speak - it just made the music sound better.

You could do a search on the forums for the op-amp models in question but really you should plug them in and have a listen. It's the only way to find out 😉
 
#3,674
If anyone is planning on running output trannies instead of opamps (eliminating the 15v supply), you can get a real dirt cheap power tranny here: 8V/1.6A Multi-Tap Transformer

I bought several of these and am running one in parallel (@ 1.6A) in the DAC. Well made Tamura and it works great!

BTW, I am now using the Edcor's for the output. Does it sound better than opamps? I don't know. If I can't A/B them on the fly I can't tell 😱
 
#3,679
I'm having some troubles with this DAC not sounding so great (Lars V1.0 08/2010), so I have been diggin' into it with a scope and my ears 🙂
It's a lot of fun so far, started with CS8416 mods:
Added 0.1uF+2.2uF SMT decoupling caps on VD and VA, added 100uH inductor between VD and VA. That cleaned up the rails.
Added 47k pullup to pin 20 TX ;is only good 32-108kHz, beyond this i.e 192kHz "loss of PLL lock may occur"
I did not yet update the PLL filter from 10nF/1K/22nF to 1nF/3K/22nF;
The RMCLK signal is pretty mushy and I have to verify timing.

This gives quite an audible improvement at 44kHz. It sounds cleaner, less grit with loud passages and fine detail is more consistent.
With the upsampler, I didn't hear a difference although the board is still needing work.

I find the small Elna electrolytics on the board are crap. The are showing high ESR/DF and high leakage so I am swapping them out.
 
#3,680
As I recall, both of mine have Nichicon Muse caps. The boards are so damned hard to desolder on the older ones it's a real gamble. I changed the PLL filter first thing, never saw the app. note. on the pullup. I primarily use the one that still has the 8416 with a Squeezebox, probably all 44khz.
 
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