DAC Mod suggestions

adam2434

I'm thinking about making some mods on a 8X TDA1543 NOS DAC I picked up a little while back. Never soldered before, so this will be a learning experience.

The output stage is totally passive with just I/V resistors and output caps, so I'm thinking that upgrading these parts could be beneficial (see pic, which I copied from Head-Fi).

I/V resistors:
- The blue stock resistors are just run-of-the-mill carbon, 390 Ohm IIRC.
- Any recos for good resistors for I/V conversion?
- I know Caddock is very good.

Ouput caps:
- The stock caps are Kemet tantalum 10uF. I've read not-so-good things about tantalum caps for audio.
- Any recos for output caps?
- I believe this may come down to personal preference, but I'm looking for options. Blackgate N have been suggested elsewhere. I think 10 uF film caps might be to large to fit in the case.
- Another possibility is to keep the stock caps in place an bypass them with high quality 0.1 uF caps. What do you think about this?

Any thoughts/recos?

Thanks

Systems

adam2434 wrote: »

the blue stock resistors are just run-of-the-mill carbon, 390 Ohm IIRC.

Probably 1%metal films.

- Any recos for good resistors for I/V conversion?
- I know Caddock is very good.

Yep Caddocks are excellent,Vishays are good and the Holco's are good as well.

Ouput caps:
- The stock caps are Kemet tantalum 10uF. I've read not-so-good things about tantalum caps for audio.
- Any recos for output caps?

Yeah I would deep 6 the Tants.I personally would try a film cap,like the Wima MKP4 series polyprops or the inexpensive but good Panasonic ECQ series polyesters.They should be small enough to fit?


Aswell you might look at replacing the power supply decoupling caps with Panasonic FC's or Black Gates(though I believe they are now hard to source because they are not being manufactured anymore).

adam2434

What is it that you like about film caps for output coupling?

Man, there are so many opinions on output caps - 'lytic, film, PIO, etc.

Glad you posted, by the way...been impressed by your technical expertise in other threads.

Systems

adam2434 wrote: »

What is it that you like about film caps for output coupling?

IMO I believe films to do less harm to the signal thus offering a less altered and more transparent and detailed signal transfer.By design 'lytics have higher ESR,DA,ESL so I think some of the finer details and nuances get obscured.

Man, there are so many opinions on output caps - 'lytic, film, PIO, etc.

Yes there are proponents for many brands and types.Its a personal taste thing.

Systems

adam2434 wrote: »

the stock caps are Kemet tantalum 10uF.

btw Those don't look like tantulums,they look like film's maybe polyester?

adam2434

I believe they are solid tantalum like these:
http://cgi.ebay.com/2-MS-Kemet-T212-12uF-50V-5-Solid-Tantaum-Capacitors_W0QQitemZ200308341073QQcategoryZ4662QQcmdZViewItem

Systems

Yes that looks like them.I have not seen tants packaged like that before,they usually look like coated ceramic types and polarized.

adam2434

Completed the following DAC mods earlier this week. These mods changed all the parts in the analog signal path of this simple DAC.

Caddock MK-132 IV resistors
Black Gate N 33 uF output caps
Mundorf ZN 0.1 uF bypass output caps

Got the parts from partsconnexion.com and had each set matched to 1%.

Given the delicacy of the board, some folks at Head-Fi suggested that I snip out the existing parts, leaving as much lead as possible, then solder the new parts to the old leads. That's what I did. Because the old leads were so short, my new solder effectively joined the existing solder.

This was fairly tedious and tricky work. I bent the new leads into a small "J" and lightly connected them to the existing leads before soldering. However, the space was very tight and it took a lot of finessing and lead manipulation to get the new leads to stay in the right spots. The resistors leads were especially challenging because the exposed stock leads were only about 2mm and were very thin. I used a slab of Blu Tac to hold the parts in place for soldering.

Placing the Mundorf bypass caps on top of the Black Gates took a little experimentation, but was more straightforward.

I fired the DAC up after the mods and it worked! It's been running 2 days straight now, burning in. So I feel pretty satisfied, given that this was my first mod and only the 2nd time soldering (the 1st time being practice). I feel pretty confident going into other mod projects and crossover rebuilds, many of which I feel will be a breeze compared to this DAC mod.

I haven't done any serious listening yet, so don't have any comments on sonics.

Attached a couple pics. The "after" pic didn't turn out very good, but you get the idea.

Systems

Contrats on the sucessfully completeing your first mod.Modding PC boards can be a tedious excerise.