[Bosk]

Hey recca I have a quick question for you-

Are the 24x Resistors next to the DAC chips 100ohm? That's the number I came up with by studying the color bands but there isn't a value assigned to them on the schematic so I can't be sure.

I'm planning on replacing them all with Kiwame carbon film resistors, which apparently sound more natural than metal films.

 

[recca]

I really don't know. I'm very curious to hear what your results are though because I thought about doing the same.

 

[Bosk]

Guess I will go with 100 ohm, it seems about right.

I'm going to solder in all the resistors separately from other mods I have planned - I'm very keen on knowing how much of a difference they make myself, not least because at US$1 each it's not really a cheap mod.

Oh, and I'm going to replace all the power caps with Panasonic FC or FM initially and see if I can hear any difference. If so, I might spring for some more expensive Elna Cerafine or Silmic II.

Finally, I'm also toying with the idea of buying a small roll of Mundorf supreme solder, which has 9% silver content, (!!!) and resoldering all the joints on the board with it. That would be the final mod I perform on the DAC once I'm happy with everything else.

 

[recca]

I'm glad you mentioned that upgrading the VRegs don't make a difference, saves me the trouble.

With that I have received some Rubycon ZL's and some Panasonic FM caps which I'll be rolling into the power section. Another plan is to setup a cap bank after the battery and before the power input. I believe this is the preferred setup in battery powered amps so I'm going to try it on the DAC as well. I'll report what I find.

 

[Bosk]

Quote:

Originally Posted by recca /img/forum/go_quote.gif I'm glad you mentioned that upgrading the VRegs don't make a difference, saves me the trouble. With that I have received some Rubycon ZL's and some Panasonic FM caps which I'll be rolling into the power section. Another plan is to setup a cap bank after the battery and before the power input. I believe this is the preferred setup in battery powered amps so I'm going to try it on the DAC as well. I'll report what I find.

Let me know how those caps go recca, I'm keen on knowing if you can hear a difference between brands.

The cap bank sounds like a very good idea.
I'd been thinking of implementing something similar myself but have no idea how to go about it.
If you could let me know how to build one I'd be keen on giving it a try too.
Any idea how many and what value of caps would be suited for it? I ask because I'm going to be putting in my order for Panasonic electrolytics tomorrow and I can add some extra caps to it if I know what types I'd need.

 

[recca]

I'm not 100% sure on the cap bank but I don't think you need a lot of capacitance for the dac. I'm using 3 x 2200 uF Rubycon ZL's and parallel them with a 1uF and .1uF. I'm hoping this should be enough. I'm also replacing C25 and C26 on the board with 3300uF Rubycon's. It might also be worth replacing C9 and C10 but I'm debating on that. 470uF Panasonic FM's are going into use in C27, C28 and C37.

Check this link regarding bypassing, pretty interesting read. Its a 3 part series and worth reading the whole thing.

Choosing and Using Bypass Capacitors (Part 1 of 3)

 

[Bosk]

Quote:

Originally Posted by recca /img/forum/go_quote.gif I'm not 100% sure on the cap bank but I don't think you need a lot of capacitance for the dac. I'm using 3 x 2200 uF Rubycon ZL's and parallel them with a 1uF and .1uF. I'm hoping this should be enough. I'm also replacing C25 and C26 on the board with 3300uF Rubycon's. It might also be worth replacing C9 and C10 but I'm debating on that. 470uF Panasonic FM's are going into use in C27, C28 and C37. Check this link regarding bypassing, pretty interesting read. Its a 3 part series and worth reading the whole thing. Choosing and Using Bypass Capacitors (Part 1 of 3)

Cheers recca, I'll give that link a read later tonight.

I'm really looking forward to hearing your impressions on the cap changes & cap bank.

Might be worth mentioning though that 470uf caps could be quite a squeeze in C27/28/37, you may want to check the dimensions of the electolytics you're planning to buy to make sure they'll fit in those positions.


You know, in a way I wish I had a stock DAC-AH on hand just so that when I'm done modding this one I could compare it with stock unit.
The modded version would probably tear the stock DAC-AH a new one!

 

[josep]

Quote:

Originally Posted by jsplice /img/forum/go_quote.gif This is very interesting. I actually have a Yulong DAH1 that I've wanted to convert to battery power, but I'm not sure how effective it would be, considering the power is used by not only the DAC, but a built-in headphone amp and a backlit LCD display (which may possible to disable if necessary). I suppose I could also disable the headphone amp, but not exactly sure how. I know the transformer has 2 x 15v output windings, so I'm not sure how I'd get 15 volts of DC from a battery because that doesn't seem like a standard voltage. How did you get this to work if the dac itself is designed to run on AC?

Hi,
The Yulong is a bit trickier to get converted for battery power. Good news is the analog rails are at 12, not 15V, bad news is thay are +12 and -12, thus requiring at least two batteries (12V ones). Also, you need a +5 supply for some electronics (and the front display) but this is not so problematic.
It can be done easily removing the original transformer and rectifier bridges, and looking at the board.
I had good results working a bit on the original PSU and configuration btw, look the Yulong threads around here

Regards (and Sorry for the small off topic btw)
Josep

 

[recca]

NP josep. Did you get it running on batteries?

 

[josep]

Hi,
I have done it but just 'in the lab' (with three batteries and lots of wires around a bit like Frankenstein) looking to find out if the noise I was detecting was or not transformer/rectifier related. It was, background was a lot quieter with them out of service, so I decided to start my mods.
The newer LiPo cells are a great find btw for this use, I can be able to put enough power inside the Yulong box to power it for many hours with them. But one must be VERY careful with them (specially if your house is wooden-made).

 

[Bosk]

Have you got round to doing any of those mods you mentioned on the DAC-AH yet recca?

 

[recca]

No I haven't. I hate opening it up to do one or two things so I'm planning on replacing the coaxial input to a BNC with a pulse transformer. Once I get that planned out I'll pop it open.

And honestly, it sounds so good right now that I'm not dying to change anything up.

Have your caps broken in yet?

 

[Bosk]

Quote:

Originally Posted by recca /img/forum/go_quote.gif No I haven't. I hate opening it up to do one or two things so I'm planning on replacing the coaxial input to a BNC with a pulse transformer. Once I get that planned out I'll pop it open. And honestly, it sounds so good right now that I'm not dying to change anything up. Have your caps broken in yet?

Wow, that sounds like a pretty major mod. Please let me know the results!

It's hard to know if my caps have broken in or not, I'm assuming they have. Like you I haven't done any other mods as yet but more are in the works. When I get some cash I'll be aiming to replace all the electrolytics and those two resistors with TAKMAN versions.
I'm also planning on buying a 12V power supply kit of some sort in future, along with a suitable transformer. Battery power is great, but inconvenient as both the DAC+t-amp are capable of running my 7AH SLA down from full charge in little over an evening of listening, especially now that the DAC is running at 8V. I also suspect that a well built 12V AC power supply would deliver more bass slam, impact and dynamics than the battery will, but then again I could easily be wrong.

Glad to hear you're really enjoying your DAC! Mine is going great too, but I'm ever eager for improvements if only because I'm curious about just how 'high-end' I can take this little unit.

 

[Bosk]

On a whim I just swapped the 1% metal film resistors I was using in R35 & R36 with 5% carbon film resistors, all from my local electronics store.

Huge improvement! It's hard to articulate the difference but it feels like detail, dynamics and musicality have noticably increased.

I have some TAKMAN carbon films and tantalum resistors due to arrive soon, I will update this thread when I've installed them.

 

[recca]

yeah i have the riken carbon's in as my resistors. I'm thinking of changing the power caps for each dac and bypassing them as well. sigh. will this ever stop?