[recca]

It depends. You have to see what values of Voltage regulators you have. If you have 6V regulators you need 150ohm resistors. 8V regulators you need 270ohm resistors. What happened is that Lite starting populating boards with 6V regulators and 270 ohm resistors which clips the DAC. It doesn't matter which regulators you have as long as you have the right value resistors across R35 and R36.

 

[Bosk]

Quote:

Originally Posted by recca /img/forum/go_quote.gif It depends. You have to see what values of Voltage regulators you have. If you have 6V regulators you need 150ohm resistors. 8V regulators you need 270ohm resistors. What happened is that Lite starting populating boards with 6V regulators and 270 ohm resistors which clips the DAC. It doesn't matter which regulators you have as long as you have the right value resistors across R35 and R36.

Cheers recca, any ideas how I go about finding out weather my DAC runs at 6V or 8V please?

And if it runs at 6V, should I run it at 8V instead?

 

[recca]

You can measure the output of the vregs but i'm not sure exactly where. I would highly suggest reading the thread I linked two posts above. It is filled with valuable information. I got all of my info from that thread.

 

[recca]

This is another article with the information. They cite 160ohm resistors in this article which I believe will work and may even be preferred.

LiTe Dac Ah – Revisited.

 

[Bosk]

Recca you're a legend mate.

I swapped the resistors, fiddled with the trim pot and... IT WORKS!

I'm so relieved, had a horrifying feeling that I'd killed the DAC. Anyway THANKS AGAIN for your advice, you saved me!!!!


Funnily enough my DAC isn't running at 8v or even 6v, it's running at 5v! All three of the VREGS say "LM7805CT" which I guess is what accounts for this - very surprising indeed.
Down the track I'm definately going to heatsink the DAC chips and then replace teh LM7805CTs with LM7808's (do I replace all three?) and run this thing at 8v as it was intended.

While I'm at it I also plan on replacing the 2200uf and 220uf electrolytics in the power supply, and replacing all the resistors with quality audiophile versions.


How about you? Do you have any other mods planned for yours or are you happy with where it's at right now?

 

[recca]

Make sure you only swap U11 and U16. Those are the 2 regulators that are supposed to be 8V. U10 is supposed to be 5V.

I'm thinking about doing more to the power supply but it works now and sounds good so there's not a hugely compelling reason yet. I'm also thinking of changing the RCA input for a BNC but I'm not sure yet. What I am planning on doing is running it through RMAA to get the freq response and distortion figures to see how its running.

Glad things worked out for you. Pretty satisfying when you make the mods yourself and getting up and running isn't it.

 

[recca]

And now I just ordered a bunch of Rubycon's for the power supply. I guess its more fun to mod when others are doing the same.

How are you liking the dac so far? What's the rest of your systems?

 

[Bosk]

Dammit. I just typed out a huge post and for some reason the forum ate it.

I'll have to reply again later today as I'm about to head out now.

 

[Bosk]

You're absolutely right, DIY is hugely satisfying.

I only wish I'd forced myself to get started in DIY years ago. I've been contemplating it for ages, but having to learn all the electronics theory has always put me off. (I have an aversion to maths)
No question though, DIY is a huge, huge cost saver.

Right now my system is FLAC/foobar, from my chaintech AV-710 card via toslink into the DAC-AH, an Indeed Audio t-amp (a cheap eBay Trends knockoff), and Fostex FE126e based bookshelves, which are a sort of semi BLH design.
I've owned more expensive headphone & speaker rigs in the past (always CD based) but this one is the most satisfying, maybe because DIY is so much fun, and not having to swap CDs is sooooooo nice.


What about you? What are you future plans for your rig?
Also, where are you buying those Rubycons from if I might ask? I'm planning on replacing all the electrolytics in my DAC and was thinking of buying from parts connexion, but unfortunately all the have that's suitable are black gate standard caps which aren't the famous N class caps. They're still pretty expensive though.

Cheers for the advice on the regulators, I'm definately going to heatsink the DAC chips, replace those two regulators and run it at 8V - probably when I replace the electrolytic power supply caps as it will be easier to get in there will all the caps removed.
I'm also going to replace R35 and R36 was better quality 270 resistors, I was thinking Takman carbon films which seem nice and aren't too pricey.
Do you reckon there would be any sonic benefit to replacing the 24 reistors immediately to the left of the DAC chips with better ones? That's also crossed my mind.

 

[Bosk]

Thought I would make this a seperate post to keep things tidy.

Just wanted to let you know that last night I performed my biggest mod on the DAC yet!

I took my Indeed t-amp and uncased it, removed all the connectors, and mounted it inside the DAC-AH case in the space the r-core tranny used to occupy!
I then soldered the cheap polystyrene bypass caps (still waiting for Obbligatos to arrive) directly to the input caps of the Indeed amp, bypassing the Indeed's cheap volume pot as I'll use the PC to control gain.

I then removed the RCA's and the OPT/COA switch from the back of the DAC-AH, drilled an extra hole and used these holes to mount the speaker binding posts, which I wired direct to the t-amps speaker otuputs.

It's not a perfect mod as I still need to find out which points to wire the polystyrene caps to on the t-amp so that I can completely bypass the t-amp's input caps. I could've guessed, but I played it safe to start out with just to make sure it worked.

It's probably a little hard to visualize what I've done, but I'll post pics when I'm done modding the DAC-AH, and t-amp.

Sound quality has really gone through the roof with this mod. There must've either been a problem with the way I soldered the caps to the RCA's in the DAC-AH earlier, or the t-amp's pot was degrading the sound enormously, because the difference really is night and day - I'm not joking!

Even more amazing is that whereas after doing the bypass mod I would need to have the pot set to around 12 oclock to get decent volume, now I have it set to about 5% of maximum in my sound card's volume control and the sound is even louder, if anything.

So I'm extremely pleased with how this is going, but there are many more mods to come!

 

[recca]

Sounds like you're really getting into this. I can imagine exactly what you did because I have my output caps in the exact same place your amp is. Before I had the CI Audio VPC 3 I used a volume pot directly after the output caps and used that to control volume. Using the PC to control volume is not ideal because it uses decimation which lowers resolution. Although realistically probably not enough to matter. If you can, try a good quality pot after the output caps and before your amp. That definitely saves on the cost and hassle of IC's.

I got my ruby's from Reference Audio Mods, cd player mods,audio mods, audio modifications

 

[Bosk]

Quote:

Originally Posted by recca /img/forum/go_quote.gif Sounds like you're really getting into this.

What gave you that idea?

Quote:

Originally Posted by recca /img/forum/go_quote.gif I can imagine exactly what you did because I have my output caps in the exact same place your amp is. Before I had the CI Audio VPC 3 I used a volume pot directly after the output caps and used that to control volume. Using the PC to control volume is not ideal because it uses decimation which lowers resolution. Although realistically probably not enough to matter. If you can, try a good quality pot after the output caps and before your amp. That definitely saves on the cost and hassle of IC's.

You may well be correct, but I'm under the impression that any volume control (even a stepped attenuator) will also degrade the sound quality.. so the best volume pot is no volume pot right?

Quote:

Originally Posted by recca /img/forum/go_quote.gif I got my ruby's from Reference Audio Mods, cd player mods,audio mods, audio modifications

Cheers! I'm still not sure which brand of electrolytics to go for which is why I posted a thread here asking for opinons on which brand is best. I'll definately keep Rubycons in mind though, cheers.

 

[Bosk]

My Obbligatos arrived today and I whacked them in, replacing the cheap no-name blue poly coupling caps in the t-amp.

Wow! Huge improvement in detail, soundstage, imaging, tone, and overall listening pleasure.

But as usual I'm never satisfied.

Given how much of a difference these have made I'm thinking of buying some Mundorf silver oil caps which I've read very good things about - problem is the price. To buy 2x2.2uf caps would cost me around AU$200 which is too rich for my blood.
If I could use 2x.47uf caps instead that would lower the price to around AU$100 which is far more reasonable.


So my question for you recca is do you have any idea what change I would need to make in the DAC-AH circuit in order to replace the 2.2uf caps with .47uf caps?
I'm guessing I'd need to change the values of resistors somewhere?
Cheers mate.

Incidentally, what are those beeswax coupling caps of yours like? They're priced similarly to the Mundorfs but I've read both good & bad reviews of them, whereas Auricaps/Mundors/Vcaps tend to be pretty much universally praised.

 

[recca]

I'm not really sure how to set it up to use the .47uF caps.

The caps I use are the Jupiter Beeswax caps. Pricewise, they aren't as bad as the mundorfs as far as I can tell. I got my from Michael Percy Audio but I believe that parts connexion have them as well. I think they are great but I don't have a direct comparison since I used them first.

Here are a couple reviews:

jupiter beeswax capacitors review
ecp.cc

They have them on sale at parts connexion right now:

http://www.partsconnexion.com/catalo...itorsFilm.html

 

[Bosk]

Sweet! I just finished modding the DAC to run at 8v. Hard to detect any difference in sound (it sounded pretty damn good before!) but its nice knowing it's running like it's supposed to.

Now to replace all the resistors and power caps next week hopefully....