Chameleon DAC listening and modifications

[Bill Allen]

I am an advocate of everything in the Spdif input circuit path does nothing but add jitter, and yes that's everything, right down to a RCA jack.

However I hate to say this but if are going to be using the Upsampling/Re-Clocking (USR) card, the gains from this sort of thing will be minimal. To confirm this I ran the Pace Car into the Spdif input with USR card installed and I hear very little difference compared to the USB input. This means the USR card is creating a common denominator dragging the Pace Car's superior jitter reduction down to its level. Same would be true with any other Spdif input improvements.

Ok where does that leave us, well if you pull the USR card then all bets are back on again. Here I can clearly "hear" every little thing I do to improve the Spdif path. On that note I had Steve Nugent look at the Chameleon wiring diagram. This is "his" recommendations.

Bill - I prefer to wire the RCA directly to the primary, no grounding. Float it. Then put the 75 ohm resistor on the secondary and ground one side of the secondary. Secondary feeds the receiver chip through a .1uFd cap.

STeve N.

Thanks Steve! Interesting "floating" the + Spdif input. OK if you do the direct wire of the Spdif + input all you need to do is lift the Spdif RCA jack ground wire. Pat's picture on page 4 clearly shows the direct wire mod and existing green .1uf cap to Wolfson receiver chip. The only question is; what side of the Pulse transformer is that 75 ohm surface mount resistor. The wiring diagram shows it on the input side. However if its actually on the secondary like Krisno suggests then Nugents Spdif "Float" Mod is already complete.

Humm ... anyone care to check this out, I am out of town until Monday.

 

[marcelnl]

now that is interesting, I played with that option for the Valab....where the 75 Ohm is in the signal path as for the 0.1 uf cap.

 

[MikeW]

I emailed Michael and asked him about the SNR of the new Chameleon, and he confirmed that it was indeed a bit noisier. And related it to the amount of dac chips being used. Is there an easy way to disable x amount of dac chips in Chameleon? Like if you wanted experiment with 12 instead of 16? I played with the USB input on Chameleon a bit, and was rather impressed straight away. It may have the edge on SPDIF in my setup, but I have pretty crappy spdif transport to begin with.

So I wonder where the magical performance mark is when relating the USR Card to Transport. How high end of a transport do you need before the USR becomes a bottleneck. It's pretty sweet that the option is totally user selectable though, as many won't have a high end transport, and stand alot to gain from the USR. Such as myself

Equally I guess most of the SPDIF mods will be useless unless you fall into the catagory of owning a high end transport.

this new information is rather contradictory to my above observations of USB sounding slightly better then SPDIF however. More listening impressions and burn in will be needed.

Edit: I opened my chameleon up for a quick look. I noticed on my Digital board, near the WM8805 there's a small green 01 UF capacitor, the left leg of it is connected to a solder pad, near the 75ohm resistor, that says "bypass" above it, the right leg however, is not connected to anything, that seems odd. Can someone check their's ?

 

[marcelnl]

I think that you'll be able to lower the noise floor a bit by using better caps and bypasses throughout the device!

Disabling 4 Dac s should be possible, but you should remember to change the value of the I/V resistor too.

There will be an optimum for the amount of DACs acc. to the law of diminishing returns; at some point the additional noise created will most likely outweigh the sonical merits of the additional resolution.

 

[MikeW]

the little green capacitor looks like it should be attached to a leg of the pulse transformer, but im afraid to attach it without confirmation.

Edit: nevermind, my green cap looks exactly like the one in Pat's "keeping up with the jones" post on page 4, looks like that's the way it's supposed to be, that's so weird to have only half of it hooked up.

Edit: Just to be clear, a question on Pat's "Direct Wire Mod" doing this mod removes the 001 DC cap does it not? So it would not be safe if your transport puts out DC? Something to remember after doing that you won't protected from dc in spdif.

It also looks like Rhodes54's Post 104 is at odds with Bill's 121 post. Wonder which one of you is right?

 

[rhodes54]

Quote:

Originally Posted by MikeW /img/forum/go_quote.gif the little green capacitor looks like it should be attached to a leg of the pulse transformer, but im afraid to attach it without confirmation. Edit: nevermind, my green cap looks exactly like the one in Pat's "keeping up with the jones" post on page 4, looks like that's the way it's supposed to be, that's so weird to have only half of it hooked up. Edit: Just to be clear, a question on Pat's "Direct Wire Mod" doing this mod removes the 001 DC cap does it not? So it would not be safe if your transport puts out DC? Something to remember after doing that you won't protected from dc in spdif. It also looks like Rhodes54's Post 104 is at odds with Bill's 121 post. Wonder which one of you is right?

The main purpose is not to block DC but to create a crossover point at the SPDIF input. This way you filter out noise and other pollution in the SPDIF signal which 'can' result in a cleaner signal. The lower the chosen value of the input cap, the higher the crossover point. As said before the value of 0,01uF is chosen to low and should be 0,1uF to keep the crossover point below 100Khz (which is more than enough). Besides the fact that it sounds better there's also a technical reason to choose this value but I can't recall what he exactly told me.

Of course different people have different views and therefore no one's right.
I do trust the guys at Tentlabs/Grimm Audio because of the their service record when it comes to jitter elimination and digital audio. Just listen to the Grimm audio products (and their philosophy behind it) and you know exactly why I'm very enthousiastic about them. That's the main reason for me to follow their advices.
One of the Grimm guys, Peter van Willenswaard, has been the first in the world to write about jitter.

Do whatever you like to do with the info I post here. I won't claim that I have the right solution, it's just one of the options.

By the way: As Chameleon owners we can ask Teradak for the schematics of the Chameleon. I got them a few days ago and it contains a lot of answers to questions posted here.

 

[hifi2001]

Quote:

Originally Posted by MikeW /img/forum/go_quote.gif the little green capacitor looks like it should be attached to a leg of the pulse transformer, but im afraid to attach it without confirmation. Edit: nevermind, my green cap looks exactly like the one in Pat's "keeping up with the jones" post on page 4, looks like that's the way it's supposed to be, that's so weird to have only half of it hooked up. Edit: Just to be clear, a question on Pat's "Direct Wire Mod" doing this mod removes the 001 DC cap does it not? So it would not be safe if your transport puts out DC? Something to remember after doing that you won't protected from dc in spdif. It also looks like Rhodes54's Post 104 is at odds with Bill's 121 post. Wonder which one of you is right?

That green cap is a coupling cap between pin 4 of input transformer and pin 3 (RX0) of WM8805. There is a fine trace underneath it. I would leave it if I were you. the trace is very small and is no fun if it comes loose...

 

[marcelnl]

even a small trace can be replaced by a wire....

 

[PatOMalley]

Quote:

Originally Posted by marcelnl /img/forum/go_quote.gif even a small trace can be replaced by a wire....

And sometimes to great effect.

 

[Bill Allen]

Ok to sum up this page for those less technically inclined, the main choice is to leave the USR card in ... or out.

1. If you use the USB input leaving in the USR is a must! (I was just listening to some native 96/24 music files and it sounded amazing).

2. If your transport has no chance at low jitter then simply leave the USR card in and be happy knowing the USR card does a fine job at jitter reduction.

3. If you have a great transport, by all means do the Spdif direct input mod. To pre-filter or not to pre-filter is your question to answer. To float or not to float is also your call. (Rhodes is correct in saying there is no right or wrong, I will play with both options as time permits).

As far as noise go's I hear no audible difference comparing the modded Chameleon to the Valab DAC. I have to stick my ear in my 100DB speakers to hear any noise. If you use headphones you may be more sensitive to this issue.

If anyone wants to play with less DAC chips it just a matter of removing them. No special considerations besides adjusting the I/V value for max output volume. With 8 chips I used 400 ohm, with 16 chips I use 200 ohm. Do your own math for 12 chips.

By the way I have no issue with clipping with these value with both my Mac Mini USB or Spdif input. However I have found some computer USB outputs can drive the DAC into clipping. If this happens you have a crappy computer and for gods sakes just turn the digital volume down a little and quit whining. (Damn did I just say that out loud).

Peace!

 

[Pricklely Peete]

You guys should ditch the RCA SPDIF jacks and cables for BNC and use Illumati 75 ohm coax cable for the hook up wire (in your transport and DAC).

Made a big dif with my gear (Audio-gd CD7 and Reference 1 DAC).

Peete.

 

[MikeW]

sounds like my best bet would be to just replace the Russian spdif input cap with a 01 uf film cap. Any suggestions? I was thinking of maybe Sonicap Gen I's. I was looking at mod parts and the price starts to spiral out of control rather quickly.

16 BG 47uf's @ 5.25 ea = 84$
Mundorf Silver/oil x2 70 ea =140
Texas Resistors, these are like 20$ ?
Quality RCA's ~30$

300 bucks easy. I wonder how the Wima's would sound Bypassed by an 01 uf sonicap platinum.

It would be interesting to experiment with different caps in place of those Silver Mica's, instead of removing them altogether. Are the additional holes on the Chameleon output cap section just more holes for output caps of different sizes? Could you use these holes for bypass caps?

marcelnl : i'd love to hear your suggestions for exactly where to put the bypass caps to improve SNR. It's my one complaint about this dac so far. I do use headphones, and it's more noticeable. I can imagine a speaker setup would be slightly less annoying as the drivers are not a inch from you ears.

 

[Pricklely Peete]

Just by pass the K40 with a T1 of low value (like 820pf). The K40 is better than NOS Vit Q but it takes at least 400 hours to settle down, until it does it's rolled off in the highs and the bass comes and goes. That K40 cap given enough burn in time combined with the Teflon is better than most boutique caps. Don't waste piles of money on fancy caps unless the DAC you are working on is worth 10X the cost of the caps your planning on using. The biggest giant killer cap combo of all is the Russsian K75 series bypassed with Teflon T-3's. I kid you not...look in the DIY forum for the huge cap thread.

Peete.

 

[Bill Allen]

Guys - lets try not to choke up this Chameleon forum with loose banter & the sound of coupling caps and bypass values. I counted over 50 pages of such nonsense on the the previous Valab forum. Let not repeat that exercise!

Feel free to PM people for specific individual questions, and lets focus on responding with well thought out Listening & Modifications "results" as the name of this thread suggests.

Quality comments ... not Quantity!

I not trying to police this thread but once it gets too large it loses its focus. If you don't believe me, just try an go back and re-read the previous 2 Valab threads. No Thank You!

 

[Pricklely Peete]

Talking about caps isn't relevant ? That's all you guys have been going on about practically speaking ...all I was trying to point out was the lowly K40 is better than the billing it's receiving in this thread. I'm all for trying anything and everything but when the caps cost more than the gear being worked on it makes little economic sense (at least it does for me), rather the trick is to get that same performance (as the uber expensive stuff) from the oddball parts that no one gives a second thought to, but should. I don't mean to dampen anyone's curiosity or to use what I say as gospel, I guess I'm just a cheap Scot that needs to write his posts with a little more diplomatic finesse.


Peete.