Chameleon DAC listening and modifications

[qusp]

ahh ok well it will be the 180R I was just going by what we do in the valab and what I have done in any passive I/V set up in any of my dacs. the I/V are usually the last set of resistors to ground before the output, I would assume your 47K are not standard and just something you put there to tune for your amp in particular?? at a glance I only saw the one set, 47K is far too large for I/V. the 340R in the valab are the I/V, in any dac i've ever built the aim is to keep the output impedance as low as possible, so it didnt even cross my mind there would be another set just to make it larger.

 

[marcelnl]

Just follow the I/V resistor it'll be connected between pin 8 of the TDA 1543 and the high roll off filter, disconnect the stuff between the I/V resistor and the output capacitor.

In v 2.5 there is a 1mH in line then a 5600pF cap going to ground and then a bead (unspecified value) in line and then the coupling cap, after that a 47 k Resistor to ground.

The 180 Ohm (brown grey brown) resistors should be connected just after the DACs, so on the left circuit board right before the connection of the coupling cap, can't see the colors on the resistors or the printed circuit board underside to identify ....


If the effect is anything similar to cutting out the noise filter in my old Marantz once made it'll be huge(similar to cutting out the de-emphasis filter).

 

[marcelnl]

Quote:

Originally Posted by Bill Allen /img/forum/go_quote.gif OK one last thought on Spdif simplicity. How about you completely remove the RCA jack from the back of the Chameleon, cut the end off your digital cable, feed it though the hole and solder directly to pin 2 of the pulse transformer, shield/ground wires to pin 1. Yes, you now have a "dangler" digital cable but I bet you it would sound even better.

I tried that approach once after having listened to the sonic effects of just one solder joint..... and though it had sonical merits the drawbacks were indeed that it only works well when you integrate the DAC in the transport, else the connections just is too finicky (for my taste) and this setup robs you of the chance to tinker with other digital cables

On the long run I may end up with using lossless files without a CD transport, and a digital cable would be unavoidable.

If it however turns out that a CD transport outperforms the digital route I might as well just build my own transport + DAC combo (something like this for a transport looks nice VAU1254 CD-PRO2M) and putting the two together in one case would be doable (and preferable as it would be possible to use a short cable using I2S).
Stick the PSUs for both in a separate box (or the combo would be huge indeed) and be done.

 

[PatOMalley]

marcelnl, right. I took a look at Bill's pictures and saw where he put his Caddock's then knew. I may lift everything from the board like you suggest and looks like Bill did.

 

[PatOMalley]

that transformer power swap heats up the case a lot. So my rubber feet are not good enough. What I did was to drill six large holes in the front top chassis and one large in the back top chassis for some venting with draw.

then added three aluminum cones to the bottom give airspace and act as heatsinks. The feet settle into those little feet rests, whatever they are called, that protect surfaces from the spikes.

Chassis work is not my forte and this looks a little hey hey but very effective.

 

[Wood]

I reduced the voltage to 7.66v to the chips from a high of 7.87v today, I found the sound to be too warm and hazy, with some loss of depth on the higher voltage. 7.66 is more of a balance for me. So nice to have the option to control the SQ this way. Might even try going below the standard 7.55v!!

I have not done the yellow wire mod simply because this is a Valab and there should be suffcient current for 8 tda's. I will do the mod and try different voltages with the Chameleon when it arrives. Already got a nice heatsink for the base of the DC-30, and I might upgrade those resistors to 1W for peace of mind, as I don't know what the effect of the Yellow wire mod will be with 220 AC.

Happy twiddling!

 

[hifi2001]

So in the course of last 15 hours or so I see there was a flurry of activities on this post and too bad I missed all that excitment... I just got caught up now. Here is my comment on some fo things that was asked.

- After A/B DC-30W blue vs yellow wire mod the best way to describe it is like going from a computer power cord to a decent power cord. I was listening to one of my favourite Canadian jazz singer Diana Panton (DianaPanton.com | Canada's Rising Jazz Star) with the yellow wire mod her voice went from a young adult to a mature woman - I still can't believe it.... I will most likely drill some small holes to both sides of the chassis and raise the legs. Another thing that is making me wonder is to use better DC cable between DC-30 and Chameleon since we have proven that blue wire was current starving the DAC.

- Bill, the 0.1uF cap you refered to on the back of Pat's clock board, I believe it will be there on all the clock boards Michael is shipping. It is basically a coupling cap between the output of transformer and the clock chip, I think Michael used it to cancel any start-up noise. Michael actually have similar cap in the pre-production boards you and I have but it is on the wrong side of the transformer.

- I/V resistor is that blue resistor Bill mentioned, however, when I pulled my off circuit I found them to measure 160R... Accordig to Michael the ideal value is 175R which is hard to find. I have 172.5R after manually matching two 330R in parallel

- Bill/Pat, both of you have removed that 0.01uF slver mica from the ouput. I will be curious to hear what you think if you added a similar value teflon cap there instead. As I mentioned, I currently have Vishay MKP there and found th sound uplifting...

- Pat, you mentioned looking for better transport? Can you share what are you looking at? I on the other hand, am going down the path of looking for a decent DVD/CDP player as transport new/old ...

 

[marcelnl]

Quote:

Originally Posted by Wood /img/forum/go_quote.gif I reduced the voltage to 7.66v to the chips from a high of 7.87v today, I found the sound to be too warm and hazy, with some loss of depth on the higher voltage. 7.66 is more of a balance for me. So nice to have the option to control the SQ this way. Might even try going below the standard 7.55v!! I have not done the yellow wire mod simply because this is a Valab and there should be suffcient current for 8 tda's. I will do the mod and try different voltages with the Chameleon when it arrives. Already got a nice heatsink for the base of the DC-30, and I might upgrade those resistors to 1W for peace of mind, as I don't know what the effect of the Yellow wire mod will be with 220 AC. Happy twiddling!

220 V should not affect the secondary voltage, so if you disconnect the transformer and you measure the unloaded yellow wire and you measure some 14-16 V Ac all should be well (the primary wire of the transformer is paralleled for 110V and connected in series for 230V). The ratio between the two should be the same for the blue wire as for the yellow wire so the difference should not matter too much.

Anyway in my experience there is no such thing as too many A in a PSU, same as with replacing cubic inches in an engine, nothing substitutes cubic inches as well as more cubic inches

@Hifi; it is not the color of the wire but the current the secondary winding on the transformer is capable of that makes the difference here, a better quality cord between the PSU and the DAC but will make less of a difference than the wire swap from 9V Ac to 12 Vac on the yellow wire.

looking for a better CD transport I'd look no further than a CDM2 Pro. There should be a good replacement that can be found in a ghetto blaster and I'll report once I have the make and model of that transport.

 

[Wood]

Hey marcelnl, thanks a lot there, youve given me the confidence to go ahead now and try that. From what you say, please correct me if I'm wrong here, that the yellow wire is not about higher voltage, its about the ability to deliver more current. So even keeping the voltage to the chips at stock level might deliver an improvement in SQ?

Apparantly those resistors are rated at only .24w do you think its necessary to swap them out?

 

[hifi2001]

Quote:

Originally Posted by Wood /img/forum/go_quote.gif Apparantly those resistors are rated at only .24w do you think its necessary to swap them out?

Wood, I wouldn't replace those 0.25W resistors for something higher... remember that we are in uncharttered territory here... thiink of those resistors as a safety fuse... this is something I've learned while building vaccumm tube amps

 

[Wood]

hifi2001, now I'm impressed, thats alternative thinking for you!!!

 

[marcelnl]

well I'd change them, as the voltage regulator can easily handle the amount of current needed....it is just that the 12V AC wire can deliver more current.
Personally I'd change the .25W resistor as I'd hate to see the PSU fail for something as stupid as a pull up resistor.
I'd rather worry about the excess power the voltage reg needs to dissipate and thus of its heatsink, looking up the specs should ease your mind as I recall that it is fine up until 18V AC.

A cathode resistor in a tube amps is something very different, hope you do' nt use voltage reg IC's in a tube amp anyway.

 

[hifi2001]

Quote:

Originally Posted by marcelnl /img/forum/go_quote.gif well I'd change them, as the voltage regulator can easily handle the amount of current needed....it is just that the 12V AC wire can deliver more current.

marcelnl, you do have a point... Since I haven't had time to fully understand the PSU circuit I'll just seat tight for now...

On a different note, your previous link for CDP-PRO2 transport, have you build one yet? I was thinking about such a project, and was looking for a starting point, etc

 

[PatOMalley]

Ah, well. 180 is not far off. And I can apply more heat than usual to help the R drift ... just joking.

Instead of us putting caps back in the filter slot why don't you move your Vishay in bypass duty at output? I bet you will notice a big difference.

For transport I was looking to VALAB who had a smart looking one a while ago. They no longer have it but I keep looking.

Quote:

Originally Posted by hifi2001 /img/forum/go_quote.gif - I/V resistor is that blue resistor Bill mentioned, however, when I pulled my off circuit I found them to measure 160R... According to Michael the ideal value is 175R which is hard to find. I have 172.5R after manually matching two 330R in parallel - Bill/Pat, both of you have removed that 0.01uF sliver mica from the output. I will be curious to hear what you think if you added a similar value teflon cap there instead. As I mentioned, I currently have Vishay MKP there and found th sound uplifting... - Pat, you mentioned looking for better transport? Can you share what are you looking at? I on the other hand, am going down the path of looking for a decent DVD/CDP player as transport new/old ...

 

[marcelnl]

Quote:

Originally Posted by hifi2001 /img/forum/go_quote.gif marcelnl, you do have a point... Since I haven't had time to fully understand the PSU circuit I'll just seat tight for now... On a different note, your previous link for CDP-PRO2 transport, have you build one yet? I was thinking about such a project, and was looking for a starting point, etc

nope haven't built one yet, probably will first get my hands on an old Philips CD 960 that I'll persuade into becoming a top loader.