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Chameleon DAC listening and modifications - Page 27

post #391 of 1144
Got some new pics for you guys. I reinstalled the TX resisters today, this time making sure to get the leads as short as possible. I also found a pretty cool way to mount the Wima FRM. This works out quite neatly. It also gives a better connection. I think this FRM mod might be a keeper afterall. I took it out today for a listen and it seemed like I lost alot of sparkle and maybe a bit of bass slam. I wonder if there are better capacitor options to use here, like a high UF electro, or if sticking with fast clean film is the way to go... anyways here's the pics, see what you guys think.
post #392 of 1144
Looks good Mike

post #393 of 1144
Thread Starter 
Originally Posted by MikeW View Post
anyways here's the pics, see what you guys think.
Better than the mish mash wire nest I have. Nice clean job.
post #394 of 1144
this FRM mod is really interesting, can someone that knows more about this then me explain exactly what it is doing? It's acting as a "Current reservoir" yes, but how can it effect the sound so much, there must be more to it then that. Is it also filtering the power supply to the dac board?

I think it would be interesting to try different caps here. Anyone got suggestions?
post #395 of 1144


Originally Posted by MikeW View Post
this FRM mod is really interesting, can someone that knows more about this then me explain exactly what it is doing? It's acting as a "Current reservoir" yes, but how can it effect the sound so much, there must be more to it then that. Is it also filtering the power supply to the dac board?

I think it would be interesting to try different caps here. Anyone got suggestions?
Nope, there is NOT more to it than that. It can affect the sound so much because the power supply as designed maintains a steady voltage (the voltage will drop after the current demand makes it so there is a delay) as much as possible. The load is fairly current heavy vs. the digital side which draws a relatively steady voltage and current. The advantage is that the current reservoir is right where it is needed, not 18" of cable away. This does a couple of things; it gives the chips the instantaneous current when they ask for it and it lets the regulator at the power supply have a little easier job as it does not try to mimic the needs of the chips quite as closely thereby reducing the tendency of the regulator to oscillate and the diodes to ring. Think of it as though it was your power amp clipping. You will lose bass and your treble will start to sound lousy. Same thing really.
Having the power supply in a separate case is a very good idea but you can now see that it is not without compromises. Engineering in a nutshell. NO free lunch but you have the solution that is easy and cheap to implement. This is where the DIY thing can be fun as it affords an opportunity to learn the compromises that a company must make in designing and building any product. Also, everyone gets to hear the changes for themselves. No marketing BS or some reviewers' opinion to rely on.
Second question, yes it would be filtering the power supply to the board but I measured no A/C so it is not a problem and noise like that would best be handled before the regulator (which it is). Everyone should understand that most chips have a pretty good power supply rejection factor (or rate) and their circuit usually has yet more capacitance to pass A/C to ground. The DC-30 is really a nicely designed unit that will take a lot to surpass without building one from scratch. Mostly, it should be left alone. Unless one is VERY familiar with building them and want to put in a bunch of time building one that matches the needs of THIS DAC specifically you will be treading into a morass. That is why people like Paul Hynes build them and make money doing so. Even Paul can be surprised when he builds them and finds significant differences between the sound of his series and shunt regulators. You can do a search to find this on the net.
Of course, that does not mean improvements cannot be made but the costs may not be borne out. Again, remember that you are helping the power supply out by having the BK caps on the chips (again, think location) and the cap reservoir. This is essentially modifying the power supply and the money IMO and IME is better spent there.
Regarding the type of caps and their value. As I have previously stated, IME film caps simply sound better even in a power supply. That being said, having electrolytics before the regulators is certainly a good choice due to the low cost and very high capacitance and the power supply rejection of the regulator chips. Very low levels of A/C at this point in digital circuits are probably more paramount (along with very steady voltages) than they might be in other circuits. This goes back to designing a power supply for the unit in question as "rules" can change somewhat depending on the demands placed on the PS. I use film type caps in my tube gear and they smoke even BlackGates head to head.
Since most guys now have a nice pair of film caps to use (except Pat, what the heck where you thinking when you chucked your WIMA's???) I would think that they will be more than sufficient as reservoir caps. Going to more exotic stuff here is probably wasting money unless you have some really nice ones sitting around like I did. No, I will not take mine out and install the WIMA's to let you know the difference. Sorry, I don't do backwards.
On another note, I ordered some of the Texas Instruments resistors today and will post my comparisons to the Caddock's that I am currently running when they arrive in a couple of weeks.

post #396 of 1144
Thread Starter 

all bets are off

I guess I'm not done, tony.

Those DACs need the caps on each. I can still bypass the BG with a small Vishay cap, and bring the power rail right from the connector straight to the DAC board getting off the trace.
post #397 of 1144
So Driguy, you think the smaller 20UF capacitance of the film caps is still better then a high UF electro? like 500 UF or something in that area? I wonder if this FRM negates or lessons the need for the yellow wire mod.

I tried floating my input ground to the 2nd leg of the pulse transformer today. It seemed to work fine. However it would randomly send my headphone amp into "Protect". I had to reverse it. Strange...

What voltage are you guys runing at anyway on the Dac chips? Mine like to start making very slight buzz noises when I raise the voltage past 7.55 It's so slight that I ignore it, can only hear it with the amp cranked to deafening levels.

edit: amp just clicked protect again, looks like it's un-related to the float ground mod.
post #398 of 1144

Bets off, there goes my retirement fund

Pat I was looking at those AN digital transformers, any ideas how to wire them up as they have 2 leads instead of 4 connection points of the pulse?

Mike, it may be the psu running out of steam at higher voltage, the reason Bill did the yellow wire mod. After I reversed the yellow wire mod I notice the bass was softer, so I reduced the voltage to 7v to the chips, this seemed to tighten the bass a little.
post #399 of 1144
does the AN have two in total? in that case it would be an auto transformer which is connected by using a common ground between primary and secondary. I would expect it has only two leads in primary and in the secondary winding, you should get a diagram with it indicating what the primary and secondary 'hot' pins are.

20uF film is a helluva lot better than a couple of 100 uF electrolytic, personally I am no big fan of the BG sound.

Pat: I'd use somethying decent and discrete there, in my experience the good WIMAs (MKS)do a great job there at laughable price.....getting them in there is the hard part. I am with Tony on this!
post #400 of 1144
Thread Starter 

the AN have four leads

I think the leads are identified as hot and ground on the covering.
I owul leave all leads the same lenght, not cutting them short, paste the coil to the board and have nice long leads to remove the board with.

The BG sound is dense at startup but opens out after a couple few hundred hours. But you gotta leave the machine on all the time and that is what i do with this DAC. Never goes off. The BGs have to reform at each power cycle. Not for use with tubes.

But I will get me some Wimas anyway.
post #401 of 1144

Head or tail?

Here is a pic and things, duh I'm confounded!!

Audio Note
post #402 of 1144
Wow wood, you are runing at 7v eh? You did not notice any negative effects of this? Like a thinner sound? That is interesting. I thought they where supposed to run at 7.5 volts min. I'd say run them as low a voltage as they sound good at, it can only help heat/stress. chips run cooler, psu runs cooler etc.

I found the problem with my headphone amp, I had been rolling OP-AMPS and got a bad chip. Had nothing to do with dac.

Edit: forgot to mention my fun experience with the pulse transformer .1 cap recently. I was taking the digital board out and I nudged my wima .1 a little to hard and it broke loose. I had lost the whole trace and everything. That was fun! I had to use an xacto knife and scrape and dig the trace back out, and then try to get solder to stick to it. Real pain in the ass, but I got it done.

off topic: Does anyone have experience with different OPAMPS? Im thinking of trying a pair of AD797BRZ on a browndog adapter.
post #403 of 1144
Thread Starter 
Originally Posted by Wood View Post
Here is a pic and things, duh I'm confounded!!

Audio Note
They are two sets of twisted leads, two leads twisted together.

Leads = +/- twisted input to coil +/- twisted output

They look nice don't they?

If you look close you can see one of the wires with a silver marking designating it as positive.
post #404 of 1144

Yes they certainly do!

Thanks Pat, bin looking everywhere for those extra wires, and they were there all the time. Might give them a try, but I have 2 pulse to change I think, there is one in my external async device as well as the Chameleon so might be pricey. Now the BGs are past the worse, I wonder how much more can be got from this dac?

Their claim 'compare the quality and be prepared to be shocked, there are good reasons why our Level One and higher Level 1 x oversampling™ d-to-a converters have the reputation they have and the digital interface transformers have a great deal to do with this'

But I guess they would say something like that..
post #405 of 1144
I'm no fan of Opamps, too much negative feedback etc....fabulous specs but crappy sound, I'd suggest a good ole tube any day but that is a matter of taste.

Great that you islotaed the problem though! From the look of those toroids you could make them yourself, find some high grade core and good wire and you're in business venturing out into a yet unexplored digital HighEnd pasture :-)
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