Buffalo II DAC problems - Voltage sag between Placid BP and IVY

**Edit - got this problem fixed now, but initial problem reposted as requested (see post No.5)**

Sorry guys, yeah basically I was having to increase the output current a hell of a lot to overcome the voltage sag. But then with the increased ouput the heatsinks were getting really hot. I thought there must be something a miss somewhere. After checking all components pretty thoroughly, I had to rule out that the battery wasn't low on my DMM and giving false readings. Changed the battery and indeed thats what it was! I rechecked all ouput voltages and currents to set up the power supplies again - it seems to all be running and adjusting correctly now.

Apart from this small hiccup, everything else has gone great with the Buffalo build. I've put it in a temporary enclosure (AKA a K702 box) until I get round to ordering one from HiFi2000 and getting panels cut from FPE.

Now that there are some Buffalo builders watching this thread, I do have some more general questions:

1) When connecting a 4-pin XLR chassis socket to the left and right balanced outs from IVY, do you just use the + and - and leave the GND empty? Or should you do something like solder a GND from each to the body of the connector?

2) When I measure the current headroom on the placid while under load (music playing) it constantly varies +/- a few (maybe upto about 5 or so) mA. Is this normal? The current headroom from the placid BP seems to stay much more stable.

3) From the placid, I am currently powering the Buffalo-II, and toslink module. I only bought one placid (and a placid BP obviously) and a 4:1 s/pdif mux board. Can I also power the mux with the same placid as the toslink module and Buffalo? If so do I just run all three sets of wires out of the VDC out terminals?

Cheers for any input guys

Quote:

Originally Posted by qusp 

I would say no, you shouldnt power it from the same placid. you are already probably pulling about 500-550ma right? plus its of benefit to have the digital and analogue sections powered from separate power sources IME. so I would get another PSU/regulator and power the dac+toslink+MUX with one and the IV with the other

I do have another PSU, the placid BP (bipolar) which is what you need to run the IVY. My question was could I run the Buffalo, Mux and Toslink boards off the same supply? Still waiting for an answer to this on the TPA support forums too.

The heatsinks are now not getting equally hot. With the PSU's set up as the manual describes, I would say the placid BP heatsinks seem acceptably hot, although one tends to be a lot hotter than any of the others. However, on the placid PSU, one heatsink is too hot to keep your finger on for very long, while the other seems pretty cool. My fingers tend to be fairly resillient to heat as well due to all the times over the past couple of years I've slightly burnt them soldering or cooking or whatever. IMO that particular heatsink on the placid seems too hot - but then again I don't know how hot these things are supposed to get. I'd assume not ridiculously hot?
 

Quote:

Originally Posted by digger945 

wrt your heatsink observations, it would seem to me at first that if your heatsinks are running hotter than normal then you are shunting a fair amount instead of using it. As this power supply is loaded the heatsinks should run cooler(not cool but not as hot), and as you back off on current demand the heatsinks will get hotter. Mind you this is a shunt power supply so the reason for heatsinks in the first place is to dissipate heat.

Assuming that you have the power supplies set up according to the users manual from the TP website, I have run and tested an unmodified(set up with the parts that come with the kit) bipolar supply north of 300mA without problems. It did have a load on the whole time and I can't recommend running one this way without further consulting the designers(Russ and Brian).

 

I also find that my Bipolar supply will drift quite a ways while warming up, and sags a bit when any load is applied, no matter the situation. I have the first gen supply(v2.1.1)

 

Saying that a heatsink is "hot" is relative to the user and builder, I think. What's hot to one is nothing to another. It seems to be relative and depends on experience.

 

I hope you get it all sorted out so that you can listen to your dac.

 

 

Umm... it is the heatsink attached to QP1, having looked at the schematic I assume it is a pass rather than a shunt? QN1 is between Out 1 and 2 (i.e. V+ and GND), making it a shunt correct? My reasoning may be all wrong with this, so please correct me if I'm wrong?

Assuming it is a pass (or if I'm completely wrong), would you expect that heatsink to get much much hotter than the other?
 

Quote:

Originally Posted by digger945 

You'll have to point out if the heatsink is a pass or shunt. Also, it wouldn't hurt to take a current measurement before and after hooking up the PS to see if it's in the supply or perhaps some unusually high draw from what's being connected. Maybe a solder bridge on something somewhere, or you are just pulling more current from one rail than the other.

Yeah I have adjusted the current as explained in the manual

Hi John, for the placid I'm using the 15VA Avel Lindberg that TP sell for the kits. I did quickly measure the AC from the both secondaries after first connecting the transformer to the IEC inlet just to make sure it was working correctly - I forget what the actual measurement was. I'll disconnect it from the placid tonight and take the measurements again. I'll be doing a spot of DIY this evening anyway, adding an XLR plug to my HD650's.

On a sidenote John, I've been looking at some of your builds lately - great work! You have some beautiful looking kit.
 

Quote:

Originally Posted by johnwmclean 

What’s you transformer spec? Have you measured the AC output over each secondary?