UpTone JS-2 Power Supply Listening Impressions

[JohnSwenson]

Ah, "the Internet of Things."

 

Ahh,

that just brought to mind the following scenario:

 

Your lights start turning off on their own and you hear coming from everywhere at once:

 

"Dave, you haven't talked to me in a while, I'm feeling lonely..."

 

 

John S.

[JohnSwenson]

I'd be very interested to hear JS' thoughts on the pros and cons of using a battery PS. You can for example buy a 5v 2 amp rechargeable power pack (designed for recharging smart phones etc) relatively cheaply. Some people report very good results vs a linear PS when powering R Pi and such like.

 

I am not a big fan of such devices for audio purposes, they are designed to charge a battery, not provide a clean low impedance source. You can guarantee that these are using the least quality parts they can get away with. But it is still a battery and if you are in a situation with ground loops they will break those loops and that can be a good thing.

 

John S.

[JohnSwenson]

And don't a lot of them use cheap switching regulators to get the right output voltage from the battery?

 

Yes, they use cheap switching DC/DC converters, but even the worst of these are considerably better than than the common AC switcher.

 

A good linear regulator will easily trounce these, but they are still better than almost any AC SMPS.

 

John S.

[JohnSwenson]

Any more inputs/responses on this question concerning improvements in JS-2 after break-in/stabilization of capacitors and stuff?

 

Large scale macro behavior will not change significantly with breakin. There are ALWAYS some macro effects due to temperature. When the unit is cold you can always get more short term current out of it than when it is hot. When it is hot you have less margin before internal components reach their thermal limits. The JS-2 is quite thermally robust so you really have to pull hard on it to notice this, but it is there. For example if you have a computer that at its normal condition is pulling so much current that the JS-2 gets HOT but is not yet in thermal limiting, something that causes the computer to draw significantly more current could cause it to go into thermal limiting. Doing that while it is cold you probably wouldn't notice anything.

 

Small transient behavior WILL change overtime during the first couple of days. For example when driving a computer the highly transient load will cause some voltage noise on the output (the JS-2 is very good at minimizing this, but it isn't perfect). The exact details of this noise will change during the first few days of use. I have not done any studies on exactly how it changes, I just have one production JS-2 and I have been using it for a long time, so it is LONG past any burn-in.

 

Due to how these things change in other equipment that I HAVE looked at, my guess is that it will be pretty good at first, then over the first day get much worse, then over the next couple days get much better than it was at first.

 

John S.

[JohnSwenson]

The grounding thread was about dealing with high impedance leakage from SMPS, the JS-2 is NOT an SMPS so it does not have any high impedance leakage to deal with.

 

The outputs of the JS-2 are isolated from each other and the chassis and the ground pin of the AC input. The chassis is connected to the ground pin of the AC input.

 

 If WANT to have one of the outputs connected to AC ground pin you will need to do that externally. There is normally no need to do this. The only reason I can think of to do this is if you are using the JS-2 to drive one of the specific LAN switches, which in order to shunt network leakage need a power input whose negative is connected to AC ground. Other than that there should be no need to ground the output of a JS-2.

 

John S.

[JohnSwenson]

What do you mean by phase in this respect? There is a switch, a fuse then the two sides connect to the primary winding of the transformer. What does "phase" mean in this arrangement? Neither side is connected to anything else other than the primary of the transformer.

 

How does it matter which pin gets connected to which side of the primary winding? Neither side of the jack gets connected to safety ground.

 

Can you provide a schematic of what you mean by phase? That link provided gives no indication what it is actually measuring.

 

John S.

[JohnSwenson]

5 hours ago, basillus said:

Hey. I'm not sure this is the right thread to write in, but couldn't find a technical JS-2 thread ; 0) The JS-2 is beautiful and would fit in my other aluminum cabinets, so I should have ordered one with my EtherRegen ...

Well, to the question:

If the JS-2 can deliver up to 7.2A at 12v, will the used choke 159ZJ not be “stressed” as its specs. is 10mh 5A? 

It wouldn´t have been better to use the 159ZL 2,5mh 10A?

On the inductor there are two two things that can be "stressed", one is core saturation and the other is temperature. For the core saturation what actually matters is the voltage ACROSS the inductor, NOT the voltage or current at the output of the supply. Those current specs are not the actual limit, but are based on a particular circuit design popular with tube amplifiers many decades ago with a particular high voltage. If you built such a design with the particular voltage and current, you would reach the limiting voltage across the inductor. These specs were designed to make it easy for a DIY type to know if a particular inductor would work based on the output specs of the supply. Trying to calculate the actual voltage drop across the inductor is not a trivial task, so the manufacturer chose this method to make it easier for non experts to choose the proper part. Those voltage and current limits are not actual limits like we are used to seeing. You can safely go to higher voltages if you use lower currents, or higher currents if you use lower voltages.

 

With the circuit we are using and the voltages and currents involved we are very far away from the actual limiting voltage of the inductor.

 

The other "stress" mode is temperature, given where we are in the magnetic range we have very low core losses, so most heat comes from just plain IR losses in the wire. These wires are thick enough so the resistance of the wire is low enough that again we are not putting anywhere near enough current through this to get it hot.

 

So don't worry about the inductor in the design not being appropriate. Everything in this design is well within operating range. A lot of time was spent getting everything as good as we could get it.

 

John S.

[JohnSwenson]

8 hours ago, basillus said:

Thank you very much for the great answers to John and Alex ;0)

The main reason I asked was because I fell over this old thread

https://www.audioasylum.com/forums/pcaudio/messages/4/43048.html

where John just mentions the symptoms when zj159 gets "stressed" and then I thought that the 7.2A sounded of a lot ;0) 

But it was written over 10 years ago and a lot has happened since and you have gained more experience and knowledge about many things that have helped you develop a JS-2 from then to now. 

I've never seen a psu with 3 rectifier diodes and have no idea how this rectifier works ;0)

There really are four diodes in a standard configuration, its just that two of them are in the same package, so one half of the bridge is in one package, but they don't make a package with two diodes hooked up the other way to use for the other side of the bridge, so that side has to use two single diodes.

 

John S.

[JohnSwenson]

7 minutes ago, mtcs said:

Does anyone happen to know the sustained and max power consumption (in watts) for the JS-2? Thanks.

By max do you mean short term? If yes what time frame are you interested in? By power consumption do you mean the power drawn through the AC line cable, or the amount of heat dissipated in the heat sinks? These can be quite different. The output voltage dramatically affects these numbers, so is there a specific voltage you are interested in?

 

John S.