Step down (240v - 110v) transformer for KingRex T10 amplfier

[johnm]

Hi everyone!

I've just been sent a sample of the new TA2020 based KingRex T-amp, and very nice it is to. Nicely screwed together, and surprisingly weighty for it's size.

Unfortunately the KingRex PSU sent to me is the 110v/60hz version

Now, I have a Talema transformer with the following specs:

Primary 230V / 50-60Hz

Red/Black secondaries - 55v / 4,5A
Yellow/Orange secondaries - 55v / 4,5A

Can I wire together the yellow/black for 0v, and the orange/red for 110v, and feed this into the 110v (Taiwan) KingRex PSU? In theory this would seem to work, but I'm not sure about the Hz side of things. I'm assuming my 'step down' transformer would output 110V, but it would be at 50hz, which wouldn't work with the KingRex's PSU? The torroidal transformer inside the PSU case is clearly marked 60Hz...

Any help would be gratefully received.

Cheers,

- John

P.S. Even with a bog standard 12v 4amp power supply for a monitor this thing sounds pretty impressive already. Nice weight and scale and all the detail we've come to expect from the TA2020 chip. Looking forward to seeing what it's capable of with the proper PSU.

 

[luka]

There is so little diffrence in Hz (10) so there is no problem, yes connect secondary like you said, take volt meter and see if there is 110V. If there is you can connect it to your amp, but I would get one for 230V because it is silly to have that kind of amp and trafo wich is outside of case, but that is my opinion.

 

[johnm]

Hi Luka - thank you for your reply. Well if you're sure this is fine I will give it a go.

Agreed it would be best to have the proper PSU, but this will take another week or so to arrive, and I'm keen to hear what the T10 is capable of over this weekend.

Cheers,

- John

 

[luka]

Hi

Then you do plan to replace it for the right one...

Well as for voltage and Hz go if you put is amp what they ask for(110Vac) there is no problem if you use outside trafo just unpractical.

Just don't see how you will bring 110 to the amp.

 

[johnm]

P.S. Is it quite normal for larger potted torroidal transformer to make little tick... tick noises while in use? I guess you don't hear this when inside a case, but on a marble chopping board (always do this incase of any sparks or flames if something is wrong) it's a little disconcerting.

Everything measures Ok.

- J

P.S. In the first post I meant link together yellow and black wires, with orange and red for the AC connections to amp.

 

[robert1325]

Where did you get that amp? I want one !

 

[johnm]

I wrote off to them

 

[robert1325]

OK, excuse me for going off -topic,

But the binding post, they only accept banana plugs? , This might be a good alternative for Charlize... The PSU is no problem, i've got one of the skyneyt 8080 modules ... Should start using it sometime with my trends

 

[johnm]

I use the Skynet 8080 as well, with a 20,000k stiffener cap with an Amp6 Basic. Sounds pretty good.

Yes the amp only accepts banana plugs, and - as far as I am aware - the KingRex comes with a simple plug-in walwart affair. The PSU is an extra option. So you'll be fine with the 8080.

Thanks for your help Luka - the amp's PSU is working fine with the step-down transformer Frighteneing levels of bass control now! Wow!

- John

 

[johnm]

P.S. Forget about what I said about the step down transformer ticking - turned out to be something else entirely

One thing I have noticed though, and not sure if it's cause for concern or not, but the torroidal 110v/60Hz transformer inside the KingRex PSU gets very hot in use.

Is this sort of thing normal, or is it because I'm stepping down from a 240v 50hz mains supply to a 110V 60Hz transformer?

Thanks,

- John

 

[luka]

Hi

I don't know if this is normal or not, I would say not but I could be wrong. Since you put 110v in, there is no diffrence if it cames from wall socket or transformer. Don't know it that 50Hz instead of 60Hz makes any diffrence either.

 

[johnm]

I think it's the 50hz running into a 60hz transformer. It really is too hot to touch and is making the whole chassis very hot. Definately not normal so I've gone back to using my Skynet 8080 SMPS supply, which sounds fantastic with the KingRex so not all bad.

I'll wait for the 240v KingRex PSU in the meantime. If that gets way too hot then it must be a bad design. I'll keep them informed as I'm sort of testing the amps for them and letting them know what I think.

Cheers.

 

[jtjames]

I will suggest you use PSU for best sounding. The switching power supply is a bad option. i tryed many other switching type power supply (but not 8080).they use for t20 amp i feel the bass punch is very pool.
In 50hz or 60hz 110ac for psu is no difference,I tryed PSU+T20 AMP+ CD PLAYER in 110v wallsocket ,continue run music over 72hours(the t20 amp volume knob set on 12 o'clock position,it can normally work. the traditional power hot then switching power is normal and OK.(could you tell me how many degree temp on psu ,you sai'd is very hot),mayby you can use volt meter to check your 110v ac(it should be 110v-120v is good).

Sincerely yours

james

 

[johnm]

I respectfully disagree with you. The Skynet 8080 SMPS sounds great with the KingRex T20 (sorry I have been writing T10 throughout this thread - whoops!). Mine's putting out 13.3v. The music is very smooth, but never boring. Loads of detail but not artificial in any way - it just sounds natural. Great bass weight, which may be in part due to the Nichicon 20,000uF cap on the output of the SMPS. The amp - with no music! - is dead silent with my ear against the speaker as well which isn't the case with another SMPS power supply (for a PC monitor) I tested. I think the 8080 is a very well designed PSU.

Using my stepdown transformer the torroidal inside the KingRex PSU got so hot you could smell the rubber isolation pads used top and bottom on the transformer - surely not a good sign. The circular metal fixing plate on top of the transformer was scorching hot to touch - not red hot but the heat was travelling through the fixing bolt and into the rest of the chassis. The underside of the chassis was again too hot to touch. This kind of heat is not kind to capacitors and would probably result in those having a far shorter life-span than they should. The transformer also buzzed quite alot as well. If this is normal and it does get hot there should be ventilation slots in the top of the chassis... I like to leave my amps on all the time, which isn't possible or safe when the PSU is this hot. I'd worry about insulation on wires possibly melting or a component failure.

I shall do as you suggest and measure the voltage - perhaps it is too high where I live.

Cheers,

- John

 

[johnm]

Update: Just measured the voltages before and after the stepdown transformer. This transformer has a 500va rating by the way.

Before, it's 237v, and after it's 121.3v. This seems slightly high - could this account for the heat being generated?

- John

 

[DocLorren]

No, what you probably have going on is a fixed loop around your toroid. This means that a loop of conducting material (probably the center bolt, top/bottom plate and casing) will act as a functional extra turn of wire around the toroid and behave like a shortcut at the same time. Advise: remove the center bolt and just attach the toroid with some plastic tie-wraps to the ground plate. Then see what happens. A 500VA trafo should not be under any strain with a TA2020 based amp. See also my own experience with this phenomenon.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=93198&highlight=

 

[johnm]

I was using the PSU with the top plate off and still getting this heat. Just had a check and there appears to be no loop in the system that you speak of, and there is plenty of space around the transformer.

Thanks for your link - will take a look at that now.

Cheers,

- John

 

[jtjames]

some transformer output side when you serial connect two coil you must consider the coil direction.
could you change the stepdown transformer output line connection and test the temp again.ths
pls see the attach file to change it.(from a to b)


sincerely yours

james

 

[jtjames]

maybe you try 240 to 120v transformer is best solution,i ask some friend they say in a transformer output side two separated coil can't serial connect,it will cause some problem.because the magnetic field direction will chaos.

Or you can wait more days,she will send another 240v input PSU for test.

sincerely yours


james

 

[johnm]

Thanks for your information James - I take it you work for KingRex? Impressed with the amp using the skynet 8080 - from experience I know the chips take a few days to burn in so I'm looking forward to the sound improving over the next few days.

On my step down transformer I currently have the Yellow and Black connected, and the red and orange supplying 121v ac to the Kingrex PSU.

Transformer details are:

Red - 55V / Black - 0V

Yellow - 55V / Orange - 0V

The informatin sheet says it can be connected in series or parallel.

Perhaps I should try joining the Black and Orange as you suggest in diagram B and see if that makes a difference?

Cheers,

- John