Power Inlet for AKSA

Carlman · « **on:** 4 Feb 2003, 07:43 pm »

Based on comments here regarding the IEC/Switch all-in-one device, I want to use this inlet module from E-T-A:
http://www.etacbe.com/n_america/new_products/3130_inlet/index.html

However, I cannot find it and would like a little help with 2 things:

1. Where do you get them? I'm trying the local shops they recommended but the part numbers aren't correct on the website.

2. Specific amperage needs. What would be the proper amperage on this switch/breaker? 10-20 amp? (for AKSA 100W)

Thanks for any help you can offer!

-Carl

AKSA · « **Reply #1 on:** 4 Feb 2003, 09:18 pm »

Hi Carl,

A Swiss company called Schurter make these integrated power entry modules, some even with RF filters built in. They are certainly convenient, but some people like the switch at the front of the case, not the rear.

I'd suggest the high current one; 16A is best. It will last well.

Cheers,

Hugh

Carlman · « **Reply #2 on:** 4 Feb 2003, 09:49 pm »

Unfortunately, I think the only one I could easily use is the 10A... (probably the KFBII) unless I got a new IEC connector. The blades are horizontal instead of parallel on the 16A.

I don't mind the switch being in the back. I'll only turn it off when I'm moving, or going away for a really long time.

-Carl

AKSA · « **Reply #3 on:** 4 Feb 2003, 11:05 pm »

Hi Carl,

OK, then perhaps go with the 10A rating. It won't last as long, but might still have a life in years.......

Cheers,

Hugh

U4EA · « **Reply #4 on:** 5 Feb 2003, 03:28 am »

Is this high amp recomendation because of in rush current? If so, why is in rush an issue in the AKSA? Is it the same issue in other amps?

Just curious and sorry if it has been covered before.

JohnR · « **Reply #5 on:** 5 Feb 2003, 04:53 am »

Toroidal transformers (as recommended for the AKSA) have a high inrush current. It's nothing to do with the amp itself.

Embarassingly enough, the exact reason escapes me just now...

J

AKSA · « **Reply #6 on:** 5 Feb 2003, 05:37 am »

High inrush current is a perennial issue with toroidal transformers.

The reason is subtle; AC quiescent in the transformer is limited by the inductance of the primary rather than the DC resistance of the windings. Inductance is dependent on number of turns, dimensions of the toroid, and the core. Toroids have a low copper content; the coupling between windings is very tight since the core is fully enclosed, and not many windings are required to give good performance. This means that ohmic losses are low, and until the magnetic field is brought to existence, the input current is very high as the retarding (cf. reactive) magnetic flux builds up. At switch-on, current inrush is therefore much greater than an EI transformer, reflecting low resistance, and the rapid buildup of a magnetic field to stabilize the quiescent. This typically takes a couple of full AC cycles.

On top of this, the toroid must, via the rectifiers, charge up the power supply capacitors. This also contributes to inrush current.

The inrush current, however, is not really the problem for the switch. At switch off, Lenz Law tells us that the magnetic field in the toroid will react violently to attempt to maintain the energizing current. As in a Kettering ignition system for a car, when the primary circuit is broken (though depending a little at what point in the waveform this happens), the collapsing magnetic field in the toroid will create a large voltage across the primary inputs of the transformer. This high voltage - often thousands of volts - will attempt to arc across the contacts of the switch, and will, over time, erode them. Some recent reading revealed to me that the snubber cap quenches this arc, just as does the points condenser in a Kettering Ignition system, and thus prolongs the life of the switch.

Cheers,

Hugh

SamL · « **Reply #7 on:** 5 Feb 2003, 07:50 am »

A bit off subject.

Just wonder how many people acutally use circuit breakers instead of fuses for the power supply? Are they the type that I can find in my home power box?
Also, are there any down side of using illuminated power switch? Will LED looks better?

Sam

Lost81 · « **Reply #8 on:** 5 Feb 2003, 10:54 am »

Kudos to Hugh for pre-emptively answering my question about what happens when the switch is turned off.

Now, I am wondering, is there a benefit to having 2 switches?
One for the Primary Winding of the transformer.
One for the Secondary Winding of the transformer.

That way, I can turn on the primary switch.
Wait a few seconds for the primary winding to stabilize,
and then flick on the secondary switch.

Will this solve part of the inrush current problem?

Notes:
Assume I am using 16A Rocker Switches for both.

Thanks!
benny

blizzard · « **Reply #9 on:** 5 Feb 2003, 12:53 pm »

How about a soft start and soft stop circuit. This would ease up to full power and ease down to off. I would think ramping up and down like this would be much easier on all parts of the amp. The only caution I would see here is to be careful about ramping too slow with the AKSA. At the lower line voltage levels there is some DC offset that might hurt the speakers if that point is maintained too long. Normally, when she is turned on, this time period of DC offset is so quick that there isn't enough time to do damage. But, if you were to design a circuit that held this point too long, you could possibly have a problem (I think). My guess is that you would want to ramp up and down in no more than about 2 seconds.
I have never built or designed a circuit like this. So, I may be off base or missing a cruicial point here. But, this is the approach I would at least look into.
Steve

Carlman · « **Reply #10 on:** 5 Feb 2003, 02:46 pm »

I was originally intending to use 2 IEC's, 2 switches, etc. and then found out about the 2-pole options on all of the switches. So, I thought, simpler, easier, etc. to do just 1 switch/iec. The Schurter with line filtering looks like a nice design and I want to stick with it... And, I also want it to last a long time.

Since the particular IEC/switch combo is only available in 10 amp, I think I'll just buy 2 and wire each transformer separately from the outlet. It's a dual mono so, I'll just go all the way with that thought. I don't agree that a first stage/second stage power scenario is a great idea. I would think that would limit the transformers ability to quickly obtain electricity to feed the caps during operation. I think in this particular amp, speedy power delivery is key.
-I may be totally wrong, I'm just thinking out loud.

I think the caps that absorb the power going back to the switch sounds like a great idea and I'd like to incorporate that into my amp. Hugh, is that something I can get directions on how to do or is that something that's already included?

Thanks for everyone's input.

-Carl

Carlman · « **Reply #11 on:** 5 Feb 2003, 04:00 pm »

I talked to a great technical person at Schurter.
They have a 15a breaker/switch. Here:
http://www.schurterinc.com/pdf/usa/c_5145.pdf

It has a 1000 amp in rush capability. The other one I was looking was rated at 70 amp. This one has a breaker, the other was a switch.

Thanks for the help, Hugh. I knew what to ask for when I talked to them. I think this is THE switch for me.

-Carl

P.S. www.alliedelec.com carries this part but, appears to have limited options and availability.

karthikn · « **Reply #12 on:** 22 Feb 2003, 09:25 pm »

Hi Carl, thanks for posting this info. What options did you choose for the switch - RF filter, undervoltage protection, medical version etc.

Thanks
Karthi

Carlman · « **Reply #13 on:** 22 Feb 2003, 09:42 pm »

I ended up getting a fairly plain one since it's all Allied stocks. Allied buys them from Schurter in popular configurations so, you can't get a lit button with 'on' and 'off' printed on it in black... You take what they have. Schurter will sell any configuration you want if you buy about a thousand or so. I didn't need $35,000 worth of IEC power inlets with breakers, so, I chose from Allied's stock.

Hopefully, this link will work:
This is the exact item I ordered

It's got a filtered IEC inlet, wired to the breaker, and has a white on/off switch with the "| and O" for on and off. It's NOT the medical version.. in fact, the medical version is not recommended for this application according to a technical guy at Schurter. I don't remember why but, it's not.

Good luck,
Carl

Jonpike · « **Reply #14 on:** 23 Feb 2003, 09:16 pm »

Quote from: blizzard

How about a soft start and soft stop circuit. This would ease up to full power and ease down to off. I would think ramping up and down like this would be much easier on all parts of the amp. The only caution I would see here is to be careful about ramping too slow with the AKSA. At the lower line voltage levels there is some DC offset that might hurt the speakers if that point is maintained too long. Normally, when she is turned on, this time period of DC offset is so quick that there isn't enough time to do damage. But, if you were to design a circuit that held this point too long, you could possibly have a problem (I think). My guess is that you would want to ramp up and down in no more than about 2 seconds.
I have never built or designed a circuit like this. So, I may be off base or missing a cruicial point here. But, this is the approach I would at least look into.
Steve

That's another way to go, and you see circiuts like this used when the inrush is large.

One way is to put a large, low value resistor in series with the AC line, and have a relay on a time delay circuit bypass it (short it out) after a second or two.. the inrush is softened by the resistor, then you're back to a direct connection.

Going slow could be a problem, but the neccicary time will be pretty short, as Hugh said, the transformer inrush is pretty fast, even if it takes several cycles (16mS per cycle). The caps charging up probably takes longer, but I doubt more than a second.

It would take some added complexity, not a whole lot.. Probably the best way would be to build your "timer" out of a cap being charged by the DC side of the power supply.. resistor network to drop the 36 or 50V down to the relay voltage (12, 24V?) a cap of the right size to charge thru the resistor for a time constant such that the relay pulls in in 1-2 seconds, and there you go.. Could be as simple as 5 parts.. 6 if you add a cap across the contacts to damp that arcing (good idea).

But, dual mono would complicate things a bit more.. You'ld probably want to come up with a way to turn things on at the same time, though I guess there is no reason not to have the two seperate supplies with separate soft start circuits turning on at slightly different times..

Hmmm.. now I'm envisioning a third relay for AC power to both channels, line voltage AC coil, a small switch for main power on, and two soft start circuits with their parts and relays.. A little more complicated, and more space taken up, but you end up with one small switch you can mount anywhere on the box and dosen't carry the high current, and one power entry.

An added benifit of a relay with heavy contacts is that it would last far longer than a small switch under a large inductive load like this.

Gee, it was just a little idea when I started!

blizzard · « **Reply #15 on:** 24 Feb 2003, 12:30 am »

Hi Jonpike
That sounds like a winning plan. I have an old dual mono Crown amp that does this. The one channel takes about a second and then the second channel starts up. At least I think this is what's happening. Initially the channel goes into a standby mode where it does diagnostics. I assume that it also limits power inrush here. Then after standby, it goes full. The entire process takes about a second per channel.
A similar soft start would also be nice for TLP and GK-1 owners, who want to extend tube life (and other components for that matter). This does not have to go full so quickly. You can 10 to 20 seconds here -- in stages (maybe 2 or 3 steps). I don't know if it is worth the added complexity. But, it would make an interesting project.
Steve

jonwb · « **Reply #16 on:** 12 Mar 2003, 10:09 pm »

I read through this post and found it very informative.

Let me first say that I am not an Eletrical Engineer or Technician. In fact I am quite the opposite, I am a mechanical engineer.

One thing that popped into my head as I was reading was why not put a wall dimmer switch on the amp, and wire it in parrallel with a "regular" power switch. That way you'd turn on the amp with the dimmer switch (over a three count), then flip the regular power switch on. You'd want to, of course, turn on the dimmer switch with the knob or slider turned down and then turn it up. Once you've turned up the dimmer and flipped on the regular switch you could in theory turn off the dimmer so the electricity would only be running through the regular switch (which would never see the notorious in-rush).

Crude yes, but would it work? It sure would be cheaper I reckon...

PSP · « **Reply #17 on:** 12 Mar 2003, 11:27 pm »

Hi Jon,
Most of the hi-fi mafia are on a total quest for pure, uncontaminated AC power (spikes, surges, noise from refrigerators, air conditioners, etc)... and dimmer switches almost always make the afore-mentioned list of audio infamy.

Most who have read all the "pure power" posts would be willing to sneak into their neighbor's house to remove a dimmer switch and few would put one in their amp. I don't know, never tried it... just telling you what you hear on the street...

Peter

jonwb · « **Reply #18 on:** 12 Mar 2003, 11:48 pm »

Quote from: PSP

Hi Jon,
Most who have read all the "pure power" posts would be willing to sneak into their neighbor's house to remove a dimmer switch and few would put one in their amp. I don't know, never tried it... just telling you what you hear on the street...

I was thinking the same thing... but then I thought, what harm could come from it since after powering the unit up via the dimmer, and then flipping on the regular power switch and then turning the dimmer off.

I wouldn't think the dimmer could do any harm (interference) when the switch itself is off. Could it???

Besides, who wouldn't want a classy looking big ivory knob hanging off the front panel of their amp...

blizzard · « **Reply #19 on:** 13 Mar 2003, 12:42 am »

Hi Jonwb,
Theoretically this sounds ok. Don't know how well it would work in practice. Number one, the dimmer should be rated pretty high -- at least 300 Watt load capacity (a variac might be better here). Number two, I would think that the switch should be make-before-break, so that the power doesn't turn off quickly before it makes contact (you will end up with the power surge that you were trying to avoid in the first place). Number three, with the AKSA it is imperative that she's powered up quickly. There is definate DC offset at lower voltages. Three seconds is way too long. Power should be ramped up in a second or less. If you ramp up slower than this, you should have a muting circuit that will keep the output open circuit until full power(but then there would be a relay in the amplifier output). Lastly, you should make the start up sequence idiot-proof. You do not want to make a mistake in the sequence -- like ramping too slow -- or something could get damaged.
It's a good idea. But, it's not as simple as it sounds. A good soft start circuit would be better in my opinion. It would be more consistent and more foolproof. But, this is not that simple either. The timing portion of the circuit has to be made to work fast. The circuit aslo must not click on and off with a slight power interruption. And, finally the relay must be reliable and made to operate without chatter.
I realize that my comments are not very constructive. I'm really just trying to express areas of concern. Don't rush into this project without thoroughly thinking it through, or you could destroy your speakers, amp, or both. Done properly, it's a very good thing. You will definately extend the life of you components.
Good luck,
Steve