How to power on amps with no on/off switch?

Amplifier in question: Hafler DH200 with switch bypassed.

If I'm not mistaken the Hafler was paired with the DH-101 preamp as seen here (pic from the web). My guess is that you plugged the power amp into the back of the pre and when you turned on the pre it turned on the power amp.

That being said what kind of pre-amp is the OP using?

Edit: I was responding to the title of the the thread however when I reread the OP's initial post I see he/she wants to connect 3 amps.

May I ask why? what are you hoping to accomplish by having 3 power amps connected? Just my opinion bu that sounds like overkill


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Stock DH-200s, E+I transformers and total of 60,000uF. Inrush current is not going to be a problem. 20A spec grade wall switch will be overkill and overkill is O.K. (okay)

No need for sequential turn on and it's not going to draw 1800W just to charge up the caps. If you want to, add an inrush current limiter to each amp.
Double checking...

You are saying that ONE 20 amp wall switch is overkill to turn on THREE hafler dh200 amplifiers. 30 amp would be even more overkill.

Am I understanding you correctly?
 
Since I had open walls, I created four (4) twenty amp circuits so I'd have plenty of options.

I currently have it split up where you walk in.....hit the four upper switches and everything you need turns on. Wife (who abhors electronic items) can simply hit them all down as she leaves for the evening.

Since I knew I'd have some items that always need power, I went to every single outlet and split them. Every upper half is switched and every lower half is hot so now I can leave certain items always plugged in (Satellite for example).

Took some time/thought to get it figured out but it's worked exactly as I'd hoped.

I also left some space in the garage (next to the 2nd panel box) where I can stick a four circuit SurgeX protector. (I might add this was one large reason why I went with four circuits.... nobody using horns needs this much power available....BUT, since the SurgeX has room for four circuits......four it is!

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Double checking...

You are saying that ONE 20 amp wall switch is overkill to turn on THREE hafler dh200 amplifiers. 30 amp would be even more overkill.

Am I understanding you correctly?

Yes. These are not class A amplifiers that draw their maximum at turn on and during idle. According to the Hafler manual, at idle the amp consumes 100VA, less than an amp each. At 100W into 8 Ohms, it's 370VA or a little over 3A.
I'm not sure where someone got the 600W of current draw for each amp. Are these 200s or 500s?

Not to mention, in a home application you'll be using nowhere near 100W continuous per channel.
 
The key term here is turn on...

The turn on surge just as a ball bark number for three of these amplifiers could be over 100 amps for the first half cycle of the AC mains wave form, depending on what part of the waveform is being switched.

upload_2018-9-12_13-25-52.png

There is something called switch bounce, that is the contacts may make and break several times during each activation of the switch. This will create an arc between the contacts that can and does eat switches for lunch.

If a switch is going to be used to switch an inductive load with a high surge current, one should use the correct switch snubber device, commonly called (although it is a brand name) a Quencharc.

upload_2018-9-12_13-41-43.png

The untamed arcs can induce voltage spikes that some pieces of electronics may not be happy with.



Note that the amplifier(s) under discussion employ a capacitor only snubber across the power switch, but it is bypassed when the power switch is on.

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I understand that it is not uncommon for the above to be ignored. I am not trying to be the switch police.
 
Are you planning on hiring an electrician to run a 30A circuit for these amps? If you're plugging them in to a 15A circuit from your breaker and are worried about needing a 30A switch, then you better run a 30A feed.
 
The key term here is turn on...

The turn on surge just as a ball bark number for three of these amplifiers could be over 100 amps for the first half cycle of the AC mains wave form...

Where are you getting this ball park number of 100A? He's not turning on industrial motors in a factory.

With over 30A per amp at turn on, those 5A fuses would pop even though they are slow blow.

Your graph should be based on the current at idle from three DH 220s, 300VA or 2.5A and the actual load presented by three of these during turn on.
 
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Yes. These are not class A amplifiers that draw their maximum at turn on and during idle. According to the Hafler manual, at idle the amp consumes 100VA, less than an amp each. At 100W into 8 Ohms, it's 370VA or a little over 3A.
I'm not sure where someone got the 600W of current draw for each amp. Are these 200s or 500s?

Not to mention, in a home application you'll be using nowhere near 100W continuous per channel.
On the back panel of a dh200 it says 600watts max. These are indeed dh200 amps in question, not 500s.
 
Are you planning on hiring an electrician to run a 30A circuit for these amps? If you're plugging them in to a 15A circuit from your breaker and are worried about needing a 30A switch, then you better run a 30A feed.
The 30 amp circuit is already in place.........30 amp breaker and 10 gauge wiring and the receptacles are in place.
 

There is something called switch bounce, that is the contacts may make and break several times during each activation of the switch. This will create an arc between the contacts that can and does eat switches for lunch.

My basic understanding is that this is why hafler on/off switches don't last and this is one of the reasons I am attempting to bypass the switches and come up with something more reliable.
 
If a switch is going to be used to switch an inductive load with a high surge current, one should use the correct switch snubber device, commonly called (although it is a brand name) a Quencharc.

Is this something that can/should be installed on a 20 or 30 amp wall switch?
 
Where are you getting this ball park number of 100A? He's not turning on industrial motors in a factory.

With over 30A per amp at turn on, those 5A fuses would pop even though they are slow blow.

It is the inrush current of the discharged main filter capacitors. Basic capacitors 101.

There are any number of online calculators that one can use to come up with similar numbers or one can do the calculation.

My example is based on 30,000 microfarads, because the positive and negative sides charge at different times for a bipolar power supply.

I used a transformer secondary voltage of 60 volts, although I did not see B+ or B- voltages on the schematic, because the main filter capacitors are shown to be rated for 75 volts. The surge current shown in my example will be in the ball park when compared to measured values for known power supplies.

You have to do the math for the type of fuse. See the chart below.

upload_2018-9-12_15-9-43.png

Since we are talking about 60 Hz power, we have to look at the time period for half a cycle and when the switch is operated in terms of the crest factor of the AC mains sine wave.

The chart above shows that the 5 amp fuse will hold over 100 amps for about a half a cycle (.01 seconds) and hold 50 amps for about 5 cycles (0.1 seconds).

To be sure these are just ball park numbers, but they are close enough for the purpose of this discussion.

Even if I drop the the transformer secondary down to 40 volts which will put about 60 volts on the filter capacitors, the surge current only drops down to about 90 amps for my example.

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My basic understanding is that this is why hafler on/off switches don't last and this is one of the reasons I am attempting to bypass the switches and come up with something more reliable.

I had a Hafler DH-200 for 20+ years. At one time it was my daily driver. I never had any sort of problem with the power switch.
 
I like music,
You switched from inductive to capacitive. The transformer type, rectifier type and capacitors all play a role in turn on. Where did you get that fuse chart?
60V on the secondary? Or was that 30-0-30? Did you mean to say 60V rails?
You come across like you know what you're talking about, except sometimes...
 
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Is this something that can/should be installed on a 20 or 30 amp wall switch?

If the wall type switch is mounted in a separate DIY enclosure there is not problem, but I would have to look at the NEC for a switch installed in a wall and local codes may be more strict, I just do not remember what the NEC says about this (I know, I am old, broken down, not healthy and on medications)...

For those that want to DIY there own, there are switches in various formats (rocker, toggle and so on) that are rated for high inrush current. See the picture below.

This is just one example, there are higher rated switches available.

upload_2018-9-12_16-4-12.png
 
I like music,
You switched from inductive to capacitive. The transformer type, rectifier type and capacitors all play a role in turn on. Where did you get that fuse chart?

Not exactly, I was talking about power supply inrush current for the amplifier under discussion, then I mentioned that if the load is inductive it is not necessarily a bad idea to use a snubber on the switch.

This is what I posted regarding the amplifiers in discussion, it says nothing about inductive load.

The turn on surge just as a ball bark number for three of these amplifiers could be over 100 amps for the first half cycle of the AC mains wave form, depending on what part of the waveform is being switched.

Then I posted...

f a switch is going to be used to switch an inductive load with a high surge current, one should use the correct switch snubber device, commonly called (although it is a brand name) a Quencharc.

Read what I posted, an inductive load, which the amplifier is because it has a power transformer, and it is high surge current because of the power supply capacitors. What this means is there is a lot of stored electrical energy in the transformer which can result in some fairly powerful arcs and not insubstantial voltage spikes, hence the need for the snubber.

There was no changing from inductive to capacitive.


The chart above is fuse time to clear/blow from Littelfuse for one of their variety of 3AG slow blow fuses. It is just fuse 101. There are any number of time to clear charts from different manufactures that show, if not exactly the same, very similar times to clear as shown in the picture below.

upload_2018-9-12_16-25-45.png

Again, this information,depending on the particular fuse is pretty much common knowledge in the world of fuses.
 
How about a master control relay? They have coils that run on 24 volts and the contacts can handle gobs of current.

BTW, you are going waaaaaaaaay over the top with this stuff.....
 
How about a master control relay? They have coils that run on 24 volts and the contacts can handle gobs of current.

BTW, you are going waaaaaaaaay over the top with this stuff.....

Yes, yes we are and that's the reason I'm not going to ask the previous poster about "stored electrical energy in the transformer" :crazy:
 
There is nothing over the top, just a fair amount of information, such as adding the correct snubber to a switch, and the correct time to clear for fuses and so on and correcting those that do not read what I say in my posts.

Since there are now over 600 hits on this thread, there must be at least a small amount of interest in the correct information.

Of course a person could put any cheap switch in a box along with a duplex outlet and call it good, and it is safe to say that this may not be all that uncommon.

60V on the secondary? Or was that 30-0-30? Did you mean to say 60V rails?

This pretty much explains it, the voltage on the filter capacitors, although I reposed with a value that is likely closer to what is in the amplifier.

I used a transformer secondary voltage of 60 volts, although I did not see B+ or B- voltages on the schematic, because the main filter capacitors are shown to be rated for 75 volts

To be clear it should have been closer to my revised example.
 
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