Amp with only headphones connected. No speakers.

[Cool Dude Ted]

Morning all.
There is a fair chance that my brother will end up buying my Rega Brio when the Quad kit arrives.
To begin with, he’ll only ever have headphones connected.
Although by plugging in headphones the speaker output is disabled, would anyone have any thoughts about how we could go about protecting the amp on those occasions when the headphone jack is removed whilst the amp is still on? It’s going to happen, I just know it.
Is there a recommended way to put (say) resistance across the speaker terminals, without needing a degree in electronic engineering to concoct something?
Apologies if this is all a bit basic.

 

[Lawrence001]

It's nothing to worry about only valve amps have an issue with that. But I wouldn't keep it on for hours at a time if it's not being used just for good practice. But that's a whole other debate...

 

[Cool Dude Ted]

It's nothing to worry about only valve amps have an issue with that. But I wouldn't keep it on for hours at a time if it's not being used just for good practice. But that's a whole other debate...

Thank you, Lawrence.

 

[uzzy]

The headpone socket will be a fed from the main loudspeaker output with some wiring inside with resistors etc to bring the output down to the level needed by the headphones. This means provided the headphones are plugged in the amp will work fine - however tell him to make sure he does not put something on to play with no headphones connected. Even a short blast at high volume with no speakers connected can destroy the output stages (unless the amp has some sort of built in protection)

 

[MartinC]

The headpone socket will be a fed from the main loudspeaker output with some wiring inside with resistors etc to bring the output down to the level needed by the headphones. This means provided the headphones are plugged in the amp will work fine - however tell him to make sure he does not put something on to play with no headphones connected. Even a short blast at high volume with no speakers connected can destroy the output stages (unless the amp has some sort of built in protection)

I'm about 99% sure that's not true as per Lawrence's post above. I've never heard of this being a genuine concern with any solid state amp anyway.

 

[uzzy]

I'm about 99% sure that's not true as per Lawrence's post above. I've never heard of this being a genuine concern with any solid state amp anyway.

Take virtually any solid state amp - disconnect the speakers and play your source at volume and watch the output stage go up in smoke. With no input being amplified (i.e. if the volume is turned to zero or no source is connected) then switich on a SS amp is fine. However, if you switch on the cd and play it and turn the volume up then .... bang

 

[rabski]

Even a short blast at high volume with no speakers connected can destroy the output stages (unless the amp has some sort of built in protection)

Sorry, but not on the vast majority of solid state amps. In most SS designs, the voltage remains stable with or without any load, and without a load there is no current flowing. The exceptions are some amps (mostly Class-D) that can oscillate with no load, and the few solid-state amps with output transformers.

The situation with valve amps (and solid-state with output transformers) is different, as with nothing connected, the amp will try to drive an infinite load. The circuit will put power through the primary windings of the output transformers, but with no balancing load on the secondary windings then the voltage will increase because there is no current and it can destroy output transformers.

As per life in general though, RFTM is the overall rule. Unless you know the circuit inside out, rules have exceptions. For that reason, I always use a dummy load on anything, based on the 'better safe than sorry' principle. Bear in mind though that a normal parts box resistor isn't enough. You need something with large power dissipation.

 

[Nopiano]

The manual is here:-
https://www.rega.co.uk/download/brio-manual-multilingual.pdf

There is protection against speakers shorting, so I’d be surprised if unplugged headphones would give it any problem. No harm in asking a Rega dealer - as I gather HQ prefer not to speak direct.

 

[bigfool1956]

People use SS integrated amps as pre-amps all the time with no issues. My AV amp has been running for years with the front two channels disconnected as the pre-out feeds the HT input of my Hegel for the fronts. Not an issue.

 

[uzzy]

The manual is here:-
https://www.rega.co.uk/download/brio-manual-multilingual.pdf

There is protection against speakers shorting, so I’d be surprised if unplugged headphones would give it any problem. No harm in asking a Rega dealer - as I gather HQ prefer not to speak direct.

This may be true of the Rega - but in any vintage SS amp this is not the case .. As I said above you can take the risk if you want but having seen so many amps go bang that were made in the 70s 80s and 90s just make sure before you try it.

 

[Strider]

This may be true of the Rega - but in any vintage SS amp this is not the case .. As I said above you can take the risk if you want but having seen so many amps go bang that were made in the 70s 80s and 90s just make sure before you try it.

Oopsie, I did that with an old Sansui amp and worse, a 1986 Mission Cyrus 1, my first piece of 'hi-fi'.. Took it back to the shop 'Westwood and Mason' in Oxford (best shop ever) and they just gave me another brand new amp and sent the fried one back.