Mark IV Why is load necessary when using Silent Recording

[dkiss4ck]

The MkIV Manual makes it clear that the speaker or a dummy load should be connected when using the amp with the silent redorcing pull switch in the out position.

I'd guess that the speaker is still in circuit somehow but as there's no audible signal what is it actually doing ?

If I have to use a dummy load would its design significantly affect the tone appearing at the record out ?

Are any recommended other than the DIY route ? (I've noticed Webers) simple and compact would be best.

The amp is probably late 80s - UK 240V features not quite as in my manual (no ground switch , no stereo etc)

Thanks
Dave

 

[zebpedersen]

As far as I'm aware you don't need a load when using silent recording - however I'd leave it in there just to be on the safe side. Don't have the manuals in front of me but I swear that's what it said in the Subway Rocket manual (and the IV as well?)

 

[hugsy41]

Even though there is no audio signal going to the speaker, it is, as you say, still part of the circuit. There is still a voltage signal (correct me if I am wrong) being sent to the speaker. The reason why you don't hear anything though is because the speaker reacts to the audio signal which is superimposed on this voltage signal. Without this, the speaker will not make a sound.

Therefore, the pull mute function does not mute the signal to the speaker, rather re-route the audio signal out the silent recording jack. It is imperative that the speaker (load) be connected as the transformer is still outputting voltage, and needs a load to prevent there being an open circuit. Otherwise, similar things will happen just as if you left the speaker load off while trying to play the amp normally.

Once again, anyone, correct me if I am wrong. I am in early stages of learning about electronics, and this is my fundamental understanding of this idea.


Hope this helps!

 

[straitouttahell]

Even though there is no audio signal going to the speaker, it is, as you say, still part of the circuit. There is still a voltage signal (correct me if I am wrong) being sent to the speaker.

For what I can tell looking at the schematics, you're partially right.

When you pull-silent the main volume knob, you are basically grounding the poweramp input, sending all the audio signal from the EQ output (preamp's very last section) to the speakersim circuit only.
By doing so, theoretically there should not be any voltage sent to the speaker. Apart from the sound signal, all other voltages are DC and should not couple through the output transformer to the speaker. However, this is theory, in practice the poweramp is still fully on and capable of amplification, so it is not a bad idea to leave a load connected to the OT just in case something weird happens. That's how I read that precaution. Please, correct me if I am wrong.

 

[straitouttahell]

The MkIV Manual makes it clear that the speaker or a dummy load should be connected when using the amp with the silent redorcing pull switch in the out position.
I'd guess that the speaker is still in circuit somehow but as there's no audible signal what is it actually doing ?

Protecting your OT from blowing in case something goes wrong.

If I have to use a dummy load would its design significantly affect the tone appearing at the record out ?

No, it shouldn't.

Are any recommended other than the DIY route ? (I've noticed Webers) simple and compact would be best.

This:

http://www.mcmelectronics.com/product/28-048

should do.

 

[MrMarkIII]

"...The MkIV Manual makes it clear that the speaker or a dummy load should be connected when using the amp with the silent recording pull switch in the out position..."

Because you will forget to plug the speaker back in and blow your OT.
This is a no-brainer. Why would you need to unplug the speaker if there's nothing coming out of it anyway??

 

[straitouttahell]

Because you will forget to plug the speaker back in and blow your OT.

Or you may inadvertently hit the main volume and re-engage the poweramp.

 

[dkiss4ck]

Thanks for all these answers I think I'm fairly clear with this.
So the load or speaker is basically a safety precaution and not normally part of the circuit in silent-recording config if all is well.
I might not have the cab if recording from a head only so the protecive load should be ideal
Dave

 

[emperor_black]

A load should be connected to the amp at all times! Never unplug the speaker unless your amp is in standby.

I recently toyed with the recording out and its very feeble, but I do hear sound from my 4x12's speakers. Its there, but very very little.

 

[chris_EIT]

Yes, I use the recording out fairly often to connect to ab impulses when I can't be loud at home. There is definitely some signal still going through to the cab despite how low it is! I would never run my mark iv without a load just in case. To precious to test!!! haha

 

[av8or3]

Always load the amp (transformer) Period!
If you don't you will ruin it.
Jim