More standby switch confusion

RandallFlagg

Should you switch an amp on with the standby switch engaged for a minute before switching out of standby and playing?

The Victory V40 manual states that you should but the Morgan PR12 manual states the opposite:

Victory V40:

HIGH – STANDBY – LOW Switch The V40 should always be switched on, (mains switch on rear of amplifier), with this front panel toggle switch in its centre position. The amplifier is now in ‘STANDBY’ mode with just the valve heaters and low voltages on. This allows the valves to heat up before they get 100s of volts up them, (it’s less of a shock). After around 60 seconds, the amp can be switch to either HIGH, (around 42watts rms) or LOW, (around 9 Watts rms)

Morgan PR12:

POWER SWITCH: Turn this ON to power the amplifier. Turn on this switch and the standby switch at the same time for optimal tube life.

 Are they both right due to different circuits or is one of them wrong? The Morgan has a valve rectifier and the Victory is solid state. Not that I even know what a rectifier does!

clarkefan

Not going to be much help but if you search TGP on this the guy who makes Carol - Ann amps swears blind it's better to just leave the standby switch permanently on and don't use it, that they shouldn't be on guitar amps cos they cause rather than prevent damage to the valves, and that he only includes them on his amps cos otherwise people wouldn't buy them.  

Oh yeah, and on some of his amps he bypasses them so they do nothing anyway.

I know shit so hopefully some experts will get back to you, but yeah worth a read

ecc83

The real danger of the SB switch is to valve rectifiers and only then if it is wired in a particular way.

Some amp techs like them as they have certain 'operational' advantages but I came to gitamps late (58) and cut teeth on live chassis and microwave ovens take NO prisoners!

Unless you have a specific need, and the only one I can think of is to mute the amp, in the dark where you can't see the controls e.g. orchestra pit during a DBO, leave it on, Gaffer tape it down then drive a 6 inch nail either side of the tape.

Dave.

professorben

Ok here is one for you @ecc83  @ICBM @RiftAmps  etc. 

I have a Mesa Studio Preamp with a standby switch. 

Is it worth using? As it's only a Preamp etc. 

Sorry to derail thread. 

ICBM

It doesn't really matter either way, although with amps with a valve rectifier and the switch in the wrong place then it can stress the valve to use it.

I still prefer amps to have them than not - they can be useful for troubleshooting, cab swapping etc - but they do need to be designed properly.

Fitting one that doesn't do anything is stupid and could lead to damage or injury if someone assumes it turns the HT off when it doesn't.

ecc83

"Fitting one that doesn't do anything is stupid and could lead to damage or injury if someone assumes it turns the HT off when it doesn't."

Yeah! Did not think of that IC! 'We' slap a big, black warning label on the S1's. Re cab swapping. Virtually all B's amps gate off the OP valves if the speaker jack is pulled. They also have a certain amount (NOT perfect!) of 'no load' protection and whilst 'cold swapping' is the preferred practice, just turning the master V to zero is fine..AS easy as flipping a switch!

Luuuuvre to not fit them but as mentioned, peeps expect them. There was quite a hew and cry when they chose not to (forgot?) to fit one to the HT-20!

Dave.

ICBM

ecc83 said:

"Fitting one that doesn't do anything is stupid and could lead to damage or injury if someone assumes it turns the HT off when it doesn't."

Yeah! Did not think of that IC! 'We' slap a big, black warning label on the S1's. Re cab swapping. Virtually all B's amps gate off the OP valves if the speaker jack is pulled. They also have a certain amount (NOT perfect!) of 'no load' protection and whilst 'cold swapping' is the preferred practice, just turning the master V to zero is fine..

Not always with other amps. There are a (very, admittedly) few amps which are unstable with no load and no signal and will self-oscillate, even if the MV is right down. The Mesa Dual Rectifier when set to Modern mode (which turns off the NFB) and the old Vox AC50 (which doesn't have any on the first place) are two I know of, there may be others.

You could also say these amps are badly designed and should either have a shorting switch in the speaker jack or a safety resistor across the output, though… and you'd be right! Selmer T'n'B 50s have a 600R resistor there, presumably for that reason - but also probably need it because they have a very poor standby switch arrangement that just turns off the HT to the phase inverter. When I work on these I always rewire them so it's a proper full HT switch.

bacchanalian

I have a Victoria Regal II which runs like two Class A amps.  Victoria say that Class A amps do not like idle and should put on standby anytime it is not in active use. It is valve rectified.  Is standby different for class A?  

ICBM

bacchanalian said:

I have a Victoria Regal II which runs like two Class A amps.  Victoria say that Class A amps do not like idle and should put on standby anytime it is not in active use. It is valve rectified.  Is standby different for class A?  

No.

It's just that they're confusing 'cathode bias running the valves way too hot at idle so any operating time at all is shortening the life of the valves' with 'Class A'.

I would take a bet that the amp is not Class A, like almost all "Class A" guitar amps.

bacchanalian

@ICBM ;
"I would take a bet that the amp is not Class A, like almost all "Class A" guitar amps."
Could you expand on that point? They describe it as Single ended Class A.  I bought for the tube swapping and did not consider what Class A meant.  
Thank you in advance

ICBM

Forget the whole Class A thing - it's used as marketing guff to make an amp seem more desirable. It's pretty meaningless when applied to guitar amps for two very important reasons -

It only applies to push-pull amps.

It only applies to *undistorted* signals.

Class A simply means that all the output devices conduct for all of the waveform cycle at the maximum undistorted power output. It only really applies to push-pull because that's the only case where you can have other classes, hence the definition is essentially meaningless for single-ended, which is more properly called 'single ended' .

In any case, most single-ended guitar amps are biased so much too hot that they couldn't even really be considered Class A by the full-waveform test, because they reach forward clipping before cutoff.

And in any case, as soon as the amp is overdriven then the class definitions are entirely meaningless.

Single-ended has a unique sound.
Push-pull cathode-biased has a unique sound.
Amps with no negative feedback (also sometimes claimed as a feature of Class A) have a unique sound.

None of them are inherently Class A - they *can* be, sometimes. You can also have a fixed-bias, push-pull amp with negative feedback that *is* Class A, if you want...

bacchanalian

Thanks @ICBM.
Wis'd that.