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Discussion in 'The Workbench' started by dslman, Jun 5, 2020.
Funny there are so many varying opinions.
A standby switch are only needed when the rectifier bridge is semiconductor diodes. An amp using a tube as the rectifier do not need a standby switch. The idea is that the tube rectifier does not switch on straight away do the other tubs heats up.
Standby switches are redundant i think. I built two 50W 2204's with no standby switch. Only one i built with standby was the tweed deluxe. Reaon being i did not know much back then and was building from kits. But now i would not put in the standby.
The usual standby method harms valves, it does not help preserve them. It generates cathode poisoning which creates a build up of interface resistance in the cathode which kills the valve. I know most won't believe this but you can never buck the Physics...
http://www.valvewizard.co.uk/standby.html Second section.
So why do they still put them in? Because guitarists know better than engineers that there is no problem with them, it's all just made up stuff, and that they can't play without having one. The idea of turning the MV down to 0 is not an option. Apparently.
"Heck, I even turn my electric oven on by going from 0 through 10 rather than just clicking straight to 10."
Just to be a technical ted, it's the other way around for a standby switch. In an oven you start at 1 because that's the lowest current, then you build up more current as you go to 10.
With a standby switch the turn-on is 'softest' when you don't use it, because the valves takes ages to warm up and start conducting. The current builds up gradually.
But when you preheat them, and then switch on, you slam everything in the amp with maximum current in one hit.
"Why do smaller tube amps not have a standby switch?"
A better question is why do any guitar amps have standby switches? Remember, 99.9% of all valve equipment ever made was not guitar amps, and they didn't need or use standby switches...
Amp manufacturers exist to sell amps. When guitarists keep demanding standby switches because they saw it on that-one-amp-that-is-famous-because-a-famous-guy-used-it, then the manufacturer will keep giving you standby switches. They don't care if it makes the valves last longer or not, heck if it doesn't, even better, you'll buy more branded valves and thank them for the opportunity.
Hahaha! Merlin? Is that the same Merlin who I have just linked to in the previous post presumably while you were typing?
I would make sure to have anti-arcing protection on V2 though (the cathode follower), since the 2nd grid will rise to almost full B+ before the valves warm up (no current being drawn = no voltage dropped on dropping and plate resistors).
It can ruin a gig, it happened to me.
It's just a diode and a resistor, it prevents the grid from going too far above the cathode by shunting the voltage straight to the cathode. During warmup grid will now be at roughly half B+ but so will be the cathode.
More info: http://www.valvewizard.co.uk/dccf.html
Using the Standby switch to mute an amp is like stopping your car by putting on Park
I have a Friedman pt20 and it has a solid state rectifier and no standby. I'm pretty sure Dave Friedman knows what he's doing and as far as putting your amp on standby at gigs during break, not good for the tubes. Common sense should tell you that. People think standby is good because leo fender used it but it's actually not necessary. Do the research and you will concur. It's more of a luxury than a necessity and that's about the best way I can put it.
Duly noted, actioned and incorporated in to my amp-life (you just taught an old dog a new trick)
I just bookmarked that site - full of very interesting tubelicious information...
I thought i read in a previous post on this forum that some amps without standby switch was in the jack
If you turn the amp on and nothing is plugged into the input its on standby, soon as you plug in a cable it comes off standby?
I had the DSL15H and thats what i thought i read about that one?
Or did i read it wrong?
I beg to differ.
A. My VoX AC30is class A cathode bias and has a standby switch
I beg to differ
A. My Vox AC3O is class A cathode bias and has a standby switch.
B. Fender Princeton, blackface and later, reverb or no, are class a/b fixed bias and have no standby switch.
I can't speak for Freidman but over the decades it's become apparent that they simply cut down on features on small amps. The Deluxe Reverb is the smallest to get not only the standby switch, but the bias control and second channel.
So no, I don't think the class and bias type matters. It's about money.
Depends how you define a standby switch.
The classic standalone switch interrupts the high voltage to the tube plates. A by product of that is that the amp is muted.
Input jacks are typically shunting. Meaning with nothing plugged in the input is grounded. A byproduct of that is that the amp is muted.
So unplugging the cable will mute the amp, but high voltage is still delivered to the plates. It's not technically on standby.
I get nervous when I hear all this Cathode grid-bias tube-shunting 12AXL Diodiuos language.
Now I won't know whether to switch my Standby on first, then power switch - or both at the same time - or in a L/R/LL combination, with 5 second intervals, standing on a rubber block to insulate myself from cathode poisoning, while wearing a Covid mask.
I just want my amps to sound and behave like tube amps
Standby switch...I do a quick sequence...power - then standby ...then listen. If anything that isn't catastrophic pops at power on or B+ on...then I can typically hear the issue as tube conduction starts...and, I can squelch the potentially excessive audio (and voltage/current-related issues) as the tubes are just starting to produce a live audio path. So...I use Standby only to save my ears when startup issues may prevail. I'll back it off to power down in the same reverse manner.
Same reason Merlin gave...I don't like slamming full B+ only fully conducting tubes.
I use Standby when powering up, to allow the low voltage side of the tubes to warm up before hitting them with the high voltage that's controlled by the Standby switch.
However, when powering down I avoid Standby to allow the caps to dissipate and discharge. I consider this a critical safety step if I'm getting ready to rebias the amp.
Bill M had a great article on this, and I replicated his "proof" with a DMM, which proved he was dead on the mark. With Standby on when powering down, the caps retain high voltages. With Standby off, the caps dissipate their energy to ground in seconds. You can watch this on a multi-meter as its happening.
Marshall 200! NO standby switch!!! Standby switch is for wimps!
Standby is an easy and convenient way to mute an amp, that's why it was originally put on amps. SnickSound has it absolutely correct in his earlier post.
For myself and maybe others, when I started using 100w stacks in the 60's it was the days of turn it up all the way all the time. If you have ever used a 100 w Marshall on 10 you know the hi gain hiss that eminates from it when you are not playing. So I used the standby just to shut off the noise during breaks as this was simpler than turning the volume down and anyway, there was a standby switch so use it. Back then parts were cheap as were tubes so this subject never came up back then. These days tho it seems as its better for the whole amp if you dont use it unless you have to. So now I will just keep the gain down until i'm ready to play and then set the amp and leave it up till done. Able to have a kill switch on the tuner that shuts down the hum and hiss..Having owned a recording studio one of the first things you learn is to never turn off the board as the shunting from on/off increases the chances of a failure in the positions..
that must've been fun.