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Comments
Rift Amplification
Brackley, Northamptonshire
www.riftamps.co.uk
Standby switches aren't necessary, but they are useful and there's no reason to stop using it - the DRRI has the switch in the correct place so it doesn't stress the rectifier valve, unlike many modern amps.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I don't understand the opposition to them. They can be useful, and (unless fitted in the wrong place!) do no harm. Some amp makers go so far as to fit a standby switch which is nothing more than a glorified mute switch - in my opinion this is silly and dangerous. If you fit a switch, have it do the right job and turn off the HT. If you don't want to do that, don't fit a switch at all.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
The reason it will thump is because it's in the correct place for a valve-rectified amp - after the first filter cap. This means that when it's switched on, that cap then supplies a big rush of current to the other caps. This is a good thing, because it means the rectifier valve doesn't have to, so it avoids stressing it - unlike amps which have the standby upstream of the first filter cap.
In amps with a solid-state rectifier it can safely be upstream of the first filter cap, since a solid-state rectifier doesn't mind supplying the current surge.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
ICBM and I have "agreed to differ" about this for a long time. Regardless of the harm to valves (if wrongly implemented and really only to those crap things VALVE rectifiers) the "danger to personal" is to me a red fish.
If you are an experienced electronics technician* you will EXPECT everything to be live (all guns are loaded) . The Guitar Amplifier with an HT SBS is an anomaly in the electronics world. NO other equipment has such a switch. Valve hi fi amps never did/do. TVs with 5,000V focus volts ('king HURTS I thell thee!) didn't. Microwave ovens, 3kV, 2 amps+ NO prisoners! are either live or not.
*If you are NOT so experience keep TF out of there or be very careful and stick to simple bias setting with a cold amp and croc clips. And DO stay away from naked mWave ovens!
There is/was a bit of kit with an SB switch. Radio TX sets but these had an expensive TX valve that that pulled a lot of power and the HT was 'blobbed on to talk', also there were portable valve TX sets and obviously conservation of battery power was vital.
Dave.
Anyway we can agree to disagree on this, but I expect you will always check what comes across your bench before assuming how a switch is wired up
I don't have an issue with not fitting standby switches, nor even with switches that are actually marked 'mute' or something, but if a 'standby' switch is fitted then it should turn off the HT. I don't even like the typical Peavey way of using it to turn off the screen supply, since it still leaves high voltages present on the valve sockets.
Yes, it's arguable that if you don't know what you're doing you shouldn't be in the amp at all, but it's a fact that this does not always apply.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Makes you wonder why Neutrik don't use 2 different sized spade terminals on their powercon sockets to prevent this happening and it also proves a PAT test is a waste of time to a certain extent
IC, you can only go so far in protecting idiots. When have you ever seen a warning inside a car bonnet that said "Don't put hand on fan belt it will rip your arm off"?
All mains electrical gear is dangerous to some extent and valve amps more than most. Then almost all amp mnfcrts fit a warning label "Warning High Voltages. No user serviceable Parts inside" I know 'we' certainly do as well as a very plain warning on the amps that need it about the unusual standby arrangements.
Dave.
So why bother sleeving the mains connections?
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Yay!
That thought leapt out at me while reading Dave's post, but I resisted.
A bit like when you use you phone to make a phone call, you does not matter if it is analog/digital with a cable/satellite/wifi, you are still making a phone call regardless of technology.
Your point about servicing is valid, however I build loads of amps without standby switches and don't really have an issue pulling HT fuses if I have to.
I have obviously missed a lively discussion somewhere, I assume we all know why some manufactures really fit sleeving on mains connections...
Because it looks neater, shows somebody 'cares' and also, certain magazine reviewers (not of guitar amps) expect such attention to detail and make a point to mention it when it is not done!
There IS a lot in a valve amp chassis we CAN'T make foolproof but surely we should DO what we CAN do? Naturally 'fools' should not be in there and we attempt to tell them that!
I think it is a bit of a cheap shot when NOBODY has come up with a reason why Quad lls , Radford 25s and the lovely little Rogers 10x10 amp I had stolen had no standby switches?
Oh! And just to be fair, there is ONE class of amp that had an SBS. Some V old PA amps and this was because they could often be used in a field on a rotary converter fed from a lorry battery so the heaters were kept on but a bit of juice saved by shutting of HT. But these were pretty rare beast even then !
Dave.