beginner forum: for novice and developing blues harp players > Turning tube amps on and off.
Turning tube amps on and off.
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bublnsqueak
137 posts
Nov 24, 2019
12:04 PM
As part of my GAS journey I have modified a couple on smaller tube amps for harp (Peavey ValveKing Royal 8 & VHT Special 6 head)
I genuinely have no idea what I'm doing but Alnicomagnet's kits and instructions are very good.
Both of these amps have Standby switches. I understand that one of the reasons for this is to protect the valves from repeated heating and cooling which, I guess, is not good for them.
Over a typical weekend I might get 5 or 6 short practice sessions in. I have started leaving the amp I am using on Standby all weekend.
Is this less bad for the valves? Or would you turn it off overnight?
SuperBee
6317 posts
Nov 24, 2019
12:32 PM
I’d turn it off.
Standby leaves the heaters running. So the amp is ready to go and there’s no surge in the power supply.
I have seen arguments against installation of standby circuits in small amps and against the common use of them to keep the amp warm between use times. Eg a person might switch their amp to standby between sets. I read that was not a worthwhile practice and one may be better to just leave the amp ‘on’.
I’ve adopted the approach that standby is only something to observe on power up and power down. Several of my amps are somewhat ancient and do not have a standby. My old ampeg Jet has been surviving without standby since 1962. My Kreisler radio has had no standby since 1964. My filmosound amp has no standby since 1948.
My homemade 5F1 champ, my vibrochamp xd, one of my valve jr amps: no standby.

I did install standby in my other valve jr, and my lone wolf se6L6.

I used the Kreisler all day yesterday and just left it on.
SuperBee
6319 posts
Nov 24, 2019
3:59 PM
Bubblnsqueak, have a look at valvewizard.co.uk.
A very good site generally for understanding what’s really going on with tubes. Specifically in relation to this issue though I think you’ll find the power and standby switches article of interest. It’s under the ‘power supply’ topic heading
bublnsqueak
139 posts
Nov 24, 2019
10:25 PM
Woah! I was thinking of simple metal fatigue from repeated thermal shocks.

A really credible article that reveals that I seem to have fallen for yet another old wives tale. MTG will be pleased that this one has been outed.

It's a mute then.
Thanks SuperBee
SuperBee
6320 posts
Nov 24, 2019
10:32 PM
The upshot of this seems to me that leaving the amp on standby is more likely to reduce tube life. It’s probably the worst thing to do.

Most electronics advice I can find is along these lines. Guitar magazines and even some amp sites seem to push for standby use. I read a really poor article on Carvin website today, which was misleading on a number of fronts.
Christian Wasmer
20 posts
Nov 25, 2019
1:43 AM
I am a tube amp service man, and I built some as well. I must admit that the valvewizard article just says everything I wanted to say about this matter ! I have repaired and modified numbers of these VOC AC30CC where the standby switch literally kills the rectifier tube ! So I mod this switch into a mute switch (connects input jack "hot" to ground).
bublnsqueak
141 posts
Nov 25, 2019
3:42 PM
Thanks for your input.

After your comments I posed the question to Nigel (Alnicomagnet) just to get a steer on my particular equipment. His reply below:

Hi Paul

The only reason I sell standby switch kits is because people asked me for them in the past. I just supplied what the market demanded.

No valve amp needs a standby switch. Valve amps fitted with valve recifiers should never have standby switches fitted, and if they are, they should never be used. Example: A customer's Marshall Bluesbreaker, using the standby switch killed a brand new GZ34 rectifier valve, and nearly took out the mains transformer HT secondary winding.

I don't like the arrangement on the VHT Special 6. I would replace it with a simple two position switch for pentode/triode. Also, the way the HT circuit is configured means that the first filter capacitor can be charged up over 400VDC if left in standby.

Cheers

Nigel

In future I'll just turn it off then!
SuperBee
6325 posts
Nov 25, 2019
6:31 PM
Thanks for raising the topic.
i've been in the habit of using the standby on my amps which have them, to power up and power down, but since revisiting the topic i think it seems unnecessary to even do that.


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