sound comes back for a moment after standby turned off

[rp]

What about a Semiconductor Diode. I wired my standby between the first node and the HV so there is nothing on the caps when in Standby Mode. It seems as though this will result in a max inrush but that's not supposed to be an issue with semiconductors? Silverfox.

If you have an HT fuse, which should be a fast blow, using the standby seems to stress them and they often pop, especially true with ss rectifiers. This is annoying as you don't really know if there's a real or developing fault. I'm not sure how Marshalls with internal fuses and SS rectifiers handle the annoyance issue, maybe they use a slow-blow? That's often been my solution though it's lame, plus of course putting the switch btwn the first two nodes, and I put a resistor across it.

Is there a reason you don't often see a STBY to interrupt the low voltage, say into the PI? I guess you'd still hear some hiss and it wouldn't sell well as a real mute? Plus the risk of oscillation running the extra wiring?

You guys against a standby still recommend this in a ss rectified amp? Seems harsh to just hit a stone cold PS with full power.

[Merlinb]

Anything that can be done to alleviate this?

I woudl guess that if you force the bias supply to collapse much more slowly than the HT, it will stop the volume pumping effect. One way to do this would be to insert a diode and resistor into the bias supply (R3 and D1). Make R3 pretty large, say 470k. C2 is then prevented from discharging quickly at switch off.

[img:458:214]http://www.valvewizard.co.uk/bias_adj1.jpg[/img]

[pdf64]

Might that arrangement result in the amp's output stage suseptibility to blocking distortion / bias recovery following overdrive, being worsened?

Is there a reason you don't often see a STBY to interrupt the low voltage, say into the PI? I guess you'd still hear some hiss and it wouldn't sell well as a real mute? Plus the risk of oscillation running the extra wiring?

If a switch with mute function is the objective, standby seems a remarkably convoluted and problematic way of achieving it.

I think that Carol Ann Amps just label a mute switch as 'standby' http://www.carolannamps.com/ in order to fulfil their customer's expection.

You guys against a standby still recommend this in a ss rectified amp? Seems harsh to just hit a stone cold PS with full power

Yes, standby (in its traditional implementation) seems a bizarre function to deem desirable. As noted, it acts as a constraint on fusing arrangements etc.

As for the stress of power up without standby being harsh, if that's a concern then NTC thermistors to limit surge currents may be a good option. They could be used in both the primary and / or B+ winding circuits, as I've not noticed a voltage limit in the data sheets.

See Merlin's page on the topic http://www.valvewizard.co.uk/standby.html

As that raises solutions to reduce tube wear but without muting, how about moving the discussion to implementation options for a mute switch?

[rp]

how about moving the discussion to implementation options for a mute switch?

I'm all ears (eyes?). I think it would be hard to sell an amp w/o a stby, people just expect it and use it all the time on breaks. My next two amps will be w/o but they're built for me.

BTW for home brewing where a few extra bucks don't matter much, and to satisfy our fetish to over-build, there are options like this from hifi-land, soft starts circuits either on the wall side, filaments, or on the B+. If I ever build a ss rectified amp I might put out one in, though it's just more stuff to fail, troubleshoot, add heat, and my biggest concern add noise/hash/hardness.

Any thoughts on these things? Needless complexity? KISS?

http://www.partsconnexion.com/DEXA-72558.html
http://www.newclassd.com/index.php?page=80

http://www.ebay.com/itm/220V-240V-AC-20 ... 1560862825

http://nervenet.info/HT_delay/

http://koti.mbnet.fi/siliconf/JukkaTolo ... ml#HD_NM_8

[pdf64]

A mute switch could be achieved by shorting the power tube control grids together, prior to the grid stoppers.
Or as per some Selmers, drop the B+ supply from the LTP, though that may cause a 'thump' when operated, as the coupling caps charge up http://bmamps.com/Schematics/Selmer/sel ... csv50w.pdf

Those soft start things seem way over the top to me; NTC thermistors http://uk.rs-online.com/web/p/thermistors/2161400/ seem to be a preferred option for Fender and Peavey, eg http://support.fender.com/schematics/gu ... ematic.pdf

[Gaz]

A mute switch could be achieved by shorting the power tube control grids together, prior to the grid stoppers.
Or as per some Selmers, drop the B+ supply from the LTP, though that may cause a 'thump' when operated, as the coupling caps charge up http://bmamps.com/Schematics/Selmer/sel ... csv50w.pdf

Those soft start things seem way over the top to me; NTC thermistors http://uk.rs-online.com/web/p/thermistors/2161400/ seem to be a preferred option for Fender and Peavey, eg http://support.fender.com/schematics/gu ... ematic.pdf

I always thought shorting the Power tubes grids together seemed like the easiest to implement late in the chain, but the potential problem is extending the grid wires a lot, and presumably right next to the noisy power switch. Not sure if this would pick up an AC noise in practice.

Kevin O'Connor suggests cutting off the screen supply as another alternative (however he agrees with Merlin to avoid it altogether or use a mute switch).

[Reeltarded]

Either I am being stupid or obvious.. not playing while the amp drains works just as good as anything else.

I dunno

[sepulchre]

Okay, I've wondered about this for some time. Merlin's fix looks good to me but I have not seen it in Marshall schematics, at least not in those I'm familiar with.
I have a JMP2204 (borrowed) and my own sort of replica ala Jana(ish) of the same. The differences are not in the PA section. When I turn the Marshall off, it's off - no more sound. But with mine, though the Standby has been off for plenty of time, when the Main power is turned off there is sound until the caps discharge. Of course Reel's solution - don't play - works great. I'm just curious about how and why this happens.

[Reeltarded]

I actually hit the switch and a big G chord then I turn the master up full. That drains fastest.

[sepulchre]

I'll give G a try. I've been using a full B9th with the low F# to make it fat.

I'm just curious why one amp does and another doesn't. Maybe it's just that bottle of Merlot talking but still . . .

[rp]

NTC thermistors http://uk.rs-online.com/web/p/thermistors/2161400/

First I've heard of this. All I have to do is put one of these in the mains return and I have a ramp up?! Seems too cheap and easy, but must be adequate and reliable if Fender and Peavy use this. Next parts order I will add some, in fact I will check today with the old school electronics shop we still have in town.

Any down side? Why isn't using a thermistor more popular with the DIY crowd, those that fetish over their rare expensive NOS tubes?

[Reeltarded]

Downside: thermistors go bad and the amp won't work. I cut them out and replace it with a wire.

This follows with my "no tube rectifiers" philosophy. It's actually a science. A theory of failures. E.pissedoff.emology.

[rp]

Downside: thermistors go bad and the amp won't work. I cut them out and replace it with a wire. This follows with my "no tube rectifiers" philosophy. It's actually a science. A theory of failures. E.pissedoff.emology.

I thought the new rectifier tubes had gotten better, guess not. Myself, I've never had a tube rectifier fail, but mine are all NOS. Even if new production I can't see them being any more prone to failure than new power tubes, but then one less new tube is one less problem, can't argue with that.

I've been googling about those surge prevention thermistors, most posts if not all are about replacing failed ones, apparently they can even vaporize into oblivion. I just figured if peavey and Fender who have to pay for warranty and deal with customer aggravation/bad vibes used them they must be reliable, why look for trouble??? Maybe someone ought to invent a thermistor that can fit into a standard chassis mount 3AG fuse holder for easy swap

When I build my EL34 Marshall it will have a standby and I'll heat the filaments up first like Leo and Jim intended.

[stretch2011]

I Havnt read through all the pages so I don't k ow if this will help you or will apply to your application.
I had a 5e3 with some signal bleeding through after I switched on standby. I rewired the high voltage to be cut off by the standby switch and it cured it.