HT20 and the No Standby Switch thing...

Discussion - HT Venue amplifiers. Inspiration from Studio to Stage.
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VENTGtr
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Sat Jun 25, 2011 4:10 pm

Know the folks from BlackStar don't seem to post on here...but if anyone has any thoughts, was wondering; Why is the HT20 the only one without a StandBy switch?

HT5 has one, HT40 does, all others seem to. Only the HT20 uses the input jack, which...to be honest, may be fine...but I'm not used to it...and like having that toggle there.

Might be one of those "We'll never know"s, but seems strange.

Ya...Saturday morning...putting off getting to things...so posing inquiries...

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majikmojo
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Sat Jun 25, 2011 11:46 pm

the real question should be why do guitar amps have standby's at all...

Standby switch: The standby switch usually allows the HT to be turned off while the heater and bias supplies are always on. Contrary to popular belief, the standby switch is not there to prolong valve life-span. The theory is that if the HT is applied while the cathodes are cold they will be 'stripped' by ions crashing into the unprotected cathode. However, this simply does not happen. It is an urban myth borrowed from transmitter and cathode-ray tube technology NOT ordinary 'receiving' valves. The only valve which might ever be at risk of failure is a rectifier valve, because it has to supply inrush current to the reservoir capacitor, and some guitar amps fail to use enough limiting resistance to protect against this (see more on rectifies).
On the other hand, leaving a cathode hot without any anode current flowing does lead to the very real effect of cathode poisoning, which reduces the gain (transconductance) of valves. Fortunately this phenomenon really only becomes significant if the valves are left on standby for hours on end.
If you're wondering why all those old amps use a standby switch, its because Fender was designing complicated amps on the cheap. In the bigger versions of the Bassman, money was saved by using power supply caps that were rated only for the working voltage, not the peak voltage which occurred before that valves start drawing current. As everyone knows, Marshall simply copied the Bassman without a second thought, complete with standby switch, so now we have the two biggest names in the industry using standby switches, and the rest is history. The other big players, Vox and Gibson, never used standby switches since they didn't need them. Only very recently have they started adding them, purely because too many guitarists want their amp to look just like a Fender/Marshall, even though nowadays no designer (who values his reputation) uses underrated capacitors. But the average amp tech doesn't know this.
Note that even the RCA Transmitting Tubes Technical Manual No. 4, p65, states: “Voltage should not be applied to the plates or anodes of vacuum, mercury-vapor, or inert-gas rectifier tubes (except receiving types) until the filaments or cathodes have reached normal operating temperature.” [My italics]. In a properly designed amp, a standby switch is nothing more than an expensive, oversized mute switch.

from "Merlin Blencowe" book of amp design

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VENTGtr
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Sun Jun 26, 2011 2:45 am


A VERY sound and well-stated explanation.

So...then...why do you think this is the only model BS has decided shouldn't have an external Standby? And, have you torn an HT20 apart to see if the "standby" that occurs when there's no jack plugged in actually does anything?

Just really seems odd.

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majikmojo
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Sun Jun 26, 2011 11:44 am

vent - i could only speculate as to why that is - we will prolly never know unless blackstar tells us :lol:

cost cutting? maybe but i kinda doubt it
amp is such low wattage they didnt feel a switched stand by was justified?? - doesnt explain why its on the 5's
one of the first models designed and perhaps the input standby was going to be on all amps until they realized that players wanted a switch?? - maybe

i really could only guess as to their reasons - i once read somewhere that all the venues series amps have the input standby feature even
if equipped with the switch - but i would have to find that again to confirm the source

like you - i prefer the switch just because its there and i hear and feel the activation - not much of a reason really :lol: - but its what i prefer

there is a lot of misunderstanding about what standby switches do and what they are for and it wasnt until i educated myself that
i was able to weed out the myths from the facts


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VENTGtr
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Sun Jun 26, 2011 4:03 pm


Well, if nothing else, your explanation on the Standby was worth posing the question. Appreciated.

Interesting info to have. Also explains, as you mentioned, but old Gibs and Voxs didn't have them.

Have always liked Gibson's amps.

Redi'zain
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Sun Jun 26, 2011 11:57 pm

It does, when you take your lead out of the input it puts it in standby. Insert a lead and then it's on.

I watched a video review with a Blackstar guy explaining it. Pretty pointless in my opinion and most people won't take the lead out at home. Probably doesn't matter.

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majikmojo
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Mon Jun 27, 2011 12:08 pm

redi - good to know...i dont see the point either

dtjesus
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Thu May 09, 2019 6:50 pm

This whole "soft standby" is infact a huge problem on its own. My HT-20 went into standby and no matter what i try, has not come out of that stage. No response from Blackstar on the issue. Think i will have to open the amp up and bypass the entire soft standby circuit, hopefully without destroying the rest of the amp. I had not idea Blackstar was stupid enough to put that in one of the models. If i had known in advance that there was no proper standby switch, I would have certainly gone for HT-40.

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