To standby or not to standby...

DartmoorHedgehog

Thanks.

imalrightjack

@ICBM Based on the schematic and from what I know of other Engls which don't leak sound in standby, do you think my concern is legitimate (or am I a paranoid loon?)?

ecc83

DartmoorHedgehog said:

The HT series have solid-state gain circuitry in the preamp, at least on the drive channel, similar to a TubeScreamer pedal.  They also have a SS phase inverter (except possibly the HT100 which I believe has a valve PI).  So they are hybrids, even though there are valves in both preamp and power amp.  As mentioned above, Blackstar annoyed people with their marketing suggesting the HT series is "all valve".  (They sound good though IMO)

The other Blackstars (S1 and certainly Artisans) are properly all-valve AFAIK.

BTW @ICBM, which modern Oranges have dodgy standby?  Should I stop using standby on my RK30?

Nearly DH!

The Series ones use op amps in much the same way as the HT series, that is for clean gain and EQ. Almost all the "grit" comes from valves. The PI is quite complex. The two OOP signals are produce by an ECC83 but this drives an ECC82 (DO NOT USE ANYTHING ELSE!) to give a very low impedance drive to the output valves, a desirable thing in several ways.

The HT-60/100 also uses an 82 driver but the PI duty is covered by the MOSFET long tailed pair used throughout the HT range.

The Engl uses more transistors and opamps I think and the PI is quite crude IMHO  compared to the B'star being a simple bipolar transistor jobbie.

I also have to say that the FET PI has proved incredibly reliable.

The Artisans are, as you say, all glass! (the VERY underrated IMHO A100 does use a silicon bridge rect, a'fore anyone moans!)

Dave.

57Deluxe

my amps at home get at least 10 mins... not just for the tubes but so that the ambient air in and around the amp warms up and drives off any damp in the air...

DartmoorHedgehog

ecc83 said:

Nearly DH!

Ah, didn't know the S1 used op-amp gain as well.  Interesting about the PI as well.  I don't see the problem with using ss stuff (on its own or as a hybrid) in amps if the end result sounds good.  I had an HT20 until recently and I bought it because I liked it, not because of what it did or didn't have inside it (but I do sort of see the point people make about the "all valve" marketing - not having a go at you personally though, I know you aren't/weren't a marketing person).

Trying to keep somewhat on topic, whoever decided to build the standby switch on the HT20 into the input jack needs a kick up the arse.  

ChrisMusic

So can you over do standby ?

Is there any guidance on whether it's better to put it in standby, or to switch off ?

ecc83

DartmoorHedgehog said:

ecc83 said:

Nearly DH!

Ah, didn't know the S1 used op-amp gain as well.  Interesting about the PI as well.  I don't see the problem with using ss stuff (on its own or as a hybrid) in amps if the end result sounds good.  I had an HT20 until recently and I bought it because I liked it, not because of what it did or didn't have inside it (but I do sort of see the point people make about the "all valve" marketing - not having a go at you personally though, I know you aren't/weren't a marketing person).

Trying to keep somewhat on topic, whoever decided to build the standby switch on the HT20 into the input jack needs a kick up the arse.  

It isn't a standby switch! It is part of a protection gate system that biases off the OP valves unless you have a plug in both input and speaker jacks.

Whether the amplifier was ever intended to have a S/B switch and someone cocked up we will never know! BTW, the gating system grew out of the S1 design because the power control system did not allow of a simple HT switch.

Wadayawant a switch for anyway? Hardly any other electronic device in the history of electronics had one!

Dave.

DartmoorHedgehog

ecc83 said:

Wadayawant a switch for anyway? Hardly any other electronic device in the history of electronics had one!

If there is to be a standby mechanism (the necessity of which is debated I know) then I'd prefer it to be a separate switch rather than having to unplug the lead and find somewhere to dangle it.  I got into the habit of looping the lead through the handle then down to the socket so it could just hang down when unplugged, but a switch is more convenient IMO.

Whether there's any point in standby mode on guitar amps at all I don't really know - it's just that we're all conditioned into believing it will make the power valves last longer by treating them better.  Then we give them abuse anyway by running them so hot

Muting the output to save damaging the speakers with pops and spikes is probably a good idea, which is a side-effect of using standby, even if it doesn't really preserve the valves.

ICBM

I find a standby switch useful and I don't really like valve amps without them, even though they are not strictly 'necessary'.

I prefer to put the amp on standby and allow it to remain fully warmed up if I'm not playing for a few minutes, up to around a hour or so. Off/on heat cycles are not good for valves, or even some of the other parts. It's also very handy when troubleshooting.

I've also never found one good reason - other than the cost of the switch - *not* to fit one.

imalrightjack

It was suggested to me by a technician that standby switches are, "...glorified mute switches that are actually more likely to harm the amp when used in the 'traditional' way.  The idea of having to pre-warm the valves before applying the supply voltage is incorrect."

An interesting viewpoint!

ecc83

ICBM and I have come to agree to disagree about sb switches!

One reason for their existence has been mooted as indeed a "mute" switch in the dance band/jazz era when the guitarist, equipped with all of 4, maybe 8 watts needed to be totally silent for certain parts of a song but needed to instantly available for his 16 bars!

The old speakers of the day used light paper cones and would have been quite sensitive so a guitarist should for instance have been able to hold his own with at least say, a clarinet?

In any case, drummers then were much more refined people!

The S1/HT series still keep HT current running to the preamp/PI plus of course heaters and so everything is kept quite "warm"! IF of course you hold any truck with the "warmed up amp sounds better" philosophy? Personally I am yet to be convinced.

As for the lack of a switch on the 20? Heaven forfend anyone should innovate in the hidebound world of gitamps!

Dave.

ICBM

imalrightjack said:

It was suggested to me by a technician that standby switches are, "...glorified mute switches that are actually more likely to harm the amp when used in the 'traditional' way.  The idea of having to pre-warm the valves before applying the supply voltage is incorrect."

An interesting viewpoint!

And also partly wrong. They are not likely to harm the amp - or the valves - at least if they have been designed correctly. (Which excludes those amps where the designer forgot about the cap inrush current - which is not a fault of the concept itself.)

Yes, the standby is a glorified mute switch - but it's also a useful way of separating the HT from the LT (filaments and any other supplies, eg for solid-state parts) which is very handy for troubleshooting, including 'hot swapping' valves. It also definitely does improve valve life if the amp is going to be left unused for a while - particularly in amps where they are run over-hot at idle - while allowing you to leave the amp powered up to avoid hot/cold cycles. I also like the visual indication that the amp is still working!

So in my opinion they have several advantages, and no disadvantages other than the cost of the switch. (Again assuming they've been designed correctly.)

Some of the ways of doing them remove some of the advantages though - switching off only the second node of the HT (quite common) or breaking the cathode connection (like that Engl) does not allow safe or accurate troubleshooting or valve hot-swapping - and the ones which stress the rectifier valve are a nuisance... although these are full-HT types, so if you replace the rectifier with a solid-state one you solve the problem.

As usual, the devil is in the detail...