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    Add Standby to ST120?

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    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Add Standby to ST120?

    Post by sKiZo on Wed Nov 27, 2013 2:36 am


    Reason I ask ... Usual routine is to turn the amp on early afternoon for a listening session, then it'll sit until late evening before I spin another disk. Eight hours is too long probably to just leave it on, but maybe not long enough to turn it off and then back on again? In a perfect world, I could just have the heaters idling away so it's ready to go and doesn't have to go thru an unnecessary hot/cold cycle.

    Seems like it'd be simple enough to mod a TDR board to use a manual switch instead of tripping automatically after a time delay ... or better yet ... both? In a perfect world, the TDR would work as intended to soft start the amp automatically, but I could manually switch to standby between sessions, then just turn the amp off at the end of the day.

    I also found this ...

    http://www.singlecoil.com/docs/standby.pdf

    That circuit uses one DPDT to allow either just the AC heater circuits or full power to the amp. I've done similar with ham amps and radios ... some have expressed concern about transients as you flip the switch, but I don't expect it'd be any harder on the amp than a relay, unless you're a really sloooooooow flipper ...





    peterh

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Add Standby to ST120?

    Post by peterh on Wed Nov 27, 2013 3:02 am

    sKiZo wrote:
    Reason I ask ... Usual routine is to turn the amp on early afternoon for a listening session, then it'll sit until late evening before I spin another disk. Eight hours is too long probably to just leave it on, but maybe not long enough to turn it off and then back on again? In a perfect world, I could just have the heaters idling away so it's ready to go and doesn't have to go thru an unnecessary hot/cold cycle.

    Seems like it'd be simple enough to mod a TDR board to use a manual switch instead of tripping automatically after a time delay ... or better yet ... both? In a perfect world, the TDR would work as intended to soft start the amp automatically, but I could manually switch to standby between sessions, then just turn the amp off at the end of the day.

    I also found this ...

    http://www.singlecoil.com/docs/standby.pdf

    That circuit uses one DPDT to allow either just the AC heater circuits or full power to the amp. I've done similar with ham amps and radios ... some have expressed concern about transients as you flip the switch, but I don't expect it'd be any harder on the amp than a relay, unless you're a really sloooooooow flipper ...




    Standbyswitches are dangerous to your tubes !!
    At least the ones that cut's B+ This will slowly "poison" the cathods, an effect that takes place within hours and is recognized by reducing the emission.

    If you want to silence an amp, then connect a breaker to ground the signal.

    BNR_1

    Posts : 78
    Join date : 2013-06-11

    Re: Add Standby to ST120?

    Post by BNR_1 on Wed Nov 27, 2013 9:41 am

    peterh wrote:
    sKiZo wrote:
    Reason I ask ... Usual routine is to turn the amp on early afternoon for a listening session, then it'll sit until late evening before I spin another disk. Eight hours is too long probably to just leave it on, but maybe not long enough to turn it off and then back on again? In a perfect world, I could just have the heaters idling away so it's ready to go and doesn't have to go thru an unnecessary hot/cold cycle.

    Seems like it'd be simple enough to mod a TDR board to use a manual switch instead of tripping automatically after a time delay ... or better yet ... both? In a perfect world, the TDR would work as intended to soft start the amp automatically, but I could manually switch to standby between sessions, then just turn the amp off at the end of the day.

    I also found this ...

    http://www.singlecoil.com/docs/standby.pdf

    That circuit uses one DPDT to allow either just the AC heater circuits or full power to the amp. I've done similar with ham amps and radios ... some have expressed concern about transients as you flip the switch, but I don't expect it'd be any harder on the amp than a relay, unless you're a really sloooooooow flipper ...




    Standbyswitches are dangerous to your tubes !!
    At least the ones that cut's B+   This will slowly "poison" the cathods, an effect that takes place within hours and is recognized by reducing the emission.

    If you want to silence an amp, then connect a breaker to ground the signal.
    Wow that is new to me. Been playing with guitar amps for a very long time and most of the ones I have used is common to have a standby switch for heater filament only. Never had issues with the tubes and some of them are very old stock tubes still going on strong.

    peterh

    Posts : 642
    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Add Standby to ST120?

    Post by peterh on Wed Nov 27, 2013 9:48 am

    There is several sources for the opinion that standby switches are bad for your tubes, one is :

    http://www.valvewizard.co.uk/standby.html

    BNR_1

    Posts : 78
    Join date : 2013-06-11

    Re: Add Standby to ST120?

    Post by BNR_1 on Wed Nov 27, 2013 11:08 am

    peterh wrote:There is several sources for the opinion that standby switches are bad for your tubes, one is :

    http://www.valvewizard.co.uk/standby.html
    It's good to know these things. When it comes to guitar amps most of them have it and by default you tend to use it for its intended purposes. Just my observation and personel experience it never appeared to cause early failure of tubes. Maybe guitar amps vs. stereo amps are done differently? Possible the damage to tubes are so minute it is not noticeable? Or the possibility that I simply do not play my amps long enough to encounter this issue? So many factors. But it does make you wonder why guitar amps have it and stereo amps do not. I just figured guitar amps are more prone for on/off situations thus someone long ago thought it may serve useful.

    peterh

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    Join date : 2012-12-25
    Location : gothenburg, sweden

    Re: Add Standby to ST120?

    Post by peterh on Wed Nov 27, 2013 11:21 am

    BNR_1 wrote:
    peterh wrote:There is several sources for the opinion that standby switches are bad for your tubes, one is :

    http://www.valvewizard.co.uk/standby.html
    It's good to know these things.  When it comes to guitar amps most of them have it and by default you tend to use it for its intended purposes.  Just my observation and personel experience it never appeared to cause early failure of tubes.  Maybe guitar amps vs. stereo amps are done differently?  Possible the damage to tubes are so minute it is not noticeable?  Or the possibility that I simply do not play my amps long enough to encounter this issue?  So many factors.  But it does make you wonder why guitar amps have it and stereo amps do not.  I just figured guitar amps are more prone for on/off situations thus someone long ago thought it may serve useful.
    the "reasons" for adding a standby switch is mentioned in the above link. Read it, then you could google about "cathode poisoning".

    Now, the damage may not be significant, but on the other hand, a standby that cuts the B+ is not anything needed anyway, so why bother ? ( it's easier and safer to ground the signal )

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Add Standby to ST120?

    Post by sKiZo on Wed Nov 27, 2013 4:25 pm

    Different circuits than what I'm used to when adding stand by ...  Reason I asked. Then again, I heard the same concerns about the mod for ham amps, and I've had a couple that have been running on standby for many years with some really expensive tubes ...

    Good links ... I did catch the part about "urban myths" regarding tube cycles and that the most susceptible would be the rectifier - which in my case is already set up for slow start ...

    Not sure what you're talking about when you refer to grounding the signal. Relay?

    Pray tell ... more please!

    Wondering if any "cathode poisoning" that might result would be offset by minimizing hot/cold cycling. That, from what I understand, is the real tube killer. Trading bad for worse, or vice versa.


    peterh

    Posts : 642
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    Re: Add Standby to ST120?

    Post by peterh on Wed Nov 27, 2013 4:39 pm

    sKiZo wrote:Different circuits than what I'm used to when adding stand by ...  Reason I asked. Then again, I heard the same concerns about the mod for ham amps, and I've had a couple that have been running on standby for decades ...

    Good links ... I did catch the part about "urban myths" regarding tube cycles and that the most susceptible would be the rectifier - which in my case is already set up for slow start ...

    Not sure what you're talking about when you refer to grounding the signal. Relay?

    Pray tell ... more please!

    Wondering if any "cathode poisoning" that might result would be offset by minimizing hot/cold cycling. That, from what I understand, is the real tube killer. Trading bad for worse, or vice versa.

    grounding might be a relay operated grounding , it also might be ( if politically correct :-) a MOSFET.
    But if you have a mechanical switch it could break / shorten the input signal as is . ( relays and MOSFET
    might have the advantage that they can be located close to the input and don't need the signal to be routed to a frontpanel).

    But as tube lifetime, suppose tubes will last 1000h ( most say they will last longer), and you play for 5h each day, that is 200 days. Round it up to a year, and make purchases as "normal service". Make
    the purchase in good time , whenever a good deal arises. If the amp's tubes are still working, let them be
    and enjoy the "savings" ( stored tubed don't get old and they don't loose value).

    If you ( like i planned but never did ) install an "hour-meter" in the amp you can have a much better control of usage.



    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Add Standby to ST120?

    Post by sKiZo on Wed Nov 27, 2013 6:24 pm

    I'm thinking the TDR board already does that then ... all that would be necessary would be a switch to allow you to bypass the automatic trigger for the relay ...

    Thanx for the reminder about a timer. Like the meters, I'd have thought one would be easier to find. Mechanical, yes ... 120v clock drive, not so much, especially an analog version. I found these, but no zero reset that I can find ...



    Right now, I'm using Old Faithful ...


    arledgsc

    Posts : 330
    Join date : 2012-11-30
    Location : SF Bay CA

    Re: Add Standby to ST120?

    Post by arledgsc on Thu Nov 28, 2013 1:02 am

    If you already have the relay board a very simple standby mechanism would be to add a switch to ground the relay board timer chip's threshold input.  Closing the switch grounds the threshold pin and keeps the relay open indefinitely.  When you want to take it out of standby open the switch and HV is applied after the timer chip's normal RC timeout.  I believe the relay board uses a 555 timer type chip.

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Add Standby to ST120?

    Post by sKiZo on Thu Nov 28, 2013 6:37 pm

    Like this then ...



    But ... assUme the amp's already been playing and I want to set it to standby ... would that mod make the relay cycle off when the switch is flipped, idling the B+ ? Seems like all it would do is prevent the timer cycle itself. Turn the switch back on, and the timer starts, triggering either a non-event, or causing the relay to cycle either on or off, depending on current state. Can't test it here as I don't have a TDR board (yet) to play with.

    If that doesn't make sense, don't mind me ... it's the tryptophan talking ... (urp!)

    PS ... got word back on that AC hours meter I pic'd earlier. It does NOT have a zero reset. They do usually stock a similar one that does, and I'll get a heads up when they got one to look at in a couple weeks.

    arledgsc

    Posts : 330
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    Location : SF Bay CA

    Re: Add Standby to ST120?

    Post by arledgsc on Fri Nov 29, 2013 11:35 am

    I stand corrected and sorry for the confusion.  The 555 timer states are controlled by a flip-flop and once timed out lowering the threshold voltage will not cause the relay to toggle.  

    A method in this case would be to utilize the Reset terminal (pin 4).  When Reset is low the Output is toggled low and the Discharge (pin 7) transistor grounds the threshold voltage indefinitely until Reset is a again logic high and the RC circuit retimes a start.   The Fairchild datasheet read this morning has a better explanation of basic monostable operation.   And assuming, of course, the relay board is wired like a typical 555 timer.

    The relay board though may "hard" pull Reset up directly to Vcc.   If you want to use Reset you may need to isolate the hard pullup and use a resistor (1k to 10k ohm) to Vcc instead.  Then connect a switch to the Reset pin for standby operation.   Close the switch (ground) and Reset is low. open the switch and Reset is high.

    Gain sorry for the initial brain strain.   drunken 

    Fairchild 555 Timer datasheet     Nice block diagram on Page 2 and Reset explanation on Page 4.

    Laminarman

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    Join date : 2009-12-30

    Re: Add Standby to ST120?

    Post by Laminarman on Fri Nov 29, 2013 7:17 pm

    OK I'm going to be a TOTAL newbie here. You don't just turn these dang things on and listen to music?? I'm going to email Bob a few questions about a 70 vs 120, but first, do you have to warm up an amp like a 1960's Mustang in the dead cold of winter in Buffalo, NY??? I have the Morgan Jones books on order, so I'm learning still. All I know is I listened to a McIntosh 275 at Classic Audio the other day with a pair of B&W speakers and vinyl. I almost died. I wonder now if they turned them on last week knowing I'd wander in?? Shocked 

    sKiZo

    Posts : 1285
    Join date : 2013-04-01
    Location : Michigan USA

    Re: Add Standby to ST120?

    Post by sKiZo on Sat Nov 30, 2013 12:29 am

    Like fine wine ... you need to take your time. On the bright side, you don't ever have to sniff the cork. tongue 

    Typically, you only need to give a tube amp a couple minutes to warm to where you won't hurt anything, but I find that it takes a good five minutes for the bias to stabilize. Even then, you may get thru a cut or two of warm up music before the amp starts to give it's very best. You can hear the music bloom when that happens.

    Couple extra steps, but certainly not as anal retentive as cuing up vinyl can be or breaking in a reed on a wind instrument. And as you've already found when auditioning the Big Mac, well worth the wait.

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