[Jim_T]

Quote:

Originally Posted by phergus_25 /img/forum/go_quote.gif Turn the volume knob to nothing and then switch phones. Good luck with the new amp! -greg

Excellent. Thanks for the quick reply. Loving the amp already...

Jim

 

[Amarok]

I would also be cautious about charge remaining in the caps after powering
the amp off. Especially SP amps with their mega-farads of capacitance. Caps
can hold a charge for quite a long time after power is removed. I don't know
if Mikhail has included circuity for some kind of fast discharge or even if
it is possible to decrease the discharge time to, say, a few minutes without
tearing a hole in the fabric of space-time. Or at least without vaporizing
the amp and it's owner.

If anyone knows better, please let me know, so I can swap tubes without the
heebie-jeebies.

I use a paper towel to hold the tubes when inserting and removing tubes.
Hopefully, this is adequate for keeping the glass clean.

A

 

[nikongod]

my mpx3 has a bleeder resistor across the last cap.
granted its an old toaster box

, but its a safety feature, and adding one isn't a major hastle or detrimental. i can see no reason to have removed it from newer revisions.

the thing runs full steam ahead until after the heaters stop glowing, so i give it a good 15 minutes to bleed off. waiting until the amp is just done playing is definitely inadequate.

 

[Mrvile]

Quote:

Originally Posted by 003 /img/forum/go_quote.gif Just a note, when you have your tube amp turned on, you should ALWAYS give it some kind of lead (have the headphones plugged in), even if you are not playing anything. Otherwise it will damage the tubes.

I did not know this. Thanks for the tip.

 

[sacd lover]

Quote:

Originally Posted by 003 /img/forum/go_quote.gif Just a note, when you have your tube amp turned on, you should ALWAYS give it some kind of lead (have the headphones plugged in), even if you are not playing anything. Otherwise it will damage the tubes. I vote for sticky. BTW, I want your amp sacdlover

The word lead was a typo and should be load, in case anyone wasnt sure what that meant.

You cant have it.

 

[Jim_T]

Quote:

Originally Posted by sacd lover /img/forum/go_quote.gif At this point I plug in whatever headphones I plan to use. This isnt something to obcess about .... but your tubes will last longer if you keep a load connected whenever the amp is on. Without a load present, for an extended time, you can get what they call "cathode stripping" .... which can drastically shorten the life of your tubes.

Quote:

Originally Posted by 003 /img/forum/go_quote.gif Just a note, when you have your tube amp turned on, you should ALWAYS give it some kind of lead (have the headphones plugged in), even if you are not playing anything. Otherwise it will damage the tubes.

Sorry everyone, but as a tube noob I'm finding this, well, contradictory. I realize 003 just wrote "ALWAYS" and maybe I'm asking to be pummelled with my own ignorance, but sacd lover wrote "for an extended time." So which is it? Like I said before, I've heard that the hardest thing on the tubes is turning the amp on and off, but is a two-second load-free period while I change cans worse? And as far as loads are concerned, would having something connected to the pre-amp outs be considered a load, or just the headphone plug and speaker cable terminals? Thanks for your attention, and sorry if this is one of those controversial issues in tube-land.

 

[musicexpression]

Quote:

Originally Posted by Jim_T /img/forum/go_quote.gif And another question, if you all don't mind. I just got a Cayin HA-1A amp today (merry Christmas, indeed!) and I'm wondering if I need to turn it off when I change headphones. On the one hand, you're meant to keep a constant load, but on the other, you're not meant to keep turning the amp on and off. Which is worse? If I stop the music and turn the volume all the way down on the amp is it OK to change headphones without turning it off? Seems to work OK with my GS-1, but tubes are new to me. Thanks in advance for your help. Jim

hey, same here, i just got myself a Cayin HA-1A.... on and off it's been running-in an accumulated for about 15+ hours using either my HD650 or my home bookshelf speakers. its pretty powerful to drive my 3-way bookshelf speakers.

i would say it's really a good amp. but you might want to connect the L/R speaker binding posts with a 10-ohm 10-watt wirewound resistor, so that the EL84s will always see a load. i have tried many times to unplug my cans w/o turning down the volume and there's no loud popping during connection/disconnection. but one thing to take note, that u must switch off the amp whenever u toggle between triode/ultralinear mode, else u'll get bad pops even with the volume turned down.

the stock tubes that came with my Cayin are their in-house 12AX7 and 12AU7 preamp tubes while the power tubes are Electro-Harmonix. hiss level seems pretty non-existent w/o any signal connected at the inputs (i muted the input RCA)

what i understand from the schematic diagram (they included this in the user manual), frequent turning on/off should not be a problem, as the 6.3VAC EL84s heater connections are directly wired to a small secondary winding of the main toroidal transformer. during a cold-start, i observed the heaters start glowing after a while. maybe the secondary windings of the transformer act as a soft-on delay switch that buffers the instantaneous full current from frying the heaters.

the heater element (i think they are DC-fed) for the 12AX7/AU7 appears to be more "protected", as there is a 10,000uF 25V capacitor connected in parallel to the heater connections immediately after the full-wave rectifier to soak up any surge during turn-on. so i think it shd be safe to turn on/off at will ;p

 

[sacd lover]

Quote:

Originally Posted by Jim_T /img/forum/go_quote.gif Sorry everyone, but as a tube noob I'm finding this, well, contradictory. I realize 003 just wrote "ALWAYS" and maybe I'm asking to be pummelled with my own ignorance, but sacd lover wrote "for an extended time." So which is it? Like I said before, I've heard that the hardest thing on the tubes is turning the amp on and off, but is a two-second load-free period while I change cans worse? And as far as loads are concerned, would having something connected to the pre-amp outs be considered a load, or just the headphone plug and speaker cable terminals? Thanks for your attention, and sorry if this is one of those controversial issues in tube-land.

I was referring to an OTL design .... as all my amps are OTL. Having an OTL amp on without the headphones connected will cause excess tube wear if you run the amp for extended periods of time that way; but no damage to the amp. I have also never had any ill effects from a quick headphone change with my OTL amps.

But the Cayin is transformer coupled. More than just causing wear and tear on the tubes, if you leave a transformer coupled amp on an extended period without a load you can burn up your transformer. A transformer coupled amp is best served by always having a load connected. I, however, cant answer what the cumulative effects of a quick headphone change would be with a transformer coupled headamp .... operating a short time without a load. A preamp connection is a load .... so if you have your headamp doing double duty as a preamp you should be fine.

 

[Jim_T]

Quote:

Originally Posted by musicexpression /img/forum/go_quote.gif hey, same here, i just got myself a Cayin HA-1A.... on and off it's been running-in an accumulated for about 15+ hours using either my HD650 or my home bookshelf speakers. its pretty powerful to drive my 3-way bookshelf speakers. i would say it's really a good amp. but you might want to connect the L/R speaker binding posts with a 10-ohm 10-watt wirewound resistor, so that the EL84s will always see a load. i have tried many times to unplug my cans w/o turning down the volume and there's no loud popping during connection/disconnection. but one thing to take note, that u must switch off the amp whenever u toggle between triode/ultralinear mode, else u'll get bad pops even with the volume turned down. the stock tubes that came with my Cayin are their in-house 12AX7 and 12AU7 preamp tubes while the power tubes are Electro-Harmonix. hiss level seems pretty non-existent w/o any signal connected at the inputs (i muted the input RCA) what i understand from the schematic diagram (they included this in the user manual), frequent turning on/off should not be a problem, as the 6.3VAC EL84s heater connections are directly wired to a small secondary winding of the main toroidal transformer. during a cold-start, i observed the heaters start glowing after a while. maybe the secondary windings of the transformer act as a soft-on delay switch that buffers the instantaneous full current from frying the heaters. the heater element (i think they are DC-fed) for the 12AX7/AU7 appears to be more "protected", as there is a 10,000uF 25V capacitor connected in parallel to the heater connections immediately after the full-wave rectifier to soak up any surge during turn-on. so i think it shd be safe to turn on/off at will ;p

Great, thanks for the info. Sounds like my amp is basically the same as yours, with the lack of hiss and EL84EH tubes. I guess we should head on over to the dedicated HA-1A thread and give our impressions.

Quote:

Originally Posted by sacd lover /img/forum/go_quote.gif I was referring to an OTL design .... as all my amps are OTL. Having an OTL amp on without the headphones connected will cause excess tube wear if you run the amp for extended periods of time that way; but no damage to the amp. I have also never had any ill effects from a quick headphone change with my OTL amps. But the Cayin is transformer coupled. More than just causing wear and tear on the tubes, if you leave a transformer coupled amp on an extended period without a load you can burn up your transformer. A transformer coupled amp is best served by always having a load connected. I, however, cant answer what the cumulative effects of a quick headphone change would be with a transformer coupled headamp .... operating a short time without a load. A preamp connection is a load .... so if you have your headamp doing double duty as a preamp you should be fine.

Thanks for the clarification and the sense of relief that it brings. We now return to your previously-scheduled tube talk...