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Sorry for the lack of clarity, one of those moments when I left half of what I wanted to say up in my head
From the article you posted, it looks best to use a delayed B+ for indirectly heated tubes (such as the 12AX7), but the article does not make any specific claims for tubes that are directly heated (such as the 2A3), so I'm guessing that I might as well add the switch...
From the article you posted, it looks best to use a delayed B+ for indirectly heated tubes (such as the 12AX7), but the article does not make any specific claims for tubes that are directly heated (such as the 2A3), so I'm guessing that I might as well add the switch...
RE:RE:SWITCH.
Hi,
Don't worry, happens to me all the time.
The final decision is up to you, in practice though not putting in the switch won't cause any damage.
I have a 2A3 amp with DC on all the heaters, since the PSU caps use bleeder resistors it takes them a little time to ramp up to full B+.
I have been doing that for years and never noticed any damage, switching the B+ on without the heater voltage present would be more risky IMHO.
Cheers,
Hi,
Don't worry, happens to me all the time.
The final decision is up to you, in practice though not putting in the switch won't cause any damage.
I have a 2A3 amp with DC on all the heaters, since the PSU caps use bleeder resistors it takes them a little time to ramp up to full B+.
I have been doing that for years and never noticed any damage, switching the B+ on without the heater voltage present would be more risky IMHO.
Cheers,
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To change topics just a little...
I have a few questions about tube amps and Gabe's design in particular that I was hoping someone could help me with.
How long should I expect a set of 2A3 tubes to last in an amplifier with this design? A few months? A few years? I know that this is likely to depend on a few things such as how often I listent, the manufacturer of the tubes, their age, and if they are used or unused... Just looking for a ballpark figure if, say, the amps are used 4 or 5 hours per week?
Also, I was reading something in the Decware page about their 2A3 tubes running close to 200c. At this point, I assume that fingerprints, residue, etc on the glass can lead to premature tube failure. Should any attempts be made to clean the tubes before they are used? If so, how should this be done?
Thanks!
Eric
I have a few questions about tube amps and Gabe's design in particular that I was hoping someone could help me with.
How long should I expect a set of 2A3 tubes to last in an amplifier with this design? A few months? A few years? I know that this is likely to depend on a few things such as how often I listent, the manufacturer of the tubes, their age, and if they are used or unused... Just looking for a ballpark figure if, say, the amps are used 4 or 5 hours per week?
Also, I was reading something in the Decware page about their 2A3 tubes running close to 200c. At this point, I assume that fingerprints, residue, etc on the glass can lead to premature tube failure. Should any attempts be made to clean the tubes before they are used? If so, how should this be done?
Thanks!
Eric
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I'll stop now...
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Ha! OK, now you're answering questions I haven't asked!
I just thought it was funny that I ask about switches for B+ and you give a sort of yes/no answer, then I ask about cleaning tubes and you come back with "it doesn't really matter" evidence...
Please don't take offense, Gabe - I'm a beginner to tube DIY, so I'm probably splitting hairs that don't really matter with my questions
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Gabe: What started my thought process about cleaning the tubes was finding a mention of 200c in the Decware literature. In my mind, I made an analogy to installing Halogen bulbs. I know that Halogens will burn out prematurely if you leave finger prints or other "goo" on them, so it seemed reasonable that 200c output tubes would behave in the same manner and might last longer if it was cleaned.
I'm surprised to hear that the old amps you have are sill running strong with all sorts of kitchen goo on them - do they get very hot? I guess on a similar note, do ALL tubes in a tube amp necessarily get hot, or just the output tubes?
Thanks,
Eric
I'm surprised to hear that the old amps you have are sill running strong with all sorts of kitchen goo on them - do they get very hot? I guess on a similar note, do ALL tubes in a tube amp necessarily get hot, or just the output tubes?
Thanks,
Eric
Hi,
Well, electron tubes aren't halogens...so other than impeding heat dissipation with a ton of smudge, a few fingerprints won't hurt it. Of course, being a true tube lover we all treat our tubes with the utmost respect and avoid holding them by their glass envelope... Especially when it's a European tube where you risk to render the label unreadable.
That all depends on the current running through them, obviously output tubes tend to get scorchingly hot when biased for class A operation.
Tip: Let the tubes cool down before you pull them out of their sockets.
Cheers,
Well, electron tubes aren't halogens...so other than impeding heat dissipation with a ton of smudge, a few fingerprints won't hurt it. Of course, being a true tube lover we all treat our tubes with the utmost respect and avoid holding them by their glass envelope... Especially when it's a European tube where you risk to render the label unreadable.
That all depends on the current running through them, obviously output tubes tend to get scorchingly hot when biased for class A operation.
Tip: Let the tubes cool down before you pull them out of their sockets.
Cheers,
Hey Eric,
There are different formulations for glass used. The glass used in halogen bulbs might not be as well tempered and definitely not as thick as a tube/valve.
Tubes/valves do get very hot, to the point of mildly burning your finger (pain for a few hours) to second degree burns (water blisters), some power tubes/valves being the culprit of the latter. I know... first hand experience, no pun intended.
Like Frank, I clean the tubes/valves when I get the old radios. Use water, not alcohol. Believe it or not, water is as good a cleaner for glass as Windex, since Windex is about 95% water anyway!
Gabe
There are different formulations for glass used. The glass used in halogen bulbs might not be as well tempered and definitely not as thick as a tube/valve.
Tubes/valves do get very hot, to the point of mildly burning your finger (pain for a few hours) to second degree burns (water blisters), some power tubes/valves being the culprit of the latter. I know... first hand experience, no pun intended.
Like Frank, I clean the tubes/valves when I get the old radios. Use water, not alcohol. Believe it or not, water is as good a cleaner for glass as Windex, since Windex is about 95% water anyway!
Gabe
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