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post #3691 of 3701

Man am I confused.  The first bit of confusion is the notion that it is the transformer , which continues to provide power making low level music via residual power from the transformer after the amp is turned off.  I am not an EE or even an ee or e, but I thought that power came from the electrolytic capacitors. 

After reading the strongly worded cautionary statement regarding about not  leaving headphones attached,.  However my personal history seems to  contradict this thinking . I have never experienced nasties between HP and the plate of the power tube in an OTL design.

What kind of damage occurs?  I have should have been destroying my headphones for years, yet they sound pretty good to me barring normal wear. My current HP system construct is a SinglePower Extreme (an OTL) and either Sennheiser HD 700s  the AKG KXX.  There is the occasional fairly rare guest appearance by the Beyer DT 770 Pro 32 Ohm. 

Oddly I have never heard or read of  HP immolations or pyrotechnics.  Yet  I  know I will of course unplug my HPs. I have as bad a case of audiophilitis nervosa as the next guy!

Seriously is there an idiots guide to a basic understanding    home  electronics  for home and perhaps (only if absolutely neccesarry} pro audio..

.

post #3692 of 3701

Just to chime in, I have a La Figaro 339 OTL amp, and I have always turned the amp on/off with headphones unplugged. Never had issues with arcs that way.

Also re: pinging sounds, the glass of a tube expands when warming up and makes ping sounds. Some 'lesser' quality tubes will warm up for a minute or two (svetlana UFO 6AS7G), while tubes with thicker glass (Bendix 6080WB) will make pinging noises for 20+ minutes until the glass has fully expanded.

post #3693 of 3701

Like many things in life, many have never had a problem leaving their headphones plugged in while turning their OTL on and off. However, I personally know of two people who have. In each case, they powered up their OTL, a power tube shorted and the current surge took out their headphones.

 

Powering up and powering down is stressful on vacuum tubes and these are the times when they most often fail, sometimes catastrophically. And of course, you never know in advance. So I always advise caution. The best practice is to be unplugged when turning on and off. Be careful out there....

 

Cheers

post #3694 of 3701

I like the sound of tubes warming up :) Then again, I mainly listen to vinyl when using my headphone amp and don't mind the odd crackle at the beginning of an LP or inbetween tracks. 

post #3695 of 3701
Quote:
Originally Posted by adeadcrab View Post
 

Just to chime in, I have a La Figaro 339 OTL amp, and I have always turned the amp on/off with headphones unplugged. Never had issues with arcs that way.

Also re: pinging sounds, the glass of a tube expands when warming up and makes ping sounds. Some 'lesser' quality tubes will warm up for a minute or two (svetlana UFO 6AS7G), while tubes with thicker glass (Bendix 6080WB) will make pinging noises for 20+ minutes until the glass has fully expanded.


Does the Bendix 6080WB go by any other name.  I ask because Bendix had purpose built tubes for fairly specific applications (read  as  'uses' which is what the word meant before smart phones)  I would like to buy a pair and would appreciate any help finding dealers who sell them.

 

Somewhere in the bottom of a box I own some Bendix tubes that I was told were super EL-84s.  They are remarkable tubes construction wise.  These tubes have very  thick ceramic spacers and the thick glass as noted.  The problem is they have a different pin out and resemble 6AQ5s electrically. They were a throw in freebee so no financial loss.

post #3696 of 3701
Quote:
Originally Posted by Mechans1 View Post
 


Does the Bendix 6080WB go by any other name. 

The 6080WB tubes I have are rebranded as Tung Sol.

I have actually dropped one (!!) accidentally from standing height and it is still ok: rock solid construction..

post #3697 of 3701
Quote:
Originally Posted by Mechans1 View Post
 

Man am I confused.  The first bit of confusion is the notion that it is the transformer , which continues to provide power making low level music via residual power from the transformer after the amp is turned off.  I am not an EE or even an ee or e, but I thought that power came from the electrolytic capacitors. 

After reading the strongly worded cautionary statement regarding about not  leaving headphones attached,.  However my personal history seems to  contradict this thinking . I have never experienced nasties between HP and the plate of the power tube in an OTL design.

What kind of damage occurs?  I have should have been destroying my headphones for years, yet they sound pretty good to me barring normal wear. My current HP system construct is a SinglePower Extreme (an OTL) and either Sennheiser HD 700s  the AKG KXX.  There is the occasional fairly rare guest appearance by the Beyer DT 770 Pro 32 Ohm. 

Oddly I have never heard or read of  HP immolations or pyrotechnics.  Yet  I  know I will of course unplug my HPs. I have as bad a case of audiophilitis nervosa as the next guy!

Seriously is there an idiots guide to a basic understanding    home  electronics  for home and perhaps (only if absolutely neccesarry} pro audio..

.

 

Long ago, I experienced 5998's arcing over on one one of my SP Extremes but I was very lucky and no damage occurred.

Others using different amps have not been lucky and the HP driver was blown.

 

Warm up noises have not been a problem for me.

post #3698 of 3701
Quote:
Originally Posted by rosgr63 View Post
 
Quote:
Originally Posted by Mechans1 View Post
 

Man am I confused.  The first bit of confusion is the notion that it is the transformer , which continues to provide power making low level music via residual power from the transformer after the amp is turned off.  I am not an EE or even an ee or e, but I thought that power came from the electrolytic capacitors. 

After reading the strongly worded cautionary statement regarding about not  leaving headphones attached,.  However my personal history seems to  contradict this thinking . I have never experienced nasties between HP and the plate of the power tube in an OTL design.

What kind of damage occurs?  I have should have been destroying my headphones for years, yet they sound pretty good to me barring normal wear. My current HP system construct is a SinglePower Extreme (an OTL) and either Sennheiser HD 700s  the AKG KXX.  There is the occasional fairly rare guest appearance by the Beyer DT 770 Pro 32 Ohm. 

Oddly I have never heard or read of  HP immolations or pyrotechnics.  Yet  I  know I will of course unplug my HPs. I have as bad a case of audiophilitis nervosa as the next guy!

Seriously is there an idiots guide to a basic understanding    home  electronics  for home and perhaps (only if absolutely neccesarry} pro audio..

.

 

Long ago, I experienced 5998's arcing over on one one of my SP Extremes but I was very lucky and no damage occurred.

Others using different amps have not been lucky and the HP driver was blown.

 

Warm up noises have not been a problem for me.

Glenn warned me about this could happen.....this is why I always have headphones unplugged for a few minutes for my tubes to warm up....and always unplug before shutting down...also believe this is what Glenn recommended to me.

 

I run the 5998 & the C3gs often in my amp.....my amp has the 5998 switch and runs C3g natively, without adapters, I make sure I have my 5998 switch in position before powering up my amp.....it is definitely one of my favorite combos....even with the Grado RS1

 

 

Listening to some Buddy Guy right now....wonderful.


Edited by whirlwind - 7/12/16 at 7:38am
post #3699 of 3701

Nice photo, great amp.

 

Better safe than sorry.

post #3700 of 3701
Quote:
Originally Posted by gibosi View Post

As I mentioned earlier, popping, creaking and pinging sounds are quite common with 6AS7G. These tubes have 2.5 amp heaters and they get very hot. And as the tube heats up, these are the sounds the interior metal parts make as they expand. And in my experience the 5998 is the noisiest of all.

Now, I have no knowledge regarding the physical condition of your amp, dust and dirt, and so on, but again, even in a squeaky-clean amp, these tubes are going to creak, groan and pop as they heat-up... and as they cool down. It reminds me of the sounds an automobile engine makes after it is turned off.

Again, my advice, wait several minutes for these tubes to heat up and stabilize. And then connect your headphones, relax and enjoy.

Hi Gibosi, I never heard all that strange noises from my 6AS7Gs, maybe some pops as the tubes heat up. They reach operating temperature after, say, five minutes, but I feel that top sound is only achieved after a minimum of half an hour playing music. I know this does not make sense from a technical point of view, the tube reaches its operating temperature and then stays more or less in that temperature, but what about the preamp, the other circuits involved, and the input tubes ? We are talking about an OTL preamp, in which the 6AS7Gs are output tubes that provide current to drive headphones, and in my setup as a pure preamp, to drive two mono, SS power amps. In this role, it is an extremely powerful preamp, however compatible with the power amp inputs, it clearly dominates the scene and the sound of the tubes are absolutely predominant. I quickly set the amps (NAD 2400 in mono, 450 watts) at 25% power, and this little audio wisdom saved the life of my beloved speakers, some day when I powered up the preamp unaware that the amps were left on from the night before, producing a freaking loud POP that would have kill the speakers for shure, if the amps were set for 100% power. In fact, this same NAD amps have blown two tweeters, one mid and one 8 inch woofer before, with my previous speakers, because its "power envelope" circuit allows dynamic power pulses 3 or 4 times above its rated power. Problem is, rise time is so fast that it can bypass protection fuses and blow the drivers...dangerous amps for sure, but -as you can imagine- extremely dynamic and seriously powerful. And neutral, with the 6AS7G preamp, the NADs sound like tubes, and since the OTL is utterly dynamic and detailed, is like a perfect match. I feel that the sound of this kind of preamp is not at all stable thru its operation cycle, it reaches good sound after half an hour, but it have ups and downs, after two hours, maybe it reach its best, but this is my subjective opinion, of course...
post #3701 of 3701

I would agree that tube amps often sound their best after being on an hour or longer. However, my original post was only about safety. In order to protect headphones and ears when using an OTL, it is best to wait 5 minutes or so before plugging in headphones. This allows the tube enough time to reach normal operating temperature. But as you note, it does seem to take at least 30 minutes or longer for everything to stabilize and "settle in".

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