SED C EL34 - opinions !

[Rogue]

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

Why is that?

Why do mass produced amps not use chokes? Simple, cost. Resistors are pennies, chokes are 10 to 20 bucks a pop.

Sorry, I edited my post because I realized it wasn't celar and you beat me to it.

More specifically, why do the screens have a different voltage with a choke than a resistor?

 

[EnGl]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

 

[baron55]

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

Why is that?

Why do mass produced amps not use chokes? Simple, cost. Resistors are pennies, chokes are 10 to 20 bucks a pop.

Sorry, I edited my post because I realized it wasn't celar and you beat me to it.

More specifically, why do the screens have a different voltage with a choke than a resistor?

I also edited my answer for your question

 

[baron55]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

Well SED's are rated at 500v on the screens so you are under their max design spec, so no worries

 

[Rogue]

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

Why is that?

Why do mass produced amps not use chokes? Simple, cost. Resistors are pennies, chokes are 10 to 20 bucks a pop.

Sorry, I edited my post because I realized it wasn't celar and you beat me to it.

More specifically, why do the screens have a different voltage with a choke than a resistor?

I also edited my answer for your question

Thanks. So you're saying that a resistor drops the voltage more than a choke would, so the total supply to the tubes have dropped more than as with a choke? That makes sense. I was somewhat confused...it seemed like you were saying just the screen voltage would be dropped, but I read it wrong. Thanks again.

 

[EnGl]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

Well SED's are rated at 500v on the screens so you are under their max design spec, so no worries

Great , So it's settled - in next week I order C's.

And how long they can be in my amp before they die ?

 

[baron55]

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

Why is that?

Why do mass produced amps not use chokes? Simple, cost. Resistors are pennies, chokes are 10 to 20 bucks a pop.

Sorry, I edited my post because I realized it wasn't celar and you beat me to it.

More specifically, why do the screens have a different voltage with a choke than a resistor?

I also edited my answer for your question

Thanks. So you're saying that a resistor drops the voltage more than a choke would, so the total supply to the tubes have dropped more than as with a choke? That makes sense. I was somewhat confused...it seemed like you were saying just the screen voltage would be dropped, but I read it wrong. Thanks again.

Correct:
The resistor drops the voltage more that feeds the screens and preamp than a choke does, the plate voltage is unchanged for the most part. But this is most noticeable at high volumes when he amp is putting out a lot of power, almost not much difference at bedroom levels.

When screen voltage drops, power drops and creates more sag. Marshall guys love this. But in more modern high gainer's guys want the power amp to stay tight and not sag under load, so they will upgrade to chokes

 

[Rogue]

Correct:
The resistor drops the voltage more that feeds the screens and preamp than a choke does, the plate voltage is unchanged for the most part. But this is most noticeable at high volumes when he amp is putting out a lot of power, almost not much difference at bedroom levels.

When screen voltage drops, power drops and creates more sag. Marshall guys love this. But in more modern high gainer's guys want the power amp to stay tight and not sag under load, so they will upgrade to chokes

Isn't there a "lower power" feature on some amps that is simply making the screens 0 volts? Or perhaps maybe super low voltage? It seems I read somewhere this will basically drop the output by half. Is this correct?

 

[LP Freak]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

Well SED's are rated at 500v on the screens so you are under their max design spec, so no worries

Great , So it's settled - in next week I order C's.

And how long they can be in my amp before they die ?

Hopefully longer than it took you to buy a set.

 

[EnGl]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

Well SED's are rated at 500v on the screens so you are under their max design spec, so no worries

Great , So it's settled - in next week I order C's.

And how long they can be in my amp before they die ?

Hopefully longer than it took you to buy a set.

Daaaa , but hey , SED is a bit of expensive so you know ... And well , they are currently out of stock in my shop and they will be in few days...

Last question - How C change tone when we will crank the amp more ?

 

[baron55]

As for tone, that is subjective. If someone asks me which are the most robust tubes, I will say SED. If someone ask which sound the best, depends on what you are looking for and as others have mentioned, tubes sound different in different amps because of all the variables involved in different designs.

I like the Shuguang (Ruby, Valve art) offerings, for a more modern tone.

 

[EnGl]

As for tone, that is subjective. If someone asks me which are the most robust tubes, I will say SED. If someone ask which sound the best, depends on what you are looking for and as others have mentioned, tubes sound different in different amps because of all the variables involved in different designs.

I like the Shuguang (Ruby, Valve art) offerings, for a more modern tone.

You have experience with SED , their EL34 will be ok for metal ?
I don't mean modern at all only djent or something like that. I mean classy thrash like Exodus or Megadeth and other kinds like Pantera.


I currently have Rubies EL34BHT , I'm really happy with them but unfortunately - they are very hard to find in europe. I know that I can order them from Germany but the shipping ...

 

[baron55]

The SED's will have less bass and more mids, they will also be harder souning, more strident in the upper mids. The Runys, are more mid scooped, have bigger bass to them.

 

[ericsabbath]

The Ruby EL34BHT are good tubes, but I would still pick the SED over them.

The SED's are tighter and have a smoother top end, the mids are complex and all EL34. The bass is tight and controlled.

The Ruby's are spongier compared to the SED's and more compressed, the mids are not as present and there is more top end and bass but the bass is not as focused.


SED= give you the more authentic EL34 tone

Rubys= give you a more modern type of EL34 tone

how does the BHT differs from the BSTR?
cause that's exactly how the BSTR differs from the SED as well

 

[guitarman967]

Doesn't really matter what power tubes people use. I think the original post was what would people here recommend. And many recommend SED.

Basically in the late 80's the Siemens EL34's were running out and there were no alternative quality EL34's. The Sovteks at the time were firecrackers, and the Chinese were worse. The Tesla factory closed and their just was no good alternative. Marshall and others started making their amps with the commonly had 5881WXt from Sovtek, this tube really wasn't a 5881 or even a 6L6, still isn't. But a Russian military tube with similar specs and could handle high voltages and power. These were also stock tubes in SLO's at the time too.

Then in the early 90's a company in St. Petersburg Russia started making a EL34, designed to handle overload conditions found in guitar amps. These tubes were as good as the NOS Siemens and were better than any other tube at the time in the EL34 category. Marshall started back up with EL34 based production. The SED was the only EL34 people would buy at the time. The SED is the only current production tube that can handle 500 volts on the screens. No others can. Thus the bullet proof reputation of the SED.

SED's have more of the vintage EL34 tone and are harder sounding and more mid focused. Players that favor vintage style amps love these, thus the love. But if you are a modern player and want more bass and less mids and more compression, then the JJ and Chinese tubes are popular.

The SED EL34 is better built, more rugged and will last longer plain and simple than the other tubes mentioned here. Whether or not you like the tone is something else.

Yes they are more money, but if you replace them less then it is a wash. Tube manufactures do not make tubes as good as they could because they need to have us keep buying them.

SED have always been the more expensive tube, but since they are much more of a lower volume factory, and the tubes are replaced less often, they charge more.


So as far as taste on what tubes to buy that is up to you, just like the amp and guitar you play.

My favorite preamp tubes are the Chinese, my favorite EL34 is the SED, my favorite KT88 is SED, a close Second is the Penta Labs (Shuguang) KT88SC which ironically is a outstanding tube that costs the same as the SED. 3rd is the KT88-88 that is re-branded by Ruby and Valve art (Shuguang made)

Some of the Sovtek tubes are good (Electro Harmonix, Tung Sol, Mullard, Genelex, Gold Lion)

Buy the way how come no one bitches about the cost of the Genalex (Sovtek) KT77, same cost as the SED's (80.00 a pair)

Youre the man Baron.
I've always wondered why people talked about the plates when it made no sense that any amplifier would exceed the ratings.
I always notice your posts here on RT because they're very informative. Kudos to you

 

[guitarman967]

Damn, thanks guys.
Well, I see that C get so many love ...

You know , I want to buy C not only because of tone.Quality and reliability is on the top of my list. And I know they are very robust , can handle 500 PV or even more.
Not many tubes can handle my amp plate voltage(480) so I'm searching for the best reliability.

I was interested also in JJ 6CA7 (they can handle 500pv) but meh ... We all know the JJ quality.

It is not plate voltage that's the issue, never has been. ALL EL34's can handle 800 volts on the plates no problem, that is minim design spec. Plates don't usually fail unless you have a catastrophic bias runaway. The max design spec limit on screen voltage is 425v to 450v. Most of the Mullards were 425V.

It is the screen voltage that is a tubes limiting factor. Most of the large bottle power tubes were always designed to have the screens run 40% to 50% less than the plate voltage. So if you ran a set of EL34's at 800 volts, the screen would be run at 320 to 400 volts. This would require dual power supplies or 40% taps on the OT which is common in Bass and Hi Fi amps.

But the early guitar amp manufactures wanted to save money, so instead, they tied the screen voltage to the same power supply with just a tad more filtration and usually put a inline series resistance. (aka screen resistor) The screen resistor is supposed to limit current as the screens try to pull current, this causes the voltage to drop hopefully enough to prevent screen meltdown.

The problem, is is you start with the screen voltage above the max limit, (most big guitar amps run 450 and above on the screens) then the chance of failure is much higher.

Most people who talk about plate voltage too high don't understand what they are talking about. Now that comment wasn't directed at anyone here, but to the supposed gurus who think they know. Also the tube companies and vendors spew the same crap, can handle the higher plate voltages, etc.

In most big guitar amps, we run the tubes way out of design spec for the sake of tone. Since the scrrens run pretty close to the plates, is where the misleading plate voltage limitation comes from.

Since SED's had beefed up screens (500v) they were able to much better able to handle the high screen voltages found in most guitar amps.

Thanks , I know that the screens are more harder factor than plates. And as you mentioned - most of el34 can handle 425 or 450.
My amp has 480 PV ( I found info on the net - guy measured pv in 6534 and it was 480 so I don't ever measured this) so the screens can be lower ? I mean 460 or 470 ? (This is what some user pointed )

It depends on the amp, many mass produced amps like Peaveys, don't use chokes. Instead they use a resistor, this adds to the screen resistor resistance and in many causes causes the screen voltages to drop to safer levels.

One thing you see a lot is guys replacing that resistor with a choke, in doing so, unless they adrees the screen rersistors or volatge node, they could be raising the screens above their design limit. EL34 screens are the most sensitive and fragile of the power tubes.

Hmm , how long this SED C can live in that conditions ? (I mean 480 PV with bias about 34mA )

You know , I want a reliable tube , I don't want change tubes for every 3-5 months ... But I must say that currently I play with low volume (about 1, sometimes 2 - but well , I playing in home but in few weeks I will move my gear in bigger place) so I guess I will not stress the power tubes too much ...

Well SED's are rated at 500v on the screens so you are under their max design spec, so no worries

Great , So it's settled - in next week I order C's.

And how long they can be in my amp before they die ?

Hopefully longer than it took you to buy a set.

Daaaa , but hey , SED is a bit of expensive so you know ... And well , they are currently out of stock in my shop and they will be in few days...

Last question - How C change tone when we will crank the amp more ?

Depends on the bias setting generally. In a higher gain amp, they will probably sound best when set with headroom to spare.