The Western Electric 300A was rated at 450V, and 40W plate.
The Western Electric 300B was rated at _?_V, and 40W plate.
In April of 1950, the Western Electric 300B was re-rated at 400V, and 36W plate.
But in any case, Mesh 300B tubes are Not 300B tubes.
Of the 2 Mesh plate 300B tubes I had, I used them at very conservative voltages, currents, and plate watts. In spite of that, one of them developed Very leaky grid current. It looked good, but the trash man got the bad one.
I have one left, care for a mesh plate, anyone?
Mono, anyone?
The Western Electric 300B was rated at _?_V, and 40W plate.
In April of 1950, the Western Electric 300B was re-rated at 400V, and 36W plate.
But in any case, Mesh 300B tubes are Not 300B tubes.
Of the 2 Mesh plate 300B tubes I had, I used them at very conservative voltages, currents, and plate watts. In spite of that, one of them developed Very leaky grid current. It looked good, but the trash man got the bad one.
I have one left, care for a mesh plate, anyone?
Mono, anyone?
You are supplying useless info here. The bias set by measuring the voltage across a cathode resistor. I forget the actual value but it sets the bias correctly. Plate voltage is about 460VDC, so plate to cathode is pretty close to max.
So to the OP, follow the manufacturer's instructions.
Do you read the posts? Clearly not good practice if you don't know the actual working conditions. If the 300B in your amp is working at more 28W plate dissipation you cannot use mesh plate 300B's, regardless of the bias. That's usually their max plate dissipation.
I suggest that you find someone that understands what is doing and let him change the tubes for you.....
You can see here that the 300B with (true) mesh plate can only manage 28W max but it is recommended to run it at 22W:
http://www.emissionlabs.com/datasheets/EML300B-mesh.htm
It is very likely that your amp runs the 300B at more than 22W. Other mesh 300B's are the same, even those with punched plate (which is not true mesh).
The 300B with solid plate from the same manufacturer has a maximum of 40W but it is recommended to stay within 36W or even less for longer service life.
Then there is the 300B XLS that can handle 55W....
http://www.emissionlabs.com/datasheets/EML300B-mesh.htm
It is very likely that your amp runs the 300B at more than 22W. Other mesh 300B's are the same, even those with punched plate (which is not true mesh).
The 300B with solid plate from the same manufacturer has a maximum of 40W but it is recommended to stay within 36W or even less for longer service life.
Then there is the 300B XLS that can handle 55W....
No. You cannot use meshplates. As i stated earlier, that leaves out the TJ. They will die within hours, if not sooner. The others mentioned JJ, EH, Gold Lion and Emmision Labs will all work.
But you must bias according to the manufacturers instructions.
This couldn't be easier.
I received the following Mastersound Model 300B bias setting instructions.
That is why I mentioned the 845 tube in my earlier post of this thread.
You can see for yourself in the attached file, it mentions the 845 tubes on the Mastersound Model 300B amp.
Sometimes it helps to have the correct product name, not the fact that it is a Mastersound amp that uses 300B tubes, but perhaps the amp in question is not a Mastersound Model 300B.
There are many sources of useless information. I too may have been mislead.
That is why I mentioned the 845 tube in my earlier post of this thread.
You can see for yourself in the attached file, it mentions the 845 tubes on the Mastersound Model 300B amp.
Sometimes it helps to have the correct product name, not the fact that it is a Mastersound amp that uses 300B tubes, but perhaps the amp in question is not a Mastersound Model 300B.
There are many sources of useless information. I too may have been mislead.
Attachments
I think that mention of the 845 tube is a mistake, it should say 300B. This is probably due to the fact that the circuit is the same as that of the compact 845 and the instructions have been adapted just changing the name of tube and possibly the adjustment value. However the value the meter needs to read might be the same because clearly that is not the bias!
Mastersound has produced 845 amps since the beginning and only recently has introduced 300B amps in their catalogue.
The most important bit is that the meter needs to read 15V. It doesn't say that 15V is the bias! Not the same thing at all.....
Mastersound has produced 845 amps since the beginning and only recently has introduced 300B amps in their catalogue.
The most important bit is that the meter needs to read 15V. It doesn't say that 15V is the bias! Not the same thing at all.....
I have just double checked on their website. Apparently the 300B amps have been in production for about 15 years, while the 845 ones for 20 years. Looking at the amps, their construction, pre-amp/driver tubes they use it looks like the kind of circuit is the same for both 300B and 845 with few necessary adjustments including the PSU and OT.....
That is correct. There is a Compact 300B, and a Compact 845 model. Both use the 15V as the measurement needed. Of course the power supplies are totally different as are the other parameters. This just allows them to use the same chassis for two different products.
15V is the correct reading though.
15V is the correct reading though.
Ok but it's just the meter reading to have the correct bias which will be 70-80-90V or whatever. It's not the bias as suggested at the beginning and that caused confusion and discussion....repetita juvant!
20 years ago I got a box of ten Svetlana 300B...and this summer I have build my first 300B Push-Pull amp...by now three died already...typically the filament gets really red and than disconnects.
I found SV300-Test from that time were people had six of them on hand and 4 died with 3 month, so I feel in good company overall, but I am still thinking if I should change my operating conditions which are:
- Fixed bias (Rod coleman regs)
- 5,8K PP transformer
- 50-55mA
- 440V on the Plate, so approx. 25W max dissipation.
- heated at 4.9V with Rod Coleman regs
...which are pretty much the working conditions mentioned in the Svetlana 300 datasheet I believe.
I considered to go down to 350V and raise the current to 65 mA as an alternative, but a colleague mentioned that he uses his with a mixture of fixed bias and a 220 cathode resistor in SE at 3k5 at 480V and 80mA...Genalex 300B and he is extremely happy with them...
Nevertheless...two questions arise:
Is there anything wrong with my operating conditions or do I experience the typical Svetlana illness here ?
What are todays opinion on the Genalex ? Still breakage ? So, EML/Elrog etc ...? After having seen 15 years ago many pairs of Kron tubes breaking, I am a bit concerned that filament breakage happens as well on very expensive tubes...
-
I found SV300-Test from that time were people had six of them on hand and 4 died with 3 month, so I feel in good company overall, but I am still thinking if I should change my operating conditions which are:
- Fixed bias (Rod coleman regs)
- 5,8K PP transformer
- 50-55mA
- 440V on the Plate, so approx. 25W max dissipation.
- heated at 4.9V with Rod Coleman regs
...which are pretty much the working conditions mentioned in the Svetlana 300 datasheet I believe.
I considered to go down to 350V and raise the current to 65 mA as an alternative, but a colleague mentioned that he uses his with a mixture of fixed bias and a 220 cathode resistor in SE at 3k5 at 480V and 80mA...Genalex 300B and he is extremely happy with them...
Nevertheless...two questions arise:
Is there anything wrong with my operating conditions or do I experience the typical Svetlana illness here ?
What are todays opinion on the Genalex ? Still breakage ? So, EML/Elrog etc ...? After having seen 15 years ago many pairs of Kron tubes breaking, I am a bit concerned that filament breakage happens as well on very expensive tubes...
-
440V is a little too high for ordinary 300Bs, for my taste, I would prefer 400V/60mA.
But the SV300B of the 1990s was the very worst for mechanical failures. Slow starting (current feed) heating delays the inevitable failure, but I would not risk my amps with them. The detached piece of filament can short-circuit on the other electrodes.
The EML is well made, and slow-starting. At lower cost, the JJ is good, and mine lasted a long time - up to natural wear out. I still use the JJs for testing filament regulators, and they can take all kinds of different startup profile, without breaking.
The EH and other XPO-PUL (Reflektor) factory output sounds alright, but they have a short life that usually ends with filaments detached from the support-point. They have been like this for at least 20 years.
But the SV300B of the 1990s was the very worst for mechanical failures. Slow starting (current feed) heating delays the inevitable failure, but I would not risk my amps with them. The detached piece of filament can short-circuit on the other electrodes.
The EML is well made, and slow-starting. At lower cost, the JJ is good, and mine lasted a long time - up to natural wear out. I still use the JJs for testing filament regulators, and they can take all kinds of different startup profile, without breaking.
The EH and other XPO-PUL (Reflektor) factory output sounds alright, but they have a short life that usually ends with filaments detached from the support-point. They have been like this for at least 20 years.
Blitz,
I will list one failure mode of the early Svetlana 300B (I do not believe there were any later Svetlana 300B tubes in production because of the high failure rates of the early ones).
A particular and peculiar failure mode of Svetlana 300B happens with DC powered filaments, and not with AC powered filaments.
On some/many Svetlana 300B tubes, the spacings of the filament to the plate were not equal from one side versus to the other side.
The plates are magnetic.
1.25 Amps DC through the filament has a strong steady magnetic field.
With uneven spacing, the filament is attracted toward the side of the plate that is closest to the filament.
The filament now contacts one side of the grid wires.
That 'bowing' of the hot filament toward the plate causes the filament to contact the grid.
When the filament contacts the grid, the tube is at Zero Bias.
Zero Bias causes high current. The contact is continuous, and the current is continuous.
The output transformer saturates, and the only limitations of plate current is the Zero Bias, the DCR of the output transformer and the power supply current and voltage capability.
Some other manufacturer's 300B may also have uneven spacing of the filament to plate.
But in that case, it is also possible that the filament alloy that Svetlana used has more expansion (and bowing) than other 300B brands. That would also cause the same Zero bias problem and resulting failure.
Does that explain one of the main failure modes of the Svetlana 300B?
(we had 50 or was it 100 of them in an audio club, and we had lots of experience).
You could use AC powered filaments on the remaining Svetlana 300B tubes.
(I would not use the ones that already failed, even if they now seem OK).
But using AC powered filaments on any 300B has the disadvantage of the 2X line frequency intermodulation on all the music frequency/tones. That is discussed in other threads on this forum.
I will list one failure mode of the early Svetlana 300B (I do not believe there were any later Svetlana 300B tubes in production because of the high failure rates of the early ones).
A particular and peculiar failure mode of Svetlana 300B happens with DC powered filaments, and not with AC powered filaments.
On some/many Svetlana 300B tubes, the spacings of the filament to the plate were not equal from one side versus to the other side.
The plates are magnetic.
1.25 Amps DC through the filament has a strong steady magnetic field.
With uneven spacing, the filament is attracted toward the side of the plate that is closest to the filament.
The filament now contacts one side of the grid wires.
That 'bowing' of the hot filament toward the plate causes the filament to contact the grid.
When the filament contacts the grid, the tube is at Zero Bias.
Zero Bias causes high current. The contact is continuous, and the current is continuous.
The output transformer saturates, and the only limitations of plate current is the Zero Bias, the DCR of the output transformer and the power supply current and voltage capability.
Some other manufacturer's 300B may also have uneven spacing of the filament to plate.
But in that case, it is also possible that the filament alloy that Svetlana used has more expansion (and bowing) than other 300B brands. That would also cause the same Zero bias problem and resulting failure.
Does that explain one of the main failure modes of the Svetlana 300B?
(we had 50 or was it 100 of them in an audio club, and we had lots of experience).
You could use AC powered filaments on the remaining Svetlana 300B tubes.
(I would not use the ones that already failed, even if they now seem OK).
But using AC powered filaments on any 300B has the disadvantage of the 2X line frequency intermodulation on all the music frequency/tones. That is discussed in other threads on this forum.
Wow. These are pretty cool insides...I did not expect...wow.
Ok...stop using those Svetlanas with DC...hmmm...
My thoughts/questions:
- Which current production 300B would not have the same problem ? Genalex vs. JJ vs. EML vs. Kron etc ?
- I have read somewhere that the filament construction internally is
-- normally (WE and others) that one filament connection / pin 1 or 4 goes physically to the centre tap of the 300B filament, while the other goes physically to the two outside connections of the filament...is this correct ?
...if true....: A 300B has more like a 10V filament (if you would use - hypothetically - only the outside connection of the filament and no CT) to be honest...which as well gives two different fields of anode-Cathode-Potential and electron flows over the whole surface ....
...which in the case of DC heating open the field of: Should your most negative area on the cathode be on the outside or the CT of the filament. I tested that a lot with the 4p1l and it makes a notable sound difference. So, the CT story is important, if it is confirmed. Than the Pin for DC-Heating going to ground makes a sound difference.
versus:
-- exception is JJ where really one filament end starts at 0V and the other end (so not the CT!) is 5V....
-- on top: JJ came up with a 2a3 with 300B specs, but a filament of 2,5V...sounds like they applied the CT approach to their original 5V filament, no ? Maybe the best solution ?
- EML I believe must have a similar filament approach as JJ as they advertise their latest generation of output tube as well with external CT with a different socket, or in the case of the 300B now as well a 300B with 2.5V !!!
-- on top: Today's russia 300B use a double filament wire, so if one breaks, the second may shine...which as well is a completely different construction again...
Can you confirm / give me insides and make a recommendation which one to prefer ? Both, from a reliability and sonic experience ?
Ok...stop using those Svetlanas with DC...hmmm...
My thoughts/questions:
- Which current production 300B would not have the same problem ? Genalex vs. JJ vs. EML vs. Kron etc ?
- I have read somewhere that the filament construction internally is
-- normally (WE and others) that one filament connection / pin 1 or 4 goes physically to the centre tap of the 300B filament, while the other goes physically to the two outside connections of the filament...is this correct ?
...if true....: A 300B has more like a 10V filament (if you would use - hypothetically - only the outside connection of the filament and no CT) to be honest...which as well gives two different fields of anode-Cathode-Potential and electron flows over the whole surface ....
...which in the case of DC heating open the field of: Should your most negative area on the cathode be on the outside or the CT of the filament. I tested that a lot with the 4p1l and it makes a notable sound difference. So, the CT story is important, if it is confirmed. Than the Pin for DC-Heating going to ground makes a sound difference.
versus:
-- exception is JJ where really one filament end starts at 0V and the other end (so not the CT!) is 5V....
-- on top: JJ came up with a 2a3 with 300B specs, but a filament of 2,5V...sounds like they applied the CT approach to their original 5V filament, no ? Maybe the best solution ?
- EML I believe must have a similar filament approach as JJ as they advertise their latest generation of output tube as well with external CT with a different socket, or in the case of the 300B now as well a 300B with 2.5V !!!
-- on top: Today's russia 300B use a double filament wire, so if one breaks, the second may shine...which as well is a completely different construction again...
Can you confirm / give me insides and make a recommendation which one to prefer ? Both, from a reliability and sonic experience ?
Last edited:
Blitz,
In addition to Svetlana 300B tubes, I have used JJ, Electro Harmonix, Valve Art, and Full Music Mesh plate 300B (I would recommend using mesh plates at lower plate dissipation).
The JJ, and Valve Art worked well. The Electro Harmonix and Full Music worked well, with exceptions as noted next.
One Full Music went Gassy (used at moderate plate dissipation), and one Electro Harmonix would give a brief internal spark when the amp was turned off (filament moving/touching grid?).
But I do not think there was enough of a statistical population for me to say the Electro Harmonix and Full Music are unreliable. (In fact, read about the Electro Harmonix 2A3 below).
I used the 300B tubes in a variety of my designs, with Interstage coupling, and with RC coupling, SE, and push pull, AC filaments, and DC filaments.
I also used 2A3 tubes from Electro Harmonix (monoplate), Sovtek (monoplate), Valve Art (dual plate), and the monoplate JJ 40W 2A3, as well as the monoplate 6.3V Sovtek 6A3.
Don’t quote me about the weight of the tubes, I list my impression only, not a result of a small scale.
As you stated, the JJ (monoplate) 2A3 filament has 2.5V from the center to the two outsides.
And the plate and glass are bigger than a regular 2A3, and even than most 300B tubes.
(And the JJ 300B is also larger than most 300B tubes).
The JJ 300B is the only 300B I have seen with the filament that is wired from end to end.
The Sovtek monoplate 6A3 filament is also wired from end to end.
The Sovtek monoplate 2A3 filament has a center, 2.5V from the center to each side.
It curiously seems a little heavier than the Sovtek 6A3.
I have had fun designing, building, and listening to these tubes.
I will give a little different direction to where I have headed in what tubes I use
(in my next post on this thread).
In addition to Svetlana 300B tubes, I have used JJ, Electro Harmonix, Valve Art, and Full Music Mesh plate 300B (I would recommend using mesh plates at lower plate dissipation).
The JJ, and Valve Art worked well. The Electro Harmonix and Full Music worked well, with exceptions as noted next.
One Full Music went Gassy (used at moderate plate dissipation), and one Electro Harmonix would give a brief internal spark when the amp was turned off (filament moving/touching grid?).
But I do not think there was enough of a statistical population for me to say the Electro Harmonix and Full Music are unreliable. (In fact, read about the Electro Harmonix 2A3 below).
I used the 300B tubes in a variety of my designs, with Interstage coupling, and with RC coupling, SE, and push pull, AC filaments, and DC filaments.
I also used 2A3 tubes from Electro Harmonix (monoplate), Sovtek (monoplate), Valve Art (dual plate), and the monoplate JJ 40W 2A3, as well as the monoplate 6.3V Sovtek 6A3.
Don’t quote me about the weight of the tubes, I list my impression only, not a result of a small scale.
As you stated, the JJ (monoplate) 2A3 filament has 2.5V from the center to the two outsides.
And the plate and glass are bigger than a regular 2A3, and even than most 300B tubes.
(And the JJ 300B is also larger than most 300B tubes).
The JJ 300B is the only 300B I have seen with the filament that is wired from end to end.
The Sovtek monoplate 6A3 filament is also wired from end to end.
The Sovtek monoplate 2A3 filament has a center, 2.5V from the center to each side.
It curiously seems a little heavier than the Sovtek 6A3.
I have had fun designing, building, and listening to these tubes.
I will give a little different direction to where I have headed in what tubes I use
(in my next post on this thread).
Blitz,
I used Directly Heated Triode tubes such as the 300B, 2A3, 6A3; and old 45 tubes
(usually with DC powered filaments).
I also used some indirectly heated tubes such as EL34, 807, and 7591 in Triode wired mode
(With AC filaments).
As time went on, I decided I wanted the filament supply to be as simple as possible, so
I started using more indirectly heated tubes. All my filaments are AC powered.
KT66, KT88, KT77, 6L6GC, 7591, EL34, 807 Beam Power and Pentode tubes
(in Triode Wired Mode).
I also used new old stock 6BX7, and 6CK4 Triodes.
I have used KT66, KT77, KT88, 6L6GC, and 7591S from JJ.
That is also in my current plans for output tubes.
I used ECC82, 12AY7, ECC99, ECC81, ECC83S, ECC803S, and E88CC, all from JJ.
I may try the JJ EF806S pentode later. These are for driver and or invertor stages.
I no longer have any amplifiers with direct heated triodes.
I get my JJ tubes from Eurotubes.
Eurotubes is near my location, and I can call them and say I want a matched pair of JJ model XYZ, and then drive over and pick them up.
Euro Tubes does lots of additional testing of the JJ tubes, before they sell them.
I now use JJ tubes in my amplifiers, with the exception that I sometimes use a driver tube that JJ does not make. But I am using more and more JJ driver tubes, and only JJ output tubes now.
If you stay with 300B and 2A3 tubes, the JJ tubes from Euro tubes should be good for you.
I used Directly Heated Triode tubes such as the 300B, 2A3, 6A3; and old 45 tubes
(usually with DC powered filaments).
I also used some indirectly heated tubes such as EL34, 807, and 7591 in Triode wired mode
(With AC filaments).
As time went on, I decided I wanted the filament supply to be as simple as possible, so
I started using more indirectly heated tubes. All my filaments are AC powered.
KT66, KT88, KT77, 6L6GC, 7591, EL34, 807 Beam Power and Pentode tubes
(in Triode Wired Mode).
I also used new old stock 6BX7, and 6CK4 Triodes.
I have used KT66, KT77, KT88, 6L6GC, and 7591S from JJ.
That is also in my current plans for output tubes.
I used ECC82, 12AY7, ECC99, ECC81, ECC83S, ECC803S, and E88CC, all from JJ.
I may try the JJ EF806S pentode later. These are for driver and or invertor stages.
I no longer have any amplifiers with direct heated triodes.
I get my JJ tubes from Eurotubes.
Eurotubes is near my location, and I can call them and say I want a matched pair of JJ model XYZ, and then drive over and pick them up.
Euro Tubes does lots of additional testing of the JJ tubes, before they sell them.
I now use JJ tubes in my amplifiers, with the exception that I sometimes use a driver tube that JJ does not make. But I am using more and more JJ driver tubes, and only JJ output tubes now.
If you stay with 300B and 2A3 tubes, the JJ tubes from Euro tubes should be good for you.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.