Thanks for the video been an audiophile for 34 years and just bought my first real tube integrsted amp and I love it ! The Doge 10 MK2b its a beast ! 59.5 pounds using golden lion KT88
HI OP, I have a real interest in antennas also. I have posted a few on a 20 meter rotating dipole and some LPDA antennas for FM broadcast band and TV frequencies. I have a keen interest in the simple coax chokes and hope to do a video with my understanding of it soon. Thanks for your comments.
I have several thoughts. Filamentary triodes are greatly dependent on filament current and the makeup of the filament nickel alloy. Additionally there is the element of filament aging. To develop free barium with which to emit (along with some strontium) the filament must be run at elevated temperature at a particular schedule after manufacturing that determine the final emission and stability. Any change in the combination can effect the outcome. The fade in emission tells me that the tubes were never broken down and aged properly, there is a contamination in the filament alloy or too much reducing agent causing failing emission or an interface layer, or it’s just plain poisoned. To compound things the worse manner in which the aging was done the more sensitive to variation in filament temperature which is a function of voltage and current. A just sealed I’m aged Tube depending on alloy and emission coating can have very very low emission and it comes up only after proper aging. Many of the current tube companies use indirect heated cathode nickels as filament nickels. This can be ok, but it results in a very mechanically weak filament. Other alloys no longer in production were far superior but the industry and margins are too low for any of the manufacturers to have any of them made and processed into the required ribbon sizes. They do the best with what they have.
Nice information. Thanks for posting. I sometimes see new and especially old tubes that fade in emission when tested for several seconds. I always take this as a weak cathode and avoid them. These tubes that just couldn't perform at proper filament voltage still showed fading emission even at a higher filament voltage. I gave some of them several minutes in the hope that they would stabilize but they never did. One pair was still in warranty and was replaced with no issue. But I have to say, the EH tubes performed really well and are now in service working great with no issues. Maybe in the next few weeks I will test them again and see if they are stable and still equal.
I haven't checked currents yet but voltage is good. In one particular high power Eimac tube I have used, the 4-1000A, I did learn to check filament current to assess the worthiness of the tube. The filament is made of strings of wire running vertically in the tube and as the tube ages, the filament strands break off and fall to the bottom of the tube. You can sometimes see "trash" inside the tube but a current measurement of this particular tube will tell if the filament is deteriorating. Normal filament is 7.5 volts at 21 amps so if the current is down around 15-16 amps, the tube is used up. I suppose these tubes (the 300B's) may be able to be used with 6 volts or so on the filaments (?)
We sent the Sophia tubes back as they are in warranty. I really hate to make any of these items look bad because vacuum tubes are a truly specialty device and even back-in-the-day, I bet there was a reasonably good percentage that were not perfect. I do still have the other pair and I will indeed measure the current thru a good one and a bad one. As could be seen at the end of the video, they checked better with higher voltage on the filament but I still did detect a declining meter reading even at the higher filament voltage still indicating a problem. All four of the EH tubes were solid. I had a set of EH KT90's a few years ago that I was impressed with and was getting 80 watts from them. Never had a problem with them but sold the amplifier.
Hello, I realize that these tubes may be under warranty but you might check the tube pins. I have seen the solder connections on the pins that weren't secure
Completely agree with you, Tim. I have seen the same thing but in the cases that I remember, the tube either did not work at all, (open filament) or it performed so badly (open screen wire on some KT88's). In the bad pin KT88 case I have encountered, I started comparing the capacitance readings between the plate and or the cathode to the other elements in a good tube and comparing to the bad tube and discovered the unsoldered screen pin. I have been able to repair each of these types of problems of open pins by heating the pin and putting a good bit of solder down the hole in the pin. This has Not worked in all cases with me. Before I did this, I did contact the seller (Ebay) and got my refund and was told to keep and throw away the tubes. I have also received other tubes with open filaments that were broken internally and nothing could be done. Also, I have some pretty amazing news since posting this video. I plugged in the two bad tubes into the tube tester and set the voltage for 6.3 volts and left everything running for at least 30 minutes each (for each tube). Afterwards, I turned everything off and removed the two bad tubes shown in the video. Just virtually minutes ago, I plugged them in and they test as good as 70 and are stable.. wow... heating the filament for 30-45 minutes at 6.3 volts seems to have revived them. I would have never believed that. They surely aren't thorium-tungsten filaments. It is hard to believe but I am amazed and they seem to be OK now running at 5 volts on the filament. Only time will tell if they are truly "fixed" and stable.
You're probably right about the QC on those filaments. Possibly the wrong filament wire even. I'm trying to decide between the TV7/U tester and a Hickok seems the Hickok might be more versatile especially for newer tubes. Not easy to find good ones of either ar a reasonable price.
Hi Bill, Check out my reply below to "tim" for what I have just discovered. I figured the same thing - probably the wrong wire for the filament. I sure agree about the price some people are asking on Ebay for tube testers and unfortunately, you never know what you are going to get. I bought mine from a fellow I worked with in Chicago. He had it for lots of years and I don't think he had used it in the last 30+ years so it had not been "fixed" or "modded" if you know what I mean. No "mystery holes". Anyway, even so, I had to get another meter movement for mine as the original one got to where it was sticking so bad it was becoming hard to use and get the same reading each time.
I had some older but new ( nos) triodes ( some were given top me because they were not good ! ) with that problem.............after resoldering the pins with the filaments they came to life and tested OK.........
Hi Frank - I have also solved problems by resoldering pins. But I never thought of resoldering filament pins to try and solve the problem with the meter dropping when the tube tester button was held down. Were you able to solve that problem by resoldering filament pins?
@@ElPasoTubeAmps You are right , that were tubes with low test values ! But the tubes with dropping values ( new production mostly ) are a real problem ( even a commercial scam ) Some pretend that this is no problems ( Young ahn) , i do not agree with such commercial policy ! You can look up at the strict and serious aging procedure that WE applied to the 300B to understand that today the world has changed ..... Thanks for your reply and have a nice day . hope you didn't suffer from Elliot.......... th-cam.com/video/2rbyz16QmiE/w-d-xo.html
I have been thinking if you use a forced air cooling system then the amp doesn't have to be in the house and could be installed in the basement of the house if you have a basement and use the strange twist sockets that are used with the 4CX250 vacuum tubes and you should be able to drive hard to drive load impedances like 2R speakers or Piezo transducers.
Again, this channel is so helpful, so credit where its due obviously. I am a bit skeptical of chinese made 300b tubes. I have really liked psvanne and others, Do you guys have experience with linlai 300bg tubes? They are the most affordable ones out there. I think they will be acceptable, maybe not exceptional, but could these be at least good value reference tubes? The cheaper tubes are the ones I am going for, because I need 8 of them for an otl design from transcendent sounds, tubes and circuit book. Theres 1 driver tube and 4 tubes per channel, I think this amp will SOLVE IT ALL. The best part is, you have all that triode action from the 4 300b's and they are being utilized very lightly so diminished operating parameters are minimized. Another question besides 'are the linlai any good' ;;; The official design uses a transformer going from 120v to center tapped 35v+35v and steps it up to 180v with a doubler circuit using 2 diodes and capacitors and 2 chokes... I think this is an ok way of doing it, kindof unusual though seeing that it can be done with a normal rectifier and nice capacitor bank (is that all?) at 120v to 170v which will be enough voltage at least. And if you can, add an autotransformer which most diyers have already, it can be operated for the called for 180v. Idk honestly, have not tried that yet, but I would not bother with the -10v difference. There is the other concern that when these are on load, the voltage can drop further, probably with both types of power supply shemes... But the best part is, no input transformer potentially and no output transformer, which for me is the only way to do it... About to make the purchase of 4 and build 1 mono, this is the only schematic that makes total sense both in audio quality and cost. Its a very very good compromise.
Thank you.. I have the amplifier for all practical purposes finished and I have been enjoying it for the past few weeks. I have been out of town to Denver and around and have come down with a bad case of back issues so I am trying to get past that and get it back on the workbench for a final video. It is performing amazingly well. From preliminary testing, it is not going to perform like a McIntosh amplifier with 0.5% THD from 20 to 20 KHz at full power but it sounds marvelous. I can't explain it but there is something about the low gain triodes that is charming. I know someone is going to say it is the linearity of the low mu triodes and maybe it is just that simple. I get around 40 watts average power out of it and that is more than sufficient to drive my efficient speakers. Hopefully, I will be able to post results soon. I think my next project will be a more compact stereo version of some low gain PP triodes, maybe even 300B's (except they are so expensive). I particularly like the vintage 6B4G as they are the 2A3 with a 6 volt filament and an octal base. I also have some VT-25's (I believe they are also know as a, 10) that are calling me from the attic to be put back into service... :-) Thanks for your message.
ElPaso TubeAmps Feel better soon. Curious that your customer is a mono fan, rare today. I like mono too but via two channels. VT25s are great but lower power than 6B4Gs also Rp is quite high so it might be hard to find a pp output trans. What about parallel single ended? 😲
Yes, indeed, mono out of two speakers. I am perfectly happy with that also. There is also the problem of having two of each of these vintage and exotic transformers, including the driver transformers/inductors, etc. When one thinks about having a truly matched set of beautiful condition UTC iron, we are talking about amps that sell for multi-thousands as the components are just so hard to get. So, with two speakers, one in each corner of the room, I am perfectly happy with one channel. As for SE or PP, I always go PP. Just makes sense to me. I have built amplifiers with a variable NFB loop and with the FB turned really low, the amplifier gets loud quickly but distorts quickly also - maybe around 8-10 watts. With 16 dB of NFB it will do 80 watts at 1% THD but has the characteristic compressed sound to it. I am speaking of an actual amplifier I built running PP KT90's some years ago. When I think about it, probably the 300B is one of the best choices for a low mu (very linear) triode that will deliver a respectable amount of power in PP. The high mu triodes like the 811A all run class-B and have their own driving issues and high Z plate load. Everything is a compromise. I am getting better quickly... no use in dragging around in pain. Maybe even tonight I can get to the shop and have some fun and post.
ElPaso TubeAmps single ended: it might be the distortion spectrum. No cancellation of even order harmonics, the good harmonics. Odd order are the baddies that pp preserves.
try running hotter for 30sec "bright" direct heated cathodes will then "sometimes" boil more thorium to the surface of the tungsten filament. This 'may' rejuvenate the tube for awhile. then back off to 5v and test. never know how long such process will work. But some times, you can get a bit more time at risk of opening the filament
EH Tubes, and pretty much ALL the stuff coming out of that Russian factory have been OK. You'll find some sonic differences, but the tubes have been consistently reliable.
Young ahn is an audio engineer that sez you can revitalize tubes! Thise are showing better numbers from running some current through them. He has a yt channel and designs and sells fluxion hifi amps.
I have a 7D/U and I can say after more tahn 35 years f use it is reliable ..........I keep some tubes as a reference for testing and the tester is stable .......
@@frankgeeraerts6243 ok yah a 7D/U is very nice tester as well. Doesn't read directly in mhos but still quite accurate. I have a hickok 752 that I use and have calibrated to within 5%. And for basic tests of quality I have an EMC 206 mutual conductance tester. Which is actually a dynamic testerlike the Eico series
Have you use or have you seen KR audio tubes, built in the Czech Republic. supposed to be very good had awards from American tca tube collectors Association of America? Anyway maybe you would like to check them out here's the website Kraudio.com there's a TH-cam channel showing the manufacture of their tubes as well. What do you think of them
Hi John, I am here to tell you, these 300B tubes are in a world of their own. I thought I had the 6L6 family of tubes pretty well figured out but these beasts are different. Drive requirements and the expectations of performance from the old UTC iron are Much harder to obtain than might be thought. I have yet to see anyone post lab grade analytical performance of these types of 300B amplifiers and/or vintage UTC transformer performance. I fear that challenging the ingrained belief that these tubes and this iron is anything less than the ultimate perfection is like challenging Einstein's theory of relativity. From my limited experience it looks like the speed of light is not the ultimate speed where time stops and mass becomes infinite. I plow onward to completion toward whatever it is.
You can make that experiment with any tube. If you increase the filament voltage, the emission will increase as well. I did some experiments about rejuvenating tubes by overheating them for a certain time. The tubes emission increased every single time while being overheated, no matter if it were directly heated oder indirectly heated tubes. So, what you determined is, in my opinion, not necessarily a thing of poor QC.
I definitely like the EH tubes much more than the other two brands. And I am getting 50+ watts at 1 KHz. The challenge now is to completely stabilize the amplifier probably with some grid-stoppers and other parasitic mitigating additions. The objective of this build is not to tweek the amplifier to "perfection", 20-20KHz at ultra low THD but rather to reproduce a vintage design and sound.
Terrible quality control from FM and Sophia. For the money you expect consistency and reliability. Were they bought from ebay? Are you only building one amp? Is your cuatomer is a mono fan?
Thanks for the video been an audiophile for 34 years and just bought my first real tube integrsted amp and I love it ! The Doge 10 MK2b its a beast ! 59.5 pounds using golden lion KT88
Thank you for posting these videos. Im not much of a tube guy (more into antennas) but I enjoy how you explain things. Please keep it up!
HI OP,
I have a real interest in antennas also. I have posted a few on a 20 meter rotating dipole and some LPDA antennas for FM broadcast band and TV frequencies. I have a keen interest in the simple coax chokes and hope to do a video with my understanding of it soon. Thanks for your comments.
I have several thoughts. Filamentary triodes are greatly dependent on filament current and the makeup of the filament nickel alloy. Additionally there is the element of filament aging. To develop free barium with which to emit (along with some strontium) the filament must be run at elevated temperature at a particular schedule after manufacturing that determine the final emission and stability. Any change in the combination can effect the outcome. The fade in emission tells me that the tubes were never broken down and aged properly, there is a contamination in the filament alloy or too much reducing agent causing failing emission or an interface layer, or it’s just plain poisoned. To compound things the worse manner in which the aging was done the more sensitive to variation in filament temperature which is a function of voltage and current. A just sealed I’m aged Tube depending on alloy and emission coating can have very very low emission and it comes up only after proper aging. Many of the current tube companies use indirect heated cathode nickels as filament nickels. This can be ok, but it results in a very mechanically weak filament. Other alloys no longer in production were far superior but the industry and margins are too low for any of the manufacturers to have any of them made and processed into the required ribbon sizes. They do the best with what they have.
Nice information. Thanks for posting. I sometimes see new and especially old tubes that fade in emission when tested for several seconds. I always take this as a weak cathode and avoid them. These tubes that just couldn't perform at proper filament voltage still showed fading emission even at a higher filament voltage. I gave some of them several minutes in the hope that they would stabilize but they never did. One pair was still in warranty and was replaced with no issue. But I have to say, the EH tubes performed really well and are now in service working great with no issues. Maybe in the next few weeks I will test them again and see if they are stable and still equal.
You're absolutely right ................I have the very strict and havy aging procedure of WE 300B and since then I know new production fail..........
David perhaps consider comparing the filament currents between the good and bad tubes. Good video, thanks.
I haven't checked currents yet but voltage is good. In one particular high power Eimac tube I have used, the 4-1000A, I did learn to check filament current to assess the worthiness of the tube. The filament is made of strings of wire running vertically in the tube and as the tube ages, the filament strands break off and fall to the bottom of the tube. You can sometimes see "trash" inside the tube but a current measurement of this particular tube will tell if the filament is deteriorating. Normal filament is 7.5 volts at 21 amps so if the current is down around 15-16 amps, the tube is used up. I suppose these tubes (the 300B's) may be able to be used with 6 volts or so on the filaments (?)
We sent the Sophia tubes back as they are in warranty. I really hate to make any of these items look bad because vacuum tubes are a truly specialty device and even back-in-the-day, I bet there was a reasonably good percentage that were not perfect. I do still have the other pair and I will indeed measure the current thru a good one and a bad one. As could be seen at the end of the video, they checked better with higher voltage on the filament but I still did detect a declining meter reading even at the higher filament voltage still indicating a problem. All four of the EH tubes were solid. I had a set of EH KT90's a few years ago that I was impressed with and was getting 80 watts from them. Never had a problem with them but sold the amplifier.
Hello,
I realize that these tubes may be under warranty but you might check the tube pins. I have seen the solder connections on the pins that weren't secure
Completely agree with you, Tim. I have seen the same thing but in the cases that I remember, the tube either did not work at all, (open filament) or it performed so badly (open screen wire on some KT88's). In the bad pin KT88 case I have encountered, I started comparing the capacitance readings between the plate and or the cathode to the other elements in a good tube and comparing to the bad tube and discovered the unsoldered screen pin. I have been able to repair each of these types of problems of open pins by heating the pin and putting a good bit of solder down the hole in the pin. This has Not worked in all cases with me. Before I did this, I did contact the seller (Ebay) and got my refund and was told to keep and throw away the tubes. I have also received other tubes with open filaments that were broken internally and nothing could be done.
Also, I have some pretty amazing news since posting this video.
I plugged in the two bad tubes into the tube tester and set the voltage for 6.3 volts and left everything running for at least 30 minutes each (for each tube). Afterwards, I turned everything off and removed the two bad tubes shown in the video. Just virtually minutes ago, I plugged them in and they test as good as 70 and are stable.. wow... heating the filament for 30-45 minutes at 6.3 volts seems to have revived them. I would have never believed that. They surely aren't thorium-tungsten filaments. It is hard to believe but I am amazed and they seem to be OK now running at 5 volts on the filament.
Only time will tell if they are truly "fixed" and stable.
You're probably right about the QC on those filaments. Possibly the wrong filament wire even.
I'm trying to decide between the TV7/U tester and a Hickok seems the Hickok might be more versatile especially for newer tubes. Not easy to find good ones of either ar a reasonable price.
Hi Bill,
Check out my reply below to "tim" for what I have just discovered.
I figured the same thing - probably the wrong wire for the filament.
I sure agree about the price some people are asking on Ebay for tube testers and unfortunately, you never know what you are going to get. I bought mine from a fellow I worked with in Chicago. He had it for lots of years and I don't think he had used it in the last 30+ years so it had not been "fixed" or "modded" if you know what I mean. No "mystery holes". Anyway, even so, I had to get another meter movement for mine as the original one got to where it was sticking so bad it was becoming hard to use and get the same reading each time.
Thanks for this vedio.i want to buy a tube tester.wich tube tester you advise me.
I had some older but new ( nos) triodes ( some were given top me because they were not good ! ) with that problem.............after resoldering the pins with the filaments they came to life and tested OK.........
Hi Frank - I have also solved problems by resoldering pins. But I never thought of resoldering filament pins to try and solve the problem with the meter dropping when the tube tester button was held down. Were you able to solve that problem by resoldering filament pins?
@@ElPasoTubeAmps You are right , that were tubes with low test values !
But the tubes with dropping values ( new production mostly ) are a real problem ( even a commercial scam )
Some pretend that this is no problems ( Young ahn) , i do not agree with such commercial policy !
You can look up at the strict and serious aging procedure that WE applied to the 300B to understand that today the world has changed .....
Thanks for your reply and have a nice day .
hope you didn't suffer from Elliot..........
th-cam.com/video/2rbyz16QmiE/w-d-xo.html
I have been thinking if you use a forced air cooling system then the amp doesn't have to be in the house and could be installed in the basement of the house if you have a basement and use the strange twist sockets that are used with the 4CX250 vacuum tubes and you should be able to drive hard to drive load impedances like 2R speakers or Piezo transducers.
Again, this channel is so helpful, so credit where its due obviously.
I am a bit skeptical of chinese made 300b tubes. I have really liked psvanne and others, Do you guys have experience with linlai 300bg tubes? They are the most affordable ones out there.
I think they will be acceptable, maybe not exceptional, but could these be at least good value reference tubes?
The cheaper tubes are the ones I am going for, because I need 8 of them for an otl design from transcendent sounds, tubes and circuit book.
Theres 1 driver tube and 4 tubes per channel, I think this amp will SOLVE IT ALL.
The best part is, you have all that triode action from the 4 300b's and they are being utilized very lightly so diminished operating parameters are minimized.
Another question besides 'are the linlai any good' ;;;
The official design uses a transformer going from 120v to center tapped 35v+35v and steps it up to 180v with a doubler circuit using 2 diodes and capacitors and 2 chokes... I think this is an ok way of doing it, kindof unusual though seeing that it can be done with a normal rectifier and nice capacitor bank (is that all?) at 120v to 170v which will be enough voltage at least. And if you can, add an autotransformer which most diyers have already, it can be operated for the called for 180v.
Idk honestly, have not tried that yet, but I would not bother with the -10v difference.
There is the other concern that when these are on load, the voltage can drop further, probably with both types of power supply shemes...
But the best part is, no input transformer potentially and no output transformer, which for me is the only way to do it...
About to make the purchase of 4 and build 1 mono, this is the only schematic that makes total sense both in audio quality and cost. Its a very very good compromise.
Waiting anxiously for the next video!
Thank you.. I have the amplifier for all practical purposes finished and I have been enjoying it for the past few weeks. I have been out of town to Denver and around and have come down with a bad case of back issues so I am trying to get past that and get it back on the workbench for a final video. It is performing amazingly well. From preliminary testing, it is not going to perform like a McIntosh amplifier with 0.5% THD from 20 to 20 KHz at full power but it sounds marvelous. I can't explain it but there is something about the low gain triodes that is charming. I know someone is going to say it is the linearity of the low mu triodes and maybe it is just that simple. I get around 40 watts average power out of it and that is more than sufficient to drive my efficient speakers. Hopefully, I will be able to post results soon.
I think my next project will be a more compact stereo version of some low gain PP triodes, maybe even 300B's (except they are so expensive). I particularly like the vintage 6B4G as they are the 2A3 with a 6 volt filament and an octal base. I also have some VT-25's (I believe they are also know as a, 10) that are calling me from the attic to be put back into service... :-)
Thanks for your message.
ElPaso TubeAmps Feel better soon. Curious that your customer is a mono fan, rare today. I like mono too but via two channels. VT25s are great but lower power than 6B4Gs also Rp is quite high so it might be hard to find a pp output trans. What about parallel single ended? 😲
Yes, indeed, mono out of two speakers. I am perfectly happy with that also. There is also the problem of having two of each of these vintage and exotic transformers, including the driver transformers/inductors, etc. When one thinks about having a truly matched set of beautiful condition UTC iron, we are talking about amps that sell for multi-thousands as the components are just so hard to get. So, with two speakers, one in each corner of the room, I am perfectly happy with one channel.
As for SE or PP, I always go PP. Just makes sense to me. I have built amplifiers with a variable NFB loop and with the FB turned really low, the amplifier gets loud quickly but distorts quickly also - maybe around 8-10 watts. With 16 dB of NFB it will do 80 watts at 1% THD but has the characteristic compressed sound to it. I am speaking of an actual amplifier I built running PP KT90's some years ago.
When I think about it, probably the 300B is one of the best choices for a low mu (very linear) triode that will deliver a respectable amount of power in PP. The high mu triodes like the 811A all run class-B and have their own driving issues and high Z plate load. Everything is a compromise.
I am getting better quickly... no use in dragging around in pain. Maybe even tonight I can get to the shop and have some fun and post.
ElPaso TubeAmps single ended: it might be the distortion spectrum. No cancellation of even order harmonics, the good harmonics. Odd order are the baddies that pp preserves.
I guess your lack of new posts suggests you might not be in such good shape. Hope that is not so, but if it is, get well soon.
where have you gone???
Hello David,
Just checking in. How is the new amp design coming along? Hope all is well. Keep em glowing!
mike mathews makes some nice things :-) hope u have a great day.
try running hotter for 30sec "bright"
direct heated cathodes will then "sometimes" boil more thorium to the surface of the tungsten
filament. This 'may' rejuvenate the tube for awhile. then back off to 5v and test.
never know how long such process will work. But some times, you can get a bit more time at risk of opening the filament
EH Tubes, and pretty much ALL the stuff coming out of that Russian factory have been OK. You'll find some sonic differences, but the tubes have been consistently reliable.
I agree - I like the consistency of the EH tubes.
I have tube tester envy and I have a couple of nice testers
Young ahn is an audio engineer that sez you can revitalize tubes! Thise are showing better numbers from running some current through them. He has a yt channel and designs and sells fluxion hifi amps.
where is the Full Music ？
Hello you have a vaccum tubes tester for sale.thnx
If your not getting consistent results you should go through your tester and calibrate it after all parts check out
I have a 7D/U and I can say after more tahn 35 years f use it is reliable ..........I keep some tubes as a reference for testing and the tester is stable .......
@@frankgeeraerts6243 ok yah a 7D/U is very nice tester as well. Doesn't read directly in mhos but still quite accurate. I have a hickok 752 that I use and have calibrated to within 5%. And for basic tests of quality I have an EMC 206 mutual conductance tester. Which is actually a dynamic testerlike the Eico series
Have you use or have you seen KR audio tubes, built in the Czech Republic. supposed to be very good had awards from American tca tube collectors Association of America? Anyway maybe you would like to check them out here's the website Kraudio.com there's a TH-cam channel showing the manufacture of their tubes as well. What do you think of them
Hi John,
I am here to tell you, these 300B tubes are in a world of their own. I thought I had the 6L6 family of tubes pretty well figured out but these beasts are different. Drive requirements and the expectations of performance from the old UTC iron are Much harder to obtain than might be thought. I have yet to see anyone post lab grade analytical performance of these types of 300B amplifiers and/or vintage UTC transformer performance. I fear that challenging the ingrained belief that these tubes and this iron is anything less than the ultimate perfection is like challenging Einstein's theory of relativity. From my limited experience it looks like the speed of light is not the ultimate speed where time stops and mass becomes infinite. I plow onward to completion toward whatever it is.
You can make that experiment with any tube. If you increase the filament voltage, the emission will increase as well. I did some experiments about rejuvenating tubes by overheating them for a certain time. The tubes emission increased every single time while being overheated, no matter if it were directly heated oder indirectly heated tubes. So, what you determined is, in my opinion, not necessarily a thing of poor QC.
EH is currently making reliable power tubes
I definitely like the EH tubes much more than the other two brands. And I am getting 50+ watts at 1 KHz. The challenge now is to completely stabilize the amplifier probably with some grid-stoppers and other parasitic mitigating additions. The objective of this build is not to tweek the amplifier to "perfection", 20-20KHz at ultra low THD but rather to reproduce a vintage design and sound.
write test values on tube with marker, wipes off with alcohol
Terrible quality control from FM and Sophia. For the money you expect consistency and reliability. Were they bought from ebay? Are you only building one amp? Is your cuatomer is a mono fan?
Badges of JJ tubes ( new ) have the same problem...................testing values falllllllllllll !
I dont think ypu are a licensed ham radio operator. Other hams usualy identify with their callsign KA5WZY