I second Jim for tubes. He may have an crooked or slightly tilted one to sell too as he lists those for less $ @ $13.50 if he has any near top of listings. EH EL34 is way down and sells singles too. EH 6CA7 might be considered too. Some like sonics better.
If you have $ Gold Lion reissues are really liked for sonics etc. if you google about the KT-66, KT-77, & KT-88 . They are said to sound as good or better than the best NOS tubes.
He also sells those Russian 6N3C-E or 6P3S-E which might be worth trying, @ $29.50 a pair. They are a military grade tube and should last! Well liked by many for sonics. I bought some and they are really heavy compared to others.
Good to have spares if you can afford it and you get to try different tubes.
If you have $ Gold Lion reissues are really liked for sonics etc. if you google about the KT-66, KT-77, & KT-88 . They are said to sound as good or better than the best NOS tubes.
He also sells those Russian 6N3C-E or 6P3S-E which might be worth trying, @ $29.50 a pair. They are a military grade tube and should last! Well liked by many for sonics. I bought some and they are really heavy compared to others.
Good to have spares if you can afford it and you get to try different tubes.
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Lots of good suggestions here. I've tried the EH EL34, and had bad luck with a dud pair. They had issues with bad screens - glowing wires and nasty stuff. Similar problems were seen with some Sovtek EL34G - they look an awful lot like the EH EL34. I have a couple sets of EH 6CA7. I like their sound, but they have a weird mechanical jingling thing going on. Others have noticed it too, and I worry about their long term reliability. I've used the Russian 6P3S-E tubes, and was very pleased with them. If you get a set that is well tested (not gassy), you won't likely find a nicer tube for the price. I'd highly recommend them. I also like my New Sensor Gold Lion KT88. They were pricey, but I don't regret the money I spent on them as they are excellent tubes. I'd imagine their other KT tubes are nice, and hope to try them someday.
Make sure you swap the EL34 between channels. Be absolutely certain you've got a bad tube, and not a dud solder joint at the tube socket.
Make sure you swap the EL34 between channels. Be absolutely certain you've got a bad tube, and not a dud solder joint at the tube socket.
Hi,
Can I really swap all those tube (KT66, KT77, KT88, 6N3C-E, 6P3S-E, 6CA7) without any modification to the amp? My Rx7 are 560 ohm.
In short, I want to know what type of tube that I can put, and maybe the characteristics of each, so that I can maybe buy two pairs to experience different sound.
Best regards,
Can I really swap all those tube (KT66, KT77, KT88, 6N3C-E, 6P3S-E, 6CA7) without any modification to the amp? My Rx7 are 560 ohm.
In short, I want to know what type of tube that I can put, and maybe the characteristics of each, so that I can maybe buy two pairs to experience different sound.
Best regards,
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George has a chart on the Tubelab site for different values for all the tubes you can use.
The bigger tubes should just be swappable as if that R of 560 ohms is for the EL34's it will give a lower voltage than what say KT-88's could take leading to an easier life for them. It might be a trade off for sonics though.
The 6P3S-E is like a 6L6 and 6CA7 probably would run the same as the EL34's. They all look close on the chart.
What is your B+ , PS transformer specs or make and model #, and do you have a choke?
The bigger tubes should just be swappable as if that R of 560 ohms is for the EL34's it will give a lower voltage than what say KT-88's could take leading to an easier life for them. It might be a trade off for sonics though.
The 6P3S-E is like a 6L6 and 6CA7 probably would run the same as the EL34's. They all look close on the chart.
What is your B+ , PS transformer specs or make and model #, and do you have a choke?
Hi,
I consider myself a kit builder, so sometime, I don't totally understand the technical stuff, but I will try to give you all the info I can. I don't understand how to read the chart on the tubelab web site
My power transfo is the Edcor XPWR035 "This transformer has multiple voltage windings, 740V (370-0-370) at 200mA center tapped, 6.3V (3.15-0-3.15) at 5A center tapped and 5V at 2A." from EDCOR Electronics Corporation. XPWR035-120
My output transfo are the gsxe from edcor again.
I also have a little hammond choke 156R (1.5H @ 200mA DC).
No motor cap.
Tube rectifier (no solid state option installed).
I usually run it on triode mode and without cathode feedback. I honestly don't know what this all mean, but I like the sound better that way.
Thanks,
You have the amp setup for EL34s. They are more or less the "least common denominator" of the various types in terms of plate current. Similar tubes, like the 6L6GC and 6P3S-E, will work just fine. Bigger tubes will also work fine and as rmyauck said, will probably last forever. They won't be operating at their optimal point sonically, though. They'll "want" more plate current and for that will need smaller value cathode resistors.
The nitty gritty is here:
Tubes & Transformers
The nitty gritty is here:
Tubes & Transformers
So the B+ is about 450V?
What is the primary impedence of OPT transformer. Like say 3000K or 5000K ohms?
All shown on charts.
How about adding Dave Gillespie's bias mod which would maybe allow adjustment with a screw driver? Maybe Voltages are too high for the up to -37V regulator.
What is the primary impedence of OPT transformer. Like say 3000K or 5000K ohms?
All shown on charts.
How about adding Dave Gillespie's bias mod which would maybe allow adjustment with a screw driver? Maybe Voltages are too high for the up to -37V regulator.
Attachments
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I started with 560 ohm cathode resistors in mine, but thought that many of the "smaller" tubes (EL34, 6L6, etc.) were running just a little too hot. The larger tubes (KT88, 6550) are fine with 560 ohm.
Yes, you can put any of those tubes in your amp. You might not need to change anything, but I would keep a very close eye on the color of the plates in a dark room. If you start to see hints of red color on the plates, consider increasing the 560 ohm resistors. I settled on 810 ohms for mine.
Hi,
Two things:
1.
How should I read the Power Output Simulation table Tubes & Transformers
Here is what I understand (right or wrong)
Tube: given, the tube type
B+ voltage: Given from the power transformer
Load Z: Given by the output transformer
Vp: ???
Vk: ???
Rk: Cathode resistance, a potential degree of freedom, can be change.
Ik: ???
Diss (idle): ??? What is the color code? Values should be high, low, or else?
Pwr Out: Power output, maximum energy that the amp can send to the speakers
Dist *nd: distortion, should be minimize.
DF: damping factor, show be as low as possible.
Can you shed some light on my question marks.
2.
Also, 810r is not there for the el34, but somebody suggested to use it as Rk. Why, and what will hapend?
Thanks,
Two things:
1.
How should I read the Power Output Simulation table Tubes & Transformers
Here is what I understand (right or wrong)
Tube: given, the tube type
B+ voltage: Given from the power transformer
Load Z: Given by the output transformer
Vp: ???
Vk: ???
Rk: Cathode resistance, a potential degree of freedom, can be change.
Ik: ???
Diss (idle): ??? What is the color code? Values should be high, low, or else?
Pwr Out: Power output, maximum energy that the amp can send to the speakers
Dist *nd: distortion, should be minimize.
DF: damping factor, show be as low as possible.
Can you shed some light on my question marks.
2.
Also, 810r is not there for the el34, but somebody suggested to use it as Rk. Why, and what will hapend?
Thanks,
B+ voltage: Measure this voltage on the red wire of the output transformer.
Vp: Plate voltage, measured at the blue wire of the output transformer
Vk: Voltage across the cathode resistor
Ik: Current through the cathode resistor
Diss (idle): Tube plate dissipation with no audio input. Orange values are nearing the maximum dissipation of the tube type and red is nearing the danger zone. However, this value depends on the manufacturer too. Some 6L6 types can handle quite a bit more than the max without plate glow (my JJs do) while others start to glow ever before reaching these values. The part George specs is conservative, though some people have had to go with higher value cathode resistors. The Chinese 6L6 types seem to have this problem. Other types vary as well.
Dist *nd: Try to minimize to some extent. You can see how larger Diss values tend to yield lower distortion numbers. In short, you are trading tube life for better distortion characteristics.
DF: This may or may not be important. It depends on how difficult your speakers are to drive.
Vp: Plate voltage, measured at the blue wire of the output transformer
Vk: Voltage across the cathode resistor
Ik: Current through the cathode resistor
Diss (idle): Tube plate dissipation with no audio input. Orange values are nearing the maximum dissipation of the tube type and red is nearing the danger zone. However, this value depends on the manufacturer too. Some 6L6 types can handle quite a bit more than the max without plate glow (my JJs do) while others start to glow ever before reaching these values. The part George specs is conservative, though some people have had to go with higher value cathode resistors. The Chinese 6L6 types seem to have this problem. Other types vary as well.
Dist *nd: Try to minimize to some extent. You can see how larger Diss values tend to yield lower distortion numbers. In short, you are trading tube life for better distortion characteristics.
DF: This may or may not be important. It depends on how difficult your speakers are to drive.
Hi,
I just measure my B+ and it is 475V. I don't want to keep swapping the Rk, but would like to be able to swap between el34 and kt88.
1. What would be the optimal Rk to be able to do so?
If I prefer one type of tube more than the other:
2. Which values of Rk should I have in my toolbox if I want to run optimally the el34?
3. Which values of Rk should I have in my toolbox if I want to run optimally the kt88?
B+ = 475V is not in the simulation table Tubes & Transformers (bottom)
Thanks
I just measure my B+ and it is 475V. I don't want to keep swapping the Rk, but would like to be able to swap between el34 and kt88.
1. What would be the optimal Rk to be able to do so?
If I prefer one type of tube more than the other:
2. Which values of Rk should I have in my toolbox if I want to run optimally the el34?
3. Which values of Rk should I have in my toolbox if I want to run optimally the kt88?
B+ = 475V is not in the simulation table Tubes & Transformers (bottom)
Thanks
1) I wouldn't go lower than 560 ohm for your EL34s at 475 of B+. That is getting pretty close to the theoretical maximum. To get your actual plate dissipation with your current setup, you can measure the voltage (Vk) across the cathode resistor to get Ik and use the plate voltage to calculate Diss (this assumes triode mode):
Ik = Vk / Rk
Diss = (Vp - Vk) * Ik
2) Since you don't want to run the EL34 much hotter than it is in #1 (assuming your calculations agree), the answer is the same.
3) Some KT88 types can handle more current than others. New Sensor tubes (EH, Tung-Sol reissue, etc) can handle more than the SED KT88, for example. If I were to take a stab at it using the chart, 430 or 390 ohms would get you near the sweet spot.
As far as 475 not being in the chart...you need to look at the 450 and 500 numbers and extrapolate.
Ik = Vk / Rk
Diss = (Vp - Vk) * Ik
2) Since you don't want to run the EL34 much hotter than it is in #1 (assuming your calculations agree), the answer is the same.
3) Some KT88 types can handle more current than others. New Sensor tubes (EH, Tung-Sol reissue, etc) can handle more than the SED KT88, for example. If I were to take a stab at it using the chart, 430 or 390 ohms would get you near the sweet spot.
As far as 475 not being in the chart...you need to look at the 450 and 500 numbers and extrapolate.
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