Hi,
I'm new here, I've read a lot of good stuff on threads here before.
I've been doing glassware amplification for about three years now, and i've come to thepoint there i'm learning how to design proper output stages.
Up till now, I've been learning all I need from education+diy. preamps, power supplies and triode power ( SE/PP) are things i can design already. at least they work
So, I finally decided to make an account and actually ask a question.
I'ts about Pushpull Pentodes. I've already got a nice amplifier so now i'm working on an amp that doesn't only sound nice, but also looks nice- better than this: (i'm the engineer there, too)
Circuits Online - Forum - Show your projects! Part 26.
I was aiming for a mercury rectifier, a nice glowing regulatortube such as OA3 to 0D3. that's all settled and fine. For output tube i'd like a nice topcap tube, but not too expensive. the budget is limited
Ive been loking around and my eyes fell on 2E26 tubes. I really like the looks ( and the price tag) on them. the datasheet mosty supplies data for Eg >0 but I dont want to go there.
The aim is a 15W amplifier. with my calculations I can get nowhere near there. but it should be easily possible with htis tube! i heard someone calling "14W SE" but that must be a little on the high side.
So, what i'd like to know, what kind of values to expect. Ra~a, Vb+, Eg, Iadc.
There 'll be a big electro market soon and i'd like to go shopping
my guess is something like Pda +/- 7W, Va = 250 to 350V, but then I don't know what Ra~a i should choose.i've no experience with these tubes.
I'll gladly hear your thoughts on this! ( & please tell me whenI'm doing things wrong)
I'm new here, I've read a lot of good stuff on threads here before.
I've been doing glassware amplification for about three years now, and i've come to thepoint there i'm learning how to design proper output stages.
Up till now, I've been learning all I need from education+diy. preamps, power supplies and triode power ( SE/PP) are things i can design already. at least they work
So, I finally decided to make an account and actually ask a question.
I'ts about Pushpull Pentodes. I've already got a nice amplifier so now i'm working on an amp that doesn't only sound nice, but also looks nice- better than this: (i'm the engineer there, too)
Circuits Online - Forum - Show your projects! Part 26.
I was aiming for a mercury rectifier, a nice glowing regulatortube such as OA3 to 0D3. that's all settled and fine. For output tube i'd like a nice topcap tube, but not too expensive. the budget is limited
Ive been loking around and my eyes fell on 2E26 tubes. I really like the looks ( and the price tag) on them. the datasheet mosty supplies data for Eg >0 but I dont want to go there.
The aim is a 15W amplifier. with my calculations I can get nowhere near there. but it should be easily possible with htis tube! i heard someone calling "14W SE" but that must be a little on the high side.
So, what i'd like to know, what kind of values to expect. Ra~a, Vb+, Eg, Iadc.
There 'll be a big electro market soon and i'd like to go shopping
my guess is something like Pda +/- 7W, Va = 250 to 350V, but then I don't know what Ra~a i should choose.i've no experience with these tubes.
I'll gladly hear your thoughts on this! ( & please tell me whenI'm doing things wrong)
Anode topcaps should be avoided if there are children or mobile pets in the house, unless you put a grounded cover over the valves. My guess is that you are one of those people who likes to display your valves, so top caps are best avoided. Insulated connections are available, but they can be large and ugly and a child could easily pull them off.
Mercury rectifiers are also best avoided. They emit UV, and can be fragile. They also contain mercury.
Mercury rectifiers are also best avoided. They emit UV, and can be fragile. They also contain mercury.
The 807 is the best top cap valve for your purposes. Cheap and readily available. Better than the 2E26.
There are Quads at unbelievably low prices from Russia.
Regulator valves add a nice touch of colour to the amp, I use the VR150.
Mercury rectifiers are best avoided for the reasons mentioned.
Put it up on a wall shelf and use ceramic top caps and all is well with the world.
Shoog
There are Quads at unbelievably low prices from Russia.
Regulator valves add a nice touch of colour to the amp, I use the VR150.
Mercury rectifiers are best avoided for the reasons mentioned.
Put it up on a wall shelf and use ceramic top caps and all is well with the world.
Shoog
Last edited:
Well, I'm a little young to have kids. i'll be 19 soon.
DF96, spot on! I'm a big an of nice lights such as regulators, magic eyes, VFD stuff, nixies and all other shiny and awesome glassware. strangely I don't like that 815 martian tube. But i'll definitely look at the designs made for them, I see the similarities.
also- how siilar is it with a CV415, except for the Pda?
I thought that the glass absorbed the UV? well, if i was wrong, i think there are too many dangers now. it'll stay in the cabinet, but i might have a 80 rectifier lying around here. It can replace the 82. marcury recitifiers tend to contain mercury...
VR150- the 0D3, the purply blue one? the only one of the four from that series I don't own yet. And how do you know the tube contains barium?
Well, I've played around with 807. Not bad. but I have limited space also and the tube can't extend over the base like the coke bottles. And the Pda is 25 watts, isn;t that a massive overkill? besides, the 2e26 is about 40 minutes on by bike away and about 3 euros per NOS tube. and it fits in an octal, hich i have plenty. else i'll have to get UX-5 bases, which I don't have in stock, and get the tubes from russia. But when find some at the electro market, i'll probably buy them.
But, still, how about this: anode voltage 300V, Ra~a of 7K, and an anode current of 30mA. (Eg -20V). quite similar to the CV415.
With my calculations I also end up at about 15watts...right?
DF96, spot on! I'm a big an of nice lights such as regulators, magic eyes, VFD stuff, nixies and all other shiny and awesome glassware. strangely I don't like that 815 martian tube. But i'll definitely look at the designs made for them, I see the similarities.
also- how siilar is it with a CV415, except for the Pda?
I thought that the glass absorbed the UV? well, if i was wrong, i think there are too many dangers now. it'll stay in the cabinet, but i might have a 80 rectifier lying around here. It can replace the 82. marcury recitifiers tend to contain mercury...
VR150- the 0D3, the purply blue one? the only one of the four from that series I don't own yet. And how do you know the tube contains barium?
Well, I've played around with 807. Not bad. but I have limited space also and the tube can't extend over the base like the coke bottles. And the Pda is 25 watts, isn;t that a massive overkill? besides, the 2e26 is about 40 minutes on by bike away and about 3 euros per NOS tube. and it fits in an octal, hich i have plenty. else i'll have to get UX-5 bases, which I don't have in stock, and get the tubes from russia. But when find some at the electro market, i'll probably buy them.
But, still, how about this: anode voltage 300V, Ra~a of 7K, and an anode current of 30mA. (Eg -20V). quite similar to the CV415.
With my calculations I also end up at about 15watts...right?
Last edited:
I have another question, why do the grid-to-ground resistors have to be so small? any risk of oscillation if I make them too large, like 100K? That way it'll be easier to drive them, I do not intend to drive the grids positive anyway. else i'll have to fool around with cathode followers and i'm not much of a fan of those. or opamps...brrr.
Result
I tried and i did it! The 2e26 tube is a nice and inexpensive tube, and the new amp is a real improvement to my setup.
The final result has 2c51 drivers and a 2e26 output tube, with VU-eyes and a 0D3 regulator. I sweeped the amp and the gain is constant between 15Hz and 30KHz, and lower elsewhere. The tube produces the 5W the datasheet promises with only a little distortion. But I don't need the full 5W and the distortion is very low at normal levels.
https://www.dropbox.com/sh/sf6t8ruowr22343/jyvgdjlm4n
I tried and i did it! The 2e26 tube is a nice and inexpensive tube, and the new amp is a real improvement to my setup.
The final result has 2c51 drivers and a 2e26 output tube, with VU-eyes and a 0D3 regulator. I sweeped the amp and the gain is constant between 15Hz and 30KHz, and lower elsewhere. The tube produces the 5W the datasheet promises with only a little distortion. But I don't need the full 5W and the distortion is very low at normal levels.
https://www.dropbox.com/sh/sf6t8ruowr22343/jyvgdjlm4n
let's try again Link
Well, I'm pretty happy so i'm not going to experiment with a new schematic. Also because the amp is absolutely quiet- absolutely no 50Hz or 100Hz hum! Only if it comes from the music inputs ofcourse.
I haven't experimented with screen drive yet, it does sound interesting but also a little difficult. By the time I want more power, i'll probably just make a new amp, much more fun
LinkWell, I'm pretty happy so i'm not going to experiment with a new schematic. Also because the amp is absolutely quiet- absolutely no 50Hz or 100Hz hum! Only if it comes from the music inputs ofcourse.
I haven't experimented with screen drive yet, it does sound interesting but also a little difficult. By the time I want more power, i'll probably just make a new amp, much more fun
How is the 2E26 working? I am in possession of quite a few of these and want to make sure they’re safe to use/sell. Please let me know how that worked out for you.let's try again
Well, I'm pretty happy so i'm not going to experiment with a new schematic. Also because the amp is absolutely quiet- absolutely no 50Hz or 100Hz hum! Only if it comes from the music inputs ofcourse.
I haven't experimented with screen drive yet, it does sound interesting but also a little difficult. By the time I want more power, i'll probably just make a new amp, much more fun
2E26 is pretty similar to 6V6 in terms of optimal operating points, with the exception of lower max screen voltage (200 V compared to 285 V of 6V6), so a circuit should be modified accordingly. Triode-connected, Ua of 300 V is OK.
I like the directly-heated equivalent, 2E24. It sounded better to me than 6V6 in a pentode amplifier. Ale Moglia of Bartola Valves has information on triode-connected 2E24. A little weak as power triode, but good triode driver.
I like the directly-heated equivalent, 2E24. It sounded better to me than 6V6 in a pentode amplifier. Ale Moglia of Bartola Valves has information on triode-connected 2E24. A little weak as power triode, but good triode driver.
Wow, you can go all the way to 300v on a 2e26 in triode even though the screen is only rated for 200v? I might try that out in a push pull amp. I have a zillion 2e26 tubes and have always liked how the looked lol.