Super cheap triode amplifier

[jackinnj]

6360's are about a dollar apiece. I've not seen a paralleled strapped curve, so this is just a guess:

An externally hosted image should be here but it was not working when we last tested it.

 

[aldovan]

How did you drive/bias the 3c24 exactly. I'm gathering parts for an amp using the 4E27. Yes, for the red plate.

Normally is used a tube in cathode follower or a transformer for driver this transmitters tubes in class A.
I have a idea of use a transistor BU208 in emitter follower with good results.
The BU208 support high voltage and the emitter is connect direct to tube grid.

Aldovan

 

[aldovan]

Fivre 25L6GT

Friends

Look this amplifier schematic playing a Fivre 25L6GT in triode mode:
Fivre 25L6GT in triode mode - YouTube
Very nice sound !

Aldovan

 

[iko]

Nice! But I like your cardboard speakers even more! 🙂

What's up with you never showing schematics. Afraid to share your discoveries?

Edit: just kidding!

 

[aldovan]

But have the schematic in the post....
You want the schematic of this 3C24, too ?

 

[aldovan]

The schematic of this 25L6Gf amplifier is the same only wirh 25V more for
25L6GT header

 

[tinitus]

Let me guess, diyaudio.com? 😀

guess again 😀

 

[tinitus]

noone using a 'universal' seperate preamp/gainstage, with both SE and balanced output/drive ?
I know buffers are more popular, but ....?

 

[iko]

But have the schematic in the post....
You want the schematic of this 3C24, too ?

I'd like to see only how you drive the output tubes. I'll play with something like that myself, maybe. There's a lesson to be learned in all of this.

 

[aldovan]

I'd like to see only how you drive the output tubes. I'll play with something like that myself, maybe. There's a lesson to be learned in all of this.

No problem.
I working now, but when I arrival in my house, I will post my simple driver solution...not the best, but work fine... 🙂

Aldovan

 

[tcqanh]

No problem.
I working now, but when I arrival in my house, I will post my simple driver solution...not the best, but work fine... 🙂

Aldovan

waiting for your schema with 3C24.

some tubes are born to be able to play with pink plate 😉 . maybe 3C24 is in that group

 

[MrCurwen]

3C24 has a shorter lifespan if plate is not operated red.

 

[Burnedfingers]

I'd like to see only how you drive the output tubes. I'll play with something like that myself, maybe. There's a lesson to be learned in all of this.

I hope that lesson doesn't include switching to cardboard speakers. I can just feel the bass😉

 

[aldovan]

3C24 has a shorter lifespan if plate is not operated red.

Yes, the Eimac and HK recommended use with red plate because the plate work as a "getter" and absorb the oxygen.

 

[aldovan]

I hope that lesson doesn't include switching to cardboard speakers. I can just feel the bass😉

No, in the video I play a simple BR with a Utah alnico speaker:
https://www.youtube.com/watch?v=67J3lIg7X5Q&feature=channel&list=UL

 

[aldovan]

I think he was just kidding.

Me like the red plates! Big time!

The 15E play fine, too.
My problem is find the socket...
In the video I use a ceramic bridge for power electric use.
https://www.youtube.com/watch?v=EAR2Iy6XjXo&feature=relmfu
Sorry for brazilian music....

Aldovan

 

[iko]

I hope that lesson doesn't include switching to cardboard speakers. I can just feel the bass😉

Good way to prototype, I must say! 🙂

 

[iko]

The 15E play fine, too.
My problem is find the socket...
In the video I use a ceramic bridge for power electric use.
https://www.youtube.com/watch?v=EAR2Iy6XjXo&feature=relmfu
Sorry for brazilian music....

Aldovan

The 15E seems harder to find. I have a good stash of 4E27, so that's going to be the output tube for me. Problem is... winding my own output transformer. 🙁

 

[aldovan]

The 15E seems harder to find. I have a good stash of 4E27, so that's going to be the output tube for me. Problem is... winding my own output transformer. 🙁

Why you do not to buy the transformer ?
The Hammond in your country have a line of very good hifi output transformers( but not the 125E or 125SE, please).

Aldovan

 

[azazello]

Tony,

The point I was trying to make is you cannot tell very much about speaker response the lack of detail or any improvements to a circuit when you listening to speakers mounted in a cardboard box.

Aldovan,

Are you talking this transformer?

GXSE10-8-2.5K


10W, single ended tube output transformer for 2.5K Ohms to 8 Ohms.

I have not used this transformer but I do have on hand two Hammond 125ESE's still new and in the box. If I'm going to build this little amplifier I will not depend on it to try to reproduce low frequencies. I will instead hook up a simple little subwoofer. This is why the Hammond 125ESE transformers I have will work fine. They are somewhat limited in their low frequency response and this will mate up fine with a small subwoofer with the frequency at a maximum of 80-100HZ @ 24db crossover.

I'm not agree about LF of H 125SE. 5-6 years ago seller offered this cheap tr. for SE 2A3, 300B, 6L6...I tried 300B with 125FSE and Freeq. band was more 20-30000 Hz with the sames amplitudes /+- 0 db!/. Now I don't believe that band is 70 or 150 - 15000 Hz 🙂. I don't understand seller's deals.....