Subminiature tubes/valves for Hi-FI

[pcardoso73]

Sorry for late answer.
Which is I don´t know. I have them in stock but never got around to "play" with them.
@Koifarm has a lot of experience though 😉

No problem ! Thanks for the reply. 🙂

 

[b_force]

@b_force
I tried, initially, to use a 7806 for the heaters but that thing got really, really hot. Then I had the idea of placing an external power transistor to help the regulator, but never got the balance between the two right. The problem is that, if I use a 12V power supply, I will have 6V drop across the 7806 and both valves are pulling 700mA or so. Finally, I gave up and used a buck, which runs cool. 😎

That doesn't surprise me if you were using a 12V power supply.
That is (12-6)*0.7=4.2W of power dissipation.

With a buck converter that is more around 630mW or so.

 

[pcardoso73]

The efficiency of switching converters is amazing!

 

[b_force]

Around 80-90% and these days 500kHz - 1Mhz is also not special anymore.
So very easy to get rid of the noise as well 🙂

 

[egellings]

6cw4 , a nuvistor, is used in hifi. Som other ones will also work well.

They tend to be microphonic.

 

[Koifarm]

Hi,
I have been doing some guitar amps with submiature valves.
But are there subminiature valves that can be used in HI-FI

With 6n16b as voltage stage and fase shifter, 6n30p parallell in PP you can make a 10watt amp

https://www.diyaudio.com/community/threads/small-tube-amp-based-on-6n6p.197840/page-2

 

[b_force]

6n30p parallell in PP you can make a 10watt amp

I only think they will get pretty toasty?

That's the reason why I went to like a 6AK6/EL91/EL95.
They are still tiny, and also only use 150/200mA heater current

 

[pcardoso73]

With 6n16b as voltage stage and fase shifter, 6n30p parallell in PP you can make a 10watt amp

https://www.diyaudio.com/community/threads/small-tube-amp-based-on-6n6p.197840/page-2

The 6N30P has a filament current of 700mA.😱
The one I am using, the 6P30B-R has more power and consumes less, but even that way it heats a lot. It's good for the winter. 😎

 

[pcardoso73]

@b_force
By the way, after what you said regarding the 6021, I had a look to the curves and said holly crap, I really messed up.
Went to ebay again and the seller exchanged that one for a 6AK6. UUUuufff (he didn't have EL91/95).
I will try it, as you suggested, as a replacement for the 6P30B-R which consumes more than 400mA of current.

 

[b_force]

In the UK, ECL80 are also easier to get I think?
Mullard even made some amplifiers with it.

It's basically a EL91 with a little triode.
The triode is not the most linear of all tubes, but fun to play with.
Also not subminiature anymore 😇

 

[pcardoso73]

This is not a datasheet but a nice summary of the specs of some subminiature tubes.
http://www.tubeclinic.com/RuSubMinTubes-Table.pdf

 

[b_force]

Although not very efficient in sense of heating/filament current, you can always cascode two triodes to get a lof more gain of course 🙂

 

[MagicBus]

My take on subminiature tube preamp. Differential, high gain, high current, low distortion. I'm also planning to use SMPS for the heaters one of these days, I already have the converters.

 

[pcardoso73]

@MagicBus
You guys do some serious stuff. Very professional. I am only a hobbyist. 🙂
What's the point in the circuit you do the FFT?

 

[MagicBus]

Assuming you are asking about signal levels, it is 100mV input to 1,9V output.

 

[pcardoso73]

@MagicBus
I was asking if you measured at the output or the grid of one of the valves.

 

[MagicBus]

No, I haven't measured each stage separately. It's the complete preamp input to output. Otoh, it can be connected as a SE but it will do the conversion to balanced anyway.

 

[as_audio]

If you call this a preamp where is the volume control ? Thanks

 

[pcardoso73]

So, if I have a complete power amp where do I measure the FFT? At the end of the preamp, output of the transformer(speaker)?

 

[MagicBus]

If you call this a preamp where is the volume control ? Thanks

No volume control, no input selector in any of my preamps. 🙂 My entire music library is digital and I use the digital volume control.