Portable Tube DAC: Need recommendation

[stocktrader200]

you could use 12AX7 and transistor current buffer to achieve that gain with common parts.
you get a bonus natural rolloff at 25 - 30 khz as well

 

[MarcelvdG]

ES9018 USB DAC - Hi-Resolution System
I found a guy on the net who build a tube dac around the same chipset I’m going to be using (ESS9018). How can I get around from using big juicy transformers ? My main challenge at the moment.

Find yourself higher impedance headphones with high sensitivity?

 

[MarcelvdG]

This link

Gerard's Blaupunkt Omniton

contains information on a tube hearing aid from around 1950, including its schematic. It used a transformer for a dynamic earphone. For a crystal earphone, the transformer was used as a choke. Apparently the 22.5 V batteries are still available.

 

[alexfrenchi]

you could use 12AX7 and transistor current buffer to achieve that gain with common parts.
you get a bonus natural rolloff at 25 - 30 khz as well

And that could be used instead of regular transformer's ?


@Marcelvdg:
The dac will be used on a Audeze LCD3 (headphone), high impedance but relatively low sensibility. They need some juicy amp.

 

[alexfrenchi]

Miniature Tube VS Juicy Tube

Have you experienced difference between miniature tube (for example: 6N16B-V) VS Some good juicy Russian 6SN7 tube ?

The signal quality is noticeable? I presume you won’t be able to have a solid low end and a good overall balance over the frequency spectrum on some miniature tube ?

PS: The use is for a high-end headphone dac/amp.

 

[Lingwendil]

Looking at the curves on the datasheet will show that the 6N16B will perform excellent when implemented correctly, if going for voltage amplification and loaded correctly. It's one of the better tubes around and is a real gem, also long life and affordable. I wouldn't hesitate to use one here personally, although I wouldn't really want to do a portable tube DAC ("transportable", yes, portable, eh...) If I were to do so I would look into running the tubes at around 150 volts, using a switchmode power supply, very well filtered, and a diamond buffer type of output stage. Using any of the regular "cathode" types of tubes will be inefficient due to heater power, and I'm not experienced enough with battery types of DHT tubes to comment further there. The physical size of the tube has absolutely nothing to do with the frequency response or "low end" however many miniature tubes are made for harsh environment use, and are more rugged than the usual types. Very versatile and usually high quality.

The only way to do what you want in any reasonable fashion for portable use is going to be a hybrid scheme, tube for voltage amplification, and solid state for output. If you want to go all tube and still have high fidelity you will need more tubes, output transformers, or some other sort of compromises in order to make it work.

 

[alexfrenchi]

Cool, so you suggest running the tube a little hot (150Volts), they say 100V+ on thedatasheet. Would result in running the tube slightly on overdrive ? Those tubesare made for that, especially for audio junkies like us haha

+What doyou mean by switch mode power supply ? +Diamondbuffer output stage ? +How can Iskip cathode, this is essential.

PS: Waslooking into Schematic’s with mini-tubes and fell on those guy’s, looks likethey used the same method as you suggested earlier on the Thread: https://www.head-fi.org/showcase/alo-audio-continental-dual-mono-dac-amp.20874/reviews

 

[Lingwendil]

Plate voltage will only be 50-60% of the supply voltage, so no overload here.

Switch mode power supply- high voltage boost converter... Something like this- High Voltage DC-DC Boost Converter ZVS Voltage Regulator 8-32V 12V to ±45V-390V 932846359175 | eBay

 

[alexfrenchi]

Any tip's/walk around on running two 100Volts tubes with a small portable battery ?