A New Tube Preamp/Headphone Amp from Douk Audio Needs Your Advice!

[Douk Audio]

Hello all ASR members,

Recently, we are going to design a new tube preamp/headphone amplifier. We know that tube devices are not popular here but we really value your opinions, if you have any ideas or concerns please leave your comments, I will convey all to our PD. Thank you in advance!

Here are some details of its functions:
Audio input: 2 groups of stereo RCA
Audio output: Stereo RCA / 4.4 balanced*1 / 6.35mm single-ended*1
Working voltage of the tubes inside: 200V
Input voltage: DC 15V/3A
Headphone output power: balanced 4.4mm ≥4W; Single-ended 6.35mm ≥2W
THD+N: 0.05%
SNR: ≥95dB

Circuit architecture and some components:
VALVO antique tube ECF801*2;
Class AB TPA6120 headphone amplifier;
ALPS original potentiometer;
WIMA audiophile capacitor;
3-level adjustable gain: high, medium and low
VU meter

What do you think of this tube preamp/headphone amplifier? Any suggestions are welcome!

 

[mhardy6647]

source: http://oldradio.qrz.ru/tubes/russian/short/ecf801.shtml

Are you using both sections of the ECF801 or just one? If so -- I hope it's the triode
Why not just use a good triode (e.g., 6DJ8 twin triode)?

EDIT: On the bright side, it looks like 200 V on the plate of the triode's a reasonable operating condition (and the pentode's, too, for that matter).

source: http://frank.yueksel.org/sheets/030/e/ECF801.pdf

 

[mhardy6647]

Oh, one other thought. please do not put LEDs under the tubes to light them up.

 

[amix]

Please add one more input, but XLR.
But most important, a (Bluetooth) remote control.
Microphony was a big problem with the E6 preamplifier for a lot of people.

 

[JeremyFife]

If you must use tubes - and it's your choice, no issue with that - then aesthetics matter more than normal, I'd have thought. I'm no designer, but that just does not look sexy. I think it has to look better.

 

[SIY]

Class AB TPA6120 headphone amplifier;

So basically the tubes are just for show/marketing.

 

[Purité Audio]

Best place for them.
Keith

 

[amix]

If you must use tubes - and it's your choice, no issue with that - then aesthetics matter more than normal, I'd have thought. I'm no designer, but that just does not look sexy. I think it has to look better.

I the looks are ok. Not like those crazy, industrial like, tube amps like we are used to
This is more modern.

 

[amix]

So basically the tubes are just for show/marketing.

No, as the tubes are for the pre. The solid state is for headphones only.

 

[Douk Audio]

Are you using both sections of the ECF801 or just one? If so -- I hope it's the triode

Hi, yeah, it just use one section of the ECF801, the triode section.

 

[Douk Audio]

Why not just use a good triode (e.g., 6DJ8 twin triode)?

Considering the sustainability of product production, we chose ECF801 composite tube because we have sufficient stock.

 

[Douk Audio]

Microphony was a big problem with the E6 preamplifier for a lot of people.

Hi, the E6 with microphone problem since it adopts direct heated tubes. We will release a new version and use indirectly heated tubes in the near future.

 

[Douk Audio]

On the bright side, it looks like 200 V on the plate of the triode's a reasonable operating condition (and the pentode's, too, for that matter).

Yeah, I have confirmed with our engineer, the ECF801 tube works at 200V, so it is not only for display, but really works.

 

[Douk Audio]

Please add one more input, but XLR.
But most important, a (Bluetooth) remote control.

Maybe it's late to add these, but I will continue to follow up and collect feedback from subsequent customers, and maybe we will make some changes in the next batch. Really thank you for your ideas.

 

[Douk Audio]

Oh, one other thought. please do not put LEDs under the tubes to light them up.

You are right. No LEDs under the tubes for this one.

 

[SSS]

Using just one triode system as a preamp is questionable. Distortion will be built in if not used as a buffer with no gain. Better to use a solid triode/pentode combination circuit with some feedback to get low distortion and low output impedance. And, the ECF801 is a tube for high frequency applications. It is known that these type of tubes are not made or selected for low noise audio. Random 1/f noise may happen.

 

[SIY]

Using just one triode system as a preamp is questionable. Distortion will be built in if not used as a buffer with no gain. Better to use a solid triode/pentode combination circuit with some feedback to get low distortion and low output impedance.

Indeed. You could use this tube for a very low distortion high performance preamp stage, but it would take some actual design work.

 

[amix]

Maybe it's late to add these, but I will continue to follow up and collect feedback from subsequent customers, and maybe we will make some changes in the next batch. Really thank you for your ideas.

Cool! Remote is my No.1 wish for this.