• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Douk HiFi 6N3 Vacuum Tube Preamp Review

Rate this product:

  • 1. Poor (headless panther)

    Votes: 117 66.1%
  • 2. Not terrible (postman panther)

    Votes: 43 24.3%
  • 3. Fine (happy panther)

    Votes: 11 6.2%
  • 4. Great (golfing panther)

    Votes: 6 3.4%

  • Total voters
    177

mhardy6647

Grand Contributor
Joined
Dec 12, 2019
Messages
11,212
Likes
24,171
Is the Headless PinkPanther taking some time off? Or is this your way of saying that even the PinkPanther only needs one arm to operate retro thingy?
Maybe it's the Boss's (i.e., @amirm's) sly allusion to the old vacuum tube/high voltage maxim: when taking HV measurments, always keep one hand in one's pocket, to reduce the chance of conducting HV DC from hand to hand and through the heart.

Just like Alanis Morissette:


:cool:
$110? I’m surprised it worked at all!
Yeah, but...

These were on sale yesterday & the day before for $29 (USD).

No vacuum tube rectifier, though. ;)

Weird, when you read reviews on homecinema.fr in France, on douk audio P1, folks are raving about these preamps
Yeah, but comedian/actor Jerry Lewis was is also venerated for his art in France.
 
Last edited:

MadMan

Active Member
Joined
Jun 27, 2020
Messages
117
Likes
134
Of course it's important to use a standardized 2V level for tests, but I wonder whether at a lower input level the output is better matched? So there are many DACs that have volume (output level) control. It would be interesting to see what input value gives a good channel volume match.
 

jsm

Member
Joined
May 27, 2020
Messages
36
Likes
22
please @amirm , as you seems to be in a tube mood, give a try to the Little Bear phono pre T11 or T10 :), better reputation on forums than the douk
 

pseudoid

Master Contributor
Forum Donor
Joined
Mar 23, 2021
Messages
5,116
Likes
3,416
Location
33.58 -117.88
please @amirm , as you seems to be in a tube mood, give a try to the Little Bear phono pre T11 or T10 :), better reputation on forums than the douk
Why not purchase one and drop ship it to the Master of the PinkPanthers?
Recommend contacting him to confirm FIRST.
 

jsm

Member
Joined
May 27, 2020
Messages
36
Likes
22
Why not purchase one and drop ship it to the Master of the PinkPanthers?
Recommend contacting him to confirm FIRST.
I'm in France... I'm sure there is an american member, using this one ;). He already knew that, I told him already during another conversation in MP (with Amir). It's like the suggestion of Sunflower redux speakers (DIY), I've done these but I can't ship it.
 
Last edited:

Jim Shaw

Addicted to Fun and Learning
Forum Donor
Joined
Mar 16, 2021
Messages
616
Likes
1,159
Location
North central USA
Send one of these to any 70+ y/o hifi reviewer in NYC. They'll be sold out by the following morning.
 

egellings

Major Contributor
Joined
Feb 6, 2020
Messages
4,004
Likes
3,244
The charm of tubes is doing home brew preamps and amps. I would never buy one.
 

gino1961

Senior Member
Joined
Dec 19, 2018
Messages
428
Likes
139
... By standards of people who want "tube sound," this box at least delivers on that promise with copious amount of second harmonic.
As Forrest Gump said in the movie, "that is all I've got to say about that!"

----------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

Hi if to get a good amount of 2nd order distortion is the goal there could be a much easier way to obtain it.
I am not an expert in electronics but a one bjt single ended no feedback line preamp shoud provide a distortion spectrum very similar to this one under review. I mean should provide a good 2nd order distortion with minimal cost.
The fact that many people like this is confusing me. I have always thought that the lower the noise and distortion the better the sound.
On this basis i have just placed an order for the amazing Topping L30 (>2012 this time) to try it mostly as a line preamp. I am very curious.
Thanks a lot for the always valuable reviews.
Kind regards, gino
 

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
one bjt single ended no feedback line preamp shoud provide a distortion spectrum very similar to this one under review. I mean should provide a good 2nd order distortion with minimal cost.

Using a J-FET with some local feedback... yes
BJT... nope.. has another harmonic spread.
For distortion to become objectionable in music it would have to be substantial.
For lower amounts of distortion to be euphonic I would like to see some serious blind testing.

It does not cost much to get distortion numbers low enough to be inaudible.

When one is curious buy low distortion gear (speakers/headphones may be the bottleneck) and use the 'distort' program from @pkane.
Use ABX tester and ensure the output levels between the compared files is within 0.1dB (1%)
 
Last edited:

gino1961

Senior Member
Joined
Dec 19, 2018
Messages
428
Likes
139
Using a J-FET with some local feedback... yes
BJT... nope.. has another harmonic spread.
For distortion to become objectionable in music it would have to be substantial.
For lower amounts of distortion to be euphonic I would like to see some serious blind testing.

It does not cost much to get distortion numbers low enough to be inaudible.

When one is curious buy low distortion gear (speakers/headphones may be the bottleneck) and use the 'distort' program from @pkane.
Use ABX tester and ensure the output levels between the compared files is within 0.1dB (1%)
Hi thank you very much indeed for your kind and valuable reply
I read somewhere that even order distortion can be nice not so odd order one
And i know of many well received preamps using fets (like Conrad Johnson for instance but also the old Mark Levinson)... maybe this could be the best option if one wants some embellishment to the sound
And with much less issues than with tubes
One of the very high end line preamps the Blowtorch by John Curl should use a parallel of single fets no feedback
John Curl is a very famous designer in the high end field He says that simpler circuits have more possibilities to sound nice Like Nelson Pass
Thanks a lot again, gino
 
Last edited:

pseudoid

Master Contributor
Forum Donor
Joined
Mar 23, 2021
Messages
5,116
Likes
3,416
Location
33.58 -117.88
Using a J-FET with some local feedback... yes
BJT... nope.. has another harmonic spread.
Can "we" at least agree that NO amount of 'feedback' (positive or negative) or added 'distortion' (odd or even) is desirable... yet sometimes becomes necessary, due to other mitigating issues in the design/implementation of circuits to process audio???
I detest both to a big degree (necessary evil) but my design dislikes also includes input-to-output audio signal processing of any kind... including digital EQ, even for room corrections.
 

solderdude

Grand Contributor
Joined
Jul 21, 2018
Messages
15,891
Likes
35,912
Location
The Neitherlands
Can "we" at least agree that NO amount of 'feedback' (positive or negative) is desirable...

Feedback is essential and desirable as it linearizes the transfer function and thus reduces distortion so it is highly desirable.
Only when amplification components were to have linear transfer functions (which none have) feedback would not be needed.
 

egellings

Major Contributor
Joined
Feb 6, 2020
Messages
4,004
Likes
3,244
Even then, you'd still want to use feedback to lower the output impedance of an amplifier, if for no other reason.
 

pseudoid

Master Contributor
Forum Donor
Joined
Mar 23, 2021
Messages
5,116
Likes
3,416
Location
33.58 -117.88
We all know the virtues of feedback, but look the other way regarding its drawbacks!
Yet, looking at it from a different perspective; any feedback (for any reason) is a band-aid fix to deal with the shortcoming of any design and its implementation.
An emitter-follower mandates major feedback dump but it does not make the best amp design due to that dump.
It has always been a better design choice w/decreased gain; rather than increased NFB...
 

LTig

Master Contributor
Forum Donor
Joined
Feb 27, 2019
Messages
5,760
Likes
9,442
Location
Europe
In fact it's almost impossible to use no feedback at all as most amplifying devices have to much amplification in the first place (triodes being an exception). So when lay people talk about no feedback they in fact mean no global feedback over more than one amplification stage.

Of course any electronics book which covers negative feedback contains the calculation which proofs mathematically that global feedback over N amplification stages is more effective in reducing non linearities then using only local feedback in each of those N amplification stages...
 
Last edited:

Gremlins

Active Member
Joined
Apr 25, 2021
Messages
159
Likes
83
Hi community
I tried the douk audio P1 tube preamp

Man, this thing is crap standard, noisy in the tweeters and overall sound definitely outside hifi standards .. ok its cheap, but this thing is not at level for audio listening if you want minimum quality listening

Also, i had to change my first purchase on amazon. First one i received had a big problem on level matching beetween right and left, so i send it back in exchange. Second one didn't had the problem, but trully was i disapointed

I finally send it back to amazon
 
Joined
Jun 12, 2023
Messages
13
Likes
6
Location
FRANCE
This is a review and detailed measurements of the Nobsound Douk Hifi 6N3 Tube Preamplifier. It is on kind loan and is on sale on Aliexpress for US $110.

This is a two box package:

View attachment 170014

Large volume control is nice to have. The amplifier is based on a pair of 6N3 tubes as indicated in the name. There is also a 6Z4 rectifier tube to really make the heart of tube lovers glow. I can't tell the branding on either tube.

In a nod to make this a "high-end" amplifier, an external power supply box is provided as you see on the right. Shame it doesn't look anything like the amplifier itself.

View attachment 170015

Nobsound Douk Hifi 6N3 Measurements
Given the unbalanced input, we follow my standard protocol of feeding the unit 2 volts, and adjusting the volume until we get the same voltage out ("unity gain"). This is what we get:
View attachment 170016

Sadly this lands the potentiometer in the region where it loses fair bit of channel matching so the output is different in one versus the other (2 volts vs 1.7). I could not do much about the mains hum which you would hope would be better taken care of in an external box. That doesn't impact SINAD though as it is dominated by the 2nd harmonic to the tune of -55 dB. While by our standards this is horrid, folks buying tube amps kind of expect this and it is good that we essentially have that one component of distortion (third harmonic is down to -95 dB).

Unit warmed up fast enough:
View attachment 170017

Mains and power supply noise likely contributes to the lackluster signal to noise ratio:

View attachment 170018

Crosstalk was not good:
View attachment 170019

Frequency response was nice though:
View attachment 170020

Before I forget, this thing has tons of gain. I think I measured about 22 dB. With that comes large rise with distortion:

View attachment 170021

Power supply noise is the main frequency dependent distortion and noise:


View attachment 170022

Multitone test shows that if you are perceiving "resolution," it is not because of the amplifier is any good with that:


View attachment 170023

Reducing that to two tones, we get similar results to our THD test:
View attachment 170024

Finally here is our channel matching test of the volume control:
View attachment 170025

Il aurait été préférable d’avoir moins de gain ou un commutateur de gain afin de pouvoir actionner le contrôle du volume là où il est plus adapté entre les canaux.

Conclusions
Selon nos normes de transparence en ce qui concerne le bruit et la distorsion, le Douk 6N3 est de la camelote. Selon les normes des personnes qui veulent un « son à lampes », cette boîte tient au moins cette promesse avec une grande quantité de seconde harmonique. Comme l’a dit Forrest Gump dans le film, « c’est tout ce que j’ai à dire à ce sujet ! »

----------
Comme toujours, les questions, commentaires, recommandations, etc. sont les bienvenus.

Tous les dons sont très appréciés en utilisant : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/


Since this is a cheap tube preamp, its performance is pretty decent overall, with the exception of crosstalk. The multitone test shows stable behavior across the entire audio band and true transparency of around 60 dB, which is pretty good for tube technology. But it is still too far behind other technologies... I also award it a postman panther.
 
Top Bottom