So you may ask what the benefits of a buffer amplifier are? With a buffer amplifier such as this, it would provide high input impedance and therefore should not offer any loading to the source CD player and as a result it gives in theory the best possible performance. On the output side ideally it should have a low output impedance making it easy to drive any amplifier easily and ensuring virtually perfect linearity. It should also offer low noise, low distortion, a large overload margin and wide bandwidth presenting an extremely clean sound with huge dynamic range. In the end minute audio details should become more apparent and the sound more liquid. Normally buffer amps. do not add amplification and are unity gain, however there are a few other models on the market which have OdB, +2dB and +4dB gain settings, but such buffer stages are at many more times the price then this amplifier - for example the Sound Space Buffer Amplifier.
Another photo of my L-top 6N3 Tube Buffer Amplifier.
So the manufacturer's claimed specs. quoted are:
In Put Power: AC17V 500mA 50/60Hz;
Input Sensitivity:0-5V;
Input Impedance: 100kOhm;
Out-Put Impedance:>200 Ohm;
Gain:0dB
Frequency response:10Hz-25KHz
Minimum THD >0.025%
Signal/Noise Ratio >97dB
RCA Input X1
RCA Output X1
Transformers:AC220V
Power On/Off switch
Fully Non-magnetic Aluminum Cabinet
AC 220V or 110V to AC 17V 1000mA Adaptor built with USA plug Only.
Other audio gear used in the evaluation:
Headphones:
Headphile Darth Beyer V3 Lepoardwood
;Audio Technica ATH-ESW9 Le Luxe Wood Headphones (Hokkaido Cherry Wood);
M-Audio Q40 Studiophile Dynamic Headphones;
Goldring DR-150 (Open Back Dynamic).
Source:Oregon Scientific Music Element CD Player.
Inset photo is the Oregon Scientific Music Element CD Player that I used for the source -
Some basic tube data about the 6N3 and 6N11 Sino tubes:
As mentioned before, the J designation on these tubes means that they were produced in China specifically for military applications and thus would be of higher grade then normal tubes without such designation.
6N3: Data Page
6N11: Chinese PDF Data Sheet
Impressions:
1. The Indeed 6N11 Tube Class A Headphone Amplifier:
The 6N11 tube amplifier has been allowed to burn in for a 6 day period (5 hours per day) before any actual listening was undertaken.
It is apparent why Indeed Hi Fi Labs made this amp. an open design with the acrylic top and bottom plates. The little amp ran quite warm and the open design allowed cooling quickly, an enclosure I think would have cooked the parts quickly to well done without proper ventillation.
As outlined above the amplifier was tested with a number of different headphones and one primary CD source. Even though the amount of burn in time has been rather limited the first impression I received listening to the amplifier was that is was warm and very musical. I suspect that replacing this with a JAN-Sylvania 6DJ8 would further improve the amplifier and these can be had for $15 - 30. The music was very fluid and it was very airy.
It was also quite articulate and tonal balance was quite good also. Bass extension was quite good but I would not call really deep and impact was above moderate. It did not seem laid back or forward. listening at different levels I did not hear any channel imbalances, but at high volumes one would expect to pick up on low level tube noise.
Attack and decay are both quite well balanced. Resolution was above average and some of the most delicate details on some tracks I did not notice with other equipment actually came through. Overall depth and sound stage was well prestented as fairly deep and wide but not the best encountered, this may be a limitation of the tube with low burn in hours and again may yet improve with a tube such aas the JAN-Sylvania 6DJ8. Focus was also fairly decent, the sound overall is quite open.
This is a fairly decent little headphone amplifier.
I did not detect much in the way of noise during quiet passages and the music again was quite fluid and open. I did not detect any sibilance, the M-Audio Q-40 headphones with their in your face characteristics would have quickly detected this.
Even with the bass heavy Darth Beyer V3's I did not experience over bearing bass, the punch was good and nicely controlled and tight without muddiness. I would describe the overall sound as sweet.
2. The Qinpu Q1 + Indeed L-top 6N3 Tube Buffer Amplifier:I first listened to the Qinpu Q1 by itself after the same number of burn in hours, whilst the detail and resolution was good and I did not detect any harshness, it was a very wee bit sibilant. There was something about it, it did not seem as spacious as the 6N11, but would this improve further with burn in still remains to be seen.
Pace, Rhythm and Timing was actually on par with some more expensive amps. But there seemed something lacking - realness and naturalness seemed to be amiss. It was also a tab bit grainy and imagery and focus whilst good was slightly below that of the 6N11. On the two tracks -"Didn't know I was looking for love" by Everything But The Girl as well as "Ancient" by Jeanne Newhall, I did not feel the fluid flow of the music as much as I did with the 6N11. I felt the music to be a bit on the dry side and not to my liking.
There was also one annoying issue with the Qinpu Q1, the volume pot was noisy and scratchy and this I felt was a no-no since it is a new piece of equipment and should be using an audio grade pot? Whilst I have not looked inside the Q1, I suspect that this pot may not be of audiophile grade and may need cleaning with a contact cleaner or possibly changing to a better quality alps or matsushita audiophile grade pot as I suspect it may be a low grade pot. I did not notice any imbalances at low or high listening levels. The scratchy pot was most annoying though! This aspect I do take strong issue with and give the Qinpu Q1 a big thumbs down.
Bass extension and impact were fair but not as good as the 6N11, control was however tight. The depth and sound stage although apparent were not as deep and well defined and overall imaging was stronger with the 6N11.
In a nutshell, what was a good sounding amp previously was dwarfed by the sonics of the Class A 6N11.
So what to do, enter the 6N3 buffer amplifier from Indeed. I connected this between source and input of the Qinpu Q1 and let it burn in for the same number of hours before taking a another listen.
It became immediately apparent that after connecting the 6N3 that the highs were more crisp, definition appeared to be better, bass extension and impact seemed better. Depth and sound stage were better defined, deeper and wider. Imaging was also better. So now for a further A-B with the 6N11. After about an hour listening between the two sets, it was still obvious that the Class A 6N11 was still ahead and better sounding but not by such a large margin as before when the Qinpu Q1 was standing alone by itself. The Qinpu was not as dull and became much more musical but I still like the definition, clarity and imaging produced by the 6N11.
Conclusions:In this A-B shoot out, my own opinion is that the 6N11 Class A Headphone Amplifier from Indeed is the winner and I like it's musical qualities. There is plenty of room for experimentation including:
- Changing the 317 regulator to a better grade equivalent from Linear Technologies;
- Tube rolling - change to a JAN-Sylvania 6DJ8 or a Telefunken equivalent (expensive but if you have one around it would be nice to see and hear the difference);
- Experimentation with battery power as a power supply source, this is already slated as a project I will look into;
- Possibily the change of the resistors to some other types like Tokyo Ko-on or RMG types with gold plated OFC leads;
- Change of the electro. caps to some Black Gates or Elna Cerafine etc.
- Can play around with different AC cables on the switching power supply.
The down side of the 6N11 is it is open on the sides and you have to be careful with what you are doing! You need to put some rubber pads on the bottom or it tends to slide about on the desk top. It does tend to run warm.
The Qinpu Q1 - Nice chassis, well bult like a tank. Sound is good but not near the 6N11. The FM tuner is an added plus to the package. It does have speaker outputs so you can hook up to a pair of small speakers if you wish. Runs cool. When connected to the L-top 6N3, the combination yielded much better results then with just the stand alone Qinpu Q1.
The downside of the Q1 - AC cord is not detachable like that on the switching supply of the 6N11, cannot play around with AC cables. Mine had a noisy volume pot - a big no-no ( I will need to look inside at some stage on the construction and components used and cannot comment on the circuit build quality at this stage), I recommend to add an additional buffer amplifier like the L-top 6N3 to open up the sonics.
In conclusion I like the Indeed 6N11 Tube Class A Headphone Amplifier.
Price Reference: (Postage Extra)
- Indeed Hi Fi Labs 6N11 Class A Headphone Amplifier US$79.99
- Indeed Hi Fi Labs L-top 6N3 Tube Buffer Amplifier US$42.00
- Qinpu Q1 Headphone Amplifier from Head Direct US$39.00 (Sale Price!)
Reviewing CD and Tracks: Custom made by ripping songs to FLAC than normalized/burnt via Nero9.
CD Tracks: Esteban - Norwegian Wood; Everything But The Girl - I didn't know I was looking for love; The Corrs - Runaway; Acoustic Alchemy - Mr. Chow; The Verve - Bittersweet Symphony; Willie & Lobo - Amsterdam; Tim Weisberg - Party of One; Sleep Station - There She goes; Seattle Symphony Orchestra - Beethoven's Symphony No. 9 (Scherzo); Sim Riney - What was I to you; Rebecca Pidgeon - Spanish Harlem; Pink Floyd - Dark Side Of The Moon; Mike Oldfield - Tubular Bells.
Additional CD's for auditioning:1. "The Sound of Analog is Back" From Mark Levinson (Red Rose Music);
2. "CD Master I - Direct Master Cut Vinyl CD" Mastering by Mark Levinson;
3. "CD Master II - Direct Master Cut Vinyl CD" Mastering by Mark Levinson;
4. "The Purest Sound-City Folk Songs-Vili" TIS Hong Kong;
5. "Dido" SRS + WIZOR Mastering CD;
6. "The Police" SRS + WIZOR Mastering CD;
7. "Avril Lavigne" SRS + WIZOR Mastering CD;
8. Jeanne Newhall - "Wild Blue";
9. Andrew Lloyd Webber - "Variations"
Notes:- Cable used were all copper OFC cables - home made with gold plated RCA plugs;
- Will listen and compare also using Silver cables at some stage;
- If someone has a Qinpu Q2 and the Indeed 6N11 headphone amp, it would be nice if if they also did an A-B test since the Q2 is a tube amp and such an evaluation would be closer to home;
- Boomy on Head fi will be doing an A-B evaluation between the Head Direct EF-1 Headphone Amp. and the Indeed 6N11 and it would be interesting to see his evaluations and comments.
- The writer has no connections with Indeed or Qinpu whatsoever and the evaluations and based on the writer's own observations and opinions.
Below are some more of my photographs:
