Audio Note Kits L3 Line Pre-amplifier

Due to the recent move to Vienna, Austria, I needed to settle in first before I could get back into my hobby as DIY audiophile. It took a long time to get started on assembling my new pre-amp, Audio Note Kits' (AN Kit) L3 Line Preamp (L3 Line) which sat in pile of boxes for some time. It is finally done, and in my system since March 2012.

 

I was inspired by many audiophiles on the internet through their websites and bulletin board exchanges. I also received many valuable advice from those who I “met” on the web. I am putting together this page to share my experience of building this kit as my small contribution back to the audiophile community on the internet.

 

For this L3 Line, I am especially grateful for the assistance, advice and information that I received from the discerning ear. Many of us may know his moniker on AudioAsylum. Yes, he can be quite opinionated at times but the advices he gave me were very appropriate and his customized components such as his Power Supply Unit (PSU) were first rate that yielded excellent performance improvement over stock components for a very reasonable cost. His website is: www.thediscerningear.com.

 

October 2012

 

Audio Note UK HiB C-core output transformers
Audio Note UK HiB C-core output transformers

Adding the pre-amp resulted in a major improvement to my system. I hear more details from recordings that I did not hear before. Bass is much fuller and authoritative but not boomy with added definition. Timbre of acoustic instruments sounds very natural closer to real. And vocals now sound wonderfully human even from digital source. Constantine Soo wrote: “For me, the M3 dispelled the stubborn notion that all preamps will degrade signals because of the extended signal path represented.” in his review of Audio Note UK’s M3 preamplifier. (StereoTimes, 30th November 2001, http://www.stereotimes.com/amp113001.shtml) Moving from AN Kit’s Kit 1 integrated amplifier, I cannot agree with him more. 

 

Below, I have listed changes and upgrades that I installed in my L3 Line. I hope these may give you some ideas :).   Please visit AN Kit’s website for further information on stock configurations.

 

 

Tubes/Valves

I relied on my experience from testing different tubes for the AN Kit DAC 3.1 Signature that I owned for several years to choose the tubes for the L3 Line. They share the same PSU and 5687 line stage boards. At this point in time, I have settled on the following tubes:

  • 5687 – Cryogenically treated NOS Tungsol JTL5687WA from Pearl Cryo Valve
  • ECL82/6BM8 - Cryogenically treated NOS Svetlana from Tubeman.com
  • 6X5 - Cryogenically treated NOS RCA from Tubeworld.com

To my ears, cryogenically treated (cryoed) tubes sounds more extended and open that throws larger sound stage without being bright or thin. They also gave a better sense of pace and rhythm with improved dynamic. For instance, I have tried non cryoed Tungsol 5687 and RCA 6X5 from the similar vintage. The difference was clearly noticeable. Switch back to non-cryoed tubes after using cryoed tubes for a while, my impression of the sound was dull, slow and were not as engaging.

 

As to the cryoed NOS Tunsol 5687s, I tried the ones from Tubeman.com, Tubeworld.com, and Peal Cryo Valves. The tubes from Tubeman.com were excellent with very reasonable price. Not surprisingly, when I decided to buy more they were already sold out. Tubeworld.com and Peal Cryo Valves does supply very good vintage cryoed tubes, though at a cost.  Both sounded equally good, but I chose Pearl because to my ears, they had less tube to tube variability and they provide detailed information on test processes, detailed test results, and with clearly indicated the tube’s grade based on the quantified noise level differences. Detailed information on Perl Cryo Valves can be found here: www.pearl-hifi.com

 

For the ECL82/6BM8, I have also tried NOS Matsushita, NOS Telefunken, and non-cryoed Svetlana. The cyoed Svetlana outperformed others in the way I described above. I have tried non cryoed RCA 6X5 tubes of different vintage as well as few other NOS tubes of different US brands but cryoed RCA were head and shoulders above the others. When I tested the tubes for the PSU, I was very surprised to hear the significant difference in sound from switching the tubes. It was much more than I anticipated.  I felt, for some reason, cryogenic treatment had more effect on the tubes used in the PSU than any other areas.  Further, rolling the ECL82/6BM8 (used as a HT regulator) had more effect based on what I heard than the rolling of the 6X5 rectifier tube.

 

At this time, Tubeworld.com seems to be the only vendor who offer cryoed rectifier tubes.  Given such an effect on sound, I hope other vendors will follow suit. 

 

5687 Line Stage
5687 Line Stage

 

5687 Line Stage Board

 I applied the typical Audio Note parts upgrades to the line stage board. All the resistors are Audio Note UK's tantalum resistors. 2W rated resistors are used in the signal path and the rest are 1W rated resistors. For the decoupling electrolytic capacitors, I used Black Gate N series. I was fortunate to purchase these Black Gates while they were still in production. Back then, I had only hoped that I will get to build L3 Pre and the L3 phono amp some day. For the coupling capacitor, I used Audio Note UK's  Silver Foil Mylar capacitors. As you can see, I decided to go all the way in terms of the parts upgrade here :).

 

AN UK Silver Foil Mylar Capacitor for Coupling
AN UK Silver Foil Mylar Capacitor for Coupling

By error, I received the PCB instead of the hard-wiring board that I ordered. I thought of contacting Brian of AN Kits for a replacement but I did not feel like waiting so I decided to build the PCB version. To my surprise, compared to the hard-wired 5687 line board from my DAC, there were no significant differences in sound. Building hardwired board is more fun and interesting but the PCB saved me a lot of time. So if you are a prospective buyer, this is something to consider.

 

 

PSU Board
PSU Board

 

Power Supply is the customized M2X PSU by TheDiscerningEar. This is a reasonably priced upgrade that resulted in notable sound improvements over the stock unit. It was well worth my investment. Most notable feature is the use of 0B2 tube in place of zaner diode with carefully selected and matched parts. My PSU uses, AN UK’s Cu Mylar in Oil film capacitors, and Black Gates and Panasonic electrolytic capacitors.

 

B+ power is supplied to the line board with the choke de-coupling. Between the choke and the line board, I added a Continental Capacitor’s “Type-A” oil filled capacitor. I used this capacitor in the AN Kit’s L1 Phono amp and I felt that it yielded a notable improvements. Addition of this capacitor took out a small amount of brightness/harshness that remained in the sound without losing details or making the sound “slow.” It may sound like a small improvement but this was the kind of change that elevates an equipment to the next level. It is large in size but I whole heartedly recommend the use of this capacitor in the PSU if space allows. This is available from Parts Connexion.

 

 

Continental "Type A" oil filled capacitor
Continental "Type A" oil filled capacitor

 

Other

Volume control: DACT Attenuator. This is a gift from a very good audiophile friend mine from Osaka. He had purchased Weiss AT202!

 

Input selector switch: GoldPoint 2P-6D-2D. With PCB attached for connection, it is very easy to use much better than DACT or other versions of ELMA switches.

 

RCA connectors: Audio Note UK’s silver plated connectors.

 

Wiring in the signal path: VH Audio UniCrystalOCC 24 AWG with Airlock Insulation and VH Audio UniCrystalOCC 24 AWG with Cotton Insulation

 

Wiring for the power: DH Labs silver plated copper wires with Teflon insulation (18AWG.)  I've used the same wire in 16 AWG in my earlier project but it was bit too much to handle. Available from Parts Connexion.

 

Goldpoint selector switch
Goldpoint selector switch

 

Well, that's about it for now, but stay tuned.  More tweaking to come!  Happy building!

 

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