Audio Note Kit Phono amp, Softone/ICL Model 4, Denon AU-1000, K and K LL1678

Vinyl Talk: 2 phono amps + 2 step-up transformers
Softone/ICL Model 4 vs Audio Note Kit Phono amp, Part I
Denon AU-1000 vs K&K LL1678, Part I

Last revised Sept 7, 2011 (round 5 of K&K added)
For round 6 of K&K (change to 30 db gain option), see Part II

Behind this article is a lot of work I have done recently. I am on a roll with my current vinyl gigs, and it has been fun experimenting with everything. More Vinyl Talk are coming!

Introduction: Denon AU-1000
In 1982 Denon released the legendary DL-1000A cartridge (official literature in Japanese. Amazingly, online there is a review from the classical music Gramophone; note that the cartridge is very light, enabling its use on the light SME3009 Series 3 arm (whether that is a good idea is hard to say).

One year later, Denon released another statement product, the AU-1000 step-up transformer (official literature in Japanese), to partner the DL-1000A. Look at that curve, impressive to say the least, and probably hard to duplicate even today. The 25 lb behemoth weighs more than a small tube amp! My unit is on loan from my friend Danz, who is out of the vinyl circuit temporarily because of his child. Hey, he is not getting this back!

Spec: Twin perm-alloy transformers with direct input/output connections (no selector switch in circuit); double-shielded sealed xfrmr case; transformer and input/output connections incorporated inside an outer gun metal shield cover

Cartridge load matching: 10 to 40 ohms
Step-up ratio: 1:11.5 or 21dB
Output load matching: 50k ohms
Freq response: 10 to 80KHz flat
Freq response: 5 to 200KHz +/- 3dB
Dims: 7" x 9.5" x 4.5" (W x D x H) approx

Introduction: K&K Step-up Transformers
In 2007-8 I learned about the K&K (Swedish Lundahl step-up transformer) SUT kits (K&K official website) from two articles by my favorite writer Art Dudley in Stereophile (the shorter article available here). Who else would write about a large selection of SUT's, some budget priced, in a mass market magazine?

Almost all designs at this budget level are based on (or at least factor in) the venerable Denon DL-103, the budget cartridge to beat, and as AD knows the Denon well and praised the K&K, I decided to try it out.

True to my cheaptubeaudio roots, I only ordered the transformers as well the tiny circuit boards (which makes wiring easier). I'd probably prefer my own choice of cables for wiring anyway. But as every DIYer know, getting the right enclosure and hole-drilling is the hardest part of a project. I thought of several short-cuts to evade hole-drilling, but never got around to it. Here lies a warning: buy the complete kit to save yourself hassles (the current version shown on the website seems to be a revised larger board that combines the 2 channels. Must be easier to work with than mine!).

When I called up K&K in 2008, a one-man operation it seems, they were sold-out temporarily of the LL9206 (the one reviewed), which has a 20 db gain option that is theoretically perfect for the Denon DL-103. As I have many other cartridges with even lower outputs, I decided to order the higher-gain alternative LL1678 (Data Sheet). The LL1678 was $78 each, the circuit boards (pic) $6 each, so with shipping I spent a grand total of $175. Today, three years and much depreciation of the US dollar later, the LL1678 is $80 each and you only have to spend $4 more for the same order. That is holding the line on inflation and I sing praise to K&K.

Phonoamp 1: AUDIO NOTE MM PHONOSTAGE KIT (old version):
The current Audio Note Kits is a Canadian company that works closely with Audio Note UK and sources many parts (not sure about all) from them. The kits now have evolved to be quite different from older kits that AN UK directly sold before (like the original Kit One 300B and the Preamp Kit that I sold long ago; I still have the rarer Kit Four, a 6V6 PP amp). It is officially sanctioned, so I am sure the philosophy and methodology and parts have remained consistent, but I still wonder a little how much the designs and revisions (in particular sound) resemble AN UK. But the official ties are strong and the dealer of AN UK in HK, Elephant Holdings, is also commendably dealer of the kits (not the way to make quick money).

Hong Kong Audio Note Kit users beware: there is another place in Mong Kok that sells AN "kits". While some appear to be the Canadian stuff, there are too many "options" that are not found on the official Kits site. I'd exercise caution and only buy direct or from Elephant Holdings.

My unit is second-hand, one assembled by Elephant Holdings. It is an earlier version called MM Phonostage Kit (details still in the official archive). Comparing the pics, although there are some differences in components, I confirmed with Brian at AudioNoteKits that it is a standard version with some upgraded Jensen caps. Many thanks to Brian here; he must be a busy man!

Compared to the current L3 phonostage kit, there are similarities as well as major differences:

-Power supply: similar, based on AN UK's M2 preamp (6X5 rectifier; ECL82 regulation).
-Main circuit: L3 uses circuit from AN UK's M3 phono preamp (3x 6072) whereas mine uses Andy Grove designed, modified phono circuit of AN UK's original Preamp Kit (pic here) (2x12AX7 and 1x 12AU7).
-Wiring: L3 uses silver and mine copper AN-A.
-Gain: L3 is considerably higher than mine (40 db vs 32 db)

Click pic to enlarge. Before full surgery (1 large cap already removed).

My particular over-burdened unit: My unit came with an anomaly, make that a deformation. Look at the photos. The previous owner thought the phonoamp had not enough bass and kept adding to the output caps. For each channel, he used 2 ridiculously large and expensive 1μ Jensen output caps (2 μ per channel). Needless to say, the bass was sluuuugish; shall we say the bass stood still? I am sure he knew, as he added a 0.01μ Jensen cap in parallel, surely in an attempt to liven up the dull top end. Considering all these are Copper PIO with Silver Lead-Outs, I could probably recoup some cost by selling them. Any offers? The units came with Mullard CV4035 (=CV4004=12AX7) tubes adapted to regular socket.

How does it Sound? Round 1, take-out: Before the unit got home I actually lent it to my friend AL. At his place he used it (warts and all) surprisingly to good effect as an MM stage with his Lenco turntable and Decca cartridge, fed into Mark Levinson electronics driving big MBL. It held up well against the EAR834P and the Softone/ICL that I am going to cover below. They did think the gain on the low side and preferred crisper current production tubes to the installed Mullards in their tube rolling.
Round 2, back home with Denon AU-1000: After I got it home, I tested it in my system. As I didn't have an MM cartridge already installed, I had to use it in conjunction with a SUT:

Analogue 1: Kuzma Stabi S/Stogi S + Midas Denon DL-103 (up to round 4)
Analogue 2: Garrard 301 grease/Ortofon RS-212S/Midas DL103/Ortofon Kontrapunkt C (round 5)
SUT: Denon AU-1000.
Connection to preamp: I used my best cable, the incomparable Kondo KSL-LPz.
Preamp: Leben RS-100 line preamp (info) on loan to me
Amp: Elekit 8230 amp (2 wpc 2A3 amp)
Loudspeakers: Tannoy Canterbury.

The gain of the SUT + phonoamp is 20 + 32 = 52 db, enough for my sensitive speakers, especially since the Leben linestage has 26 db of gain!!!!! However, as mentioned, the sound was lugubrious and sluggish in the bass. No, the big output caps don't work for me!

First Surgery, weight losing:
Without a manual or circuit, I was not sure of the correct value of the output cap. Some searching showed that the later L2 kit used 0.22 μ, which seemed right to me. I removed all of the outputs caps and put in place cheap cheap (yes, I have temporarily re-discovered my cheaptube roots) 0.22 μ NOS Russian (military) caps, which instantly restored normalcy to the sound. I later confirmed with Brian that 0.22 is the right value. Thanks again, Brian!

Round 3, after first surgery, with Denon AU-1000: After I restored the output caps to original value, the sound improved hugely. Now, rhythm and pace came back, and the bass finally moved! :-) Now, I was able to assess the true sound of this unit as well as the Denon.

The sound of the Denon AU-1000 is truly exceptional (I have used it with other preamps; more reports later) , dark in background, wide in bandwidth and dynamic. Probably partly due to its low gain, the sound of the AN kit was just a tad slow with my gig, slightly soft on top, but smooth and quiet. I didn't think Mullard tubes are the best choice for it. Swapping in 2x 12AX7 Holland Amperex + 1x RT 12AU7 resulted in some gain in air. Even if the caps were not run-in, I was satisfied with the very good performance of this kit.

Click pic to enlarge. Note the green K&K boards and grey Russian output caps.
Second Surgery-K&K weds Audio Note: As I rarely use MM, I decided to turn the AN into an MC phonoamp by installing the K&K trannies (plenty of space). This way, it saved me one chassis and the hassle of hole-drilling; cheaptubeaudio forever!

I cut off the stock AN-A input cable near the circuit board ( originally star grounded under the circuit board) and re-used the cable for input to the K&K, but I did not yet connect the shield at either end.

For the K&K/circuit board interface, I reused the AN-A red + strands. The original white -ve and shield could not be extricated as they were twisted and soldered together; worse, they broke off while I manipulated it (I am not so sure I like AN's way of wiring). As they could not be re-used, I soldered a tiny length of Radio Shack solid core to the star-ground underneath, and connected this to the K&K boards' -ve's with small lengths of silver-plated wires. I used blue-tac to fix the trannies to the cage. I did not solder in posts for loading resistors. Perhaps when I tweak again I may, but then I may not.

Aside from the -ve, each K&K circuit board has a separate ground as well as another ground out (labeled CT, presumably center tap). I did not connect these but did solder wires to them in case I need to ground them.

For the LL1678 I chose the 24db gain option (others are 18 and 30db). The impedance ratio is spec'ed at 256 and so the loading of the MC would be roughly 183 ohm, theoretically therefore likely more optimal for Denon than my Ortofon's. But again, I belong to the camp (which includes K&K) that think loading is much less important when SUT is used. But there are many who think otherwise and would go to great lengths for impedance matching; for that you can read this wonderful Vinyl Engine article on SUT and MC cartridge matching.

Round 4, with K&K, now an MC phonoamp: Brand new, without run-in and a trace of hum, the sound was not bad at all, even at first play. Compared to the Denon AU-1000, the raw K&K seemed just a little less precise, rendering the proceedings with a broader stroke, but in terms of dynamics and detail, they seemed just fine and not much behind. I shall run these in and then tell you more about it.

Later in the evening, when I returned after rendezvous with my friend, I decided to switch in the Kondo M7 preamp in place of the Leben. My my, the cheap K&K much preferred high society!

Click pic to enlarge. Note more grounding and the yellow output caps.
Round 5, with Garrard, hum management and output cap tweak: While I did have a trace of noise with the Kuzma gig, it was at low level. But when I switched to my Garrard 301, the noise, hum and Rf and all, became quite prominent. At this point I connected the ground outs of the circuit board to the ground, but to NO avail.

I replaced the output caps with a generic yellow 0.22 output cap (available at 麥氏). It has no brand name, and I don't know what it is. Rated at 1000V I suspect it is intended for use in power supplies, but I have used these for years to great effect. Sonically they are crisp and balanced, scoring over the Russian caps for sure. But the noise remained.

I discovered accidentally that touching the phono cable connectors produced noise, and knew then that the input -ve was not well grounded. Indeed, checking the circuit diagram revealed that the -ve on the input side should be grounded (shows you how much of a DIY person I am, or am NOT). I did so and bingo, cured. The connector is no longer hot and things became much less noisy, with just a low-level hum remaining.

Click pic to enlarge. Note removed AC filter top right.

Phonoamp 2: SOFTONE/ICL MODEL 4:
Softone is a small Japanese company that used to be ICL (official site in English). Its chief designer is quite respected. I have long been a fan of this company, and shall write an overview when I have time. I have all their current products except the passive preamp. If you wonder why there is no Model 1, it is an discontinued integrated ICL amplifier available with either 300B or 2A3 (I have both).

The Model 4 is a MM/MC phonoamp of hybrid CR-type RIAA that eschews NFB. Its price has not increased in years, and at USD 650 is a screaming bargain. It is a hybrid CR-type RIAA with no NFB. ICL's mail order is efficient and packaging first-rate. Buy with confidence.

At this price point, it is a great luxury to have the choice of 2 MC loading impedance. Under the cover, the built, as with everything from this company, is exceptional.

Round 1, comparison with Denon AU-1000: The Model 4 worked a treat with the Denon DL-103 to produce a beautiful and mellifluous sound (it was after all designed around that cartridge), just a little on the soft side at the top end and in terms of dynamics. Using it as an MM stage, it was obvious the Softone has more gain than the AN Kit. The Denon AU-1000 had just a little more precision than the stock trannies, but the results were very close. This attests to the fine quality of the SUT's inside the Model 4. Incidentally, like K&K's Lundahl, they use Permalloy.

Round 2, comparison with K&K/AN: In terms of tonal balance and macrodynamics the two are hard to tell apart, even if the Softone has higher gain. But after a lengthy session one thing started to emerge: even if it is a little slow, likely due to the low gain, the AN/K&K had the better rhythm and pace. It is like speech with better cadence that employs good punctuation and appropriate pause when needed. The Softone was by no means not fluent, but it sang in a somewhat broader stroke and its fluency seemed just a little less related to the music, a sort of mild euphony if you will. It was obvious the Softone lacked a little in microdynamics.

Round 3, minor surgery before rematch: At this point I did a minor surgery that saved the day. The idea, which oozed out of my friend oozz, was conveyed through my 惡客 friend icefox.

You see, the ICL phono and digital gears all employ an AC filter at the AC socket. Personally, like my friends who noticed, I have never liked these and would prefer not to have them (even if my home is RF prone). Fortunately, as the Model 4 AC wires are only clipped on, substituting a normal filter-less socket was a breeze. I also corrected the AC polarity (Japanese AC polarity is different from HK) while at it, though I don't think that accounted for much. I did the same on my ICL DAC, but haven't had time to test it.

The result was instantly audible as better microdynamics. Now the 2 phonoamps are very close in performance and I will cover more in Part II.