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| Model: | K&K Parallel-Feed Phono Preamp Kit |
| Category: | Preamplifier (Tube) |
| Suggested Retail Price: | $1,450 |
| Description: | Complete tube phono preamp kit, including chassis |
| Manufacturer URL: | K&K Audio |
| Review by gdahl on November 16, 2003 at 16:57:50 IP Address: 68.186.79.176 | Add Your Review for the K&K Parallel-Feed Phono Preamp Kit |
During the past couple of weeks I have had the opportunity to complete and listen to the phono stage kit offered by K&K Audio. The construction process itself was interesting and fun, partly because of the high quality of the parts. It turned out to be a bigger project than I first expected, but the results have been more than worthwhile.Actually, the availability of this phono stage kit turned out to be a happy coincidence for me. Last spring I was looking with interest at Chris Brady's version of the Oz-Loesch preamp. This circuit has an interesting heritage. As far as I know, it started with Arthur Loesch's design, which featured a split-passive RIAA. The path was something like this: 417A input tube, RIAA filtering, 6GK5, more RIAA filtering, paralleled 6DJ8 or 5687, and a volume control at the output.
The Loesch preamp was famous for its superb sonics, but problem areas included the challenge of finding quiet 417A's, and the high output impedance resulting from the volume control’s being located at the preamp’s output. The tubes at the output stage were battery-biased at the grid, which meant the volume control had to go somewhere else.
In Australia (“Oz”), Michael Maloney made a variation of the Loesch preamp, the “Oz-Loesch.” In order to tackle the noise issue, a FET was added to the 417A, creating a hybrid cascode input. This reduced the noise level very effectively. I’m not sure who was the first to use the FET cascode, but according to Chris Brady, Maloney improved the sonics of his variation by battery-biasing the FET, which reduced the slight transistor coloration that was otherwise present.
Chris Brady (of Teres Audio) created his own variation of the Oz-Loesch, which featured a 26 output stage. Chris chose to dispense with battery biasing for his output stage, and instead used traditional cathode bias.
Studying Chris Brady’s schematic last spring, I started thinking about the possibility of building my own variation on the Oz-Loesch preamp. Instead of a 26 output stage, I was interested in using the 3A/167M (loctal 437A) in parallel-feed, driving a step-down transformer. This would result in a nice low output impedance and the ability to drive long cables easily without noticeable losses.
Lynn Olson sat down with me the next evening, and together we worked out a schematic. It used a FET/417A cascode, passive RIAA, a CCS-loaded 8556 for the second stage, volume control, and a CCS-loaded parallel-feed 3A/167M driving a TL-404 step-down autoformer. I happened to describe the circuit to Kevin Carter, and he said that had been developing a very similar circuit, which ultimately became the kit currently being produced. I figured if Kevin had gone to all the trouble to bring the circuit into reality, there was no point in doing it myself from scratch. He had already worked out all the details, so I was just as happy to leave the sketch Lynn and I had made on the drawing board and build Kevin's circuit instead.
Kevin Carter’s design retains the FET cascode, but uses the Russian-made 6N1P for both stages. This is an RIAA-only unit, which must be used with an external line stage (K&K offers a line stage kit featuring a balanced topology, which is very similar to Lynn Olson’s Raven design).
I started out with just the kit for the signal boards. My plan at the time was to use my own power supply, perhaps the Loesch-recommended Gen-Rad 101B, but after some months I still hadn’t taken the time to work out all the details. Eventually I concluded that doing everything myself just wasn't going to be worth the effort for me, considering that Kevin's complete kit has switchable cartridge loading and signal polarity, plus a beautifully-made chassis with an internal subchassis for the power transformer and choke—these were good features to have, yet more trouble than I probably would have taken. Having completed the kit, I am now quite certain that the results are better what I would have come up with on my own.
I did make one change from the stock unit, though. I have been a big fan of Gary Pimm's current sources, so I installed his in place of the corresponding K&K parts.
The complete kit itself is a fairly good-sized project, but most of the tasks aren’t especially difficult. There is a significant amount of cross-checking required between the parts lists, schematics and stuffing diagrams. Kevin, believing “a picture is worth a thousand words,” saves the need for a lot of explanation by including a CD containing photos of various construction details and stages of assembly. Even so, there were a few places that required some careful analysis to understand how things were supposed to go together. This is perhaps not the best place to start for a first-time builder, but the documentation will probably evolve a bit more. There is also some soldering in tight quarters, so good soldering equipment and technique will certainly help bring about successful results.
I was especially pleased with the quality of the chassis, and the ingenuity of the layout. The chassis consists of five steel panels that fit together with machine screws, and a nice thick aluminum front panel. The builder can choose either a black or natural brushed aluminum front panel. I chose the natural, mainly because I planned to use my own stainless-steel DACT knobs instead of the turned wooden knobs offered by K&K. The power transformer and choke are housed in a steel sub-enclosure which fits inside the main chassis. The result is a noise level as low as one would get with an external supply, but with the convenience (and tight ground path) of a self-contained configuration.
Last weekend I brought the finished unit up to Lynn Olson's house and finally had the opportunity to play some music through the new K&K phono stage. He has been borrowing my amps since early October, when VSAC ended. I also brought my Maplenoll Athena turntable. The Maplenoll had a well-worn Grado TLZ installed, but I also brought along my Shelter 501/II. The Shelter had been previously used for about a week by the friend who sold it to me, but I hadn't had a chance to hear it for myself yet.
After getting the table set up and everything wired in, we listened to a few tunes. We could tell right away that something special was going on, but we also noticed a bit of dullness. High level passages ran into some trouble too. It sounded either like overloading or a tracking problem. Lynn said that he thought the Grado was shot, so I installed the Shelter.
This was where the real fun began! The Shelter was immediately vivid, transparent, and presented the music beautifully. It was clearly a great match for the K&K phono preamp. We listened to several records before it was time for me to head home. During the next listening session, I made further VTA and tracking force adjustments, which improved tracking and brought the soundstage into good focus.
Lynn said that it was the best phono preamp he had heard, and for my part, I would have to agree. There was detail and vividness in abundance, but it didn't sound either noticeably cold or over-warm. As we listened to more records, we frequently exclaimed that SACD (let alone CD) couldn't reproduce the beauty we were hearing. Low-level detail and dynamics were all one could hope for, and the unit ran extremely quiet, even with the 0.4 mV Shelter. We listened to a wide variety of program material: classical, rock, jazz, bluegrass. The resolution was high enough that we could even hear the magic of wonderful performances on poor pressings—a difficult test for any preamp.
Congratulations Kevin...very well done!
Gary Dahl
| Product Weakness: | Um, the power switch, I guess. |
| Product Strengths: | Sonics, build quality, quiet, flexible cartridge loading, low output impedance, front-panel mute/phase reversal feature |
| Associated Equipment for this Review: | |
| Amplifier: | Aurora (Lynn Olson) 16W Class A p/p 300B |
| Preamplifier (or None if Integrated): | (none) |
| Sources (CDP/Turntable): | Maplenoll Athena w/Shelter 501 |
| Speakers: | Ariel (Lynn Olson) 92 dB |
| Cables/Interconnects: | Nirvana, Pimm |
| Music Used (Genre/Selections): | Allison Kraus, Grieg, Gershwin, orchestral, rock, acoustic jazz |
| Type of Audition/Review: | Product Owner |
Follow Ups:
Sounds very interesting, but there's very little on the website about it (yet).What exactly is supplied with the kit, for those of us who might be less experienced builders? Is it as complete as a Welborne or Bottlehead kit? Does it come with all the parts? Are there step-by-step instructions, or do you have to read a schematic?
J!
Hi J,The "complete" kit includes everything but the power cord. Basically:
signal boards and parts
power supply board and parts
power transformer and choke
chassis and subchassis
cartridge loading kit
switches, input and output jacksThe K&K website is getting re-worked soon. The existing site has maxed out its bandwidth, so the new stuff has had to wait for the new site. You can get info by calling or E-mailing Kevin, or asking questions on the K&K forum.
Gary Dahl
"So many tubes, so little time..."
As many here already know, I have been singing the praises of this phono stage recently. It is as good as Gary says, I can hardly describe it any better. Mine was assembled by Kevin himself and the build quality is superb. The icing on the cake is how well this thing mates with the S&B TX-102 residing in the same case. For a VERY fair price I got an excellent linestage and phono stage that I would (and have) put up against preamps costing several times the price.Just another happy owner,
Oz
Hi Oz,I'm using the TX-102's also! They are at the input of the Aurora amps.
Gary Dahl
"So many tubes, so little time..."
I was especially gratified how the setup plays some pretty rough-sounding records - Columbia/Gershwin/Bernstein/Rhapsody In Blue, Beach Boys "Surf's Up," various Judy Collins records, etc. Some of the records need a good bath - our next purchase, needless to say, is a record-cleaning machine - but the sound was direct, immediate, and even on badly-EQ'ed records, realistic and vivid tone color.
You can effortlessly "listen through" the sonic gremlins and just enjoy wonderful performances - this is an unusual experience, especially on ultra-revealing high-end equipment. Usually high-resolution is a pretty brutal experience on less-than-perfect sources, which is why some folks with $50,000 systems have pretty small record collections (or, God forbid, only CD's!).The K&K/Shelter combo works *very* well together - and the adjustability for cartridge loading and a choice of MM/MC is just a neat bonus. By the way, the K&K is utterly silent - no grounds loops, buzz, tube rush, nothing. Just silence, or the quiet rumble of pressing noise. The set-up is absolutely untweaky - the Lundahl input and output transformers break the ground loops, so there's no endless hum-chasing with this or that shielded or unshielded cable. Transformer coupling is *the* way to go, folks.
Thank you, Kevin!
..using it with a Shelter (501MkII). What load are you using for your Shelter? I have been well pleased with mine at 100 Ohm but I have heard others going down to around 20.I have a friend who is also an audio dealer. The friendship came first so I don't have a problem if there are some things I don't buy from him. Anyway, this also gives me the opportunity to compare a lot of equipment. We compared the K&K (which I also had Kevin bulid for me) to a number of phono stages. It held its own or bested everything up to about $4K, including the Aesthetix IO (non signature). Great piece of equipment and one fo the best bargains I've found in audio. As I left my friend joked, "Tell few people about this phono stage, and NONE locally". :-)
Hi 4yanx,Actually the K&K phono stage and Shelter are mine, but they are set up at Lynn's place for now. We have been using it at 100 ohms. I have seen the 20 ohm recommendation for the Shelter when used with a transformer, and plan to try it. But when building the K&K, I started with stock values.
I am always glad to find great bargains in audio, because so much of the other stuff is beyond my means. The K&K uses a topology I was interested in and had high hopes for, so it has been rewarding to find it to be a great performer.
Gary Dahl
"So many tubes, so little time..."
...be interested to learn of more experiences with different loadings before going in and making adjustments. I am using the Lundahl MC trannies in mine and 100 Ohm is as low as I can go given the current configuration.
Congrats Gary! I'm glad you're enjoying the Shelter, wait until it fully breaks in...
And to Kevin Carter, keep up the good work.JH
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