Current System

[Lynn Olson]

There's actually two systems here: the AV system, with the Panasonic 58" Plasma TV, Panasonic Blu-Ray player, and Marantz AV8003 pre/pro and MM8003 power amplifier, and the 2-channel all-triode system, off to the left. The Ariel speakers are switched between the two sources.

The digital transport is a modified Denon with SuperClock III, the Behringer is a sample-rate-converter that upconverts to 88.2/24 with added dithering, and the Monarchy DAC uses the Burr-Brown PCM-1704 ladder DAC with resistive I/V conversion and 6DJ8 in SRPP for further amplification and buffering. I'm considering getting a high-quality USB-S/PDIF converter and using the MacMini as a music server.

The close-up photo shows the Karna amplifier, with a 5687/7044/7119 dual triode for the input tube, push-pull 45 direct-heated triodes for the driver stage, and push-pull 300B triodes for the power stage. The input transformer/phase splitter is from Tribute in Holland, and the two interstage and output transformers are from Bud Purvine of O-Netics in Seattle, Washington. The amplifier stays in Class A1 up to about 15 watts, and goes into Class A2 (positive grid bias) through 30 watts. Clipping recovery is instantaneous, since there is no local or global feedback, or RC-coupling caps to charge and discharge.

Each Karna amplifier has two independent B+ supplies (350 and 500V) from an external chassis, on the rack below the main chassis. The input and driver stage use VR-tube shunt regulation on the 350V supply, and the output section uses the 500V supply. Rectification is from 6CJ3 damper diodes, which have 30 sec warm-up time and are quieter than the more common vacuum diodes like the 5U4 and 5R4.

Yes, I know there's no place for the new turntable. All too aware of that. My sweetie suggested moving the Xbox 360 over to the left side of the TV, moving the digital gizmos into the space where the Xbox was, and putting the new Technics SL1210 Mk5 and the as-yet-unbuilt phono preamp on top of the main equipment rack. All in good time - this forum is a good place to start asking about racks for the phonograph, which would go over where the Technics RS1520 tape deck is now. Putting the tape deck on top of the REL Strata II subwoofer isn't a classy place to leave it anyway, so I have an incentive to re-think where everything goes.

[jostber]

Those Karna amps look mighty nice, sure they sound good. :thumbsup: Are there 4 amps you have there?

[Lynn Olson]

Umm. let's see. The Marantz has eight channels, five of which are in use (when watching movies or TV). Sound quality for movies is superb, but music is only just OK. Then again, there are very few transistor amplifiers that I like, including the $50,000 amps I hear at hifi shows. I auditioned many different home-theater receivers and was appalled just how bad they sounded on music - far worse than the mid-fi Japanese receivers of the Seventies, which were hardly great at the time. The Marantz has the merit of being at least listenable on music, so the folks in Japan must have done some voicing on the circuit.

I have a "spare" stereo amplifier, the JWN Special, which I reviewed in Positive Feedback Online. It's a real charmer for about $1200 or so, using a quartet of 6L6's and vintage 6SN7's. Definitely one of the nicer PP pentode amps I've ever heard. I got it for those times when I twiddling with the Karna amps, so I'll still have a good-sounding tube amp to listen to. The JWN easily compares to high-end products in the $10,000 range, and is designed and built by a easy-going fellow in New Jersey. All point-to-point wiring, with vacuum-tube rectifiers, and the deluxe feature of separate B+ supplies for input+driver and the output stage. Smooth, silky, tonally vivid, and excellent 3D spatial presentation.

The Karna amps have four chassis, two for B+ power supplies, which are connected to the two audio chassis via HV umbilical cables. The umbilical cables are rated for at least 3500V, and the Amphenol connectors similarly. Next time around, I will put all of the circuits on one chassis (per channel), since the umbilical cable has a rather tricky grounding system.

The Karna amps have the snap and clarity of SE triode amps, but with a depth of tone and dynamic scale that is unusual in the SET arena. For one thing, distortion is much lower, and the driver section, thanks to transformer coupling and ultralow distortion 45 DHT tubes, is a powerful little 3-watt amplifier in its own right. In most commercial SET amplifiers, the driver has more distortion than the output tube (particularly if the driver is RC-coupled), so you never really hear the output tube at all. The sound of the Karna is not easy to describe, since it is so different than most PP amplifiers, which rely on 10~20 dB of feedback to linearize the pentodes.

I plan to be working with a collaborator in Texas on a RIAA phonostage using balanced circuitry and transformer coupling - in a way, the SL1210 commits me to the project, since I have no plans to buy a commercial phonostage.

[Lynn Olson]

Here's a picture of the JWN. It sounds even nicer than it looks - certainly one of the best pentode amps I've ever heard.

Tube lineup: Input tubes are single triodes in the 6J5 family, drivers are 6SN7, and the output tubes are top-cap versions of the 6L6, the 6BG6GA, which is an uprated, high-voltage version of a 6L6.

[DSJR]

All wonderful but potentially lethal if kids are around... Are these kits or are they available retail?

[Lynn Olson]

The JWN is fully assembled, not a kit, and the price includes all tubes, tested and ready to listen. Jim Nicholls, of JWN, is happy to build his amplifier with EL34, 6L6, or any other popular pentode tube. His standard model has the input jacks on the back; it was my request to put the inputs on the front, which simplifies the signal path in the amplifier.

Since this is Grandma's and Grandpa's house, it's a no-toddlers and no-uncontrolled-pets zone. This house is grossly unsafe for the rug-rats; there's a maze of wiring behind the AV system, open tubes at very high temperatures, and woe betide anyone that dares to approach the open crossovers for the Ariels. Look but don't touch is the rule for guests; even visiting dogs seem to figure it out. Maybe there's an unseen energy field that tells them to keep away.

[golana]

Looks like a great system, Lynn. Have always liked the design of the Karna.
What are your future plans for your Techie 1210? All out or reserved?

[The Grand Wazoo]

Mike, you have a message on your profile page (http://theartofsound.net/forum/member.php?u=3070&vmid=881#vmessage881). It would be appreciated if you would follow the request I've made there.
Thanks a lot in advance.

[Lynn Olson]

Looks like a great system, Lynn. Have always liked the design of the Karna.
What are your future plans for your Techie 1210? All out or reserved?

All out, I'm afraid. Looking very closely at the Jelco 750 arm, the Applied Fidelity bearing, and the Applied Fidelity Delrin mat+aluminum top-platter. The latter adds 3 lbs of additional platter weight, but swapping the main bearing should deal with that. The lower the bearing noise, the less the servo feedback has to correct, which is all to the good. (The less you give feedback circuits to do, the better they work. Monitoring the feedback error signal is the best possible way to directly examine what stick-slip bearing friction and stylus drag are doing under real-world conditions.)

I'll be posting in the SL1200 forum asking for people's experiences with various mats, bearings, etc. Sending the TT to the UK is not a realistic option - shipping from the center of the USA (Colorado) all the way across the Atlantic, and then back again, is hardly going to be cheap.

I'm also very curious about which stands/plinths/supports sound best. I'm not really much of a tweaker, so the this whole area is new to me.