FrankCooter

Excellent explanation of often poorly understood power supply issues, particularly regarding the use of chokes. Like you, I'm also a big fan of "iron" in a HVDC supply. For many years, audio power supplies were more or less an afterthought to the audio circuitry. A lot of the mushiness and euphonics attributed to tube gear was directly related to the floppy, high impedance of cheap and under designed tube rectified power supplies. Conversely, a good portion of the flat, cold, harshness attributed to early solid-state gear was the result of power supplies that consisted of nothing but noisy solid-state diodes, a pair of giant electrolytic capacitors, and simple resistor. I'm curious to see your shunt regulator. On one hand, with the minimal and balanced current draw of the SRX circuit, one wonders if it would make any noticeable improvement over the already very effective LCLC filters you're employing. On the other hand, because of the minimal current draw of the amp, the SRX seems like an ideal candidate for a shunt regulator experiment. Generally, I prefer shunt over series regulators. Sometimes I think that solid-state series regulators can add add a glare or harshness to some circuits. Shunt regulators, whether tube or solid-state, don't seem to have this problem. One thing you might want to consider if space is no problem is swapping the electrolytic caps for some PIO motor-run types. At least with class A single-ended tube circuits, it can make a noticeable improvement.

When I was referring to the the SRX circuit, I meant Jim's SRX Plus circuit. The original is pretty good, but Jim has taken it to an entirely new level. I don't often build other people's designs anymore, but the original SRX always intrigued me, and the SRX Plus has renewed my interest. I have a reputation for building "over-the-top" tube projects, but I actually find it a lot more fun to see how much you can do with simple circuits and limited resources. In the not too distant future I'll be building Jim's SRX.

I have some spare power supply boards for the KGSS. You're welcome to one if you want. I second nopants recommendation for the SRX. It's easy, cheap, rugged, uses readily available common parts and can be built point to point. Any design can always be improved, but there's nothing at all wrong with the circuit as is.

What you're looking for is called "SOOW cable". It's very flexible and is designed for equipment where there is a lot physical motion. I use 16 gauge 8 conductor. It's rated for 7A/600VAC. Try "Wire and Cable to Go". They sell it by the foot. If you can't get it anywhere else PM me and I'll cut you a piece off my (ever shrinking) roll.

Thanks guys.

Really like what you've done with this circuit. I've come close to building the original several times. I've always had an attraction to dirt simple, but high performance tube designs that could be built in a weekend by a high school physics student using mostly scrounged parts. I don't have anything to add to to your extensive documentation except my output tube experience with several Egmont variations using simple 10M90 CCS. As has been mentioned, the 6BL7/6BX7 have huge section to section variations. Out of 30+ samples I could not get any that matched closer than 10V. Some varied as mutch as 50V. Too bad, because on paper, they look like excellent candidates for this application, not to mention they are cheap. By trial and error based on listening, I settled on 400V rails with 20mA current. Overkill I know, but I like small power tubes in non-traditional applications. I used triode-connected EL84's, 7591's, and 6v6. Running open loop, it was easy to hear the differences. I would bet your cascode CCS is a mutch better approach. The 50's era 6SN7GTA/B is a great tube, I've run them no problems at 400V at full dissapation. They are also still plentiful and a great bargain. I especially like the Sylvanias. Thanks for your contribution and let us know when you article comes out.

Rotijon, I have never seen Kerry's work in person, but judging from the posts and photos of his work on these forums, I consider him ( I've built electronic equipment myself for 40 years) the finest amp builder in this hobby. No slight to the commercial version, which is superb, but I would bet his construction sets a quality and artistic standard that can't be pratically duplicated in a commercial product.

HemiSam, pm me, I may be able to help.

The 26 and the 6080 are about as far apart as you can get in the tube world. Neither is really suited for phono use. I own about 30 type 26, none of them are quiet. The type 112A is similar to the 26, and usually a little quieter, but not much. The only thoriated tungsten tube that I can think of that MIGHT work in this application is the 10y, which is expensive. Any DHT will be difficult and problematic in a phono application. If you're determinined to try it, I'd look at the Russian 4P1L or 6P21S. They both work well as the output of a headphone amp, and are dirt cheap. Lots of options if go for an indirectly heated type. I like small power tubes anytime low gain is required. Not much beats the tonality of a triode-connected 6V6.

Doug, I hear you about the Dynaudios. The best small speaker I ever built was a simple two-way based on the 21w54 woofer .Absolutely the best 8" woofer I ever heard. Simple 2nd order crossover and some Dynaudio tweeter I've forgotten the model number of. Quite efficient, but had some real balls. Ran just fine off a small push-pull 6V6 amp. So unless things have changed a lot in the speaker world in the last couple of decades I'd be looking hard at the Dynaudios. You might want to consider vintage JBL's, Tannoy's, Altecs, or Klipsch. If you do it right it's actually a profitable investment. A few years ago I had a pair of Klipsch "Belles" ( furniture grade LaScalas). I bought them cheap because of some fairly minor cosmetic issues. I refinished the cabinets, used them for a year or so ( my listening room wasn't really big enough to take advantage of them), and then sold them on Ebay for substantially more than what I paid for them. Another alternative is your own cabinets filled with TAD components. You won't lose money here either. I don't own any speakers at the moment, ( kind of done with the horn thing) but I'm beginning to think about some vintage high-end JBL's or Tannoy's.

Your work looks great. I particularly like the way you've handled the heatsinks and the chassis in general. My only criticism is that you can still work on the wire dress a bit. My projects always look like a mess at first pass. It usually takes me three revisions before I'm satisfied, and even then, there's always things you would change if you did the project a second time. It helps to wait a few days before each revision. Putting the project aside for a while clears your mind and gives you a fresh perspective.

Greetings Mario, There are many people much more qualified to answer your question here, but I'll give it a shot anyway since my tastes and expiences somewhat echo your own. I currently own SR-007Mk2's and have have owned 303's in the past. I have heard a lot of 007Mk 1's. The Mk 1 has a subjectively more even and neutral overall presentation. The Mk 1 responds best with solid-state or very neutral tube amplification. The Mk 2 has a bit of a mid bass bump and a slightly more forward presentation. The Mk 1 is preferred by most here, but the Mk 2 is a very fine headphone in it's own right. With some amplification (primarily tube) the Mk 1 can sound a little recessed and dark. I build tube amplification and listen to rock music. In my system I actually prefer the Mk 2. I also prefer the Mk 2 to the LCD-3 ( also a very fine headphone), which I also own. I was very fortunate to get a one time shot at a brand new U.S. Mk 2 with warranty at essentally a used price. Like you, I was hesitant to purchase a 10 year old headphone in unknown condition for the kind of money we're talking here. Many of the Mk 1's I've seen at meets are starting to show their age. If you ever need new drivers from Stax, they will be M 2's. If I had to pay full list priceI for the Mk 2's i might have made a different decision, but I have no regrets and greatly enjoy my Mk 2's.

Best post I've ever seen !

They do sound nice. Slightly fuller overall and with a less harsh treble than comparably priced Stax. Maybe one day they'll fix the "squeal" issue. Mine are on their 4th set of drivers (all supplied under Koss warranty-superb unlimited "no questions asked" service} and could use a new set. Perhaps someday Koss will attempt a genuine world-class product. I'd bet it would be very interesting.