Funny you talk about filament sag. I used to restore tons of vintage tube amps when I collaborated with Jim McShane. So I worked on many amps that used the EL84 type tubes. There is a Russian variant that is quite a good sounding tube and you could get them for peanuts. The only thing was that for a series of years they made that tube, they suffered from filament sag. They were tough as nails and worked for years, but it you tipped an amp on its side to work on something while it was running.... bbzzzzt. Fried output tube and usually the cathode resistor as well. You could run any other EL84 type in any direction, but not those Russian ones of that decade or so! You could run them upside down without an issue, but not on their sides.
300b lovers
I have been an owner of Don Sachs gear since he began, and he modified all my HK Citation gear before he came out with his own creations. I bought a Willsenton 300b integrated amp and was smitten with the sound of it, inexpensive as it is. Don told me that he was designing a 300b amp with the legendary Lynn Olson and lo and behold, I got one of his early pair of pre-production mono-blocks recently, driving Spatial Audio M5 Triode Masters.
Now with a week on the amp, I am eager to say that these 300b amps are simply sensational, creating a sound that brings the musicians right into my listening room with a palpable presence. They create the most open vidid presentation to the music -- they are neither warm nor cool, just uncannily true to the source of the music. They replace his excellent Kootai KT88 which I was dubious about being bettered by anything, but these amps are just outstanding. Don is nearing production of a successor to his highly regard DS2 preamp, which also will have a unique circuitry to mate with his 300b monos via XLR connections. Don explained the sonic benefits of this design and it went over my head, but clearly these designs are well though out.. my ears confirm it.
I have been an audiophile for nearly 50 years having had a boatload of electronics during that time, but I personally have never heard such a realistic presentation to my music as I am hearing with these 300b monos in my system. 300b tubes lend themselves to realistic music reproduction as my Willsenton 300b integrated amps informed me, but Don's 300b amps are in a entirely different realm. Of course, 300b amps favor efficient speakers so carefully component matching is paramount.
Don is working out a business arrangement to have his electronics built by an American audio firm so they will soon be more widely available to the public. Don will be attending the Seattle Audio Show in June in the Spatial Audio room where the speakers will be driven by his 300b monos and his preamp, with digital conversion with the outstanding Lampizator Pacific tube DAC. I will be there to hear what I expect to be an outstanding sonic presentation.
To allay any questions about the cost of Don's 300b mono, I do not have an answer.
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Hi Lynn and Don (and the OP!), it’s been great fun watching this thread. I heard from several PAF attendees that the Spatial room was a highlight of the show. A friend and Audiogon member directed me to this thread (Hi Mark!). In reference to Lynn's suggestion regarding a cathodic triode, several years ago I worked directly with JJ Electronic on an octal based cathodic style "300B". This was originally a joint project with Matt Kamna, who also desired an easily implementable cathodic 300B derivative. We tried modifying all the usual suspects (KT88 included) but the best candidate was their EL509S. With that tube we could simply remove G2 and the beam forming plate, tweak the G1 pitch, and you get a viable power triode, with a hell of a cathode to work with...
Grid Curve 300Vp fixed:
Plate Curve -56Vg1 fixed:
Cheers,
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I am impressed you took the project that far, but the minimum requirement for 10,000 units on an unknown tube is a steep hill to climb. Even at OEM prices, that’s a half-million dollars on a gamble. The "X" tube would have to be very very good, and very very popular, for that gamble to pay off. In other news, the all-IT, no coupling-cap version of the Blackbird is the best version yet. The LC coupling on the 6SN7 is going away and getting replaced with a custom IT with 18 Hz to 35~40 kHz bandwidth. This gets rid of six parts - a pair of 100 Hy inductors, a pair of copper-foil coupling caps, and two 220K grid resistors. No RC coupling, no LC coupling, and no current sources, either as plate loads or in the cathode circuit. The signal path is copper wire, high-nickel magnetic cores, and vacuum tubes. As Don mentioned on a recent phone call, there is no direct electrical coupling between any of the stages, which filters off any RFI incursion before it gets amplified. Homes are much noisier in the RF spectrum than they used to be, with Bluetooth and WiFi everywhere. Tube lineup remains 6SN7, matched pair of 6V6, and matched pair of 300B. Tube rolling is welcome so long as pairs are matched. |
@eddie138 Thanks so much for chiming in. Really interesting post and the economics are of course as you stated. It is not like getting a custom capacitor made where you only have to have 100 of them for an order. I guess that explains why manufactures stick with the known tube types where there will be a market. Now if someone would start cranking out moderately priced 45 tubes......:) But you would have to sell a lot of them to make it worthwhile. |
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