I meant to post this question the other day, but it apparently disappeared into the ether -
Who, on this thread, plans to attend the Pacific Audio Fest this year?
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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RC coupling, although fast and compatible with overall loop feedback (highly desirable in pentode amplifiers), throws away about 1/3 of the potential swing (through voltage divider action) and also creates a steeper load-line, which increases distortion by 2 to 3 times (the load-line swings down into the low-current region). But Job One in any feedback amplifier is bandwidth, otherwise the thing goes unstable. Can’t have that. So the rule of thumb is no more than one coupling cap in the entire forward path, plus the output transformer needs at least 60~80 kHz of bandwidth. The Williamson, which dominated from 1948 to 1956 in this country, was marginally stable unless you used the specified Partridge transformer, which had an astounding bandwidth extending to 120 kHz, and down to 4 Hz. So your options are limited if you want to wrap feedback around the amp ... only RC coupling, and only once per side, not twice, like the Williamson. If there is no overall loop feedback, you can have any kooky topology you like, since phase margin no longer matters. But ... triode-connected pentodes have somewhat higher output impedances than DHTs (2 k instead of 800 ohms), and aren’t as linear. But this depends on the pentode. Don and I selected the triode-connected 6V6 because 1) 45 tubes are near-unobtainium these days 2) 6V6’s are reliable, been around forever, much loved by guitarists for their famous tone, and oh yes, sound good too. Last but not least, the 6V6 was purposely designed as the replacement for the 45 in radio use, so operating points are very similar. Part of amp design is deciding what "tone" you want. Because it’s going to have a sound, no matter what technology is there ... Class D, MOSFETs, bipolar transistors, pentode, triode, or DHT. No matter what you design, it will have a sound, no matter what you do, or how clever you are. The perfect component does not exist. The designer needs to steer that little touch of coloration in a good direction. Fortunately, Don and I are on the same wavelength ... I’m looking forward to meeting him at the Seattle show, in person. Should be a lot of fun. |
As they say, if you literally built a straight wire with gain half the people wouldn't like it:) Everything has a sound. I will say that these amps have far less of a sound than anything I have ever heard... or not heard... or whatever... They just seem to remove themselves and just leave this cloud of music in your room. Pinpoint imaging, but it is like omnimax for the ears. That is my take. I will be interested to hear what other people think in Seattle. |
Yep!!! Tubes and transistors both present some degree of colouration but with different signatures. Charles |
Like @whitestix I am quite comfortable with my very limited understanding of 'Math' for Electronics and 'Hands On' practical exercises with Electronics, even though the latter is easier to comprehend. The above has never been a limitation or a constraint for me in relation to having Devices produced for Audio that are Bespoke and unique, as is the Design of Amp's under discussion in this thread. I have created relationships with EE minded individuals that are very adept, and one relationship/friendship extends back 30 years and I still contact the EE a few times a year and send a Bottle of Drink for them in the New Year. The Math is one thing, how to utilise the Math and adopt it to be used for the Practical Exercises being undertaken, 'will always be a better undertaking', when a time served experienced individual, who really has a understanding of how to interface their design hooks are doing the Math and Circuit Design. I have 6SN7's actually 'Half 6SN7's' in a Driver Stage on 845 Mono's. I have been fortunate to have had a variety of these Tubes from modern to vintage tested for being matched pairs. These have then been used for Tube Rolling and as the subjective evaluation, I have become very attached to the Vintage KR VT 231 Black Glass for the SQ when the perception of a lean Bass and projected Mid and High is the desired presentation. If a Richer Presentation is desired, the Vintage Sylvanias do this, to various degrees, even though some will swear the details. As a subjective evaluation I have found that the modern Tubes EH and Genalex have proved good for a period of time, a distortion can be detected to develop and even though not too much of a detractor, it is enough for me to want to end the use of the Tubes when it has been detected. I have been extremely happy with what I have learned about the use of a 6SN7, I have also found the Tubes I am Wed to. Additionally, due to the rarity and costs associated with vintage tubes and then the concerns for a accurate matching, I have looked at other modern alternatives and there is a Linlai Thread on this forum that presents a very positive assessment for this Brands Tube. As a Tube Roller and attendee of other Tube Owners rolling experiences, I am very aware a magic can occur as a result of a change of a tube. When Don's 300b design is up and running, I am sure there will be a time when an owner will become curious and the stock 6SN7's are to be swapped, there is nothing to suggest differently, that a Valve might be discovered that really 'hits one out of the ball park' for the perception of Amp's performance.
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