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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. 

 

 

whitestix
atmasphere's avatar
atmasphere
12,210 posts
 

The measured frequency response of this transformer (with 6f6) in my amplifier is 6Hz to 90KHz -3dB.

@alexberger while that looks excellent, I suspect these measurements at the link are not at full power. If you want the amp to perform, full power bandwidth is important. Did you measure your amp at full power?

how do you balance a number of tubes in parallel on your OTL amplifier without fixed bias. Is it necessary to select all these tubes by parameter or the amplifier circuit balances all parallel tubes automatically? 

Actually our OTLs are fixed bias. A manual DC Offset control is provided to balance the two output tube banks using the front panel meter.

We've never practiced power tube selection.

You can get a bit lower distortion by doing so; the distortion created by mismatch tends to be lower ordered harmonics. 

Most of the distortion in our design depends on how well matched the internal sections are in the input tube, since the input Voltage amplifier comprises all the gain of the amplifier. Usually that defines the measured distortion; apparently the output section is very low distortion on its own. 

This approach allows for much lower distortion than is possible with an SET. For example our MA-2 (which is zero feedback) can make 220 Watts (230 at clipping) with distortion at full power around 0.5% (with excellent tube matching); up to 1.8 to 2% if the tubes are not matched at all. Most SETs cannot make that sort of power; if the MA-2 is running at any level an SET can make the distortion is several orders of magnitude lower and its mostly 2nd and 3rd harmonic. Lower distortion is directly associated with greater transparency and detail and this is easily heard. 

Unlike an SET or push-pull tube amp, the distortion of our OTLs is unaffected by frequency since the amp has a direct-coupled output. Its full power down to 1 Hz. 

donsachs's avatar
donsachs
313 posts
 

For those interested and who may happen to be attending the Toronto Audiofest Oct 17-19, I will be attending and showing prototypes of the preamp and 300b monos that are built entirely with directly heated tubes.  Lynn Olson and I have been developing these over the past year or so.  They will be in a room with Joseph Crowe's largest horn speakers.  Troy (Joseph) Crowe will be there too of course.  I would love to chat with anyone reading this thread who would like to come by and hear some big horns driven by tubes!

cheers,

Don

tinear123
243 posts
 

Hi Don… My wife and I auditioned Troy Crowe’s full range horn speaker at his home yesterday and they do sound and look beautiful!  We flew up from the SE US to audition and glad we did.  I think you Troy will have a big time at the Toronto audio show. FYI, I’ve run your preamp for 5 years now and still love it.  Hope to hear your new amp one of these days soon.  

donsachs's avatar
donsachs
313 posts
 

Yes, Troy makes amazing speakers.  I have the open baffle ones, which he designed for me.  Just wonderful speakers.  He has a good ear!  Of course they are all works of functional art as well.

donsachs's avatar
donsachs
313 posts
 

@tinear123 If you auditioned speakers at Troy's then you heard the previous versions of the all dht preamp and amps.  They will be upgraded to the final circuit before the Toronto show.  Better and tighter bass is the main difference.  If I had to put a number on it I would say the final version is maybe 20% better.  Good luck with your speaker decision.

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