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. 




Alex, remember, you cannot harm your amplifier if you completely remove the grid-load resistor. With a transformer, runaway from DC instability is impossible. There is always a DC path through the secondary ... as long as the secondary is intact.

If you have an oscillation lurking in there, at some high frequency like 5 to 20 MHz, that's a different story, and unrelated to the value of the grid resistor. 5 to 20 MHz oscillations, even at a very low level, will absolutely make the sound bright and unpleasant. If they are -40 dB down, you will never see them on a scope ... that's no more than a trace width. You need an RF spectrum analyzer to sniff out the little monsters. They look like little spikes rising out of the noise floor (which should be very smooth).

If you suspect this, you need a grid-stopper in series with the grid pin, like 100 to 500 ohms of carbon-comp resistor soldered no further than 1/2" from the grid pin. (NEVER use a wirewound for a grid-stopper.) That will kill self-oscillation.

I would try a grid-stopper first before futzing around any more. The only way you can solidly rule out self-oscillation is use an RF spectrum analyzer that's good to at least 20 MHz, preferably 100 MHz. These things aren't cheap, and only have one use, chasing out RF nasties. Low-level RF oscillations are surprisingly prevalent in high-end audio equipment, with poorly designed regulators as the usual culprit.

Try the grid-stopper first before anything else. After that, play around with various value of grid resistor, including nothing at all. It should not be sounding bright, unless something is wrong.

There are now over the past few months arrived Three 300B Power Amp's within my Local HiFi Group.

Two are from the Designs done by TDP and Andy Groves for World Audio Designs, One of these Two has an upgrade which I believe has Interstage Transformers.

The other is a design from a 'Heart' of Dutch Origin.

I am now becoming re-familiarised with the 300B sonic.

With the recent experiences and the knowing there are certain designers early in their career knowledge been applied to the Amp's, it really does make the idea of listening to the Amp's being discussed in this thread, a experience to be had. 

Who knows a Pair may one day be on the UK to be demonstrated.   

@pindac that will be up to Spatial Audio Lab.  I am going there in late Nov to teach them the builds of amps and matching preamp.  There will be a review pair made that will spend some time in the USA next year.  After that we shall see.   It is not hard at all to spec power transformers with dual windings and make a 220-240 VAC input version and source a proper IEC connector.  While I expect both these pieces to be very reliable, the problem with supporting European and Asian markets is shipping cost, and if the customer has a problem of any sort, the shipping costs are enormous to help them out with any warranty issues.  If you make 100 units of anything, no matter how reliable, one will either be damaged by a reckless carrier, or some weird problem may arise.  The important thing in that case is to immediately take care of the customer, and that is expensive outside of N America.  So that will be Spatial's call.   It is much more expensive to support markets outside the USA and Canada.

Hi Don, I have heard a VAC Amp' within the UK, one of the earlier models is owned by a HiFi Group Member who owns a 300B.

Another newer Model VAC is also owned by a Group Member, I am yet to be demo's this one.

I have heard Modwright as well other Brands that are not with a dealer distribution, it is not too strange for products to end up in the UK without the supporting networks behind them.

There is a fair amount of UK Audio Enthusiasts who are willing to look far and wide for their entertainment to be satisfied. 


@pindac Would it require a 240 VAC version or have most of the ones you have heard been US market 120VAC ones that someone was using a step up transformer with on your side of the pond?   I will say that I have the pair of prototype amps that will go into production other than some cosmetic changes to the cases and panels.  The circuit and power supply will not change as they are done.  I abuse the amps regularly, putting them on the bench and tweaking something and turning them on and off 10 times in 30 minutes.  Nothing has fazed them in 3 or 4 months since their birth.  So I am pretty darn confident if they arrive undamaged they will simply just work and be very reliable.  I/we wouldn't sell them if they were not very reliable.  But shipping overseas is always dicey, even with good packing.