I’ve had the SEWE300B amplifier in use for about 400 hours now. I could write on and on about it but the truth of the matter is that there is a short and sweet answer to “how is it?” It’s a clear and dynamic amplifier that presents an accurate and vivid sound field in audio playback.

The only other 300B amplifiers I have heard were two Cary amps in the late ‘eighties and early ‘nineties. One was an amplifier, the other an integrated amplifier. Neither were heard in my own system. I was very impressed with the sound, the SET nature capturing me first, and then I think the sound of the 300B tubes themselves. The basic sounds of these amps were warm and forgiving and inviting. Hearing these sent me on a search for an SET amp that I could afford. I had grown up on my father’s Dynaco tube system, and had been listening for a few years to a 1959 EICO EL84 integrated stereo amplifier I had bought from a friend (who had been using it as a guitar amplifier and was unhappy with the sound). Eventually I found Decware, talked to Steve on the phone and bought Zen amp #27. It didn’t sound like the Cary amps, but that
Type to enter text was great as they sounded uniquely clear and dynamic and I spent over two decades with Decware amps and speakers revealing in the many different soundscapes and tonal universes they can deliver.

I never forgot that 300B sound though. . . and always wondered what a Decware 300B amp might sound like. And now I know. The SEWE300B sounds marvelous.

For the last five years I’ve used a pair of Decware SE84UFO3 Monoblock amplifiers with all the 25th Anniversary mods. These amplifiers trained me how to get the best out of them and became my time machine and escape platform, giving me thousands of hours of musical enjoyment. I never thought I would replace them. . . until Steve announced the development of the SEWE300B. I knew I would have to hear one, and trusting Steve’s vision and innovation, I knew it would be a spectacular amp and if I heard one I would have to have one. I managed to order one and my intuition about this amplifier was right on. It’s the best amplifier I have ever owned.

My direct comparison to the SE84UFO3 Monoblocks with the 25th Anniversary Mods initially surprised me as the amplifiers sounded so similar. There was a shared clarity and a shared dynamic feel, from micro to macro dynamic playback. And as I grew more familiar with the SEWE300B and as the amplifier broke-in and seasoned, its distinct character became more recognizable. There was a feeling of easy “power” delivered to the Decware HR-1 speakers I have used for over 12 years. The SE84UFO3 Monoblocks with the 25th Anniversary Mods worked surprisingly well with the HR-1 speakers, but the speakers were better matched with the additional “power” from the SEWE300B. There was a teaspoon more heft to the sound of the lower frequencies, and a similar bit more detailed portrayal of the sound of a contrabass violin, cello, or electric bass guitar, and a bit of sparkle to the higher frequencies, a tiny bit more transparency to the recorded sound of trumpets for example—their sound burst out from the collage of accompaniment a bit more than the quite satisfying way the SE84UFO3 Monoblocks with the 25th Anniversary mods portrayed them. And I enjoyed the same voltage regulation benefit shared with the Monoblocks which allowed me to tailor the overall amplifier sound by using different combinations of voltage regulation tubes. The overall sound can be slightly lush to very quick and clean and many different points in between those two end points using the three different voltage regulation tube types and different brands of each. I would think any owner could find the right combination for their taste and system needs. Like the SE84UFO3 Monoblocks with the 25th Anniversary Mods the SEWE300B also has two bias signatures switchable for the input tube, and two settings for the speaker connections, and these also offer flexibility to the overall sound. An owner of the SE300B can explore many sonic possibilities with these switches. These switches and the voltage tube regulation set this amplifier apart and aid the owner to find the right set up for his system.

As is my nature as a tube fancier, I rolled a number of tubes in all positions except for the 300B tubes themselves, as I only have one pair of 300B tubes to use at the moment, the Sophia Electric Classic 300B in blue glass. Any change of input, driver and rectifier tubes is easily recognizable—the clarity of this amplifier reveals the characteristic sound of each tube. I bought the SEWE300B from Decware without tubes, and I found an excellent tube complement from tubes that I had on hand after much experimentation. Having decided on these tubes as a foundation, for the last two weeks I have been listening with enjoyment to new and very familiar musical material, both CD and SACD, and also to LPs. The SEWE300B draws me in and commands my attention, and I am loathe to turn them off and end a listening session. And I’ve suffered no listening fatigue.

I have used the SEWE300B with my Decware ZTPRE and ZBIT and ZROCK2 and really enjoyed the dense, vibrant sound. As the SEWE300B has a built in preamp stage, I spent an afternoon listening to the system without the ZTPRE  preamp. The sound was very nice, I did miss a bit of the density and heft that riding the gain from the ZTPRE provides. I tend to darker, thicker sound overall than others, and it was predictable I’d prefer the ZTPRE in the audio chain, but I am sure others would enjoy sound without it—a preamp is certainly not necessary with the SEWE300B to enjoy deep audio satisfaction, yet another great feature of this amplifier.

The bottom line is: this amp is more than just a keeper, it’s going to be the foundation of my main music system going forward. I’ve sold my SE84UO3 Monoblocks with the 25th Anniversary Mods, something I would not have imagined a year ago. Even though I feel the SEWE300B has a bit more seasoning ahead of it to be all it can be, I’m deeply enjoying its sound and flexibility and thankful to have it for all the hours of listening ahead.

Nice review, Lon.  Thanks for putting these thoughts together.  Your review provides a unique perspective on the 300B, given your history and familiarity with Decware.  It sounds like the 300B either met or excelled at your expectations, which is noteworthy for those who have followed this amp's development and wondered how it might turn out.

Now, if they you could only get your electricity restored.

I too was waiting for this review.  The leap of faith was successful.  Makes my wait only harder! Congrats on finding new sonic bliss as well as finding your monoblocks a new home!

Thanks, Lon.

Randy

I sure will @Tony, though I suspect my review will be on the simple side. I'm really new to this arena and have been chasing a sound quality. I can't really describe it other than to say I really appreciate clear, crisp, and defined. To paraphrase Justice Potter Stewart, I'll know it when I hear it. But gosh, there are so many moving parts ! I listen almost exclusively to vinyl and what a sound is coming out of that little Zkit tonight. Transporting.

Wow, four days! I bet you can't wait to hear you new enchantment maker!

I love and hate how the computer decides what I am trying to say, especially with close ones easy to miss like reveling and revealing. But at least revealing works OK. Really glad your amp is such a pleasure!

Just got power back and took a shower! Relief!

It was really hard to be without music. I wore my laptop battery down listening a bit but it was not nearly as satisfying as listening to any of the three stereo systems.

It's clear that the amp has really begun to bloom. Since the power came back on and my front ends warmed up a day or so I am getting great sound. I did some tube-rolling and at the moment I'm enjoying an Amperex 6085 in the input, RCA Gray Glass 6SN7 with converters as the driver tubes, and an Amperex 5R4WGA rectifier (with an Amperex pinched waist 7062 in the ZROCK2) and getting a rich and silky sound. Wow.

I have I estimate over 600 hours on the amplifier now, and the resolution and depth of the sound have come into a new zone, perhaps its final plateau of travel.

I have a tube complement now that I feel is laid back and spacious, yet not lacking any detail or drive. My front ends have never sounded better either, which has me now enjoying the most profound sound ever.

Here are the tubes in use:

"Sun" labeled Holland made 12AU7
3 75C1 tubes
RCA branded Holland made 7308
Sophia Electric Aqua 274B
Sophia Electric Classic 300B

The team of rectifier and output tubes from Sophia Electric is a very good one, these work together so well. (It's important to note that he ZTPRE has six 6085 tubes with converter bases within it, and the ZROCK2 had a Steve-supplied National 5963 within).

I'm thinking less of the amp right now and just treating the system as I normally would at last, and really. swimming in excellent playback.

I have sold and shipped my Monoblocks so no further direct comparisons are possible.

My conclusions from direct comparison and a five year history with the Monoblocks: To be honest the differences are likely more pronounced in my system as the Monoblocks JUST work with my HR-1 speakers and the sound is shaped by the efficiency of the speakers--giving me a more forward and tilted upward sound than the sound with the SEWE300B which is much better suited with its power for the HR-1 and has a flatter frequency response as a result.

The other difference in "character" between the amps is I think related to the "dual mono" nature, the separate chassis and power supplies. There's a "specificity" to the two channels with the Monoblocks which leqds to just a slightly more chiseled image of an instrument and a slightly more precise left and right and center to the soundstage. The soundfield of the SEWE300B is a bit more center-filled and there's a tiny bit of relaxation to the sound. The fact that there's a preamp stage to the SEWE300B probably also contributes to subtle differences.

What they both share are many characteristics but one prominently: they are very transparent as far as signal purity and each change of tube in the tube conplement is very apparent and the many different ways these amps can sound is fascinating.

Not something I wonder about.

The treble cut circuit made the Monoblocks have the frequency balance I needed, and I did not need more power as a result.

The SEWE300B has plenty of power for my needs and has ended all my "wondering" about other amp possibilities. Now it's more about tubes. Biggest question is about 300B tubes. . . Western Electric? Wathen? Steve says the Wathen has a bit fuller sound, and a bit more bass weight. As shy as I am about ordering from Wathen again, I might.

These updates are exciting and very promising indeed. This will probably be my last attempt at a 300b amp. I'm looking forward to hearing things.

Thanks Lon

Charlie

Your jaw dropping comment reminded me of the UFO25 thread that I read recently and the notion of a jaw holder to prevent injuries and the rendition of what it would look like.  Maybe we need one for Sarah too!

Well I finally decided to try an "audiophile fuse" in the SEWE300B and chose a relatively inexpensive one to try first, the ACME Ag/Cryo Fuse 5A SB 5x20mm CFC Series, from partsconnexion. About 31 dollars including postage.

At first I thought perhaps I had it installed in the wrong direction and that may still be the case, but after about four hours of play the sound has shifted and the frequency balance is less tilted to the high fequencies than initially. I rolled a few tubes and now have an Amperex Holland Bugle Boy 12AU7 in the ZROCK2 again, and a "Sun" labeled Holland 12AU7 in the SEWE300B, a nice slightly warm combo.

It's early to make judgments but I do notice an increase in "punch" -- a dollop of more dynamic shift, and there is a tightening of the attack of notes. I'm listening again (second time this morning) to Betty Carter "It's Not About the Melody" and there's a real precision to the rhythmic sense and a sense of accuracy to each enunciated syllable from this master vocalist.

I have an AMR fuse on the way from Germany to try soon. .. but so far I'm liking this Acme.

It's only been about fifteen hours on this fuse but. .. it's a bang for the buck option for sure.

Now I have Audio Magic M-1 in the PS Audio P15, PST and DSD Mk II, and ZROCK2, and Synergistic Research Purples, in the ZTPRE, so quite some expensive fuses upstream that I heard as each was introduced. The basic ceramic fuse I had put in the SEWE300B was a tiny improvement and it seemed to me listening to the SEWE300B at first that perhaps that was a bottleneck.

This fuse has allowed me to hear a bit more depth to the sound and everything seems a bit more "breathing"--the dynamic information is a bit more pronounced and instrumental images are a bit more chiseled.

It's all about a lessening of noise. Paying attention to the electrical quality in any and many ways is always a good thing. This is a nice improvement from a cheap fuse.

MY GOD it's hard to wait that long. I wager it will be worth it.

I put forth the pentultimate change to my SEWE300B: I gave up on cheap audiophile fuses (though the ACME was a bargain and a bang for the buck fuse) and put in a Synergistic Research "Purple" fuse five days ago.

A very good move. This fuse has brought a tonal balance and soundstage improvement that has me just settling into the music in a new way. This amp has become an even smoother, natural vehicle for the great signal coming from upstream.

I have only one more planned change for the SEWE300B: whenever they ship a pair of Cryotone 300B-WC. We'll see what they do.

Of course today the CSP3 that I bought from Joman is arriving and I'll put that in place of the ZTPRE and see what that brings! It's been a year of change here in my system but changes for the better!

So it's been more than two weeks now I guess since I went without a preamp. It has taken me a while to withdraw from a preamp in the system. . . I keep wanting to adjust that one more gain stage and then realize I don't have it and then re-adjust the other stages.

But the truth of the matter is that with the preamp stage of the SEWE300B a preamp is NOT needed and the sound is great with a ZBIT and ZROCK2 in between the source and amplifier. Great. . . may be an understatement. Clear and dynamic, full-bodied and atmospheric. One can get all of that or combos of these characteristics with tube-rolling and gain-riding.

And music comes out. . . really satisfying and involving music. And that is what it's all about. I keep buying music, and in fact I want more and more with the SEWE300B in place and broken in.

Now that I don't use a preamp in this system (and have two that need minor repair to get up to snuff and likely put up for sale) I find I have dozens of tubes I won't be using. Sigh. I guess I'll put quite a few up for sale. I do have debt still to work off.

Life is good. I only wish the SEWE300B were available about ten years ago. Where's that damned time machine anyway. . . I thought it was in the root cellar, but that was just in a dream I had. . . .

Nice discoveries Lon, and I love: "Life is good. I only wish the SEWE300B were available about ten years ago. Where's that damned time machine anyway. . . I thought it was in the root cellar, but that was just in a dream I had. . . . " With all your experiments, quite a tribute to your beautiful amp!

I am always re-surprised when I love taking my tuned up CSP3 out, and then love it after I put it back in, pretty much every time including some tube and/or cable tuning to get that love.

So far for me anyway, often the benefits can still outweigh the down sides. But I get your current preferences of no pre with your SEWE300B, especially still having gain tuning adjustments with your ZBIT and ZRock2. The pattern of three pre stages for me has gotten less clear also.

Over so many years, my Torii IV having been tuned up for open resolution that is so musically awake... And these days, with the right amp tuning and tube sets, using spacious and lively 300B and 845 tubes in my non-Decware amps...the amps seem quite awake and musically balanced on their own. No doubt to me, if we can lose the old 300B amp habits of rolloff and syrup, there is some amazing potential with those big Triodes! Anyway, with more resolved space, density, complexity, and speed from the amps, I often use only the ZBIT, or the ZBIT with either the ZRock2+, or CSP3+.

In fact, running all three for a while, I took out the ZRock2+ the other day. After resolving and speeding its sound, it seems more prone to subtle distortions at times. Guessing the clearer paths may be showing and/or contributing to distortions easier. Probably a big part... within the increased resolution and clarity, increased speed creates more powerful transients, pushing occasional audible distortion hits more, an issue in my setup at my loudest listening levels. So I took it out hoping to do some tests and see if I can adjust it. With some tube and baseline gain level changes in the ZBIT and CSP3+ the system sounds great without.

It is important though, that the distortion edges here are to do with my preference for multiple pre stages before whatever amp I use, and I have a high volume room space... so my amp's power relative to my speaker efficiency at high volumes is near edges.... I am pushing lots of thresholds.  

In my late-night-dark-room listening sessions, with playlists from different recordings and mastering, I am always just on the edge of audible distortion blips on limited note hits of limited recordings....but being near the edges, less obvious distortions are there too. I mainly just need a few more dB of headroom I think.

That said, seems I fall into distortion easier, and at a little lower volumes, with all three pre stages... the ZBIT, ZRock, and CSP3. Take one out and less of it, and take two out, a little louder with less edge again.

Also, the ways I adjust the pre stages for speed, warmth and lucidity, it seems each is close to, or being pushed itself... and in succession, they progressively add push to the next, each adding density/hit to the signal along the way. Guessing the voltage from each progressively pushes the other's edges along the way. And not least, transients becoming relatively faster and more powerful, this finally pushes amp thresholds at lower average volumes.

Long lead up to.... Logic would point me to using less pre stages to help solve this distortion edge thing. But, with care, I still love the combinations, how each of the three contributes in their own individual ways. And tuning those complexes together can be beautiful, as I know you found at different stages of gear and your journey.

It does not surprise me taking out a pre with your SEWE300B though... Not only is it a great amp design, a refined and awakening pre stage part of that great design...But also... those big Triode tubes (at least if the design lets them breath)... To me they can be incredibly elucidating, yet comfortable within that awakened bigness, including big complexity, big openness, and big speed/dynamics complexes. The amazing space, with powerful and smooth density, and importantly, a density that can allow for highly developed harmonic complexity... beautiful how they can be set up to be so clear and spacious, and so rich without tending to hardness.

And when that is all working, everything in front shows for better or worse. I am always sort of shocked how things can be truly great, and then just keep getting better with exploration. What an amazing life-enhancing gift lively music in the home can be... I don't know if I ever would have gotten so much from it, truly "harmonic medicine" to me, without Steve and Bob, and you, and others contributing to this friendly forum. Another amazing gift.

As usual, I am enjoying following your impressions and unfolding path, lately with your new and beloved SEWE300B amp!

Yes, it is fun having shared a lot of exploration with pre stages in and out of the mix. And it is true my stuff is more resolving and nuanced due to all the modification work I continue to explore... As an example I have used before, I finally could not use the ZRock2 I bought from you (as it was then) after the initial glow wore off. It was just too slow and unresolving in the context of the rest of my setup at the time, the rest having been musically opened up for more immediacy and resolution. This made the Zrock off balancing in my setup, where it might not have been in others. So I think your point as to pre stage choices being different for us is well taken. Also, I can easily imagine the pre built into the SEWE300B being really, really good on its own for bringing out great harmonics and space with density and nuances... some things my modifications have been devoted to.

Relative to your 300B being better for your HR-1s, it is amazing to me how 6-8 300B watts can sound so big, smooth, dense, and resolved...  louder feeling, pushing the HR-1s more optimally. I am thinking part of the amazing sense of power is from the tube, all on its own, generally being bigger in most areas of sonics... smooth and dense, expressive dynamics...and with with big space and complexity potential... just a big sound all around before looking at watts.

Still trying to get more clear on what I am hearing with 300Bs, but they seem to occupy a different enough zone that the tube is of itself. I am getting similar qualities from my 845 power tubes, an even bigger triode, but only one pair of those, so can't compare yet. But changing the 300B drivers in front of the 845s, or the 6SN7s before the 300Bs, produce pretty "big" sonic changes... I might say changes similar in bigness to how the big triodes sound in general. Equally, what comes before the amp is more notable and has more distinct gain tuning sweet spots here, often with less latitude than I had with my Torii IV... indicating the sonic power of these tube's also to me.

Leading me to: I expect for me, you, and others, the sonic qualities these tubes bring to the matrix (in a transparent platform) have similarities with what we want pre stages to do for us with some other amp types, the pre stages adding potential for tuning lucidity in dynamics, density, weight, complexity and space. I'm thinking that a nice 300B tube, in a fairly transparent design, can already do a nice job awakening these sonic qualities, so that adding more before with a pre stage (or three) can potentially be too much... thickening/coloring the sound. In other words, aside from gain tuning abilities, which I love, is a decent 300B tube similar to a well tuned pre stage in terms of what it can bring to the whole.

Part of what got me on this track was, at 200+ hours, my 845 amp is filling in down low... not fully resolved yet, but the bass, and bass in the balance, is coming in and up, so the overall sound fuller, warmer, and thicker. For the last few days, I was having a hard time with getting it open enough with tubes and gain tuning all three stages in front of the amp. This is part of why I first pulled the ZRock2+. Then I pulled the CSP3 after your posts talking about pulling yours, along with your comment about mine potentially being different, which I think is true having made things as naturally fast and musically resolved across the spectrum as I can. But what would it be like without?

Pulling the CSP3, it was different with just the ZBIT, but not better per se, the CSP3+ adding its own flavors, but with really good harmonic complexity. Other than that, the overall tone was quite similar with and without, but I missed the resolved complexity, and tuning ability with gains adjustments on the signal.

So while out, I decided to try to open up the CSP3 a little more, to see if a pretty subtle signature change might be amplified by these amazing tubes, while making the CSP3 a more powerful tuning tool with more flexibility.

I had a little 0.022 Miflex Copper Oil cap, with some smaller caps bypassing it, as a filter between the power supply caps and the internal VRs. I decided to take that Miflex out, the oils having nice complexity, but a little slower, smoother, and richer than Miflex Coppers that don't have oil (like in your amp), so thinking pulling this oil cap might head me in the right direction. With its bypasses still in place, I hoped the sound would be a little more open, faster and more translucent. Those bypasses are a fancier 0.01 Solen, and a .0033 Mallory 150, and those alone as this filter, the difference was pretty notable... doing what I hoped a little more than expected.

Now there is no question the CSP3 is helping me with this amp at this stage of burnin... giving me more complexity and flexibility for density and dynamics without getting too thick. And this seems like it might corroborate how powerfully these big triodes impact the overall sound... one little low value cap pulled in the stage before the big triodes, an encouraging difference.

I am growing really affectionate for these tubes as they too burn in. It is hard for me to keep any of the 300Bs I have in though, they are all so intersting in their own ways... so it is taking a long time to burn them in!

Looking forward to your future updates!

Will

Nice Lon!

The UFO-25 sound is excellent--if they fed the HR-1 as comfortably as the SEWE300B I probably would not have taken this journey. Still the resulting sound for us both has been wonderful. We owe Decware and patience a lot.

MarLin, I have a feeling the SEWE300B will not disappoint.

PS Audio released a new firmware for my DAC and MAN what an improvement. From hour one it was a great revamp and 38 hours in it's even more so.

Unfortunately, clutzily reaching around to install the firmware I managed to knock my Decware 9 pin straightener off the top shelf and before it reached the ground it clipped the very tip of the Cryotone long plate tube in my ZROCK2 and rendered that useless. I replaced it with one of my Amperex Holland Bugle Boy 12AU7s and really enjoyed the sound. Made me think to replace the Cryotone on the input of the SEWE300B with another of my favorite 12AU7s, a Sun labeled Holland, and wow, another great sonic structure. With these Holland tubes in comparison to the Cryotone there is just a touch of appealing warmth, and the soundstage is less pushed forward with a touch more depth. I like this! I have another Cryotone on order but . . . it may go elsewhere. I love the tube complement in place now and what is revealed by the new firmware (Massive).

Love your characterization Lon! Keep on spinning!

Lon said:

I did some tube rolling and found excquisite liquid rich sound with a GE 5963 from Steve in the SEWE300B and a Brimar 12AU7 in the ZROCK2. The fatiguing characteristic has not re-appeared.

Hey Lon,
When you described your listening experience as one resulting in fatigue managed by switching various tubes, I was struck with your assessment and solution.  Is this a common clue, listener fatigue, that something is not optimal within the system? It is a novel means of evaluation for me.  Sometimes I listen to my system and feel energized and excited by what I hear; listening fatigue reminds me of other times when I have gotten bored.  I might have attributed that to a poor choice of music or that I needed more rest, but it never occurred to me to suspect that a recent rolled tube or combination of recently rolled tubes might be the cause.

What I think of as listening fatigue feels to me like my ears have been "hammered" (over vibrated along with transients) a little too hard, resulting in dulled hearing and when bad, even some ear canal inflammation. Most people seem to attribute it to highs, maybe like Lon in this case. In my case, the bass can sound pretty right in all ways, but be a little "too good," and that is where I can usually solve fatigue... chill down and/or articulate the bass a little. Or if the sound is just intense in general, then milder tubes in general can fix it.