Hey Steve.  Any more insight into "hum" from this amp?  I would run this amp with my K-horns (~105db sensitivity).  If there is hum, would it be audible from the speakers when music is playing but quiet?

I just checked out the dimensions of the ZF15L and those things are huge.  They take up more space than Klipsch Cornwalls.  Wow!

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No volume controls are logarithmic as are speakers.  

With a 1 volt input signal, vol control maxed (5:00) the output is 5 watts. Vol control at (3:30) is 4 watts.  Vol control (2:00) is 1 watt.  Vol control at (noon) is around a 1/4 watt.

Now if your question is will it sound half as loud when the volume control is somewhere around half way when compared against all the way up, the answer is yes.

Everyone seems to be understanding the design except DancingSea who is hung up on the word EQ and is using it to get other peoples panties in a knot who read the SteveHoffman forum and trust me that is not productive or helpful to the design.  

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Unity gain starts at 12 and by 1:15 equalization just begins to become detectable. That is what is considered the magic spot in a ZROCK2.  If you measure this spot it measures within 1dB of flat. I don't understand why it is so confusing.

The reason I said I had no plans to mention the ZROCK2 circuit I used in the gain stage is because people could have the same missundstanding and get hung up on the term EQ.

If you look at the frequency response I just published it is concurrent with what I've stated which is that the frequency response is within 2 dB of flat.  Obviously the response is EQ'd by 1 db in the low and high frequencies... or it is just a natural anomaly of the circuit design. We won't know until I bypass it and remeasure.  

Please look at the Stereophile measurements of 300B (or any) amplifiers. There is a simulated speaker load, usually the black line, along with the standardized measurements. Guess what, it's not flat. No moving coil speaker is. Do we call our speakers EQ'd. I guess we better so that no one thinks the manufactures are hiding stuff ; )

I could if I wanted make an amplifier that had the opposite simulated response so that the Stereophile simulated speaker load measures a flat line.  That would give the speaker a flatter response so you see the rabbit hole here I assume.

No offense DancingSea , I read all your posts on SteveHoffman forum. Demonizing me in other forums because my transparency isn't up to your standard is a good way to get on my bad side.


Steve

"dummy load.  The name comes from people who think this is how an amplifier measures on speakers"            

Thank You, Steve. I enjoyed that one!

Brian

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DS, above is a quote from your fingers. Please take note and adjust.

From my point of view a buffer gain tube stage was added to the 300b created by Steve Deckert and can be adjusted by tube rolling. That is all.......

John

None of the other Decware amplifiers required a second gain stage to bring the input sensitivity up to a useful level like the 300B amp did. It was because it needed an additional stage (tube) that we went down this path. For our other amps it would be best to just buy a ZROCK2.

Additionally, if I did the same thing to our other amps, it would be a flat measuring non-adjustable ZROCK2 which means it's not a ZROCK2. And even then if you wanted the tone shaping abilities of a ZROCK2 you would still have to use one just as would be the case with this 300B amplifier.

My whole fascination with the ZROCK2 circuit in the first place is what it does to the imaging and sound stage and midrange tone. That is not a function of altering (EQing) the frequency response because it happens before the ZROCK2 really starts shaping. It's just that I knew the combination used in that ZROCK2 gain stage with the particular caps and resistors and voltages and so on creates (extracts or reveals) a coherency that is not there without it. As I tried to convey before, it's more about the phase & timing effects across frequencies created by the values and placement of the parts than it is about actually changing the frequency response.

Every amplifier is it's own device. What works in one will work differently in another. There are no plans to try to repeat this in our other amplifiers because we would have to add another tube to each model and you would still have to buy a ZROCK2 if you wanted to do any shaping.

Steve

will - very nicely said - cheers - scott

Steve,

Will these bad boys hit the market cherried out, like a UFO25? Or will high-end caps and other 25th stuff be an add on?

Thanks.

Why does he listen to this?

I am listening for anything bad to happen. I am listening for mud. I am listening to how the amp deals with excessive heaviness. If it doesn't sound excessively heavy then it's doing well. I am listening for textures and seeing how long those can hold my attention against such a predictable and monotonous / repetitious experience. Is the amp deep enough to make this sustainable over time without having to change albums.

It's easy to evaluate bass performance on something tight and staccato but how does it fair on the opposite?  Something slow or veiled would sound muddy on this.


This is why.

Thanks for the response, that makes a lot of sense. I'd be perfectly fine with 25th mods baked into the price!

This amp sounds like it's shaping up to be a real beast. I, like everyone else in this thread, love reading the updates. The whole engineering process is shockingly interesting to read about.

I'm hoping to swing some Cornwall IVs sometime around the time this amp ships...or likely a little bit after. At 102db, I'm hoping to tap into some of that magic you're talking about with the 300b Sarah!

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I'm triggered by hum. Pass the candle.

I mean I'm not going to get this amp regardless, but I really appreciate that Steve has the integrity to mention something that a lot of people would ignore if they noticed at all.

Me too CAJames, hum can be a hard one for me. Years of up and down subtle hum with my Torii, and getting it more fully solved a few years ago, when it shows up, I realize I have grown less able to take that frequency range. Putting a DAC I had not been using for a while, I got a ground loop recently. I could hear it from the seat a little, and realized I am indeed "triggered" by hum.

UPDATE MAY 22 / 2022

Experiencing it

We’ve come to the point where there is no more soldering or experimenting. Just experiencing it now. Experiencing it on my huge library of speakers. Experiencing it with different cables. Experiencing it with the different tubes. I am doing the same thing you would be doing had you just unpacked one a week ago.


Living with it

This is where I really know if I got it right. How consistent is it across this wide range of speakers and with different sources, and all the other variables. I am used to this, and have a reference with all our other amps, so the bar is set high. If it passes, it will be because I didn’t think about it.


Different speakers

So far there have been some interesting observations with respect to synergy. Sadly I didn’t invent something that can be synergistic with everything but it's always fun to try... That said it’s far from picky. All of our speakers sounds great with it so far, it’s just about “at what levels”. The Zen Master Series baffles will play loud with low distortion and there is an amazing synergy there. The power and scale is there for anything. No subs required. 

Smaller less efficient speakers in the mid to low 90’s sound great at low power. Incredible in fact. But because the amp has such a long ramp for clipping, it is easy to turn them up louder than you should and then become puzzled why they sound a bit compressed. Interestingly, the least efficient at 88dB is my House Speakers featuring the top of the line Scan Speak drivers and my own crossover. These actually get louder or to phase it more accurately, put more music in the room than the Tube Tots with the same 4 watts from this particular amplifier.

I will continue on this path until I have tried all my speakers.  

Think of this process like going to the same concert hall and listening to the same artists but each time you are setting in a different seat. With this many perspectives on the music (recording) you are certain to come to a higher level of understanding of the music. In this case, the amplifier.


The EQ that isn’t there…. Tube has rolled response, now it doesn’t.

As I mentioned in my prior updates, I took over 60 measurements for my own knowledge which turned out to be very interesting for reasons I discussed. All of these were taken into an inductive load instead of a resistive “dummy” load. Since the dummy load is the standard that people are used to when making comparisons, I will be re-measuring the amp on the other station with the resistive load and evaluating the differences. In any case, Because 300B amplifiers measure so poorly compared to many other amplifiers, I will be publishing the full specs and measurements when I do the web page. Think of it as a de-knotting tool for your panties in the spirit of full disclosure. ; )

You will see that many 300B amps suffer into 4 ohm loads compared to 8 ohms and 2 ohms isn’t even considered. It’s not the difference in power across these impedances but rather the changing frequency response and distortion. The tendency I saw in several amps was to dramatically roll the top end as the impedance drops. Holly crap batman… it’s a good thing I didn’t know this or the tendency to become microphonic for the past 30 years because I certainly would have used it to bash 300B tubes in defense of Decware’s choice to go with a $20, 2 watt tube instead. A tube which btw was $2 ea. in 1998 when I found it.


click to enlarge


By some miracle this amp measures the opposite and measures the same from 2 ohms to 16 ohms. That makes it a TRUE BONAFIDE ZEN TRIODE AMPLIFIER. All Zen Triode Amps can drive a 2 ohm speaker without sounding like crap. This is going to make it a lot more honest in the real world compared to these other amps I looked at. So that is exciting. It happens naturally, no complex crap to make it happen. When I say complex crap the image in my mind is a circuit board full of relays and logic chips to rearrange  an EQ circuit differently for each setting of the output taps… a true sonic nightmare.

The bass, mid bass, midrange is within .02dB of perfectly flat into this inductive load! Then a mild presence rise in the treble that we can hear. Couldn't ask for better with a 300B.




A preamp makes your source sound better - also can be that magic bullet for imaging and sound stage depth.

And this is where the meat of tonights update lies.  It is no secret that Decware amplifiers sound great without a preamp. But the reason that statement is true is because so many preamps sound worse than a Zen Triode Amplifier.

This is why there is so much pressure on the source component to have a “real” analogue output stage design so the music doesn’t sound lean or thin and so you get a good sound stage and imaging.

Because this tube requires more voltage swing and a preamp of sorts (additional gain stage) was needed a great opportunity presented itself. First of all, with this gain stage, it will be an absolute certainty that preamp will not be required to make the amp sound better because the gain stage IS the preamp. That means we eliminate an RCA cable and connectors and a ton of variables that come with a second component. But more importantly it means that we control everything about that signal path. How it sounds, and how it mates to the amplifier and the resulting synergy have been carefully crafted in a way that would have been unlikely to happen by chance with separate components.

This is particularly crucial when it comes to overall tone, dynamics, and imaging / soundstage depth.

Some of those rare unbelievable systems that exist on the planet are the result of years of trial and error component/cable matching until nirvana accidentally happens. That comes as the result of the preamp and cables associated with it. So this has been taken care of for you making it a unique model in the Decware line, as well as a very cost effective one.  

Low volume ultra high res listening

The imaging depth of this amplifier is world class. The depth is only possible by having that synergy between all the involved gain-stages that combine to drive an output tube. This is what I was talking about with the switch.





As you can see I eliminated the first Normal / Bypass switch a while back. Now it's just between the N normal and the : ) Enhanced. I have not liked it in the N setting on a single pair of speakers or with a single source or with or without a preamp. As predicted I will likely delete it completely.

I have been visiting the switch with each combination of speakers/cables/source and going between the normal and the enhanced setting and every time it is not even close. Normal setting is very good, but images like an amplifier with no preamp. Enhanced on the other hand is like the guy who spent 20 years finding the ultimate preamp and cable combination to create that holographic sound stage that you thought didn’t really exist - only in audiophile hyperbole or Greek mythology.

So what I am saying is that the depth of the imaging is insane. If your speakers are up against a wall, please don’t buy this amp ; (.  It would be such a waste.

All of this is happening from a stock CXNv2 and a pair of Decware RCA cables tonight. It shouldn’t but it is. This is called keeping one foot on the ground at all times. Someone asked if I have listened to vinyl or tape on it yet. HELL NO. That would be like trying to fix a water heater without tools. The tools are the mediocrity of the source components that may be used with the amplifier. Hell -- switch setting A -- the one I don’t like because it’s like someone stole the sound stage, would sound great on Vinyl as long as I never heard switch setting B. I prefer digital for setting up an amplifier due to the consistency and the obvious fact that this is what most will listen to.


Anyway, I love setting this amp up with the speakers pulled out into the middle or the room and pointed at my face only 6 or 8 feet away. It’s so holographic that it feels like being in space. Your room isn’t part of the sound like this, and the depth of each note and placement in the grid is just astonishing. It’s at this point that I begin to think about Danny from GR Research who doubled down on his controversial video calling out reviewers for not having worthy listening rooms. He was somewhat right. I wish everyone who doesn't have a well treated space would go to his place (or come here) and listen, because he knows as do I that the most audiophiles will never have a clue what is actually possible in a 3D listening experience until they take it out of their living space and create a dedicated treated space for the stereo, which means having two stereos. and another room somewhere... A big commitment to make without any real incentive.

I know for a fact that many people had they first heard what is possible would consider doing whatever it took to create a dedicated listening space that could recreate sound this way. Sadly to most stereo is like television. A flat entity associated with the boundaries of a living space where it remains out of the way so you can live in the space. AKA entertainment.

To me while I recognize that application, this is not entertainment. This is a real F-IN spaceship or time machine (same thing) that will give you an experience you didn’t know about -- that once you’ve had it you can’t not have it. It’s like learning to walk. Once you accomplish it, you can’t go back to crawling. It’s just not possible.

So I have to respect Danny for doubling down because it’s actually true for many what he says.

I bring this up, because this sculpting the imaging is the most difficult and time consuming part of the design process and we know very few will actually experience the full potential of it. As an artist I feel like I am painting in color with great contrasts and subtleties with the color palette and 80% of my audience is color blind, not because they can't see colors, but because they won't take off the shades.

Sound wise at last comparison this was getting dangerously close to the same level as the 25th Anniversary Zen Triode amp, and now that it is finished and nearly burned in, it’s getting hard to imagine that it’s not as good or better. Certainly it IS better if you don’t put a preamp with the UFO25 so there you go.

The T6 speaker




Tonight I went from the House Speakers to a polar opposite, a single driver crossoverless stand-mounted bookshelf prototype called the T6.  And at these intimate volumes the silkiness and depth of each note is so satisfying it almost feels like you are listening to music in slow motion.. By that I mean if music were video, and you watched the video in super slow motion and let your mind get lost in the amazing detail of physics as the picture evolves frame by frame - like when a bullet intersects an object and the whole scene takes 30 seconds to watch…

Just a different chair in the auditorium… and I can smell the varnish on the cello. These speakers are magical on this amplifier up to a modest volume. They are around 93dB/8 ohms. If I play them any louder than the House speakers on this amp (88dB 8 ohms) I stop liking them. You can't have too many speakers when you are testing amplifiers. Anyway, you will see these jewels on the web site soon. Tube Tots were a big success, we are already nearly out of them so another 30 pair is under way. This speaker is a touch better. It's a really nice match with the 2 watt Zen Triode amps and amazing with the TORII's and ZMA.

So that's it, just listening and listening. Still amazed at the smoothness and tone's ability to dissolve my pickiness about recordings. More stuff sounds good with this amp than any other which is to say it is a more forgiving amplifier and is doing it without dumbing things down.

Steve

This is that time of night when the black hole begins to open up between the speakers... so in the interest of science I set up another test.

I put the T6 speakers less than 4.5 feet apart. They are the center pair of speakers in the picture. Have a look at the picture for a minute...


click to enlarge

I just got a sound stage from this amplifier on a pair of speakers placed 4.5 feet apart that wrapped around the room past my shoulders.  In the picture this is impossible to show because the picture isn't wide enough.  But to over simply things, picture the outside pair of speakers (DNA's) playing with a huge arc of sound outside and between the speakers.  

This is what I am hearing  and it's all from the center pair of speakers in the picture. It was so insane that the Audio Gods just showed up. No shit! Great energy is here and so with a high five and a nod off they go and here we are blessed by their interest in sound.

I have to laugh because when they left the room a few minutes later they pulled me outside myself and let me read this post from a skeptics point of view who doesn't know me and -- holy shit does it sound like a giant load of crap!!!  

But... we both know it's not a load of crap.

I agree with whoever said "if I had only two years left, I would take an amp over everything else." Same here. Absolutely. Over everything. It's the spaceship of the soul and that's how I approach it. You have to understand there is no benefit from putting this much time and passion into a design if it didn't have a higher purpose beyond money. This will create the same glow that you see in the tubes inside your heart. : )


Have a great night and happy listening! I'm almost feeling guilty.

Steve

I am listening to it now and in my mind I can easily overlap the CSP325 and what happens is it is making the CXNv2 sound like the HOLO Audio MAY dac.  You have nothing to worry about. Everything just got juicer. You're now swimming in it which is only possible when air achieves the density of water or you achieve the mass of a house fly.

My favorite thing about that preamp is how it shows you the perfect input level from your DAC via the VU tubes.  It's a masterpiece for those who want complete control over the gain structure. But getting the source level set right is what sets the stage for everything thereafter so this preamp is designed to show you when it's ideal using those cool tube meters.

Steve

To sleep—perchance to dream. Ay, there’s the rub!

Another exciting update. I can't wait (well I can, I will, no option) to hear this TRUE BONAFIDE ZEN TRIODE 300B SARAH AMPLIFIER with my HR-1.

I can't afford a fully treated listening space--that would be too expensive, a cost I can't pay, a divorce--but I have done the best I can which is an enlarged near-field listening space and I have achieved some amazing sound. Actually my SE84UFO3 Monoblocks with the mods are amazing me every day, and I've spent a few years now learning how to pilot them to the further reaches of sonic possibilities. I bet I can get even further, deeper with the Sarah.

Keep the updates coming!

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So, I guess the 6000 dollar question is why would one choose the UFO25 over the 300B, or vice versa? The watts? The preamp? The price?

My best guess: The UFO is already proven. The Sarah has much to prove, and many are willing to give it a shot, solely for love the 300b tube. I've never even heard one, but people go nuts for it.

I think the $6k was a reference to the UFO25th w/ CSP325. The 300b will be far less coin than that.

The 300b, being a single ended triode, low watt amp, is more akin to the UFO than it is the Mystery Amp. There are lots of things going on with the Mystery that account for the steeper price tag.

But yes, sonically, the 300b should be one for the books!

Whether or not the new amp offers balanced input option, the same thing can be accomplished with the outboard device called a ZBIT, which has an output level control. A balanced input would be fixed.

Steve I have ordered the DHC-3 blue power cords for The RACHAEL and ZP3, are they appropriate?

Since we are talking AC I'd also like to ask in a large 120 apt building what would you think more beneficial, a power conditioner or a regenerator?

XLR vs ZBIT...I've been somewhat following the threads where members talk about balanced XLR and the benefits, as Paul McGowan explains, distortion/noise can't pass along that balanced XLR input to the end point...noise is more prevalent and a byproduct across RCA.  

2nd observation, XLRs are offered on Decware amps, and XLRs "can't have noise" so, of course, I ordered my Torii MK5 with XLRs...then this and other members and threads say to just use a ZBIT, does the same thing...except that idea AGAIN goes against many of what you say should be avoided...more circuits, longer runs, reducing distortion/noise at all costs...but then isn't one introducing all of the unwanted circuits, longer runs, allowing noise across the RCAs required with a ZBIT configuration?

How is introducing a ZBIT in the circuit NOT blasphemy towards doing everything that putting XLRs on an amp and a DAC is all about?   Why isn't DAC to AMP via XLR (one set of cables) superior to 3 sets of cables (2 sets being RCA) and adding boxes (ZBIT + Zrock, etc)?