Steve, Exciting, and expensive, stuff!!  What happens to the sound if you substitute the 25th anni. modified CSP3 for the ZTPRE rather than adding it to the chain which includes the ZTPRE?

Great!, Steve. it seems a shame to be forced to listen alone. There are those who are anxiously waiting to be able to join in the fun and pleasure!!  If you get my drift  ;)

Steve, have you tried the UFO25 or UFO325 with the S3HOXRS speakers?

Nothing official has been handed down - only estimates and assumptions have been tossed around here. May still be a bit premature for Steve to commit as technically the amp is still in development.

Yes, all speculation at this point.

That's great news Steve! I know there's more than "a few" eager to know the final details and possibly place an order.

Tonight I'm A/B testing the SE84UFO25 Anniversary amp against a 25 watt OTL amp that I built!  It's a $20K tube amplifier with anywhere from 20 to 50 watts depending on the speaker and bias settings with 0.03% THD and an output impedance of .5 ohms... meaning death grip on the woofers.



The OTL is an exhilarating amp to listen to because of its combination of power and transparency... a true reference amplifier with only two output tubes per channel!  Gotta love those low impedance 6C33C triodes!  They were used in Russian ICBMs so rugged is an understatement!

I have to say that SE84UFO25 is holding it's own handsomely despite being only 1/10th the power it is hard to notice any difference in size, weight, scale or volume at my normal listening levels. The OTL is male with great absoluteness. The UFO25 is female with surreal magic spells that cast themselves upon you.

It's hard as hell to say which is actually better.  One has no output transformers but uses feedback, the other has no feedback but uses output transformers. I actually think the bigger difference is the even order vs. odd order harmonics each amp has.  Some will prefer one some will prefer the other some will enjoy both. The point is that after 25 years we've taken a Zen Triode Amplifier to this level and it's for real!  

Can't wait to start shipping these baby's and start hearing everyones reports!

Steve

Wow, that's exciting news!

Now I want to try a pair!

lol..

Still waiting for the "change" with the production sample, and despite a few more days and another 70 hours, no change.  I'm convinced it's the attenuators, so this weekend I will remove and replace them with the Decware Attenuators. I guess I've grown spoiled over the years with our attenuator.  

In our attenuator we use ultra low-noise thin-film nichrome surface-mount resistors rated nearly 10 times the resolution as 1% metal film leaded resistors used in most attenuators. These resistors are so good by comparison that you can stack dozens of them in series and hear no difference between the series string and the single resistor.  Up until these resistors became available the only type of attenuator worth using was a Ladder type which has only one resistor in the signal path at any one time.

Since we could no longer hear the difference between the ladder and series attenuator using these resistors some realized (and we recognized) it was possible to take it even one step further by almost eliminating all the circuit board traces. This was done by positioning 20 of these Nichrome SM Resistors in a circle as small as possible so that the end-caps of each resistor touched each other. The circle is soldered together and the gold wiper is then swept across gold pads at the end-caps of the resistors. This puts the wiper within a few thousandths of an inch away from the end caps of the resistors. It is the simplest most pure attenuator design God will allow. And it sounds like nothing is there, which is what you want.

Neither DACT or GoldPoint or anyone else do it this way, and it's because it doesn't LOOK impressive and is fragile. Well you know me, I don't give a blank about any of that IF it sounds better, and it does.

I have our attenuators custom made for me in Japan. Of course there are dozens of Chinese clones on ebay.com. My guess is that if you got three of the fakes to ensure at least one of them worked properly, even without the premium resistors it would probably still sound respectable.

Shown below is one of our attenuators I've disassembled so you can see the simplicity (zen) of it's design.




In the "real world" where most of our amplifiers live I usually recommend the standard carbon volume pot over the attenuators. The reason for this is that the amps are so transparent the warmth of the carbon pot is kind to mid-fi digital. The SE84UFO25 is not a real world amplifier. In fact it is an out of this world amplifier that is magnifying the differences in attenuators to the point of ruining the entire amplifier.

Anyway, I'll report the results once these attenuators are installed in the production sample.

Steve

LR - this is the only attenuator we have used since about 2005 so if you your amp has an attenuator, it is this.

Well I removed and replaced the attenuators and can confirm that was the entire problem! The incredible sound is BACK!  

The high-end machined attenuators I hoped would work looked like a million dollars, most fitting for such a special amplifier. Sadly they turned out to be series type and used conventional leaded low-grade resistors and circuit boards as I probably mentioned earlier.

It's amazing how large the difference is. Now the production sample sounds exactly like the prototype and I mean exactly. Nothing can proceed until that type of consistency happens, because consistency is the oak tree of success.

You know you have a great design when you can exactly replicate it. Remembering back when I was just another D.I.Y. amp builder, I can say it's pretty easy to be proud of yourself when your amp project is finally completed and sounding the way you wanted it to but it is damn humbling when you try to build more just like it and they all sound different. I've always said you know you're good when you can build the same amp five times in a row with identical results. You know you're really good when you can build it 25 times in a row with each and every one sounding identical. Even then, your amps don't become great until they stay in service for 25 years without unforeseen failures which is why this 25th Anniversary amp is so dear to my heart.

I'm listening to it now.

It's ear candy. Like a sweet new chocolate that the world has never tasted. Each note momentarily hangs time so you can enjoy it's full decay.  It's like hearing music in slow motion and live at virtually the same time supporting the sense that there's a multidimensional element to it.

I've been listening to this amplifier for weeks and until this KEY of a new attenuator unlocked the lock placed on it by the old attenuator, there was absolutely no multidimensional element to the sound. This is what separates this amplifier from virtually everything I've ever heard. See how fragile this is? And Lon is right, your room is not going to stop this element from dominating your listening experience.

Time to do some levitation...  and marvel at how much information is actually captured in a good recording. Not even the engineers had any idea in many cases.

Listening to the same garden of music during this development process helps to hear what changes when it changes.  Between last night with the the old attenuators and tonight with the new, the sound can not be contained in the listening room.  It comes out into the surrounding space with a seductive quality that was never there.  It's so much better it's just ridiculous.

To maintain context, this is an amplifier with 1 capacitor and two resistors in the signal path. The inferior sounding attenuator just added between 1 and 24 more low quality resistors to the signal path and the additional solder nodes was equally devastating. Perform the same test in a solid-state receiver where each of 8 op-amps have 27 transistors and heavy feedback loops with large value electrolytic coupling capacitors between the many stages and you will hear no difference between the two attenuators.  This should give those who have never heard such a good tube amp a basic scale of just how much better sounding it really is.

Steve

Yea, LR, I know it too, as evidence by what Jeff has already accomplished with his...  it will be a fun journey and I look forward to it. I already know what it's going to sound like, because I can hear it in my head as I write this. The word that comes to mind now as I listen to that... is... "exhilarating"... hard to turn off.

Steve

I like your listening tips. For once I know these artists from earlier. Both Askvik and Boel are norwegian. An additional tip would be Radja Toneff with the album Fairytales, a very popular jazz album around here

stone_of_tone said: "into my 5th year with my ZMA"

Already five years of the Mystery amp! If asked I would have said it was 7 or 8 months ago that we were reading the forum page introducing this new model.  It does not seem possible that much time has got away.  

Ordered all the custom parts for about 30 UFO25's this weekend! That should get the ball rolling.

Also completed the CNC work on the tube caddy this evening...



Just threw in some random tubes to check the fit. This case will be included with each amp.

I should be able to start contacting people on the list by no later than Memorial day!

Literally the only thing left is the photographs and to lock in the introductory price on the web site - both to be determined once I get the hardwood bases and the cost of those bases.

Steve

Wow, very cool case! This amp is really going to be something!

Any chance of dual outputs on the se84-25? Add-on option?

I am pleased to announce that the SE84UFO25 bases have been here for well over a week!  

I have chosen Peruvian Walnut for the Anniversary amps standard base. This is an exotic wood for an exotic amp. This wood is to standard walnut what the anniversary amp is to the standard zen amps. This weekend I'll try to get some photos.  

Here is what the wood and natural finish look like:



So now we're really close. To expedite things I have estimated the labor cost to build when I came up with the target price of $2800.00 so the final step is to have Dennis build serial 001 to be sold and make sure my estimate wasn't way off. I hope to have him start the build next week. This means we are still on track for contacting people on the list by May 30th.

Pretty exciting stuff! Listening to the amp just brings me joy!

Also Bob's starting the build on the DNA2 speakers to make sure we can replicate it. Normally that wouldn't be a real concern, as you build it the same way with the same tolerances and parts and it sounds the same. These particular speakers sound so good I'm going to have to hear at least 3 pair between me and Bob to believe it's actually happening - if you know what I mean.

So that's where we at, sailing down wind at about 5 knots in clear weather with land in sight!

Happy listening!

Steve


NOTE:  Shortly thereafter (Days) I changed the wood to African Padauk which you will see in later photos.

This "visualizing the distortion" thing is really cool. Unfortunately I find that in my system I like the bottle-shaped OB3 tube best. . . and there's less "visible" area on these and it's not as easy to tell distortion. But my experience with the OA3 has let me know where the power boundaries are with the HR-1s and I never need to go into distortion land to get the output that I need.

That said I've ordered a pair of short, straight OB3s and I think these will allow me to see flashing if it occurs, and I hope they sound as great as the Sylvania bottle-type I'm using.


I love the sound of the Monoblocks. With the ZTPRE and ZBIT and ZROCK2 I get the lower end heft and presence that the Torii Mk III brought to the system for the first time, and I get that organic "I've never been split" sound of the SET amps and that atmospheric detail and drama of the Anniversary mods. Man it's a great sounding pair of amps.

Well, just had a holy crap moment during the intro to After Midnight by Hanne Boel Outtakes album... honestly wasn't expecting that one!  These resistors are better than I knew.  You won't be hearing from me for the rest of the night as I'll be preoccupied.

-Steve

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I know you're busy with 25th Anniversary stuff, but I'm not listening to my ZMA since I've had my Pre-Prototype Zen in place since December. I can drop it off anytime if you want to tinker with it.

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That sounds seriously amazing! I may have to pick up some for my little Zen! Would it be worth it in the ZMA as well? Or are there too many components in the path, comparatively?

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LR, I was wondering the same thing when I read Steve's post last night.  Looks like there are a couple 1/2 Watt resistors coming off pins 2 ad 7 (Grid) of the input tubes and a couple 2 Watt resistors coming off pins 3 and 8 (Cathode).  I assume the two 1/2W resistors would be the ones to target.  

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Yes, the grid is the input.

Since the DirectStream DAC has it's own volume that doesn't drop bits, I'd be tempted to bypass the attenuator pot and try these resistors on the ZMA input tubes. Sounds like an expensive experiment...so I'll leave it to you, Jeff.    ;D

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I have the DS and the TEAC NT-503