AmpsandSound Amplifiers and Speakers builder

I agree. It took a bit of legwork to sort out the different families.

I believe Leeloo and Pendant are the same family, and Suolo is part of the Kenzie family.

I believe the Nautilus is a fusion of the Mogwai and Kenzie families.

Hope you’re enjoying it along with the recently landed tubes.


The Nautilus is awesome. I was going to leave it at that, but here are some early impressions.

I haven’t A-B’d it against the Pendant yet, but it has a familiar fast, neutral sound, so it’s not a huge leap from the Pendant in terms of sound signature, although I suspect I will notice differences when I get around to comparing them.

Plenty of power. The Verite sounds nice and relaxed using the 100 ohm output, but I think I prefer 300 ohm, because the Verite suddenly becomes locked into the rhythm of the music, and the imaging is clearer. From memory (which is faulty), the ZMFs did not sound as controlled on the Pendant’s “High Z” output. The Stellia sounds awesome using the 32 ohm output.

Having gradually switched from stock to NOS tubes over a number of days, I can say that I could have stuck with the stock tubes and enjoyed using the amp, with the exception of the JJ 12ax7, which I found sucked all the warmth out of the music. I also found that the 12ax7 had too much gain for my Stellia, meaning that I had no practical range on the volume knob. Switching to a 12au7 gave me more flexibility with volume.

Switching from stock JJ KT88 and Tung Sol (new production) 5AR4 to Amperex GZ34/5AR4 and Tung Sol (NOS) 6550 gave me a little more texture, stage and holographic imaging. The texture of synths and strings is amazing. Bass is well controlled and very rhythmic. The stage is nice and wide, and when I listen to a piano concerto, I can follow the pianist’s hands from one end of the keyboard to the other. And I’ve noticed the height of the stage, not just the width, i.e. some sounds are above my head and some are below.

When using the stock power and rectifier tubes, I had preferred using the Mazda 12au7, which didn’t have the warmth of the Mullard, but had a more uniform sound, giving me good highs and lows. But with the NOS tubes, the Mazda has slightly too much emphasis on the upper mids and highs, so I’ll try one of my other 12au7’s to see if I can find better synergy. The curse of tube-rolling I suppose, where you find the perfect combination, you’re happy for one day, and then you change one tube, which causes the whole house of cards to fall down, and you have to start again.


No, you just go back to the tube combo you liked!! Stop once happy! Rolling away from a good set just reinforces that you have a good set.


You’re right, but I still have another rectifier to try out (I wanted to hear the difference between a 5AR4 and 5U4G, to help me understand what “sag” means) so I’ll stop rolling right after that.

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Thanks, it’s nice to get more detailed impressions of the Naut, including the interaction with certain tubes.

Your impressions generally line up with my expectations.

My preferred ohm output seems to be a function of the power of the tube roll used and whether I want a more/less aggressive/assertive presentation.

I would expect the 12AX7 to have too high of a noise floor with the high sens. Stellia.

I’ve found Justin’s amps to be especially adept at imaging and soundstage, on both headphones and speakers.

Is your Pendant High Z output 100 ohm or 300 ohm?


I couldn’t remember so I had to find Zach’s writeup here.

I have the latest version of the Pendant before the SE, so High Z would be 100 ohms. OK, that’s why the Verite sounds different on 300 on the Nautilus.

Both 100 and 300 are very good, it just depends on my mood. The 100 is more liquid, with smoother vocals, and the 300 is a little more aggressive-sounding, where I get the feeling that the Nautilus is telling me “you liked that, now see what I can do”, and everything locks into place, particularly drums.


I view High Z 100 on the Pendant to be favorable, if one had to choose.

With 300 out, the amp makes it clear to the driver and listener, in no uncertain terms, who is boss.

5AR4, 300 ohm out, Tool’s Pneuma. Now that’s a party.


Yes! I’m listening to Pneuma right now, 5AR4, 300ohm out. It’s just exhilarating, I’ve never heard anything like it. Drums crashing all around me, the guitar notes are so thick, I can feel them.

Not relaxing though, and perhaps that’s contributing to the emphasis in the upper mids and highs that I’m experiencing. I can imagine that I’ll settle down eventually and go back to using 100.

I’m curious to try out the 5U4G (probably tomorrow), and see how this all changes.


Are you generally happy with your tube pick ups?


Sweet! It’s such a killer track and showcase of Danny Carey’s talent. Perhaps also check out Neil Peart and Rush’s YYZ.

I couldn’t do 300 ohm as my usual go to, for my system. It’s nice to have the versatility, as with 5AR4 and 5U4G.


Yes, very happy. I don’t feel the need to search for any “holy grail” tubes. I might buy one or two more 12au7’s, which are fairly cheap, but only to get a feel for each manufacturer’s “house sound” (with the understanding that there can be a variation in sound between different tube models).

I’ve tried to buy high value tubes (e.g. I got the Mullard 12au7 made for Phillips, which was significantly cheaper than the Mullard-labeled tubes) and I feel that this was a good way to educate myself about tubes.


Anyone has Bigger Ben, and what do you think of it? Talked to Justin a couple of days back, the impression I got was that Mogwai SE + Jupiter Caps upgrade goes a long way, I am wondering if the Bigger Ben would help any further if I am hearing on ZMF Verite Open for the time being. Just wondering what more power from the Bigger Ben would do to the sound on the Verite.

I have a Mogwai SE + Jupiter caps upgrade. I opted to not get the Bigger Ben.

The Bigger Ben likely wouldn’t be worse – more there-there, that could be revealed by the VO. The Bigger Ben has larger output transformers and other enhancements related to power supply and choke filtering. I don’t believe the power output between the two is a significant difference.

Another feature of the Bigger Ben is the 2 additional headphone taps that allow you to dial in your sound across the range of output impedance.


The website pics of the BB show only 1 input, while the Mogwai SE has 2 inputs. I’m not sure if those BB pics are current.


When I talked to Justin about this, he basically implied that the upgraded SE with Jupiter caps was the biggest bang for your buck in the headphone line.
He described the Bigger Ben as being “within spitting distance” of the Natilus.


That’s helpful, and is consistent with my evaluation and ultimate selection of the Mogwai SE with upgraded Jupiter caps.

The Bigger Ben and Nautilus are no doubt outstanding.


Tube rolling update on the Nautilus, with a question to @bpcarb and other tube experts at the end of the post, regarding my results.

This is what I was using yesterday, which gave me a touch too much emphasis in the upper mids and treble:
Power tube: Tung Sol 6550 (grey plate with 3 holes)
Input: Mazda 12au7
Rectifier: Amperex GZ34/5AR4

Switching the 12au7 to an RCA clear top removed the emphasis on the highs, and the sound is quite nice, much smoother. It’s almost too smooth compared to the Mazda, but I’ll give it more time to burn in (only 5 hours of listening for the RCA).

I’d originally planned on keeping each tube combination stable for a few days before changing anything, but I only had 1 more tube to try, and impatience won the day, so this morning, I switched my rectifier to an RCA 5U4G.

I hated the results.

The tone was fine, but the sense of rhythm and timing was “off” to me. It’s hard to describe, but everything sounded a microsecond “behind the beat”, making the music sound slower, and I couldn’t tap my foot at all. I put the 5AR4 back in and the rhythm and timing returned.

I was wondering if this change in timing is a characteristic of the 5U4G vs a 5AR4 (am I describing sag?), or if it’s down to the combination of the 6550 power tube and the 5U4G not working well together for my taste, and perhaps a different power tube (like a KT88) would have better synergy with the 5U4G.

Note that the RCA 5U4G only lasted 20 minutes before being pulled. Perhaps it needs more time to burn in? I’ve noticed changes in tone after lengthy burn in, and wasn’t expecting the timing to change, which is why I took it out so quickly.


I consider this progress toward dialing in your system and preferences. Embrace it, I kid.

What you describe demonstrates the difference in sag. At its worst, too much sag can be sluggish and bloated. At its best, it can be euphonic and beguiling.

You might want to swap in a higher gain input tube such as 12AT7 (if this raises the noise floor, try swapping in a lower power power tube such as 6L6GC) and see how it plays with the 5U4G.

I doubt that there would be a difference between 6550 and KT88 as they have the same power output, but this isn’t 100%.

Burn in might help the 5U4G, but unlikely to move the needle for you.

It is quite possible that 5AR4, along with the accompanying tubes, is your jam. Zach likes 5AR4/GZ34 on the Mogwai SE with ZMFs, and I might prefer it most of the time also.

I’d venture to say that an RCA or Amperex input tube is your sweet spot, in between Telefunken/Mazda and Mullard. These are my best projections only.


Thanks @bpcarb, that was extremely helpful!

I can return the 5U4G to Vintage tubes, so I think I’ll do that, in order to limit the variables, which will helps me to continue dialing in my system and preferences, as you put it. My goal is reach stability in my audio chain asap so that I can listen to the music again and not the gear.


Generally, in my comparison with 5ar4 to 5u4g I found similar. 5u4g was softer, more congested, more trailing edge. It is entirely possible that synergy with other tubes is effecting things; however, I wouldnt be too interested in trying to make a tube work for you unless there was something about it you really wanted to keep, such as benefit in tonality or dynamics.

Having said that my best rectifier is of the 5u4g type, and it surpasses my other rectifiers both 5ar4 and 5u4g, buts its rare and expensive and not something I would recommend chasing unless you want to risk a potential loss on a tube.

I doubt you’d get a big enough improvement to justify being pissed off about your sound for the time it would take to try and burn it in, Unless you burn it in when you are not there, but, thats still not something I think will make a huge difference. If a tube really sounded off initially I pulled it. I doubt burn in would improve anything enough to make a bad tube good, might make a good tube great or a very good one in to something you never take out of your amp, but burn in likely wont rescue a tube.