Using a fast-blow fuse in place of a slow-blow will very frequently (perhaps always in some cases) cause power-on fuse failures, especially with transformer-based PSUs. The in-rush current at power-on is much higher than the steady-state. That’s why we have slow-blow fuses.
You should still talk to Justin to make sure there are not other issues, but using a fast-blow fuse to replace a slow-blow is just an open invitation to frequent power-on failures.
A week after my Mogwai OG arrived and after 70 hours of listening it starts to bring out its qualities.
I stopped rolling tubes and in order to learn something about tube amps I mounted the original JJ tubes the Mogwai OG came with.
70 hours are nuts but tubes now are very silent and pleasing in sound.
I know there are better ones.
But I know I have to learn too.
No background noise, clean, open sound with nice dynamics and holographic soundstage.
A pleasure to listen to it.
Innuos Zen Mini MK3 with LPSU, Mogwai OG on steroids (Auri Caps) Sennheiser HD 600 on 100 ohm tap.
Stunning listening experience @ampsandsound
Just sharing some quick EL34 rolling impressions on the Mogwai (SE):
Was trying to find a good roll for the Utopia on the Mogwai, ended up with this. Pretty close to black noise wise and for me a great compliment to the sound of the headphone. Adding a slight bit of meat and soundstage while compromising as little as possible in terms of detail and speed. Ended up with this:
Tube roll:
Sylvania 6sn7w metal base
Ei EL34 Siemens labeled, saucer getter, black base
Sylvania 5931 double mica version
Input transformer = Off
Jack = 8 ohm
Psvane - EL34PH
I am usually not a big fan of the “extra fancy” reissue stuff, and this tube is no exception in the Mog. The construction, while true to the form of a Mullard innards, it has that cheap replica look on the metal base. In terms of sound, it reallty doesn’t add much from a regular Psvane EL34, if anything it is slightly more coloured and mushy. Still it sound like any chinese generic tube to me, not bad, but slightly dull, flat and unexceptional. Has more colour in terms of warmth than the russian reissues, which some may prefer. I’d just get a real Mullard (these are almost the same price) or save som cash on regular reissues personally.
Mullard EL34 - Xf3s, Blackburn, Philips labeled, single getter
Quite common, middle of the road Mullard, still a solid tube. They have a really good balance of that EL34 body and kindness to them, but are still very detailed and exciting to listen to. In the other amps i’ve had, these would usually be my go-to, but they just don’t click in the same way with the Mog. These are not as warm as the replicas, but still a touch too warm and slow in the Mogwai for my taste. Works out for headphones like HD800 though.
Ei EL34 - Siemens labeled, black base
A very cool looking and characteristic tube in terms of having the top on the bottle. I have rolled these in other amps vs. the Winged Cs, and to me they have been quite similar in those cases. I don’t have any Winged Cs on hand atm for comparison in the Mog. However, they are a less “romatic” kind of tube than the acclaimed Mullards. They still have that distinct EL34 body to them, and good staging capabilities. Seems like a good balance and fit with the Mog in general for me.
Summary:
Found the EL34 tube with the least warm leaning signature to it to be most desireable for this roll. Complimentary input and rectifiers similarly, but also for noise control.
Notice:
No input transformer chosen for a slightly more open presentation, which I think compliments the headphones at hand. 8ohm tap probably a no brainer in this case.
Informative impressions. I’ve been curious about this pairing.
This is interesting. I can also turn off the input transformer with my Mogwai SE by using Input 2.
Does noise increase from 32 and 300 ohm outs?
This is interesting. I can also turn off the input transformer with my Mogwai SE by using Input 2
Yes, seems to be a bit of a variance of opinions on this case. My take is that it makes the sound a bit less compact, for the lack of a better word. Also moves the breakup point way down, so the amps potential to drive heavy loads are substantially reduced…which is no problem with stuff like these kinds of dynamics tbh.
Does noise increase from 32 and 300 ohm outs?
Yes, too much for me personally. But also the bass on the utops don’t play well on higher impedance for my taste. I tried making Clears work at some point, but i found them even bloating up a bit on 8. Utops do just fine, very happy about it acctually. They both have very agressive impedance humps in the bass region… and the drivers don’t seem to play well on low DF, rule of 8 seems to be legit on focals with A&S, at least for my taste. Got a little inspired by @Resolve 's video with the utops+forge tbh.
Yeah I’d only use the 8 ohm out with the Utopia.
We did selectable inputs for mogwai SE, but then it became the default to have it on both inputs as people were always wanting it.
Its utility, no input Tx/ input tx has been reduced.
We are likely moving to just single input tx but have been working on a 2:1 step down tx.
So it would allow 1:1 input tx for most situations and 2:1 reducing/attenuating really hot front ends… still a work in progress as we haven’t received the prototype/preproduction of the new input transformers.
Variance of perceptions, indeed. The sonic difference is subtle for me. With input transformer, I sometimes pick up on enhanced microdetail and decay. Without input transformer sometimes solves ground loop issues.
I haven’t encountered this where I have high sensitivity dynamics, planars, and speakers. I’ll keep in mind.
With the Rosson RAD-0, while the 8 ohm out sounds correct, I’ve found the 32 ohm out to introduce some bass bloom, which is sometimes desirable.
I’m not going to write review about my @ampsandsound Mogwai OG custom. I haven’t got the competence and my words can only be reductive in comparison to the job Justin did.
I have the headphone amp since 5 months and I believe I can put down in words some impressions.
I know there are many very competent persons in the forum and I’m everything but competent about tubes so please take my consideration with a grain of salt an accept my apologies for wrong things I’ll write for sure.
This amp has totally changed the way I work with music and the way I enjoy music.
I love the way tubes colour my music without messing with the sounds I love.
First of all comes the soundstage. In comparison to solid state the sense of stage that tubes give is incredible. When listening to vinyl especially, using a MC cartridge with proper pre amplification and 6L6GC STR tubes the sound is lively, spacious, rich and I love it.
Basses are dense and authoritative without being excessive or inaccurate.
Mids are rich, they have the centre of the scene and it is something I really appreciate.
Treble is well controlled and never fatiguing or unpleasant.
When I have to listen to music I need to review I’ve found the best (for me, for my tastes and needs) is using a pair of EL34L: a little less power but so many more shades and finesse in the sound.
It is something Justin talked about in the interview by @Resolve and something really help me to learn to use my amp to it’s full potential: stop seeking raw power and explore the finesse, the subtle changes you can obtain with certain tubes.
The Mogwai has been my first tube amp and it’s been the start of a whole new journey.
I’m rediscovering the music I love and I always find new little shades that I wasn’t aware the music had.
I’ve used the Mogawi with all my headphones: Sundara, HD600, HD660s, Dan Clark Noire and Grado GS1000. None of them sounded inappropriate with it and even the Grado found a space again in my listenings.
I’m very grateful to Justin and to all the members of the community that helped me in so many ways to find my tube path.
Thank you for reading and for your patience for my lack of skill about tubes.
Enjoy the weekend.
Very good points, I just wanted to mention that the interview was actually done by @Grover - so big thanks to him on that.
My bad Andrew, my apologies to you and Grover. Great interview, very inspiring about tube rolling and quality listening.
A pleasure for the eyes and for the ears. EL84B-STR are a very pleasing match with the Mogwai OG: very clean sound floor, nice, full bodied sound at the same time clear and precise.
I’m listening to AMM’s “AMMMUSIC” on vinyl and I’m really appreciating the finesse of these tubes.
Hello everyone!
Very much enjoying my mogwai se here.
Reading around about tube rolling the input tube 6sl7 to a 6sn7.
I know the 6sn7 lowers the gain compared to the 6sl7 but someone informed me the 6sn7 lowers the gain but has higher current.
Would I then be right in saying that the 6sn7 is be better suited for most planars?
The theory behind your assumption sounds correct to me and will give it a try.
For a more proper answer drop an email to Justin: he will give you a technical better answer for sure.
P.S. For tech data I’ve checked JJ website and found the following. I add it for your info and for others that may be interested in the topic.
This can become my final setup on the Mogwai for quite long time: Ruby EL34L STR and Tung-Sol 6SL7 GT.
Great dynamics, very subtle nuances and good control of the colours.
I paid something like €10 from my faithful store in Germany for the Rubys.
Sometimes the best (for my tastes) comes with the smaller expense.
This morning I’ve bought a very old RCA Black base 6SN7 GTB at a flea market near me for €5. I’ve spent 2 hours patiently cleaning it and restoring the pins. Put it on my Mogwai OG and my Noire are singing, punching very hard playing some Mika Vainio records.
Since they’re half the power in comparison to 6SL7 you have to set the volume accordingly but man! It’s incredible how good it works having double the current in comparison to 6SL7.
Thank you so much for the inspiration and thoughts.
PS. Next one that tells me DCA headphones don’t slam I’ll put a 6SN7… in his mouth 
I have been using the stock tubes my Mogwai Se came with:
Tung-sol 6l6gc str + JJ 6sl7+ Electro-Harmonix 5u4gb tubes for my radiance and hd600
And replace them with Golden lion KT88 + JJ 6sn7 + Tung sol 5AR4 Tubes when using Arya and LCD-XC (2021)
It definitely adds slam and body to all planars I have tried using that combo.
Arya definitely benefits from this.
Glad to hear I’m not the only one enjoying 6sn7 with planars.
Would be nice to hear other peoples experience with this and what preference they have for certain tubes on certain headphones and why?
Personally think this should be one of the top topics of this group. 
You would likely come across some relevant info in this topic.
Everything slams off the Mogwai OG!!! 
