[Deleeh]

Sonics would be important, and would certainly make a difference with Zmf headphones.
Which is probably in favour of the Kenzie.
I looked up VT-137, which is still reasonably priced.
12ax7 also and a little better represented.

Mogwai would also be appealing on a Art.

I assume the noise floor that was present in the counterpart is probably fixed on both after Rev 2? Or I'm not sure if they were represented at all.


I'll definitely put both on my wishlist.
Thank you very much for taking the time for me.

 

[ampsandsound]

Noise floor is non issue on either. Now I’d straping KT88 5ar4 12ax7 you’d have it the highest but perhaps but you’d also have 7-8watts. Not really ideal for orthos and high impedances. The Mog order versatility and tube rolling. It’s the Swiss Army knife.

 

[gacyde]

http://ampsandsound.com/

Mogwai

Like many of our products, the Mogwai evolved from our earlier designs, borrowing from the Bigger Ben and Classic Wonder, while embracing the form factor of the Kenzie. The Mogwai offers more than an entry point for tube amps, but a hybrid product, meant for serious headphone and speaker use.

Our circuit offers the ability to roll a wide variety of tubes inexpensively and bring increased power to headphones without any sacrifice of design choices that conflict with our values.

The Mogwai combines the features of a full sized amp into a small amplifier package, weighing ~15lbs largely due to its over spec’d custom wound transformers. The Mogwai utilizes Single ended Class A operation with zero feedback to provide the essence of our Classic Wonder sound; strictly old school SET sound, while paired with a more accessible tube selection.

The performance of the Mogwai is made possible with custom wound ultra-high quality output transformers from Transcendar Transformers providing amazing frequency extension and flat response.

The Mogwai does not use a voltage divider network, but depends on transformers instead. We chose 32ohm tap for headphones to offer a dedicated selection for the widest range of headphones, and an 8ohm speaker tap to connect the Mogwai to moderately efficient speakers.

The Mogwai displays its transformers prominently on the chassis to frame in the tube selections, which can vary from a 6L6GC to a KT88.

Volume control is handled by the ALPS volume pot to allow attenuation and simplify the signal path… no preamp is needed. Zero feedback on the outputs negates the need for a pre, an iPhone can drive the Mogwai without issue.
The Mogwai differs from the Kenzie as it aims to provide powerful output while remaining true to 50s tube ideals, and single ended sweetness. As with all ampsandsound products, we strive for a neutral, non-fatiguing sound, and demand that all our products be ultra-quiet in operation. Quiet operation is not just a goal but a guiding principle that shapes all design and implementation choices… from pots to resistors we strive for tube amps to never distract from the music.

Input tube: 6SL7 or equivalent
Output tubes: 6L6GC, EL34s, KT66, KT77, KT88, 6550s and KT90s
Personal favorite is the TungSol 6L6GC STR. Warm, strong and tight bass.
Cathode Bias/automatic bias allows for easy tube changes without adjustment.

Compatible with 32ohm-300ohm headphones using the “32ohm” 1/4″ jack. (Beyerdynamic T1-600ohm were used successfully but not ideal.)

Headphones driven successfully or tested with the amp include, Mr. Speaker Ethers, Mr. Speaker Ether Cs, Audeze LCD-2.2F, Audeze LCD-XC, AKG240, AKG701, Sony MDRV6, Sennheiser HD650, Sennheiser HD800, Beyerdynamic T1-32ohm, HIFIMAN HE400i.

The Mogwai is made with pride in Southern California with US sourced parts, including our precision transformers.

Specs:
Input impedance is 250Kohm with alps pot, .5v for full power.
Noise with pot fully counterclockwise is 500 micro volts RMS
Measured with 6550 output tubes on 1/4″ 32ohm optimzied headphone jack. 500mW RMS output 20 Hz (-2db) to 17.7 kHz (-3db)
Measured with 6550 output tubes on 8 ohm tap. 3W RMS output 30 Hz (-1db) to 20 kHz (-2db)

Please look at our news section for feedback from owners of the Mogwai.
Mogwai Headphone amp – $1,700 with tube set.

Kenzie Headphone Amp

Like many of our products, the Kenzie Headphone Amp evolved from our earlier designs – in this case, rave reviews about the SE-84’s headphone section. The inevitable question followed; why didn’t we build a dedicated headphone amp?

Why indeed? After some research, we came to the conclusion that the Kenzie amp using the much loved darling circuit was the right choice for us. The outstanding performance of the Kenzie Headphone amp is made possible with custom wound ultra-high quality output transformers providing amazing frequency extension. The Kenzie does not use a voltage network, and has more than enough power to drive even the most difficult headphones. We chose 32ohm and 600ohm to allow use with the widest variety of headphones.

The Kenzie Headphone amp showcases the transformers on the chassis to frame in the amazing 1626 tubes in all their single-ended direct-heated bliss. We have included an ALPS volume pot to allow attenuation and simplify the signal path… no preamp is needed.

The 1626 AKA Kenzie is one of the sweetest-sounding amps you will ever hear. The 1626 is commonly referred to as the poor man’s 300b; all the same great imaging, texture, and single-ended sweetness without the cost to break the bank.

The 1626 is a WWII era tube used as a transmitter tube in radar installations. The design is shy on pure output, but is overflowing with texture and drive, and is paired with a massive choke and robust output transformers for ultra-quiet operation. As with all of our products, parts selection was crucial during this build and each chosen not for price, but for best quality and synergy.

Input tube: 12SL7 or equivalent
Output tubes: 1626 or VT-137 which is a WWII transmitter tube and characterized as sounding like a mini 300b.
Cathode Bias/automatic bias allows for easy tube changes without adjustment.
Compatible with 32ohm-300ohm headphones using the 32ohm 1/4″ jack.
Headphones above 300ohms will benefit from using the 600ohm 1/4″ jack.
Headphones driven successfully or tested with the amp include, Mr. Speaker Ethers, Mr. Speaker Ether Cs, Audeze LCD-2.2F, Audeze LCD-XC, AKG240, AKG701, Sony MDRV6, Sennheiser HD650, Sennheiser HD800 (though reduced volume), Beyerdynamic T1-600ohm, HIFIMAN HE400i.

The Kenzie is made with pride in Southern California with US sourced parts, including our precision transformers.

Specs:
Input impedance is 250Kohm with alps pot, .5v for full power.
Noise with pot fully counterclockwise is 5mV RMS (Average)
All measured at 32 ohm tap. All power measurements in RMS
100mW 20 Hz (-1db) to 17.7 kHz (-3db)
150mW 20 Hz (-1db) to 14.8 kHz (-3db)
200mW 20 Hz (-1.25db) to 16.7 kHz (-3db)

Please look at our news section for feedback from owners of the Kenzie Headphone amp.
Kenzie Headphone amp – $1,500 with NOS tube set.

Gizmo

I picked up the Mogwai that was at CanJam SoCal. Really loving it! These amps deserve their own thread. I'd post a pic of it, but it's the one on the website and the pictures are way better than what I can take.

Since I bought the prototype, I'm claiming the right of prima nocta... or something... and nicknaming my Mogwai "Gizmo."

Reviews

Kenzie Headphone Amp

Positive Feedback
Headphone.Guru
mithrandir38
joespride

Note that development continues over at ampsandsound, and additional amplifiers have come to be since the post was originally made.

The following headphones amps are now being made by ampsandsound:

• Kenzie: Based on the Darling circuit. Now has a coupling cap upgrade option.
• Kenzie Encore: Bigger than the original, headphone jacks now up front. Now has 2 inputs and 1 preamp out. Also comes in a Deluxe version with input transformers and upgraded coupling caps.
• Mogwai: Headphone / speaker amplifier in one, old school SET sound. Coupling cap upgrade now available.
• Mogwai Special Edition: Not yet widely available. Includes a tube rectifier and moves the the headphone jacks up front.
• Agartha: Uses 300b tubes, SET sound. Cap and input transformer upgrades available.
• Leeloo: Uses 12AX7 for input and a pair of EL-84s for output.
• NOTE: You can talk to Justin Weber and order different output impedance on the headphone jack than what's listed.

good

 

[Deleeh]

Noise floor is non issue on either. Now I’d straping KT88 5ar4 12ax7 you’d have it the highest but perhaps but you’d also have 7-8watts. Not really ideal for orthos and high impedances. The Mog order versatility and tube rolling. It’s the Swiss Army knife.

Sounds good with the noise floor.
I'm glad they got it under control.

Are we talking about Mogwai or Kenzie as far as the Kt88 is concerned?

Mogwai would appeal to me even more, even if the tubes are a bit expensive.

But the Kenzie also makes a great impression.

I will try to say so.
I have a Feliks Euforia amp in use with the Zmf Auteur and upcoming Zmf Atrium on order.

If I were to buy a second amp, it would be great if it was also an upgrade to the Euforia amp.
I don't know if that's too much to ask, or if there's a limit to what tube amps can do.

At the weekend I listened to the Mcintosh mha 200 with the Auteur and the amp was not necessarily better for me than the Euforia.
There were also two things about the Mcintosh that weren't necessarily great for the price.

 

[gonintendo]

Does anyone experience a high pitched ringing sound when running KT88s?
I’m assuming it’s heater noise since I can hear it when I put my ear next to the tubes.

It seems to happen with most KT88s on my Mogwai SE. Lower power tubes are quieter but I like the KT88 sound.

Any tips for mitigating? I have some metal and rubber dampers on them which help but it doesn’t eliminate it.

To follow up on this, I was able to reduce this quite a bit by moving my UPS off of the circuit that mogwai is on to a different one (I didn't have the mogwai plugged into it obviously). I have those beefy underwood power conditioners that Justin recommends, and they definitely make a huge difference but they were no match for how much noise that UPS was dumping into my system. Moving it away also reduced the 60 cycle hum when you crank the volume by quite a bit too and everything just sounds way better. So lesson learned, power conditioners aren't a panacea for power issues.

 

[LegatoB]

Here are some photos purple lighting photos I took last night running Euforia as preamp to my Nautilus. Pretty interesting sound with the EL38 + 32 giving a different dimensionality to the power in Nautilus with the lighter EL34’s. Enjoyable, light, airy, resolving sound.

 

[audio integrity]

Hi all. Could someone who has heard both the Mogwai and the Forge comment on any substantive sound signature differences between the two amplifiers? Just for context, the use case for me will be 8ohm tap for LCD-XC and LCD 5. Thanks, in advance, for any color .

 

[theveterans]

Hi all. Could someone who has heard both the Mogwai and the Forge comment on any substantive sound signature differences between the two amplifiers? Just for context, the use case for me will be 8ohm tap for LCD-XC and LCD 5. Thanks, in advance, for any color .

From my rough memory forge on JJ KT88 tubes and stock 6SL7 on 300 ohm out sounds more "linear", i.e. less bloom and have a more prominent top and bottom end than the Mogwai SE OG with stock 6L6GC tubes. It should be pretty close between the two with the same input and power tubes, but expect more tube rolling with the Mogwai since you can roll rectifier tubes unlike the SS rectifier from the Forge

 

[TDinCali]

Here are some photos purple lighting photos I took last night running Euforia as preamp to my Nautilus. Pretty interesting sound with the EL38 + 32 giving a different dimensionality to the power in Nautilus with the lighter EL34’s. Enjoyable, light, airy, resolving sound.

huh, interesting…I’m going to have to try this setup.

 

[Deleeh]

Hello,
Quick question about the Kenzie og rev 2, can only 12AX7/5751 tubes be used or also others like 12au7?

There are 2 listed on Ebay right now but they are the older versions.
What is the relationship to the previous model and the current version?
(The price would be reasonable but I would have to check with Justin first if it is possible to have it converted to 230 because they are Us versions).

If I understand it correctly the first version is a bit more versatile in tube rolling with adapters,and with the 12SL7 a bit more susceptible to hum as well if the information is correct?
I assume the latter is no longer present with the Rev 2 as Justin has confirmed, the price for this is probably that it has slightly less rolling options.

Personally I find it a bit of a shame that you can't find much information about the Kenzie Og rev 2.
Even the rentals tested or personally purchased here on Headfi are all older versions.

 

[ampsandsound]

The Rev2 of all the amps offer many more tube rolling options. Its true you could have used adapters but there were improvements to the the PCBs between Rev1 and 2, it wasn't a pin change... additionally 12AX7 variants are much more common and variable than octals. You have many more options of differing Mu values. That said, both the Rev 1 of any of the amps and the current Rev 2s are wonderful amps...

 

[gonintendo]

Can 6L6/KT66 type tubes take a 5AR4 rectifier or just KT88+?

 

[ampsandsound]

Sure can

 

[TDinCali]

Anyone have a Bigger Ben and using highly sensitive hp’s without any crackling?

I don’t have a big tube collection so I’d like to try different combinations to get rid of the noise I’m hearing. It’s not a hum, but a crackling noise that’s there when music is playing or not. When I turn up the volume I eventually drown it out but on quiet passages I can still hear it. It taking away from my enjoyment and I’m hoping there’s some solution.

 

[nwavesailor]

If you don't have another pair of KT-88, do you have another rectifier and driver tube to try?
Is is in one or both channels?
I'd swap one tube at a time. it sounds like one may be bad. My BB had a little hum but NO crackling!