AmpsandSound Amplifiers and Speakers builder

Welcome @ampsandsound. There are many fans of your gear who frequent the forum.


Hi @ampsandsound how you are having a good weekend.

Can you easily explain how you make so many different impedance outputs on your amps? My Ovation has FIVE! I am digging the 32 ohm out with my 300 ohm Eikons, and I do not really understand the whole impedance matching thing and it seems there is some flexibility with it.

If it doesn’t require a dissertation I think some other of us non-builders would be curious…

Have a good weekend!


I actually found I really like the 32ohm tap as well from my Mogwai OG as well as the Nautilus with the Verite Open and the Aeolus. So you are in good company buddy!


Hey guys, sorry for the late reply… I spent yesterday at the zoo with the family.

As a general rule, I think most/many headphones sound really great on the 32ohm tap as consider it a bit of a universal.

The idea behind multiple tapps is to engage the output transformer as directly as possible… no voltage divider networks or other means of adjusting impedances. In general the closest impendence is likely to provide the most efficient energy transfer.

Adjustment of impedance gives the user the ability to find a sound that best suites their gear and ears. Lower impendences generally will yield lower noise floors. Lower impedances should provider greater dampening factor/better control of the woofer.
However, higher impedances can sound more lively and sometimes give more bass output but not as taught.
The relationship between drive, noise floor and liveliness/air is influenced but impedance tapp and the relative voice coil… use your ears to gage your own preferences.

Hope this helps… I always think I give more complete answers when speaking :-).


Let your ears be the guide seems like a reasonable assertion beyond your general assertions about low z to high z tendencies. For what it’s worth, I enjoy my Autuers off the 100 ohm output and HE560 off the 16. I’m still in the honeymoon phase with my Kenzie Ovation so expect more detailed impressions after a few weeks.


Thanks a lot Justin, the info is much appreciated.

I have had my Kenzie Ovation for a few weeks now. I’m fairly new to serious tube amps, so YMMV. I’m also greying about the muzzle and my hearing isn’t what it used to be. These caveats aside, I am incredibly impressed with this amp.

I generally run my ZMF Auteur on either 100 or 32 ohm outputs. I like the sound of my HE560 off the 16 ohm output.

I have the volume between noon and 3 o’clock on the knob even with a -3 db volume drop in Audirvana. I set the -3 db drop in software to give me more headroom in the rest of my chain. I am super sensitive to brick-wall filtering and that awful digital glare that occurs when the signal gets overloaded.

As far as tubes are concerned, I have three different sets of 1626 power tubes. I can’t hear much difference, but it may very well be there and I don’t know what to listen for yet.

I will continue to experiment with pre-amp tubes including 12SG7, 12SN7, 420a (with an adapter), 2C52, and 9-pin 12 series (with an adapter). While I find that pre-amp tubes make more impact on the sound, I can’t say I have a strong preference yet. I would liken the preamp tube choice to bitters in a well made cocktail: the pre tube seems to emphasize some aspects of the music, but the result is never less than pleasant.

I will share more impressions as I continue to listen to just one more song.


I’m coming up on 2 months of enjoying the music with the Mogwai SE. Below is a summary of my tube selections and recommended approach for the Mogwai SE with high sensitivity headphones and speakers (which may potentially be applied to other amps).

For my chain and desired sonics, my tube preferences lean toward more detailed, incisive, airy as opposed to warm and punchy.

UPDATE: See subsequent post below.

My current preferred tube combination for Qutest 2V > Mogwai SE 32 ohm out > VC with Auteur/Be2 pads (all NOS except JJ):

12AU7 Amperex Bugle Boy Holland (or Telefunken/Mazda)
5U4G Tung Sol blackplate ST shape
KT88 JJ Slovak Republic made blue glass

For less sag:

Same input tube
5AR4 Sylvania fat boy

The above essentially reflects either a high power rectifier coupled with low power power tubes or low power rectifier coupled with high power power tubes. In my listening, going high-high resulted in too much energy and going low-low was too relaxed. In all instances, a low gain input tube was preferred. Eventually I might see if low-low matches with a higher DAC output voltage, and vice versa.

For those wanting a warmer/punchier tilt, they may like RCA (especially 6550 and 5691 redbase), Mullard, Gold Lion, Matsushita. Bendix (with adapter) and Tung Sol were also highly regarded in my research.

For new production, Tung Sol and JJ have been good, especially TS 6550.

If someone can please report back on Tung Sol 6550 grey plates no holes, early 1960s, they are supposed to be the next tier up for power tubes.

For high sensitivity headphones, I would start with a low gain input tube. Next, figure out whether you like more or less sag, or whether your chain responds better to a higher or lower power rectifier tube. The power tubes then fill in to best complement the selected input and rectifier tubes. Depending on any audible noise/hum and sonic preference, adjust accordingly for more power/gain. Once nailing down the tube type, you can proceed to selecting the tube manufacturer (not necessarily the tube brand). Other approaches may work; this worked and was manageable for me.

12A_7 tubes require the use of a tube adapter with the Mogwai SE. I got better results with these tubes over NOS 6SL7/6SN7.

Switching to high sensitivity speakers, using the highest power and highest gain tubes was preferred.

Below is a cheat sheet for the gain ranges for 9-pin 12A_7 input tube variants (not comprehensive, someone check my math):

100: 12AX7
70: 5751
60: 12AT7, 6201, ECC81
47: 7062, 6211, 5965, 18ECC, E180CC
20: 12AU7

My sweet spot for performance and value for non-directly heated tubes is generally $60 to $100 per tube. Before I commit to spending more on a tube, I’d need to confirm that an elevation in tubes would result in the highest ROI compared to other enhancements to my chain.

@PaisleyUnderground I’m posting here as the content is specifically related to the Mogwai SE and other A&S amps. We can link in the other thread.


Hi @Cryptowolf Thanks for sharing and glad to hear you are happy with the Ovation. Me too!

My tube feedback will be simplistic, I have a box of about 30:

1626: RCA & Sylvania
2C52: Raytheon
12SL7GT: Sylvania, GE, Dumont, National Union
12SN7GT: Sylvania, Dumont, Raytheon
12B4A: RCA, GE, Philips ECG
ECC801S: 1 tube labelled Telefunken, but also 6201 USA, not sure it is authentic but sounds great

12AX7 to 12SL7
12B4A to 1626

I have not bothered to try different brands of 1626, I just change them when they go bad or start making noise. In the 3 months I have owned the Ovation I have discarded 2 1626 tubes for making noise.

I tried the 12B4A tubes adapted but I preferred the 1626. In my case, the 12B4A had a higher noise floor.

For efficient headphone use, I prefer the 12SN7 for its lowest noise floor, but for 2 channel it lowers the gain too much (for my speakers). The 2C52 adds the most gain, more noise, and sounds very “solid state” to me. Less holographic I think, but I only have one. It is a powerful tube for 2 channel listening.

For 12SL7 I “think” I prefer Dumont. But the odd National Union I have, which looks really simple in construction, is the quietest one! But the bass also is a little bit looser.

The ECC801S adapted is probably my favorite tube, even though I am unsure of its true pedigree. It is screened both as a 801S AND a 6201 USA, Strange. I don’t care, it sounds like live music with similar noise floor to a 12SL7. It is of course by a big margin the most expensive tube, but I did my best to be objective even knowing its price. It does remove a little of the amps inherent neutrality, but in a really good way.

In general, with the Ovation, the tube differences are subtle outside of noise floor and gain. The amp itself is so clean and transparent, I found more important differences using different output impedances than rolling tubes.

I prefer my Eikon out of the 32 ohm, I find it too efficient for the 300 ohm, I hear the noise between tracks. I like my 6XX out of the 100 ohm. I was also amazed I could listen to my MEST out of the Low Z! It is the best they have sounded.

I am too new at this to give informed advice. But my limited experience would indicate that with this amp, having A LOT of inexpensive stock tubes will serve well so you have good supply to replace them as they get noisy. These things are old, and in my experience variable. Get a bunch while they are still cheap before more ampsandsound owners start driving up the price. For example, I got two 2C52 for $40 bucks, when I decided I wanted to lay more down for my 2 channel listening, the same seller wanted $60 for two!

Enjoy your Ovation.


Hi Mark,

Great input, it sounds like you’ve unlocked and unleashed the Ovation for both headphone and speaker listening!

This is a key point and I agree.

This makes sense to me based on my comparison of my 6XX and VC.

Please don’t discount your input. It’s been helpful and insightful (fried egg included), and there is value to getting diverse viewpoints including based on where a person is in their audio journey.

This is one factor I took into account when choosing the Mogwai SE rather than a directly heated triode based amp.



Thanks a lot for saying so


Thanks for the detailed response Mark. I haven’t tried the 2C52 yet, but I have tried a variety of 12SL7 and one 12SN7. The 12SN7 is a 12SN76TA from GE Honeywell (1966). Like you, I have found only a subtle difference, though the 12SN sounds phenomenal on all my headphones. The notes seem to emerge from a black background and then fade away into the same darkness. I remain impressed by the sound retrieval and ability to hear new things on familiar tracks.

I should have an adapter and ability to roll 12# tubes soon enough. Enjoy the music.


Per subsequent listening, I prefer the lower sag and tighter control and responsiveness of 5AR4 rectification.

My current preferred configuration: Qutest 1V > Mogwai SE 8 ohm out > VC with Auteur/Be2 pads with the tubes below.

12AU7 Amperex Bugle Boy Holland (or Telefunken/Mazda)
5AR4 Sylvania fat boy

The higher power output of the 5AR4 is offset/balanced by a lower output voltage on the DAC, lower gain input tube, lower power power tubes, and lower 8 ohm impedance out. 32 ohm out may be preferred by those looking for a more energetic presentation.


interesting you are liking the 8 ohm out with Auteur…I will try that with my Eikon, I have never even tried below 32 ohm.


Prior to this, I had not preferred the 8 ohm out. This is very tube and DAC output voltage dependent, where the headphone tap selected is the last line of defense that determines what amplification reaches the headphones.

*With the VC.


yes, VC with Auteur, I mis-read but I should know they are VC!


All good, and yes you do indeed know this :wink:


I was browsing through the A&S website. The Kenzie Encore, Leeloo Monos, and Suolo Monos are no longer listed. I view a consolidation and narrowing of the lineup as favorable, including to make room for future releases.


I agree! 20 Characters


I think the consolidation helps a lot, because I always found the A&S headphone amp page very confusing. However, I also think Justin could make the page even clearer, especially if there are new releases in the future.

When I was originally shopping for A&S amps, I would have liked to see the amps grouped by family (e.g. Kenzie, Mogwai), along with a description of the sound signature of that family.

At the time, I found it hard to understand whether the Leeloo Monos, Suolo Monos or the Nautilus were part of the Kenzie or Mogwai families or something else. I was confused enough about the line-up that I decided to set up a call with Justin, after I returned from vacation, to help me understand which amp I should buy first to complement the Pendant, with the long term target being the Nautilus. Of course that plan went to hell (in a good way) because I decided to cut through all my confusion and bought the Nautilus.