Small Footprint SS Power Amps

Look at my StereoTimes website review on the SPL S800 single chassis amplifier. It fits the size you are looking for. It's made in Germany, very reasonably priced, and I made it a 2020 Product of the year because of its beautiful performance. I bought the review piece because I enjoy it so much. In my opinion, it's in another much higher league then the amps you mention in your post.

Teajay

Various Bel Canto models. 

Many small-shop monoblocks using PuriFi or NCore modules would fit your description. Some well-known vendors are Nord in the UK, Apollon in Slovenia, and VTV in the US.
These are class D but I would not rule them out for that reason. I replaced a more expensive AB amp with PuriFi monoblocks and haven't looked back.

Go  by sound not size.

Maybe the AGD GaN amps. There is a thread on them.

BTW - I have 2 AHB2’s hidden in my sons IKEA toy shelf which are 12 inches wide. A perfect fit.

Schiit Vidar

My new (to me)  Herron M1 monoblocks are pretty awesome. Small footprint, 150 WPC, but you need two. 

Class does not matter nearly do much as the size of the power supply. Look for seperates if you need a small footprint.
I' m getting 50 + 50 + 100 in 1.5" x 4" x 7" with a much larger remote power supply.

If you can afford and have the room
THOSE VINCENT monoblocs are simply wicked great. 
Vincent T-700 monos. Amazing German amps!
if I had the coin, I would be all over them!

 Dropping 800 on the avantone cl-200 in another week for a backup amp.

 Will be watching  my saved stash for enough for those Vincent monos.

Monarchy Audio.

i think that lil mighty mite parasound zamp can be strapped mono - gets about 100 wpc iirc

“14" or less wide.”

The dimension limitations regarding depth and height would be of use in providing you, The Original Poster, accurate recommendations. 

Adcom GFA-1A, Belles II, Carver The Cube, Quad 303 and 405, SWTP 207. All narrower designs. I have them in my amp collection.

AGD Audion GaN monoblocks. 

Quad 405 or 405-2.  100 watt per channel current dumping power amp.  13-3/8" wide by 7-3/4" deep by 4-1/4" high.  The heat sink is in the front so side ventilation is not an issue.  With a Dada Electronics revision kit and Dada's DC protection/delay modules, you'll have a very fine SS amp. with the power and size requirements you are after.

+1 hypoman! The Quad 405 -1 and 2 are great and innovative SS amp designs worthy of inclusion in any hi-end system! Too bad that today they are largely forgotten due to the hype for the latest greatest amp! Mine has been nicely upgraded by the previous owner. 

Here ya go! It’s not A/B!
https://ciaudio.com/product/c%e2%80%a2100s-2-channel-stereo-amplifier

I am guessing OP wants a Narrow STEREO Amp. i.e. space is the issue, so two monoblocks will exceed 14" max width.

Small: I have, am sitting here listening to, a Carver CUBE 

https://www.hifinews.com/content/carver-m-400-cube

mine is the M-400t (t version i.e. tube sound)

This one is overpriced, but nice photos and info

https://reverb.com/item/39295847-fully-restored-carver-m-400t-the-cube-stereo-mono-power-amp-over-20...
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OP mentioned class A/B

evidently it is class A/B up to 20 wpc, which (if you watch any McIntosh meter, or the Cube's db meter while playing), is almost everything. It has non A/B tricks to deliver more power when needed.

excerpt from the hifi news review linked above

"The innermost pair operate from ±25V rails and constitute a 20W Class A/B linear output stage, and stacked on either side of this pair is another pair of output transistors, commutated or switched by catching diodes and some driver circuitry. These are linked to ±50V supply rails and accommodate the swing of signal peaks between ±25 and ±50V. A third pair, the outermost, are fed from ±80V lines, these using additional driver and bias circuitry for clean operation.

For power levels below 20W, the additional transistors and rails are never invoked, and no difference in operation from a conventional amplifier should be apparent".

.................................

Frankly I never knew mine, t version, is supposed to sound like tubes. I bought it on Harvey's used shelf as a curiosity.

Used it for it's small size, in a bookcase with small bookcase speakers like now. 

I did use it's 200 wpc with my JSE Infinite Slope Model 2's, compared it to McIntosh MC2250 SS, 250 wpc. It is astounding how that little .... can compete.

I agree with smrex13. The Schiit Vidar meets all your needs. 
                                     
https://www.schiit.com/products/vidar

small and very good sounding, and a bargain at $875
https://www.audiogon.com/listings/lisaa033-audio-alchemy-dpa-1-stereo-amplifier-solid-state

AGD Audion. https://positive-feedback.com/reviews/hardware-reviews/agd-productions-audion-amplifier/

Hello,
Marantz made these home theater mono blocks. The store I buy gear from has a bunch of them. They are $190 each and they are 125 wpc. They have that good Marantz sound. They are about 3”-4” wide and about 14” deep. They will ship stuff to you. https://holmaudio.com/

https://holmaudio.com/product/marantzma500-mono-amps/
I hope this helps. 

https://www.audiocircle.com/index.php?topic=148963.0

hahaha

they sound just alright, but man do they stack nice!

Check out PS Audio has a cute little guy called the Sprout. I used one for about a week and and was happily surprised at how good it sounded.

All the best.

JD

Thank you all for the suggestions, having fun researching the options! Will let you where I end up.

Jeff Rowland has made a few over the years. The Model 125 is 13.7" wide.

The two options that I ended up pursuing were the SPL s800 (thanks for the suggestion @amorstereo) and a modded Quad 909. I can't find a 909 right now but may well try this for fun when I do find one. The SPL is ordered. Really appreciate all the suggestions.

I believe you are in for a real "sonic treat" when you get your S800. Please let us know what you hear when you get it. SPL is one of those companies that are relatively unknown here in the states, but highly acclaimed in Europe and Asia. 

Teajay (Terry London) aka amorstereo

@arcticdeath,

“if you can afford and have the room
THOSE VINCENT monoblocs are simply wicked great.
Vincent T-700 monos. Amazing German amps!
if I had the coin, I would be all over them!”

Check out Shengya PM150. Interior looks the same. Exterior is barely different. I believe it to be the same amp and is a quarter of the price. Just like Cayin and Spark audio are the same. 

Not sure if you have ever looked into the Audiolab 8300M Mono Blocks.
Really great sounding with some power behind them(250wpc Class A/B). I have tried these on several different speakers in the shop and seem to match up well with everything I throw at them.

@amorstereo Teajay - the SPL has been in play since Friday and it is everything you said it would be here and in your review. My recent addition of the LTA MZ3 as a preamp really upped the transparency and detail in my system and the SPL has added noticeable flesh to the sound (without sacrificing any of the detail) vs the SST Son of Ampzilla it replaced. I have not heard this much beautiful bass response from my Harbeth Super HL5+ speakers previously. The fact that it also fits into my smallish shelving is icing on the cake. Lovely piece of gear.

AVM MA 30.3s are half width monos.  Haven't heard them yet but (brand new models) but they look really interesting.  

amorstereo Teenay - your recommendation is spot on regarding the SPL Audio Performer S800. I’m so glad that I purchased it. It’s a remarkable amp that delivers the dynamic swings effortlessly & beautifully. I can’t imagine anything above it…class A/B ‘smallish’ amp befitting for a desktop application if desired…& its 185 watts @ 8 ohms alleviates any real need to upgrade.

The AVA DVA M225's are great small power amps to consider. I changed to those after the S800 and could not sell the S800 any faster. The M225's sound great, have 20w in class A bias, cool to the touch, and sounds incredibly natural. I'm not sure what to complain about at their price point.

1/2 size footprint and high-end ? …..CYRUS…l

 

https://www.cyrusaudio.com/category/products/power-amplifiers/

 

I'm thinking of the Atoll MA100. But it's only 60W in stereo and 150W in mono. 

So 2x Atoll MA100 ? 

AGD Tempo di Gan gets you there.

If you can accommodate really small monoblocks, I endorse Van Alstine M225's.

reality is, with class d tech of various types, small footprint amps with substantial capability are plentiful these days

there are also excellent class ab ones as well, from well respected companies like exposure uk, van alstine, and so on, built on half-wide chassis

Goldnote PA 10s when in mono blocks are 300 watts at 8 ohms and 600 at 4 ohms and very small foot print mates with their DS10 pre/dac/streamer also I small foot print  I am using this set up on my Audiovector r6 arrete plus I have  Auris Fortissimo integrated tube 

reality is, with class d tech of various types, small footprint amps with substantial capability are plentiful these days

Yes- ours is only 11" wide. We thought of making a version that hung off of the speaker terminals to create a 'powered' speaker...