Mark Rehorst's Tech Topics: A12 Classic

The A12 front panel. Yes, those are tubes in there!

I only recently started buying new gear for my stereo system as opposed to my habit of buying (and sometimes fixing) used gear. In July I bought an SVS 3000 Micro subwoofer to go with a pair of Canton Ergo 22DC bookshelf speakers my brother gave me. And more recently, I splurged on an $80 SMSL SU-1 DAC and an Advance Paris A12 Classic integrated amplifier.

I got the SU-1 DAC to connect my TV PC to the stereo system before I decided to buy the A12 amp. More on that DAC, here.

I've been using an LG sound bar with the TV, but have grown unsatisfied with its performance, especially with regard to dialog that I frequently can't understand. The sound quality from the stereo system is so much better than the sound bar, that it almost hurts to use the sound bar any more. It seems redundant to have the sound bar and the stereo system in the living room, so I thought it would be best to connect the TV to the stereo system and get rid of the sound bar. That means I need an amp that has HDMI ARC input. The Krell KAV-300i that I recently recapped, and has been powering the stereo system is a great integrated amp, but it only has analog inputs.

I am not a true-believer when it comes to audio gear. I trust measured specs more than subjective reviews full of purple verbiage. To me an amp is an amp, as long as it isn't poorly built and has adequate power to drive the speakers. Any subtle differences that may exist in sound character will be minor (especially compared to differences in speakers and their room interactions) and I probably won't be able to hear them (see my recent listening test of the SU-1 DAC vs 30 year old VRDS-20 CD player), or will quickly get used to them.

I look for adequate power output, ability to drive low impedance loads (because who knows what speakers I may end up with), adequate input/output capability, quality of construction which includes components and layout, and near the bottom of the list, the way it looks. With a lot of high end audio amplifiers, you pay a lot for artistically machining the amp's face plate, or maybe even the whole chassis. Some look really spectacular, but that's just not how I want to spend my money.

I looked at a lot of different integrated 2 channel amplifiers to see if any had HDMI ARC inputs. There aren't many out there, unless you want to go full surround-sound with 5-17 amplifier channels and speakers. I saw the Advance Paris A10 and A12 amplifiers and really liked their I/O capability. I found a deal on an open-box A12 that was only about $200 more than a new A10, so I ordered the A12. Either one would more than meet my requirements.

Rear view of the A12. There are eight analog inputs, two of which are balanced. Among the inputs is one for MC or MM phono cartridges, with selectable gain and load capacitance. There are also eleven digital inputs, including three optical, three coaxial, two USB, and two HDMI jacks. There's a balanced preamp output, two outputs for subwoofers with selectable LPFs, and two headphone jacks with selectable gains and output impedances. Note: this is not my amp. I found this photo online. Look closely at the labeling under the speaker connectors. It says "A or B Speakers Impedance: 4-16 Ohms" and A+B Speakers Impedance: 6-16 Ohms". My amp says "A or B Speakers Impedance 8-16 Ohms" and "A+B Speakers Impedance: 16 Ohms". It's a mystery!

Since I have a subwoofer, one feature of this amp that I am especially interested in is bass management. There are two subwoofer outputs on the back of the amplifier with switches to control the LPF cutoff frequency at either 75Hz (for larger speakers) or 150 Hz (for smaller speakers, such as my Canton Ergos, though they really should be OK down to 45 Hz). The spec sheet and manual don't say much about bass management. Do the subwoofer outputs switch on and off with the speakers? What is the slope of the roll off? Does it also apply high pass to the A12 amplifier stage I sent an email to Advance Paris asking these questions and got no response. Hmmm.

The corner frequencies for bass management are pretty high, so I don't think they are intended to be used with just an amp/speaker sub. It will need to have its own LPF that you can set to match the main speaker's low frequency cutoff, otherwise you'll have both the sub and the speakers response curves overlapping over a relatively wide frequency range and that could cause some room/system frequency response problems.

I also liked the preamp-out/power-amp-in I/Os. That can be useful for doing stuff like bi/tri-amping a system or adding an equalizer (though it might be better to connect an equalizer to the tape out/amp in). There is no jumper on the back of the amp to connect the preamp output to the power amp input, just a menu selection on the front panel that turns the power amp input on. Does it also turn off the preamp?

Advance Who?

Advance Paris is a French company, with manufacturing in China, like many many brands of audio gear, including some uber high-end stuff. They've been making audio gear since 1995 and selling mostly in the EU. They recently started marketing world-wide, including the US.

The look of the A12 has been compared to McIntosh, and they are similar, but I think the A12 has updated that look.

McIntosh MA12000 hybrid integrated amplifier. Notice any similarities to the A12? Two big meters, tubes visible between them (backlit in green here), knobs and a digital dot matrix display. In this model there are handles, but in other products there are always a couple vertical metal bars along the left and right edges of the front panel.

I'm not entirely sure I like the way the A12 looks - it reminds me of futuristic kitchen appliance that you might see in a 50 or 60s era sci-fi movie. Not that that's bad... Hey, maybe it will go well with my 3D printed Sci-Fi Lamp! Maybe I need to print another with a blue shade to match the VU meters in the amp. We'll see if the design grows on me when I've had the amp for a while.

Sci-Fi Lamp, printed on UMMD using 1mm nozzle and PETG filament. The shade is two identical prints, one green and one transparent edge-glow glass. The red parts are actually 15 identical pieces, stacked inside the shade pieces.

The A12 has a dual-mono (meaning that each channel has its own power supply) class AB power amp that delivers 190 W/ch into 8 Ohms and 280 W/ch into 4 Ohms, so it should be able to drive just about any speakers ever made (more on that, below). A lot of newer amplifiers are class-D circuits, which tend to be small and very efficient, but I'm not so sure about their reliability. I found the full digital amplifier in the Technics SU-G700 interesting, but the Stereophile measurements turned me off - they looked great except for lots of ultrasonic noise in the output. It also doesn't have HDMI input. Maybe the next generation...

The DAC that's built into the A12 is a PCM1796 made by Texas Instruments (originally Burr-Brown, bought by TI in 2000). That chip has been around for over 20 years, and it may not measure as well as some of the newer chips from AKM or ESS, but are the differences audible? Maybe to some, but probably not to me. When you run the incredible SINAD signal from a modern DAC through relatively noisy tubes, does the DAC's high performance really matter?

Yes, the A12 has tubes. For many people that's a selling point, but I'm not sure if it's good or bad. Some people think tubes have a euphonic sound, In the A12 the tubes are biased in class A in the preamp section of the amplifier. If tubes have a "sound". I'd guess it's from noise and distortion- they tend to produce even order harmonics that for some reason sound nicer than the odd order harmonics produced by bipolar transistors. But in a preamp you're probably not going to drive the tubes hard enough to distort audibly, so is there really going to be a difference in the sound other than a poorer S/N? Another different "sound" you might get with tubes is microphonics. That happens when the tubes vibrate. Small changes in the physical position of the elements in the tubes cause changes in capacitance and that can modulate the audio signal. If it gets severe enough (maybe by turning the volume up to 11 so the subwoofer vibrates everything in the room) it can actually cause oscillation.

The tubes are 12AT7 or ECC81 type made by JJ Electronic. That type is still made by more than one company and not too expensive, and should last many years before they need to be replaced, so they're not too much of a problem in that regard. Some tube audio fanatics are into "tube rolling" which means trying tubes by different manufacturers, or old stock tubes, to see if one sounds better than another. I don't suffer from that affliction.

Construction

You know, I hate audio equipment reviews that don't show me the insides of the unit being reviewed. To me, quality of construction is a much more important factor in deciding whether to buy than the looks of the front panel. Why don't more reviewers open up the gear they review? Maybe their agreements with the equipment maker prohibit them from showing off the guts.

Well, I have no such agreement! You're going to see pictures of the guts here.

There are good ways to build electronics and some not so good ways. Here's an example of not-so-good- this is an 80's vintage Soundcraftsmen DX4000 preamp that I recently recapped and sold on ebay. All the I/O switching is done with switches mounted on the front panel, with long wires from the connectors on the back panel. Does it work? Sure. Do I want to buy something like that, at any price, even if it specs well? Nope.

No! This is not the A12! It's a 1988 Soundcraftsmen DX4000 preamp. Can you imagine wiring this? or repairing it? Honestly, it looks like something I would have built when I was in high school and couldn't afford proper tools or parts.

Here's an example of more preferable build quality- the Krell KAV-300i amplifier:

This is more like what I want. This amp wasn't without its problems, but this type of construction is a big improvement over the Soundcraftsmen preamp in the previous photo. The I/O switching is done by relays at the back of the amp, very close to the connectors. There aren't a lot of wires running all over the place.

As of this writing, there aren't many photos of the internals of the A12 online, but what I can find looks like good quality construction. Everything looks modular with PCBs used to connect them together, and minimal cabling.

One of the few images showing internals that I was able to find.

In this video from Advance Paris, at about 4 minutes in, you can see some of the insides of what might be an A12. It looks well laid out, and I see many small relays used to switch signals, similar to the Krell KAV-300i amplifier. I also see some Bennic XPP series film caps used instead of nonpolar electrolytics. While there are many surface mount parts on the PCBs, it looks like the electrolytic caps are through-hole type that will be relatively easy to replace in 20-30 years when they start failing (assuming they last that long, and that radial lead electrolytic caps are still available in 20-30 years). Nice!

More reviews (you may need to translate):

https://www.hifitest.de/test/vollverstaerker/advance-paris-a12-classic-22057

https://www.on-mag.fr/index.php/topaudio/tests-auditions/24521-test-ampli-hifi-advance-paris-a12-classic-une-oeuvre-musicale-complete-et-imposante

https://www.whathifi.com/reviews/advance-paris-a12-classic

Video reviews in French:

https://youtu.be/-pFpBgrVjsM?si=2d2rLTvVqJLoVSOG

https://www.youtube.com/watch?v=0v3YV-tX0MQ

It's Here!

When the amp arrived, I connected B&W 703 S3 speakers and a CD player to both the balanced analog and a coax digital inputs on the amp, and a Squeezebox Touch to another coax input. Everything sounded great, and worked perfectly. Then I tried connecting my TV to the HDMI ARC input. That's when things turned not so great.

I managed to get the HDMI ARC input working a couple times, but have no idea why it started to work and why it stopped. I emailed AP about it, and got a reply within an hour (great!), that the amp is stereo only and I should disable all surround sound multichannel audio capabilities in the source. It would be nice if they included that sort of info in the manual!

I have an Nvidia Shield TV Pro (STVP) connected to my TV via HDMI because the STVP has better video upscaling than the upscaling built into the TV. I have been using the HDMI ARC connection on the TV to connect to an LG Dolby Atmos sound bar, and it was all working fine. After the email from Advance Paris, I went through both the STVP and the TVs setup menus and disabled all multichannel audio.

I messed with it and messed with it, and changed settings, powered down and back up, etc. and could not get it to work. I tried connecting the TV audio to the amp via optical fiber and it worked without and problems, so that's probably how I'm going to use it. Maybe they'll update the manual or there will be a forum with info online somewhere. For now, optical is the way to go.

Photos and some details

I wanted to take pictures from the top and bottom sides, but after removing the top cover, realized that the bottom cover is part of the chassis structure and I'd have to take the whole thing apart to get the bottom off. It seems it is intended to be serviced from the top side only, which requires removing a bunch of stuff I'm not willing to remove right now, so the photos are mostly taken from the top side.

The binding posts on the output are very heavy, and seem to be very good quality. The posts are 7 mm in diameter and the vertical holes that you might insert raw cable or pin plugs into are 3.7 mm in diameter. You can also insert banana plugs into the ends of the posts, and they seem to grip well (with my bananas, anyway).

The power transformers are 120 mm D x 80 mm H. There are multiple windings all called out on the label. The power amp is powered by a dual 46.5V @ 2.5A windings. There are four, big amplifier filter caps (2 for each channel), each is 12,000 uF @ 80V. It looks like all the electrolytic caps are made by Decon and all (everywhere in the amp) appear to be rated for 105C operation, which is good because this amplifier runs warm. It looks like all the electrolytic caps in this amp are through-hole type, easy to replace when the time comes.

For those who aren't aware, electrolytic caps have finite lifetime, usually specified as something like "2000 hours at 105C, max voltage, and max ripple current". That doesn't sound like long, but operating at less than that temperature, voltage, and ripple current extends the operating life. For every 10C below the maximum temp, lifetime essentially doubles, so operating at 45C (about where this amp seems to sit most of the time) multiplies the operating life by 2^6= 64x, which means the caps should last 64 x 2000 hours= 128,000 hours. That's equivalent to 8 hours per day for 16,000 days or 43.8 years.

The tube preamp is on its own PCB and it looks like you have to remove 4 screws and a couple cables to get it out of the amp. Access to the tubes would then be from the front side, I think. There's a metal cover over the tubes that is soldered to the PCB that holds the LEDs that light up the tubes (you didn't think that light came from the tubes, did you?), so you won't be removing that cover when it is time to change the tubes (hopefully many years from now). There are a couple nuts on top of the metal cover that have some shellac on top. If you look closely into the tube window you can see what looks like conical springs that appear to keep the tubes pushed down in their sockets. I think those shellacked nuts are on the ends of the springs.

There are 6 output transistors bolted to the heatsinks in each channel. I can't see the numbers on them.

Inconsistencies and information needed

The manual is lacking in some critical details. There's nothing about how to use the HDMI ports, it doesn't specify exactly what the hi-bias switch does, it doesn't explain whether the preamp is still functional if you turn on the power amp input (could be useful for biamping). It doesn't say if the tubes are on the preamp or power amp side of the power amp input.

I tried to use the HDMI port to connect my TV to the stereo system and ran into a lot of trouble. I emailed AP about it and they responded within and hour (!), telling me to be sure to turn off all surround sound capabilities in the source component (the TV and Shield TV Pro that I use) because the HDMI ports in the A12 are only 2 channel capable. I did that and tried again, and it still wouldn't connect consistently. I'd try it in the morning and it wouldn't work, but by evening it was working for some reason. I switched to one of the optical inputs which worked perfectly on first attempt, and will try messing with HDMI again in the future.

The specs on the web site say the amp can deliver 190W/ch into 8 Ohms and 280 W/ch into 4 Ohms, but two different versions of the amp seem to exist, one in which the speaker terminal labels say 4 Ohms is OK and one that says the minimum speaker impedance is 8 Ohms. I have posted a large photo of the back side of an A12 (above) that shows the 4 Ohm minimum impedance. The back of my amp says 8 Ohms minimum.

The manual says there's a USB driver that can be downloaded at the AP web site, but I was unable to find it. I haven't tried the USB input yet.

I did find a firmware update for the amp on the web site and successfully installed it without any trouble by following the procedure detailed in the English language readme file that was zipped with the update file. The V1.6 update adds a function to always power up with a user specified volume level instead of defaulting to the volume that was set when powering the amp down the last time it was used.

The update file is not found under the "downloads" tab at the web site. It's on the A12 page under the "documents" link, labeled "mise a jour V1.6"

A12 with the top cover off. There are 11 screws that hold the top cover in place.

The back panel (gold) is a structural component, as is the bottom pan (black). There's no taking the bottom off without taking most of the amp apart.

One of the two power transformers in the A12. I would guess that the 210V windings are used to bias the vacuum tubes. The 46.5V 2.5A windings are powering the power amplifier.

The tube preamp board. The tubes are located inside the metal box at the top of the image. It looks like there are 4 cables and 4 screws that have to be removed to take the preamp board out and to access the tubes. The metal cover over the tubes is soldered to the circuit board.

The tube preamp board appears to be held down by 4 screws, one of which is seen near the center of this image. The other boxed area is one of the two shellacked nuts that hold the tube hold-downs in place.