M² Circuits

The audio test panel for the new shop space deserves its own post - so here we go! Strap in as I try to explain all the functionality in one go 😁 The tradition of building my own test panel dates to when I first started at the local repair shop and was amazed by the custom panel built by my mentor. He had built it to suit his work flow and had features all at the flick of a switch - no patch-bay in sight. I have since built a few of my own panels, and while I do have an Audio Precision now I still find digital menus too cumbersome. With the new shop set up differently than my previous space I needed to build something that fit the 19” rack standard and also included fixes and features I have come up with while using my previous panels. In order from top to bottom: Power Amplifier Panel This takes signals from a resistive load box on top of the rack and displays the power on a pair of calibrated meters. It has settings for load impedance (4-8-16Ω) and watts range (10-20-50-100-200W), which ranges the meters and monitor outputs. The load select also controls relays in the load box that set the load resistor configuration. Main Audio Panel This is the hub for everything, the input section and switching allow you to monitor loop back, the DUT input, and power amp panel output. It has input loading select (600-10k-100k) and buffered scope outputs for sending to my millivolt meter, scope, and counter. The output section has selectable sources (EXT-Audio-Mute-Gen), stereo/mono switch, matched T-pad attenuators (10-20-30-40-60dB), output Z switch (600-150Ω), and output terminator (on-off). The output is balanced by two Hammond 804s and the mute function disconnects the outputs from the transformers and shorts H & C together. Power Supply Supplies +/-16V for audio and +24V for indicators and relays to both panels. Front panel pilot lights, test points, and voltage trims. The patch panel for connecting to DUTs is located on my bench so that wires don’t cross in front of me. It has XLRs for the line level and Speakon for power amplifiers. #m2circuits #electronics #design #repairshop #hamilton #canada #madeincanada @hammondmfg #analogaudio

The end of our LA trip is the culmination of one of the largest and most exciting projects to date. The project entailed the restoration and commissioning of Les Paul’s Ampex 300/350 8T-1” tape recorder (also known as “The Octopus”), his Ampex 300/351 3T-0.5” tape recorder, the infamous Les Paul Rein Narma console (known as “The Monster”), all the power supplies, monoblock amplifiers, and the vari-speed amplifier. None of this would have been possible without the help and support of: @rektagon @c.omplena @betoresende A special shoutout to Norm from @audioanonymous1 and @chrissycaskey for putting up with all the FedEx packages we sent in advance and during the trip, and for making us feel like part of the LA audio family. Thank you to @brycegonzales for organizing the legendary audio tech meetup, it was amazing to meet all the folks we have built long distance relationships with over the years. Thank you to everyone who followed along!

New Mulitcaps are in! 1” and 1.375” sizes to replace the two most common can sizes. New boards now have the can com on the outer edge and undersized holes for press fitting test points as solder lugs! They work great in old Tek gear and other vintage pieces that use bolted in cans. Check them out at the new shop page on the website! msquaredcircuits.com/shop/ #multicap #vintage #electronics #pcbdesign #custom #new #designedincanada #toronto #canada #tektronix #m2circuits #repairshop #shop #electronicsrepair #capacitors #restoration

As is tradition, the end of year post! 2025 was another crazy year filled with many projects and repairs. Custom gear builds, bringing a whole Scully to Carnegie, fixing MCI and 3M machines, plus local repairs of every flavour, all made for a dense but incredible time. Thank you to all the folks who made the year so amazing, both in person and virtually. I always enjoy chatting with people to share and learn about everything from baking pies to circuit design. A very special thank you to my wife @sarahelainemiserere for always being supportive of everything I do, even when it means being away from home in Ampex land. I am truly lucky to have Rico @thumprecording and Ben @tubular_audio alongside me in the crusade to fix everyone’s broken crap. Plus, our fun (and wire prep intensive) builds are always a treat. Thank you to the usual suspects, @marquee_sound for always being game to bounce ideas and tell me how engineers actually use studio gear, @modulatedgroove for listening to me rant about how my printer is clogged or how garbage Sony is, @novaluxstereophonic for the FM tuner wisdom, and of course my family for always being my biggest fans ❤️ Here’s to another year filled with friends, family, and tape machines 🥳 #nye #newyears #recap #fyp #audio

It has been a hot minute since a post was made! Enjoy this smattering of photos from my most recent trip to Ampex Land (aka @thumprecording ). We made a good dent in repairs and projects, wrapping up some major ones like the Yamaha PM700 direct out mod, sussing out all the final gremlins on the MCI JH24, and way too many dbx 160s 😅 I have many more photos from this year that haven’t been posted yet - I hope to get around to sharing more of them with ya’ll 😁 Some new PCBs will be added to the store, including a new Rev of the Ampex 440A/B cap board with the option for models that have the “orange wires”, relay boards to replace the flat Omron relays in TEAC decks (like 80-8), and some more ideas that I just need to CAD out. #repairshop #nyc #studio #audio #fyp #instagram #electronics #analog #vintage #proaudio #mci #yamaha #ampex #recording

As is tradition, a collection of photos from throughout the year - and what a year it has been! A special thank you to some very important folks in my life that I am lucky to have: my amazing wife @sarahelainemiserere , my ever-supportive parents and siblings, Rico from @thumprecording , Braden from @marquee_sound , Ben from @tubular_audio , Peter from @modulatedgroove (who listens to every ranting waffling voice message I send), Calvin @ampfreek (who brings me tomatoes, smoked bacon and, Hiwatt PCB layout jobs), and everyone else I’ve had the pleasure of meeting and talking to over the year. I wouldn’t be where I am today without the immense support from everyone ❤️ From the completion of the Les Paul restoration to marrying the love of my life, and all the projects and repairs in between, there hasn’t been a single dull moment. I hope everyone had a wonderful year, and wish you all a Happy New Year that brings nothing but happiness and cool gear 🥳 #repairshop #analog #audio #fyp #m2circuits #canada

Three, practically empty, parted-out Ampex 351 chassis were sent back north with me by Mr. Thump with the plan of breathing new life into these. Instead of scrapping the metal, we decided to build three 351 Mic Preamps with in-house designed PCBs. Hand wired and laced on a custom wiring jig by yours truly. The new record boards added independent Mic and Line transformer inputs, mic input 30dB pad, Altec 1567A EQ with bypass, and a Direct Input with pre/post first stage switching. Everything is relay controlled to keep signal paths short, and thus free from noise and complex wiring. The preamp stage is identical otherwise to the original 351. The new power supply boards feature regulated (and adjustable) 12V heater and relay supply, and modern capacitor footprints. We kept the tube rectifier for the high voltage supply and the traditional unregulated dropper/filter stages. Other features include a meter range switch (+4,+8,+12, OFF), and output attenuator so you can really get crunchy. All this alongside new Cosmo Japanese pots, CineMag output iron, and OG ampex input mic and line iron. With THD+N of 0.1% or better @1kHz @+4dBu out (meter OFF), and 80dB of gain, these turned out great. All three of these units are spoken for, and will be heading back to Brooklyn soon. If you are interested in a build, reach out to Thump and we maybe able to hook you up with a one-of-a-kind creation. #ampex #351 #custom #handwired #analog #audio

The shop will be closed until October 15th, 2024, as I will be busy marrying my better 3/4 @sarahelainemclay and then enjoying some time off while we do some post-wedding travelling 🛫 Enjoy this smattering of photos from the last month, including my sexy new HP 206A oscillator and rearranged equipment rack. Thank you to those that have filled out the waitlist/inquiry form, I will start knocking repairs off the list once we are back! See ya’ll then! #repair #repairshop #hamilton #canada #weddingweek #electronics #engineering #hifi #tapedecks #reeltoreel #hewlettpackard #testequipment

🔥📢AMPEX 351 PCBs NOW FOR SALE📢🔥 The much anticipated time has come, and M² in conjunction with @thumprecording are now offering AMPEX 351 replacement board sets! These are meant to be drop-in replacements for use in 351 preamps. Despite the new layout and footprints, the circuits and values remain the same as the OG design. Aimed towards those with existing electronics knowledge, this is not really a kit, but more of a tool to aid in 351 repairs/restos or building a 351 mic preamp. Yours truly created a 17 page doc that contains everything you should need to use the boards. Schematics, notes, BOMs, etc. Richard and I have poured a lot of time and effort into this project. We have used them in many OG units and custom builds with great success, and we hope that you find them as useful as we do! You can purchase them through the link in my bio 🤠

Another Thump trip in the books! We spent three weeks going through a massive lot of about thirty Ampex preamps, a little over half of them being 351s and the rest 350s and a pair of 403s. These are for sale with some already sold! Reach out to @thumprecording if you’re interested in purchasing one! Along the way I built a stereo 351 mic preamp, mono 351 preamp with added EQ controls, and modified three Ampex 354s for use as mic preamps. I have been sent back north with three more parts 351s that I will turn into mic preamps. I was tasked with repairing a few other pieces of gear, including the unicorn of recording equipment - a Fairchild 670 stereo tube compressor. It needed new caps in a few places and a new control tube in the regulator circuit that was causing the 240V rail to oscillate. Multicap and Sil-Rect boards made the job a breeze. I might do a dedicated post about it in the near future. Braden from @marquee_sound came down to hang and check out the new Thump studio. We had some fun trying out some of my custom built 351 preamps and messing around with all the cool gear. Overall, very happy with the work we got done. We put a huge dent in the pile and got 99% of the Ampex units ready for sale. I will be taking a little time off to recover from the Ampex grind, but will soon get back to the local repairs that await me. Special thanks to Richard for being an excellent host as always ❤️ ~ Maurizio

Those that follow my IG & FB stories know I’ve been plugging away at reopening the shop and finally getting some work done this past month. There are some dedicated posts I need to make about the new test rack and bench, as well as the new shop itself. I’ll try to find the time to make those because there’s some stuff I’m quite excited about of in there! For now here is some June content: a little Revox action, some TEAC time, AMPEX fun, and even the rare event of a Sony product crossing my bench. The shop will be closed for three weeks most likely at the end of July for my quarterly AMPEX-land adventure. Much to be done before then - PCB designs, Binson rebuilds, a few decks along the way - so keep checking the stories cause that’s the best way to stay informed about what’s going on here! All the best, and enjoy the rest of your week! - Maurizio #m2circuits #repairshop #canada #analog #audio #hifi #openreel #fyp #foryoupage #foryou #ig #hammer #summer #engineering #electronics

A smattering of photos from my April 2024 Thump adventures! We were able to make headway on a number of projects, including the new Binson and Ampex 351 replacement circuit boards. I put together three stereo 351s and a mono 350, all fantastic machines. I really enjoyed hearing how fat that full track mono 351 sounded. The new Ampex 351 boards are currently undergoing Rev 02 testing and will be available for purchase in the near future. There will definitely be a post about them when that time comes. A little head relapping was required for some of the 351 head stacks, and I was very happy with how they turned out. The usually Q&A: Yes, I do it by hand. No, you can’t send me heads (I like having the machine present so I can align them after). The Binson Rev 01 replacement board was installed into a unit and was tested, and it functions wonderfully. Quieter and more reliable with updated wiring for easier servicing - I left a small service loop so you can hinge the front panel open and have access to the back of the PCB and all the front panel controls. More on that project soon! A little vintage HP side quest was had getting a late 40s Model 400A AC voltmeter going. Looking forward to using it while I’m down next time ☺️ The final boss was getting the Ampex 300-4 up and running, it required some mods to overcome the cobbled-togetherness of the whole thing. It deserves its own post in the future. For now, know that it sounds as thicc as it looks. A massive thanks to @thumprecording for making this all possible. Richard is always great to work with and is consistently an excellent host ❤️ I was delayed in reopening the shop due to some events outside of my control, but I hope to be accepting new repairs soon so I can take care of my local peeps 🐥