It's always fun to see a new amplifier coming together! Your M2x should provide many many hours of enjoyment through listening, trying a different IPS, and listening some more.
Mechanical transformer hum can be a tricky thing to nail down. The big toroid in my Nain NAP250 used to hum on occasion until I fed it with a Transparent Audio power cord that has built-in filter modules ($$). Nasty bits of garbage are frequently present on our AC mains these days, with all the different types of appliances that get plugged in. You may notice that the transformer is less noisy at different times of the day, or in different weather as you and your neighbors use electric heating or air conditioning. I finally started using big rubber stoppers in the center hole of all my toroids to help dampen any vibrations. I also mount the transformers to 3/8" or thicker slabs of acrylic. Haven't had any mechanical hum problems since.
Interestingly, the transformer that I used in my M2x doesn't have either of those things due to being housed in the Antek steel case. The case itself seems to do the trick of damping vibration. That giant 5U chassis that you are using gives you lots of room for trying different things. You could even go crazy and replace that metal right angle bracket with a simple 1" thick slab of acrylic, or a three piece construction using 1/2" material.
Mechanical transformer hum can be a tricky thing to nail down. The big toroid in my Nain NAP250 used to hum on occasion until I fed it with a Transparent Audio power cord that has built-in filter modules ($$). Nasty bits of garbage are frequently present on our AC mains these days, with all the different types of appliances that get plugged in. You may notice that the transformer is less noisy at different times of the day, or in different weather as you and your neighbors use electric heating or air conditioning. I finally started using big rubber stoppers in the center hole of all my toroids to help dampen any vibrations. I also mount the transformers to 3/8" or thicker slabs of acrylic. Haven't had any mechanical hum problems since.
Interestingly, the transformer that I used in my M2x doesn't have either of those things due to being housed in the Antek steel case. The case itself seems to do the trick of damping vibration. That giant 5U chassis that you are using gives you lots of room for trying different things. You could even go crazy and replace that metal right angle bracket with a simple 1" thick slab of acrylic, or a three piece construction using 1/2" material.
@TungstenAudio
I think I just figured it out. It's not ideal, and I'd like to permanently "prevent" this type of thing, but you nailed it.
It was coming from my bench-top fluorescent work lamp on the same circuit. No lamp - no problem. I turned it on to look inside a bit with the top off - hummmmmmmm.
I have a completely separate circuit for my gear with a big-ol isolation transformer / power conditioner, so I will leave it alone for now. I am now confident that it won't present any issues when I move it to the main rig.
Thank you again for all the support! You've been incredible. I hope to hear more about how your custom IPSs are coming along.
Re: Assembly of ModuShop chassis:
I also had some fun with my 5U400 ModuShop chassis. Noticed the "pulling in" when tightening the inner base plate to the rails.
I settled on the following procedure:
- mount rails to heat sinks, make sure everything is lined up perfectly, tighten.
- mount inner base plate to rails, loosely
- mount front and back panel to rails / heatsink assembly, tighten, thereby making sure they are lined up correctly using a "right angle tool" (don't know the proper English term ... )
- tighten inner base plate
I then was able to remove one heatsink from the chassis to mount boards and FETs, leaving the other heatsink, front and back plate and inner base plate in place. That stayed stable and aligned. Only at the end I did put in first the outer base plate, then the top plate.
Best regards,
Claas
I also had some fun with my 5U400 ModuShop chassis. Noticed the "pulling in" when tightening the inner base plate to the rails.
I settled on the following procedure:
- mount rails to heat sinks, make sure everything is lined up perfectly, tighten.
- mount inner base plate to rails, loosely
- mount front and back panel to rails / heatsink assembly, tighten, thereby making sure they are lined up correctly using a "right angle tool" (don't know the proper English term ... )
- tighten inner base plate
I then was able to remove one heatsink from the chassis to mount boards and FETs, leaving the other heatsink, front and back plate and inner base plate in place. That stayed stable and aligned. Only at the end I did put in first the outer base plate, then the top plate.
Best regards,
Claas
@poseidonsvoice, @chede / Claas, and @Ozark HiFi Doctor - Thank you!
@poseidonsvoice -
you and @6L6 nailed the issue. I had never heard of this (Clearly I've never mounted a transformer before). I hope this saves some other person from having the same issue. I suppose I can feel a bit good about taking a final look around the inside and checking temperatures before sealing it up... Who am I kidding? I just wanted to play with my new IR temp gun... 
Pic of the resulting fix. I lifted the transformer up in the mount, secured it much more tightly with a lock washer and juuuuuust for extra measure cut a piece of rubber to place under the metal top plate.
@poseidonsvoice -
you and @6L6 nailed the issue. I had never heard of this (Clearly I've never mounted a transformer before). I hope this saves some other person from having the same issue. I suppose I can feel a bit good about taking a final look around the inside and checking temperatures before sealing it up... Who am I kidding? I just wanted to play with my new IR temp gun... Pic of the resulting fix. I lifted the transformer up in the mount, secured it much more tightly with a lock washer and juuuuuust for extra measure cut a piece of rubber to place under the metal top plate.
Attachments
The M2x has been operating flawlessly. I posted over in the main thread some time ago that I’ve completed the installation and initial testing of all the daughter cards.
It sounds incredible to my ears with all the daughter cards.
I finally had some time to reformat the pile of notes I copied from the forums and other sources. I also included my overall / very general build sequence with some notes. As mentioned, this is not a build guide. @6L6s build guide and the original schematic thread contain a wealth of information. However, I hope this may help another noob (or anyone for that matter) find or keep track of some great information. I also recommend reading the F4 and F5 threads and the PSU thread. The knowledge shared is incredible. I still re-read them and pick up new things each time. Nothing here is meant to be comprehensive. It’s a bit random, but it is what I used, and my amp turned out OK.
Note added later since I’ve been a slacker about getting this up.
I adore the M2x. I’ve posted some impressions over in the main thread. I still have yet to do any op-amp rolling on Tucson, and I haven’t learned how to tune the harmonic distortion from the Ishikawa board, but that can all come with time. The M2x gave up its home yesterday to the Aleph J I just finished. When I get another chassis and PSU built, then I’ll have more options. I am ready to mount some SissySIT boards, and start the builds for the F4 and F5 boards. The first First Watt got me hooked!
So far… the Norwood and Austin boards have by far the most listening time. There’s just something about them I like. Mark and Jim nailed it. If you want input stages that use modern non-unobtainium parts with (to me) equal or better sound to the original Toshiba JFETs, it can be done.
Here’s the notes I promised. Enjoy your builds!
M2x Notes
MATERIALS
USE THE BoM. However, I had to make a few extra parts orders b/c I didn’t get all my parts initially, and I made a few errors. Not everything is on the BoM. Also, I put in a list of tools I’d have never known about until trying to build an amp.
List of Extra Stuff Not On BOMs
• Chassis and all mounts and I/Os / IEC – Standoffs or Mounts
• Power Transformer(s) and mount(s) and/or cases
• CL-60s or other inrush limiting devices
• Safety Cap for AC Input
• Wire
• Terminal Blocks
• Quick Connect Terminals (if that’s your style). Wire size – Yellow and Blue
• Ring Terminals to fit #6 holes and < width between terminals. Wire size – Blue (If that’s your style)
Less Common Tools I never knew I might need.
• Dummy Load Resistors – 4 or 8 Ohm 100W or 200W – wire accordingly – See ZM’s post about not needing them for this amp.
• Shorting Plugs – Used for checking DC offset
• Dim Bulb Tester – Check for shorts or other critical issues. It may save your amp. Build one. They’re relatively inexpensive. If I had to do it over, I’d do it like @6L6.
• Variac – to check DC offset at slightly higher and lower mains. Bring voltage up slowly for initial checks. Not needed, but can be a stress-lowering device.
• Kill A Watt – Check total current draw of amp. Not needed.
Parts Suppliers –
Mouser - https://www.mouser.com/
Digi-Key - DigiKey Electronics - Electronic Components Distributor
Arrow - https://www.arrow.com/
AVNet - Avnet: Quality Electronic Components & Services
Newark / Element14 (Tied to AVNet) - https://www.newark.com/
RSComponents - https://uk.rs-online.com/web/
Site to find who has parts – www.octopart.com
PICTURES
Here are some pictures I found very useful and “inspirational” (I stole shamelessly from their builds).
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Easy to see LED front panel
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Shows full DIYAudio UPS with Diodes
Official M2 schematic
The diyAudio First Watt M2x
Aleph J Build Guide – Great pics of overall wiring and IEC etc.
Aleph J illustrated build guide
Dual Mono
Official M2 schematic
Official M2 schematic
BOARD ASSEMBLY NOTES
Here are the notes I kept nearby before I built any of the boards. I also had the schematics and the build guide open for each. For the daughter cards, Mark’s notes were my biggest asset.
Daughter Boards
Ishikawa – No directional orientation needed for RV1. Set to middle
Tuscon – Socket the OpAmp, Ensure correct diode direction.
Mountain View - Ensure correct LEDs. Ensure correct LED orientation.
Norwood – Be careful re: SMD. Inspect closely. Ensure correct diode direction
Austin – Tight board. Watch for bridges. ENSURE correct orientation of transistors.
GOOD PICTURES FOR VERIFYING NORWOOD ~POST 1341
PSU
Ensure correct values for input buffer before installing diodes / heatsinks.
Amp Boards
Ensure proper orientation of optocoupler and diodes.
Leave a bit of space under the 3W resistors
No directional orientation for RV1
Test Edcors for continuity before installation.
See post #1189 for excellent description of spacing for pin #1 of Edcors! Essentially don’t force them.
Use non-biblical values to ensure ease of setting/nulling DC offset.
Solder input wires prior to mounting boards to heatsinks
Mounting MOSFETs and Board to Heatsinks
• Clean heatsinks
• Use a fine polishing emery board (or similar) to polish the heatsinks prior to installing MOSFETs.
• Debur! See saga of one gentleman that was going through MOSFETs due to shorts
• Don’t break the standoffs – clean the holes and/or use a steel standoff. Don’t force.
• MOSFET legs get bent at narrowing point
• Test fit prior to soldering - final check for clearance under boards
• Check for shorts on all legs of MOSFETs to heatsinks
• Check with diode test on DMM – Should show NO voltage.
WIRING / GROUNDING / CHASSIS ASSEMBLY / TESTING
Here are the notes I put together for myself re: wiring and the overall testing of the assembled amp.
Good thoughts on overall assembly order and testing…
Official M2 schematic
• Rough layout. Place components – get an idea where things go
• Add space between inner chassis and bottom plate
• Temp wire mains to terminal block with cap (heatshrink legs of cap)
• Temp wire primaries to terminal block with CL-60s (heatshrink legs of CL-60s)
• Temp wire safety earth to chassis
• Temp wire transformer shield and CL-60 (to audio ground) to chassis ground
• Connect switch to IEC and Fuse (2 fuses – hot and neutral) the IEC
DIM Bulb test PSU - Check Rail Voltages
• Place components in final locations on bottom chassis and secure
• NOTE – Ensure metal toroid mounts don’t touch base plate. See – “short turn”
• Final wiring ready
Final Checks and DC Offset
• Verify that the power inputs are not shorted to ground with a multi meter.
• Dim Bulb - Don't forget to remove the Dim Bulb tester after the check!
MUSIC!!!!!
-------------------------
RANDOM TESTING NOTES
Everything below was cut and pasted from the forums. These are not my words. They’re stolen shamelessly and sometimes paraphrased. You can find the original text by searching. Occasionally there are links to the posts and a post number. All of the information below was extremely helpful to me.
M2x thread See post 1199 for questions about testing. See 1201 for @6L6’s answer for part of it. Really good continuation at around post 1209. More information ~1228. Great stuff.
Joshua’s follow-up post #1235
Test PSU without amp channels attached, connect one amp board, test and adjust, disconnect that one, connect the other, test and adjust, if all ok, try them both and listen to beautiful music.
It's a but more complex than that, but the important thing to understand is hook it all up and hope the smoke stays in at initial power-up is not the best plan, and any incremental steps are useful.
See 1633 for exact method to check continuity of MOSFETs to heatsinks / ground!
Regarding wiring and hum
Wiring to each amp board
- Official M2 schematic
GENERAL TESTING
Test all resistors prior to installation. Test all Caps. Check diode orientation.
• How to measure low resistances
The diyAudio First Watt M2x
Measuring IDSS
The diyAudio First Watt M2x
Check Edcors before installation
• “The most important thing to measure on the Edcors, IMO, is whether any of the coils are open-circuit.”
• “One of my output coils on one Edcor was damaged and did not show any resistance on a voltmeter. Tea-Bag said he heard one other person had this problem. The tiny magnet wires are fragile. One could have been loosened or broken during shipment or installation.”
• “Better to measure before installation! I soldered in mine and had to track down the problem after the build with a scope and signal generator.”
• See post #1189 for excellent description of spacing for pin #1 of Edcors!
Daughter boards
“ If you decide to solder your Austin boards anyway, please make sure you’ve got adequate lab equipment to, at the very least, apply the requisite ±25V DC power supplies and measure the supply current. If you’ve got an incorrectly assembled board, it’s vastly preferable to have it catch fire on your lab bench, near your lab fire extinguisher, rather than inside your M2X amplifier.”
@Elwood625 asks some great questions at 1914.
To test daughter boards - V+ to pin 3 and ground to pin 1.
Power Supply check then attaching each component
Dim Bulb Tester. DO NOT USE WHILE SETTING OFFSET OR BIAS *Bias on M2x is automatic.
Light Bulb Tester
https://www.antiqueradio.org/dimbulb.htm
Important Note – if building dim build tester per the schematic of antique radio.org and using a standard US outlet – ensure to remove the tab between outlets on the neutral (larger prong side) and leave the other side intact.
Some wisdom from Andrew T – paraphrased from posts beginning around #26
Light Bulb Tester
DC Offset process - Recommended offset +- 30mV
Official M2 schematic
#1563 AC Noise - The diyAudio First Watt M2x
You can take a DMM and set it to AC at the highest resolution (most sensitive setting) and measure the output with shorted inputs. Your reading should be way below 1 mV. A good power amp should not show more than 0.2 mV of noise at the output. It is probably difficult to get much below 100 uV of noise.
Put the amp on a "Kill A Watt" $20 household wattmeter, it ought to draw 135-160 watts with input signal jacks shorted, if everything's assembled correctly.
“I don't know how everyone else does it but when I assemble an electrical device, I check for continuity to chassis on every module as I install them, before ground connections are made.It always looks like there will be no problem and loads of clearance to chassis parts but all it takes is a strand of wire to become dangerous. I also check between rails and outputs on amplifier boards or any high power transistor board with the meter set to diode check. Red lead on V+ rail, black on output, the red on output, black on - rail. If you have a voltage reading on either rail you likely have an output device or driver shorted or reversed. After the unit is assembled, check for continuity between mains, neutral and chassis. If you see any sign of trouble, find it before you power up. The problem won't fix itself. There should never be that surprise flash and smoke when you power up the first time. Continuity checks only take a couple minutes and can save lots of parts and/or your life. Really the only surprise you should run into is possible meltdown from oscillation, but that's what your bulb limiter is there for.
diyAudio Power Supply Circuit Board v3 illustrated build guide
POTENTIAL FUTURE MODIFICATIONS AND NOTES
Dual Mono or Monoblocks?
Dual Mono – Could fit in 5U case
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- Post re: discussion re: how to stack the power transformers for dual mono - Official M2 schematic
Bypass Caps for C2 and C3 – Learn this.
- Official M2 schematic
Potential to bypass C2? Check schematics and ensure correct. Start here.
- Official M2 schematic
Motor Run Caps? See Elwood’s build and questions.
• Elwood’s question – Bottom of 1948
• Tungsten Audio Answer – Addition of some other additional capacitance - 1949
• ZM Answers based on design - 1951
Separate Power Supply
• Official M2 schematic
Papa’s note for <100Ohm output resistance not necessitating IPS. How to allow for bypass + daughter boards? All output resistance for all my components is <100Ohm. From Papa – “Keep in mind that any reasonably low output impedance preamp (say <100 ohms) will drive this circuit without need for the input buffers”.
@CubicIncher - put in a switch to go between the daughter boards. Very cool!
Notes for Mu Metal or other Edcor shielding in the future –
- Official M2 schematic
- I stand corrected, grounding the mu metal shield is not necessary. I am sure it does not hurt, so I am not going to take apart my M2 just to remove those grounding wires.
- Link to copper tape shielding on Edcor site - https://www.edcorusa.com/copper-shielding
- A source for a ready-made Edcor shield / box
It's a TEKO 3710. I got mine at Reichelt, Germany: at reichelt elektronik
Joshua - great thoughts on the standoffs and star washers used to connect the daughter boards to the main boards.
The diyAudio First Watt M2x
See Joshua’s offer for additional boards with connections.
See posts 2013 and following answers for how to adjust Ishikawa RV1. Just set it in the middle for now.
The diyAudio First Watt M2x
Add XLRs – See Aleph J thread.
Roll OpAmps in Tuscon
• DIP8 / SOIC - Watch the material type, some combinations of plating materials can be bad together (avoid gold/tin combinations)
o LCQT-SOIC8-8 Aries Electronics | Mouser
o 4808-3004-CP 3M Electronic Solutions Division | Mouser
• OpAmps
Worthy contenders might include the LT1115, OPA227, OPA134, OPA1611.
• Great question about opamp swapping for Tuscon
The diyAudio First Watt M2x
@Xrk971 posted about a possible new daughterboard. Mark Johnson has posted about requesting folks to audition new designs.
INTERESTING STUFF
Interesting perspective on resister comparisons / noise.
The diyAudio First Watt M2x
Great beginner’s article.
http://www.decdun.me.uk/gainclone_psu.html
Nelson Pass discussing modularity
The diyAudio First Watt M2x
Nifty idea for swapping in parts to check values – Pin Sockets
https://no.mouser.com/ProductDetail/Harwin/H3155-05?qs=/ha2pyFadugBFPtvz19zBl50O3n52lac0SLnjqncec0=
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Official M2 schematic
Paper on Capacitors
Download this pdf to your computer and save it somewhere that you can find it again.
Power Transformers and understanding
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Mark’s summary of power transformer needs
The diyAudio First Watt M2x
Wire Choices
• RussellC - For wiring, I usually go to Apexjr, silver coated Teflon insulation, Mil spec....solid, stranded, whatever gauge and color.
• @6L6 – Basically any of the Mic cable (2-conductor plus shield) will work perfectly for the whammy –
o W2552 Mogami W2552 Microphone Cable (Black)
o W2549 Mogami W2549 Long Run Mic Cable (Blue)
o W2697. Mogami W2697 Miniature Balanced Mic Cable (By the Foot)
If you order from there, spend 5 bucks and do yourself a favor and get 20ft of 2381 as well, it's a small flexible coax that makes great wiring to/from RCA jacks and such. My absolute favorite for wiring RCAs to PCBs. Mogami W2381 Black Coaxial Cable, 50 Ohm (By the Foot)
• “I think ZM uses silver plated copper Mil-Spec 22 AWG M22759/11” – SissySit Building Tips #108
How to use the Mega328
https://www.amazon.com/Using-Yosoo-...=using+yosoo&qid=1558492174&s=gateway&sr=8-1
OTHERS’ BOMs
It sounds incredible to my ears with all the daughter cards.
I finally had some time to reformat the pile of notes I copied from the forums and other sources. I also included my overall / very general build sequence with some notes. As mentioned, this is not a build guide. @6L6s build guide and the original schematic thread contain a wealth of information. However, I hope this may help another noob (or anyone for that matter) find or keep track of some great information. I also recommend reading the F4 and F5 threads and the PSU thread. The knowledge shared is incredible. I still re-read them and pick up new things each time. Nothing here is meant to be comprehensive. It’s a bit random, but it is what I used, and my amp turned out OK.
Note added later since I’ve been a slacker about getting this up.
I adore the M2x. I’ve posted some impressions over in the main thread. I still have yet to do any op-amp rolling on Tucson, and I haven’t learned how to tune the harmonic distortion from the Ishikawa board, but that can all come with time. The M2x gave up its home yesterday to the Aleph J I just finished. When I get another chassis and PSU built, then I’ll have more options. I am ready to mount some SissySIT boards, and start the builds for the F4 and F5 boards. The first First Watt got me hooked!
So far… the Norwood and Austin boards have by far the most listening time. There’s just something about them I like. Mark and Jim nailed it. If you want input stages that use modern non-unobtainium parts with (to me) equal or better sound to the original Toshiba JFETs, it can be done.
Here’s the notes I promised. Enjoy your builds!
M2x Notes
MATERIALS
USE THE BoM. However, I had to make a few extra parts orders b/c I didn’t get all my parts initially, and I made a few errors. Not everything is on the BoM. Also, I put in a list of tools I’d have never known about until trying to build an amp.
List of Extra Stuff Not On BOMs
• Chassis and all mounts and I/Os / IEC – Standoffs or Mounts
• Power Transformer(s) and mount(s) and/or cases
• CL-60s or other inrush limiting devices
• Safety Cap for AC Input
• Wire
o Mains to Primary
o DC Power
o Signal
• Fuses – 2.5A Slow Blow (for 120VAC Mains)o DC Power
o Signal
• Terminal Blocks
• Quick Connect Terminals (if that’s your style). Wire size – Yellow and Blue
• Ring Terminals to fit #6 holes and < width between terminals. Wire size – Blue (If that’s your style)
Less Common Tools I never knew I might need.
• Dummy Load Resistors – 4 or 8 Ohm 100W or 200W – wire accordingly – See ZM’s post about not needing them for this amp.
• Shorting Plugs – Used for checking DC offset
• Dim Bulb Tester – Check for shorts or other critical issues. It may save your amp. Build one. They’re relatively inexpensive. If I had to do it over, I’d do it like @6L6.
• Variac – to check DC offset at slightly higher and lower mains. Bring voltage up slowly for initial checks. Not needed, but can be a stress-lowering device.
• Kill A Watt – Check total current draw of amp. Not needed.
Parts Suppliers –
Mouser - https://www.mouser.com/
Digi-Key - DigiKey Electronics - Electronic Components Distributor
Arrow - https://www.arrow.com/
AVNet - Avnet: Quality Electronic Components & Services
Newark / Element14 (Tied to AVNet) - https://www.newark.com/
RSComponents - https://uk.rs-online.com/web/
Site to find who has parts – www.octopart.com
PICTURES
Here are some pictures I found very useful and “inspirational” (I stole shamelessly from their builds).
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Easy to see LED front panel
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Shows full DIYAudio UPS with Diodes
Official M2 schematic
The diyAudio First Watt M2x
Aleph J Build Guide – Great pics of overall wiring and IEC etc.
Aleph J illustrated build guide
Dual Mono
Official M2 schematic
Official M2 schematic
BOARD ASSEMBLY NOTES
Here are the notes I kept nearby before I built any of the boards. I also had the schematics and the build guide open for each. For the daughter cards, Mark’s notes were my biggest asset.
Daughter Boards
Ishikawa – No directional orientation needed for RV1. Set to middle
Tuscon – Socket the OpAmp, Ensure correct diode direction.
Mountain View - Ensure correct LEDs. Ensure correct LED orientation.
Norwood – Be careful re: SMD. Inspect closely. Ensure correct diode direction
Austin – Tight board. Watch for bridges. ENSURE correct orientation of transistors.
GOOD PICTURES FOR VERIFYING NORWOOD ~POST 1341
PSU
Ensure correct values for input buffer before installing diodes / heatsinks.
Amp Boards
Ensure proper orientation of optocoupler and diodes.
Leave a bit of space under the 3W resistors
No directional orientation for RV1
Test Edcors for continuity before installation.
See post #1189 for excellent description of spacing for pin #1 of Edcors! Essentially don’t force them.
Use non-biblical values to ensure ease of setting/nulling DC offset.
Solder input wires prior to mounting boards to heatsinks
Mounting MOSFETs and Board to Heatsinks
• Clean heatsinks
• Use a fine polishing emery board (or similar) to polish the heatsinks prior to installing MOSFETs.
• Debur! See saga of one gentleman that was going through MOSFETs due to shorts
• Don’t break the standoffs – clean the holes and/or use a steel standoff. Don’t force.
• MOSFET legs get bent at narrowing point
• Test fit prior to soldering - final check for clearance under boards
• Check for shorts on all legs of MOSFETs to heatsinks
• Check with diode test on DMM – Should show NO voltage.
o (+) Lead to V+ and (-) Lead to output
o (-) Lead to V- and (+) Lead to output
o (-) Lead to V- and (+) Lead to output
WIRING / GROUNDING / CHASSIS ASSEMBLY / TESTING
Here are the notes I put together for myself re: wiring and the overall testing of the assembled amp.
Good thoughts on overall assembly order and testing…
Official M2 schematic
• Rough layout. Place components – get an idea where things go
• Add space between inner chassis and bottom plate
• Temp wire mains to terminal block with cap (heatshrink legs of cap)
• Temp wire primaries to terminal block with CL-60s (heatshrink legs of CL-60s)
• Temp wire safety earth to chassis
• Temp wire transformer shield and CL-60 (to audio ground) to chassis ground
• Connect switch to IEC and Fuse (2 fuses – hot and neutral) the IEC
DIM Bulb test PSU - Check Rail Voltages
• Place components in final locations on bottom chassis and secure
• NOTE – Ensure metal toroid mounts don’t touch base plate. See – “short turn”
• Final wiring ready
Final Checks and DC Offset
• Verify that the power inputs are not shorted to ground with a multi meter.
• Dim Bulb - Don't forget to remove the Dim Bulb tester after the check!
o Hook up V+,V-, and PS ground to channel A, turn on the power and look for smoke.
o Power off and disconnect Channel A
o Hook up V+,V-, and PS ground to channel B, turn on the power and look for smoke.
o Power off
o Hook up V+,V-, and PS ground to channel A,
• Initial DC Offseto Power off and disconnect Channel A
o Hook up V+,V-, and PS ground to channel B, turn on the power and look for smoke.
o Power off
o Hook up V+,V-, and PS ground to channel A,
o Close up chassis (temp with top lid no secure), tidy and secure wiring
o Short Inputs
o Attach DMMs to Speaker Terminals or Output and Ground O on amp boards
o Power on and rough in offset
• Finish Case and final DC offset and checkso Short Inputs
o Attach DMMs to Speaker Terminals or Output and Ground O on amp boards
o Power on and rough in offset
o 5U case assembly case assembly. See earlier posts in this thread for some good advice. See if 4U thread is back up and has new pics.
o Power up
o Allow to set for an hour or more – fine tune DC offset
o Check DC Offset after 24 hours
o Power up
o Allow to set for an hour or more – fine tune DC offset
o Check DC Offset after 24 hours
MUSIC!!!!!
-------------------------
RANDOM TESTING NOTES
Everything below was cut and pasted from the forums. These are not my words. They’re stolen shamelessly and sometimes paraphrased. You can find the original text by searching. Occasionally there are links to the posts and a post number. All of the information below was extremely helpful to me.
M2x thread See post 1199 for questions about testing. See 1201 for @6L6’s answer for part of it. Really good continuation at around post 1209. More information ~1228. Great stuff.
Joshua’s follow-up post #1235
Test PSU without amp channels attached, connect one amp board, test and adjust, disconnect that one, connect the other, test and adjust, if all ok, try them both and listen to beautiful music.
It's a but more complex than that, but the important thing to understand is hook it all up and hope the smoke stays in at initial power-up is not the best plan, and any incremental steps are useful.
• Verify that the power inputs are not shorted to ground with a multi meter. You should also check other spots on the board if you can figure out which ones. If not, just use the bulb tester when you put power to the boards.”
• Do check for a short between all three legs of each mosfet and the heatsink.
• Hook up V+,V-, and PS ground to channel A, turn on the power and look for smoke.
If you use the Mountain View board, it has a LED that will warm your heart when it glows.
• If all is good, short the input (power it off first), and start tweaking the DC offset. Give it 20 minutes or so, and tweak it again. Put the probes directly on the speaker outputs of the board, not at the speaker end of the speaker wire (binding posts really should not be connected yet, especially if they are not insulated).
• Turn off the amp, disconnect Channel A, and hook up channel B.
• Repeat the above process.
• Power off, hook up channel A, and let it warm up for a couple of hours. Once your DC offset is stable and as close to zero as you can get it, put an 8ohm 100W resistor across the speaker terminals, and do a final offset. I found the resistor made no difference, but it made me sleep better
• My amp needed a small tweak 24 hours later, and has been dead stable ever since.
• Once all that is done, then hook up the speaker terminals. I used an old pair of speakers to make sure it was working, then hooked it up to my mains speakers.
• Do check for a short between all three legs of each mosfet and the heatsink.
• Hook up V+,V-, and PS ground to channel A, turn on the power and look for smoke.
If you use the Mountain View board, it has a LED that will warm your heart when it glows.
• If all is good, short the input (power it off first), and start tweaking the DC offset. Give it 20 minutes or so, and tweak it again. Put the probes directly on the speaker outputs of the board, not at the speaker end of the speaker wire (binding posts really should not be connected yet, especially if they are not insulated).
• Turn off the amp, disconnect Channel A, and hook up channel B.
• Repeat the above process.
• Power off, hook up channel A, and let it warm up for a couple of hours. Once your DC offset is stable and as close to zero as you can get it, put an 8ohm 100W resistor across the speaker terminals, and do a final offset. I found the resistor made no difference, but it made me sleep better
• My amp needed a small tweak 24 hours later, and has been dead stable ever since.
• Once all that is done, then hook up the speaker terminals. I used an old pair of speakers to make sure it was working, then hooked it up to my mains speakers.
See 1633 for exact method to check continuity of MOSFETs to heatsinks / ground!
Regarding wiring and hum
On the subject of hum and where to put the speaker ground. If moving the ground off the board and onto the PS reduces hum, there is probably some ground loop. A likely place for the ground loop is the speaker terminals. If they are not insulated, then you will almost for sure have a ground loop. My speakers are grounded to the board, and I have no hum at all.
I think I'd twist the pairs of wires together, that run from each RCA input jack to each PCB's input pins. I'd do this to reduce hum, and also to feel good that I did something, I took active steps, toward reducing hum
Directly from the build guide re: grounding.
PCB GND The silkscreen text on the M2X amplifier board, and the text on the M2X schematic diagram, calls out three different grounds.
GND.I is the input ground, the second wire in the two wire pair which connects the input jack to the amplifier PCB.
GND.P is the power ground. There are two twisted pairs of wires which connect the amplifier board to the PSU board. One twisted pair is (VPOS and GND.P), the other twisted pair is (VNEG and GND.P). The connectors for VPOS and GND.P are placed close together for easy wiring. Similarly the connectors for VNEG and GND.P are placed close together for easy wiring.
GND.O is the (optional) output ground. If desired, you can connect a twisted pair of wires between the amplifier board and the loudspeaker output jacks: (OUTPUT and GND.O). However many builders find that hum and noise is reduced if the speaker ground is connected on the PSU circuit board rather than on the amplifier circuit board. Try them both and see which you prefer.
TungstenAudio Guidance:
I recommend connecting the negative speaker binding posts directly to the ground attachment points on the Universal PSU. Each of the main channel boards still needs its own ground wire, which can be routed in parallel with the positive speaker output. The VPOS and VNEG supply wires should be routed in parallel between each channel board and the PSU. See post #1666 in the M2x thread for a picture of how this was done.
Post 1666 - The diyAudio First Watt M2x
Discussion of star ground and how to do it to reduce noise
- Start at ~1110 and go to ~ Official M2 schematic
Toroid Placement and ensure secondaries are as far away from Edcors as possible.
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- Interesting question about running power supply orientation for symmetrical wiring in 5U. Official M2 schematic
- From the man himself - “Something I have always done on FW amps is to rotate the toroid +/-60 deg in operation, as one position will give minimum noise. Usually there is a lobe of radiation, and pointing it at (or away) from the right spot is a big help.
- Saga of potentially a less than ideal toroid (not the placement) in original M2 thread.
- Transformer orientation if mounted vertically on the front. I was talking to somebody about that quite recently and yes, it does make a difference, and yes, having the wires face front (away from circuitry) seems to be the best orientation. See pictures and posts around #1182
- Transformer mounting bracket. “Bracket is an L-300 from Toroid Corporation. The L-300 is a good fit for the AnTek AS-3218. I have also used the L-625 L-bracket which is a good fit for the Antek AS-4218”
From ZM “toss that nasty coax on input and use just twisted pair of tiniest solid core wire you have”
Explanation and Follow-up
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- “Anything from 24ga to 30ga works well. I use 24ga solid silver for connections and for interconnects.
Route Mains wiring between mesh bottom and bottom of chassis.
- Official M2 schematic
- https://www.zenmod.in.rs/amplifying/babelfish-j-v2/
How to wire CL60sI think I'd twist the pairs of wires together, that run from each RCA input jack to each PCB's input pins. I'd do this to reduce hum, and also to feel good that I did something, I took active steps, toward reducing hum
Directly from the build guide re: grounding.
PCB GND The silkscreen text on the M2X amplifier board, and the text on the M2X schematic diagram, calls out three different grounds.
GND.I is the input ground, the second wire in the two wire pair which connects the input jack to the amplifier PCB.
GND.P is the power ground. There are two twisted pairs of wires which connect the amplifier board to the PSU board. One twisted pair is (VPOS and GND.P), the other twisted pair is (VNEG and GND.P). The connectors for VPOS and GND.P are placed close together for easy wiring. Similarly the connectors for VNEG and GND.P are placed close together for easy wiring.
GND.O is the (optional) output ground. If desired, you can connect a twisted pair of wires between the amplifier board and the loudspeaker output jacks: (OUTPUT and GND.O). However many builders find that hum and noise is reduced if the speaker ground is connected on the PSU circuit board rather than on the amplifier circuit board. Try them both and see which you prefer.
TungstenAudio Guidance:
I recommend connecting the negative speaker binding posts directly to the ground attachment points on the Universal PSU. Each of the main channel boards still needs its own ground wire, which can be routed in parallel with the positive speaker output. The VPOS and VNEG supply wires should be routed in parallel between each channel board and the PSU. See post #1666 in the M2x thread for a picture of how this was done.
Post 1666 - The diyAudio First Watt M2x
Discussion of star ground and how to do it to reduce noise
- Start at ~1110 and go to ~ Official M2 schematic
Toroid Placement and ensure secondaries are as far away from Edcors as possible.
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- Interesting question about running power supply orientation for symmetrical wiring in 5U. Official M2 schematic
- From the man himself - “Something I have always done on FW amps is to rotate the toroid +/-60 deg in operation, as one position will give minimum noise. Usually there is a lobe of radiation, and pointing it at (or away) from the right spot is a big help.
- Saga of potentially a less than ideal toroid (not the placement) in original M2 thread.
- Transformer orientation if mounted vertically on the front. I was talking to somebody about that quite recently and yes, it does make a difference, and yes, having the wires face front (away from circuitry) seems to be the best orientation. See pictures and posts around #1182
- Transformer mounting bracket. “Bracket is an L-300 from Toroid Corporation. The L-300 is a good fit for the AnTek AS-3218. I have also used the L-625 L-bracket which is a good fit for the Antek AS-4218”
From ZM “toss that nasty coax on input and use just twisted pair of tiniest solid core wire you have”
Explanation and Follow-up
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- “Anything from 24ga to 30ga works well. I use 24ga solid silver for connections and for interconnects.
Route Mains wiring between mesh bottom and bottom of chassis.
- Official M2 schematic
- https://www.zenmod.in.rs/amplifying/babelfish-j-v2/
- Official M2 schematic
- Zen Mod’s full build with pics - Official M2 schematic
- From the man himself – “Just for the record, the 6moons photo shows the thermistor which is in series with the AC line. There is another one hidden which connects signal ground to chassis/earth.
Credit for that invention goes to one of the technicians at Adcom years ago - I am sorry that I have forgotten his name. In that photo you can also see the Mu-metal shields I made for the Edcor transformers. I found I didn't need them for the Jensen transformers, but it is also important to keep them as far from the power transformer as possible and rotate the toroid for least noise on both channels with the RCA input connections attached to a source.”
- Picture of 6Moons referenced http://www.6moons.com/audioreviews/firstwatt11/open1_big.jpg
- Official M2 schematic
- ZM “IEC earth tab must go directly to chassis then main audio GND point goes through CL60 to same point on chassis”
- See Mark’s thread on alternatives to CL-60s
- Zen Mod’s full build with pics - Official M2 schematic
- From the man himself – “Just for the record, the 6moons photo shows the thermistor which is in series with the AC line. There is another one hidden which connects signal ground to chassis/earth.
Credit for that invention goes to one of the technicians at Adcom years ago - I am sorry that I have forgotten his name. In that photo you can also see the Mu-metal shields I made for the Edcor transformers. I found I didn't need them for the Jensen transformers, but it is also important to keep them as far from the power transformer as possible and rotate the toroid for least noise on both channels with the RCA input connections attached to a source.”
- Picture of 6Moons referenced http://www.6moons.com/audioreviews/firstwatt11/open1_big.jpg
- Official M2 schematic
- ZM “IEC earth tab must go directly to chassis then main audio GND point goes through CL60 to same point on chassis”
- See Mark’s thread on alternatives to CL-60s
Wiring to each amp board
- Official M2 schematic
GENERAL TESTING
Test all resistors prior to installation. Test all Caps. Check diode orientation.
• How to measure low resistances
The diyAudio First Watt M2x
Measuring IDSS
The diyAudio First Watt M2x
Check Edcors before installation
• “The most important thing to measure on the Edcors, IMO, is whether any of the coils are open-circuit.”
• “One of my output coils on one Edcor was damaged and did not show any resistance on a voltmeter. Tea-Bag said he heard one other person had this problem. The tiny magnet wires are fragile. One could have been loosened or broken during shipment or installation.”
• “Better to measure before installation! I soldered in mine and had to track down the problem after the build with a scope and signal generator.”
• See post #1189 for excellent description of spacing for pin #1 of Edcors!
Daughter boards
“ If you decide to solder your Austin boards anyway, please make sure you’ve got adequate lab equipment to, at the very least, apply the requisite ±25V DC power supplies and measure the supply current. If you’ve got an incorrectly assembled board, it’s vastly preferable to have it catch fire on your lab bench, near your lab fire extinguisher, rather than inside your M2X amplifier.”
@Elwood625 asks some great questions at 1914.
To test daughter boards - V+ to pin 3 and ground to pin 1.
See posts 1943 through 1945.
Elwood’s final values at 1948
I posted some follow ups starting at Post 2049
The diyAudio First Watt M2x
and ending at ~Post 2068
The diyAudio First Watt M2x
Below are the readings +- 0.1mA
Elwood’s final values at 1948
o Austin 1 = 8.26mA
o Austin 2 = 8.30mA
o Tucson 1 = 4.49mA
o Tucson 2 = 4.36mA
o Mountain View 1 = 23.81mA
o Mountain View 2 = 23.89mA
o Austin 2 = 8.30mA
o Tucson 1 = 4.49mA
o Tucson 2 = 4.36mA
o Mountain View 1 = 23.81mA
o Mountain View 2 = 23.89mA
I posted some follow ups starting at Post 2049
The diyAudio First Watt M2x
and ending at ~Post 2068
The diyAudio First Watt M2x
Below are the readings +- 0.1mA
• Tucson - 8.7 and 8.7
• Mountain View- 28.8 and 28.8
• Ishikawa - 7.5 and 7.5
• Austin - 11.6 and 12.1
• Norwood - 15.8 and 15.9
• Mountain View- 28.8 and 28.8
• Ishikawa - 7.5 and 7.5
• Austin - 11.6 and 12.1
• Norwood - 15.8 and 15.9
Power Supply check then attaching each component
Dim Bulb Tester. DO NOT USE WHILE SETTING OFFSET OR BIAS *Bias on M2x is automatic.
Light Bulb Tester
https://www.antiqueradio.org/dimbulb.htm
Important Note – if building dim build tester per the schematic of antique radio.org and using a standard US outlet – ensure to remove the tab between outlets on the neutral (larger prong side) and leave the other side intact.
Some wisdom from Andrew T – paraphrased from posts beginning around #26
Light Bulb Tester
The Big Advantage of the bulb tester is that it automatically inserts the protection "current limiter", that is Mains voltage rated, to prevent catastrophic damage downstream. I always start with a low power bulb, I have just bought some 25W bulbs specifically for this use and compatible with the bulb holder I have. (my previous 25W bulbs need an e15 holder which I have not found yet.
Normally I start at 40W and progress through to 150W, if necessary, to get the circuit up to almost full operational voltage, checking the circuit at each stage for smoke, smell, voltages, currents, etc. But this progressive increase in bulb power is only required where the quiescent power draw brings on the limiting effect of the PTC inside the bulb envelope, i.e. it start to glow. If the bulb filament stays cold or near so, then the resistance in the primary circuit passes quiescent current safely to the transformer.
… Don't use a bulb tester when you are not using a mains transformer. The transformer and it's wiring is what the first line of checking that the bulb tester is useful for !!!!!!
Don't be "worried" about the bulb wattage being too low.
The bulb is rated for mains use.
It will not blow up no matter how badly you wire up your equipment.
The worst that can happen to the bulb is that it reaches the end of its life and fails. Plug in a new bulb.
I have mentioned a few times that having paralleled bulb sockets to allow adding extra bulbs would be useful.
The only danger is that you can "Start Up" with too high a wattage (or total wattage) and the current limit is set too high.
Start with a very low wattage and work your way up to a higher wattage.
A transformer alone, with no rectifier, can start up on a 15W candle bulb. It sometimes does not even flash. With a rectifier and no capacitors it will probably start with the same wattage. I have not tried that, the smallest bulb I have is 25W and that will start all lone transformers and all transformers with a bridge rectifier. 25W will also start up a small to medium transformer with some smoothing capacitance.
A large transformer with a lot of smoothing capacitance may need a 40W bulb to start up and for the filament to dim down to a very dim glow. The capacitor leakage and rectifier leakage is what creates the glow. This should lessen to almost off over many hours as the capacitor re-form.
See Papa’s post 1499 re: measuring the voltage across the 0.47 Ohm resistors for the bias current. Official M2 schematicNormally I start at 40W and progress through to 150W, if necessary, to get the circuit up to almost full operational voltage, checking the circuit at each stage for smoke, smell, voltages, currents, etc. But this progressive increase in bulb power is only required where the quiescent power draw brings on the limiting effect of the PTC inside the bulb envelope, i.e. it start to glow. If the bulb filament stays cold or near so, then the resistance in the primary circuit passes quiescent current safely to the transformer.
… Don't use a bulb tester when you are not using a mains transformer. The transformer and it's wiring is what the first line of checking that the bulb tester is useful for !!!!!!
Don't be "worried" about the bulb wattage being too low.
The bulb is rated for mains use.
It will not blow up no matter how badly you wire up your equipment.
The worst that can happen to the bulb is that it reaches the end of its life and fails. Plug in a new bulb.
I have mentioned a few times that having paralleled bulb sockets to allow adding extra bulbs would be useful.
The only danger is that you can "Start Up" with too high a wattage (or total wattage) and the current limit is set too high.
Start with a very low wattage and work your way up to a higher wattage.
A transformer alone, with no rectifier, can start up on a 15W candle bulb. It sometimes does not even flash. With a rectifier and no capacitors it will probably start with the same wattage. I have not tried that, the smallest bulb I have is 25W and that will start all lone transformers and all transformers with a bridge rectifier. 25W will also start up a small to medium transformer with some smoothing capacitance.
A large transformer with a lot of smoothing capacitance may need a 40W bulb to start up and for the filament to dim down to a very dim glow. The capacitor leakage and rectifier leakage is what creates the glow. This should lessen to almost off over many hours as the capacitor re-form.
DC Offset process - Recommended offset +- 30mV
Official M2 schematic
#1563 AC Noise - The diyAudio First Watt M2x
You can take a DMM and set it to AC at the highest resolution (most sensitive setting) and measure the output with shorted inputs. Your reading should be way below 1 mV. A good power amp should not show more than 0.2 mV of noise at the output. It is probably difficult to get much below 100 uV of noise.
Put the amp on a "Kill A Watt" $20 household wattmeter, it ought to draw 135-160 watts with input signal jacks shorted, if everything's assembled correctly.
“I don't know how everyone else does it but when I assemble an electrical device, I check for continuity to chassis on every module as I install them, before ground connections are made.It always looks like there will be no problem and loads of clearance to chassis parts but all it takes is a strand of wire to become dangerous. I also check between rails and outputs on amplifier boards or any high power transistor board with the meter set to diode check. Red lead on V+ rail, black on output, the red on output, black on - rail. If you have a voltage reading on either rail you likely have an output device or driver shorted or reversed. After the unit is assembled, check for continuity between mains, neutral and chassis. If you see any sign of trouble, find it before you power up. The problem won't fix itself. There should never be that surprise flash and smoke when you power up the first time. Continuity checks only take a couple minutes and can save lots of parts and/or your life. Really the only surprise you should run into is possible meltdown from oscillation, but that's what your bulb limiter is there for.
diyAudio Power Supply Circuit Board v3 illustrated build guide
POTENTIAL FUTURE MODIFICATIONS AND NOTES
Dual Mono or Monoblocks?
Dual Mono – Could fit in 5U case
- Official M2 schematic
- Official M2 schematic
- Official M2 schematic
- Post re: discussion re: how to stack the power transformers for dual mono - Official M2 schematic
Bypass Caps for C2 and C3 – Learn this.
- Official M2 schematic
Potential to bypass C2? Check schematics and ensure correct. Start here.
- Official M2 schematic
Motor Run Caps? See Elwood’s build and questions.
• Elwood’s question – Bottom of 1948
• Tungsten Audio Answer – Addition of some other additional capacitance - 1949
• ZM Answers based on design - 1951
Separate Power Supply
• Official M2 schematic
Papa’s note for <100Ohm output resistance not necessitating IPS. How to allow for bypass + daughter boards? All output resistance for all my components is <100Ohm. From Papa – “Keep in mind that any reasonably low output impedance preamp (say <100 ohms) will drive this circuit without need for the input buffers”.
@CubicIncher - put in a switch to go between the daughter boards. Very cool!
Notes for Mu Metal or other Edcor shielding in the future –
- Official M2 schematic
- I stand corrected, grounding the mu metal shield is not necessary. I am sure it does not hurt, so I am not going to take apart my M2 just to remove those grounding wires.
- Link to copper tape shielding on Edcor site - https://www.edcorusa.com/copper-shielding
- A source for a ready-made Edcor shield / box
It's a TEKO 3710. I got mine at Reichelt, Germany: at reichelt elektronik
Joshua - great thoughts on the standoffs and star washers used to connect the daughter boards to the main boards.
The diyAudio First Watt M2x
See Joshua’s offer for additional boards with connections.
See posts 2013 and following answers for how to adjust Ishikawa RV1. Just set it in the middle for now.
The diyAudio First Watt M2x
Add XLRs – See Aleph J thread.
Roll OpAmps in Tuscon
• DIP8 / SOIC - Watch the material type, some combinations of plating materials can be bad together (avoid gold/tin combinations)
o LCQT-SOIC8-8 Aries Electronics | Mouser
o 4808-3004-CP 3M Electronic Solutions Division | Mouser
• OpAmps
Worthy contenders might include the LT1115, OPA227, OPA134, OPA1611.
• Great question about opamp swapping for Tuscon
The diyAudio First Watt M2x
@Xrk971 posted about a possible new daughterboard. Mark Johnson has posted about requesting folks to audition new designs.
INTERESTING STUFF
Interesting perspective on resister comparisons / noise.
The diyAudio First Watt M2x
Great beginner’s article.
http://www.decdun.me.uk/gainclone_psu.html
Nelson Pass discussing modularity
The diyAudio First Watt M2x
Nifty idea for swapping in parts to check values – Pin Sockets
https://no.mouser.com/ProductDetail/Harwin/H3155-05?qs=/ha2pyFadugBFPtvz19zBl50O3n52lac0SLnjqncec0=
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Official M2 schematic
Paper on Capacitors
Download this pdf to your computer and save it somewhere that you can find it again.
Power Transformers and understanding
The diyAudio First Watt M2x
The diyAudio First Watt M2x
Mark’s summary of power transformer needs
The diyAudio First Watt M2x
Wire Choices
• RussellC - For wiring, I usually go to Apexjr, silver coated Teflon insulation, Mil spec....solid, stranded, whatever gauge and color.
• @6L6 – Basically any of the Mic cable (2-conductor plus shield) will work perfectly for the whammy –
o W2552 Mogami W2552 Microphone Cable (Black)
o W2549 Mogami W2549 Long Run Mic Cable (Blue)
o W2697. Mogami W2697 Miniature Balanced Mic Cable (By the Foot)
If you order from there, spend 5 bucks and do yourself a favor and get 20ft of 2381 as well, it's a small flexible coax that makes great wiring to/from RCA jacks and such. My absolute favorite for wiring RCAs to PCBs. Mogami W2381 Black Coaxial Cable, 50 Ohm (By the Foot)
• “I think ZM uses silver plated copper Mil-Spec 22 AWG M22759/11” – SissySit Building Tips #108
How to use the Mega328
https://www.amazon.com/Using-Yosoo-...=using+yosoo&qid=1558492174&s=gateway&sr=8-1
OTHERS’ BOMs
That is just superb information, hats off to you to collate and put them here. I think its a reference not just for any M2/M2X builders but could be for any kind of build
Hear, hear
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