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M-Patch 2 - Anyone successfully mod this thing? Monitor Controllers
Old 3rd December 2009
Gear Head

Would be also interested in a mod to improve the attenuator and perhaps clean up the mute circuit...

I've had my m-patch2 for slightly less than half a year...its worked perfectly until recently where I didn't use it for 2-3 weeks (had been using it everyday until then).

Levels became unbalanced often at moderate levels...we're talking around -30 to -20dB attenuation (previously very seldom), had to use the trick of giving the knob a nice big spin to the max to even it out.

And just now my left channel got attenuated quite noticeably...even the knob trick didn't work. After messing around I discovered that the mute switch/circuit was the problem - after pressing/depressing the mute switch it became ok

The weirdest thing is that I never use the mute switch as I don't like the crackling sound it produces when muting - I've always just switched my input to Aux (which isn't connected) or just simply rolled down the volume to -infinity.

Maybe I just bought one with a lame mute switch, idk.
Old 29th September 2010
Gear Head

bump for one simple question

if i got this expensive 5k stepped atten from goldpoint, is it easy and simple to swap the pot?, i mean is it as simple as "take off the old one, and solder the new one", and no need to modification the board or anything at all?

Old 17th January 2011
Gear Head

just a tiny mod with my m patch 2 :

1. get rid those crappy mute switch that very scratchy, and bypass the connection (WARNING: the default position when the switch lifted is in MUTE position, so bypass it if you dont have any switch replacement)

2. ordering this pot, to replace those unbalanced-level-pot
Old 27th January 2011
Gear Head

finishing replacing the main pot with ladder attenuator pot (10k)

next mod :
- buying another stereo ladder, to split the output
- changing all cheap 8pdt switch with schadow brand pot
- build a new case (acrlyic) :D
Attached Thumbnails
M-Patch 2 - Anyone successfully mod this thing?-photo0382.jpg   M-Patch 2 - Anyone successfully mod this thing?-photo0383.jpg  
Old 2nd June 2011
Gear Nut
supafuzz's Avatar

5k or 10K

Originally Posted by blinkerss View Post
finishing replacing the main pot with ladder attenuator pot (10k)

next mod :
- buying another stereo ladder, to split the output
- changing all cheap 8pdt switch with schadow brand pot
- build a new case (acrlyic) :D
the volume control is a 5k pot why would you replace it with a 10K?
Old 3rd June 2011
Lives for gear
Blinddot's Avatar

It seems the pot value should match the input impedance value of your power amp. At least that's what goldpoint advices

Detailed Information

Old 3rd June 2011
Lives for gear
BradM's Avatar
Originally Posted by View Post
Also, I just saw the opamps in the pic - good - they're through-hole. Much easier than surface mount. Unfortunately they're a 1x8 pin layout which is weird. But otherwise, they're just regular bipolar dual opamps so anything that matches that pin layout should work.

Not sure what comes that way.
The op amps are SIL...NJR makes their version of the 5532 in that package. I can't remember the part...maybe NJM5532? That's the best you are going to do. You will have to find a distributor that will go out of their way to track those down for you though. Good luck. I'd get this instead which will allow you to put whatever DIP opamp on there you want:

SO8/DIP8 to SIL Adapter (p/n 060301)

My favorite is the LME49860.

Old 30th June 2011
Lives for gear
Quint's Avatar
Originally Posted by blinkerss View Post
finishing replacing the main pot with ladder attenuator pot (10k)

next mod :
- buying another stereo ladder, to split the output
- changing all cheap 8pdt switch with schadow brand pot
- build a new case (acrlyic) :D
So what specific brand/model of attenuator did you end up using on your mod? Did you have to do anything special or was it simply a matter of swapping one out for the other?
Old 30th June 2011
Gear Nut
supafuzz's Avatar

Originally Posted by Quint View Post
So what specific brand/model of attenuator did you end up using on your mod? Did you have to do anything special or was it simply a matter of swapping one out for the other?
yes please tell us..I like this box but it's frustrating at lower volumes when the stereo picture collapses
Old 1st January 2012
Here for the gear
yoshitoshi's Avatar

Hi guys! I have also this piece of gear and I'd like to improve some parts. Mainly the sound of phone preamp! Has anyone already tried to change those original opamps (NJM4558L and NJM4556AL)?? Which ones should i use for the best sound quality? Thanks for reply
Old 2nd January 2012
Lives for gear


1. What impedance headphones are you connecting to the headphone amp??

I would guess prolly a studio-type load of typically somewhere between 150 and 750 ohms. That would lead to pretty quiet monitoring through the headphone amp.
although my 600 ohm AKGs do just fine.

2.My MPatch 2 works daily and has done for almost 2 years no make that just over 2 years. In that time I have had to replace a faulty headphone jack socket under warranty early on, otherwise all works perfectly.

3. I run two input streams and two output streams.

Aux has the main outs from the music computer and Stereo has the main out from a freestanding hard disk recorder.

The two outputs go to two pairs of monitors, but all of these can be mix and matched as required, plus of course I can always stick my mp3 player in that crappy little 3.5mm jack.

A friend has a Mackie Big Knob that has crapped out on him time and time again.
He now has the Nanopatch which does all he needs and was even cheaper.

Last edited by ivansc; 3rd January 2012 at 08:11 AM.. Reason: tidying up typing
Old 3rd January 2012
Lives for gear
sdelsolray's Avatar

Originally Posted by silence2-38554 View Post
What I was disappointed in is the way that the headphone system is designed. With the M-Patch2 plugged in & the headphone volume all the way up, you have to have the source's volume knob also turned up about 1/4 of the way to feed the headphone signal. So no matter what, if you're trying to head your phones at a decent volume, you're going to hear a bit of your monitors playing in the background as well. That is my main complaint.
Use the Mute switch while using headphones. It turns off the monitors and does not turn off the headphones.
Old 8th November 2012
Gear Head

I have the Mpatch2 and the potentiometer is dead. There is no accurate stereo-image any more...

My question is: I now want to use the Mpatch2 as a simple switcher (shortcut the poti) I can´t really figure out how the circuit is working. There are (as also seen on some pictures posted by other users) four lines going to the potentiometer, but how is it going from there? How can i simply disconnect the poti, and who has a link for me for further information about circuits like this one...

Best regards,

Old 2nd December 2013
Here for the gear

to: blinkerss
Please Tell Me!
How install stereo potentiometer instead quad!
How did you do it???

I make more combination No Sound or mono.

Please draw a diagram.

Attached Thumbnails
M-Patch 2 - Anyone successfully mod this thing?-patch-2.jpg  
Old 24th May 2014
Here for the gear

"How install stereo potentiometer instead quad!"

no one knows?
Old 24th May 2014
Gear Head

SM Pro Audio customer service

I had some similar issues with my M-Patch 2: uneven L/R main channel volume, instability of image (due to uneven volume), inability to completely mute both channels, etc. I have had this unit apart 6 times. I finally cleaned all pots with Caig treatment, and there was some improvement.

BUT, here is the worst of it. I contacted SM Audio, notifying them of the problems. They assured me these issues were not chronic, in spite of many threads to the contrary (with many happy customers as well), and chastised me for suggesting people were having problems.

- It took 3 weeks for them to answer the first e-mail
(Danny assured me he would act on this)

- It took another 3 weeks for him to say he would send me a new main switch
(and only after I recontacted him)

- three weeks later I notified him I received no switch

- it took him a week to contact me and assure me he would check on the switch

It has now been over 3 1/2 months, with no switch sent, a solution they suggested

This kind of customer service is the bane of audio companies. Just be smart enough to interact with your customers on an honest, direct level.
Old 14th June 2018
Gear Guru

I have replaced a pot and a switch on separate occasions. SMPRO Germany sent them free of charge. That company are gone now and JBL are not providing support. I suspect the design is unchanged though. Does anyone have a schematic? I need to find a generic, higher quality, switch. Is it 6PDT or what?

Old 18th June 2018
Gear Nut

Push/Push Switch Refurb

@ Dan Dan (and others) - If the switches shown in Plazma's pic of 12/02/2013 are indicative of all Rev's of this design, I would say it's a 4P2T, rather than a 6P2T, as you were wondering. If I'm remembering correctly, with "break-before-make" switches of this type the way to assess this is the number of visible contacts per side (the two rows of contacts visible on the brownish colored plate at the top make up 24 total, with 12 per side) divided by three gives you the number of poles. Push/Push switches similar to that one were used by Symetrix back in the 90's when I worked there.

A simple cleaning/re-lubing may be all that's required rather than a total replacement (with associated risk of damage to the PCB). The one's we got at Symetrix were made by Shadow, if I recall correctly. They can be lubed with a non-conductive silicone grease (which counter-intuitively quiets them up, making for less "scratchy" transitions). Partial disassembly is required but not too difficult:

1. Using a small "hook" tool (like a dental pick, or similar) or small pair of needle-nose pliers, pull the chrome-colored latch/catch pin up slightly to remove it from its slot at the front of the switch plunger (white plastic - what the switch cap is attached to), and gently pivot it off to one side or the other. Don't pull it up with enough force to remove it completely so it doesn't get lost. With this catch pin disengaged from the plunger the switch becomes a "momentary-action" switch (should you ever need to mod one to do this function).

2. Using the "hook" tool again (or a small straight-slot screwdriver), there's a small plastic tab-like protrusion at the top front of the body of the switch (the brownish plate you see which has the tops of the solder leads coming out of it) that has a prong on it that engages with a slot in the white plunger, and prevents it from backing all the way out of the body assembly. Keep a finger on the switch cap to prevent it from shooting across the room (the plunger is spring loaded to allow it to return to its most outward of travel positions), and gently lift the moving edge of this prong just enough for the plunger to move toward you and allow the plunger to become free of the body. A light tug should completely free it - try not to force it, as there are contacts and contact springs attached to the plunger which you mustn't lose, as you'll have to buy a new switch at that point.

3. A smallish dab of silicone grease on each contact "throw" should do the trick, then reinsert the plunger into the switch body. If inserted far enough into the body, the plunger should be automatically trapped into position by the prong mentioned in step two. Exercise the switch vigorously for a few seconds (while testing I would often listen to the switch with signal passing through to observe the proper reduction of "contact bounce" - the true cause of "scratchy" switches in most cases).

4. Re-insert the catch/latch pin into its proper channel in the plunger (you might have to move and hold the switch into a position that allows for the pin to "find its home" easily).

Often the factory lube migrates away from the contact "throw" with time, or a little bit of dust or corrosion builds up which contributes to "contact bounce". In the case of Symetrix analog units I was testing during my employment there, we would actually wash the wave-soldered motherboards to remove flux residue, then have to deal with the washed-out factory lube issue in a manner as described above.

Anyway, hope that's helpful.
Old 18th June 2018
Gear Nut

Added note: upon magnified inspection of Plazma's photo above, it appears that unlike the ones produced by Shadow, these do not have a locking prong as I mentioned in step 2. Therefore the catch/latch pin may be the only thing holding the plunger in place against the resistance of the spring. Keep your finger on or partially engage the switch to enable swinging the catch pin to the side without the "rocket launcher" effect sending the plunger (and its smaller springs and contacts) across the room.
Old 18th June 2018
Gear Guru

I removed one. It is 8PDT. A friend at DACS found a source of a much better looking one. Pushbutton Switches | Switches | DigiKey

Old 19th June 2018
Gear Nut

@ DanDan - Of course you are correct, my response was made too late in the evening for my one working brain cell to completely think it through (memory failed me due to it's having been 24+ years since my working at Symetrix). Yes, the formula should read: count the total number of solder pins and divide by three. Each row (side) should have a total pin count that is divisible by three (the pole, or input pin is the middle of a set of three contacts, the 2 throw pins are adjacent to either side) for it to be a DT (2T) type. Since in this case the row pin count is 12 per row, divided by 3 = 4 poles per row X 2 rows = 8 poles. Sorry, my bad!

Still, did your switch completely fail or just get scratchy? Actually these are pretty simple switches-other than losing the individual spring tension on the plunger contacts, or (if designed with individual coil springs for every contact) having a spring pop out of position, I'd be surprised by an absolute, unserviceable failure.

The ones you linked to should work fine AFAIK, as C&K has had a pretty good reputation for decades. Just to be sure, measure the pin center-to-center spacing and compare to the C&K spec sheet, although those switch types are likely to have had a standardized pin spacing since their type has been in production for over 30 years. Best of luck.
Old 20th June 2018
Gear Guru
Failure breeds success

Thanks brain, you are very helpful. I would buy another MPATCH in a heartbeat but, the switches behave really badly, after only a few months...... they look really really cheap also. Also these M Patches seem to have spawned a host of imitating products now. But despite poor switches, I have been very happy with this little box for quite a few years. It is a pretty high end audio path, and this little fella does not let it down. Except for the switches.
I have changed or bypassed three. The construction is very good in there, the pots have a nice feel and don't scratch at all, or unbalance the stereo.
So I am thinking 15 bucks to get this going again, with three decent switches....
To be honest this SMPRO was always meant to be temporary. But it works to the extent that I have stalled building this project....... Should be a nice Winter night thing.
Old 20th June 2018
Gear Nut

After all the help you've given to others on these forums (including myself), you're very, very welcome!
I may entertain the notion myself of a DIY monitor controller using stepped attenuators and other switching functions, but I have yet to flesh out all the details needed. My project may entail accommodations for 4 subs, two mains, two to four mini's/alternates, two satellite tweeters, three sources (one test/analysis rig, one primary DAW or host and a "guest" or alternate set of sources), and associated DSP crossovers, power amps, etc.

If I might ask, I have been considering getting one of the M-Patch 2's to help control the analysis rig by itself, and was wondering - do the output selector switches act as an Exclusive OR (like old-style car radio buttons), or as an AND-type function? In other words can you select: A, B, and A+B? Thanks for your help.
Old 20th June 2018
Gear Guru
Winter Nights

Forgot to include the SoundSkulptor Link.
This might actually work for you....
Sound Skulptor: MC624 Monitor Controller - Kit, Other studio devices, MC624

The MPATCH does A+B.

Old 20th June 2018
Gear Nut

Wow, that MC-624 seems to be a very well thought out piece! Quite the winter evening(s) project, indeed.

Thanks for the reply about the M-Patch outputs being an AND-type. That clinches it, I'm getting one, and will probably order the C&K switches you linked, since the stock ones are "iffy". Thanks again.
Old 20th June 2018
Gear Nut

Actually, I should have said a classic OR, not AND, nor XOR. Logic escaped me
Old 20th June 2018
Gear Guru

I has been around for a while. JBL seem to have recognised the quality and it is now a JBL product. No idea if they have revised it. It would be very easy to find a better headphone chip. The CK switches are about £5 each. The SMPR ones I would say 50c. I found the name hidden underneath....BUBUJING.
I will let you know in a week or two if the CK switches fit!

Old 5th August 2018
Gear Nut

@ Dan Dan - Did the switches get delivered to you, and do they fit? My JBL version of the M-Patch 2 just arrived a couple of days ago, and I just cracked the lid. The PCB's all have JBL Silk Screened on them, and the switches in question have a different look from the photos posted earlier in this thread, closer to the Shadow switches Symetrix used (same mechanism that I described above, with the catch-pin and return spring).

They have a different enough appearance from Plazma's photo that they my not be from the "Bubujing" source yours are (haven't verified mine with a switch removal yet) - mine have a lighter grey body, and a transparent top (you can see the off-white Plunger of the switch through the top).

An interesting note to anyone with earlier Symetrix gear, these switches don't have a hole-punched extension to the solder pins that extends above the switch body like the Shadow switches (handy for grabbing securely the solder pins with a test lead or scope probe), although they might have been customized/trimmed off at the factory. Though I haven't taken a micrometer to the pins yet, the Center-to-Center spacing appears to be approx. 8.5mm (0.33"), as measured by a tape measure flexed into position to have a look.

The pots appear to be Delta brand, and the op-amps are NRC 4558 8-pin SIP's. The Motherboard (Main PCB) appears to be double-sided, although the Daughter boards for the top two output jacks, and Volume knobs are single-sided. Curiously, the Motherboard has art and trace layout for an unpopulated three-terminal TO-220 package (although without a B.O.M. part number printed near it), probably for a +15 VDC voltage regulator to drive the headphone amp and LED's. The larger electrolytic caps are Samwei brand, and I believe the PCB's are populated with 1/4 Watt 1% metal-film resistors. Although there may be no local chip supply decoupling caps (usually 0.1 mFd ceramics), I believe I detect a couple of 27pF feedback-compensation caps for the headphone driving chip, which in my experience with the Symetrix designs utilizing the the 4558's successor (the 4560 op amp) is a conservative quantity of capacitance that will be fairly stable (resisting oscillation under load) yet not overly damped in the high frequencies.

Any way, those are my observations at the moment, let me know about those C&K switches, please.
Old 5th August 2018
Gear Guru

Everything went wrong. I have been using x3.5 Ready Reader Glasses when soldering. So I treated my self to an Optivisor with 3.5 lenses. It has a focal length of 4 inches.......
I ordered from There is no such thing. My parts came from America, which means an extra 20% VAT charge. Luckily there was no Customs Charge.
The switches looks way better than the original troublesome ones. I popped one in. The legs are shorter! The originals had very long legs to accommodate LEDs underneath on the front panel.
I was close to weeping now.
With the help of a friend I tried to modify the front panel. Ultimately I get rid of the printed front panel, cut all the LEDs, headphone socket, volume, Mono switch.
I didn't ever use any of that anyway. My friend used an angle grinder to cater for the lower switches. It all looks pretty Mad Max now, but works perfectly. This will tide me over until I build my Mon Controller kit from SoundSkulptor. That is if the Sun ever stops shining here! I am not kidding, best summer in memory.

Perhaps the best headphone amp I have heard is my DACS. It uses JRC 45800 chips.

EDIT, when searching for a Monitor Controller I found plenty that will clip at say 22dBU. ProTools HDX192 is way hotter than that. As is an 1176, or Massenburg Preamps.


Last edited by DanDan; 5th August 2018 at 10:28 PM..
Old 6th August 2018
Gear Nut

Sorry for your troubles, Dan Dan. Man that's a lot of hassle just to replace the switches - were the C&K's like 6mm shorter, or so? I take it the pin center-to-center spacing was OK anyway. However hacked it now looks, as long as it's working for you, and doesn't distract you too much by being all Frankenstein-ish, then it'll suffice 'till you build a better one.

So, how hot do you figure the Pro Tools HDX192 system runs- like +26dBU? I've never wired up an 1176 or Massenburg pre's (too much above my pay grade at the moment), but unless their dumping so much voltage that a passive controller's resistors would fry (maybe 1/8th Watt would be ill-advised) I'd think there wouldn't be much distortion produced by a passive controller, unless the load resistance was too low, in which case the pre-amp's output devices could be loaded to distortion.
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