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M-Patch 2 - Anyone successfully mod this thing? Monitor Controllers
Old 27th November 2009
  #1
Gear Nut
 

M-Patch 2 - Anyone successfully mod this thing?

I have the SM Pro Audio M-Patch 2 passive volume control and switch box. I know this gets some love round these parts. In theory, this is a great little piece of gear, totally fits a need for me--If it worked all the time. Right now, after on-again-off-again, I've completely lost the right channel in Aux path.

I've done extensive re-searches here and all around, and I read that people say this SHOULD be easy to mod, change out the crappy pots and switches to stepped attenuator, change switches, etc., yet I read NOTHING about anyone actually doing this. I brought this to a guy with some experience with electronics locally and he doesn't want to get into it, says he doesn't know what parts to get, how they'd fit in, seems like it'd be an extensive point-to-point, time-consuming mod.

I think there must be a way to fix/mod this thing effectively and without too much trouble. I've found stepped attenuators with Dale resistors pretty cheap on eBay, but I have no idea what exactly I'd need or whether/how they'd fit. Compared to anything else out there, I love the M-Patch 2's simplicity, compactness, and price.

Anyone have any pointers, advice, schematics, experience, parts you've used, shared misery, anything? I'm not ready to write it off yet and say I need a Central Station.

Thanks,
Perry
Old 28th November 2009
  #2
If you lost a channel completely, I'd suspect that there was a cold solder joint somewhere, and you should open the box up and reflow all the solder connections, particularly if they seem low on solder. Look especially at the connectors and switches. The main channels on that thing are passive, so it is unlikely that any parts are damaged.
Old 28th November 2009
  #3
I, too, would show interest in modding this unit, as I received mine about 2 weeks ago and am about 50 % happy with it. What sold me on it was the fact that a lot of people on here said they prefer it's sound over the more expensive Central Station. That, and the fact that it operates without power unless using the headphone amp. 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. My other complaint is that they advertise the ability to run three separate sources into the unit. Mains & two aux sources. GREAT!, I thought. I can finally hook up my computer's output and my turntable both into the monitor switching unit. Not really. The mini-jack sort of... overrides the RCA's. So, when I have my turntable playing (with my external Phono preamp cranked), it is virtually inaudible unless I un-plug the mini jack coming from the computer. Once unplugged, the turntable is very loud, as the signal is no longer blocked. This design is really annoying. I just want two aux inputs!!
Old 28th November 2009
  #4
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How about you take a picture of the inside and we continue from there?
Old 29th November 2009
  #5
ill try to get pics up tonight!
Old 29th November 2009
  #6
Pictures!!

I just popped the top off to snap these, let me know if anyone needs better pics / info off of anything.
Attached Thumbnails
M-Patch 2 - Anyone successfully mod this thing?-imgp2978.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2981.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2977.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2982.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2983.jpg  

M-Patch 2 - Anyone successfully mod this thing?-imgp2985.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2986.jpg   M-Patch 2 - Anyone successfully mod this thing?-imgp2987.jpg  
Old 29th November 2009
  #7
Gear Nut
 

Thanks silence. I saw the post from Tomer1 and was planning to do this and didn't have time yet. I am waaaaay inexperienced with electronics, but having said that, I've been doing some research. Below is a pic of what I've been looking at on eBay wondering about whether it'd fit and whether the existing circuits in the Mpatch2 would work with it. It's a stepped attenuator with Dale resistors. There are others, no doubt better quality and for much more cash, made by Goldpoint and others, but might an inexpensive solution like this work?

Here's the link to the attenuator on eBay Attenuator 24 Step 10K 'A' Dale resistor Stereo NEW - eBay (item 360138248175 end time Dec-06-09 10:00:08 PST)
Attached Thumbnails
M-Patch 2 - Anyone successfully mod this thing?-stepped-attenuator.jpg  
Old 29th November 2009
  #8
Gear Nut
 

Quote:
Originally Posted by aclarson View Post
If you lost a channel completely, I'd suspect that there was a cold solder joint somewhere, and you should open the box up and reflow all the solder connections, particularly if they seem low on solder. Look especially at the connectors and switches. The main channels on that thing are passive, so it is unlikely that any parts are damaged.
Thanks for the reply. Maybe you're right, and I will look at this. Unfortunately, my soldering skills are...underdeveloped. Also, tho, I'm really interested in the larger question of making this unit much better. But, yeah, good advice.
Old 30th November 2009
  #9
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The only one I can see in the pictures is the volume 100k knob (nice of them to label it). You'll need a 100k replacement if desired:

Attenuator 24 Step 100K 'A' Dale resistor Stereo NEW - eBay (item 330344958120 end time Dec-12-09 10:13:28 PST)

Could also be a tight fit with that electrolytic behind it.

The thing I find weird about the m patch is how Silence says you can't mute the speakers and still have the headphones. Can anyone confirm this is normal function? Or is it possibly a dysfunction in his unit?

Also, thanks for the link to those stepped attens - Pricey, but could be fun to try out in more than a few applications.
Old 30th November 2009
  #10
Quote:
Originally Posted by mobius.media View Post
The only one I can see in the pictures is the volume 100k knob (nice of them to label it). You'll need a 100k replacement if desired:

Attenuator 24 Step 100K 'A' Dale resistor Stereo NEW - eBay (item 330344958120 end time Dec-12-09 10:13:28 PST)

Could also be a tight fit with that electrolytic behind it.

The thing I find weird about the m patch is how Silence says you can't mute the speakers and still have the headphones. Can anyone confirm this is normal function? Or is it possibly a dysfunction in his unit?

Also, thanks for the link to those stepped attens - Pricey, but could be fun to try out in more than a few applications.
Good call on the Mute switch. I assumed it would mute all output, including the phones. Wrong. It only mutes the speaker outputs, so you can crank the input's volume as high as you want (with mute switch engaged), then use the headphone volume pot to attenuate that signal. This little box just became much more functional to me Still lookn' for mods, though!! It looks like there's a couple op-apms in there (probably for the headphone circuit) that could be easily upgraded. One got caught in my pictures but the other was too difficult to see. If anyone's interested in doing further op-amp research I can pull the top back off mine & post some numbers.
Old 30th November 2009
  #11
Lives for gear
 

I'd be curious to see what opamps it uses. Also, if there's enough space and it's not surface mount, you may even be able to try some discrete opamps in there.

Looking at it so far, I imagine the most difficult part would be assembly/disassembly, but everything's nicely wired with sockets so even that shouldn't be too hard.

Regarding that 100k pot, I just looked at the unit layout and it seems that's the headphone pot, right? So no real point modding that. A picture of the main volume or aux volume pots would be more helpful since that's what you'll want to upgrade.
Old 30th November 2009
  #12
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headwerkn's Avatar
I've had my MPatch2 for nearly 6 months now and it is still rock solid reliable. Granted I'm not using the Aux input much (lately just to run BeBot from my iPhone through my monitors!) but everything else is still A-OK.

Being a simple, passive circuit I would have thought troubleshooting and modification would have been dead simple. If there was one thing I would change it would be the knobs, with some nice heavy machined aluminium ones.
Old 30th November 2009
  #13
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steveschizoid's Avatar
The mute switch on mine doesn't reliably mute the speaker outputs; I have to push it in and out several times before it works. It looks like you pretty much have to disassemble the entire thing and remove the circuit board to get to the switch, so I haven't even tried to fix it yet. Am I correct in assuming that it needs a new switch? If so, any ideas as to exactly what switch I'd need to obtain?
Old 30th November 2009
  #14
Lives for gear
 

Dunno bout the mute switch. Would depend on the exact size/brand they used if you want it to fit. Would need pics at least to start. Otherwise any DPST should work.

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.
Old 30th November 2009
  #15
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Blinddot's Avatar
 

Watching these pics I feel glad I bought m-patch version 1, no active electronics in the box, no caps, no resistors, no coils, just switches and 2 pots one per input. I did a mod on it, I changed the cheap XLRs with neutrik ones, no real need to mod it, at least until the pot makes noise. I acctually find the nano patch much cleaner that m-patch 2, if you really need 2 outputs (like I do) try to find version 1 then.

If you want something better (perfect L/R tracking at low levels, constant impedance, lower selfnoise, longer lasting) just go for stepped attenuators, goldpoint for me are the best ones (non-DIY), the pic speaks for itself (check the guts)

Goldpoint SA2X Level Controls / Passive Preamps

you have a DIY reference in their website as well, so you'll be able to learn some basic electronics related to signal attenuation.

Reference Data for DIYers

if you are into DIY I would also have a look at DACT website

DACT - Danish Audio ConnecT



Old 30th November 2009
  #16
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Blinddot, if I'm not mistaken, the active electronics are probably for the headphone amp. According to the copy here (SM Pro Audio M-Patch 2) that seems to be the case - it's still perfectly passive for main volume monitoring.

(Which raises the point that since the opamps are just for the headphone amp, there's probably no real point in upgrading those at all. I'd stick to just upgrading the big main/aux pots and leave it at that.)

The Goldpoint looks nice, but you'll need a separate headphone amp and then have to juggle a multi-unit setup to get it right if you use headphones.

Switching the main two pots on the SM to stepped Dale should give the same performance with more functionality.
Old 30th November 2009
  #17
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lectric's Avatar
 

I have the same problem with a a designs atty. I d´ont like the stereo work at low levels. I want to change the stereo pot for a step by step pot hig end quality. Do you know what impedance is correct??? 10k or 100k?
Old 30th November 2009
  #18
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White Falcon's Avatar
Quote:
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.
On mine (and probably yours) the mute button kills the monitors, but leave the headphone amp unaffected. So, hit mute and turn the big main volume knob up and you should not hear anything from your monitors, and you should have a solid signal to and from your headphones.

thumbsup
Old 30th November 2009
  #19
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The caps and OPamp are used for the headphone amp.

Regarding the electro cap which is behind the 100k Pot ,
It can be twisted to provide room for the steped switch. thumbsup
Old 30th November 2009
  #20
Yeah, it almost seems like there's more room for improvement in the headphone amp than anywhere else... The "pots" for the Aux & Stereo volume knobs are the green rectangle things in the 1st & 3rd pictures. They say A5k on them. Not sure if they are easily upgradable or not.... I may pull my unit apart further tonight to check out how those pots are pinned & post up later.
Old 1st December 2009
  #21
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Quote:
Originally Posted by silence2-38554 View Post
They say A5k on them. Not sure if they are easily upgradable or not.... I may pull my unit apart further tonight to check out how those pots are pinned & post up later.

Ah, so they're 5k. Unfortunate since I can't seem to find any cheap 5k stepped attens.

The only finished ones I see are from Goldpoint and cost quite a bit:
Prices

Also doesn't look like there's much room up there with the wire sockets so close...

If it could fit, you could always DIY a stepped atten like from one of these kits with custom 5k resistor values, but then the soldering is getting intense:

Kikitronic -- DIY Audio Kits: Attenuator for volume control
DIY kit Dale 23 Step Attenuator for Volume Control 100k - eBay
Old 1st December 2009
  #22
OUCH! In order to maintain the dual output option of the M-Patch2, you'd have to go with the quad from Goldpoint which is 250.... Bummer.
Old 1st December 2009
  #23
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Quote:
OUCH! In order to maintain the dual output option of the M-Patch2
I was under the impression only one speaker can be choosen by the selector switch,
What u are saying is that the pot is controling two sets of outputs and the monitor selector is made out of two on/off switchs?

Even if so,
I would lose one of the outputs and if you do want to use two monitors place an A/B switch after the Mpatch 2.
Old 1st December 2009
  #24
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You can also DIY one from a kit I linked for $35 if you're brave enough.

If so, Goldpoint has all the correct 5k resistance values here:
Mini-V Parts Lists
Old 2nd December 2009
  #25
Gear Addict
 

Quote:
Originally Posted by silence2-38554 View Post
I, too, would show interest in modding this unit, as I received mine about 2 weeks ago and am about 50 % happy with it. What sold me on it was the fact that a lot of people on here said they prefer it's sound over the more expensive Central Station. T
Nice thread. I have a M-patch 2 also.

silence2 - I have not come across the above statement on GS?? can anyone vouce?

I've been drooling on the Goldpoint for years, but no headphones. At that price point, might as well go with the SPL 2 control, whihc has a attenutator not a pot. SPL has a seasonal discount per their email.


T
Old 2nd December 2009
  #26
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Blinddot's Avatar
 

Quote:
Originally Posted by mobius.media View Post
Blinddot, if I'm not mistaken, the active electronics are probably for the headphone amp. According to the copy here (SM Pro Audio M-Patch 2) that seems to be the case - it's still perfectly passive for main volume monitoring.
OK maybe it is "geeky" me, but I tend to keep passive signalpaths very clean, I tend to think their fairly delicate, very sensitive even to cable capacity (roll off on hi frequency on long runs) , the hp amp, its power cables and ground.. I just like to keep that stuff out of the chassis, even if it is a very high impedance buffer I tend to think it will act over the signal and at least lower down its level a little bit (even if is high impedance buffer, some current has to flow from my signal to the buffer input), and also, to induce noise. I just prefer to keep my control-room buss cleaner. In my case I don't need a headphone output, I've got one on the DA converter.

Assuming you don't even power the HP amp, are you sure that the only components in the signal path are the pot and the output switch? (like in version 1). Passive signal path I'm sure it is, but a cap, a resistor or a coil are passive but I wouldnt like them on my signal path or close to it. To be honest I don't know the schematics, but try to understand me when I prefer the old design, just in case.

Old 2nd December 2009
  #27
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headwerkn's Avatar
Quote:
Originally Posted by Tomer1 View Post
I was under the impression only one speaker can be choosen by the selector switch
No, you can use either or both of the speaker outputs simultaneously. You can only select one input at a time though (ie. no summing).

The only active/powered electronics in the box are for the headphone amp and the status LEDs... pull the power adapter and the attenuation and switching still works.
Old 2nd December 2009
  #28
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Quote:
The only active/powered electronics in the box are for the headphone amp and the status LEDs... pull the power adapter and the attenuation and switching still works
Yes Im aware of that,
If it wasnt the case they wouldnt have called it a passive attenuator
Old 2nd December 2009
  #29
So, I found a thread from '07that had pictures and it appears quite a few things have changed in the M-Patch 2. The pots and even the silicon boards are different. t looks like the older unit was assembled better, too (cable clips glued together). The older pots appear to be higher quality, too......
Old 2nd December 2009
  #30
pictures
Attached Thumbnails
M-Patch 2 - Anyone successfully mod this thing?-mpatch2_1.jpg   M-Patch 2 - Anyone successfully mod this thing?-mpatch2_2.jpg  
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