[johnjen]

  It's the smps in the 3+ usb for sure that's adding the veil = noise. And yes, you can use 5v with the 3+ usb as I have found out.
I also just added another 3+ usb to the chain and modded it with lps.
 
If I can go to the next upcoming meet, (not sure yet if I could) then you can listen to the rig and see if you hear any diffrence.

I'm also not sure if I'll make the bottlehead meet, or not.
 
And today I yanked the SMPS out of my 3+usb and powered it up (6.255Vdc) with my dual LPS.
It failed to latch on the aes data stream, and would loose its lock on a SPDIF feed from my 3+ as well.
 
So I'm investigating getting it repaired, which means sending it back to Germany.
I bought it used so there is no warranty.
 
But before I send it in I'll try lowering the voltage down from 6.2 to 5.2Vdc to see if that fixes its problem.
I sure hope so because it's not gunna be cheap to get it fixed, what with shipping, let alone the actual repair costs.
 
One of the prerequisites of DIY is to take responsibility when things go sideways.
 
And I'm thankfull this sort of thing is rare.
 
JJ

 

[Muziqboy]

  I'm also not sure if I'll make the bottlehead meet, or not.
 
And today I yanked the SMPS out of my 3+usb and powered it up (6.255Vdc) with my dual LPS.
It failed to latch on the aes data stream, and would loose its lock on a SPDIF feed from my 3+ as well.
 
So I'm investigating getting it repaired, which means sending it back to Germany.
I bought it used so there is no warranty.
 
But before I send it in I'll try lowering the voltage down from 6.2 to 5.2Vdc to see if that fixes its problem.
I sure hope so because it's not gunna be cheap to get it fixed, what with shipping, let alone the actual repair costs.
 
One of the prerequisites of DIY is to take responsibility when things go sideways.
 
And I'm thankfull this sort of thing is rare.
 
JJ

 
I was experiencing the same thing with not locking on the input signal. I installed a 2.1mm female jack as I did on the non-usb Mutec but for some reason, I was getting flickering of the blue led lock until I found a certain 2.1mm male plug out of the several that I have on hand that finally worked and I got a stable lock on the input signal. It was really weird that this thing only happens with both the usb version that I have and noticed also that happened once I removed the smps board out. It did not happened before when the smps was still in there.
 
As an experiment, before you send it back try to solder the wires coming out of your LPS directly to the board on the Mutec usb and see if that will give you a solid lock on the AES input signal. I think hopefully that will solve the issue.

 

[johnjen]

Thanks for the insights.
And that you had the same flickering leds that I see, and the lack of lock on, gives me a few hints.
And I'll use the scope to see if I can see anything weird as well.
 
And yeah it was working fine on the SMPS, well except for the SQ.
I kept waiting for the magic to happen and it just didn't.
So I figured the LPS upgrade ought to do the trick…
 
But I'd already hardwired it directly to the mainboard, as is my usual routine.
 
But that you saw the same behavior as what I'm seeing, and your solution was to improve the connection from the LPS to the mainboard (for more current delivery capability) gives me a few clues to pursue.  :thumb
 
JJ 

 

[Muziqboy]

I was just thinking that we might have disturbed some grounding scheme or something when we removed the SMPS.
Kinda like the grounding that's important on the Rednets.
just my 2c.

 

[johnjen]

Yeah I thought the same and restored the grounding scheme to stock but it didn't make any difference.
I even thought it may have been a ground loop problem, but no matter what I tried the problem persists.
 
The thing is the 3+ (non usb version) has no problem with the LPS mod, it's only the 3+usb that can't latch onto the incoming signal.
Perhaps its a firmware issue.
 
I'll start fussing with different supply voltages later today and see what happens.
 
I do find it odd that the 3+usb has 6.x Vdc feeding it where as the 3+ uses 5Vdc.
 
JJ

 

[mourip]

 
I do find it odd that the 3+usb has 6.x Vdc feeding it where as the 3+ uses 5Vdc.
 
JJ

 
I wonder if it is the USB board that needs it? I have not replaced my SMPS yet but I did pull the USB board.

 

[Muziqboy]

Yeah I thought the same and restored the grounding scheme to stock but it didn't make any difference.
I even thought it may have been a ground loop problem, but no matter what I tried the problem persists.

The thing is the 3+ (non usb version) has no problem with the LPS mod, it's only the 3+usb that can't latch onto the incoming signal.
Perhaps its a firmware issue.

I'll start fussing with different supply voltages later today and see what happens.

I do find it odd that the 3+usb has 6.x Vdc feeding it where as the 3+ uses 5Vdc.

JJ

The thing is, if you just solder wires to the + and - of the Mutec usb and run a LPS to it without removing the SMPS, it locks on the incoming AES or SPDif signal with no problem at all.

So a word of caution for folks wanting to do the LPS mod on the Mutec usb. Just solder wires to the power pins on the Mutec usb and do not remove the SMPS until JJ can figure out what's going on.

 

[Superdad]

The thing is, if you just solder wires to the + and - of the Mutec usb and run a LPS to it without removing the SMPS, it locks on the incoming AES or SPDif signal with no problem at all.

So a word of caution for folks wanting to do the LPS mod on the Mutec usb. Just solder wires to the power pins on the Mutec usb and do not remove the SMPS until JJ can figure out what's going on.

Per Mutec's CEO, leaving the stock SMPS connected is NOT advisable:
 
 

"Yes, the MC-3+USB does not need 1.2A, so from that all good. But using a linear power supply you must remove the internal power supply of the MC-3+USB. That means you must remove the whole PCB out of the case and de-solder the power supply from that. Don’t simply connect the two cables of the linear power supply to the pins of the MC-3+USB’s SPS. That would let the secondary stage of the SPS run as well! Please also consider that when doing this modification, you are losing the warranty claim.
 

I have attached a PDF showing the PCB print of the mainboard. The two DC outputs of the internal SPS are marked with “+” and “-“. At these points you must connect the cable of your linear power supply.

Please report how your MC-3+USB performs after the modification has been carried out.

Good luck!"

Regards, Chris.
Dipl.-Ing. Christian Peters

Geschäftsführer / CEO

MUTEC Gesellschaft für Systementwicklung
und Komponentenvertrieb mbH
Siekeweg 6/8
12309 Berlin, Germany

 

 

[Muziqboy]

Per Mutec's CEO, leaving the stock SMPS connected is NOT advisable:




[COLOR=0000FF]"Yes, the MC-3+USB does not need 1.2A, so from that all good. But using a linear power supply you must remove the internal power supply of the MC-3+USB. That means you must remove the whole PCB out of the case and de-solder the power supply from that. Dont simply connect the two cables of the linear power supply to the pins of the MC-3+USBs SPS. That would let the secondary stage of the SPS run as well! Please also consider that when doing this modification, you are losing the warranty claim.

 


I have attached a PDF showing the PCB print of the mainboard. The two DC outputs of the internal SPS are marked with + and -. At these points you must connect the cable of your linear power supply.


Please report how your MC-3+USB performs after the modification has been carried out.


Good luck!"


Regards, Chris.

Dipl.-Ing. Christian Peters


Geschäftsführer / CEO


MUTEC Gesellschaft für Systementwicklung

und Komponentenvertrieb mbH

Siekeweg 6/8

12309 Berlin, Germany[/COLOR]


 

I have read that but for some reason if you remove the smps, the Mutec usb version is having a hard time locking on the incoming digital signal. Both me and JJ have recently experienced this. The solution that I stumbled upon is to try different 5.5 x 2.1mm dc plug until I found one that gave me a solid lock on to the incoming digital signal since I installed a 2.1mm dc female jack on the back of the Mutec.

Might have something to do with current supply don't know. I'm just guessing at this point.

 

[johnjen]

OK so here's the deal.
 
I lowered the voltage to 5.219Vdc (from 6.255Vdc) and the 3+usb is now working and is stable.
 
Which begs the question why is the SMPS, when it outputs 6.239Vdc (measured), but when using 6.255Vdc from a LPS, causes problems?
This is a head scratcher for sure.
 
And why does the 3+usb use 6Vdc when the 3+ uses only 5Vdc?
But even more of a conundrum is why are these circuits so sensitive to just 1 volt difference at their input?
 
Usually they have regulators whose job is to lower the voltage to that which is needed by the circuit so the input voltage can have a fairly wide range of input voltage variance.
Except in this case even 1 Vdc is too much, even though the SMPS output voltage was ramped up for the 3+usb.
 
A head scratcher anyway you look at it.
 
So if you match the voltage of a LPS to the output from the stock SMPS for your 3+usb, and it becomes unstable and won't latch onto the digital audio signal, try lowering the voltage down to 5.x Vdc.
It works for me and I'm now hearing what others have reported as a benefit of the 3+usb vs the 3+ and without the SMPS veil.
 
I sent in a request to Mutec for their repair services, but will shift gears a bit and ask them why this situation exists and report back what their response is.
 
JJ

 

[Muziqboy]

  OK so here's the deal.
 
I lowered the voltage to 5.219Vdc (from 6.255Vdc) and the 3+usb is now working and is stable.
 
Which begs the question why is the SMPS, when it outputs 6.239Vdc (measured), but when using 6.255Vdc from a LPS, cause problems?
This is a head scratcher for sure.
 
And why does the 3+usb use 6Vdc when the 3+ uses only 5Vdc?
But even more of a conundrum is why are these circuits so sensitive to just 1 volt difference at their input?
 
Usually they have regulators whose job is to lower the voltage to that which is needed by the circuit so the input voltage can have a fairly wide range of input voltage variance.
Except in this case even 1 Vdc is too much, even though the SMPS output voltage was ramped up for the 3+usb.
 
A head scratcher anyway you look at it.
 
So if you match the voltage of a LPS to the output from the stock SMPS for your 3+usb, and it becomes unstable and won't latch onto the digital audio signal, try lowering the voltage down to 5.x Vdc.
It works for me and I'm now hearing what others have reported as a benefit of the 3+usb vs the 3+ and without the SMPS veil.
 
I sent in a request to Mutec for their repair services, but will shift gears a bit and ask them why this situation exists and report back what their response is.
 
JJ

 
Here's another head scratcher just for kicks. The first Mutec usb version that I have is still being powered by the LPS that I originally got to power it which is 6.3vdc output.
When I first modded it, I just soldered wires to the + and - pins on the Mutec board and got the other end of the wires soldered to a female 2.1mm dc jack mounted on the back.
I did not removed the smps in the Mutec and it was locking on to the digital signal in an instant without problems.
 
It's when I removed the smps that I started having problems with the signal not locking and the blue led lock flickering. So I kept replacing the 2.1mm male connector of the LPS cable until I found 1 that finally worked and I got a solid blue led lock. So ya, I'm still powering it with 6.3vdc without any problems now.
Ponder on that.

 

[johnjen]

My understanding is that most circuits that use 5Vdc should be able to utilize at least a +20% higher voltage, which is 6Vdc and I have seen instances where 7.5Vdc is 'acceptable'.
 
And in your case it could be that the SMPS is pulling down the voltage that the rest of the mainboard 'sees'.
Which in turn may lower it enough to avoid this scrambling of its pea brain.
 
And I wonder about what effect the firmware update for the 3+usb has on all of this as well.
 
And it may have been a current limiting situation with the barrel connectors you were using, until you used the 'correct' one.
 
So I'll dive into what is going on with all of this when Mutec replies to my request.
 
JJ

 

[Acrobat77]

Hi all, I'm the person who linked to the manual that describes how to remove the push lever from the AES/EBU XLR connector of the MC-3+ USB. One of you linked to the topic where I shared it or copy-pasted the text I wrote.

Anyway, just chiming in to say my MC-3+ USB works fine with the original SMPS removed. I'm powering it using one of the four rails of my Paul Hynes SR7-MR4 PSU which is configured to output 6.2V. The DC output wires are soldered directly to the Mutec mainboard. I'm using just two inputs of the Mutec; primarily the USB input coming from a SOTm sMs-200 and occasionally the Toslink input from a HTPC.

It worked fine both before and after the 1.10 firmware update of the Mutec.

Good luck in solving the issues you guys face. No idea why it doesn't work for you.

 

[johnjen]

Thanks for the input and yeah it is rather strange that it should be so sensitive to the input voltage.
 
And I'll investigate the firmware updates to see if there is any correlation there and also see what Mutec says about all of this as well.
 
This is a first for me where an electronic device has this degree of difficulty with the variation of its power supply voltage.
 
But I must say I'm rather pleased with the results it brings to my system regardless of these foibles.
 
JJ

 

[johnjen]

More results from my fussings.
 
I found that my dual LPS was getting to hot for the regulator so it was 'protecting' itself, which is probably why the 3+usb was failing to latch.
 
So I opened up both ends of the case to let it breathe.
Then after it cooled down and stabilized, I again cranked up the voltage feeding the 3+usb to 6.2 volts and then power cycled it.
It failed to latch, until I lowered the voltage to 6.049Vdc when it latched up and has stayed operating properly ever since.
I see this as more details to help figure this all out.
 
And granted my dual LPS is WAY overkill for use with these low powered 3+'s which in turn means it generates more heat than a more purpose built LPS would.
So if your LPS case runs Very warm, it may be a good idea to add some form of additional cooling to the case, via either convective or forced air methods.
 
As an example I added a few vents holes to a Headroom BUDA power amp and used convective cooling and as a result the SQ took a small step up as a result.
 
So to fix the overheating LPS problem, I have 4 choices.
#1 I can drill some holes in the case and use convective air flow cooling.
#2 I can order a lowered output voltage and lowered VA rated transformer with (dual 7Vac instead of the existing 12Vac windings).
#3 Build up another LPS just for these 2 Mutec boxes.
#4 Add a fan to this case.
 
I opted to order up a Noctua 80mm 3 speed fan to either force feed cool air into or pull the hot air from the case.
Which is the 2nd least expensive option but the one with the most flexibility in terms of dialing in the amount of added cooling.
 
Which also brings up the possibility that others may also be running their 'home built' LPS units at or near their thermal limits.
And this in turn may be a contributing factor with these signal latching problems.
 
JJ