Mixer is dying. Time for a mod.

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Mylithra

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I have a Behringer DDX3216 that Ive had for a few years now. Today during my band's practice, the entire mix started cutting out. Being that the alternative is buying a new mixer (which is $$$ I dont have at the moment) I decided to attempt to fix it and while Im at it, Mod the thing.

Since it was affecting the overall mix and none of the meters showed a signal dropout, I have to assume the problem is on the Analog Out board.

It could be any number of things but I havent dug deeper into it yet. At this point.. I think it might just be better to see if I can replace the entire Analog output board. I also thought it could just simply be one of these opamps has gone bad in which case, the next bit might solve that problem for me.

As to the modding,
Assuming I can fix the output problem, The only real mods I thought about doing to this was getting rid of all the NJM4580s in favor of the OPA 2228 and replacing all signal path caps with Panasonic. The A/D Converters are AKM5383s. I use the BLA Microclock as an external clock source so I wont be screwing the clock or the converters on this.

Anyway, Ill post some pictures once I see about some parts.
 

s2udio

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I have the DDX also ,now 5 years old,have had no trouble with it
at all ,but am thinking of servicing it soon,replacing the psu fan
and giving is a good blow out
keep us posted as this could be a handy thread for DDX owners
I tried to obtain a service manual from the uk service agents
Pro Line Audio Ltd, but as expected they declined to sell me one !!
so anyone who has a full service doc , help obtaining one would be
magic
:thumb:
BTW Mylithra i doubt its on the way out,just a little tlc required !
maybe the multicons need a clean
 

Mylithra

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Well, the part I was dreading.. The phone call in the Behringer's service center. I was answered by a human in less than a minute who ask me what I was looking for and transfered me over to someone else. I spoke with this nice young lady who asked me what I had and what I needed for it. I told her I had a DDX3216 and I needed the Anaout01 board:
anaout01.jpg

She typed away on her computer and asked me to hold for a moment. Not more than a minute later, she came back and said that they didnt have any more brand new parts, but they had another mixer, returned to the factory with a dead CPU board and they could take the Anaout01 board from that one and send it to me. They asked me for my address and said it should be heading my way in the next day or so. No charge. This was my only experience calling into behringer and I have to say I was quite pleased, but I digress. Im getting a replacement out board.

Now for the ugly.
They really LOVE the hot glue at the Behringer factory. I mean its everywhere.. In fine strands, slatherd on ribbon cables, I mean.. it really was ugly. On the connectors, I used an Ice cube wrapped in a paper towel to get it cold and used a pair of needle nose to pull the glue off in 1 piece most of the time. For the more delicate things, I used my soldering iron to heat it up (just got it close enough to melt it) and used a cotton swab to coax the glue into an area where I dont have to be so delicate to get the glue off the board. It took a while but I eventually got most of what I needed to get off the parts.

Now on to the other good stuff:
The Analog In board:
If you havent read the block diagram for this thing, look it over carefully before doing anything. I dont have a schematic to work from so Im going from what that says, and what I know of circuit design. When it comes right down to it, its pretty simple. Take you generic Mic pre schematic (such as the one for the INA217) make a couple of modifications to the circuit and you have whats on this board. The OPAMPS in this thing are the much viled NJM4580L. In a SIP configuration no less. Theres 1 dual opamp per 2 channels. There are 4 electrolytics in the signal path per channel and 1 that the phantom power goes through. .
anain01.jpg


The A/D Converter board: (the AKM AD convters are on the flipside of the board. These are the parts Im going to mod though. )
anain02.jpg



The rotary encoder control board: Note the missing encoder on channel 4. Had a Mic fall right on that knob and busted the shaft. I never made a difference in the channel only becase I could still use the knobs under the LCD to control whatever the encoder would but since I have it in pieces anyway... Might as well fix it.
ctrl11.jpg


and lastly, the underside of the front cover. I had no need to remove the pirmary control surfaces from their mounts so I didnt. Only the Encoder board needed to come off and as luck would have it, it was the first card on the stack.
frontcover.jpg



Heres inside the case. It contains the shielded power supply, the CPU board, (Its an AMD CPU if you're wondering), the DSP board for the effects and the rails for the expansion cards.
caseinside.jpg


So on to the modding:
Initially, Im just going to test to see what the difference will be with the change in components beforing throwing down a lot of money on doing the whole mixer so,

On the Anain01 board:
The list of parts to be replaced.
The opamp that runs Micpre 1,2
The 2 opamps that drive line in channels 15 and 16
and all the capacitors in the signal path of those channels.

On the Anain02 board
the 2 opamps on the first 2 channel that drive the line ins the AD converters as well as their related signal path caps.

On the Ctrl11 board:
just replace the rotary encoder with one that doesnt have a broken shaft. :)

On the Anaout01 board:
The 3 opamps that drive the Control Room outs, the 3 opamps that drive the Main outs and the related signal path caps.

Bringing the total of 11 OPA2228s. The total for this would be well over 50 if I was doing to whole thing so better to hear what the difference will be at around $50 in parts rather than the $200 or so it will cost to get parts fo the whole thing. Plus, by only doing these components, I have a means of comparing the modified to the unmodified and can make some samples.
Ill keep updating as things progress.
 

s2udio

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Excellent work m8 i would love to see what improvement
the mod does.
If results are favorable i just might take the plunge myself !
Are you planing to mount the OPAs on sil headers of some kind ?
 

Mylithra

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So. Texas
http://www.cimarrontechnology.com/index.asp?PageAction=VIEWPROD&ProdID=34

It turns the OPA2228 into a pin compatable replacement for the NJM 4580L
 

s2udio

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Nice find but hard to find in the uk
I will only be modifying the input section as the Aouts are used for
monitoring only , I use the ADAT option cards for recording and
playback to an HD24
I may knock up some DIY stripboard headers .
 

rafafredd

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bd060301_7.jpg


mmm... I could use these pins for a project of mine... Does anyone knows where to get it maybe? A Farnell part number would be great, if there is any. Or maybe RS.
 

Mylithra

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The link I sent earlier in the thread was the only place I could find them anywhere. I think it would either be getting them from Cimarron Technology or do up a batch using a PCB editor and some PCB manufacturer like ExpressPCB.
 

Mylithra

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So I got the first set of parts for this thing.
chips.jpg


The spaces are pretty tight to try and get the old OPAMPS out of some spots on the boards so I just bent them back and forth till the leads broke. Better to just snip out the old part than to try and screw up a PCB.
As you can see, the size is not all that different so everything should fit back together with no trouble.
 

Mylithra

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Well,
I got the new OPamps into their SIP boards and got them loaded into the PCB. The new rotary encoder came in and got installed. Im still waiting on the Anaout01 board thought. I did start putting it all back together and I did take some more pics which I will upload when I get home. All thats left is to swap the opamps on the out board and IT LIVES!!
 

s2udio

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Excellent work ,looking forward to the conclusion :thumb:
BTW ,come to think of it,i had some trouble with the aouts ,it turned out
to be the jack sockets ,corrosion i believe as a good clean and lube with
vaseline (petroleum jelly)cured intermitent cutouts
:wink:
 

AJMAC

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kansas
It will be interesting to see what the upgraded components do to the sound, bringer typically rips off pretty solid designs.. :green:
 

Mylithra

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So. Texas
Well,
Here we are , over a month later, and the parts finally come in. Ill try to keep to the facts in all this and keep my opinions to myself.
I called Behringer on Aug. 26th. Told the parts person my problem and what I needed. As I had stated before, they didnt have a new Analog Out Board to send me but they did say they had a dead mixer that they could rip one out of. I had said that would be ok. After 4 weeks of not hearing anything I called back. They person didnt seem to know who I was or what I wanted even though it was the exact same person I talk to over ther. I repeated my problem, what I had wanted, and what they said they would do. They had a hard time locating the part but she took my name and number and said they would call me back. A couple of days later, I received a call from a friendly Behringer repair shop. They guy there wanted to make sure he got the right board to send to me. I told him what Behringer's part number and name for that board was. A couple of days later, Behringer called me back to confirm my address to send me the part. This was the thrid time I had given them my address but I digress. That was about 8 days ago. I got the part today and everything was in good working order.
So it took 6 weeks to get the part here but it did get here and I didnt have to pay for it so I leave it to you to determine if the way everything went down was good.

I got the 6 of the old opamps off the board, 3 for the main channel and 3 for the control room out, and replaced them with the Burr Browns. I put it all back together and fired the mixer up. (Saying a little prayer that it all wont blow up in my face). The mixer lit up and looks to be functioning normally. I plugged a Mic into it and tested the modified channels as well as the un-modified channels. Everything works like it should so I at least put it back together correctly. :grin: The difference was not immediatley conclusive so I will have wait to throuroughly test it. I now have to get my studio cleaned up and ready to be wired up again. I dont think I'll have time to do that during the week but once I do get it done, I will post a few audio clips of both the modified and un-modified channels.
 

Mylithra

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OK.. I started getting into the whole rewire of the studio.. Got the basics hooked up. (1 output from the Computer in via Light pipe, the Word Clock and the control room out. At random, it will start having this high frequency noise.. My guess would be something akin to RF. I thought it might be because the new opamps were oscillating though Ive never heard an oscillating opamp so Im not certain what one sounds like. I attempted to put in some decoupling caps, .1uf 50v ceramic caps between the the V + in and the V- in but then it sounded very weak and distorted. Im guessing I got the decoupling wrong.

example.gif


Did I use the wrong values, did I just get the decoupling wrong or could it be something else like one of the amps is bad?
 

Igor

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Hi, just my $0.2....it's easier to build a new mixer instead of moddin' Behringer ;)
 

Mylithra

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Maybe so, but if Im having trouble getting this to work, I dont think Id be able to do it from scratch. Besides, I take this as a good learning experience.
 

smallbutfine

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OK, I have some opinion about the OPA2228---
It is a great opamp, but unstable in some applications.
I always thought it is not unity gain stable if I remember right, I always preferred OPA2227 when modding things and using 228 only as a try when I had then occasionally at hand....
Maybe you should try some cheaper alternative like NE5532 first - to me it sounds still far better than the 4580 so called audio opamps. (also note that the OPAs need more current... sorry, I'm writing this from memory, so I cannot verify if this might be an issue in the behringer....but from my experience behringer psu's can be very picky with higher currents...)

Hope this helps and kind regards,
Martin
 

Mylithra

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OK.. I had a duh moment.


When I did the mod on the out board, I did both the control room outs and the main outs. When I hook up the control room speakers to the main outs via XLR, I get no noise. When I hook the control room up to the control room outs via TRS, I get the noise. Lets take a look at the board again.

anaout01.jpg


The 3 opamps that run the control room are the ones on the far left.
The 3 opamps that run the Main out are on the far right.
The circuits that run both are identical and since one does it and one doesnt, I have to rule out the Opamp in and of itself.
Now lets look at the bottom chassis:

caseinside.jpg

See the holes in the back plate for the out board? See what the out board is sitting right on top of? Note the main out are not over the power supply but the control room is. Its got to be picking up noise from the PS. So Im going to go back to the drawing board to find a Opamp thats going to be less susceptible to noise from the PS.

Hey Martin,
Im going to give the OPA 2227 and possibly the NE5532 but Im going to go back to the datasheets to make sure im well within the current draw limit of the PS.
 
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