BEHRINGER UB1204FX PRO

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Hi,

I haven't modded this exact type of Behringer product but in all other devices I did mod (A500, DEQ2496, DCX2496, T1953, SRC2496) had SOIC devices on board. I swapped them for OPA2134 on the inputs & OPA2227 on the outputs and added extra supply bypassing. Works like a charme. Beware Behringer does not only solder the parts to the PCB but also uses a small amount of glue! I found that a desoldering hot air gun @ 400C works best for removing these opamps.
 
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Thanks a million Mark.C,

As you've indicated,the "chips" on these too could be SOIC types!

I was just wondering, you have mentioned that you swapped these JRC xxxx with OPA 2134 & 2227 devices. But, are not JRC 4580 BJT type,while OPAxxxx are JFET tyes? I am thinking on the lines of replacing these with NE5532 or LM4562 op amps. What's your take on this?

If the chips are glued as you've rightly warned me, then it would be a pity,that melting the glue would very likely fry the IC's, thus rendering these unusable. 'Cause JRC 4580 is not all that bad & are widly used in guitar effects & stomp boxes as well.





Thanks again & cheers.
 
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From the top of my head the OPA2134 are JFET devices and the OPA2227 BJT

I must admid that a part of the reason I used these devices is that I had them in stock. To me it made more sense to use the JFET devices as input & BJT as output. I also tried OPA2228 but these are not stable in this application and caused oscilations.

After this mod my noise floor was lowered quite a bit, but this is probably a combination of a cleaner power supply & lower noise opamps.

As long as you use an opamp which is stable at unity gain and can handle the supply voltages you should be fine, NE5532 should do a great yob here. The JRC4580 is certainly not a bad opamp for it's price but you can do much better.

When you are already busy inside the mixer check if there are any clocks generated by a crystal and a logic port (inverter). Filtering the supply of this IC with an LC filter and adding a beefy capacitor can do wonders here...

Regarding the glue, i didn't fry the opamps but the PCB itself is far more sensitive. If you pull on the IC a bit with tweezers you can be sure you will have some traces lift off the PCB. be carefull with this, very carefull!
 
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Thank you again for all your invaluable info...this is exactly what I was looking for! Much appreciated.

You, with a better insight than me in the finer points of modding, I hope, will be able give me some more tips & advice on generally improving this mixer as I dwell into this soon. I've actually uploaded the schematic elsewhere on this thread, so please do feel free to make any comments or improvements as you may deem fit from time to time.

I think,this piece of gear has a lot of potential,by the sheer number of mods done on this by many!
 
Thank you indeed for your offer with regard to the schematic. I do have the schematic for the UB1204FX Pro.I did try to upload this here,but couldn't as the PDF file size was way over (605kb) the limit allowed on this forum since all the 10 pages are combined or linked, so I don'r know how to export it 1 page at a time!

Please do upload it, as I am sure it'll benefit many. Btw, are the JRC 4580 on these SOIC types? Just trying to be 100% sure. What did you swap these with?

What other (critical) mods have you done to improve the UB1002?
 
This is all very interesting, as I am really interested in upgrading the opamps in some equipment.

One is an old Soundcraftsmen preamp I use mostly for source switching and unbalanced effects sends and returns. It's got lots of other mods, like years ago I upgraded all the interior wire to shielded wire and added power supply caps, added a switch to turn off the RIAA preamp section, added shielding around the power supply,
 
Hi teleman,

I can't find the schematics, I did a quick google search but that came up emty to.

If you can share (a part of) the schematics, I'll have a look.

Hi Cyclecamper,

If you have some room to spare inside the device you could have a look at really filtering the supply of the opamp, not just adding extra capacitance. A simple way to try (i use it a lot in my designs, both DIY and professionally) is a 10uH coil in series with the supply and a 10uF ceramic or tantalum cap to ground. cheap, simple, quick mod.
 
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Mark.Clappers,
As I've explained earlier, I'm unable to upload this PDF File due to it's rather large size (605kb)! Besides,I don't know how to seperate these 10 pages & upload it 1 page at a time! Any suggestions or workaround to this?

Perhaps, CFMartin can upload the schematic of the UB1202 for us?
 
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Hi teleman,


I can't get the PDF split up either, tried a few things (convert to BMP / DOC) but this didn't work.


Anyway, I did have a look at the schematic, that are a lot of opamps! If you want to replace them all you got quite some work to do.

1 thing that looks very familiar to me is the power supply. This is a very simple 7915 / 7815 based supply that can be inproved upon with little effort.

What I did in my mods is just rip out the voltage regulators and replace them with a "low-noise" LM317 / LM337 based power supply, but there are better regulators out there (National, TI, Micrel all have nice LDO's).

For the digital supply I used A LM317 set to ~ 9V and used transistors to futher lower the supply to +5V. since most of the digital IC's don't use much power these can be small, I used a transistor for every important "digital" IC (ADC, DAC, DSP). Also beads can help here for rejecting HF noise. And ofcourse the LC filters I mentioned earlier.

I would implement these mods 1 at a time and measure the performance with a scoop (with FFT function is great, it lets you zoom in on the problem area's real quick, or even better use a spectrum analyzer + scoop) after every mod.
 
Here is what I did to UB1002. As I wanted to shorten signal path when using micpres, I converted line in connections to dir out in the two first channels that have micpres. Behringer UB1002 micpres are typical complementary feedback pair (CFP) designs. In the original schematic line inputs have been done simply connecting 10k resistors (R4, R8) to the input transistors. Together with bias resistors (R9, R15) they form a voltage divider and a line level signal pad. But as the UB1002 is loaded with dedicated line level inputs it was better for me to convert channel 1, 2 line inputs to dir outs.

10k SMD resistors R4 and R8 (in this schematic) are removed and former input capasitors C4, C5 are reversed or better jet, replaced with bipolar capasitors. 47 ohm resistor is soldered between opamp output (RC4558 pin 7) and capasitor C5 (leading to 6,3mm jack tip). This is the “hot” output. To get impedance balanced output, another 47 ohm resistor is connected between C4 and ground forming “ring”. As the input and output are really close together it’s important to keep resistor wiring far from input transistors to avoid oscillation.

I also changed 4558 opamp (SO8) to NE5532. It can better drive loads directly and has lower noise. C7 and C13 were added to filter out the bandwidt above 200kHz or so.

As Mark pointed out 7815 and 7915 regulators should be changed to something better.

An externally hosted image should be here but it was not working when we last tested it.
 
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Hi Mark,
Thanks for trying just the same. Perhaps if these pages could be scanned seperately, then might be small enough to upload..page by page! Why the this generous file size limit? Puzzles me!

Yes, you're right, I counted 35 dual chips in all! I thought I'd first replace the 4 mic/line inputs with NE5532 & 2 LM4562? as stereo pairs & then improve the PSU section as you have done,test it & take it step by step.I also calculated that it's very economical to stick to one type IC like either LM4562 or NE5532 if one wishes to replace all the LINIER IC's to just one type. At Mauser & Digikey,a total purchase of + £50,00 ex.VAT/taxes & over will entitle you to free postage too, which otherwise costs £12,00!

I don't have my mixer with me ATM & have no access to it until late March. So all I can refer to are the schematics & the User manual for the time being. Is the Phantom power global on all 4 mic/line channels? ie;either on or off? If so,then wouldn't be a good idea to incorporate seperate switches on each ch. to switch these on or off?

Good idea indeed to change the 7815/7915 to LM 317T/377T for increased current handling?

CF Martin,
Nice introducton to your mod! I notice that the UB1002 mic/line circuit is different from that of UB1204? could you please explain the importance of C10=680pF in the loop?

So, the ICs are SOP types & NOT SOIC on the UB1002 then? Any idea on adding a 12dB pad to this UB1204 then?

It would be just fantastic,if we can gather as much info as possible on this thread,so that it would be a comprehensive referance (manual) to anyone who wishes to mod these UB series mixer!

Thanks guys & keep up the good work!
 
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Hi Mark,


Good idea indeed to change the 7815/7915 to LM 317T/377T for increased current handling?


Not so much, but some extra current handling capacity doesn't hurt either :p The idea behind all the power supply mods is to lower the noise floor of the system. I did this by seperating the power supplies of the various IC's with LC filters & beads, use better regulators, and suppressing any digital noise as close to the source as possible (and better opamps ofcourse).
 
Yes, you're absolutely right; more current handling & more importantly much better noise specs! I did build a few PSUs based on LM317T/377T for my earlier projects. These are amazingly quiet devices! However, as you've rightly pointed out, v.good quality b.rectifier,caps & metal film resistors certainly helped.

I am not yet good with LC filters & beads, but this won't prevent me from learning to use these either!
 
I would look at this another way. While I like a good DIY project and take on many maybe too many at times I tend to focus on projects that have some long term value. Spending time and money to mod a Behringer mixer is not one of those considering after spending the time and money it will still be a Behringer and most likely will have some issue or failure crop up in the future just like every Behringer product I have ever seen. You would be better off to go out and buy at least the original product that Behringer ripped off, copied and built with the cheapest possible parts and manufacturing techniques.
 
Hi Mike,

I agree with you that some Behringer products are not good enough. However my personal experience is different, I have a ADC / DAC (src2496) which is heavily modded and still going strong after 7 years. The same goes for my DEQ2496 & T1953.

Behringer products are not badly designed, they are designed with low, low cost as design objective. This can be a good thing for DIYers like us (buy a DAC for E130,- and start modding, if the thing breaks down who cares, it's only a E130,- piece of equipment), but this is a bad thing if you want to use it (semi) professional.

The big upside for us DIYers is that with relatively simple mods you can get a nice piece of equipment for bottom dollar (or euro :) )

Just my 2C
 
Yes, you're absolutely right; more current handling & more importantly much better noise specs! I did build a few PSUs based on LM317T/377T for my earlier projects. These are amazingly quiet devices! However, as you've rightly pointed out, v.good quality b.rectifier,caps & metal film resistors certainly helped.

I am not yet good with LC filters & beads, but this won't prevent me from learning to use these either!

Beads are very simple devices, they have a impedance curve in the datasheet, and as long as you don't saturate them they should follow this quite closely.

LC filters are not that difficult either, make sure the Rdc of the coil is low, you target the right frequencies with your filter and measure a lot to verify everything. A nice tool could be this one: AADE Filter Design and Analysis

I use it a lot, even at work to simulate filters used in TV applications (IF bandpass & lowpass filters). My designs are currently used or have been used in a lot of TV's from big brands like Philips, Samsung, LG, Vizio to name a few. So it can't be to bad right :cool:
 
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