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Another (ultimate?) Behringer mod - what can  do to DEQ2496  (PART 1)
Another (ultimate?) Behringer mod - what can  do to DEQ2496  (PART 1)
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Old 23rd March 2017, 04:19 AM   #31
calderes is offline calderes
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Don't bypass C29 and C28! That was true for the v2 board, but on the v2.5 board (different ADC chip) C11 and C12 are the ones you want to bypass.

C29 and C28 are .01uF as they should be, but could also be replaced with film caps.

I'll be continuing this journey on my new thread specific to the v2.5 board here:
DEQ2496 V2.5(!) (2017) Recap and Opamp Upgrade

Post #12 on that thread explains why C11 and C12 are the ones to bypass.
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Old 24th March 2017, 04:41 AM   #32
calderes is offline calderes
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after studying the new cirrus logic chip that replaced the akm adc, I think we'd better hold off on bypassing C11 and C12. (if they are proper C0G 10uF ceramics then they should be fine without modification) Please follow the thread I referenced in post #31 if you want more information.

The v2.5 board is just too different to be able to utilize instructions from previous mods.
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Old 28th March 2017, 02:35 PM   #33
PierOlo is offline PierOlo  Canada
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Wow!
long monologue by Calderes since my last visit, so I'll chime in and give him a little company...

So the identity of the mystery cap on the analog board would be C65. One thing solved.

It would appear the two 220p caps I missed are still on the run, as I do not see them on the analog board photos. (which are, by the way, very useful. That's what I should have done back then- thanks Calderes!)

"So PierOlo, you used polyphenylene Sulfide (PPS) Film caps for the surface mounts, no questions there."

uh, I never sais that! I did put in film caps, but I do not remember which variety. I just aimed for film caps, and not for top-of-the-line esoteric über stuff. I really have no interest in that esoteric stuff... If I find my original invoice from DigiKey I'll be able to say exactly what I did put in, but don't hold your breath- that was long ago...

All the electrolytics on the output section are doing is DC blocking. Their ripple-suppressing capabilities are irrelevant in that situation. I see that you seem to be going overboard about caps to replacement on the digital board... I see no point in replacing every electrolytic caps for the fun of it unless they are directly involved in the audio path. My prsonnal goal in this mod was just to correct a fundamental desing flaw (bad capacitor type used in audio path that do cause a perverse effect) rather than to give it an "audiophile" aura...

All this gives me more reason to re-open my DEQ, mainly to chase those 220p caps and to find out which version of the digital board I have. But I'm not that excited about removing it from the rack at my workplace, so it may take some time.

Keep up the good work Calderes!

Last edited by PierOlo; 28th March 2017 at 02:56 PM.
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Old 28th March 2017, 03:28 PM   #34
PierOlo is offline PierOlo  Canada
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Quick note: I found the invoice, they are indeed PPS caps...
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Old 19th December 2017, 03:30 PM   #35
avp1 is offline avp1  United States
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In my first post in this thread I wrote "Now you can find even more impressive devices like made by MiniDSP ot DSPeaker". I have to take away my words regarding DSpeaker - it is way less transparent than modified Behringer. See my test bench report here: DSpeaker Dual Core 2.0 – Test Bench Report

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Old 15th March 2018, 10:40 PM   #36
HeavyNova is offline HeavyNova
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Thought I'd post a complete ceramic capacitor list for the complete analog /jack board including both top and bottom (where they are mostly located) Here they are for anyone interested in upgrading the DEQ's analog section with films or having them at a glance.

20p x 3 = C36, C39, C40

100p x 20 = C10, C11, C13, C14, C2, C3, C61, C32, C33, C62, C63, C34, C35, C64, C46, C56, C37, C48, C38, C4

330p x 2 = C57, C58

390p x 4 = C66, C67, C69, C70

2n2 x 4 = C12, C15, C65, C68

10n x 3 = C55, C49, C59

100n x 11 =C8, C9, C50, C51, C30, C31, C60, C44, C45, C52, C53
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Old 16th May 2020, 07:03 PM   #37
Sensation45 is offline Sensation45  Turkey
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Default Deq2496 opamp

Deq2496
I have 3 types of opamps opa1656 opa2134 opa1612

Which opamps should I use for dac analog input and output?
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Old 8th June 2020, 10:44 PM   #38
Sensation45 is offline Sensation45  Turkey
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I say I use opa1656 for analog input ... I say dac a opa1612 ... I use opa1656 for output
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Old 28th August 2021, 08:21 PM   #39
DBMandrake is offline DBMandrake  Scotland
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Hi Everyone,

Interesting thread which runs at a slight tangent to one I just started regarding a channel imbalance fault in mine:

DEQ2496 repair/replace ? Anyone have a circuit ?

In summary my right channel is down about 1.5dB on the left channel in enabled mode but is matched in analogue bypass mode.

The frequency response of the bad channel is also not flat - there is significantly more loss in bass than treble, so there is approximately 1.8dB loss at bass frequencies tapering off to 1.2dB at treble frequencies.

As I don't have any digital sources or sinks available and use the device only in analogue mode, I don't know how much of this gain loss is on the input side and how much on the output side.

I've been unable to find a schematic and the reverse engineered schematic in this thread is the closest I can find.

I notice there are 4x 47uF electrolytic caps being used as DC blocking / AC coupling caps in the opamp signal path and these drying out, loosing a lot of their value seems to be a likely culprit for a loss in gain especially accompanied with a slight change in frequency response ?

Both channels have some loss in gain relative to the relay bypass mode (even the "good" channel is down about 1dB) but one channel is worse than the other hence the imbalance.

I notice most people in this thread are not really talking about replacing these 47uF coupling caps and focusing only on the ceramic caps...

I'm mainly interested in fixing the level imbalance issue on mine and with as little work as possible as I'm not well equipped to deal with SMD components. When I replaced the bypass relay a few years ago I found the PCB quality to be very poor making lifting tracks etc very easy, so I don't want to replace anything that isn't likely related to the fault.

Electrolytics seem like a poor choice for this type of coupling capacitor with a low DC offset - in an amplifier repair I did a few years ago with similar value electrolytic coupling caps in the pre-amp which also had an issue where one channel had low gain I replaced them with tantalum caps and that seemed to work well with no issues since then and the channels were perfectly level matched after the repair.

Would this be a reasonable replacement for the 47uF coupling caps ? Is there enough room on the PCB to fit 4 small "blob" tantalum caps?

The PCB pictures above indicating capacitor locations don't show these 4x 47uF caps, can anyone point out to me where they are located or their C numbers ?

My unit is a 1st generation model bought in 2004.
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Last edited by DBMandrake; 28th August 2021 at 08:27 PM.
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Old 30th August 2021, 05:04 PM   #40
PierOlo is offline PierOlo  Canada
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I don't have my unit near me, but 47uF caps should not be hard to spot...
I certainly advise against using tantalums in this position: as far as I can remember tantalums require strong biasing to work correctly. I would go for good quality electrolytics and maybe bypass them with small value films (0,1uF) for good measure.
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