Modify behringer DEQ2496?

[ChuckT]

Yes, they are connected to ground and the values on the board looks like is 100p.
Here's a pic. I am now starting to mod the PS. In goes the Blackgates.

[stef1777]

Be careful with the power supply. This is a switched power supply.

I will suggest you at start to mod only the two 470UF and the two 10UF before and after the 15V regulators.

- Replace C4 and C5 by 1000UF 35V with low ESR / hight ripple current (as Rubicon ZL). Will fit but you will have to push a little D1 and D2.

- Replace C1 and C2 by 47UF 25V tantalum (use good quality model as AVX Tap).

Write for reference, all voltage before and after regulators before tweaking. Write voltage with the digital card connected and without the digital card connected.

But the most important is to replace opamps.

[ChuckT]

I just found out that is only two 0.1uf decoupling caps for the four opamps. All the ceramics next to the opamps are for filter circuit, the 2 decoupling caps are located much further away.

The opamp will be replaced by lm6172, but I will definitely replace the whole output stage later when I have more time.

[stef1777]

Please put picture here if you identified coupling / decoupling caps on the analog board. This will help others.

[ChuckT]

Refer to my opamp pic, the pair of decoupling ceramic are just located in the top left of the pic where one is hidden under the black ground wire and another next to it.

[stef1777]

I have the DEQ with a complete 'new caps' power supply for a week and all is fine.

For the caps on the analog board, I waiting for an Black Gate PK source.

We have a thread there but in French. You can have a look on the pictures.

http://www.homecinema-fr.com/forum/v...761&highlight=

[ChuckT]

Hi Stef1777,

may I recommend not the use the PK grade blackgate, I have use those before and find them not very effective and not worth the price. I would probably just use a higher value ZL which also fits. Just my opinion.

Also, I have tested some the ecaps on the output board and none of those are from the +/-15v rail. So I believe they are just for the relay.

Do you know why it has 4 dual opamp for the output, the ak4393 datasheet shows that output stage uses only 2 for balance out.
Could it be possible that using lower gain will bypass 2 opamp?

[stef1777]

Originally posted by ChuckT
may I recommend not the use the PK grade blackgate, I have use those before and find them not very effective and not worth the price. I would probably just use a higher value ZL which also fits. Just my opinion.

Actualy as I don't realy know the use of the 7 ecaps close to the in/out, I haven't moved to replace them. The PK was not really expensive. Rubycon ZA seems better than ZL. 6.3mm caps can fit on the analog board. Elna (all type) do not fit execpt if we change value or voltage.

Also, I have tested some the ecaps on the output board and none of those are from the +/-15v rail. So I believe they are just for the relay.

Do you know why it has 4 dual opamp for the output, the ak4393 datasheet shows that output stage uses only 2 for balance out.
Could it be possible that using lower gain will bypass 2 opamp?

I don't know sure but you have 2 stages. I changed the 7 opamps... but at start I was looking to put AOP2134 on input and AOP2604 on output. As not sure where are the right one, I changed all of them will the same opamp.

But be careful, Behringer's engineers are vicious.

The PCB is really FRAGILE.

[ChuckT]

Ok, more probing shows that the ecaps next to the relay are coupling caps for the 1st opamp stage. There are 4, but I only trace the 2 to the opamp, the other two not sure.
So changing this should make a difference.
I put in Blackgate-N for the opamp coupling and cerafine for the other 2.

[ChuckT]

I have also change the opamp to lm6172. As the decoupling is fairly sad on this area, I have put in some cap that fits on the +/- pins.