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DBX 118 Modification - Little help?? Dynamics Processors (HW)
Old 3rd July 2007
  #1
Gear maniac
 

Thread Starter
DBX 118 Modification - Little help??

Hey all,

I have a DBX118 that I want to "fix up" and have a couple of questions cos I am a bit of a noob when it comes to DIY...

1) The IC's on the board are OA2 TI RC4560, OA3 TI RC4560, OA4 AD 712 and OA5 LM 301AN... Can anyone suggest replacements for these? I am thinking Burr Brown but don't know which ones to choose...

2) The power supply is mentioned as coming in at +/-12VDC... Where on the board would I attach these to if I was to build a bigger and better damped PSU for this?

I have attached schematic and a pic of the PCB for your perusal...

Any other suggestions to pimp this guy up? I want to keep the same basic characteristics but improve the freq response and hopefully reduce the noise, it hisses like a snake.

Thanks heaps!!!
Attached Thumbnails
DBX 118 Modification - Little help??-dbx118.gif  
Old 3rd July 2007
  #2
Gear maniac
 

Thread Starter
Here the GIF of the PCB...
Attached Thumbnails
DBX 118 Modification - Little help??-dbx118_a_m.jpg  
Old 3rd July 2007
  #3
Change opamp 3 to a LM4562, LM6172, AD8599, LT1358. Use a machined socket to test them. Add a couple of .1 uf mono ceramic caps from pins 4 and 8 to pin 3 (ground). Bypass the .33 uf input cap with a .01 uf polyprop film like Wima. Change the 4.7 uf output cap to a 220 uf 25v Panasonic FM with a .01 polyprop bypass.

The power supply has lots of ripple, the National 4562 has very good PSRR. I would add some 4700 uf caps into the psu mains to limit the hum. If you replace the power transformer with a small torriod, you can get the secondary voltage up to over 18 volts. Then you can fit a couple of 7815/7915 regulators in there and really quiet it up.

Jim Williams
Audio Upgrades
Old 3rd July 2007
  #4
Opps, I didn't see the 723 regulator, that's fine. Live with the 12 volt rails unless you want to reset the dividers and up the voltage a bit. A new transformer will be needed. This is a very old version as it has the discrete VCA/RMS cards on it like the 162. That VCA pcb could probably use a LT1357 single on it. Or a OPA211, or a LME49710.

Jim Williams
Audio Upgrades
Old 4th July 2007
  #5
Gear maniac
 

Thread Starter
Thanks Jim. Any other replacements you'd suggest? How about OA2, 4, and 5?

When you're talking about bypassing caps, do you mean wire them in parallel?
Old 4th July 2007
  #6
The rest is side chain, only one chip is used for audio. Lay the polyprop across the elec cap. Measure DC on it's output. If + v, place the + pin on the output cap towards the + voltage. If the National LM4562 or LT1358 are used, the output cap can be eliminated.
Old 22nd September 2011
  #7
Gear interested
 

I have here two DBX 119 and one DBX 118 , I want to put all 3 side by side (removing their wooden sides) inside a rack enclosure (one of those made for two DBX 160Vu model) and change their i/o's to balanced and replace their AC cords for sockets. It's kind of a DIY project, I'm learning.
But before starting that , I checked on google about mods and found the Burr Brown thing and also the replacement of the capacitors. It's supposed that by doing those you get better frequency response and eliminate a bit of distortion,... but how much????

I also watched the ebay guy who offers the mods for absurd prices, I even asked him to sell me a mod building kit with the components because I live in South America and can't send all 3 dbx's to the States. He said no . no kits for sale.

It's also my concern that by changing their original OPamps they can lose their original sound. I like these boxes because I like how they turn weak signals to warm organic when amplified . So I was thinking maybe I should start my project without OPamp and caps replacement.
Also , it seems that the only person in the world who can give info on this mods is the ebay guy, damn.

if anyone have done these mods please let us know if it really improve the dbx sound without changing their vintage quality.

I thought it could be a good idea to take pictures of the DBX PCB and hang them here so maybe someday will show up and explaing a bit more about what to replace , with which Burr Brown OPamp and which capacitor etc etc etc..

If some of you guys find out something please share it here.

Good Luck!
Old 30th July 2012
  #8
Gear Nut
I have a UK dbx118 (230 volts) so I'm confused as to whether to take certain advice here or not about cap values.
I want to replace the input and output caps (C1, C2, C5, C9).
My 118 has 470uF 40V input caps and 4.7uF 25V output caps atm. I put an OPA2134 in OA3 a couple of years ago.
Should I just replace the caps with the same values?
Cheers.
Old 31st July 2012
  #9
Lives for gear
I'm pretty sure that the cap values in rye circuit would be fine to change... The UK 230 v thing really only matters for the transformer and maybe the fuse if it has one. Once the juice is past the transformer it does really matter that much where you are, the insides are still the same.

sent from my m-3500 using the gearslutz app
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