Hello fellow gear slutz and gurus. I seen another thread on a modification for the DBX 163X. I decided to touch up on the same modification but with other modifications included as well. DBX 163X (Hong Kong Version). I know this is old news already but it is new news to myself as I just decided to buy one of these compressors at a steal price. Untouched and original. I was wondering if anyone can help me find anything I may be missing. I have attached a photo which could act as a chart.

Power Supply Unit Modification (PSU)
The Blue circled items on my diagram are the PSU mod that requires removing these caps and replacing them. The caps in position C28 and C29 can be replaced by larger caps upwards of the known 2200uF 35V 105C, the smaller caps in position C30 and C31 should be replaced by caps of 100uF 35v.

Voltage Controlled Amplifier Modification (VCA)
The VCA mod is circled in yellow on my diagram. I replaced the current SIP8 VCA with a THAT2180A VCA. I then remove the R9 and R10 resistors that are next to the VCA circled in yellow.

Operational Amplifier Modification (OPAMP)
The operational amplifiers are DIP8 chips that are circled in orange on my diagram and the board has them labeled as OA(?). I simply replace them with ultra low noise versions. Optional is to add a socket to make swapping them easier. Some of the recommended OPAMPS for the position of OA1 are the NE5532, OPA2132, OPA 2134, OPA2107, LT3158, or the preferable LME49860NA. The OPAMPS that can be swapped in for OA2 are OPA134, OPA602, OPA627, LT1357, or the preferable LME49710NA. I have also read that replacing OA3 and OA4 with an LME49860NA can help considerably, but this is an optional modification.

Capacitor and Resistor Modification
This modification is to ensure durability and stability and I have them circled in Red on my diagram. It may also stop overheating issues that some have reported. Remove position C1 completely, Replace C2 with a ferrite bead. Replace C5 with a 22uF 35V bipolar capacitor. Remove C7 completely. Replace positions C3, C4, C8, C9, C10, C11, C18 & C19 with 0.1uF capacitors. Replace positions C24 & C25 with 0.01uF capacitors.
For the resistors I have them circled in gray on my diagram. Simply replace positions R1 & R5 with 1kΩ metal film resistors. Lastly, replace R16 with a 22Ω metal film resistor and R2 with a 100KΩ metal film resistor.

This should pretty much sum up everything that I have done so far on my DBX 163X. Please if you have anymore information on any of these modifications, inform everyone by sharing on this thread. I have seen bits and pieces all over the place but never a solid thread about these modifications. I hope this helps someone who owns one of these compressors or maybe a different model that can use similar modifications.

Old bump i know. Thinking of doing some but not all mods to a pair of 163x. Thinking about replacing all caps with sanyo os con? I dont think i want to change the op amp but would do a 5532 if anything?

Upgraded my pair of DBX 163x !!!!
After a lot of reading, looking at schematics, sifting through the "Jim Williams Mod" comments but not finding any exact instructions, I finally settled on a plan of action... here's what I've done with notes:


1. Replace C28 & C29 with 2200uF 35v electrolytic caps

2. Replace C30 & C31 with 100uF 35v electrolytic caps

3. Replace C32 & C33 with 10uF 50v electrolytic caps

4. Replace IC1 with a THAT 2180A (9 bucks on mouser in 2019)

5. Remove trim resistors R9 & R10 from the board. The new VCA is pre-trimmed. (be sure to look for "R9" & "R10" designators on your PCB. There are pictures of this mod out there circling the wrong resistors.)

6. Replace OA1 with an OPA2134PA (5 bucks on mouser). I put in an IC socket first. As usual, check orientation before plugging anything in.


thats it!


There are other mods out there that recommend replacing every op amp, cap, and VCA on the board, which would easily triple the cost of modification. My goal was to smooth out the power supply as much as possible, and spend big on the chips that are amplifying the signal. IC1 is the main VCA (the compressor), and OA1 is the amp that feeds it signal. IC2 is RMS detection, so it is watching the signal but not part of the sound. OA2, 3 and 4 are level set, threshold set and output buffers, which I did not swap.


So far these are sounding AMAZING. Clean, loud, and a lot of color.

Considering whats out there, this $50 mod (for the pair) is really worthwhile.

Etienne
Rithma Music

@ rithma :
Little newbie question about the mod:
When you write "Remove trim resistors R9 & R10 from the board", do you mean remove the resistors and leave the trace cut, or solder/connect the trace back together afterwards?

I know you posted a while ago but for those who read this later, you remove the resistors and leave them off the PCB or just cut pin 4 off the VCA. The 2150a needed to be externally trimmed and the 2180a is internally trimmed. Pic below shows the pin out configuration and as you can see pin 4 is labeled NC for “no connection.”

I’ve done the mods listed above on both of my 163’s and the improvement is well worth it. My next step is to swap all the carbon film resistors with Dale CMF55 metal films. I’ve done this one channel at a time in my console and it makes a considerable sonic difference.

Hey guys,
The Panasonic EXC-ELSA39 Ferrite bead from Digi-key is obsolete, but they have a 75 ohm and an 86ohm Ferrite bead rated for 5A. Would one of these suffice in place of C2? I know Mouser has an 82ohm 7A FB, but would like to keep my whole order with digikey if possible. The Ferrite bead from mouser is $0.46, but the shipping is $20!!!!!!!

I still don't quite understand how I'm supposed to know what value ferrite bead I'm supposed to use. I also don't know what kind of 0.1uf caps I'm supposed to use. Do i match the voltage of the old ones? I've read film caps are preferred to ceramics, should I use those instead? I'd really appreciate some readily available choices.

Quote:
Capacitor and Resistor Modification
This modification is to ensure durability and stability and I have them circled in Red on my diagram. It may also stop overheating issues that some have reported. Remove position C1 completely, Replace C2 with a ferrite bead. Replace C5 with a 22uF 35V bipolar capacitor. Remove C7 completely. Replace positions C3, C4, C8, C9, C10, C11, C18 & C19 with 0.1uF capacitors. Replace positions C24 & C25 with 0.01uF capacitors.
For the resistors I have them circled in gray on my diagram. Simply replace positions R1 & R5 with 1kΩ metal film resistors. Lastly, replace R16 with a 22Ω metal film resistor and R2 with a 100KΩ metal film resistor.

I did not do the Ferrite bead. I recapped the electro’s. The .1uF are mononceramic. Get Vishay. They are for decoupling and giving extra power to the op amps for stabilizing them. Audio does not pass through them. Metal film resistors are typically said to sound better. I agree with this after changing them out in several pieces of gear. You only need to do those in the audio path. Electrolytics degrade audio so the more you can pull the better. As Jim Williams says, “the best capacitor I’ve ever heard is a piece of wire.” Films are better for audio when you can sub them. Electro’s in the audio path should be bypassed with a .01 WIMA 250v cap. You solder them on the foil side of the PCB. That’s the opposite side of the component side. Your ears will thank you. I need to revisit these mods. I’ve learned a lot more since doing them. I use both of mine in series on every mix for bass. I’ve used them for parallel compression of a drum sub mix but they were replaced by modded DBX 166’s.

Here some pics of .01uF’s added on the foil side and .1uF’s added for decoupling. Red are the WIMA’s bypassing electro’s and yellow are for decoupling. They go from the power pins of the op amp to a nearby ground. You can see in one instance where a .1uF was soldered to the ground trace. Little tricks like that are your friend.

You've been very very helpful. What voltage should the mono ceramic be?

I do 50v because it pretty much covers anything solid state. I use Vishay. I don’t buy anything from EBay anymore because of rebranded fakes. Mouser and DigiKey are your friends and places like Parts Express. They’re more expensive but you know your getting what you pay for. I compile a running list of parts for projects and make big orders to save on shipping. I’m in Texas and I prefer Mouser because regular UPS is next day for me. Usually by noon.

And most of the advise I’m giving is regurgitated advice from the likes of Jim Williams, John Roberts, Matt Syson, Brian Roth, Nosebleed, Gyraf, Ruffrecords, Audio-specific and the likes. They’ve done a lot of the R&D for us and monuments should be built for them. They don’t have to share their knowledge. I’m passing on what’s been passed on to me.

This has honesty been the best, thank you. I have one last question if you dno't mind as I tend to be thorough. How much do tolerances matter in this context?

Depends on the part. Electro’s are generally 10-20%, I aim for 10%. Films are 5-10%, I aim for 5%. Resistors in metal film can be found in 1% and that’s what I get. If your swapping op amps get milmax machined sockets so you can easily swap op amps later.

Google your questions in short hand form. Tag Gearslutz on the end and you’ll get lots of hits. Some people read novels, others short stories or magazine articles. I read Gearslutz archives, DIY Audio archives, gear manuals and schematics. The more you red the more you’ll learn. The more you do, the more you’ll be forced to learn.

Some other tips.

1) caps of same value come in different physical sizes as well as with different lead spacing. Make sure you get the cap that will fit the PCB. Leads can be manipulated to fit but it’s better to order the correct part.

2) caps also come packaged differently. Some bulk, some tape reel, etc... If you don’t want to rip the tape off the leads buy bulk, however, I buy my .01/250 WIMAS in tape reel because the leads are longer and easier to manipulate.

3) you’ll find most designs share and use similar values. I buy more than I need and have parts in parts bins. I’ve gone through gear and not had to buy a thing because I had it on hand.


4) never stop reading.