Modifying DBX 163X

[runrunrun]

i have been rocking some modded 163x's for about a year now with great results. i recapped all the electrolytics, swapped the vca for a that corp one and upgraded the 4558's to opa2134's.

some day i am going to open them up and try fancier opamps in place of the lm353 and the 5534, but the mods i have already done make worlds of difference. i have a 263x on the way that i am planning to mod in the same way. will let everyone know how it goes.

[Sean Sullivan]

I'd like to try the OPA2134's, mouser and digikey are both out of them.

[Brian]

What Up, Illacov??
I hear ya man.
I've been looking inside mine and did quite a bit of mod, I think that the two caps in the audio path on the inputs will make a big difference and removing HF if you need the high is too easy.
That PS mod is the biggest deal, that make a lot of difference. I put a polypro on the input and it sounds beefy I bet a polystyrene would work for tooby clarity, film for sheen, PolyPro for 3D-ness. COG for razor's edge, electro for fatness. You could build a combo. do that every now and then.
Check back in the thread and get the proper schematic if you didn't already, the one on the DBX site is way off.

[illacov]

What Up, Illacov??
I hear ya man.
I've been looking inside mine and did quite a bit of mod, I think that the two caps in the audio path on the inputs will make a big difference and removing HF if you need the high is too easy.
That PS mod is the biggest deal, that make a lot of difference. I put a polypro on the input and it sounds beefy I bet a polystyrene would work for tooby clarity, film for sheen, PolyPro for 3D-ness. COG for razor's edge, electro for fatness. You could build a combo. do that every now and then.
Check back in the thread and get the proper schematic if you didn't already, the one on the DBX site is way off.

Dude walk me through this regarding the caps on the inputs.

Which caps are they?? I already switched the 470uf to 1000uf 35V.

I will probably end up with film caps once you tell me what to switch out and to replace with what values?? I can do this today hehe. The ceramics I probably won't touch and regading that whole bypassing bit, that PCB is in there really tight as it is. Won't those caps even if you have em flat, make the profile too tall to fit??

Either way lets stick to the easy stuff, the caps in the audio path you speak of on the input. What are they labeled as and what values would you recommend replacing em with??

Thanks man!
This will probably work for my 263x, which I didn't mod yet.

Awaiting with reckless abandon and a hot iron.

I do see a promising cap at C1 the 120pf and at the C5 position 3.3uf in the pathway to the 1252 vca. Are these the caps you speak of? The caps I'm looking at the output besides these are the .1ufs. But those are bypass caps right??

Peace
Illumination

[Brian]

What Up, Illacov??
I hear ya man.
I've been looking inside mine and did quite a bit of mod, I think that the two caps in the audio path on the inputs will make a big difference and removing HF if you need the high is too easy.
That PS mod is the biggest deal, that make a lot of difference. I put a polypro on the input and it sounds beefy I bet a polystyrene would work for tooby clarity, film for sheen, PolyPro for 3D-ness. COG for razor's edge, electro for fatness. You could build a combo. do that every now and then.
Check back in the thread and get the proper schematic if you didn't already, the one on the DBX site is way off.

Dude walk me through this regarding the caps on the inputs.

Which caps are they?? I already switched the 470uf to 1000uf 35V.

I will probably end up with film caps once you tell me what to switch out and to replace with what values?? I can do this today hehe. The ceramics I probably won't touch and regading that whole bypassing bit, that PCB is in there really tight as it is. Won't those caps even if you have em flat, make the profile too tall to fit??

Either way lets stick to the easy stuff, the caps in the audio path you speak of on the input. What are they labeled as and what values would you recommend replacing em with??

Thanks man!
This will probably work for my 263x, which I didn't mod yet.

Awaiting with reckless abandon and a hot iron.

I do see a promising cap at C1 the 120pf and at the C5 position 3.3uf in the pathway to the 1252 vca. Are these the caps you speak of? The caps I'm looking at the output besides these are the .1ufs. But those are bypass caps right??

Peace
Illumination

(most important)= C1 & C2, these could be polypro, or combinations, better quality and "around" the same value added up.
(not as important) C5, C6, C12, polyesters will do well,
hf suppression = (input)C3 & C4, (output) C8 & C9, these could be removed, but, do it "in situe" and you could lessen the value and keep it in, use ceramics if you do. Not sure a smaller value COG would be any benefit.
and it seems like if your going to change the opamps, the 5534 and the 353 are the two to improve. 5534 is a fine opamp. The 353, maybe not so much, but, I have no problem with it.
This will get rid of the "boxiness" that DBX is famous for and that will give it a wider bandwidth sound.

[illacov]

Thanks man!

Did you take out your HF suppression completely??

I wonder what the stock vca and opamps sound like without it.

I'm looking at the 263x guts right now and it pretty much mirrors the 163x in places.

I wonder why the de esser needs HF suppression in addition to the hf suppression the actual de esser adds??

Hmm...I wonder.

Any body have ideas on what to do with the 263x?? Exact same as the 163x?

Thanks Brian!

Peace
Illumination

[Sean Sullivan]

OA3 and OA4 is the side chain control.

Replacing OA1, OA2, and IC1 are going to clean up the noise.

I replaced all the electrolytics because they are probably 20+ years old. If you install a 2180 you need to remove R9 and R10.

[Brian]

Thanks man!

Did you take out your HF suppression completely??

Nope, just took it down a few notches.

I wonder what the stock vca and opamps sound like without it.

The high end is extended a little further up and it's fairly smooth.

I'm looking at the 263x guts right now and it pretty much mirrors the 163x in places.

I wonder why the de esser needs HF suppression in addition to the hf suppression the actual de esser adds??

Hmm...I wonder.

Probably how it accomplishes the de-essing.

Any body have ideas on what to do with the 263x?? Exact same as the 163x?

Thanks Brian!

Peace
Illumination

[illacov]

OK now its on!!

I took out the hifi suppression completely, replaced C2 with a new mylar film cap of the same value, as before mentioned I replaced the 470uf PSU caps with 1000uf 35v and this thing KICKS ALL TYPES OF ASS!!

The 263x went like at least 10 db quieter with upgraded PSU caps!

I want to buy another 163x and change out the VCAS and opamps so I have the pristine version.

Thanks a shit ton guys! Hats off to Brian for keeping the crusade rolling at Gearslutz and over here on Tape Op!

Peace
Illumination

[Sean Sullivan]

If you are considering upgrading to 2200uF, the Nichicon HE series are too tall. Maybe Panasonic FM will fit?

Here's a complete list of what I did to mine:

Replace R2 with a 100K Dale RN55 (mouser.com)
Replace OA1 with LME49860 (digikey.com)
Replace OA2 with LME49710 (digikey.com)
Replace IC2 with THAT 2180A (mouser.com)
Replace C13 and C15 with WIMA MKS-2 10uF polyester caps
Replace C5 with WIMA MKS-2 3.3uF
Replace C28 and C29 with Nichicon HE 1000uF electrolytic cap
Replace C30 and C31 with Nichicon HE 6.8uF cap
Replace C32 and C33 with Nichicon HE 33uF cap
***Bypass the caps with WIMA MKP-2 .01uF polyprop cap***
Replace C12 and C16 with WIMA MKP-2 .33uF polyprop cap
Replace C17 with WIMA MKP-2 .068uF
Replace C2 with .WIMA MKP-2 .1uF

I also replaced all the HF caps with .1uF mono ceramic caps, when I removed them from the circuit I got oscillation. All WIMA's are available from Mouser. Nichicon caps are available from Mouser and Digikey.

[Brian]

If you are considering upgrading to 2200uF, the Nichicon HE series are too tall. Maybe Panasonic FM will fit?

Here's a complete list of what I did to mine:

Replace R2 with a 100K Dale RN55 (mouser.com)
Replace OA1 with LME49860 (digikey.com)
Replace OA2 with LME49710 (digikey.com)
Replace IC2 with THAT 2180A (mouser.com)
Replace C13 and C15 with WIMA MKS-2 10uF polyester caps
Replace C5 with WIMA MKS-2 3.3uF
Replace C28 and C29 with Nichicon HE 1000uF electrolytic cap
Replace C30 and C31 with Nichicon HE 6.8uF cap
Replace C32 and C33 with Nichicon HE 33uF cap
***Bypass the caps with WIMA MKP-2 .1uF polyprop cap***
Replace C12 and C16 with WIMA MKP-2 .33uF polyprop cap
Replace C17 with WIMA MKP-2 .068uF
Replace C2 with .WIMA MKP-2 .1uF

I also replaced all the HF caps with .1uF mono ceramic caps, when I removed them from the circuit I got oscillation. All WIMA's are available from Mouser. Nichicon caps are available from Mouser and Digikey.

I like the R2 replacement, gonna have to look into that too.

SOOOO, how does it sound?
How does it work for you now?

[Sean Sullivan]

I'm still waiting on a couple parts (resistor, some caps) so I'll give a full report soon. Because Mouser charges a pretty penny for shipping and Digikey has a minimal order, I probably won't finish on the first week of December because I'm going out of town. I've got a couple DBX 160A's and a pair of Aphex 651's I'm going to do next. I'm waiting on Jim to send me back one of Aphex's he modified and I'm going to try to replicate what he did (but I'm not going to share that online).

[Brian]

If you are considering upgrading to 2200uF, the Nichicon HE series are too tall. Maybe Panasonic FM will fit?

I laid mine on their sides cleverly.

I also replaced all the HF caps with .1uF mono ceramic caps, when I removed them from the circuit I got oscillation. All WIMA's are available from Mouser. Nichicon caps are available from Mouser and Digikey.

Did you need to remove them? Could you just reduce he value till the oscillation stopped?
Maybe .001 instead.

[The Scum]

By HF caps, are you talking about the dozen or so .01uf caps that hang on the legs of each IC?

Those aren't HF suppression, filtering, or anything of the sort. They should have minimal effect on the audio bandwidth of the unit.

They're what I'd call "local supply decoupling." They hang across the power rails were they enter the chips, so that there's a little reservoir of current that the chip can draw when transients come along. It allows the chip to get that current from nearby, and not have to fight against the series inductance and resistance of the PCB traces (a parasitic lowpass filter) to get it.

Apparenty, they're essential to the stability of the circuit...which probably gets worse when you put "better" opamps in it...they're faster, so more prone to misbehave. They'll keep things stable, and possibly help the transient response. Making them bigger, and using better quality caps will only help the circuit. Kemet Gold Max X7R or NP0 meet the bill.

It has nothing to do with a HF roll off on the audio path.

[Brian]

Nope, just meant the ones on the opamps and only the hf suppression. I don't have the schematic handy, but, I think it's a .0068 ceramic cap.
On those decoupling caps, I have heard about people using polypros, but, I would think a ceramic would be better as long as it was good enough.
Is COG better?