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Stitch333
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#1
20th December 2006
Old 20th December 2006
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DBX 118 Mod

So Ive been goin through the old gear I have in the studio in my spare time, replacing bad caps, testing cables, etc. and I got to my DBX 118. I love this old box, my friend got at a garage sale a couple of years back for $3. But the bass response was always noy so good. Serious mud... not to mention the comp itself is almost too slow to be truley useful but other than that, its got some killer DBX vintage comp sound.
I cracked open the case the other day and noticed 4 8pindip IC chips on the PCB. I think (could be very wrong) 2 x IC for the stereo VCAs, 1 x input, 1 x output.
Couple a minutes on google and I was able to find updated chips for each of the points.
5 days later, chips from digikey came, swapped out the ICs...
The thing sounds GOOD. Not great, granted, but definitely usable. The Compressor is much faster arresting transients and everything below 100hz has become way more defined. This is a real cheap way to have a halfway decent comp for pennies (I think I have $15 invested).
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Stitch333
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21st December 2006
Old 21st December 2006
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OA2 TI RC4560

OA3 TI RC4560

OA4 AD 712

OA5 LM 301AN

if anyone wants to try...
#3
21st December 2006
Old 21st December 2006
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Cool idea, I'll definitely try this with mine, thanks for sharing.
#4
21st December 2006
Old 21st December 2006
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Quote:
Originally Posted by Stitch333 View Post
OA2 TI RC4560

OA3 TI RC4560

OA4 AD 712

OA5 LM 301AN

if anyone wants to try...
That's great, thanks!
Are the chips listed here in order of VCA, Input, Output?
Thanks for the info.
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21st December 2006
Old 21st December 2006
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Quote:
Originally Posted by jarbar View Post
That's great, thanks!
Are the chips listed here in order of VCA, Input, Output?
Thanks for the info.
Honestly, I just looked at the PCB. If you crack the 118, you'll see 4 sockets labeled OA2, OA3, OA4, OA5 on the PCB next to the chip sockets. Replace as mentioned above. As a disclaimer, I didn't have the schematic so I merely researched chip upgrades by model number as recommended. I believe the LM301AN at OA5 is the same that was in there before but I replaced it anyway. If anyone has chip recommendations or other mods we can do to a 118, Im down fer some frankenstein soldering...
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21st December 2006
Old 21st December 2006
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None of those chips are VCAs. The 4560s are dual op amps, crappy ones. The 301 is a single op amp, alsp crap but probably not in the audio path. The AD712 is also a dual op amp, one I'm not familiar with although it is made by Analog Devices and they mostly make good stuff. But it kind of depends what you're doing with it. In any case, the selection of these amps will have no effect at all on the compression attack or release times. There are going to be some capacitors and resistors that could get replaced if you wanted to change the timing. Anybody got a schematic?
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Stitch333
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21st December 2006
Old 21st December 2006
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Quote:
Originally Posted by ulysses View Post
In any case, the selection of these amps will have no effect at all on the compression attack or release times. There are going to be some capacitors and resistors that could get replaced if you wanted to change the timing. Anybody got a schematic?
compressor performance increased (maybe frequency response? Im not being very scientific about this). Personally, I instantly noticed the bass resolution increase and the dynamics were defined better consequently. Got any suggestions for a better chip than the 4560s or the 301?
#8
21st December 2006
Old 21st December 2006
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Keep in mind that the upc4560 opamp is the chip that made Mackie famous...

Do install either a National LM4562, LT1358 or even a BB OPA2134. Your ears will thank you. Get'um from Digi-Key.

Jim Williams
Audio Upgrades
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21st December 2006
Old 21st December 2006
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Quote:
Originally Posted by Jim Williams View Post
Keep in mind that the upc4560 opamp is the chip that made Mackie famous...

Do install either a National LM4562, LT1358 or even a BB OPA2134. Your ears will thank you. Get'um from Digi-Key.

Jim Williams
Audio Upgrades
Thanks Jim, Ive read some of your posts...good s**t!

National LM4562, LT1358 or even a BB OPA2134 in place of the 2 x 4560's? I have a bunch of the 2134s and some linear technology chips floatin around here somewhere, i'll play around and post some results.
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22nd December 2006
Old 22nd December 2006
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hello,

here's the schematic !!

I also have a dbx 118 and want to make some mods...

first of all I wouldn't change the vca's because they're part of the vintage-sound...
(the same type as used in the dbx 162)

I think I'll build a balancing stage using the new that ic's (line receiver 1206 and line driver 1646) or as an alternative ti drv134 and ina137

a new power supply for better stabilization

change oa3 to opa2134 or opa2227 or opa2604

change oa4 and oa2 to a low noise opamp

increase c7 and c16 to 4,7µF

connect line driver circuit at r34 and r8
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DBX 118 Mod-dbx118.gif  
Stitch333
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22nd December 2006
Old 22nd December 2006
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Quote:
Originally Posted by matthias View Post
hello,

here's the schematic !!

I also have a dbx 118 and want to make some mods...

first of all I wouldn't change the vca's because they're part of the vintage-sound...
(the same type as used in the dbx 162)

I think I'll build a balancing stage using the new that ic's (line receiver 1206 and line driver 1646) or as an alternative ti drv134 and ina137

a new power supply for better stabilization

change oa3 to opa2134 or opa2227 or opa2604

change oa4 and oa2 to a low noise opamp

increase c7 and c16 to 4,7µF

connect line driver circuit at r34 and r8
Wow, thanks man!

Just a couple of questions (now that I can look at the schematic):
-the c7 and c16 values you are talking about changing to 4.7uf are at 100V?

-I wonder why on my 118 oa2 and oa3 were matched 4558s (upd to 4560s) when on the schematic its oa2 and oa4 that have matched 4558s...any suggestions fer yer oa4 and oa2 chip to replace the 4558?

-With the THAT parts, are you talking about building a balenced Input/output stage with XLR I/O on the back? A balenced line stage would be cool.

the VCAs are the best part...

Thanks again, y'all
#12
22nd December 2006
Old 22nd December 2006
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Quote:
Originally Posted by Jim Williams View Post
Keep in mind that the upc4560 opamp is the chip that made Mackie famous...
They made some of the Peavey boards similarly famous. That thing has to be the worst sound device I've ever heard.
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22nd December 2006
Old 22nd December 2006
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Quote:
Originally Posted by sekim View Post
They made some of the Peavey boards similarly famous. That thing has to be the worst sound device I've ever heard.
still better than the stock 4558 in the 118.
Stitch333
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23rd December 2006
Old 23rd December 2006
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but not near the 2134. I just swapped out the oa2 and oa3 RC4560's with 2 x opa2134. Its noticeably even more defined through the bass but I think there is a better fitting modern chip for the 118 design.
#15
2nd January 2007
Old 2nd January 2007
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I'm looking to swap the chips in my 118 soon and this thread has been great. Any new developments or experiments? I'm going to order some soon so I thought I'd ask.
Thanks a bunch and happy new year.
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10th January 2007
Old 10th January 2007
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Quote:
Originally Posted by jarbar View Post
I'm looking to swap the chips in my 118 soon and this thread has been great. Any new developments or experiments? I'm going to order some soon so I thought I'd ask.
Thanks a bunch and happy new year.
I just ordered caps from Digikey. My 118 gets more use now but Im going to recap the piece as it definitley old. Stuck with the 2134s, they are good. When I get some time Ima run through some of Matthais' idears...esp piecing out an new PS. Dont think I'll build a balenced line stage as I have too much on my plate already. You do anything like you been talkin boot Matthais?
#17
11th January 2007
Old 11th January 2007
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no, not really... but balancing with drv134 and ina137 isn't a big deal at all...
#18
11th January 2007
Old 11th January 2007
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4558 is nice sounding dev ice if to bias outputs properly.
#19
11th January 2007
Old 11th January 2007
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What type of capacitor did you use for C7, C16? Polycarbonate types are good, but a metalized polypropylene is better. You might try direct coupling to see if the bass gets better. Check for a DC offset from whatever is going in first. Miniscule offset means no need for the degradation from an extra cap in the signal path.

C5 and C9 are also in the signal path and are in dire need of replacement . If there is room, a low voltage, metalized polyprop is best, otherwise use a Black Gate (type N, NX, or NX HiQ).

The power supply capacitors need replacement too, and the post-regulator one, C4 needs replacement. Best would be a metalized polyprop bypass on an electrolytic. There's lots of room for discussion on types of 'lytics and values, but need for an upgrade is not. Changes here will help the bass.

Just about every capacitor is ripe for replacement, actually! The schematic notes imply that most of the caps in filters are ceramic. Better would be polystyrene or polypropylene film/foil. If the ceramics are C0G types, they may be OK.

For $3 you got yourself a lot of work to do!
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12th January 2007
Old 12th January 2007
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Quote:
Originally Posted by Wavebourn View Post
4558 is nice sounding device if one bia's the outputs properly.
Yes, they will do well driving meters. THD doesn't much matter there.

Anyone considering using one for high quality audio is suffering from Rip Van Winkle syndrome. Wake up.

Jim Williams
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#21
15th January 2007
Old 15th January 2007
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Quote:
Originally Posted by Jim Williams View Post
Anyone considering using one for high quality audio is suffering from Rip Van Winkle syndrome. Wake up.

Jim Williams
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True, this thing is not high quality audio, but I was using it this weekend for some home recording and it was doing some wonderful things to room mics!
My is still the stock version, but I'm up for any cheap and easy way to improve the sound quality (but the compression circuit I'm happy with). I'm definitely going to try out some of the chips mentioned earlier in this thread. Thanks
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15th January 2007
Old 15th January 2007
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Quote:
Originally Posted by Jim Williams View Post
Yes, they will do well driving meters. THD doesn't much matter there.

Anyone considering using one for high quality audio is suffering from Rip Van Winkle syndrome. Wake up.

Jim Williams
Audio Upgrades
I started this thread in low end. Not everyone has an arsenal of knowledge and gear at their fingertips, my man.
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15th January 2007
Old 15th January 2007
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Quote:
Originally Posted by markk02474 View Post
What type of capacitor did you use for C7, C16? Polycarbonate types are good, but a metalized polypropylene is better. You might try direct coupling to see if the bass gets better. Check for a DC offset from whatever is going in first. Miniscule offset means no need for the degradation from an extra cap in the signal path.

C5 and C9 are also in the signal path and are in dire need of replacement . If there is room, a low voltage, metalized polyprop is best, otherwise use a Black Gate (type N, NX, or NX HiQ).

The power supply capacitors need replacement too, and the post-regulator one, C4 needs replacement. Best would be a metalized polyprop bypass on an electrolytic. There's lots of room for discussion on types of 'lytics and values, but need for an upgrade is not. Changes here will help the bass.

Just about every capacitor is ripe for replacement, actually! The schematic notes imply that most of the caps in filters are ceramic. Better would be polystyrene or polypropylene film/foil. If the ceramics are C0G types, they may be OK.

For $3 you got yourself a lot of work to do!
Panasonic and BC...Im checking out the Black Gates now.
Still need to find 2 x 22uf 16v at c2 and c3 on the VCA boards.
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16th January 2007
Old 16th January 2007
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Quote:
Originally Posted by Stitch333 View Post
I started this thread in low end. Not everyone has an arsenal of knowledge and gear at their fingertips, my man.
Got news for you, we ALL started out that way, empty minds of mush.
That's why I post the information here, for your education. Smart folks will learn from it, the others will take the longer path to figure out stuff on their own.

Your call.

Jim Williams
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#25
16th January 2007
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C'mon the 118 119 117 whatever , sound mojo!

for what they are / do!

not every piece should be homogenized!

uses .......uses....

upgrading components can be fun, but the beauty of this piece is what

it "sounds" like , its imperfections.

On the other hand this thread tempts me buy another and mess with it, improve

some components then that one would be for that kind of sound!
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16th January 2007
Old 16th January 2007
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Quote:
Originally Posted by Jim Williams View Post
Got news for you, we ALL started out that way, empty minds of mush.
That's why I post the information here, for your education. Smart folks will learn from it, the others will take the longer path to figure out stuff on their own.

Your call.

Jim Williams
Audio Upgrades
Jim, I just wanna thank you and all the other technical cats on this part of the board for sharing the info that makes one realize how long the path can be. I respond to comments in kind, tho. Call me mush-mouth.....for now.
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16th January 2007
Old 16th January 2007
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Quote:
Originally Posted by mahasandi View Post
C'mon the 118 119 117 whatever , sound mojo!

for what they are / do!

not every piece should be homogenized!

uses .......uses....

upgrading components can be fun, but the beauty of this piece is what

it "sounds" like , its imperfections.

On the other hand this thread tempts me buy another and mess with it, improve

some components then that one would be for that kind of sound!
This is the reason you install IC sockets. You then have a choice, old or new.

Jim Williams
Audio Upgrades
#28
16th January 2007
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Yeah true but i'am lazy.

Once its sitting there i don't want to open it up and swap.

I'd rather have another like i said..
I guess i'am no geekslut.
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#29
9th February 2007
Old 9th February 2007
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For anyone who cares: Thot Id do an update on this thread. Got my panasonic HFS series caps. redid the VCA, RMS, etc...I guess it goes without saying that a 30 year old piece of gear benefits from the replacing of caps...still waiting on the 470uf PS caps, but its still yet another improvement. Once I can finish, I'll try and get some sound samples up.
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23rd August 2007
Old 23rd August 2007
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Hey all,

FYI - I swapped out my PSU trafo for a toroidal and dropped a BB OPA2134 in OA3.

Night and day... The one word I'd use to sum it up is "detailed".
The old op-amp slushed things around a heap, now the top is airy and alot cleaner. It hasn't affected the bottom much but I am going to recap the PSU which I've heard helps...

Very happy. I have a second one I will put an OPA 2604 in for something different. These boxes definately aren't "hifi" but a mod like this moves them out of the "effect box" bin and into something you could use more regularly.
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