dbx 160vu clone

[Biasrocks]

I would prefer to keep it as original as possible.

For instance, it would be nice to keep the duals as they are
way more options available for upgrading if one wants to experiment.

You are treading on ground that has been covered in the forum previously. I have
a number of documents relating to the RMS, VCA circuits including PCB layouts
that I can forward to you.

Also, the meter is in 160 is a custom job, I believe it's a center resting meter.

Any idea how you're going to address that?

Mark

 

[damnyankee]

Jim Williams is an expert on dbx compressors.  He has posted a number of the mods he does to open it up (think of flying in a plane and your ears unpopped vs popped):

1. to reduce psu noise (as in silent), he recommends "ditching the 470uf mains caps and going to 4,700uf 35v FM's and use a bead of hot glue."

2. "To replace the 22 uf post regulator caps I use 220 uf FM's."

3. "I replace the 470 uf mains caps with 4700 uf 35v FM's. The 22 uf post regulator caps I use 220 uf FM's. The 4.7 uf bipolar is replaced with a Wima MKS-2 bypassed with a .01 MKP-2. There are a couple of others like a 100 uf on the mute circuit, change them all. Then there are those LF353 and LM301 opamps..."

4. "As to those 353 and 301 opamps, if you install quality sockets you can play with the opamps. The 353 just plugs in the front end and I/V stage. The 301 is used on the outputs. Lift up pin's 1 and 8 and solder a 30 pf cap across them. Then you can plug it in for that 1975 flavor."

5. "You can try a LT1358CN8, LME49720NA, AD8599 on a S0-8 to dip adaptor. You will need to add a 22 pf cap across the feedback resistor on the input opamp. I also add a 10 pf across the B side of the second 353 opamp around the VCA. Also add a couple of .1 uf  mono ceramics from pins 4 and 8 to ground.

"For the 301, I use a LME49870MA on a S0-8 to dip adaptor. Remove the 30 pf cap from pins 1 and 8. It runs on + - 22 volts so replace the 2.2k 24 volt dropping resistors to 330 ohms. That brings up the power rails to + - 21 volts adding some additional output headroom. It's also precision so no DC offset voltage."

 

[Biasrocks]

Jim Williams is an expert on dbx compressors.

I'm not sure even Jim would agree with that statement.

I'll say this, he's an expert at upgrading many pieces of gear and a hell of a cool guy to talk to.

He has posted a number of the mods he does to open it up (think of flying in a plane and your ears unpopped vs popped):

Not everyone wants their ears to pop when they use a dbx160.

It has a sound, it's been used on thousands of records in it's stock form, there's a good reason why that is,

It has a SOUND.

Besides, if you start with the original, anyone can follow Jim's directions and "upgrade" their clones.

Mark

 

[abechap024]

Interesting Mark,
The center resting meter will have to be something that will need to be addressed. As soon as we get a working pcb maybe someone card prototype it and we'll go from there. Worst case we 'll have to change the meter circuit a bit to work with a standard VU. But It seems we want to keep it stock as possible. Thanks for the info
AC

 

[bruno2000]

anyone know dimensions of the pins for the modules?
Thx
AC

Here's the pins in the 200 VCA (this 200 VCA is from a dbx 119). Looks to me like the size of the component leads:

http://www.gearslutz.com/board/attachments/geekslutz-forum/36110d1181243868-dbx-128-inside-vca.jpg

The VCA pins are 0.042" in diameter.  Hope this helps!
Best,
Bruno2000

 

[abechap024]

Thanks Bruno2000! that does help. Also any chance of the foot print measurements? 

 

[bruno2000]

Thanks Bruno2000! that does help. Also any chance of the foot print measurements? 

All I have out right now are some 202s and 204s, which, I believe, are different size.  If I get time, I'll pull out a 160VU and measure for you, but those things are a PITA to take apart.
Best,
Bruno2000

 

[damnyankee]

Hi Mark,

Thank you kindly for your generous offer to forward the vca, etc docs.  May I have a copy?  sevenfoldguitar at yahoo dot com.

As for meters, musicianservice dot com may still have some NOS meters in stock.

 

[bruno2000]

I had to replace a meter in a 165 (not quite the same, but almost).  IIRC it was over $100 from MSC.
Just sayin'
Bruno2000

 

[abechap024]

WOW, I wonder what makes the meter so damned expensive. You know a meter is just a luxury - haha there are those LEDs and your ears come on what more do you need! 

 

[emrr]

Any real meter is expensive.  Most people don't use real meters that meet official specs.

 

[abechap024]

ok so making a PCB is much more a pain in the ass than i realized. Makes me grateful even more to the people on here that have made all these great projects so far. Thank you guys!
I just need the footprint of the rms and vca modules then I can seriously start the component placement. i've been fooling around with it for a while, but no real poiint until I have all the sizes...
any thoughts on transistor substitutes?
AC

 

[damnyankee]

Thank you for your efforts, AC - there's a group of us who are greatly appreciative of your efforts.  I tried to do this PCB and couldn't - I just don't have the expertise.  I would also like to do the Rockman Instrument EQ, Rockman Stereo Echo, and Rockman Stereo Chorus but again, I don't have the expertise.

I remember someone on the other board posted these transistors are still available.  If that's not the case, I don't know how reliable a source this is, but this may be of help:

BC 173 replacements: BC 169, BC 184, BC 239, BC 549  (source: http://english.electronica-pt.com/db/cross-reference.php?ref=BC173)
BC 263 replacements: BC 241, BC 259, BC 309, BC 559  (source: http://english.electronica-pt.com/db/cross-reference.php?ref=BC263)
BC 361 replacements: BC 161, BC 303...304, BCX 60  (source: http://english.electronica-pt.com/db/cross-reference.php?ref=bC361)
KE4858 replacements: used for output muting and there are no replacements.  

Regarding the dbx 160/161 VU's (4) KE4858's per Jim Williams: "I wouldn't waste any time on that [finding a replacement], the output mute circuit is not needed and will add THD to the signal, it's best not to lay a bunch of leaky fets across the outputs anyway. If you don't attenuate the next piece in line when you power up, you will learn to, just as you do with lot's of other gear."

I hope that helps...

 

[damnyankee]

Any real meter is expensive.  Most people don't use real meters that meet official specs.

I guess why couldn't we use these?  I'm sure we could buy "replacements" from dbx or their distributers...???

http://www.gearslutz.com/board/attachments/high-end/154244d1264116551-dbx-160s-bashers-thank-you-ever-so-much-dbx-160-sl-blue206537767_o.jpg

 

[abechap024]

Thanks damnyankee.
thats good to know that we don't need the ke4858s. I think that would eliminate a lot of parts and parts...I'm still learning myself...hopefully someone smarter than us takes a look at the schematic and tell us what parts we can eliminate! haha I'm still in my first year of EE.

I'm guessing
r100
c30
c31
c32
r93
r101
q5
r99
r96
r97
r98
c25
cr15

 

[damnyankee]

Hopefully someone here will be able to say for sure.  I'd hate to ask Jim for help - he's given me (and many others) so much free help on these dbx compressors already.   In the "dbx 160 comp/limiter" service manual schemo (http://www.dbxpro.com/product_downloads/Service_Manuals/160-161-162%20Service%20Manual.pdf - the last page I think), I would consider eliminating:

BC261
C29 (250v 1uf)
C30 (25V 100uf)
C31 (3.3nf)
CR18
Q10 (KE4858)
Q11 (KE4858)
Q12 (KE4858)
Q13 (KE4858)
R96 (10k)
R97 (1k)
R98 (1M)
R99 (10k)
R100 (15M 10%)
R101 (3.3M 10%)

Anyone???

 

[abechap024]

here is what I've eliminated from the mute circuit. You know wouldn't that be a bitch of some of the magic was in that fet distortion...

 

[damnyankee]

You eliminated the components I thought were part of that output mute node.  However, I'm only an amateur.

And AC: you've done a killer job!!!

 

[abechap024]

right, thats what were getting rid of right? the output mute circuit...
and thanks, i'm trying my best...It will be exciting if it actually works
AC

 

[damnyankee]

The magic isn't from the output mute jfets...don't worry about that.  You just eliminated a trouble shooting issue because when a KE4858s goes down, it distorts/lowers output volume.

As for the board itself, I'm interested to see how you're going to tie in the power supply/power rails with Eagle.

Ya know, if I had a dbx 160VU, I would make a scan of the bottom of the pc board so you wouldn't have to fiddle around with Eagle.  I could easily create the images of the board for etching.  However, I don't have a dbx 160VU tho. *sigh*  I guess on the bright side, you're getting some practice with Eagle and it'll come in handy with your future projects (like a valley people dynamite *haha*).  Again, a HUGE thank you for your efforts!