dbx 160vu clone

[damnyankee]

Using NTE replacements is.....   Take handfull any BCxxxC , select and match hfe Ube , and You have exellent replacements for VCA200 and RMS208.

Thank you, arska. 

I'd like someone to double check those NTE cross references to ensure they are direct replacements to the original BCxxx's.  The crappy power supply and the RMS detector contributes to the mojo in the 160VU and I want to be sure we don't lose any mojo. 

Arska - would you mind being an extra set of eyes and double check the BCxxx cross reference to NTExxx for us?

DY

 

[matthias]

???  you want to keep the crappy power supply. but increase the caps to remove noise??

The crappy power supply and the RMS detector contributes to the mojo in the 160VU and I want to be sure we don't lose any mojo. 

have you ever heard that what you call the "mojo" of the dbx 160 ??

 

[matthias]

here's a pic of the dbx 160 pcb

dbx160-pcb.JPG

 

[damnyankee]

Matthias, I don't have a 160VU; but I do have 119's.  Do the swap then A/B your two units.  Then re-ask me the question.   ;D

 

[damnyankee]

here's a pic of the dbx 160 pcb

dbx160-pcb.JPG

Matthias,

Thank you VERY VERY much for completing my dbx 160 files!  You da man!

DY

 

[matthias]

ok, here's a schematic of a "modern" rebirth of the old "160" ... that's how I would do it...

dbx 160 - 2010.pdf

and of course I would get rid of the old power supply and use something modern.

for the led gr-metering I suggest the 20-led gr meter of the picocomp

 

[arska]

KE3687 = 2N3687  working replacement  J201,  RMS208 BC453C  I used BC550C

 

[damnyankee]

KE3687 = 2N3687  working replacement   J201,  RMS208 BC453C  I used BC550C

Thank you, arska.

Just so I have this correct in my very simple mind:

J201 replaces KE3687,2N3687? (those J201's sound killer in those tube amp simulated guitar pedals by the way)
BC550C replaces BC453C in the RMS can? 

Correct?

 

[arska]

Correct! yes.


There´s errors in the schematics of RMS208, RMS209 and VCA200!!!!!!!!!! Even in DBX manuals (DBX160vu hand drawn pictures of RMS208/209).


 

 

[arska]

Matthias, there will be a problem in control voltage of 2180 in your schematic.
1. use pin 2  instead of pin3, control voltage to EC+
2. voltage divider 200ohm/200ohm will drop control voltage to half!!!! Use buffer amp (5534A ) for 2180vca

I have tested prototype on my desk, built with modified rms208, THAT2180vca and 100uA moving coil meter for G.R metering ( or 20led bar meter )
Schematic is in pdf format, I can email it..... 
 

 

[matthias]

schematic updated...

dbx 160 - 2010 2.pdf

 

[damnyankee]

Wow Matthias...is that all there is to the modified circuit?!!! 

And I have just a general electronics question as I'm pretty much a simple guitar pedal builder: I noticed in circuits there are caps/resistors in the audio path that go to ground.  Is that to tame frequencies, remove oscillations, etc in the audio path???

Thanks much!

DY

 

[abechap024]

Very Awesome guys!
great circuits. Arska, you say there are mistakes in the VCA/RMS circuits? Could you could email the working schematics to both. abe (at) acsoundstudio(dot)com
That would help me a million. also you said you have a working prototype. Is it of the original 160? if so how does it sound etc...any pointers on ways you would do it
Thank you guys!

Matthias I love your simple approach! That is the circuit! I bet that it will sound cleaner/better then the original!! I am only afraid that by making it sound "better" we are loosing something in the process. But then again It might just sound...better!
DamnYankee the caps your see to ground are for the power supplies and for the chips to help stabilize them and last but not least the Timing in the RMS unit.

You guys rock!
AC

 

[damnyankee]

AC:  just so I understand (I have built only battery powered pedals):

AC enters the transformer; the transformer converts to DC.  The main caps are grounded and serve several functions:

1.  they remove residual AC and its ripple from getting in the audio circuit. 
2.  they smooth DC voltage. 
3.  they are large in uF value to have low reactance in all frequencies; but as caps are not created equal (and some are better than others), the highest quality caps should be used here (because these caps are really what we are listening to and affect frequencies we hear). 

Is this correct?

Secondly, I understand the point of using resistors in a circuit (control the flow of current to other components) but I've never quite understood the point of grounding resistors???

Now onto the dbx 160VU clone...

I trust the THAT VCAs with "sound better" means - to coin a Jim Williams phrase: "it's like taking saran wrap off a speaker"...or "removes the fog"...or "when your ears pop in an airplane".  In other words, I hope the 160VU mojo sound will be even clearer to the ear.  However, I am mindful of what Les Tyler/dbx once said how the crappy power supply contributed to the unique sound. 

Matthias: how does your prototype with different power supply compare to your old 160VUs?

Thank you very much - I'm getting quite an education!!!

DY

 

[abechap024]

Hi DY,
Yes you are right about the capacitors removing noise and ripple. They also act (to some extent) as little batteries for when the op amp or whatever needs more current. Also Power supply caps are not as important quality wise as the capacitors you will be putting in your direct audio path (to control DC voltages in the AC signal )
I'm working on the Power supply right now, and it is such a weird power supply! I have never seen anything really like it. Why so many transistors?? haha it almost looks more like a discrete op amp than a power supply.

I think while Matthias approach is the easiest, we want to do everything we can to recreate the vintage 160 mojo.

So here is a list of the things I think are probably most important we keep as to avoid changing the sound and while probably more than a few could be changed out without too much of a change I would just rather err on the side of caution:

208 RMS circuit
200 VCA (that)option
Weird/Awesome power supply (yes DY you've finally convinced me...)Total pain in the ASS. uses old 723 regulator can'r read the pin outs and been trying to fandagle this for the past hour. I've come to the conclusion that people can make their own power supply. DY, there are tons of easy power supply schematics and PCBS out there. Much easier then trying to build this old old power supply. The only way i could imagine it having effect on the sound would be if it "sags" a little bit. But all that is going to do is dull the transients. i'm just going to leave the jumpers on the PCB so anyone is welcome to use whatever power supply they want.


and last but not least we should keep the Discrete output stage

Something I want to maybe make it easy to add on if someone so wishes is different Timing circuit caps and an option for a 5meg or so Pot in place of the timing resistor. Options of course and I am probably thinking out loud and getting ahead of myself.
AC

 

[damnyankee]

Hi AC,

Does this pin out help??? (click on the image to blow it up):
http://www.national.com/mpf/LM/LM723.html#Overview

By the way, Mouser has 9,200+ LM723's in stock for $0.67: http://www.mouser.com/Search/Refine.aspx?Keyword=LM723

Wrong component.  Here's the correct one for the LM723CH TO-100 can style:

http://www.national.com/packaging/folders/h10c.html
http://www.national.com/profile/snip.cgi/openDS=LM723C
http://www.national.com/mpf/LM/LM723C.html#Packaging

And, they are in stock at Digikey:

http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_cid=sp_014_0310_buynow&site=us&lang=en&%20?Keywords=LM723CH&vendor=14

And, maybe Matthias can help us where each pin on the LM723CH goes.  I tried to compare the pics of top of pcb vs bottom of pcb and I can't read the bottom of the pcb very well...

Does any of this help???
[/quote]

 

[damnyankee]

AC,

Thanks for all your doing - I know it's been a huge job working with Eagle and creating the PCB.

DY

 

[arska]

schematic updated...

dbx 160 - 2010 2.pdf

Here is something to help using 218x / vca200 in same iron.

 

[damnyankee]

Thank you, Arksa!

AC is getting very frustrated with the LM723CH - I am too.  I want to use the original power supply but we need help determining which of the 10 pins go to which components...?

Thanks!

DY

 

[abechap024]

Correct! yes.


There´s errors in the schematics of RMS208, RMS209 and VCA200!!!!!!!!!! Even in DBX manuals (DBX160vu hand drawn pictures of RMS208/209).


 

I would be most interested on what the errors are!
Thank you
Abe