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Project Specific Discussions => Dynamic Processors => Topic started by: [silent:arts] on March 25, 2015, 05:35:11 AM

Title: 903-51X Comp / Limit
Post by: [silent:arts] on March 25, 2015, 05:35:11 AM
(http://www.silentarts.de/DIY/90X-51X/IMG_5605-640.jpg)

Documents:

903-51X schematic (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-Schematic.pdf)
903-51X PCBs (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-PCBs.pdf)
903-51X Parts List (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-PartsList.pdf)
calibration procedure (https://groupdiy.com/index.php?topic=59044.msg870446#msg870446)

Full Kits are available in the White Market (https://groupdiy.com/index.php?topic=39570.0)
Title: Re: 903
Post by: [silent:arts] on March 25, 2015, 05:35:47 AM
(http://www.silentarts.de/DIY/90X-51X/IMG_1636.JPG)
(http://www.silentarts.de/DIY/90X-51X/IMG_1638.JPG)
(http://www.silentarts.de/DIY/90X-51X/IMG_1639.JPG)
Title: Re: 903
Post by: bernbrue on March 25, 2015, 09:30:33 AM
 8)
Bernd
Title: Re: 903
Post by: culteousness1 on March 25, 2015, 10:17:11 AM
Ah, the prototype PCBs have arrived! Nice, Volker!
Title: Re: 903
Post by: Patrick from Davis on March 25, 2015, 03:09:45 PM
I see you picked sonically superior yellow for the PCB's.  Good call.
Patrick

Title: Re: 903
Post by: tzman on March 25, 2015, 03:10:56 PM
Awesome!
Nice to see how you managed to shrink the size! Ow, and are we seeing a little teaser in the background?
Title: Re: 903
Post by: [silent:arts] on March 25, 2015, 03:23:00 PM
First test (without VCA,  just with a jumper wire): passes audio fine, +21,5dB gain.
Without (VCA and) any calibration 0,004% THD in the audio path. Cool.

Anybody knows how to calibrate the 903 correctly?
Can't find anything. However, we will find out ...
Title: Re: 903
Post by: [silent:arts] on March 25, 2015, 03:25:59 PM
I see you picked sonically superior yellow for the PCB's.  Good call.
Patrick, my PCBs are color coded. Yellow needs +/-24V ;-)

Ow, and are we seeing a little teaser in the background?
No. Just my eight slot Backplane with SubD25 only.
Title: Re: 903
Post by: tzman on March 25, 2015, 04:04:05 PM
Anybody knows how to calibrate the 903 correctly?
Can't find anything. However, we will find out ...

I think you can get a lot from the 160X service manual in the Tech Docs section...
Title: Re: 903
Post by: usekgb on March 25, 2015, 10:30:47 PM
I was thinking about taking this on at some point.  I'm glad to see it's in good hands!
Title: Re: 903
Post by: peterc on March 26, 2015, 04:56:27 AM
Very nice! Love the dbx stuff.

Peter
Title: Re: 903
Post by: mitsos on March 26, 2015, 06:35:23 AM
Cool! What's the second pushbutton?  Overeasy toggle?   Can you elaborate on what features you guys are adding?  Very curious!
Title: Re: 903
Post by: gyraf on March 26, 2015, 07:21:25 AM
GREAT idea making the DBX903 for 51X-format!

What do you use for the obscure RMS-converter chip?

Jakob E.
Title: Re: 903
Post by: [silent:arts] on March 26, 2015, 08:34:39 AM
Cool! What's the second pushbutton?  Overeasy toggle?   Can you elaborate on what features you guys are adding?  Very curious!
the 2nd pushbutton is for stereo link. not tested yet. just summes up the CV signals.
further features are the choice of unbalanced output (original), impedance balanced output or transformer balanced output.


What do you use for the obscure RMS-converter chip?
the same dbx used on a daughter PCB: 1 x CA3083, 1 x BC550, 1 x 1N4148 (see attached pic)
Title: Re: 903
Post by: mitsos on March 26, 2015, 10:53:30 AM
cool. Are you going to do the original gold VCA?
Title: Re: 903
Post by: gyraf on March 26, 2015, 11:16:57 AM
Nice! I've only seen 903's with DBX's own obscure semi-pro RMS chip - that sub circuit makes a lot of sense!

Jakob E.
Title: Re: 903
Post by: culteousness1 on March 26, 2015, 02:53:54 PM
Would be great to replace the obsolete CA30823 in the emulation circuit as well  :o
THAT300 series only features 4 NPNs in an array. Don't know of any other array of 5 elements though...
Title: Re: 903
Post by: [silent:arts] on March 26, 2015, 05:23:24 PM
CA3083 are no problem, I can still get them way cheaper than any THAT array.
Looking at the THAT 2252 and THATs product politics I'm not sure how long the arrays will be available ...

Jakob, attached a foto of the dbx replacement. Never have seen any without, and even found some PCB overlays for the 902 with the substitute PCB drawn on top of the 146221.
However, looks like there have been many different revisions, even with 1252 and 1253 ICs.
Title: Re: 903
Post by: Bassniac on March 27, 2015, 01:11:55 PM
Hey

When do you start to sell them? I will be one of you first customers. Then I can finally get rid of my 160A.

Cheers.
Title: Re: 903
Post by: [silent:arts] on March 28, 2015, 05:16:59 AM
When do you start to sell them? I will be one of you first customers. Then I can finally get rid of my 160A.
First it must be up and running and completely tested  ;)
Title: Re: 903
Post by: [silent:arts] on March 30, 2015, 09:24:14 AM
Update: few resistor values in the dbx schematic are wrong  ::)
2nd prototype seems to work correctly.
Some more tests to follow.

(http://www.silentarts.de/DIY/90X-51X/IMG_1660.JPG)
Title: Re: 903
Post by: culteousness1 on March 30, 2015, 09:47:31 AM
Very nice to hear! How did the pot orientation work out?

Title: Re: 903
Post by: [silent:arts] on March 30, 2015, 09:55:02 AM
How did the pot orientation work out?
Odd. I mean good. All potentiometers = correct, trimmers wrong way (doesn't matter, but will be changed)
Title: Re: 903
Post by: [silent:arts] on March 31, 2015, 07:46:38 AM
Received some Prototype Panels from Frank @ frontpanels.de:

(http://www.silentarts.de/DIY/90X-51X/IMG_1669.JPG)

Next I will test different VCA options, all is working good up to now.
Stereo (CV) link doesn't, however, I didn't expect it to do. Won't be in the final revision.

Audio would work with +/- 16V only, however, the Meter doesn't.
Title: Re: 903
Post by: EmRR on March 31, 2015, 10:00:04 AM
You'll have to shoot it out with the new DBX and the old 903.   

(http://www.etnow.com/images/general/news/large/474088247_1533.jpg)

I see 903's can be had frequently in the $50-$75 range. 
900 racks are cheap, sometimes $100.   Same for the FS900 two space rack. 
I see several instances of a rack of nine 903's selling under $600. 
Title: Re: 903
Post by: TheJames on March 31, 2015, 11:00:42 AM
One thing I always missed on the 903 vs the 160, is the hard knee.
Title: Re: 903
Post by: jensenmann on April 07, 2015, 02:07:47 PM
I don´t know how close these 903 are to 160X or XTs. In case they are close, then it should be mentioned that the 1uF foil coupling cap in front of the VCA is too small IMHO.  I´ve modded several 160s and always found them to loose lowend in original state.  Increasing these caps to 6,8-10uF helped a lot and additionally cleared the lowmidrange. Though I used to like 160Xs for PA use I never dug them for recording because of the uninspiring audiopath. That changed after modding them, which involved a lot more than changing this cap. They can sound pretty darn good while sticking with the original compression behaviour which I really like.

Doug is right, prices of 160s and 903s are falling and they can be found for half the price than 2yrs ago. From an economical POV there´s no sense in DIYing one. But the fun in DIYing is something else, of course.
Title: Re: 903
Post by: [silent:arts] on April 07, 2015, 05:09:55 PM
Hi Jens, in the 903 the cap in front of the VCA is 4,7uF.
1uF is in front of the dbx 146221 RMS chip.
Title: Re: 903
Post by: mitsos on April 11, 2015, 08:05:12 AM
One thing I always missed on the 903 vs the 160, is the hard knee.
Is there a way to change the knee on the 903? That would be an excellent addition to this project!

Also, please, for those of us that, umm, don't have their 51x rack anymore, can you make the 24V pads on a tab that can be broken off? If I understand correctly the only thing running off 24V is the output amp, which could be modified easily to be 16V friendly, and then this project would be even cooler.  Thanks!
Title: Re: 903
Post by: [silent:arts] on April 12, 2015, 02:13:47 PM
It tested fine with +/-16V only (lower headroom, however)

The new PCBs are ordered and are coming like this:

(http://www.silentarts.de/DIY/90X-51X/VPR.jpg)
Title: Re: 903
Post by: mitsos on April 12, 2015, 05:03:49 PM
Cool, 16V works better in my API rack. :)

Curious, why the doubled up diodes?

Any ideas on the knee change?  I wish I could help with that, I would already have done it to my original 903s. 

In for a couple PCBs for sure, faceplates would be nice too!
Title: Re: 903
Post by: [silent:arts] on April 12, 2015, 06:31:30 PM
Curious, why the doubled up diodes?
to follow the original schematic as close as possible

Any ideas on the knee change?  I wish I could help with that, I would already have done it to my original 903s.
I changed nothing. I only added the option for impedance or transformer balanced output, and added a 202X VCA substitute circuit
(which is exactly the same 2150 / 218X VCA based circuit later revisions of the 903 used)
Title: Re: 903
Post by: mitsos on April 12, 2015, 07:21:20 PM
Re: the knee change,  I didn't mean that you changed from the original, what I meant is, had you researched the possibility of implementing a hard knee in this design, instead of "over-easy" all the time. 

I (and someone else above) mention it because it would be nice to have a harder knee for faster transient stuff, and would make this project THAT much more versatile. (not that it already isn't, I like DBX stuff, obviously).   There are lots of posts about this all over the net, but as far as I've seen, no one's come up with a solution.  Maybe it isn't possible or is overly complex to implement in the original modules,  but, this being a new design, and with all the brainpower on this forum, this seems like the place to do it. 

Anyway, don't want to just give you extra work :)  so I'm willing to help by testing ideas on my original 903s, if you need. 

thanks!

Title: Re: 903
Post by: TheJames on April 12, 2015, 08:36:54 PM
I agree with the knee comments.  I have a few 903's and really miss not having hard-knee as an option.  Over the years I've glanced at the 160 schematics in an effort to maybe see how I could make the 903 have the same hard knee function.  Ultimately I always got frustrated with trying to sort out the mess of the 160 schematics and think "another day maybe."

The new DBX 560a (160 in  500 series) gives you the option of "Over-easy" of hard knee compression.  I like the dual meters too (level and gain reduction).

Don't read it as discouraging, If I didn't have a 900 rack I'd be seriously eyeing this project.  However since I do have a 900 rack (and a few 903's) I'd be more interested in a 903 retrofit for hard knee.
Title: Re: 903
Post by: mitsos on April 12, 2015, 10:36:33 PM
Ultimately I always got frustrated with trying to sort out the mess of the 160 schematics and think "another day maybe."
haha, me too!

The new DBX 560a (160 in  500 series) gives you the option of "Over-easy" of hard knee compression.  I like the dual meters too (level and gain reduction).
Good point, DBX is pretty good about sharing info, they're one of the only companies with so much free service info of legacy products online.  Might be worth an email to them?

However since I do have a 900 rack (and a few 903's) I'd be more interested in a 903 retrofit for hard knee.
I thought about this too and I think you'd sell quite a few of these to the tons of people who are still using 903s!  How's that for an incentive! :)


Of course, I still would like a couple PCBs of whatever version you end up with.
Title: Re: 903
Post by: [silent:arts] on April 13, 2015, 04:02:13 AM
Well, if you want the hard knee option you should consider buying the DBX 560a.

Looking at the 160X schematic the side-chain is completely different to the 903, using two RMS converter, one for "over easy" and another for the hard knee and so on. It is not like changing a few resistor values or adding / leaving out a few components.
Title: Re: 903
Post by: mitsos on April 13, 2015, 05:12:18 AM
Well, if you want the hard knee option you should consider buying the DBX 560a.
That is an option, but I'd rather build the Silent Arts 903 with switchable knee!   ;D 8)    Also, I just saw they have a de-esser based on the 902!

Quote
Looking at the 160X schematic the side-chain is completely different to the 903, using two RMS converter, one for "over easy" and another for the hard knee and so on. It is not like changing a few resistor values or adding / leaving out a few components.
I can't make much out of the 160X schem on their site, it's all cut up and there is a small sliver missing.  Specifically R83 and R84.  Do you have a full schematic?   Anyway, it seems to me, (someone smarter than me should look at this)  one RMS is only used for metering?  And the over easy switch is switching between two opamps following the U13 RMS detector.  half of U5 and half of U6, the ones surrounded by diodes.

Anyway, it's your project, like I said, I'll take some PCBs regardless.
Title: Re: 903
Post by: [silent:arts] on April 13, 2015, 05:20:03 AM
902 to come later  ;)

Attached the best readable of different 160X schematics I have.
Title: Re: 903
Post by: mitsos on April 13, 2015, 05:27:05 AM
of course.. I was looking at the 160XT..

but wow, this one, the 160X, the schematic makes me dizzy.  I'll have to print it so I don't get seasick, hopefully others will chime in, and maybe the hard knee will work out...  That is, if you want to do it.

cheers!
Title: Re: 903
Post by: EmRR on April 13, 2015, 07:57:59 AM
My memory says a simple switch of knee changes the meter calibration, so one or the other meter setting will be wrong in the simple version.   DBX is probably using 2 SC and scaling them relative to one another; guessing. 
Title: Re: 903
Post by: mitsos on April 13, 2015, 09:29:18 AM
I looked at the 160X schematic and I still think the lower RMS is only going to the meter, but I can't see how the signal gets to the upper RMS detector...  ::)  Was this jumpered to the input like the 903? 

Anyway, one pole of the switch seems to switch between the outputs of 105A alone and 105B + 105A through a 1K resistor.  The other pole connects one input of one of the LM339's to the negative rail, I think, turning on the "above, easy, below" LEDs.  But I don't see any change to the GR metering at all.  Someone with a degree please step in!

Hard knee would mean the CV would ramp up to full value quicker and closer to the threshold, whereas the overeasy is supposed to slowly start ramping up before you actually hit the threshold, IIRC. 
Title: Re: 903
Post by: mitsos on April 13, 2015, 03:56:16 PM
OK, I took a shot at tracing out the RMS detector to better visualize how the individual diode-connected NPNs were used.  The NPNs are all represented as diodes but marked with a number corresponding to the schematic silent arts posted on the first page:

http://groupdiy.com/index.php?topic=59044.msg750249#msg750249

The circled junctions correspond to the pin numbers of the detector.  Anyway, someone double check this, I had very little sleep last night. 

Thanks for putting up with me, volker!
Title: Re: 903
Post by: mitsos on April 14, 2015, 12:07:05 AM
BTW,  the 47K above the second opamp, I couldn't tell if it was + or - 15V, but I found a clearer schematic, it should be -15V. 
Title: Re: 903
Post by: mitsos on April 23, 2015, 05:02:30 PM
...Tumbleweeds.....

So, I've been looking at THAT app notes and talking to other members, (mainly joaquins), and come to the conclusion that the soft/hard thing is not the RMS but the thresh/rectifier amps afterwards.  If that helps anyone. I'm going to try some changes to my 166, and see if I get anywhere, but it doesn't seem like anyone else is interested in such an obvious improvement to an otherwise great comp..

Other than that, in case you're still working on this, a sidechain HPF would be nice.  Seems DBX had a "contour" switch on some units which seems to be just a passive HPF on the RMS input.
Title: Re: 903
Post by: Patrick from Davis on April 23, 2015, 05:16:09 PM
I think a reasonable amount of people are interested in the hard knee, however, personally, I don't have anything to say that will help you on this matter.  Looking at Volker's board, there does appear to be some real estate left.  Yes, redesigning things/verifying is a pain, and could be something that Volker isn't interested in. However even if you come up with a mod for your old unit, it seems to be interesting enough to write it down or share.  Anyhow, I'll go back to lurking and learning now...
Patrick

Title: Re: 903
Post by: TheJames on April 23, 2015, 11:42:30 PM
I've been busy with other projects, but I do have an interest in this.  I got a little time with some schematics today and have some ideas floating in my head.  Maybe if  I get some time this weekend....

Title: Re: 903
Post by: mitsos on April 24, 2015, 12:52:02 AM
Well, I haven't come up with anything yet, just some ideas to try.  For now, it'll have to be with the 166, in a couple of weeks I should have my 903s back.

As for the HPF, a simple 1 pole could be done by placing a cap in series with each leg of the differential input to the RMS.   Or further along, by swapping caps going into the RMS detector.
Title: Re: 903
Post by: culteousness1 on April 30, 2015, 04:47:27 PM
Any news, Volker?  8)

Carsten
Title: Re: 903
Post by: [silent:arts] on April 30, 2015, 05:11:37 PM
sure - rev02 PCBs are already soldered, but haven't found time for the final tests.
Title: Re: 903
Post by: [silent:arts] on May 14, 2015, 08:49:21 AM
Finally found some time to play with rev02  8)

(http://www.silentarts.de/DIY/90X-51X/IMG_1871.JPG)

We implemented six different output options:
(http://www.silentarts.de/DIY/90X-51X/90X51X-Output-Options.jpg)

Some measuring (all done with the original unbalanced output version):

Frequency response:
(http://www.silentarts.de/DIY/90X-51X/90351X-Frequency.jpg)

Noise floor:
(http://www.silentarts.de/DIY/90X-51X/90351X-Noise.jpg)

Some gain reduction curves:
(http://www.silentarts.de/DIY/90X-51X/90351X-GainReduction.jpg)
Title: Re: 903
Post by: [silent:arts] on May 14, 2015, 08:58:53 AM
Maximun output level, headroom and dynamic range is different in VPR vs. 51X configuration:
(http://www.silentarts.de/DIY/90X-51X/90351X-Output.jpg)

but power consumptions is in within specs for both:

VPR, +21dBu into 600R, no gain reduction: +16V = 48mA / -16V = 56mA
VPR, +21dBu into 600R, all LEDs on: +16V = 65mA / -16V = 80mA

51X, +25dBu into 600R, no gain reduction: +16V = 28mA / -16V = 36mA / +24V = 25mA / -24V = 30mA
51X, +25dBu into 600R, all LEDs on: +16V = 50mA / -16V = 36mA / +24V = 30mA / -24V = 35mA
Title: Re: 903
Post by: TheJames on May 14, 2015, 09:02:46 AM
Looks pretty good.

What are you using for your measurements?
Title: Re: 903
Post by: [silent:arts] on May 14, 2015, 09:10:37 AM
What are you using for your measurements?
(http://www.silentarts.de/DIY/90X-51X/IMG_1873.JPG)
Title: Re: 903
Post by: TheJames on May 20, 2015, 02:47:51 PM
That's a really nice piece.   :)
Title: Re: 903
Post by: [silent:arts] on June 27, 2015, 06:04:26 AM
L-Bracket done, and received my final front panel from Frank  :)

(http://www.silentarts.de/DIY/90X-51X/IMG_1967.JPG)
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on July 05, 2015, 09:52:22 AM
903-51X schematic (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-Schematic.pdf)
903-51X PCBs (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-PCBs.pdf)
903-51X Parts List (http://www.silentarts.de/DIY/90X-51X/90351X_rev02-PartsList.pdf)
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on September 26, 2015, 05:59:58 AM
25 full kits are available, check the white market (http://groupdiy.com/index.php?topic=39570.0) if you are interested.
Title: Re: 903-51X Comp / Limit
Post by: Upacesky on October 03, 2015, 03:55:33 PM
Hi Volker,

I'm building the 903-51x and after populating the diodes and resistors, I have some questions:
-R70 is not included, should I worry about it or just leave it open?
-what's the value of R71?
-on the schematic, RM11 and RM14 are 51R, but the bom doesn't say anything about RM11 and I only got one 51R resistor with the kit.  Is RM11 populated?
-What are the little PCB holes inside the footprint of IC2-3 and REL1?
-Why is there an IC footprint over QM22?
- is there something to do for calibrating the unit?

Well, that's a lot of questions, thank you for your answers!
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on October 04, 2015, 05:45:56 AM
- R70 and R71 are not included, and not needed with the provided, pre-trimmed THAT 2180 VCA. Just leave them out.
- RM11 is only for trimm-able VCAs, it is not included and populated for the 2180 VCA
- the little PCB holes inside some footprints are VIAs (http://pcb vias diameter), just ignore them
- the IC footprint over QM22 is for the original 146221 dbx RMS chip

- calibration: I will adjust the 160XT calibration procedure for the 903-51X today / tomorrow
Title: Re: 903-51X Comp / Limit
Post by: Upacesky on October 05, 2015, 10:07:19 AM
So the unit is finished, passes audio, sounds clean, the meter is metering, everything's fine!

I just need to calibrate the thing now.
Thanks a lot, the kit was easy to build.
Title: Re: 903-51X Comp / Limit
Post by: culteousness1 on October 05, 2015, 10:15:43 AM
So the unit is finished, passes audio, sounds clean, the meter is metering, everything's fine!

I just need to calibrate the thing now.
Thanks a lot, the kit was easy to build.

Pictures or it never happened  ;D
Title: Re: 903-51X Comp / Limit
Post by: Upacesky on October 05, 2015, 10:54:19 AM
Yes, sir!
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on October 05, 2015, 03:51:38 PM
Congrats!

I just need to calibrate the thing now.

Lets start:

OUTPUT OFFSET TRIM:
with no signal applied adjust R22 to 0V DC measured at R28

GAIN CAL:
with OUTPUT potentiometer set at middle position (0dB) adjust R12 for input level = output level

Up for now leave the other trimmers like they are. Most of my tests have been done like this.
We will go thru them later.
Title: Re: 903-51X Comp / Limit
Post by: Upacesky on October 06, 2015, 03:27:33 AM
OK,

I calibrated the output offset, but I need an extension jig or a 24V power supply to use the module outside of the rack and calibrate the gain. Those trimmer are a bit hidden and I can't access them with a screwdriver at the moment.
I'll keep you tuned
Title: Re: 903-51X Comp / Limit
Post by: Axelerator on October 26, 2015, 02:58:43 PM
Hi Volker,
is this Project for sale already ?
always in for 511 diy and  i always wanted dbx style compression for my bassdrums !

greets,
axel
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on October 26, 2015, 03:14:49 PM
Hi Axel,

yes, already for sale:
http://groupdiy.com/index.php?topic=39570.0
Title: Re: 903-51X Comp / Limit
Post by: Axelerator on October 30, 2015, 09:47:53 AM
Du hast ne mail ;)
Title: Re: 903-51X Comp / Limit
Post by: Mulmany on January 14, 2016, 10:26:36 PM
How do you determine the orientation of the haufe transformer? I also guess that you dont needJP1 and RO28 with the transformer option.

Thanks
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 15, 2016, 03:28:30 AM
The Haufe Transformer will only fit like in attached picture,
and - correct - don't install JP1 and RO28 if you are using a transformer.
Title: Re: 903-51X Comp / Limit
Post by: Mulmany on January 26, 2016, 09:00:24 PM
One Done! One more to go!  Tested against my gold can 903's and I like these better. 

(http://i1196.photobucket.com/albums/aa417/Mulmany/Mobile%20Uploads/20160122_234633.png_1.jpeg)
Title: Re: 903-51X Comp / Limit
Post by: nashkato on October 27, 2016, 03:05:29 PM
got one on the desk right know ...
Quote
It tested fine with +/-16V only (lower headroom, however)

at my unit it  the relay  switches @ app. 17.5V , it´s always in STDBY in my VPR rack .
solved it by hardwiring the +16V to the former GND pin of the relay , datasheet of TQ2-24V suggests maximum of 38V
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on October 27, 2016, 04:50:00 PM
Strange, worked here without any mod.
However, not switching against ground is even the better solution!
Well done.
Title: Re: 903-51X Comp / Limit
Post by: DuBmastah on December 19, 2017, 07:05:13 AM
WOAAAAW,

Absolutly great KIT.
Pretty good quality, Beautifull and solid design, worse every penny imho...
Not plugged yet but ready to go in the 51x box !!!

(https://scontent-cdg2-1.xx.fbcdn.net/v/t31.0-8/25532254_1768839066488973_3378538533996762206_o.jpg?oh=1d941a1c7e4d3f88ab31e6844758b23e&oe=5AB86DF1)
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on December 19, 2017, 10:48:43 AM
Looking good DuBmastah  8)
This doesn't look like done by a "newbie".
Congrats, fire it up!
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 15, 2018, 07:26:06 PM
Hello Volker and others,

I started building my 903-51x and have a few questions:

1) On the PCB there is no CBP17 to CBP20 marked. I suppose the WIMAs go next to the electrolytic caps that say C17 to C20. Is this correct?

2) How can I determine the polarity of the tantal capacitor (C12)? All I see printed on it is what you see in my attachment.

3) Strangely enough, after populating all resistors I have one spare 4,7k resistor left. I have checked the PCB for empty spaces, but there are none. Could this simply be a packaging mistake? Or have I overseen something?

4) What are the two dark brown components that look similar to diodes? Are these wire jumpers? I have already soldered a simple wire as a self-made jumper to make the module VPR-ready.  Should I better use one of these brown parts? And why are there two of it? Where does the second one go?

Thanks in advance,
Claudio
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 16, 2018, 12:18:14 AM
Hi Claudio,

Quote
1) On the PCB there is no CBP17 to CBP20 marked. I suppose the WIMAs go next to the electrolytic caps that say C17 to C20. Is this correct?
yes
2) How can I determine the polarity of the tantal capacitor (C12)? All I see printed on it is what you see in my attachment. (http://2) How can I determine the polarity of the tantal capacitor (C12)? All I see printed on it is what you see in my attachment.)
you see the +? that is the positiv leg (on the photo it looks centered but is at the right leg)

Quote
3) Strangely enough, after populating all resistors I have one spare 4,7k resistor left. I have checked the PCB for empty spaces, but there are none. Could this simply be a packaging mistake? Or have I overseen something?
I'm known for packaging mistake. Glad you have too much, in another kit this resistor will be missed ...

Quote
4) What are the two dark brown components that look similar to diodes? Are these wire jumpers? I have already soldered a simple wire as a self-made jumper to make the module VPR-ready.  Should I better use one of these brown parts? And why are there two of it? Where does the second one go?
If we are talking about the same parts they are zero ohm resistors. I put them in the kits since the transformer is an option (look at the 2nd picture (https://groupdiy.com/index.php?topic=59044.msg750132#msg750132)).
For VPR there is jumper wire needed, please don't power the unit up if you put one to the <--VPR--> marks on the PCB. This would short the +/- in your lunchbox.
See attached photo for the VPR "mod".
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 16, 2018, 04:55:52 AM
Thanks, Volker, for another helpful response. :)

2) How can I determine the polarity of the tantal capacitor (C12)? All I see printed on it is what you see in my attachment. (http://2) How can I determine the polarity of the tantal capacitor (C12)? All I see printed on it is what you see in my attachment.)
you see the +? that is the positiv leg (on the photo it looks centered but is at the right leg)
Well, that’s my problem. The + is indeed centered and it’s not exactly clear which side it belongs to. So if I face the imprint, the right leg is the positive one?

Quote
I'm known for packaging mistake. Glad you have too much, in another kit this resistor will be missed ...
If anyone misses it, they can PM me. :)

Quote
If we are talking about the same parts they are zero ohm resistors. I put them in the kits since the transformer is an option (look at the 2nd picture (https://groupdiy.com/index.php?topic=59044.msg750132#msg750132)).
That’s what I thought. So with my Haufe transformer I won’t need them, right?

Quote
For VPR there is jumper wire needed, please don't power the unit up if you put one to the <--VPR--> marks on the PCB. This would short the +/- in your lunchbox.
Ouch, then I made a mistake. See my attached pic for what I did.  :-\ Now the diodes are already soldered. Can I simply add two wires from their right solder pad to the jumper pads, as I marked in bright blue in the picture?

Thanks,
Claudio
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 16, 2018, 05:19:36 AM
- C12: in your photo the right leg is +
- Haufe transformer = no jumpers
- VPR: you can do that. Oder die Brücke in der Mitte durchschneiden und einfach umschwenken.
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 16, 2018, 06:57:42 AM
- VPR: you can do that. Oder die Brücke in der Mitte durchschneiden und einfach umschwenken.
Ach ja, klar. Gute Idee. Allerdings: Die Lunchbox-Anschlüsse, zu denen du in deinem Bild die Brücke baust, sind doch genau die, die ich absäge. Die Brücke muss zu den Dioden gehen, oder nicht?
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 16, 2018, 08:47:26 AM
Richtig, die sägst Du ab, die beiden Durchkontaktierungen bleiben Dir aber erhalten  - und die sind per Leiterbahn mit den Dioden verbunden.
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 31, 2018, 09:29:48 AM
Hi Volker,

habe heute etwas Zeit gefunden, das Modul fertig zu bauen. Bevor ich es anschließe, ein kurzer Sicherheitscheck: Ist die Brücke so nun richtig (siehe Anhang), wenn ich den 903-51x in einem VPR-Rack benutzen will?

Danke
Claudio

Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 31, 2018, 11:24:37 AM
Perfect!
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 31, 2018, 11:54:52 AM
Ok, thanks!

But here’s another problem: When I mount the meter board to the main PCB, the distance is too high and the LEDs tower over the bracket. Seems like the connector pins are too long. See picture.

Yes, I know, I soldered the socket to the meter board and the pins to the main PCB and not the other way around as in your pics. But this shouldn’t make a difference, since the distance between the two PCBs would still be the same.

So what’s wrong here? Could this be another packaging mistake and the 2 x 5 socket or pins are simply too large? :)
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 31, 2018, 12:09:49 PM
No packaging mistake. You need to shorten the header.
Title: Re: 903-51X Comp / Limit
Post by: Claudio on January 31, 2018, 12:12:46 PM
But it has these plastic stops at each end that define the distance. Where exactly should I cut, and how much? Do you happen to have a picture of it?
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on January 31, 2018, 12:29:24 PM
Cut it away.
Title: Re: 903-51X Comp / Limit
Post by: Claudio on February 23, 2018, 07:18:46 AM
After a long break, I finally finished my 903-51X build in five minutes today. Sounds great, quite aggressive compression, though. I might have to look into calibration next. Thanks, Volker, for all your support and patience with my newbie questions!

Now I’m left with another huge problem: my lunchbox is full now...

Title: Re: 903-51X Comp / Limit
Post by: kante1603 on February 23, 2018, 09:46:21 AM
There's only one solution,isn't it  8)  ?


Best regards,


Udo.
Title: Re: 903-51X Comp / Limit
Post by: Claudio on February 23, 2018, 10:59:18 AM
There's only one solution,isn't it  8)  ?
For the lunchbox you mean? Sure. Six slots just ain’t enough. ;)
Title: Re: 903-51X Comp / Limit
Post by: kante1603 on February 23, 2018, 12:34:29 PM
For the lunchbox you mean? Sure. Six slots just ain’t enough. ;)
Yep!
Title: Re: 903-51X Comp / Limit
Post by: Mulmany on March 03, 2018, 08:54:27 PM
Was a calibration procedure ever nailed down? Over the initial voltage calibration, I mean.
Title: Re: 903-51X Comp / Limit
Post by: [silent:arts] on March 04, 2018, 01:07:39 AM
Was a calibration procedure ever nailed down? Over the initial voltage calibration, I mean.
Sorry if I missed mailing one to you:

Output Gain Calibration
1. Set the controls to the following positions:
   - Unit not set to BYPASS
   - THRESHOLD control set to 0
   - RATIO set to 1:1
   - GAIN set to 0dB
2. Set your signal generator to 0 dBu at 1kHz
3. Adjust GAIN CAL R12 so that the level at the output is 0 dBu

Output Offset Calibration
1. Mute your signal generator
2. Measure DC with your voltmeter at the left leg of R28
3. Adjust OUPUT OFFSET TRIM R22 to nearest 0V DC

Infinite LED Adjustment
1. Set your Ratio Potentiometer (R56) to Position INF:1
2. Adjust INF LED CAL R60 to switch between on and off at that position

INF CAL Adjustment
1. turn INF CAL R57 full counterclockwise

THRESH CAL Adjustment
1. Measure DC with your voltmeter at the upper Leg of R50
2. Adjust THRESH CAL R49 to nearest +10V DC

OFFSET TRIM Adjustment
1. Measure DC with your voltmeter at the upper Leg of R53
2. Adjust OFFSET TRIM R54 to nearest 0V DC

RMS Symmetry Adjustment
1. Set your signal generator to 0 dBu at 100Hz
2. Monitor IC2 Pin1
3a. Adjust RMS SYM TRIM R40 for best RMS symmetry (equal amplitude peaks of the waveform)
or
3b. Adjust to measure 50mV with your voltmeter at IC2 Pin1
Title: Re: 903-51X Comp / Limit
Post by: Mulmany on March 08, 2018, 11:36:57 PM
Sorry if I missed mailing one to you:

Output Gain Calibration
1. Set the controls to the following positions:
   - Unit not set to BYPASS
   - THRESHOLD control set to 0
   - RATIO set to 1:1
   - GAIN set to 0dB
2. Set your signal generator to 0 dBu at 1kHz
3. Adjust GAIN CAL R12 so that the level at the output is 0 dBu

Output Offset Calibration
1. Mute your signal generator
2. Measure DC with your voltmeter at the left leg of R28
3. Adjust OUPUT OFFSET TRIM R22 to nearest 0V DC

Infinite LED Adjustment
1. Set your Ratio Potentiometer (R56) to Position INF:1
2. Adjust INF LED CAL R60 to switch between on and off at that position

INF CAL Adjustment
1. turn INF CAL R57 full counterclockwise

THRESH CAL Adjustment
1. Measure DC with your voltmeter at the upper Leg of R50
2. Adjust THRESH CAL R49 to nearest +10V DC

OFFSET TRIM Adjustment
1. Measure DC with your voltmeter at the upper Leg of R53
2. Adjust OFFSET TRIM R54 to nearest 0V DC

RMS Symmetry Adjustment
1. Set your signal generator to 0 dBu at 100Hz
2. Monitor IC2 Pin1
3a. Adjust RMS SYM TRIM R40 for best RMS symmetry (equal amplitude peaks of the waveform)
or
3b. Adjust to measure 50mV with your voltmeter at IC2 Pin1

Thanks.