dbx 160vu clone

[Biasrocks]

I'm amazed on how long USA to Canada post takes! I sent it off a couple weeks ago

What's even more surprising is that I'm on the busiest Canada/USA border and it still takes 1.5-2 weeks
to see things from the US.

When I order from the UK the shipments arrive in about half that time.

Mark

 

[damnyankee]

That's nice layout AC! Looks really good and easy to implement. I agree with the LED positioning. Much easier to just be looking at one area of the panel at a time. After looking at your layout, I think I will end up doing a 2 channel unit after all.  ;D Why not? Its so inexpensive to build!

I just wanted to confirm that if I use the THAT 2180, that there are no issues building the discrete RMS module on the PCB. From what I remember reading, the only issue with the transistor matching has to do with the VCA. Is that the case?

PCB still in transit, but I am stoked to get working on it. Anyone else made some head way?

Yes - I hope to have the power supply up and running by Tues/Wed.  I received the last of the parts list from Mouser & Digikey last night.  I realize there's a couple of parts missing not on the materials list that I'm out of (jacks, a couple of ICs, fuse holder, etc), so as we finish the prototype, I'm sure AC would appreciate if we forward those additions so he can tack them on his materials list.

I am NOT looking forward to the calibration process...

DY

 

[Biasrocks]

Started building this guy tonight and I have a few observations.

1. The silk screening vaporizes if you rub up against it.
2. The four mounting holes on the corners need to be considerably larger,
preferably to fit a 6-32 or 4-40 sized screw or mounting device.
3. As pointed out earlier, the hole spacing for the dbx RMS/VCA modules is incorrect.
4. Suggestion for silk screen, instead of 4.7K use 4K7, decimal points are hard to see.
5. The pads for resistors could be larger, but this is less of an issue and only if space
permits.
6. AC transformer and Power connectors should be larger sized to accomodate higher
currents and larger wire. Maybe double sized/spaced.

That's it for now, will report back with more as I continue on.

Mark

 

[abechap024]

Started building this guy tonight and I have a few observations.

1. The silk screening vaporizes if you rub up against it.
2. The four mounting holes on the corners need to be considerably larger,
preferably to fit a 6-32 or 4-40 sized screw or mounting device.
3. As pointed out earlier, the hole spacing for the dbx RMS/VCA modules is in correct.
4. Suggestion for silk screen, instead of 4.7K use 4K7, decimal points are hard to see.
5. The pads for resistors could be larger, but this is less of an issue and only if space
permits.
6. AC transformer and Power connectors should be larger sized to accomodate higher
currents and larger wire. Maybe double sized/spaced.

That's it for now, will report back with more as I continue on.

Mark

Good stuff.

I agree using the 4k7 instead of the 4.7k , I know I was inconsistent, and that makes the potential confusion even worse.

Making the pads bigger is a good idea that won't take very long on my end to change.

Good suggestions, stuff I wouldn't of thought of.

-Abe

 

[Rybow]

Alrighty. I have been thinking a lot about the filter cap experiment, and I am going to implement it when I get around to building this bad boy. I will be mounting the caps off board, and I just wanted to run the configuration by you guys to make sure it would work.

So, I would mount the 470uF caps on on a separate board and connect them to the main board via some wire. The 4700uF caps would be mounted behind the 470uF. Connect the + terminal of one 470uF cap to a 4700uF cap, do the same for the other 2. Then use a DPDT switch on the - lines in order to switch in both 4700uf caps simultaneously. This keeps the 470uF caps always in the circuit to avoid the popping issue. Should I connect the other poles of the switch to ground in order to provide a pathway for the 4700uF caps to drain? Would it be better to switch the + side or even to switch the caps completely out of the circuit?

Thanks!

 

[Biasrocks]

On the 4.7uf/25 volt audio cap, the spacing needs to accommodate a number of different lead spacings, I would say from 2.5mm all the way up to 15mm. I'm choosing to put a film cap in that position as opposed to a bi-polar electrolytic, mostly because availability of film caps tends to be better than bi-polar electrolytic. For example I could only find one bi-polar elco in stock at Newark and it was a 10uf/16v as
opposed to a 4.7uf/25v, so I opted to go with a film cap in that position. Luckily I was able to find an axial version so I'll be able to fit it into the lead spacing provided.

Alternate footprints for all the electrolytics would be a good thing. This will allow different versions to fit into these spaces. For example I'm using a 470uf/50v which has a lead spacing of 5mm, instead of the 10mm provided.

Suggested BOM changes:

Amend the BOM for the "4558a" to read RC4558P for the PDIP version.

Allow subing film cap for C8 - 4.7uf/25v

20K pots Audio or Linear taper?

Transistor selection

BC263 - The collector current is specified @ 200ma, the BC560C is only 100ma. A better substitution would be a BC177B.
BC341 & BC361 - A closer substitute is the BC441/BC461 also about $1 cheaper than the NTE parts.

Power Supply

Substitute for 1N4383 = 1N5393

Substitute for 1N9608 9.6V Zener = BZT55C9V1 (9.6V)
or 1N5237B (8.2V) + 2x1N4148TR *200mw version (1.4V)
or 1N936 (9.45V)
or 1N5232 (5.6V) + 1N5228 (3.9V)


1N9608 is actually 1N960B a 9V1 Zener rated @ 500mw. The "B" designation indicates %5 tolerance. Alternate part would be 1N5239B.

Mark

 

[dandeurloo]

Abe, I just got back from being out of town all last week with my Drum company and I saw your layout.  I really like it for the stereo version in the 2U.  Nice work.  It even leaves some room for some nice mods like mix and such if it is implemented!

 

[Rybow]

Hey AC! PCB arrived today. Let the games begin!

 

[abechap024]

Hey AC! PCB arrived today. Let the games begin!

Great News!! Check the thread for relevant info, and feel free to if you have any questions, of course.

AC

 

[abechap024]

Bump...Interested in any progress anyone has made...
Cheers,
Abe

 

[Biasrocks]

Stuffed as far as I can with parts on hand, got a parts order into Newark which is waiting on a
523K resistor which is back ordered. As soon as I get the parts order I should be able to fire it
up within a few hours.

Mark

 

[Biasrocks]

It's alive.

I'm getting voltages and it's passing signal. The transformer I had laying around isn't adequate to get the 24v rails up and running to spec, but the 15v rails are good and strong. Only seeing about 20v's on the 24 rails, but once I get a proper transformer on there that will be fine.

The meter doesn't seem to respond to any of the trim pots being turned to their extremes so, not sure what's going on there. It does respond when I turn the threshold control along with the LED's.

Some notes on the layout,

1. Power supply transistors Q1, Q2, Q5 & Q6 require heat sinks as called for in the schematic, with the current layout
it's very difficult to fit these because the transistors are laid out very close to one another.

2. NOTE on transistor subs; When I placed the transistors they were all EBC where the layout calls for CBE. I needed to twist the leads to properly orient them on the board.

BOM Revisions;

C32/15pf is specified in the MAIN BOARD BOM and is not need when stuffing the DBX 208 RMS detector.


And a couple of questions;

1. It seems that the 24v circuit is unregulated so it would be fairly critical to match that up with the original. Do we know what the original PT transformer specs are?

2. What's the calibration procedure for the meter emulation circuit?

Mark

 

[Kingston]

1. It seems that the 24v circuit is unregulated so it would be fairly critical to match that up with the original. Do we know what the original PT transformer specs are?

You are remaking a commercial mass production unit. Their probable original design goal priority #1 was to save money where ever they could. This is one of those places where you really don't have to care about that. No DIY guy is going to care about the 4 euros they saved with unregulated 24V rails.

Just make them regulated, use a properly specified and easily available - let's say 25V - transformer with some standard easy regulator solution. No need to hunt for some obscure transformer spec. You get more stable performance as a bonus.

 

[Biasrocks]

Okay, but I'd rather stick with the original design, flaws and all. There's also the issue of the regulated 15v rails, which will now be burning more voltage and creating more heat because of the need to elevate the secondary voltage of the PT in order to regulate the 24v rails.

The original is fused at 1/4 amp, so I'm thinking 24-0-24 0.5A should fit the bill and will probably power two of these guys without issue; or am I better off going to 25-0-25 because of the voltage drop across the bridge diodes?

Mark

 

[abechap024]

It's alive.

Awesome!

The meter doesn't seem to respond to any of the trim pots being turned to their extremes so, not sure what's going on there. It does respond when I turn the threshold control along with the LED's.

Hmm that is interesting...you should be able to zero out the meter with r117mechzero trimmer and then go through the calibration procedure found in the calibration procedure pdf.

Some notes on the layout,

1. Power supply transistors Q1, Q2, Q5 & Q6 require heat sinks as called for in the schematic, with the current layout
it's very difficult to fit these because the transistors are laid out very close to one another.

good Idea I'll add that to the list

I'm very excited to hear more about this. I'm still waiting on my parts and been stupid busy with school and work on the weekends. Thumbs up and a big thanks to Mark for gaining more ground on this project.

Abe

 

[envelope]

...you should be able to zero out the meter with r117mechzero trimmer and then go through the calibration procedure found in the calibration procedure pdf.

Hi Abe, I've looked for the calibration procedure pdf, but I can't seem to locate a link. Can you point me in the right direction. Thank you kindly.

 

[abechap024]

Here it is.

www.acsoundstudio.com/DIY/160vu/160-161%20Calibration%20Procedure.pdf

you can also find it on the dbxpro.com site.

Cheers!
AC

 

[abechap024]

So Mark, you say the unit passes signal...does it compress?

Cheers,
AC

 

[Biasrocks]

Yes, I think it's compressing but it's hard to tell what it sounds like because I don't have the proper power transformer.

The sound resembles a pffft, because when the power transformer has to deliver it craps out.

I'm back to deciding what power transformer to use. I'm going to measure the voltage drop/gain with the one I'm using and decide whether I need a 24-0-24 or a 25-0-25.

Mark

 

[damnyankee]

Yes, I think it's compressing but it's hard to tell what it sounds like because I don't have the proper power transformer.

The sound resembles a pffft, because when the power transformer has to deliver it craps out.

I'm back to deciding what power transformer to use. I'm going to measure the voltage drop/gain with the one I'm using and decide whether I need a 24-0-24 or a 25-0-25.

Mark

Hi Mark,

This is what I'll be using...

http://www.antekinc.com/details.php?p=24

DY