Crush N Blend Rev 6 V3 (CNB / Wet-Dry Circuit) + Support

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livingnote

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Joined
Aug 12, 2007
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Crush N Blend Rev 6      Crossfader / Wet-Dry Circuit

Rev6TTest3c.jpg


Measurements (clickable):



Distortion and Noise (A-Weighted):

Level: 12.2 dBu
Freq: 1031.25 Hz
S/(N+D): 0.0038%
THD+N: 0.0023%

Level: 18.2 dBu
Freq: 1031.25 Hz
S/(N+D): 0.0039%
THD+N: 0.0028%


Level: 20dBu
Freq: 1031.25 Hz
S/(N+D): 0.0049%
THD+N: 0.0042%

Distortion takes off around 19.5dBu.

Quiescent current draw ca. 70mA including LED (Class A opamp output operation due to
pull up resistors).

For the graphs above, note there is some fluttering in the meter under about 250-500Hz.
I don't know where that slight phase twist up at 20kHz in bypassed comes from but I surmise
it's a side effect of there being no load on the DAC output going straight back into the input
for measuring. As far as I remember, it did that even when there was no CnB attached at all,
and the input was shorted to the output so...yeah. Looks good.

Changelog:

Power Input protection diodes from last rev now have some added 7.2Ω rail input resistors,
and there's a 10Ω ground plane lifting resistor. There are 100k resistors to ground on all 4 pot
inputs which stabilize the whole construction. Relay Status indicator LED if you want one, and
6 trimmers with a wide enough range to adapt to most "out there" situations.

Also, a push pull dual 10k pot from Alpha has been found - I have them in stock here, along
with small PCBs that output to a standard pin header.

The main mechanical changes were that I got the rivets/vias out from under the component
legs for two reasons:

The "weak" reason for this is because I hate soldering and resoldering stuff that goes through
vias because on industrial boards, you can burn out the barrel and on DIY boards with rivets it's
just a royal p.i.t.a. so I keep them away from component legs.

The "strong" reason is that if you're etching at home and can't lay vias in the form of rivets,
you're screwed, and end up having to rework the board or have ugly caps, relays and trimmers
sticking half out of the PCB. By locating all vias away from the component legs, you can just solder
a wire where the via goes and don't have to worry about components not sitting right.

-> Etch Rats Happy 8)

Construction Documents:

Master File


Etch Separations


Schematic


BOM


Wiring Guide for GSSL


And here is "Das Exquisite Board" from my Etch Lab if you want to order one:



Have Fun!
 
Construction Documents added.

Note to Moderators: I posted this in the lab after having been gone too long and in the old rut of posting projects there - could this be moved to the dynamics processors forum? Thanks :)

Will add Etch Separations as soon as I have them verified.

[Edit: I added them anyway - if it blows up, it wasn't me ;)]
 
Yeah, sure - you can send a mail to the address in the construction docs and I can etch some. At the moment it's all still living-room style etching because I haven't yet found a way to reliably turn dxf into Gerber data without software that costs $4000+, but if someone knows anything or can help, I will be able to do an actual run sometime.
 
Hi Lukas,

I'm ready to start installing and wiring the Crush N' Blend board you sent me on my GSSL but I have few questions though...

- First, I've been surprised to notice that on the populated board you've sent me, there's only 2 Wima caps in front of the 8 electrolytic capacitors, so there is 6 empty spaces left, is it normal ? or do I need to solder 6 more Wima capacitors onto the free solder pads ?
- I've chosen to separate the in/out switch and the pot, so which kind of switch do I need to use ? is a SPDT switch ok ?
- Also could you explain how to wire it ?
- I received your wiring layout but I'm a "newbie" and the GSSL is my first build so it would have been really helpful to have a picture showing the wires and the pads where they are soldered from and to.

My unit is fully working, it's a classic GSSL from Gustav's PCB Grinder with a Turbo mod installed.

Thanks for your help

Pierrick
 
Hey Pierrick,

cool - I left the Wimas off because there are Panasonic FCs on there and word has it that bypassing good
electrolytics with polyester capacitors can actually degrade signal behavior again, and so I left them out.

Switches - SPST or SPDT are both fine, you just need to apply power to the relay with it. When Relay power
(9-18V) is interrupted, the unit goes into bypass.

Here's the wiring guide for the GSSL.

Cheers :)
 
Cool ! Thanks for the wiring guide, it seems to be really clear. I'll let you know if I have some more question.
 
Hi Lukas,

I've finished wiring the C N' B on my GSSL, now it's time for testing in my studio. I'll let you know the results.
Otherwise I still have a question... You wrote :
I left the Wimas off because there are Panasonic FCs on there and word has it that bypassing good
electrolytics with polyester capacitors can actually degrade signal behavior again, and so I left them out.

So why did you put 2 Wima caps in front of 2 of the 8 electrolytic Panasonic caps ? The 6 left electrolytic caps have nothing soldered in front of them so, DO I let the board like this or do I have to unsolder the 2 Wima caps ?

 
Hi Lukas,
I've finally got the time to bring my unit to my studio and test it. I've got two issue. I've found the first one directly when opening the unit when coming back home. I made a mistake when connecting the  12v power for the C N' B via the SPDT switch so, this mistake explained why I didn't get any change when activating the C N' B with the switch. The second issue I've got is that I had the left side signal completely saturated and the left side vu meter on my console where were inserted the GSSL was clipping and staying on top in red. I think I've found the issue too but not sure, so maybe you'll tell me if it could be that.
When desoldering the 100p cap of the wet left side, I had some difficulty to do it because of the small space between components and I think that I've damage the cap. Do you think that it could explain the issue ?

Thanks for your help.

Pierrick
 
Hey Pierrick,

The first suspicion I have there is that you may have somehow disconnected the entire feedback
section of the channel that is now clipping while desoldering that cap, which would make it amplify
as much as it can and explain the behavior - what made you want to desolder the 100p cap in the first
place? It belongs in there - only the 100n caps in the signal path are optional components.

Anyway, check around the 100p cap - it's highly unlikely you would get that kind of behavior from
components in that region damaged by soldering, more likely you would get it from an open feedback
loop because contact is broken somewhere.
 
HI Lukas,

my explanation wasn't so clear, so in fact I've just desolder one leg of the 100p cap following your wiring guide instructions, and connected it to the lifted leg of the 15k resistor. I did it on both sides and I connected there my wet signals, left and right respectively as explained. I connected the out signals to 2 of the 4 free holes, also as explained in your guide. I double checked, even triple checked the wirings, changed the 100p cap, but the problem remained the same after a second test in my studio. I went back home, opened the unit and fired it up. What i've noticed is that the led on the C N' B didn't light up.
 
And I forgot to tell that when testing the unit, the right side was compressing normally, clear sound, with compression or in bypass, but the C N' B had no effect, switching it in and off didn't changed anything, and turning the pot from dry to wet when C N' B on in position had no effect too.
 
After some inspections, I saw a short between my left out connection and one solder pad of the IC just near by (I took my out connections where the 100p cap's legs were lifted). So I have to make a test in my studio but that could explain the saturated signal on the left side. Also I got now the led of the C N' B lighting up.

Thanks for your help.
 
SO, unit tested this evening, and the problem remains almost the same. I still have the left side Saturating when C N' B is out, and right side compressing normally, but when I switch on the C N' B, I've got the same saturated signal on right side, so both side are saturating.
 

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