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 Forum index » DIY Hardware and Software » Ken Stone designs - CGS
CGS/Bridechamber Wave Multiplier
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Thu Mar 19, 2009 2:23 am    Post subject: CGS/Bridechamber Wave Multiplier Reply with quote  Mark this post and the followings unread

I recently bought the Bridechamber/CGS Wave Multiplier 2-PCB set. This 2-PCB combines the CGS Wave Multiplier and CGS Real Ring Mod Projects on the larger PCB and the CGS Grinder and CGS Simple (Lockhart) Wavefolder on the smaller PCB.

Now that I have installed 99% of the components and the PCB is almost ready to be tested, I have the following questions about the larger of the 2 PCBs (especially the Real Ring Modulator circuit).

1) Is there a schematic and/or wiring diagram available for the larger of the 2 PCBs in this set. (I'm talking about the PCB that contains the Real Ring Modulator and the Wave Multiplier?)

Since the Real Ring Modulator on the larger PCB has 4 op amps on 2 ICs and 4 trim pots associated with it, it is definitely more advanced than the original CGS Real Ring Modulator (CGSRR). It would really be nice to have a schematic for initial debugging purposes and future troubleshooting purposes.

2) In the lower right corner of the PCB (just left of the Unicorn's head) that are two unlabeled spaces that appear to be reserved for resistors. Either links or resistors must be inserted in these 2 spaces in order for external Audio and Carrier Inputs to be sent to the ring modulator.

Its only logical to assume that components (or links) should be inserted in these 2 unlabeled spaces. Is this correct? What components?

3) There is a remark printed on the PCB that says "T-RI 1 uF buffering for RM in." I'm a little confused about what "T-RI" means.

Perhaps it is referring to the "Triangle input". I did trace the connections on both sides of the 1uF capacitor and found that one of them went to the Audio In Trimpot of the Real Ring Modulator. I believe the other side of the 1uF capacitor connects to the input of the LM3080. Thus, if the schematic for CGS project CGS29 (Wave Multiplier) applies to this drawing, it appears that the sum of the Triangle In, Square In, and the Manual and External Offsets are sent to the Audio Input of the Ring Modulator.

Again, a set of schematics or at least a wiring diagram would make this question a mute issue.

I would appreciate any additional documentation or assistance.

David
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Thu Mar 19, 2009 2:44 am    Post subject: Bridechamber's Matched Transformer and Diode Set Reply with quote  Mark this post and the followings unread

(Oops, I meant to place the following post in this folder instead of starting a separate folder.)

When I bought my Wave Multiplier PCB set from Bridechamber, I also purchased the Matched Transformers and German Diode set for the real Ring Modulator in this particular project.

When I was installing the diodes, I noticed that the diodes were "gold-doped diodes" instead of "germanium diodes". I also measured the forward voltage drop for each of these diodes and although all 4 diodes were equally matched, the forward voltage drop was 0.66 volts, which is consistent with gold-doped diodes, and not the 0.25 to 0.3 volts that one would find when measuring the forward voltage drop of a germanium diode.

There is a note on the PCB that says to use germanium diodes for the ring of the Real Ring Modulator. So I'm sure that this will effect the overall sound of the real ring modulator and its associated distortion.

Did anyone else who purchased this Transformer+Diode set from Bridechamber also get gold-doped diodes? How did this effect the overall sound?

David
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Tasmanian Alkaloid



Joined: Jun 29, 2008
Posts: 116
Location: Isle De Mort

PostPosted: Thu Mar 19, 2009 4:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi David,
i got the transformers & diodes in the Wave Multiplier/RRM kit, but they are the only things i haven't stuffed yet. I'm not sure what my diodes are- they are red bodied with a black top. I can't read the code without a magnifying glass (which i don't have).
With regards to wiring, i also was stumped, but have you tried working it out from the wiring schematic from Ken's website? That's what i'm about to do myself, in the next day or so.
In answer to your other questions- i saw a photo of a finished module of this, and the two spaces near the unicorn's head were left empty. If you look at the traces, they both go to an unmarked pad. One is in fact connected to nothing, while the other trace runs to another resistor. Unless i'm wrong, i don't think they're for anything.
Also, as far as i can tell, T-RI stands for (T)ri to(-) (R)ing (I)nput.
Hope that helps.
-Matt
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Thu Mar 19, 2009 11:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Matt,
Thanks for the reply. I knew others had to have similar questions.

>>i got the transformers & diodes in the Wave Multiplier/RRM kit, but they are the only things i haven't stuffed yet. I'm not sure what my diodes are- they are red bodied with a black top. <<

The Ring Modulator diodes I got from Bridechamber are a reddish copper (or reddish gold) color with a black band at one end. (So mine may be similar to yours.) They look almost identical to the common 1N914 (or 1N4148) switching diodes that are used in the Wave Multiplier circuit as well as many of the other synth modules.

I used to have some 1N34A Germanium diodes that were made of clear plastic with a black band at one end, but recently I ran across a few germanium diodes that also look like 1N914 switching diodes (reddish copper with a black band). So you can't tell always tell if a diode is a Germanium diode by looking at it.

The best way to distinguish these two types of diodes is by measuring the (forward) voltage drop across the diode. The voltage drop across a switching diode is usually between 0.6 and 0.7 Volts whereas the voltage drop across a germanium diode can range from 0.2 to 0.4 volts.

The easiest way to measure the voltage drop across a diode is use a volt-ohm multimeter. Unless you have a really old multimeter, you should have a diode position on the dial that you use to select the volt/ohm range. The diodes I received from Bridechamber had a forward voltage drop of around 620 mV (0.62 Volts). If the diodes were Germanium type diodes, the forward voltage drop would have been about 0.2 to 0.4 Volts (or 200 to 400mV).

>>With regards to wiring, i also was stumped, but have you tried working it out from the wiring schematic from Ken's website? That's what i'm about to do myself, in the next day or so. <<The>>In answer to your other questions- i saw a photo of a finished module of this, and the two spaces near the unicorn's head were left empty. If you look at the traces, they both go to an unmarked pad. One is in fact connected to nothing, while the other trace runs to another resistor. Unless i'm wrong, i don't think they're for anything.<<

Are you talking about the picture on the Bridechamber website (go to http://www.bridechamber.com/bridechamber.com/WM%20PCB.html )? While the module looks to be complete, it isn't? The PCB looks exactly like my module right now except I have already installed IC sockets. (Although there are place holders for them, the IC, or IC sockets, have not yet been installed on the PCB shown in the picture.) The wiring is incomplete also since there are no connections to the input jacks nor are there any power connections. (Shouldn't the smaller PCB get its power from the larger PCB via a connection between the two PCBs?)

Even more important, have you noticed the silkscreen of the PCB that is posted on the Bridechamber website? (Go to http://www.bridechamber.com/bridechamber.com/WM%20PCB_files/wm%20screen.GIF ).

On the silkscreen of this PCB you will see that these same two "unmarked pads" that appear on the PCB are marked "RM (Ring Mod) In" and "CA (Carrier) In" on the drawing of the PCB silkscreen. According to the silkscreen drawing these 2 pads are for an external Audio In and a Carrier In) to the ring modulator. I verified this by tracing the traces. (Of course, the big question is this: Why does the actual PCB differ from the PCB silkscreen that is posted?)

Further complicating the matter is the fact that the silkscreen, like the PCB, fails to show values for the 2 unmarked resistors that I mentioned in my original post. Resistors, or links, must be inserted in these spaces in order to connect these 2 input pads to the ring modulator circuit. Thus, what suppose to go here?

Thanks for your comments, Matt. I appreciate your interest. Hopefully, Ken or Scott can provide some answers to these questions.

David
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Tasmanian Alkaloid



Joined: Jun 29, 2008
Posts: 116
Location: Isle De Mort

PostPosted: Thu Mar 19, 2009 1:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

I measured my diodes at around 700mv each. They look like the IN4148's (reddish copper with black band), but i can't read the code.
I reckon the two pcb's are connected between the small +ve, 0v & -ve pads on the edge of each of the boards.
I think you may have misread those RM In CA In pads- on my pcb, the letters R & C respectively have been covered by the silver of the pads- if you compare the Bridechamber pcb layout and the actual pcb, it's clear. The 2 unmarked pads are still a mystery- i'd suggest finishing up the module then it'll be obvious if they were meant to be used.
Have you thought of mounting your pots straight on the pcb (no wiring!). I think that's what i'll do. On Ken's Wave Multiplier page, most of the jacks' ground lugs are connected to each other and grounded once at the board. This will probably have to be done here as well.
When i got my component kit from Bridechamber, nothing was provided for the two unmarked resistors- i also wondered what they were for, so i guess they are in fact meant to be empty.
-Matt
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camelneck



Joined: Sep 27, 2008
Posts: 68
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PostPosted: Fri Mar 20, 2009 11:27 am    Post subject: Reply with quote  Mark this post and the followings unread

>>I think you may have misread those RM In CA In pads- on my pcb, the letters R & C respectively have been covered by the silver of the pads- if you compare the Bridechamber pcb layout and the actual pcb, it's clear. The 2 unmarked pads are still a mystery- i'd suggest finishing up the module then it'll be obvious if they were meant to be used. <<Matt>>The 2 unmarked pads are still a mystery- i'd suggest finishing up the module then it'll be obvious if they were meant to be used.<<You>> I reckon the two pcb's are connected between the small +ve, 0v & -ve pads on the edge of each of the boards. <<That>>Have you thought of mounting your pots straight on the pcb (no wiring!). <<That>>On Ken's Wave Multiplier page, most of the jacks' ground lugs are connected to each other and grounded once at the board. This will probably have to be done here as well.<<Right>>When i got my component kit from Bridechamber, nothing was provided for the two unmarked resistors- i also wondered what they were for, so i guess they are in fact meant to be empty. <<

Right. Unless you want to add multiple ring mod inputs. You could have one set of inputs, say a set of keyboard inputs, set up for a level that is preset by the "In Lev" and "Car Lev" trimmers. You could install pots in these locations so another set of inputs could be used for a guitar, for example.

I WOULD STILL LOVE TO HAVE A SCHEMATIC OF THE RING MOD CIRCUIT JUST IN CASE ANYBODY IS KIND ENOUGH TO PROVIDE ONE!

David
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camelneck



Joined: Sep 27, 2008
Posts: 68
Location: KY (USA)

PostPosted: Fri Mar 20, 2009 12:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Matt,
In regards to the reply that I just made to your last post, well, over half of it didn't show up. I guess it read the arrows that I put around the "quotations from your previous post" as html codes.

You wrote,
"I think you may have misread those RM In CA In pads- on my pcb, the letters R & C respectively have been covered by the silver of the pads- if you compare the Bridechamber pcb layout and the actual pcb, it's clear."

You are right. I must have had a case of temporary dyslexia. (I had also mounted a MTA-100 connector which covers the label in question.) The RM In and CA In pads go to the two resistors that are above the 2 unmarked locations.

Last night, I spent over an hour trying to map the traces in an attempt to make my own schematic of the ring mod circuit. Unfortunately, I was only partially successful. Since there are traces on both sides of the PCB and since I have all of my components mounted on the PCB, I couldn't follow many of the top side traces due to the transformers, trimmers, and IC sockets. I documented the 2 op amp connections, but I couldn't follow the 4 traces that connect the op amp portion of the ring mod circuit to the transformer/diode ring section of the circuit. So I guess I will have to either forget the modifications, I wanted to make to the ring mod circuit or resort to trial and error.

"I reckon the two pcb's are connected between the small +ve, 0v & -ve pads on the edge of each of the boards."

Exactly.

"Have you thought of mounting your pots straight on the pcb (no wiring!). On Ken's Wave Multiplier page, most of the jacks' ground lugs are connected to each other and grounded once at the board. This will probably have to be done here as well."

I'm also going to mount the 7 designated pots to the PCB. Ken's wiring drawing on his Wave Multiplier page should be correct for everything but the ring mod circuit.

"The 2 unmarked pads are still a mystery."

Indeed they are. Perhaps they are for a secondary set of inputs to the ring modulator since they do connect to the ring modulator if resistors or links are placed in those 2 unlabeled locations. Most people will probably just ignore them.

However, they (or at least one of them) could be used if you want to add multiple ring mod and/or carrier inputs. You could set-up the levels for the first set of inputs for your synth level inputs. The other set of inputs could be set differently ... say for a guitar.

I WOULD STILL LOVE TO HAVE A SCHEMATIC OF THE RING MOD CIRCUIT JUST IN CASE ANYBODY IS KIND ENOUGH TO PROVIDE ONE! It doesn't have to be a perfect drawing ... I'll settle for a rough sketch.

David
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Luka



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PostPosted: Tue Mar 24, 2009 3:48 am    Post subject: Reply with quote  Mark this post and the followings unread

did you look at the cgs website at all?

Posted Image, might have been reduced in size. Click Image to view fullscreen.

should be pretty easy to work out

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MR-808



Joined: Sep 30, 2010
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PostPosted: Fri Feb 24, 2012 3:18 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm in the process of trying to figure this thing out. Documentation is sketchy - Scott told me that even he doesn't have a schematic for it!

I took the CGS67 schematic and compared it to the PCB. Not exhaustively, so there may be errors. I've attached my edit below. Notes:

* I deleted the TL071 and the associated input circuit in the original schematic.
* The 330Rs are now 220Rs.
* The 25k trimpots are now 100k.
* The output level pot is now a 100k resistor.
* The area circled on the left is not on the PCB, but I left it on the schematic because I'm contemplating if and how I want to modify the circuit to better utilize the ring modulator.

I'm leaning towards adding a couple of switches - one to select AC or DC coupling on the CARRIER IN, and another to select the wave folder offset or the carrier unbalance as the destination for the OFFSET pot.


schem_cgs67_rrm3.gif
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MR-808



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PostPosted: Fri Feb 24, 2012 3:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Also, here's a copy of the silkscreen file that Scott gave me. Given how bad the layout is and the lack of an official schematic, I think it's pretty necessary for stuffing the PCBs!


cgs_wm_screen.gif
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MR-808



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PostPosted: Fri Feb 24, 2012 3:35 am    Post subject: Re: CGS/Bridechamber Wave Multiplier Reply with quote  Mark this post and the followings unread

camelneck wrote:
Its only logical to assume that components (or links) should be inserted in these 2 unlabeled spaces. Is this correct?


One goes to the signal summing node, the other to the carrier summing node. If you're using the Bridechamber panel, I wouldn't stuff either. In fact, I wouldn't stuff the RM IN 100k, either, just the CA IN one.

I'll probably used the space tied to the carrier node for a 330k resistor that goes to a switch to change the OFFSET pot to an UNBALANCE pot (see my previous comment). I'm sure that the intent behind putting the spaces on the PCB were to make mods such as this easier.
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