Cardinal Tremolo (Vactrol-base Harmonic Tremolo) - schematic & discussion

[midwayfair]

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

It's red and has a bird. <3

[Soup39]

I've been eagerly waiting this.  Just ordered..Thanks

[Liquitone]

Thanks for this article Midwayfair!
It will take some time to read through all the pages but I'm certainly going to try this one,.
I'm also interested in that 11 FET version you mentioned in the video.

This article inspired me to experiment with my uni-vibe based tremolo and I got some really interesting sounds out of it.
If there's any interest I can post it in a different tread as not to derail this one.

[drolo]

This article inspired me to experiment with my uni-vibe based tremolo and I got some really interesting sounds out of it.
If there's any interest I can post it in a different tread as not to derail this one.

I would definitely like to have a look at that :-)

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

[midwayfair]

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

As noted above, the Eagle files are on Pedal Geeks United. I won't be printing a run in part because it would compete with Josh's (1776's) PCB run of the standard circuit and partly because it's such an expensive board to populate, but if someone else wants to make themselves a couple from OSH Park, they're welcome to do so with impunity as long as it's not a commercial endeavor.

[drolo]

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

Any plans to publish the PCB for the TAPLFO version?

As noted above, the Eagle files are on Pedal Geeks United. I won't be printing a run in part because it would compete with Josh's (1776's) PCB run of the standard circuit and partly because it's such an expensive board to populate, but if someone else wants to make themselves a couple from OSH Park, they're welcome to do so with impunity as long as it's not a commercial endeavor.

Thanks Jon, that's great :-)

[drolo]

Jon, I am trying to cook something up inspired by your circuit and was having a look at the low pass frequency you use to have something to start with. You mention your lowpass cuts at 723Hz, but with the 10k and 2n2 in your schematic, I get the result 7.23kHz. Is that maybe a typo? (22n would normally result in 723 Hz) Or maybe I am calcuating this wrong ... Sorry if I am missing some obvious detail

[duck_arse]

drolo, I had the same question, lost in the thread noise ......

http://www.diystompboxes.com/smfforum/index.php?topic=101722.msg902991#msg902991

[drolo]

drolo, I had the same question, lost in the thread noise ......

http://www.diystompboxes.com/smfforum/index.php?topic=101722.msg902991#msg902991

oh I had missed that .. thanks  :-)

[GGBB]

A couple of quick questions about the wave and volume pots.  For external pots, what taper is best - I assume audio for volume but not sure about wave?  Do wave adjustments affect the volume?  I think I can live without a volume control, but I'm not sure if having the external wave pot will allow me to make adjustments that will end up needing a volume correction.

[midwayfair]

A couple of quick questions about the wave and volume pots.  For external pots, what taper is best - I assume audio for volume but not sure about wave?  Do wave adjustments affect the volume?  I think I can live without a volume control, but I'm not sure if having the external wave pot will allow me to make adjustments that will end up needing a volume correction.

Linear for both pots.

The volume isn't really necessary, but there's a bunch of boost available if you want to use it as a preamp. The wave pot is really nice if you want the mode switch.

[GGBB]

Linear for both pots.

The volume isn't really necessary, but there's a bunch of boost available if you want to use it as a preamp. The wave pot is really nice if you want the mode switch.

Thanks Jon.  I am itching to build this (my 10th Ann. prize) as soon as I get some free time.  I absolutely love the demos I've heard.

I believe you did a tap-tempo version of this right?  Can that be done using the 1776 PCB along with a second board?

EDIT:  Never mind - found the answer on your original schematic.  Awesome!

[midwayfair]

This is the Univibe mod! Very exciting.

THEORETICAL

So, Dane Kinser (eldanko) over on Madbean accidentally discovered that you can make the Cardinal sound like a vibe by replacing C6 with a much bigger cap, in his case 33nF. This got me thinking whether we could use a single toggle to replace the center mode with the vibe mode.

It requires a DPDT on/on/on.

It's wired thusly:
DPDT on/on/on
1 4
2 5
3 6

-Jumper 1 and 5.

-Replace R6 on the PCB with a much larger value, e.g. 33nF.

2: This is the ground connection (pad 2).

3: This connects to the pad on the PCB that goes to C6 (pad 1)

4: This connects to the pad on the PCB that connects to the gate of Q3 (pad 3)

-Solder a smaller value cap across lugs 3 and 6. (See below for values and cutoff frequencies.) We will call this the "switched" cap.

The modes will now be:

Up/right - Normal tremolo
Center - Harmonic
Down/left - Vibe

How this works:

In the center, C6 + switched cap create series capacitance.

When the switch is up/right, the emiter of Q3 is connected to lug 5, which is jumpered (internally) to lug 1, which is now connected to the ground connection.

When the switch is down/left, C6 is connected to ground, and the cap across lugs 3&6 are disconnected.

Switched + C6 cap values and calculations:

-2.7nF + 33nF will equal ~2.5 nanofarads. Cutoff frequency will be 6366. This isn't that close to the original 7234, but remember that we're dealing with harmonics and it's better to go a little lower rather than higher with the cutoff.
-3.9nF + 33nF will equal ~3.5 nanofarrads. Cutoff frequency will be 4547 (not too far from Dane's 4822 with a 3.3nF)

R5 could be (VERY) mildly adjusted as well if you want to hit a particular cutoff frequency. For instance, if you want to get even closer to the cutoff frequency of the stock values, you can use a 9.1K with 33nF and 2.7nF caps to get a cutoff of 6995. Or to get really really close to Dane's original cutoff, you can use an 8.2 with 33nF and 4.7nF caps.

It would be best to experiment with the larger value cap in C6 first to get the vibe sound you want and then calculate the switched cap based on that.

I will give this a go in one of my builds, maybe in the tap tempo version since I need to open it up to add Josh's optical bypass to it.

Thanks to everyone in the switch thread that showed me the DPDT on/on/ons (armdnrdy, GGBB, slacker).

[GGBB]

This is awesome Jon!  But I just built mine over the weekend - doh! 

It requires a DPDT on/on/on. Croquet hoop noted that there may be two types of DPDT on/on/on switches. You need the kind with an internal jumper across lugs 1 and 5. This is apparently most of them, but be sure to check.

Can you clarify that?  I've never run across any that were like that.  Are you going by the diagram I pointed to in the other thread?  There, the 1-5 connection is drawn in red and is meant to be added to the switch, not an internal connection.  Please clarify.

[midwayfair]

This is awesome Jon!  But I just built mine over the weekend - doh!  

It requires a DPDT on/on/on. Croquet hoop noted that there may be two types of DPDT on/on/on switches. You need the kind with an internal jumper across lugs 1 and 5. This is apparently most of them, but be sure to check.

Can you clarify that?  I've never run across any that were like that.  Are you going by the diagram I pointed to in the other thread?  There, the 1-5 connection is drawn in red and is meant to be added to the switch, not an internal connection.  Please clarify.

Oh, I thought it was internal. I'll fix that.

EDIT: If you already built yours, this shouldn't require redrilling or anything.

[GGBB]

Finally got around to firing this up and all I can say is wow!  Jon - this is a beautiful pedal - thanks for contributing this.  Now I want to build a tap tempo version.

Some notes from my build:

If you are using the 1776 Effects PCB, pay attention when installing the vactrols.  On the LED side, the anode is the square pad, not the other way around like one would expect.  This means that VTL5C1s will be installed label side down.  She don't make no nicey sounds if you get that wrong like I did at first. 

The vibe mod is really really nice.  I went with a 22n cap for C6 with a 2n7 on the switch.  I could have been equally as happy with a 33n for vibe mode (although if forced to choose I would have picked the 22n), but liked the 22n-2n7 combination a little better than the 33n-2n7 combination for harmonic mode, and actually preferred that to the stock 2n2 alone for harmonic.

I've decided to go with an external volume control as I found that in normal tremolo mode you can have so much depth that you need to bring the volume up to compensate.  The wave control can make this even more necessary.  It should be said that this is a pretty awesome sounding normal tremolo in addition to harmonic and vibe.

Everyone should have one of these.

[midwayfair]

Wow, thanks GGBB! Glad you like it, and thanks so much for verifying the Vibe mod.

[pinkjimiphoton]

I know most folks on DIYSB are all about etching and vero and such, but I just thought I'd stick a note here that 1776 Effects released the PCB project for this today: http://1776effects.com/store/

It's red and has a bird. <3

freekin' sweet, just ordered one. this looks like it woulda been a beetch to vero!!
can't wait to finally build this thing!!
thanks jon!!

[GGBB]

Wow, thanks GGBB! Glad you like it, and thanks so much for verifying the Vibe mod.

I should also add that I tried going bigger for the vibe mode - 68n and 100n (out of 47n at the moment).  But it's too far in the other direction and loses the effect.  22n or 33n seems to be the ticket.  And when you're in vibe mode, the wave control comes in really handy.  There's a really interesting interaction between the depth and wave controls in both harmonic and vibe modes - you can find a lot of different subtleties in there.

[midwayfair]

There's a really interesting interaction between the depth and wave controls in both harmonic and vibe modes - you can find a lot of different subtleties in there.

I would expect the triangle wave to have a tiny bit of the univibe's lope.

I'll get to hear it soon enough ... I'm putting the mod in a stereo tap tempo tremolo I'm making "because I could".