Baja Trembulator schematic, board layout and circuit board

mictester · Post by **mictester** » 03 Oct 2009, 00:38

sinner wrote:
mictester wrote:I'll forward my modified PCB design if anyone wants it.
Would you like to post it here?

Here's the Veroboard layout. It uses a TL062 for the audio path (low current, low noise, and two op-amps in the package). The second op-amp is used as a unity gain buffer, with a nice low output impedance which will drive long cables OK and isolates the gain control part from the next item it's connected to....

This is, quite simply, the very best tremelo I've heard.

There's no noise to speak of, no distortion, and a wide range of control!

Thanks Bajaman for another great design!

Louishr · Post by **Louishr** » 05 Oct 2009, 03:07

Hey guys, Here's the fix to my layout, I posted it a while ago somewhere else on the forum and forgot I had posted here as well, This layout works just fine.

devastator · Post by **devastator** » 13 Oct 2009, 16:44

Hi folks

I started working on mine, but I would like to add a gain stage and a volume in the end. I'm thinking about building a simple gain stage with AOP but I'm not really an expert about biasing. Like the low impedance coming from the AOP (tremolo) I can just put a 100K resistor to connect the AOP enter to VR, right ?

mictester · Post by **mictester** » 17 Oct 2009, 14:27

devastator wrote:Hi folks

I started working on mine, but I would like to add a gain stage and a volume in the end. I'm thinking about building a simple gain stage with AOP but I'm not really an expert about biasing. Like the low impedance coming from the AOP (tremolo) I can just put a 100K resistor to connect the AOP enter to VR, right ?

If you use my modified version, you can use the output op-amp as a gain stage. If you make the feedback resistor a variable, you can vary the gain! If the mod isn't obvious, I'll post an amended diagram in this thread.

The reason for the additional op-amp stage originally was to separate the gain control element (the depth pot and the LDR) from the equipment following it. I found that the "raw" version could be adversely affected by the loading presented by other equipment, so a lowered output impedance seemed a good idea.

devastator · Post by **devastator** » 17 Oct 2009, 19:40

I didn't see your modified version actually. Yeah that looks like identical.

Here's what I'd like to add on mine. Juste a volume knob to adjust the level and have a boost if need it. I copied the micro amp boost :

But I've some doubt about the frequency corner formed by C1/R1, I think It's ok to have all frequencies (the cut is really low) but I don't know what values putting to baising the "+" input. If the impedance is low I can put a low resistors but I'm not really sure about that (I always use high values (470K/1M) in ovedrive/distortion circuit).

I could change the 4K7 for a 5K trimer and set the volume boost.

In seing your post , creating a buffer to separate the tremolo circuit and the boost could be great too.

Plus I think the gain will be about 47, maybe too lood for a volume pot in tremolo circuit.

el pucho · Post by **el pucho** » 17 Oct 2009, 23:52

Hi,

I'm going to build this pedal using mictester's layout and have a quick query. Would any of these LDR's be suitable. I'm not sure how much your choice of LDR influences the sound, if at all.

http://www.rshelectronics.co.uk/otheropto.htm

Also, what does the 10k trimpot do?

Thanks to everyone who put in all the work on this pedal, looking forward to trying it out!

devastator · Post by **devastator** » 18 Oct 2009, 16:21

Guys Which trimpot I must buy :

http://www.banzaimusic.com/Trimpots/

I don't know the good one to put it perfectely in the PCB holes.

Thanks.

Geosh · Post by **Geosh** » 20 Oct 2009, 17:45

mictester wrote:
Here's the Veroboard layout. It uses a TL062 for the audio path (low current, low noise, and two op-amps in the package). The second op-amp is used as a unity gain buffer, with a nice low output impedance which will drive long cables OK and isolates the gain control part from the next item it's connected to....

Do you have the schematic that goes along with this vero? I am trying to get better at understanding the schematics rather than just copying someones layout and I was having issues tracing this layout to the schematic that you previously posted. Maybe it was too late last night and my brain had gone to sleep before I did, but hopefully they are different.

Thanks!!

mictester · Post by **mictester** » 26 Oct 2009, 23:02

The schematic is about 12 posts earlier up the thread! I hope your Vero build goes OK.

Ben N · Post by **Ben N** » 27 Oct 2009, 12:50

Louishr wrote:Hey guys, Here's the fix to my layout, I posted it a while ago somewhere else on the forum and forgot I had posted here as well, This layout works just fine.

Why two boards?

mictester · Post by **mictester** » 27 Oct 2009, 19:13

el pucho wrote:Hi,

Also, what does the 10k trimpot do?

It sets the maximum LED current. Start with the depth pot at maximum, and the rate set at its slowest and the preset set to MAXIMUM resistance. Put in a tone, and advance the preset until the depth is such that the signal just completely disappears during each cycle. The preset is then correctly set, and the maximum current through the LED is set as low as it can go (guaranteeing long life for the LED, and minimising battery consumption).

Louishr · Post by **Louishr** » 02 Nov 2009, 19:12

i used two boards because I combined this with a zvex style sequencer, but the multiple boards let me squeeze it into a small box

el pucho · Post by **el pucho** » 03 Nov 2009, 15:56

Thanks for the info Mictester, getting the parts ordered today so hopefully have this up and running soon.

devastator · Post by **devastator** » 06 Nov 2009, 18:05

I've jsut finished mine, it sounds really good.

I'll just add a tiny boost stage at the end to put a volume knob in the third hole in the box.

devastator · Post by **devastator** » 08 Nov 2009, 16:51

Completed !

el pucho · Post by **el pucho** » 08 Nov 2009, 17:29

It must be the day to build these, just finished too!

I built using Mictester's layout and maybe spotted a couple of errors.

I think the status LED should be connected to the row below the one stated in the layout, so it connects to the 4k7 resistor, and not the 1k as shown.

Also I think the 10k trim pot is wrong. I ended up connecting lugs 3 & 2 together then used a jumper to connect lug 1 to the 1k resistor. If I'm reading it correctly the way it is in the layout means the signal has nowhere to go after going through the 10k trim pot.

I might be totally wrong as I'm not very knowledgable when it comes to building these things.

A couple of other things: I think I'm getting a bosst in volume with this pedal on, is there any way I can add a volume control?
I also quite fancied a hard/soft switch, but I'm not really sure how to do this.

It's sounding like a huge upgrade to my EA Tremolo so far, thanks to Baja, and anyone else who contributed to this.

phibes · Post by **phibes** » 08 Nov 2009, 18:36

For the hard/soft switch just hook a switch up to jumper out the trimpot. It'll get very choppy.

I did a few other things to this and I love it. For a faster speed without going to overboard I changed the resistor in series before the rate pot to 1K and then changed the pot to a 25K lin. I also changed a few things for the depth that Baja wrote in another thread. I changed the 1uf bipolar after the 1.8k resistor to a 4.7uf and then changed the pot to a 10k lin. Try em out.

mictester · Post by **mictester** » 08 Nov 2009, 18:40

el pucho wrote:It must be the day to build these, just finished too!

I built using Mictester's layout and maybe spotted a couple of errors.

I think the status LED should be connected to the row below the one stated in the layout, so it connects to the 4k7 resistor, and not the 1k as shown.

Also I think the 10k trim pot is wrong. I ended up connecting lugs 3 & 2 together then used a jumper to connect lug 1 to the 1k resistor. If I'm reading it correctly the way it is in the layout means the signal has nowhere to go after going through the 10k trim pot.

You're completely right! The layout below is the corrected one!

The LED is fed via the 4k7 resistor, and the preset connects to Pin 6 below through the 1k.

I must have been tired when I put that layout up. Sorry!

el pucho · Post by **el pucho** » 08 Nov 2009, 19:14

No problem mictester, more thank you for putting up the alyout I'd be completely lost trying to plan a layout from a schematic.

I don't seem to be getting anywhere with the hard/soft thing. Is it the 18k resistor I need to jumper out, or the 10k trimpot (I used mictester's layout)?

Thanks for the tips Phibes, I'm going to mess around with those speed combinations and see what suits me best, a little faster would be nice.

About the volume control, could I just add a pot between the output of the circuit and the output jack? Or is there a resitor somewhere that controls the output volume?

The other thing I noticed is mt Depth pot seems to work backwards, turned up to 10 gives no effect and at 0 gives full effect. Is this normal?

I want to try and finish this tonight and get it boxed up, problem is I can't stop playing through it and get back to working on it.

Cheers again guys.

phibes · Post by **phibes** » 08 Nov 2009, 20:56

el pucho wrote:No problem mictester, more thank you for putting up the alyout I'd be completely lost trying to plan a layout from a schematic.

I don't seem to be getting anywhere with the hard/soft thing. Is it the 18k resistor I need to jumper out, or the 10k trimpot (I used mictester's layout)?

Thanks for the tips Phibes, I'm going to mess around with those speed combinations and see what suits me best, a little faster would be nice.

About the volume control, could I just add a pot between the output of the circuit and the output jack? Or is there a resitor somewhere that controls the output volume?

The other thing I noticed is mt Depth pot seems to work backwards, turned up to 10 gives no effect and at 0 gives full effect. Is this normal?

I want to try and finish this tonight and get it boxed up, problem is I can't stop playing through it and get back to working on it.

Cheers again guys.

The 10k trimpot is what needs to be jumped. Mr. Fuller does his that way.

Sounds like you wired your depth knob backwards.

Baja Trembulator schematic, board layout and circuit board [documentation]