Tap tempo modded Echo Base PCBs in the works - vote on features

[slacker]

Yep, it's looking like you'll have the ability to do parallel and series, but it will require a 4PDT toggle switch,

Why? You can do parallel/series switching with a DPDT, or are you using the extra poles to switch other things?

[slacker]

Is there a way to have it either be a mix pot or a level pot? Like depending on the builders desire? Or is that a part of the PCB that's either one or the other.

Is there a reason you'd prefer a level pot to a mix pot? Originally I wanted as much flexibility as possible, but as the board gets more complex, this is harder to maintain. I'm thinking I will go with one or the other. The Mix pot seems more versatile to me. What do you think?

You can give the builder the option of having delay level or a mix control fairly easily, it just needs a couple of extra solder pads adding to the original schematic, I'll knock up a drawing. If you go with a mix control though there's no way you can use the original switching, you'd either have to true bypass it or use buffered bypass, but either way you'd lose the tails feature.

Personally I don't see the appeal of a mix control, but if it's is something a lot of people wanted I could have a go at redesigning the switching to allow for it and keep the tails feature.

[Taylor]

Why? You can do parallel/series switching with a DPDT, or are you using the extra poles to switch other things?

Well, I'd love to see how you'd do it. Here's what I worked out.

We need to switch these things:

In parallel mode, the output from the input 4066 switch needs to go to the inputs of both PT2399s. In series mode, the input to the second delay chip needs to be cut out.

In parallel, the output from the first delay needs to go to its own feedback knob (half of a dual gang pot) which then goes to the input of the same delay. In series mode the output of the first delay needs to be switched to go into the second delay's input.

In parallel mode, the output from the second delay chip needs to be fed into the input of the same chip. In series, the out from the second chip needs to be fed back to the in of the first chip.

The PTAP has a series/parallel mode switch that needs to be switched simultaneously.

I'm definitely no guru, so if anyone can think of a more efficient way to switch all this, it would be great.

[Taylor]

You can give the builder the option of having delay level or a mix control fairly easily, it just needs a couple of extra solder pads adding to the original schematic, I'll knock up a drawing. If you go with a mix control though there's no way you can use the original switching, you'd either have to true bypass it or use buffered bypass, but either way you'd lose the tails feature.

Personally I don't see the appeal of a mix control, but if it's is something a lot of people wanted I could have a go at redesigning the switching to allow for it and keep the tails feature.

I do want to keep the tails and switching. I have a schem that somebody did that incorporates a mix knob at the opamps, didn't change the switching, is there some reason that doesn't work? Can't find the schematic right now, but it's buried in the Echo Base thread.

I would just like the ability to cut the clean signal to get vibrato sounds. Even a switch to kill the clean would be useful to me.

[slacker]

Why? You can do parallel/series switching with a DPDT, or are you using the extra poles to switch other things?

Well, I'd love to see how you'd do it. Here's what I worked out.

My thought was just to switch the inputs and outputs of the delays between series and parallel, which you can do with a DPDT, I hadn't thought about the extra stuff you're switching. I was thinking of having separate feedback pots and connecting them both back to the input of the first delay. That way in series you can tap the feedback from either the first delay or the second or a mixture of both.

I do want to keep the tails and switching. I have a schem that somebody did that incorporates a mix knob at the opamps, didn't change the switching, is there some reason that doesn't work?

I can't remember what the person who posted the mix pot mod did, so I might be wrong and it might work fine, I'll have a look at it.
My concern is that in the original design the dry signal goes through the pedal unaffected by the the bypass switching, this only affects the delayed signal. If you add a mix pot then potentially you're changing the level of the dry signal which means the bypassed volume will change depending on where the mix pot is set, in a worst case if you had 100% wet and then bypassed the effect you'd get silence.

[slacker]

Here's the mix pot mod from the Echo Base thread http://www.diystompboxes.com/smfforum/index.php?topic=60662.msg556933#msg556933 looks like it was meant to be used with true bypass, it definitely won't work properly with the original switching.

I think I've come up with a way to do a mix pot that will allow anything from 100% dry to 100% wet and let you keep the tails, it just means using a DPDT stomp for the bypass which doesn't seem like a problem to me. I'll have to breadboard it to see if it works, if it does I'll post a schematic.

[Taylor]

Here's the mix pot mod from the Echo Base thread http://www.diystompboxes.com/smfforum/index.php?topic=60662.msg556933#msg556933 looks like it was meant to be used with true bypass, it definitely won't work properly with the original switching.

I think I've come up with a way to do a mix pot that will allow anything from 100% dry to 100% wet and let you keep the tails, it just means using a DPDT stomp for the bypass which doesn't seem like a problem to me. I'll have to breadboard it to see if it works, if it does I'll post a schematic.

Cool! I assume most people would be using a DPDT at least anyway, since SPST latching switches are less commonly available than DPDT stomps.

My thought was just to switch the inputs and outputs of the delays between series and parallel, which you can do with a DPDT, I hadn't thought about the extra stuff you're switching. I was thinking of having separate feedback pots and connecting them both back to the input of the first delay. That way in series you can tap the feedback from either the first delay or the second or a mixture of both.

I did a little simulation on my computer, and doing it this way makes the echos stack up arhythmically until they become really diffused and sound like a reverb. The way I'm doing it is the only way I could come up with while allowing the delays to act right. The 4PDT is going to be board-mounted, so you won't have to deal with wiring such a monster.

[slacker]

Here's a quick schematic of the mix pot idea, I simulated it and it seems to work ok, I'll see if I can try it out at the weekend. The switch would be part of the bypass stomp. It might be possible to use the spare CD4066 switch instead, that would be a bit more complicated and probably not worth the effort. If it works it would be easy to build either this or the level pot using the same PCB layout.



When the effect is on the switch would be closed shorting the 1M resistor and the mix pot would then give you anything from 100% wet to 100% dry. In bypass the switch would be open and the 1M resistor then basically isolates the dry signal from the pot so you get the straight dry signal with the tails mixed in at what ever level they are set at by the pot.
That's the theory anyway

[Skruffyhound]

I think you are onto something with the standard board and the turbo board Taylor. I  may not be so interested in the standard E.B. having built it already, but there's new builders arriving all the time who I believe would appreciate it. Perhaps a new newb-friendly thread when you are ready with it. It's a complicated build to perf, so it requires the ability to etch and not everybody has that option to begin with.
That way you could push this turbo board to the limit. Compact is good, but don't restrict the board size at the expense of useful features.

I'll put it in a rack if I have to.

+1
Looking forward to another cool pedal, thanks Taylor.
@ Ian, great you can find time to help with this.

[aziltz]

Hey Taylor, the BYOC Ping Pong does the series/parallel switch via toggle in mono.  Perhaps checking out that schem might help?  They keep em posted in their build instructions.

-Austin

[Taylor]

Hey Taylor, the BYOC Ping Pong does the series/parallel switch via toggle in mono.  Perhaps checking out that schem might help?  They keep em posted in their build instructions.

-Austin

Yep, I've looked at their switching setup. Don't want to say negative things because I guess in a weird way I'm now a "competitor" of theirs (I don't see it that way, but somebody might), but the way they do it isn't really satisfactory for my purposes. The reason is that it doesn't allow any feedback for one of the delay lines in parallel mode. So it wouldn't allow you to do the cool 3-against-4 rhythmic repeats or the "The Edge" thing with 2 repeating delays at different multiples of each other.

Their setup gives you one repeating delay and the other delay just repeats once and that's it. Plus, they still do it with a 3PDT, and they don't have to switch the PTAP, so not only is their switch less capable but it's also less efficient with poles. 

So their thing is perfectly respectable and it does its own thing which is cool, but it's too limited for my tastes. If you're going to go to the trouble of doing a dual delay, you may as well go the whole nine with it, right?

[aziltz]

oh ic.  I haven't built it, only looked at it briefly, but I agree we should go the distance!

[slacker]

I got chance to try out the mixer idea I posted earlier and it seems to do what we want. Some of the values will probably need tweaking to get the best balance of the wet and dry signals and maintain a constant volume between bypassed and effected but it basically works. Even hooked up with a bunch of crocodile clips there's no popping or other nasties when switching and tails work like on the original.

I have to admit the 100% wet setting is pretty cool for vibrato sounds and the chorus sounds seem a bit easier to dial in.

[Taylor]

I got chance to try out the mixer idea I posted earlier and it seems to do what we want. Some of the values will probably need tweaking to get the best balance of the wet and dry signals and maintain a constant volume between bypassed and effected but it basically works. Even hooked up with a bunch of crocodile clips there's no popping or other nasties when switching and tails work like on the original.

I have to admit the 100% wet setting is pretty cool for vibrato sounds and the chorus sounds seem a bit easier to dial in.

Very cool, I will have to incorporate into the PCB.

I have set aside the "gigantor" PCB for a second, because it was getting a little taxing on my brain. PCB layouts are much like complex puzzles and you know how it goes when you work on the same puzzle for weeks - you really need to put it down and come back to have a clear head about it. 

In the meantime I completed a simpler Echo Base board. It has the updated input and output sections for cleaner operation, less hiss. It's got just a couple of little mods that don't take up room (the status LED flashes with the LFO, there's an option for an LFO kill switch), but other than that it's stock. Best of all it, it will fit, with stomp switch, jacks, etc. in a 1590B box, oriented landscape style ala ZVex.

On the Gigantor front, I heard back from Steve at Small Bear regarding the dual PC mount pot. Good news: he's going to carry it. Bad news: he said "look for it in late Spring, early Summer".    I don't really want to design the board for a part that no one can get for 5 months. So I guess I'll go with optocouplers. 

[Skruffyhound]

What's special about the dual gang pot you want to use?  Is it a vertical mount with the long legs? Otherwise we could just accept that one pot needs to be wired and use a more common dual pot with lugs. Wouldn't a vertical mounting dual sit higher than the other pots anyway. Can't see the problem, could you sketch the way you want to mount it?

[bluesdevil]

What's special about the dual gang pot you want to use?  Is it a vertical mount with the long legs? Otherwise we could just accept that one pot needs to be wired and use a more common dual pot with lugs. Wouldn't a vertical mounting dual sit higher than the other pots anyway. Can't see the problem, could you sketch the way you want to mount it?

+1
Design to wire in a standard lug dual pot and focus on the more ambitious "Gigantor" model... something worth getting excited about.
Small boxes are for small men.

[Taylor]

Hmm, ok. I just hate offboard wiring - it's so much faster and cleaner to do board-mounted pots, but that's just me.

So you guys would prefer to wire a solder lug dual pot than use optocouplers?

[Skruffyhound]

Generally I'm in favour of PCB mount everything, but since I can't see how this vertical mount dual pot will align with the other pots anyway then I could make an exception and wire 6 lugs. So yes I'd prefer the pot to opto's

[Taylor]

Generally I'm in favour of PCB mount everything, but since I can't see how this vertical mount dual pot will align with the other pots anyway then I could make an exception and wire 6 lugs. So yes I'd prefer the pot to opto's

Check out the drawing, it's the last one on this page:

http://www.taiwanalpha.com/english/p_e_50.htm

Then compare to the penultimate pot on this page:

http://www.taiwanalpha.com/english/p_e_49.htm

The pot body is slightly larger on the dual pot, but the distance between the top of the body to the pins is the same. It should line up right, but there could be some little thing that I'm not envisioning properly. The pots in this case will not sit against the board, but sort of hang off the side (disregard the negative mechanical connotations of the word "hang" - it should be quite sturdy).

Just out curiosity, what about optos do you object to? I realize they are not really accurate for things that need to be really matched, but in this case it's just for the 2 feedback pots, which in my experience it's not really a big deal if the feedback of the 2 sides isn't perfectly matched - since there's no option for stereo operation here, I doubt anyone will use the 2 sides set to the same speed, so you won't notice if they have slightly different feedback amounts.

[bluesdevil]

I'm not in the habit of building with mounted pots anyway 'cause I like the freedom of placement (in a larger enclosure) , so soldering up 6 lugs is nothing to get hung up on for me.
 My personal concern is I won't be able to buy a load of opto's to sort through if you go that route.
   Mainly I hope you don't lose patience and do the junior version. Looking forward to seeing how this ends up.