Echo Base - is it running right?

[ACS]

Hey all

Have built myself an Echo Base on the breadboard (first crack at breadboarding too!!)  but I have a couple of questions.  Have put together a 4min video that will show the questions I describe here:

1. I read that we expect the mod speed pot to change the delay time a bit aswell.  But the amount that it changes on mine seems excessive.  Confirm or deny normal behaviour?
2. When the mod depth is set to maximum and the delay time pot to minimum or close to, the mod works as I'd expected.  But, when the delay time pot gets more than about half way through its travel, the mod basically disappears.  Is that normal?
3. Clock noise - creeps in when the mod depth pot and the delay time pot are set to give a very long delay.  To be expected?
4. Chorus sound - I don't seem to be able to get a decent chorus sound out of it.  Watched a couple of other youtubes of echo bases, and these other builds seemed able to get a better chorus than I can get.

Here's the vid that should explain things a little further (excuse the crappy playing and the Kiwi accent...)

http://www.youtube.com/watch?v=Kbqyhn1ZXuE

Cheers
Aidan

[Taylor]

I can't watch your video right now, so I don't know the severity of your issues, but that all sounds pretty much like the way mine works.

[ACS]

Thanks Taylor, useful feedback.

Here's an interesting observation that I've just discovered - the 'LFO ticking' (if that's what it is) does not go away when bypassed, IF the boss/tails switch is in the 'tails' position.  If it's in the 'boss' position, then the noise disappears completely...  This implies to me that maybe it's the switching part that's incorrect, and it's not really LFO ticking I'm hearing?

Thoughts?

[edit - a quick search shows that LFO ticking would most likely change speed with the speed pot.  This is not the case - no matter the settings, the noise never varies, except with a) the position of the boss/tails switch in bypass, and b) the wet volume pot.]

[slacker]

Watching the video all sound like it should.
I'd say the effect the depth pot is having on the delay time is about normal, might be a bit worse than mine but it's hard to say. I'm looking at seeing if this problem can be resolved, it doesn't really bother me but a few other people have mentioned it. Someone suggested decoupling the LFO from the PNP transistor using a big cap, I've tried this and it works, but I didn't like the effect it had on the modulation sound. It might just be a case of tweaking a few more components to improve it though.

I hadn't noticed the mod disappearing before you mentioned it but having just had a play with mine it does seem to. Mine only does it with the mod depth at maximum then at about 2/3 of the delay time pot's rotation the mod effect stops. On mine turning the mod depth down a touch brings the effect back, so if yours does the same then you can just increase the value of the 240k resistor before the depth pot a bit and that should solve it.
A bit of clock noise at maximum delay time is normal, it's no worse than any of the other PT2399 delays. Adding modulation makes it worse, because you're slowing the chip's clock down even more.

To get the chorus effect set the delay time at minimum or close to it, mine sounds better with it just a hair away from minimum. Turn the level up all the way and the repeats up to about a third. Then adjust the mod speed and depth to taste. One problem can be that the pedal is not getting to a small enough delay time, if you turn the mod depth all the way down, with the delay time on minimum you shouldn't really be able to hear a delay. If you can still hear a short slapback delay then something is is adding too much resistance between pin 6 of the PT2399 and ground. This could be an error or an incorrect component or it's possible the PNP transistor isn't turning on enough and it's resistance is too high, trying another transistor might fix it, if that's what it is.

To check if the noise you're hearing is from the LFO or not just short out the 1uf cap in the LFO, that will stop the LFO, so if the noise is from there it will stop. As you can only hear it in tails mode though it sounds like it's noise from the PT2399 not the LFO.

Hope this helps

[ACS]

Thanks Ian, appreciate the response.  Good to know I'm on the right track.  Definitely keen to pursue the decoupling idea, as the changing delay time really bugs me!!  What did you put in there as a first pass, and what was the effect on the mod itself?

[zyxwyvu]

What did you put in there as a first pass, and what was the effect on the mod itself?

I built my echo base with a 10uF (I think.. anything that size or bigger should work) capacitor. The modulation sounds fine to me, and the depth setting doesn't affect the delay time.

[ACS]

OK, thanks Josh - where does this go then?  Between pin 4 or 6 of the PT and the trannie?  Or after the mod depth pot? or somewhere else?!

[zyxwyvu]

OK, thanks Josh - where does this go then?  Between pin 4 or 6 of the PT and the trannie?  Or after the mod depth pot? or somewhere else?!

I put mine between the 240k resistor and the depth pot (just cut the connection between them, and insert the cap). You can also put it before the 240k resistor (connected to U1A). The positive side goes towards the LFO, the negative towards the transistor.

[ACS]

Awesome, I'll give that a crack tonight

[slacker]

I put mine between the 240k resistor and the depth pot (just cut the connection between them, and insert the cap). You can also put it before the 240k resistor (connected to U1A). The positive side goes towards the LFO, the negative towards the transistor.

Thanks for that info. I'd tried it with the cap between the pot and the transistor, and it really messed up the modulation waveform, made it sound all "rubbery" not smooth like I wanted it. I'll try your method and see what happens.

[ACS]

Josh, you're a legend!  This one mod has, for me, turned this effect from a pretty cool but somewhat quirky effect, into a VERY useable box.

Ian, awesome design on this - and this is the icing on the cake   I definitely suggest you try this one...

Cheers!

Aidan

[slacker]

I just tried putting a 10uF cap where Josh suggested and it works great, really nice modulation sounds with little or no change to the delay time when turning the depth pot.
Between this and the "no tick" cap I think that's pretty much addressed all the main complaints about the design. I'll update the schematic with this mod, and see if I can fit it into the vero layout somehow.