Echo Base - a new PT2399 delay

[slacker]

However its nice project. I love this effect   

Thanks. Yes that is a known problem with the mod depth pot, it does the same thing when modulation is on but it's probably harder to tell. You can fix this by adding a 10uF Electrolytic cap between the 240k resistor and lug 3 of the mod depth pot. The positive end of the cap goes towards the resistor. There might still be a bit of an effect turning the pot but it's a lot less.

[bluescage]

I got me a usb oscilloscope and discovered that when this distorted sound came, the output opamp was oscillating at approx. 533KHz.

Interesting information, I don't think I heard of that problem before, thanks for sharing. With the TL072 you might be able to stop it oscillating by putting a 100 Ohm or similar sized resistor in series with the output. That might stop it by isolating the output of the opamp from the cable capacitance.

Thanks Ian, I will try this and report back.
Thank you for your projects and your effort to answer all questions!

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[bluescage]

Yes.

The 100 ohms did the trick, The TL072 is tamed!
Thank you Ian for the tip!

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[Mario44]

However its nice project. I love this effect   

Thanks. Yes that is a known problem with the mod depth pot, it does the same thing when modulation is on but it's probably harder to tell. You can fix this by adding a 10uF Electrolytic cap between the 240k resistor and lug 3 of the mod depth pot. The positive end of the cap goes towards the resistor. There might still be a bit of an effect turning the pot but it's a lot less.

Well, You couldn't see on these photos, but I had that 10u mounted on the reverse side of my fancy "panel" 
but instead of fixing, it made only dry signal going through the circuit, so no modulation and no delay. It was like You said, positive to 240k and negative to pot lug.
However, it's good for me.

[blackieNYC]

Echo base builders: at very slow LFO speeds, is the modulation smooth? I'm working on a similar (and verified, I guess ) build, and the LFO is very square at the low speeds, where a triangle or sine would sound so much smoother. Thanks

[slacker]

The LFO output is triangular at all speeds, and the modulatation is smooth.
In what you're building is the problem with the LFO output or with what it controls?

[blackieNYC]

Just looking at the LFO by itself.  Goes down to .3Hz, but it is .6vp-p. up at 4Hz and above it is 1.6vp-p. starts to triangle there. The Magnus Modulus LFO, and the Jenny Greenteeth LFO. https://dl.dropboxusercontent.com/u/57831278/JennyGreenteethBuildDoc.pdf
Update: I am wrong.  The waveform at .3 hz is fine.  I had my scope on AC coupling, and low frequencies like that confuse the scope. DC coupling reveals a perfect amplitude and triangle. 

[slacker]

Yeah that's what I'd expect the waveform should be pretty consistant over the whole range. Your problem sounds like it is somewhere after the LFO. I'll take a look at your other post

[Ozsi]

Slacker/Ian, I've finished building an Echo Base over the past few days and just want to add my voice to the chorus of praise for this project, it really does sound amazing.  And all your contributions to this thread over the past seven(!) years answered pretty much every question I came up with whilst debugging it.

To be honest, the whole build probably took longer than needed, because every time I went to test the pedal I couldn't help but noodle around for another 30 minutes   In fact, when the board was first done, I had no output signal at all - even the clean part was being killed - and the modulation wasn't working.  But I found the delayed output from the PT2399 with the audio probe, and had 15 minutes of fun just playing with that (I do have a soft spot for delays, admittedly...)

Simon.

[Liz]

Hi guys!

I hope you can help me! I've recently built an echo base and everything is working fine except for feedback.
This is how it sounds when there is no input signal and i "turn" feedback on:

http://www.4shared.com/mp3/suaA2F_5ba/echobase_feedback.html

I've checked the schematic, layout, devices and wiring for about five times now. I just can't find a mistake.
Maybe someone has a suggestion for me...

[slacker]

Hi

That sounds like it is going straight into maximum feedback, I would start by double checking all the connections to the feedback pot especially the one that is supposed to go to ground, also check the value of the resistor connected to the wiper of the feedback pot, it should be 20k.

Which layout are you using?

[Liz]

The resistor and the connections are fine.

I'm using my own layout in which I already included dub madness and diode lift mod. So maybe I've made a mistake there.

http://www.4shared.com/photo/exEp9IKRba/Feedback_Mods.html

[slacker]

The schematic looks correct for the dub madness and diode lift mods. It's a bit of a strange problem, just to check when you have the feedback turned all the way down it works fine and you just hear one echo? Then as soon as you start to to turn it up you get all that noise?

[Liz]

Yes, exactly. When feedback is turned off there is one echo and when I turn it up just a little there is feedback. But as soon as I turn it up more there is that noise.

I changed the 100k to a 50k and I get a bit more of the feedback function but in the end it's the same.

[garcho]

maybe take some voltages and post them here? Welcome to the forum!

[slacker]

It could be a problem with the dub madness mod, make sure the switch is connected so that it's normally open Ie: there's no connection between lug 2 of the switch and lug 3 of the level pot. Maybe check that there's nothing shorting the switch out on the layout, a stray blob of solder or something.
The other thing that could cause it is too much gain somewhere in the PT2399, perhaps check all the resistor values around pins 13, 14, 15 and 16.

[bandmbill]

Echobase and Taptation

Please don't all shout at me for this!

I have had a normal Echobase for a while - totally brilliant pedal - I bought two PCBs and have a second that I want to tie to Taptation - I would like to keep the Echobase mod controls.

I have the Taptation documents - the circuit in the PT2399 Interface Application Note gives a connection to pin 6 on the PT2399 - I have tried sifting through the Echobase and the Taptation threads on this forum but still haven't got it sorted in my mind how to sort this - anyone got a diagram?

Bill

[slacker]

Unfortunately you can't really have tap tempo and have the Echo Base's modulation at the same time, the PNP transistor used to do the modulation adds a different amount of resistance than the taptation is programmed for so the tapped tempo will not be accurate.
If you want to try it anyway, remove the Echo Base delay time pot and figure out which of the pads connects to pin 6 of the pT2399 and which pad connects to the PNP transistor. Then going from the  taptation appnote connect pins 5 and 6 of the MCP41100 to the pad going to pin 6 of the PT2399, and connect pin 7 of the MCP441100 to the pad going to the PNP transistor.

You've really got two options either add a switch that disconnects the modulation for when you want to use the tap tempo accurately or use the modulation from the taptation instead of the Echo Base's. Or a combination of both EB modulation or taptation modulation.

[bandmbill]

Thanks - I will have a play!

[Seven64]

love this build.  i need to build another with ALL THE MODS.  i have one that i jumpered to never have tails, and the mod is always on so there is only a stomp and 5 knobs.   

anyhoo, bump to an awesome build!