Echo Base - a new PT2399 delay

[slacker]

Yeah the stripboard fits in a 1590B.

[mr_deadmaxxx]

@slacker

what will be the disadvantage if i rewired it in a way that the circuit will turn off when bypassed?

anyways, if you have a distortion pedal, a delay pedal and a noise gate, which pedal would you prefer to come first if you connect these in series?how would you arrange the 3 pedals in a way that you would still get a nice guitar sound output?

[slacker]

The disadvantage will be that no sound will come out
The bypass just switches the delay on and off, the dry signal passes through the effect all the time. Even on pedals where this doesn't happen turning the power off in bypass is normally a bad idea, because you get pops or other strange noises when you turn the power back on.

Delays normally go after distortion pedals, noise gate either before or after the distortion depending on which sounds best to you.

[mr_deadmaxxx]

will it (noise gate) not affect the delay if you place the noise gate after the delay?

[mr_deadmaxxx]

@slacker

i want to ask you something about true bypass..
i have sent you a PM.

[mr_deadmaxxx]

is it ok if you make this into a true bypass?
will you still have the tails effect?

because i think if you make it a true bypass, then the output signal will be instantly cut off when bypassed and the delay signal will not die out naturally..

[Taylor]

is it ok if you make this into a true bypass?
will you still have the tails effect?

because i think if you make it a true bypass, then the output signal will be instantly cut off when bypassed and the delay signal will not die out naturally..

You can't make this true bypass and still keep the tails effect, for the reason you state. The whole purpose of the electronic switching in this is to allow the tails.

Now technically you could make this true bypass while maintaining tails, if you programmed a microcontroller to control 2 relays: one for input and one for output. You switch the input directly when the pedal is bypassed. Then the microcontroller waits a few seconds and switches the output. This isn't something you could just mod into the circuit, though, it would be a complete redesign.

[Valoosj]

Can't you just wire it like this, and connect the board out with the output?

[slacker]

Nice idea Yorick, but I'm afraid it won't work. The output of the pedal is a low impedance, and you'd be connecting it to the signal path so it would completely load down your signal so you'd get no sound or hardly any.
Taylor's relay idea either with a micro controller or some old school logic to generate the delay in the switching is the only way to keep the tails and make it true bypass.

[Valoosj]

How about my idea and putting a simple blender in between? Would that solve the issue?

[slacker]

Yeah a simple active blender would work, but that wouldn't be true bypass and, unless I'm missing something, the end result would just be the same as what the pedal already does.

[Valoosj]

Hah yes, off course, stupid of me 

I guess true bypass and the echo base will never be a good marriage if you want some tails.

[El Heisenberg]

Ya really need true bypass tho? Its just one pedal.

[Taylor]

A simpler (electronically) way to do it is just to have the normal EB bypass switch, and a second true bypass switch if you're really into TB. Hit the normal bypass, let your tails die off, then hit true bypass to maintain yer tonez.

[El Heisenberg]

Or you could quit worrying about differences only a dog can hear 

[Valoosj]

It doesn't matter all that much to me, just wondering about the possibilities.

[cctsim]

I built the stripboard version of Echo Base today and and currently testing the circuit outside the enclosure.  I have some questions related to
the LFO section. From the measurements I did the LFO seems to work from ~0.55Hz to 20.79Hz, however,  the output amplitude is not constant
across the frequency range. It varies from 100mVpp to 360mVpp, respectively.  Also, for the lower frequencies the waveform is not triangular any more.

Is this normal or should I look for errors in my implementation ?

[slacker]

I noticed on your picture there's a box that says AC, I guess that means you're measuring AC, which would explain your results. You need to be measuring DC.
If you measure straight from the opamp you should get about 3 volts peak to peak across the whole speed range.
The range of speeds is correct.

[cctsim]

I see, for the very low frequency setting the oscillation appears as dc and it is blocked because of the setting.

I'll check it again with the dc option enabled, many thanks.


Another thing I noticed was related to the SPEED pot. It seems that the range ~1.5Hz - 20.79Hz is covered between 0 and 500k and
the remaining 500k rotation only covers ~1 Hz. I was wondering if there is a better way to utilize the SPEED range maybe by using a reverse log pot (?).

[slacker]

Yeah that's right, the AC setting probably has a capacitor to block DC, like the input capacitor in most pedals. This along with the input impedance of the scope will make a high pass filter so only frequencies above a certain speed will pass through.

A reverse log pot might work better and spread the speeds out more evenly, other similar designs use them. I just used linear because it worked well enough for me and I know some people find it hard to get reverse log pots.