Echo Base - a new PT2399 delay

[mattthegamer463]

Fuzz Aldryn, do you have any pics of the inside of your pedal?  Also, which echo base layout did you use to get it into a 1590B enclosure?  I would love to know.

[YouAre]

Fuzz Aldryn, do you have any pics of the inside of your pedal?  Also, which echo base layout did you use to get it into a 1590B enclosure?  I would love to know.

That doesn't really look like a 1590B to me. I think it's the slightly bigger 125c. Taylor said his board should fit in there.

[Fuzz Aldryn]

Fuzz Aldryn, do you have any pics of the inside of your pedal?  Also, which echo base layout did you use to get it into a 1590B enclosure?  I would love to know.

That doesn't really look like a 1590B to me. I think it's the slightly bigger 125c. Taylor said his board should fit in there.

No Sir, it is an Eddystone 27l34P which is the same size as a Hammond 1590B. Layout I used must be somewhere here on the forum  - if I remind exactly it's the same that John Lyons sells.

[BoxOfSnoo]

Glad you got it working. Some people have mentioned that it sounds a bit distorted especially with hot pickups, I've never noticed on mine.
The first thing to do would be to remove the 2 diodes connected to the feedback pot and see if that stops it.

Ok I pulled out the diodes and it doesn't seem to make any difference.  Here is a very small clip of what I am hearing (the level pot is about 50%)

Is this correct?

[BoxOfSnoo]

Can any of you compare your working Echo Base to my (very small) MP3 demo above?  Does it distort as much on the repeats?

Thanks in advance.

[slacker]

That doesn't sound right to me, I take it the loud sound is what you played and the quiet distorted sound is he delay?
I would double check all the resistor values around pins 12 - 16 of the PT2399 to make sure they are correct, also if you've got one try another PT2399, perhaps whatever killed your regulator damaged the chip as well.

[BoxOfSnoo]

That doesn't sound right to me, I take it the loud sound is what you played and the quiet distorted sound is he delay?
I would double check all the resistor values around pins 12 - 16 of the PT2399 to make sure they are correct, also if you've got one try another PT2399, perhaps whatever killed your regulator damaged the chip as well.

Ugh.  Resistors all test at their proper values.  The only thing that doesn't seem right on the voltages of the PT2399 is pin 5 which reads 2.79v instead of 2.89v.  Everything else is much closer to the voltages you posted before.

Too bad, I have to collect more stuff for another order including the chip.  Oh well, it still sounds cool, it just limits the versatility somewhat.

[thehoj]

Just trying to debug a few small issues with the echobase I just assembled (Taylor's PCB). It works quite well except for a few issues when the pots are set at certain levels..
If I turn the LFO depth pot right down it for some reason starts to hiss quite badly, but as soon as I turn that up past a 1/4 of the way it completely dissapears.
Also, if I have the Level pot past about 3/4 of the way up I can hear a clock tick, even though Taylor's pcb includes that 2.2uf cap from pin 7 of U1B to ground.

Has anyone come across the loud hissing only when the LFO depth pot is turned down? Any suggestions on what could be causing that?
And is there anything I could do to get rid of that ticking when the level pot is turned up?

I've read through this thread quite extensively, but haven't come across anything about the hissing from the LFO depth pot. Also haven't really seen any discussion of ticking when the 2.2uf cap has been in place.

Thanks for any help on the matter.

[thehoj]

I think I've got the things in my previous post basically sorted out.. My next question is about distortion in the repeats.. I know that removing the clipping diodes and decreasing the gain on the op-amps lowers the distortion on the repeats, I've done that and noticed a decent change, it stays fairly clean with a clean signal going into it.
The only thing I'm noticing now is that if I run the delay after some hefty OD pedals or turn the gain up in my preamp (I'm running the delay pedal in the effects loop) the repeats become heavily distorted to the point that they almost seem to overload the pedal (sort of really heavy distortion and crackling almost).

Do I need to run this pedal before any OD? I thought that generally it's good practice to have the delay as late in the chain of effects as possible.

Any thoughts?

[BoxOfSnoo]

I think I've got the things in my previous post basically sorted out.. My next question is about distortion in the repeats.. I know that removing the clipping diodes and decreasing the gain on the op-amps lowers the distortion on the repeats, I've done that and noticed a decent change, it stays fairly clean with a clean signal going into it.
The only thing I'm noticing now is that if I run the delay after some hefty OD pedals or turn the gain up in my preamp (I'm running the delay pedal in the effects loop) the repeats become heavily distorted to the point that they almost seem to overload the pedal (sort of really heavy distortion and crackling almost).

Do I need to run this pedal before any OD? I thought that generally it's good practice to have the delay as late in the chain of effects as possible.

I have mine at the end, with almost all true bypass pedals in front, no gain pedals on and it still overdrives, as you may have heard above.

What do you mean about decreasing the gain of the opamp?  How did you do that?  I have a load of 4558 chips, but I figured those won't be as clean as the TL072s... or is that relevant in this circuit?

[Taylor]

You can decrease gain by lowering the value of the resistor connecting the inverting (-) input and the output of the opamp. However, in my PCB, which thehoj is using I think, the input opamp does not have a resistor at all, so the gain can't be lowered there, it's already unity. You would only be lowering the output gain, and I don't see how that could be effecting the repeats at all, unless the distortion is coming from the opamp.

[thehoj]

You can decrease gain by lowering the value of the resistor connecting the inverting (-) input and the output of the opamp. However, in my PCB, which thehoj is using I think, the input opamp does not have a resistor at all, so the gain can't be lowered there, it's already unity. You would only be lowering the output gain, and I don't see how that could be effecting the repeats at all, unless the distortion is coming from the opamp.

What I meant was just halving the 47K resistors (putting second 47K resistors in parallel with them). That did decrease the volume of the repeats by quite a bit though, so I've reversed that. The distortion of the repeats isn't bad at all with those 1n4148 diodes out of the circuit now. I just have to have the delay pedal basically right at the start of my effects chain, which I had thought would sound pretty bad, but I actually like, the repeats don't distort really, and it's sounds pretty natural even with the effects affecting the delayed signal. I guess this is just the way I need to use the pedal?

I do have a surprising amount of hiss when the pedal is in the loop though (even while disengaged), it's not too bad but definitely noticeable compared to not having the pedal in the loop at all.. So I'm thinking I may just use 3dpt switch to bypass the circuit completely when the pedal is disengaged.

[slacker]

As a few people have mentioned distortion problems recently I decided to take some measurements off mine to see if I can pinpoint what the problem might be. I fed the input with a 1Khz sine wave and adjusted the volume until I got visible distortion of the wave on my scope. The test was done with all the controls turned down, so it doesn't take into account the intentional clipping caused by the diodes.

I measured at the output first, to see when the input and output buffers would clip, and the signal was clean up until about 5 volts peak to peak, after this it clipped harshly. To me this says the buffers have plenty of headroom, so if you're getting distortion when the pedal is bypassed there's either something wrong with it or you just need to turn down whatever is in front of it.
Like most stompboxes it's not designed to go in effects loops though, so depending on the level of your loop I suppose the signal could be too hot for it.
Using a different opamp in place of the TL072 might give it more headroom but as 5 volts is the same as the PT2399's supply voltage it is  going to clip at that point anyway.

Next I measured the signal at pin 14 of the PT2399, this is the output of the chip. The signal stayed clean with an input of up to about 400mV then it clipped. So I guess this confirms what people have said that hot pickups or a loud boost, overdrive, fuzz or whatever will cause distortion. I guess I must just have wimpy pickups and not run my pedals very loud because I've never heard any distortion from mine.

I'd try the suggestion from thehoj  and others and reduce the value of the 47k resistors, maybe change them to 22k - 30k. To stop this reducing the level of the delay you need to also decrease the 10k resistor after the level pot by a similar proportion.

[jmwreck]

I am having a problem with my build, i've made it sound but as i turned the feedback  higher, it starts to destroy the sound with just feedback motor machine sound, and as i turned the speed lower while my feedback is at zero position, the motor sound turns on again.  I know this is quite done, but my question, is there any possibilities that my PT2399 chip was damaged? coz i can hear the delay sound at feedback - 0 , and speed - max.  therefore, its good, besides the tweaking of those pots, it became horrible.. what could possibly be the problem?? 

[jmwreck]

  im trying to resolve this..

[BoxOfSnoo]

I'd try the suggestion from thehoj  and others and reduce the value of the 47k resistors, maybe change them to 22k - 30k. To stop this reducing the level of the delay you need to also decrease the 10k resistor after the level pot by a similar proportion.

I reduced these to 22k, and the 10k down to 3.3k and it's MUCH MUCH better!  The repeats are much cleaner... I even put the diodes back in, just to keep the character of the delay.  I may need to drop the 3.3k even more, as at the moment I have to turn the level pot up higher than I'd like. 

There's also a motorboating sound (if I understand motorboating correctly) now when the level pot is maxed.  I'll have to reread the thread to see if it's been mentioned, but for now, I just won't turn it up that high.

[BoxOfSnoo]

Ok sound clips, now that it's running well!

East Wes (half without, half with EB engaged)
Cold Shot Vibe

Godin Freeway Classic into my Vox AD30VT (Boutique CL mode)

Needless to say, I'm happy!

[elshiftos]

I threw together a rebote 2.5 but lost interest in it because of the amount of noise that was present when the delay pot was over 1/3 up. I've just replaced the ceramic caps I originally put in with film, it has made some difference to the noise level but not enough for my liking.

The general opinion on here is that the echobase is cleaner than the rebote, yet it effectively has less filtering going on. Is this possible?

Ta

[Marcvv]

Cool, I'll have a look at the original PCB and see if I can show how to add the mods. I presume the PCB John's using is the anonymousfacelesscoward one?
Looks like with a bit of trace cutting and a couple of extra jumpers the new buffers can be added to the PCB.

Hi Ian,

Did you ever find out how to mod the original board to add the new buffer?

Thanks, Marc

[slacker]

I had a look at and it looked doable, I didn't get round to actually trying it though. I'll have a look over the weekend.