Echo Base - a new PT2399 delay

[mikemaddux]

OK so I plugged the old TL072 that I had pulled out when slacker told me they were backwards.

I imagined that since the TL072 was getting hot it must be in the wrong way.  I flipped it around and started to mess witht the wires on the 100K delay volume pot.  I noticed when I applied pressure to the pot it would work.

I replaced that pot and now have a semi working echobase.

the repeats seem pretty distorted so im sure there is more to this debugging, but at least all the knobs, switches, and LED work.

Thanks again guys.  Anyone know about the distorted repeats?

[D.O.O.H.H.]

Hi!Distorted repeats?Ok.Replace two res.47k(pin14 and pin15 of PT2399) to 22k or 24k,decrease feedback pot to 47k and replace res.20k(out of feedback) to a trimpot 47k.And sorry,friends,for my very-very bad English,I'm from Ukraine(offtopic).Good luck! 

[Auke Haarsma]

it depends on the cause of the distortion. If you have a fully functional echobase but get distorted repeats with signals (like humbuckers) but clean with not-so-hot-signals (like single coils), I'd suggest to drop the feedback-limiting diodes.

[burdt]

i just finished building one using the anon-faceless-coward layout.  i've managed to get it to work, had some problems with noise early on and some overlooked jumpers.  my only problem now is a very hot signal.  what would be the easiest way to tame the echo base's output? 

[Auke Haarsma]

I think my self-quote below could help you out. With too hot a singal out of the EchoBase, I assume you mean the volume of the delayd signal?

(...)
Feedback pot causes too loud feedback too soon / oscilliation
There is  a resistor to tweak here. Focus on the 20k resistor running from the middle lug of the feedbackpot. Raise this value to tame the feedback pot. I swapped in a pot and dialed my 'perfect' value. Turned out to be 135k. No resistor with that value in my stash ofcourse. 120k would still cause oscilliation before reaching the end of the feedbackpot, so I put in 150k. Does the trick. I'd would probably be a good idea to replace the 20k resistor with a trimpot (say 150k or 250k).

[burdt]

Auke, i did read about feedback resistor tweak but the loudness problems i'm having are related to the total output.  even with bypass on i get a very hot signal, way hotter than unity.  the pedal works, i just have to turn my amp way down.  if i attempt "normal" amp settings i get ridiculous volume and amplified noise, whether it be with our without delay.

any ideas?  i'll post my voltage readings shortly. 

[slacker]

That's very strange, the bypass signal is just a couple of buffers so it should be the same volume as your guitar straight into the amp.
I would check the value of all the resistors around the input and the op amp that makes up the buffers, especially the 2M2 and 10k resistors, if some of those were incorrect values or if they were switched around that could cause it to be louder than it should be.

[burdt]

thanks slacker, i'll check when i get home.  i'm pretty certain i used all the right values but i might have read a resistor code incorrectly.  last time i put a 75k into what was supposed to be a 15k because i mistook purple for brown.  some of those colors are hard to read.  on top of that, my etch was pretty dismal.  some of my traces are razor thin.  i got impatient and rather than etching a second board i got to work right away.  while all the traces pass continuity tests, the board is a total mess.  next build should be prettier. 

on another side note, i'm using a recycled box i purchased in a lot with a bunch of other guys from the board.  i'm thinking of adding a 6th pot for wave shape control, since the box would lend itself for that very nicely.  earlier on the thread there was a post regarding the wave shape pot's location, and i believe it was posted via schematic.  while i'm sure i can figure out where to drill the holes for the pot's leads from that schematic fragment, i would like a second opinion.  i used the layout that was originally on the japanese page. 

i appreciate the help. 

[burdt]

That's very strange, the bypass signal is just a couple of buffers so it should be the same volume as your guitar straight into the amp.
I would check the value of all the resistors around the input and the op amp that makes up the buffers, especially the 2M2 and 10k resistors, if some of those were incorrect values or if they were switched around that could cause it to be louder than it should be.

the two 10k resistors under the buffer were actually 30k.  this is why one shouldn't solder for 6 hours straight.  after taking those off and replacing them with 10k the volume dropped considerably.  its still a bit loud but its not ridiculous like it was before.

regarding this:

on another side note, i'm using a recycled box i purchased in a lot with a bunch of other guys from the board.  i'm thinking of adding a 6th pot for wave shape control, since the box would lend itself for that very nicely.  earlier on the thread there was a post regarding the wave shape pot's location, and i believe it was posted via schematic.  while i'm sure i can figure out where to drill the holes for the pot's leads from that schematic fragment, i would like a second opinion.  i used the layout that was originally on the japanese page. 

y'all can forget about that.  i'm quitting while i'm ahead.  i want to play so i boxed it into the recycled box and left a bunch of open holes.  it is a prototype after all.  i'll call them speed holes, like homer simpson...

[fegg]

hi, just starting the debug of my vero build, so a couple of points I could use help with...
I had c24 (47u) connected 1 row lower than on the vero layout (pin 6 instead of 5 on U1 ), I sorted this..hopefully it didn't damage anything!!
also I'm using a bc558b for q3 <-- is this OK?
and bc548b for q1 (sure this is ok)
also I have a 100k trim for r17 for the feedback (i also added a 47k after this to the wiper).

basically I'm getting mega oscillation, or with level zeroed it get clean guitar,
I get "some" response from all the pots with exception of mod speed pot.
I will check the voltages this afternoon if I have the time 

geoff.

EDIT: I had a L7805 in and the pinout is different    will I have fried my chips!!

[slacker]

hi, just starting the debug of my vero build, so a couple of points I could use help with...
I had c24 (47u) connected 1 row lower than on the vero layout (pin 6 instead of 5 on U1 ), I sorted this..hopefully it didn't damage anything!!

That won't of damaged anything.

also I'm using a bc558b for q3 <-- is this OK?
and bc548b for q1 (sure this is ok)
also I have a 100k trim for r17 for the feedback (i also added a 47k after this to the wiper).

Those changes should all be fine.

EDIT: I had a L7805 in and the pinout is different    will I have fried my chips!!

If you were unlucky you might of fried the PT2399, everything else should be Ok. What I always do is power the circuit up for the first time with none of the chips in and then measure the voltages on the power pins of the sockets to make sure I'm getting 9 volts, 5 volts and ground in the correct places, that way you'll hopefully spot any errors and you don't risk frying the chips.

[kierc]

Finished mine yesterday! 

When adding the 2.2uF to stop the LFO bleed, does the polarity matter? which way should I connect it?

Thanks!

[slacker]

The positive end of the cap goes to pin 7 of the opamp the negative end goes to ground.

[fhsueh]

I've been enjoying my Echo Base for the past month and it occurred to me that an external button-type switch to dial the feedback pot up/down would be really useful.  I personally am not very adept at using a wah (something about the balancing act ). But if I could step on a button switch and hold it down to dial up the feedback as I'm playing, I'm thinking it could create some really expressive sounds on-the-fly.  Releasing the button would return the feedback level to the setting on the pedal itself. Of course, this would be cool for any of the pots.  Does anyone know how this might be done?  Thanks in advance!

[slacker]

Have a look at RG's LERA design http://www.geofex.com/Article_Folders/lera/lera.htm. That could probably be made to do what you want, you'd just have to figure out the best place to put the LDR, from the top of the feedback pot to after the "feedback" resistor would probably work.
You could also add this to the delay time or mod speed pots.

[fhsueh]

Thanks Ian! I took a look at the LERA, and clearly R.G.'s other article "Add an Expression Pedal to Any Effect" lays out the easier method - I just have to be willing to use a rocker assembly I guess.

[ShortScaleMike]

Just built this today from a Veroboard layout I found, it had a few minor errors which might have been fixed since but I noticed them as I was building so all was well. I was very pleasantly surprised that it fired up and worked first time! Sounds great and I'm really happy with it, will be boxing this one up for sure.



Thanks very much to the original designer and the person who made the layout, great pedal!

[slacker]

Cool, glad you like it.
That looks like my "true bypass" layout from here. If it is if you let me know what errors you found I'll correct it, I did it very quickly because someone asked for it, I didn't bother checking or building it.

Actually just looking at it now I can see one straight away, the top left opamp has no ground connection

Welcome to the forum

[ShortScaleMike]

Cool, glad you like it.
That looks like my "true bypass" layout from here. If it is if you let me know what errors you found I'll correct it, I did it very quickly because someone asked for it, I didn't bother checking or building it.

Actually just looking at it now I can see one straight away, the top left opamp has no ground connection

Welcome to the forum

Cheers! That was the only major one, the other two were just missing part number labels, I believe on the main 9V filter cap (C26) and also the coupling cap to the Feedback CW lug (C16), however that aside it was all completely fine, you have no idea how big the smile was on my face when I fired it up and it worked first time. I've built a fair few pedals before, but only in the Boost/Drive/Distortion or Tremolo realm, Delay is completely magical to me and when I came across this layout I couldn't resist and did the parts order. Now it's working I can't wait to get it boxed up and on my board, I think my Deluxe Memory Man is going under the bed in it's box to accumulate value instead!

[slacker]

Thanks for that, I'll correct the layout.