Echo Base - a new PT2399 delay

[ppatchmods]

I sent a partially working board to a forum member to debug/rebuild and got a completely different board back that has no sound whatsoever...and he charged me tons of cash. But enough about that. I posted a question earlier with no reply so here it is again:
"not sure if this has been covered, but i want to add an expression pedal jack to 2 of the pots. I want to use the same jack and switch between them via toggle. what type of toggle would i use? maybe a dpdt or 3pdt? i was thinking the speed pot and either the delay time or mix pot."
Thanks guys...& yes. I quoted myself! 

[slacker]

I don't think you can very easily use 1 jack and switch it between controlling 2 pots. There's too many connections that would need switching, plus the fact that the delay time and the mod speed use completely different pot values. I guess if you really wanted to do it some sort of multipole rotary switch might do the job, but it would be a lot of effort.

[slacker]

Actually there might be a way to do it, let me think about it.

[mth5044]

Hey slacker (or anyone for that matter), did you try out PTAP on the echo base yet? I can't wait to see some end results.

[slacker]

Not yet, haven't had time. I'm definitely going to order one though.

[mth5044]

I got kinda bored and made up a tap tempo PCB off of the two IC's and schematic from the PTAP. Not sure if they are right, but oh well, maybe someone can see some fix. I don't know if there is a layout/PCB for it yet, but here is another one anyway. About 1"x 1.2", so pretty small. Could be smaller I guess. I put on the 5v reg because the notes say it should have its own, or it could introduce noise.





http://thoughtprocessinc.com/files/PTAP%20Controller%20Manual.pdf

Like i said, could be smaller, but it's such a small circuit anyway, why not have a little solder room 

It also has this note:

"NOTE: Both the timing calculations and current-limiting considerations are based on this series resistor
being 1k, which is the standard value for most PT2399 kits. Other values will results in incorrect timing,
and values lower than 1k will cause the digital pot to exceed its maximum pin current."

Is it 1k in the echo base?

[slacker]

Is it 1k in the echo base?

The Echo Base doesn't have that resistor. The minimum delay time is set by the resistance of the PNP transistor and is less than 1k. To use the PTAP you'll need to add the 1k resistor. Like I mentioned in the PTAP thread this might affect the ability to get the chorusy sounds.

[svstee]

Built th Echo Base (Thanks Ian!) and after realizing I had switched my in/out wires, I got it (mostly) working. Delay, level and feedback work great, but I don't have any modulation.

I checked voltages and I am finding some things that confuse me.

PT2399
All normal, except:
7 and 8 are 3.3v instead of 0.5


4066
1 and 2 are 2.8 should be 4.6
3 and 4 are 0.0 should be 0.4
5 is 0.0, normal
6 is really weird. It should be 0.45 on 4.5 on, but I get .08 off, and when it is on and I touch it with the meter lead, the effect turns off.
7 is 0.0, normal
8 is 2.26 should be 9.0
9 is 1.92 on and 0.0 off should be 3.0 on and 0.32 off
10 and 11 are 2.89 should be 4.6
12 is 8.5 on, normal
13 is 7.5 should be 8.5
14 is 9.0, normal

TL082, top left of vero, U3
all normal except:
6 is 3.37, should be 5.0

TL072, bottom left of vero, U1
all normal except:
2 is 3.62 should be 5.0
5 stays at 4.12, should change.

Voltage regulator and all transistors work the way they should. Any thoughts?

[decc]

I got kinda bored and made up a tap tempo PCB off of the two IC's and schematic from the PTAP. Not sure if they are right, but oh well, maybe someone can see some fix. I don't know if there is a layout/PCB for it yet, but here is another one anyway. About 1"x 1.2", so pretty small. Could be smaller I guess. I put on the 5v reg because the notes say it should have its own, or it could introduce noise.

One note: the delay pot is just forming a voltage divider for the MCU to read, but it has to divide the 5V, not the pedal's main 9V. So I would put a 5V pad on there for pin 3 as well (and pin 1 is grounded, which I assume is one of the "GND'd stuff" connections).

Is it 1k in the echo base?

The Echo Base doesn't have that resistor. The minimum delay time is set by the resistance of the PNP transistor and is less than 1k. To use the PTAP you'll need to add the 1k resistor. Like I mentioned in the PTAP thread this might affect the ability to get the chorusy sounds.

If I understand the explanation of modulation section correctly the PNP transistor and the 39k resistor in parallel form a small voltage controlled resistance, and it is at its minimum R when modulation is off. So with the modulation pot dialed to 0 we can measure the delay pot and the voltage on the collector, and derive the equivalent resistance. From there we know what value needs to go in series to total 1k.

This still doesn't help with the chorus sounds as I think they are supposed to be around 30ms and a 1k min resistance is equivalent to about 50ms. I really should just sit down and build the modulation section and test this myself.

[svstee]

Can someone help me out?

The bypass and boss/tails work perfectly.

Just double checked  the whole back of the board with a 7x loupe. No solder bridges, incomplete trace cuts or anything.

Speed and modulation knobs are effecting voltage change on the PNP's base.
I replaced the transistor, no luck. Then, just for giggles, I turned it around in case my transistor had a weird pinout. It worked exactly as before.  What is going on? Voltages above.

[slacker]

This is very strange. What voltages do you get on pin 1 of the LFO opamp and what voltages do you get on the base of the transistor with the mod depth pot on maximum?
If you turn the delay time pot to minimum what sort of length delay do you get?

[Taylor]

It's very tough to help people troubelshoot their boards without being able to see them, but I'll share my number one debug tip with you:

Go through and reheat every single solder joint. I have debugged many things this way, including some huge PCBs, and this has solved way more problems for me than my meter has. Just reheat and let the solder flow. This fixes some invisible problems with joints, where the solder has domed over the component leg without making good contact.

[carrejans]

Isn't there any webpage about this pedal, with all the usefull info bundled?
Or do I have to go through 30+ pages? 

[Lurco]

Isn't there any webpage about this pedal, with all the usefull info bundled?
Or do I have to go through 30+ pages? 

This IS the webpage! 

[slacker]

Yeah this is it 

I keep meaning to do a pdf or something with all the useful info in, I just haven't had time yet.

[Barcode80]

Isn't there any webpage about this pedal, with all the usefull info bundled?
Or do I have to go through 30+ pages? 

this is just a tad ungrateful, please be respectful. this is a community, not a service. please don't complain about how such a great project is developed and shared, just enjoy the project!

[theehman]

Isn't there any webpage about this pedal, with all the usefull info bundled?
Or do I have to go through 30+ pages? 

this is just a tad ungrateful, please be respectful. this is a community, not a service. please don't complain about how such a great project is developed and shared, just enjoy the project!

I wouldn't call it ungrateful.  While I salute and respect the work others have put into this, it IS a bit tiring to go through so many pages for the information.  It would be great if the first post on any build thread was left for constantly updated information.  It could include the schematic/PCB layout (updated as it changes), parts list, troubleshooting tips w/ thread links, etc.  I think it would cut down tremendously on the constant posts for help with problems that were covered 2 or more pages ago.

[slacker]

If you just want to build it stock all the info you need apart from the PCB layout is in the first 4 pages. Point taken though, it would be nice to be able to add things to the original post to keep it up to date.

[Barcode80]

I will say it might be helpful if we established a "projects" section like certain other forums so all the specific information on a pedal can be consolidated in one place. Though it would require more moderation which I'm not sure Aron really has the time for

[Vitrolin]

hej since i cant find a CD4016 or CD4066, i was wondering if its possible to make the Echo Base with something like the buff n blender, and still keep the echo tails feature?



or maybe some other way that doesn't requiere that exotic componentes