This is my attempt at a stero ping-pong delay
(http://img329.imageshack.us/img329/6198/delaystbnv2btw7.th.png) (http://img329.imageshack.us/my.php?image=delaystbnv2btw7.png)
I started out with the echobase schematic, duplicating stages. the stereo ping pong is achieved feeding the output from delay stage A into delay stage B. The feedback goes from B output to A input.
this way, if both delays are set to "T" delay time, repeats go at time T:outA, 2T:outB, 3T:outA... and so on.
The spatial effect when using two amps is great, and the vibrato thing adds a nice chorus to the sound.
Some problems i had was that the signal got easily distorted, notably with humbuckers, so I changed some resistors. The red marked areas are those changes from the original echobase made to clean up the sound. i think i got a nice setup with this.
Green areas are some additions:
The LFO on/off: disconecting the main LFO output is not a satisfactory method, because there will be a fixed 39k at the delay time, so the switching must eliminate that resistor.
The tails switch: I made a variation to the original switching. Input must be muted whenever the pedal is OFF, regardless of tails mode, so that no delay tails are generated while OFF.
Switchable caps at pins 9-10: this asymetric configuration will filter the delays on a more dramatic high-pass style. Long feedbacks will fade into a more treble echo. This will also increase output level. It can be done on pins 11-12 to go into a deep low-pass feedback.
All four cmos switches are in use, and there is one left opamp if using dual chips, which could be used as another buffer for a second input.
There's a lot of possibilities on providing wet, dry or mixed outputs, working out some kind of jack switching.
i am waiting your comments and corrections about this, since i'm sure there may be a lot of improvements to be done
thanks!
Thanks for posting your idea!
You can bypass the LFO by taking the 1uF out of the circuit at the LFO. So, no need to disconnect that 39k resistor.
Maybe it is cool to add another feature:
There is a mod out here (coop from Slacker and Valoosj iirc) that doubles the delay-time by adding another PT2399 to the Echobase. It could/should be possible to add a switch to your schematic so you can choose: ping-pong delay or double delay time. This makes maximum use of the additional PT2399.
Nice work, I love the hand drawn schemo.
Quote from: Auke Haarsma on October 03, 2008, 03:50:27 AM
You can bypass the LFO by taking the 1uF out of the circuit at the LFO. So, no need to disconnect that 39k resistor.
There is a mod out here (coop from Slacker and Valoosj iirc) that doubles the delay-time by adding another PT2399 to the Echobase. It could/should be possible to add a switch to your schematic so you can choose: ping-pong delay or double delay time. This makes maximum use of the additional PT2399.
Nice tip on the 1uF, it resets the LFO and keeps the delay time setting static. Thanks!
there can be mono or stereo ping pong with a couple of switches ruled by the output jacks (using the stereo pin to ground as trigger). That way, for example: only connecting out A, you have amix of "ping and pong", both outputs is for the full stereo panning, and B only is for a long delay time using both chips. Can be made with more 4066 cells, or some kind of FET switching.
A dual pot on delay time will give symetric stereo delays, or two independent pot may give a more complex pattern, like "taa-ta-taa-ta-taaa" :icon_lol:
Quote from: slacker on October 03, 2008, 12:13:50 PM
Nice work, I love the hand drawn schemo.
there are still some typos there, and a couple of resistors missing
i still have a problem when bypassing the delay lines. I will try to breadboard a stock echobase to see how it behaves, for i may have misplaced something.
When closing the cmos switches for the output, i get a sudden increase in feedback level, so it goes over unity and feedback gets out of hand, all this while being "bypassed". So turning it on again turns up in a big and loud noise havoc.
It also happens when turning down the output pot at the delay out (prior to the mixer opamp). As the wiper turns lower, feedback level increases too. ???
I tested the original echobase with the following results:
- with the 47k resistors it produces some distortion when using humbuckers (anybody else? or is it just me?)
- The feedback level is stable when coling the output switch or reducing output level
When changing both 47k to 22k, the sound is much cleaner, which is a big improvement. The rebote schematic has 10k values there, but it suffers from a lot of background noise though.
The original echobase with the two 22k resistors has the same problem with the feedback level, so its easily reproducible. Feedback growth is proportional to the lowering of output level, and closing the output switch will make it grow even faster.
I guess it has to do to some relation between resistor values, including internal values on the chip.
Coincidentially, the PT80 delay also uses 22k there, so we could find some clues there.
i would really appreciate some help here, since the echobase is a great desing.
That's bit strange, I'll have a think about it and see if I can work out what is happening.
I don't know if it's just a mistake on your schematic but you've drawn it with the 1M5 biasing resistors for the 4066 connected to ground, they should go to 5 volts. I don't know if that would cause the problem you're having though.
Quote from: slacker on October 04, 2008, 01:27:19 PM
I don't know if it's just a mistake on your schematic but you've drawn it with the 1M5 biasing resistors for the 4066 connected to ground, they should go to 5 volts. I don't know if that would cause the problem you're having though.
:o :icon_redface: i misread that on the first time and took for granted from then on.
that is a very probable cause of problems. there are coupling caps though ??? i will try tomorrow and see what happens
strange is that those 4066 worked fine with the signal biased to ground, there is supposed to be a heavy clipping in that configuration.
thanks indeed Slacker
biasing hasnt solved anything. Even taking the 4066 out of the circuit doesnt make any difference.
Looking at the PT80 schematic, it has a buffer right at the output, probably to make the compander happy.
Borrowing the idea and placing a buffer right before the output bifurcations seems to have solved the issue, maybe in not a such elegant way.
i really dont know if those resistor values are appropiate (any help there?), at least it sounds ok.
(http://img376.imageshack.us/img376/2456/delaybufferqs7.png) (http://imageshack.us)
I am still concerned about the distortion i noticed in the original echobase. Is it a common isue or is it just me doing something wrong?
What about all those 100n caps? For what i've seen, the usual is 1uF and bigger
thanks!
I can't understand how making the 47k resistors smaller would affect the feedback level.
The only thing I can think is that the lower value is allowing some signal to take a different path through the circuit and that is causing the problem.
Try putting the 47ks back in and replace the 10ks on pins 16 and 13 with 22ks, that will give the stages about the same amount of amplification. See if that solves or reduces the problem.
No one else has mentioned anything about distortion so perhaps you have a problem somewhere. Is the bypassed sound clean?
About the 100n caps, I used them originally because I had a lot of them. However, I've done the maths and combined with the other components they are large enough to let all useful frequencies through, so there's no need to make them any bigger.
Quote from: cpm on October 03, 2008, 06:37:25 PM
there are still some typos there, and a couple of resistors missing
It's so twentieth century to call your hand-written errors "typos" :icon_lol:
This is incredible work. I'm really just posting so I can encourage you guys and have it pop up under "show new replies" whenever something comes up. I plan to build my echobase as soon as I get together enough $$$. I'm afraid I can't offer much until then. Keep up the awesome work, though!
Quote from: cpm on October 03, 2008, 06:37:25 PM
there can be mono or stereo ping pong with a couple of switches ruled by the output jacks (using the stereo pin to ground as trigger). That way, for example: only connecting out A, you have amix of "ping and pong", both outputs is for the full stereo panning, and B only is for a long delay time using both chips. Can be made with more 4066 cells, or some kind of FET switching.
A dual pot on delay time will give symetric stereo delays, or two independent pot may give a more complex pattern, like "taa-ta-taa-ta-taaa" :icon_lol:
:icon_eek: WOW! I am TOTALLY building this.
a provisional schem: http://bayimg.com/LalglAabk
this is how i build it up. Its basically a doubled echobase and some additional workarounds
the schem is not verified though. There may be also some mistakes or ugly things regarding components and design.
Has anyone verified the schematic yet?
this is the updated schematic which i think is the one that will stay for me.
(http://img525.imageshack.us/img525/8396/delaystdb4.th.png) (http://img525.imageshack.us/img525/8396/delaystdb4.png)
Does that schematic include the extra delay time?
it does two PT2399 in series, so the delay path goes U1->U2->U1->U2->U1...
playng with the control signals you can have the output at out_B which is U1+U2 (long delay), or out_A with the mixdown from each U1, U2, ... (shorter times), or both outs A & B with separate U1, U2 times respectively, also with clean mixed in or just the delayed (wet) sound
Very cool. Now I just have to figure out how to mix this schematic with all the mods in the other echobase forum.
Thanks much,
Conrad
I've printed out the schematic and I'm trying to figure out how all of this connects. If anyone could give me a brief walk-through of the signal path, I would greatly appreciate it. Also, I can't seem to figure out where the ping-pong vs. extra delay switch is.
Thanks
I'm doing my best to figure out this schematic, and I've compared it to the original. I'm getting quite a bit confused. I've used the 4066 chips on most of my recent effects, and I don't understand some of their purposes here. I can tell that one of them is for the LED. The next two (moving up and to the right) are the input bypass. The two at the top and right are the output bypass, controlled by the boss/tails swicth (I'm assuming). The one in the middle of the upper right is whether or not the two ends of the stereo are connected, which amounts to the extended delay vs. ping pong? If there are six of these, then two 4066's are needed, and more than one switch is required to activate them. I'm assuming that, if I'm using a DPDT, the LED and the in/out controls can be powered with it. The mix can be a spdt, and not necessarily a foot switch. The LED, the mix, and the boss/tails don't have to be 4066 switches
The Out_CLEAN section is also confusing. I'm guessing that gets connected to both ends (or whatever you want) to mix in the clean sound. Seems self explanatory, but I want to be certain before I make a mistake.
Both pt 2399 chips are connected back into each other, by the looks of it. So, every time the chip processes the sound, it is output to it's designated out, and also input into the other ship, which then processes the sound and puts it out to its own output and back into the other chip, etc. So that's how the ping pong part works. What changes to allow it to be just extra long delay? Or does the ping pong delay even have that as well?
What do switch 1 (a and b) and switch 3 do? It looks like switch 3 grounds the current on the control of the bottom left switch, which would turn off the LED? Does it also change the transistors in the bottom left? How do those transistors affect the circuit? Also, what is the significance of the jack rings (B and CL) in the schematic?
I have several switching jacks, and I am planning on having the two outputs go into one output jack unless the second jack is plugged in. Shouldn't be too hard to wire. I should check and see if I can find a stereo switching jack so that I can have the option of using a stereo quarter inch jack.
In the switch that separates or incorporates both sides of the stereo, what is the purpose of the capacitor connected to the right side? Is it merely to remove the voltage offset? Also, most of the input/output caps are 100nF, which is .1uF. Can I change these to larger values? I play bass, and people typically recommend that. I'm assuming 4.7 or 10uf (i've got plenty of these) will do fine. That won't change too much, right?
With the input and the output switches, why is there already a 9v supply going through a 220K resistor? How much does this drop the current? What purpose does that serve?
What is the difference between boss and tails mode? The tails allow the delay tails to taper off after the delay is bypassed. Does boss cut them off abruptly? I've never understood a lot of the switching options. I understand true bypass and I understand the 4066 chips, but I don't know what boss-style bypassing is.
Does having the feedback only on one of the two channels affect anything? Does is do the same thing as it would in the original echobase? I will admit I have no idea what the feedback does, or, even, what it really means in this case. If anyone can help me out here, that would be awesome.
Also, has anyone had success modifying this version to use the waveshape and envelope mods? I'm thinking that I want to build this thing with all of the whistles and bells, so I want to work both of those mods.
Switch 2 seems to be in charge of the boss/tails section, as well as disabling the LFO. Is this supposed to be two different switches? I'm trying to figure out how many SPDT's I need to order.
The wiring of the LFO into the two PT2399 chips is slightly different than on the original schematic. Is there any real difference in performance?
I think that's about all the questions I have. If any of the things I said are wrong, let me know.
I'm excited to get working on this. Thanks again.
Conrad
a lot of questions there... :icon_mrgreen:
As you've guessed, chips are in series, one after the other, so delay time can be doubled as the sum of both delay times, and taking the "long" output at the out of the second chip (out B). Feedback here is called to the signal going from the output at the second PT to the input of the first one. At the output of the first chip (out A) it would be in the middle of the "long" delay time.
Using separately both outputs there is a stero ping-pong effect. Using only out B there is long delay time. Using both out A & B (mixed down into one physical output) there is short delay time.
The switching in the original echobase is ctl_A for the input to the delay line, ctl_B for the output of the delay line, and the led switching.
There is 9v through 220k into the 4066 to make a default logic "1", the control wires pull it down to ground in order to disable the 4066.
For the stereo version you can see switch B is duplicated. Also added more switches for controlling A&B mixdown (for short delays into out_A), and clean mixdown (for a 100% wet)
the original echobase uses a simple NPN inverter/buffer for the switching. Physical switches are still "bypass" and "LFO", both SPDT. Additional switching C & D is switched directly from the output jacks. When a mono jack is inserted in a stero jack its ring terminal connects to ground, so it can be used to control the 4066 switches. I used mosfet (as used in a millenium2 bypass) as a quick a dirty solution, but that can be improved with a NPN like the original bypass switching, a real CMOS inverter, mosfet pair... i guess its important to not flow significant current into the encloseure (
for the A & B control wires i changed the way the boss/tails switch behaves. i care that no signal enters into the delay line when the effect is bypassed, in order to always get a "clean" start when the effect is engaged.
The out_clean output is just buffering the clean input (no effect), and switching automatically for a 100% wet output (no clean mix). my usage is for getting three outputs: A & B (delayed only), and C (clean output without effect).
Some 4066 are biased to GND instead of 5v. Thats weird but i settled on that to avoid noises when switching. Those made a loud "pop" when biased to 5v. It may be circumstancial or not, but it worked for me anyhow.
For the LFO part the only addition is a switch for the cap to enable/disable the oscillation
Okay, so it seems that a lot of the switching falls into the realm of things I don't easily understand. For my sanity, I think I'll try to swap out some of the FET switching with switching jacks. I see that you updated the image with a list of what everything does, which is very helpful.
I'm confused about control D. On the schematic, Control D connects the input to the two outputs to have the clean sound. There is also another buffered output of the clean sound. What is this used for?
How is the extra delay vs. ping pong changed? Which switch is it?
I have to admit I have no idea what the high pass delays and more feed back means. I don't really understand the feedback anyway.
The switching, for me, will then amount to something like this: DPDT for bypass control in 4066 and the LED, Switching jack to determine whether there is one output or two, SPDT for LFO, SPDT for ping pong/long, SPDT for delay tails (attached to DPDT and then to 4066), and an SPDT for the highpass(?) thing. I would either forget about the control D switch entirely, or replace it with a pot. What is OUT_CL anyway? Will these mods still work? Am I forgetting anything?
Thanks again. I know I've got a lot of questions, but I'm not to the point where I can just immediately understand everything.
Quote from: Radamus on December 26, 2008, 05:28:10 AM
Okay, so it seems that a lot of the switching falls into the realm of things I don't easily understand. For my sanity, I think I'll try to swap out some of the FET switching with switching jacks. I see that you updated the image with a list of what everything does, which is very helpful.
the switching is done that way to be actioned without switches, using the output jacks whether there is a jack or none pluged in.
QuoteI'm confused about control D. On the schematic, Control D connects the input to the two outputs to have the clean sound. There is also another buffered output of the clean sound. What is this used for?
for my needs, i want the possibility of having the clean signal separated from the delayed sound. As in the echobase, clean input is always mixed at the output, so the switch at D should be a default "on". What i do is break that switch when a jack is inserted on the third output (buffered clean)
Quote
How is the extra delay vs. ping pong changed? Which switch is it?
the ping pong is obtained by taking both outputs A and B
A long delay is obtained by only using out B
Shorter (and cleaner) delay is obtained by mixing A and B outputs, so thats the reason for the switch that connects B into A's summing opamp. This switch in ON when there is no jack inserted at B output (i would only plug in out A, using only one output since theres no need for stereo here)
Quote
I have to admit I have no idea what the high pass delays and more feed back means. I don't really understand the feedback anyway.
Feedback is the delayed sound which is inserted again to the input of the delay. In this case the ouput at PT2 is inserted into PT1's input. Witchout feedback you would only get one repeat (the clean note and the repeat after the delay). Feedback produces multiple repeats, by regulating its volume you make each "trip" to sound quieter until it fades out, thats what the "feedback" pot does. If the 2feedbacked" signal is higher than the ouput, there will be a volume increase with each repeat, leading to a loud noise and sonic chaos, as repeats never fade out.
The pair of caps (plus a switchable cap) you refer have to do with the filtering applied to each repeat as it passes through the delay chip. From some experimentation i found that having different values changes the way that filter behaves. For a 1:1 ratio (100n+100n as echobase, rebote, etc) the filtering is somewhat flat, softening each repeat into a darker sound. Switching the third cap (in parallel) there is a 1:2 ratio (100n+200n) which changes the filter to allow more highs to be kept for each repeat.
You can think of it as a "dark / bright" switch. For me the "bright" setting works best for near "infinite repeats" for it doesnt get all muffled on the low end.
Quote
The switching, for me, will then amount to something like this: DPDT for bypass control in 4066 and the LED, Switching jack to determine whether there is one output or two, SPDT for LFO, SPDT for ping pong/long, SPDT for delay tails (attached to DPDT and then to 4066), and an SPDT for the highpass(?) thing. I would either forget about the control D switch entirely, or replace it with a pot. What is OUT_CL anyway? Will these mods still work? Am I forgetting anything?
Thanks again. I know I've got a lot of questions, but I'm not to the point where I can just immediately understand everything.
OUT_CL, as explained, is a buffered output that always follows the clean input. It may be removed if not needed.
For the switching, all you need is to let or not to let the sounds pass through some places. As long as this is accomplished you can use whatever you feel like, raw switches, 4066 controlled by switches or jacks, momentray switches plus latches... whatever that does the trick
The main reason for 4066 here is the need to turn some sitches simultaneously with one single stomp on the switch.
good luck
Okay. Very cool. Thank you for all of that help.
I have one last question (I think). If having a single input makes it extra long delay, how can you be using two amps (for ping pong) and then switch it to extra long delay out of both outputs? I would like that to be an option (and possibly another footswitch) so where would I put that? What needs to be changed for that to work?
Thanks again for all the help.
Conrad
Another thought occurs to me. I like the idea of being able to have a rhythmic repeat, almost like a loop, with the infinite repeats. How can I make it so that the delay "resets?" What I mean is, how can I stop the repeats without necessarily disengaging the effect? I understand that this is by no means a looper, mainly due to the limitations of the pt2399 chip, not any of the wonderful work that has been put into the project, but I'd like to know how I can use it in that regard in a limited fashion. For example, I play a single note on my bass with a quick, infinite repeat. It will get distorted, but I kind of like that idea. It will play consistently. I will disengage the effect, but the delay tails will allow the chip to continue. If I want to stop it, I know one way is to interrupt the feedback for the length of the delay, which can be up to nearly two seconds with this version. Is there another way to quickly reset the chips? I would need this to be in a footswitch, but I'm not sure I can get a momentary one to hold the effect loop off. The ones that are out right now seem to all be expensive, big name effect switches. Is there an easier way? I wouldn't necessarily mind using another DPDT to switch it.
I hope I'm not taking the project too far beyond its original intent, but this doesn't seem to be an enormous departure or even that difficult. Thanks for all the help, again.
you can silence the delay by putting its audio input to ground.
for what you want, you may use two parallel delay lines. One is the main delay effect, another one would be setup with strong feedback and switched in only when you want those infinite repeats, and mute it when switched off. This way both delays go into the mixing opamp the same way the echobase does.
How much current does this draw? I want to make sure I buy the right parts for a power supply I'll be building too.
Thanks.
Does anyone have a layout or a picture of their build I can check out?
Hello,
I am working on drawing up a layout for this project. While I was thinking about it, I came up with a couple things I'd like to change, and I was wondering if any of you could help me make this work.
The functionality of the project is still the same, but I want to change the output switching slightly.
As it is, putting one jack in A give you Rhythmic delays in one speaker. One jack in B gives you extra delay. Two jacks gives you ping pong. I would like to have the option of switching back and forth between rhythmic/ping pong and long delay.
The way I'm thinking about it is like this: DPDT footswitch. Middle pegs connect to delay out A and delay out B. The top peg of the B side connects to both stereo outputs (need suggestion here for splitting signal). The bottom of the switch connects to a DPDT switching jack where, if no plug is there, then A and B connect together and then to the single output (Rhythmic delay). If a plug is present, then each delay goes to its respective output (ping pong). This would give me a DPDT footswitch which changes ping pong to longer delay without changing the input jack. Then, the switching jack determines ping pong vs. rhythmic.
So, then, I need help with whether I can get away with putting resistors in series with each delay line to split or combine them, or whether I need to get into some more serious buffering. I have on extra op amp due to not using the clean output section. I am only using one 4066 as I replaced the mixdown (control C) with a footswitch (and I will probably place it later on) and control D with an SPST.
Let me hear your ideas.
Thanks in advance