Building the Echo Base PCB

[hoyager]

Thanks very much.

this from slacker

"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'll use a 3.3k instead.

One more, I'm pretty sure I'll only want slow modulation and not very deep, the mod below seems like the one for me

"If you want to tame the modulation depth then make the 240k resistor before the mod depth pot bigger. You'll have to experiment with values but
hopefully that will give the pot more of a useful range. For the mod speed if you want the fastest speeds to be a bit slower then make the 27k resistor
after the speed pot bigger, and if you want the less of a range overall make the speed pot smaller.

Can you recommend a good substitute range for the 27k resistor? and also is the slowest speed very slow? like <1hz? If not is thre a quick swap out for that?

Thanks so much for the board and your help
Andy

[slacker]

You might not need to mod the 10k resistor, I tried changing the 47k resistors to 24k in mine and there was still plenty of volume without changing the 10k.

The LFO goes from about 0.33Hz (1 cycle every 3 seconds) up to about 15Hz. I would only change the 27k resistor if you just want small changes to the maximum speed. If you want to make the LFO go much slower or much faster then change the 1uF cap, doubling it will make the LFO roughly half the speed and halving the value will double the speed.

[Taylor]

Yo fellas, I've added several mods including the "humbucker-friendly" resistors to the Echo Base PDF:

http://www.aronnelson.com/gallery/main.php/v/Taylor/

[StereoKills]

Does anyone know offhand how far apart the pots are placed?

[Taylor]

The pots are .8 inches center-to-center. (20.3 mm)

[StereoKills]

Awesome, thanks!

[hoyager]

Hey fullas. Awesome delay, had it going yesterday and its totally what i'm after. Thanks!

I had a few issues getting it going to begin with, mainly the chips weren't pushed in hard enough I think, but I swapped the resistors I'd changed back to the original values as well, except for the 47k to 22k's.

However, I tried plugging it in later yesterday, and i *think* the + and - shorted (an intense hum from the speakers?). The dry signal then was still going through but no more delay (the lfo was still working too).

I then replaced the delay chip, 4066, regulator and the both TL072 and its working again, not quite optimaly I don't think. Are there any other bits I'd need to replace after the possible shortage?

Power supply could be an issue, its giving 10v to the board even though its a 9v.

In the process of debugging I've resoldered everything and am 99% sure everything is in the right place and the right value.

A curious thing is happening also when I measure the upper 220k resistor beside pin 13 of the pt2399 on the board, it gives me 1073ohms (also 7.3kohms, not quite sure which range to test it with (gives 018 in the 2000k range). If I pull it off the board its fine and measures 220k. I've measured a new one, put that in and a similar outcome. The other one next to it is fine on the board at 220k

here are some voltages

PT2399
1. 5
2. 2.5
3 0
4. 0
5. 2.55
6. 2.5
7. 1.3
8. 1.3
9 - 16. 2.5

TL072
1. 5
2. 5
3. 2.5
4. 0
5. 5
6. 5
7. 5
8. 10

TL072 LFO

1. changing
2. 5
3. 5
4. changing about .9
5. 4.15
6. 5
7. changing
8. 9.15

4066
1. 2.86
2. 2.86
3. 0.15
4. 0.15
5. 0
6. 0.88
7. 0
8. 1.76
9. 1.76
10. 2.86
11. 2.86
12. 8.3
13. 9.55
14. 10

This is the second thing I've built so, was hoping just to do everything right the first time, so I didn't have to bother with this stuff... (which I don't really know about)

here are some tests as it its at the moment

ebasetest3.wav


ebasetest2.wav


ebasetest1.wav

These are mostly done with the level and feeback knobs almost all the way up, which it seems they have to be.

Many thanks
Andy

[Taylor]

Hey Andy. Your clips sound great, I wish I had an electric piano.

I can't quite tell what the problem is. What issues are you having now? It sounds like it's working properly to me. The resistor value is no problem, you can't usually get a reliable resistance reading when a resistor is in circuit.

[hoyager]

Oh cool, thats good to hear it sounds normal. I think I must just be tripping after working on too intensly!

I've wanted a vibrato for quite a while, makes the rhodes sound even more old school...., I'll be doing that mod for sure

Would shorting out the 9v and ground have blown all the chips?

[Taylor]

I'm not sure, but in any case you didn't blow all the chips, or else you wouldn't have had a clean signal in bypass. Listening back to your clips, doesn't seem like anything's wrong, but you tell me if the knobs aren't functioning or something.

I think "Cowboys" by Portishead would make a nice test for the Echo Base+Rhodes combo....

Someone asked via PM about my dual-purpose footswitch wiring, so here it is:

[incubus20851]

Hey, Thanks for the diagram !

Can't wait to receive the PCB to start building this beautiful pedal !

[hoyager]

Cool, thanks for all your helps. Hoping to order 3 more boards tommorrow.

2 quick questions;

Can I use lower than a 3.3k (which replaced the 10k beside pin 1 of the 4066) to get more volume from the delay (seems like I have the level all the way up most of the time)? and if so is there a ball park for the value? ie. is 220ohms too low/small?

Also, is it possible to boost the bass response on the delays with a simple mod, or would this just clip the 2399?

Many thanks
Andy

[Taylor]

I wonder why your volume is so low? Did you change any other resistors?

Instead of lowering that resistor, I'd change the resistor in the feedback loop of the opamp to raise the gain. On the PCB, it's directly to the right of pin 5 of the TL072 under the Level pot. Raising this value will raise the gain of the opamp.

Do you want to boost bass, or cut highs? Cutting highs would entail changing some cap values in the feedback loop. If you want to boost bass, you'd need to build a separate bass boost circuit (which would probably just be a lowpass filter combined with an amp stage) and insert it in the feedback loop.

[hoyager]

mmm.. the 2 47k's have been replaced with 22k. that could be it actually, was concerned about getting to much distortion.

with these back to 47k would the level knob be able to dial out distortion from hot signals?

cheers

[Taylor]

No, if you distort the PT2399 the volume knob will not change that distortion as it's after the delay chip. I honestly don't know anything about the signal a Rhodes puts out compared to guitar or bass so I'm not sure what you should do about levels.

[frequencycentral]

I honestly don't know anything about the signal a Rhodes puts out compared to guitar or bass so I'm not sure what you should do about levels.

My Rhodes is much hotter than a humbucker. But, just like guitars, it's all in the setup too. There's a lot you can do with the positioning of the tines with respect to the pickups which will affect the tone as well as the volume. Anything from subdued and mellow to brash and almost ring mod. Last time I set up a Rhodes it took me a week to get consistency across all 73 pickups/tines. You'd certainly want to attenuate before hitting a particularly sensitive effect designed for guitars.

[ibodog]

In a build I have here I've added momentary switches for the on/off switch and the feedback mod.  On that feedback mod, is there any way to ramp up and ramp down the time it takes to get to "full" feedback? 

[Taylor]

You could try adapting this:

http://www.geofex.com/article_folders/lera/lera.htm

[slacker]

Instead of lowering that resistor, I'd change the resistor in the feedback loop of the opamp to raise the gain. On the PCB, it's directly to the right of pin 5 of the TL072 under the Level pot. Raising this value will raise the gain of the opamp.

If you change the feedback resistor you will increase the volume of the dry signal as well, which doesn't sound like what hoyager wants. If you just want to increase the volume of the delayed sound, then lowering the 10k after the level pot is the way to go.

I've now done the 22k mod on mine, I actually used 24k but shouldn't make much difference, and the volume of the delays is a bit lower than on my original version. I haven't changed the 10k resistor and the maximum volume of the delays is fine, it should be about the same or slightly louder than the the dry signal, if not there's possibly a problem somewhere else.
The first half of the pots rotation is a bit quiet though, half volume is about the same as a quarter on the original. It might be worth trying a 100k linear instead of log, that should improve the feel of the pot and make lower settings louder. I haven't got one the right size to hand otherwise I'd try it.

On that feedback mod, is there any way to ramp up and ramp down the time it takes to get to "full" feedback?  

Here's a quick idea that should do what you want, it's basically a stripped down version of what Taylor linked to. Points A and B connect where the blue and red wires go on Taylor's diagram above.



It should probably have a current limiting resistor between the switch and the pot and you'll need to experiment with the values, but the ones shown should be a starting point.

[dmc777]

Does anyone know of a mod for this to allow the unit to run 100% wet for parrallel mixing? Maybe a kill dry switch or something? I know it's gotta be something pretty easy but I'm kind of a newb. Any help would be highly appreciated. Thanks alot guys!