Rebote Delay Troubles

vigilante397 · March 22, 2014, 05:59:31 PM

Lately (and by lately I mean for the past couple months

) I have been trying to get a decent delay built. Lately I've been trying for the Rebote, and last night I finally got one working. I was obviously remarkably excited and I made preparations to box it. But when I got it into the box, it started giving me ridiculous noise. It still works, but the noise makes it almost unusable. The only thing I'm doing different from last night (aside from the box) is using a different power supply. Last night I used 12V 1000 mA (my favorite

) and today I just used a 9V 300 mA (what I understand to be relatively standard). I'm at work now, but I plan to test it again this evening with the 12V supply to see if that was it, but I would expect it to run off 9V 300 mA with no problem.

Has anyone that built a Rebote had a similar experience? Any suggestions as to what else I could try?

vigilante397 · March 23, 2014, 12:22:10 AM

UPDATE: I tried out the 12v 1000mA supply again and found that the noise is significantly quieter to the point at which it could be considered usable onstage, but it's still there. Any ideas? $:-\$

PRR · March 23, 2014, 02:53:49 PM

Does this Rebote have _any_ power supply filtering?

vigilante397 · March 23, 2014, 04:35:27 PM

Quote from: PRR on March 23, 2014, 02:53:49 PM
Does this Rebote have _any_ power supply filtering?

An excellent question. I have some lovely caps I use for just such purposes, but I don't recall putting one on this build. That's definitely worth taking a look at. I'm sitting in church now (yes, this is what I think about during church), but I'll check when I get home. Thanks

vigilante397 · March 23, 2014, 08:05:44 PM

Before I explain what I have done, let me show you what I'm working with. I know vero layouts are like the bastard stepchild of schematics and PCB layouts, but this is what I'm working on:

I assumed that the 100nF cap connecting the output of the regulator to the ground was the power supply buffer, but I tried upping the value of that as high as 100uF with no real change. Am I doing this right? Where should the buffer go?

vigilante397 · March 23, 2014, 08:06:41 PM

Also, because I know people like schematics, here is this:

PRR · March 24, 2014, 12:47:21 AM

The Q1 FET stage has "ZERO" power-crap rejection.

The 47uFd at the +9V power rail does try, but if the power supply is sufficiently rude yet strong, it is like my Corgi trying to catch the school bus.

That FET stage is the only stage subject to raw power crap. The '2399 has a regulator. And the FET does not need much power. A rough R-C filter ought to make a big difference.

You can hack this on your Vero by lifting the "top" end of the 6K8 next to the 78L05, running 470 Ohms (270r to 1K) from the +9V to the 6K8, and flying a good cap (22uFd-100uFd 16+V) from that air-junction down to the ground strip (which is pretty cluttered here, but maybe you can sneak into the hole between the 100u and the '2399).

Better (less buzzy) power supplies are also a good thing to have. This isn't 1980 again; well-filtered power supplies can be found in guitar stores.

vigilante397 · March 24, 2014, 01:15:43 AM

Quote from: PRR on March 24, 2014, 12:47:21 AM
The Q1 FET stage has "ZERO" power-crap rejection.

The 47uFd at the +9V power rail does try, but if the power supply is sufficiently rude yet strong, it is like my Corgi trying to catch the school bus.

That FET stage is the only stage subject to raw power crap. The '2399 has a regulator. And the FET does not need much power. A rough R-C filter ought to make a big difference.

You can hack this on your Vero by lifting the "top" end of the 6K8 next to the 78L05, running 470 Ohms (270r to 1K) from the +9V to the 6K8, and flying a good cap (22uFd-100uFd 16+V) from that air-junction down to the ground strip (which is pretty cluttered here, but maybe you can sneak into the hole between the 100u and the '2399).

Better (less buzzy) power supplies are also a good thing to have. This isn't 1980 again; well-filtered power supplies can be found in guitar stores.

Paul, this forum is lucky to have you, and I'm lucky that you're here. If I can sneak my soldering iron off of my desk without waking up my wife I'll try it out tonight, if not I'll do it in the morning. Thanks a million, and I'll let you know how it goes.

I've been meaning to grab me a decent power supply, but the closest decent guitar store is about 150 miles away, and I'm not really sure what I'm looking for enough to feel confident buying online. My board runs quietly, mostly thanks to on-board buffers like these, but can you recommend a particular power supply that runs quietly?

vigilante397 · March 24, 2014, 02:05:48 AM

Paul, you sir are a genius. My build was pretty tight as it was, so I ended up building a 4x4 "buzzkill" daughterboard and wiring it into the main board. I didn't have any 33uF caps so I went straight to a 47uF and it's absolutely perfect. If you're ever in the Idaho area let me know and I will buy you lunch.

PRR · March 24, 2014, 03:50:06 PM

> confident buying online

I have no specific suggestion.

It does seem that in recent years one or a few pioneering "pedalboard supplies" has moved the market away from many 9V batts or a collection of poorly filtered supplies toward a holistic plan with good filtering and board-worth daisy-chain cables. Basic-supply price target seems to be $20/$30-- a tight fit for the manufacturer but a good fit to extract spare change from musicians. You can pay more. And less.

I'd read (but not swallow) the reviews on Musician's Friend, Amazon, etc. Many reviewers are idiots, or just incoherent. Some are grinding axes. And some are "friends" of the marketers (both for their product and against competitors). But reading a few dozen, you can get a sense of what some "Reasonable Man" (woman) might say about the product.

Here is one retailer's "Most Popular" pedal (and other) power supplies:

http://www.musiciansfriend.com/amplifiers-effects-power-supplies

I don't know why one brand is $19 and another is $109-$300. Both average 5.5 Stars which is an astonishingly good user-opinion for any web-review (there's always 10% of users who got the rare dud, have a stupid gripe, or just can't count/click stars).

OK, $19 buys just the power, the same thing with a bunch of ends is $31. There is a competitive $31 package with similar good stars.

$109 buys four 9V outlets, *isolated* (sometimes that matters), one shared with a 12V out, and an 18V out so you can really juice-up (or fry) one pedal. I can't tell if it comes with cords.

I think the $19/$31 job is supposed to cover "most" musicians' needs. While pedals should be proactive against crap power, quality power (low hum, steady voltage) is also a real fine idea.

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Rebote Delay Troubles