Visual Sound H2O opamp replacement

[surfdaworld]

Hey y'all!
just got a new Visual Sound H2O Chorus/Delay pedal that didn't work for $28 off ebay, and was able to get it working by replacing the onboard JRC4558's, (which apparently came from a bad supply batch) with TL082's.

my problem (if it is a problem) now is this:
when the 'Repeats' knob of the delay side is turned past 2 o'clock, the effect level begins to drop, and continues dropping as the 'Repeats' knob is turned, until the knob reaches its maximum, at which point the effect level is only about 50% of its maximum potential.
  Since I've never played any other H2O pedal, I don't have anything to reference this by.  I was wondering if some of you who own this pedal could tell me whether this sounds normal for this pedal, or if it's not normal, do you have any ideas as to what could cause this?

Thanks in advance!
    --TJ

[rockgardenlove]

You sure came to the right place!
RG ( http://www.visualsound.net/rgkeen.html ) is a regular here and should certainly be able to help you out. 

Welcome to the forums! 

(Oh, and did anybody else notice that the title of that page says "Visual Sound - R.G. Keene" and not "Keen?" Odd.)

[R.G.]

just got a new Visual Sound H2O Chorus/Delay pedal that didn't work for $28 off ebay, and was able to get it working by replacing the onboard JRC4558's, (which apparently came from a bad supply batch) with TL082's.

There are some clues there.

I'd have to check the most current manufacturing to be sure, but to the best of my memory the H20 does not use JRC4558s unless it was a recent manufacturing change. I think what you have is one that someone "improved" by replacing all of the opamps for more mojo. That might explain it being on ebay - a botched mod. It's a possibility. I think all of the opamps in there are originally TL072s.

What you describe is not normal, I think. At least mine doesn't do that. I'm wondering if there were other "improvements".

If replacing the opamps didn't do it, you might try replacing the electrolytic caps, observing polarity carefully. The square pad is positive. Otherwise, it might be anything.

The H2O predates my time at Visual Sound, so I'm not the world's authority on it. You might contact service@visualsound.net for some advice. Dave is an expert.

(Oh, and did anybody else notice that the title of that page says "Visual Sound - R.G. Keene" and not "Keen?" Odd.)

I just looked, and it has "Keen" now. They must have caught that.

This is just one of the fallouts of having a non-standard name. Last names with only one sylable are an issue. People just don't get enough info from the single sylable to nail a word down, so they guess the closest one that they're familiar with. With "Keen" that's "King". And when they do ear it correctly, they spell it with three e's, as that is more common than the two-e version.

Even with two sylables, "R.G." becomes "Archie". At restaurants when they want a name for a table, I tell them "Fred". It's simpler and quicker.

[rockgardenlove]

Aw, I figured you would be the go to guy.  This place is still great though!   

As for the name-I mean at the top...up on the menu bar:

Like so.



And is R.G. your actual name?  I always figured it was your first two initials...

[R.G.]

And is R.G. your actual name?  I always figured it was your first two initials...

It is initials, but it's the only name I use.

It's a long story. It'll have to wait until we can buy beer while we go through it. 

I see the title. I just blew past that. I suspect our web master did the pages based on verbal instructions and he made the second mistake.

[rockgardenlove]

I suggest we petition Aron for one of these smilies:


I should also stop spamming this guy's thread...peace!

[surfdaworld]

 
Wow!

Thanks RG and everybody for the quick responses!

if this was a botched mod, it was done by someone with some very competent soldering skills--I was unable to visually detect any signs of user tampering on the board.

in regards to the original TL072 opamps that you remember this having, RG, are the TL082's I replaced them with a workable replacement?

what is the best all-round op-amp upgrade to use, generally?

Does Visual Sound guard the schematics for these pretty closely?

Thanks again!
   --TJ

[jonathan perez]

Even with two sylables, "R.G." becomes "Archie". At restaurants when they want a name for a table, I tell them "Fred". It's simpler and quicker.

i do the same thing! 90% of the time, they spell jonathan incorrectly. so i just say Jo.

[petemoore]

in regards to the original TL072 opamps that you remember this having, RG, are the TL082's I replaced them with a workable replacement?

what is the best all-round op-amp upgrade to use, generally?
  These are all good dual opamps, any dual should work really good...whether you can tell any much difference between 082's and 072's in the chorus...they're both already 'high grade' IME.

[heyniceguy]

best all around op amp? i'd say the TL072 for the price. very low current consumption and clean as a whistle.

my name is JB, which becomes Jaime quite frequently. but often once people get past that, it becomes BJ or DJ. feels like i cant win.

[R.G.]

if this was a botched mod, it was done by someone with some very competent soldering skills--I was unable to visually detect any signs of user tampering on the board.

Weird. It sure sounded like a botched mod. Ah, well. It was just a theory. The 4558's are not going to work all that well in there even if they are good; there are a couple of places where high input impedance and the higher gain-bandwidth of the JFET input types are really needed.

in regards to the original TL072 opamps that you remember this having, RG, are the TL082's I replaced them with a workable replacement?

As the others have said, yes, they will be fine. The TL06x, 07x and 08x opamps are a family of opamps with similar technology and specs. The 06x family is optimized for low current drain at the expense of noise performance and high speed. The 07x group is normal performance, and the 08x group is low noise at the expense of higher current draw.

what is the best all-round op-amp upgrade to use, generally?

Unless I know of a specific reason not to, I use TL072s for everything. They are very, very good for the price. They are not the quietest opamp, but they not too far back in the pack. They are not the fastest opamp, but they make lots of other opamps look slow. They are not the lowest distortion or most innocuous distortion, but to get better you have to pay many times the price, and some more expensive ones are not as good.

About the only reason not to use them everywhere is that their input common mode range does not include ground or +V, and their output range is about a volt from each supply. That means that there are some LFO and control voltage things they can't do, but they are very impressive for the money.

Does Visual Sound guard the schematics for these pretty closely?

Yeah, we do. As long as were not going to bandy about schemos for some manufacturers here, we'd prefer to be included in the ban. I could show them to you, but then I'd have to kill you...   

[surfdaworld]

Pic removed by me out of courtesy to RG

'k here is the pic of the mainboard--I've notated the components that are relevant thus far.

-IC 1  was a TL072 when I got this--replaced it with a TL082  (the original chip was working, but I had a spare anyway)

-IC 2  was a JRC4558, replaced with a TL082  |
                                                                   |---These chips were the culprits when I got the pedal--replaced them and started getting sound.
-IC 3  was a JRC4558, replaced with a TL082  |


so now the problem is the effect level of the delay portion.

as I said, the effect level diminishes as the 'repeats' knob is turned up.

If my trace is correct, the left leg of the 'repeats' pot is connected to ground, the middle is the signal supply from the delay chip, and the right controls feedback back into the circuit.

If I run an audio probe on the middle and right pins, I notice the same effect as on the output jack--as the knob is turned up, the effect level decreases.

This is purely conjecture, since I haven't worked on many delay boxes, (much less this one), but is it possible that the delay circuit is sucking too much current as the signal is fed back in, causing the level to drop?

RG, perhaps you could give me a hint here--is there supposed to be a gain recovery stage of some sort after the feedback loop?

thanks again!

--TJ

[R.G.]

Please email me at k8e8e8n8@8g8e8o8f8e8x8.8c8o8m minus the "8"s.

[surfdaworld]

Thanks RG!!!!   

looks like R14 was the culprit

[Cliff Schecht]

R.G., do you still live in Austin? I'm down here now as of Christmas break (I'm an EE up at Texas Tech) and while I'm here, I'm throwing together quite a few projects that I've had in the plans. Do you ever travel down to M.C. Howards by any chance?

[R.G.]

Hi, Cliff. Yes, still in Austin. Well, kind of. Any time it freezes I move south, and the last freeze we had in Austin I moved to Dripping Springs.

I used to haunt Howards a lot, but recently I've been so busy with some new design projects that I haven't been there in quite a while. We're just about to go Christmas jaunting to see the relatives, or I'd meet you there. I remember with some longing having the prospect that the time between Christmas and New Year was going to be a long uninterrupted stretch of whatever I wanted to do. Enjoy it!!

[Cliff Schecht]

I defenetly am enjoying the break, my way. I spent about $40 on parts at Howards and about $20 or so more at Fry's (plus a re-up on tooling from Harbor Freight), but it's well worth it to me. I could go spend well over $1000 on all of the effects I plan on building over the break, but instead I build stuff for about $10 a build on average. For electronics as a hobby, it's hard to beat Austin.