Visual Sound H2O, want to shorten min delay time . . .

[vseriesamps]

Hi you all

I have a Visual Sound H2O delay/chorus pedal which is a cool thing, but I'd like to shorten the minimum delay time for the delay side. Their website says the pedal uses two chips, an MN3102 and an MN 3207, I can't say myself if they are shared by the chorus and delay or what. Their tech help says these chips set the delay time and the pedal as is cannot be modified to make it shorter. I'm wondering if there is another chip I can use as a drop-in replacement that would have a shorter min time? or is there another trick to be employed? I wish I could offer up a schematic . . .

Thanks everyone in advance,
-k

[Dirk_Hendrik]

The delay is made with a PT2395 chip. The MN's are for the chorus portion.

[puretube]

ooops - didn`t know it`s
analog (BBD - MN3207 & MN3201 - clock)
and
digital (delay - PT2395).

sorry for misleading you, Vseriesamps... 
(http://www.diystompboxes.com/smfforum/index.php?topic=49563.0)

but anyway: in this part of the forum you`ll probably
get more replies.

[vseriesamps]

that's cool, pure. clearly I didn't know either.

To rephrase my original question, then--the delay side of the pedal uses a PT2395 chip. Does anyone know if there is a drop-in replacement that would have a shorter min delay time? are there even drop-in replacements for thesse things? is there some other way to reach my intended goal?

thanks y'all
-k

[Mark Hammer]

The inimitable Ken Stone has a PT2395-based delay project here: http://www.cgs.synth.net/modules/cgs44_ddb.html

You can go directly to the schem here: http://www.cgs.synth.net/modules/pic/schem_cgs44_ddb_ds.gif

What you can see is that the delay time is set by an onboard clock that looks a whole lot like the circuit in the MN3101/3102 and is found associated with pins 24-26.  The delay range (i.e., clock rate) is set by a cap tied to pin 24, and the specific delay time within that range is set by the resistance off pin 25 and 26, with the variable resistance on pin 25.

Ken's schematic shows a 5k pot in series with a 1k fixed resistor.  Generally the way these things work, the fixed resistor sets the minimum delay time (i.e., the fastest possible clock speed), and the various pot values provide clock rates slower than that, hence longer delay times.

All of this says that for small adjustments of delay time on the unit, you should look for the connection between the delay-time pot and pin 25 of the PT2395 chip.  The fixed resistor will either be between the pot and pin 25 or else their order will be reversed and the pot will be tied directly to pin 25 and the fixed resistor linking it to the other resistor from pin 26 and the pin 24 cap.  Depending on what you find there, you can either reduce that fixed resistor by replacing it, or by placing a suitable-value resistor in parallel with it.  For instance, if it was, say, 2k2, you may want to do something like reduce it to 1k9 by placing a 15k resistor in parallel.

For somewhat larger delay-range shifts, you may want to consider changing the cap on pin 24.  This, of course, would depend on what sorts of value differences can be achieved in that cap-value range and the available space.  The cap will almost assuredly be in the pf range.  The datasheet shows 30pf in the application circuit, and Ken's project uses 30pf as well.  You *could* consider changing to a 27pf value or at most a 24pf value.  Note that all the filtering assumes a given delay range, although usually that poses much less of a problem when shortening delay times as opposed to lengthening them.

There have been several PT2399-based delay projects posted here, but nothing yet using the Princeton chips that requires separate DRAM (the 2399 has the DRAM on-board).  So, I think there would likely be much interest in what sorts of cap or resistor changes result in what sorts of delay-time changes.  Please report back.  That is, if you can stop playing!

[vseriesamps]

Thanks Mark!

I'll try to get into this right away. I'm also going to ask a couple of very newbie followup questions.

1) how do I know the pinout on a chip like this?

2) do I have to use one of those anti-static wristband things to work on a unit like this?

I'll definitely report back. I'm actually doing this as part of a larger hack on this pedal, and when I get it dialed in I'll give a full report.

Cheers!
-k

[Mark Hammer]

If you were installing the chip from scratch, you *might* be advised to wear a wristband, but since it is installed and unlikely to be subject to static damage, you main concern is to get in and out fast, and simply avoid heat build-up.

[puretube]

click here for PT2395 datasheet/pinout,
and here for PT2399

(might need a second click on "download"...

[R.G.]

Hey, cool. Since we're into respect...

Would you all not post schematics, mods or other internal reverse engineering information on Visual Sound equipment, please?

[vseriesamps]

Hey RG! I'm sorry, it hadn't occured to me that I was stepping on toes, though it certainly make sense I might have been.

I've actually been in touch with the Visual Sound folks a couple of times about the pedal - albeit briefly  - once to ask for info on how to set it to "wet only" (for which they did in fact provide hack info, even sending over a layout pdf), and then yesterday via IM to ask about this mod. Since they were willing to discuss the idea a little bit (though not offering a solution per se) it hadn't occured to me I shouldn't post. They even said, "let us know if you get this working, Bob'll want to hear it."

If anything, my thought was that if I accomplished what I was after, other people might be interested too, which might actually sell a couple pedals in the long run. If you're like me, you're good enough to change a resistor value or two, but not good enough to reverse engineer a circuit like the H2O circuit, much less build one from scratch. Moreover how many of us have bought TS-9s to mod into TS-808's? Lots. VS refers directly to the TS808 on their website--they've definitely been reverse engineering a few things themselves!

But I understand your concern. Heck maybe you work for them and I was talking to you yesterday.

I'll keep the rest to myself. Suffice it to say that fx-only chorus sounds amazing, and their echo sound, with the dry extracted, is beautiful enough to want to use as your main sound sometimes, an effect all its own (like a crazy lofi eq! soooooo cool), especially if you could *somehow* get the delay time short enough you didn't have a big latency problem that kept you from playing along with your band in time.

It's a terrific pedal--and getting better as I dig into it. Buy one! Everybody!

OK y'all, thanks
-k

[R.G.]

No offense taken.

Actually, I do work for Visual Sound. It wasn't me you were talking to, but it probably was Dave.

One reason I work for Visual Sound is that they - including me! - take their motto, "Real sound for real people", seriously, so there's remarkably little magic fairy dust or granulated carbon mojo used - just good solid circuit boards, quality parts and a real commitment to making it work reliably as well as sound good. So there are not all that many magic secrets in the units, only solid design and production.

But we would prefer to have the same degree of non-exposure accorded to other small makers of pedals.

It is a good point about the latency issue in playing along. I'll get that tossed to the other techies and talked about. I have no illusion that our stuff is so good it just can't be improved. No promises, but it'll get talked about.

[Mark Hammer]

Sometimes, a design makes the parts do its bidding.  Perfect case is is the Fuzz Face or Fuzz Factory.  There, the circuit is comprised of components that are generic, in the sense that they are not made for any specific purpose.  You could yank all those parts out and reconfigure them to do something different.

Other times, a design employs parts whose function is so specific, that there is only one thing you could do with them, and to understand the component is essentially to understand much about the design.  While, like you (and not just because you're a buddy), I am committed to the protective nurturing of smaller-scale manufacturers, by discouraging the posting of schems and such, in this case we have a product whose design is more like the second type than the first.  Had someone posted a query about "How do you change the delay range on a PT2395?", the answer would have been exactly the same.  I would note that changing the delay range on Matsushita delay chips has been discussed at great length on these pages, and such information is readily applicable to both the H2O and a wide array of other equally desirable and used commercial products by large and small manufacturers alike.  In those instances, you can't talk about the properties of the chip and NOT tip the hand of how commercial pedal X "works".  Admittedly, it is a tricky dance to discuss the properties of specialized chips while at the same time not tipping the hand of a commercial design, it IS a dance that is possible to do, and to do responsibly.

Having said that, I would agree with you that the "correct" way to do it is to make an effort to discuss the properties of the devices/chips themselves and not the commercial product they are part of.  I would also emphasize that any mods done do not reflect shortcomings or flaws of the products, merely the reality that if you designed any product to be everything to everybody, the toggles and shipping weight alone would put the price well outside the reach of 95% of the "everybody" you're aiming it at.  EVERY commercial product, no matter how much honest effort and consultation was put into its design, and how much care was put into its construction, will inevitably miss out on the needs of at least one player in one set of circumstances.  Achilles had to be held by something in order to be dipped into the river Styx and be impervious to arrows, and though the back of one ankle may not have seemed like much at the time, it ended up mattering.

This leads to a more generic question, though, which maybe ought to be posted under a separate thread.

[R.G.]

I completely agree - discussions of how to, for instance, shorten the delay time of a PT2395 are completely fair game - as should be the discussion of how to apply TL072s, NPN transistors, what happens when your power supply impedance is too high, filtering and decoupling and so on. No one should be able to quell discusssion of 1M resistors because their Mekkano-Blaster Plasma Distortion has one in there.

Quoting Tom Waits "I'm not weird about it - I don't tie myself up first or nothin'". But as long as we are having certain areas of conversation that are off limits, I'll have some of that too, please. 

As you realize, I have a somewhat quizzical and amused attitude at this.

[vseriesamps]

You know discussions like this interest me sometimes more than the discussions about gear. Thanks for splitting some interesting and relevant hairs--and potentially, threads.

Maybe there should be a separate board for discussion of ethical issues surrounding stompbox design, modification and piracy. These things often pop up as part of other threads--it would be cool if there was a central place where we could all be mulling these things over together.

R.G.--I'd be happy to share the tiny sonic gains I've made with you VSers (via PM/mp3s) when I get back to Brooklyn in a few days, insofar as they might get people over there thinking about the H2O in interesting new ways (I can already smell a lofi filter pedal in the making). And if in fact there was some way to tackle the latency issue and you care to share, I'd be pleased.

Mark--getting very OT, but did you ever spend much time with functionalism and cognitive science? One of the classic puzzles goes something like, If one little piece of my brain was replaced with a microchip, would I still be a human? The answer innvariably comes back Yes. Two pieces?--Uh, sure. Three pieces?--Well, how big are the pieces? Robots aren't humans, after all. Similarly we come to the question of how different a circuit must be before it becomes a new design? I'm sure the law has an answer. But for ethical issues surrounding this board? Tubescreamer/Tube Reamer/Son of Screamer/et al? I think the answer must be more complex, probably similar to the one you give above.

Thanks again everybody.

-k