Behringer VD400 analog delay - trimpot adjust and it's awesome!

[ghostsauce]

After getting a chance to really crank the amp with this delay, I've noticed a small amount of unwanted frequency resounding in the delays... but I was able to tweak it out using the upper-right trimpot. And in the pedal's defence I may have very well caused it because I had been tweaking that trimpot, hehe.. Sounds great now though. I wish the delay time were a little longer, but I am loving this thing for the price. Will definitely be buying a second one down the road for my JCM900 rig! Using this one on my Class 5 after my Dr Boogey and before the SHO.

[Mark Hammer]

Mark, that remote switching is so frickin' cool! Frig, you could build a board that had all the pedals in a little box hidden from view, and just a big switchboard on top for the ultra clean look! Or just have a small switchboard out front and run a 15-pin midi cable back to a flight case with your pedals inside! That's really quite an interesting idea

Yep.  I don't know why Boss hasn't been making their pedals with the damn jack pre-installed all along.  That way they could work in stand-alone fashion, or be controlled by a Boss-made switching station.

[ghostsauce]

No kidding.. There must be a market for this stuff... and if they slap the Boss name on it they can't go wrong. People go nuts for Boss stuff.

[scuzzphut]

There is a "swell" (SWL) mode on both the EP and EM600.  Set the mix to all wet, the delay time short, and zero repeats, and you have a digital Slow Gear with much more reliable triggering.

Never tried that before. Sounds brilliant and you're right - the tracking is good.   

Thanks Mark !

[paulyy]

Just got the VD400 and EM600 and both sound really good for being so cheap. First off the EM600 is great but the tap tempo could be better. The VD400 at first didnt really impress me. I found that the repeats were to dirty for me but I did do some tweaking with the trim pot and was able to clean it up alittle. I also replaced the 3102 opamp with a socket and tryed a few other 3102 opamps I had laying around. I had three laying around and all of them were different brands. Once I found one that worked well, The repeats came in cleaner and warmer. Now it sounds really good. All in all, Im pleased with these pedals. They work really well and they dont seem to suck any tone. I think I'll get the DD600 in a few weeks. Despit some of the cheap parts. Great bang for your buck.

[Seven64]

i picked up the behringer slow motion (slow gear) for $22 shipped and the space c (dimension c) for about $25 shipped.  both were terrible, but with some trimpot tweaking, they both now are awesome!

[bolero]

 zombie thread, but I picked one of these up & am getting an ugly distorted/sharp high pitched noise, only on the beginning/attack of the delay, that sounds terrible. it's a very short sound but when doubling with what you are playing it's nasty

I wonder if it's due to the cheap op amps, or maybe it needs a lowpass EQ? has anyone run into this?

thx!

[Mark Hammer]

First, welcome.  Let's hope your first post leads to the resolution of a problem.

Second, does "one of these" refer to the Behringer VD400 or to one of the other pedals mentioned by others here?

[bolero]

 hey! how are you doing?

it is indeed a Behringer vd400

the annoying sound seems only present on the initial attack of the first delay

I think maybe it needs a cap somewhere, is it true the circuit is the same as a Boss DM3?

thanks!

[Mark Hammer]

Doin' fine, thanks.  I wasn't sure if it was you or someone simply using the same handle. (we know each other from another forum)

The chances are pretty good that it is simply a clone of the DM-3.  It has the same delay range, indicating use of a single 4096-stage device.  And since Behringer gets its delay chips from Coolaudio, that points to a V3205 ( https://www.coolaudio.com/features-page.php?product=V3205SD )

I'm trying to think through this one.  Is the annoying sound produced on the first repeat no matter what the input signal level is? Or is it a side-effect of picking harder?

Is it correlated with how the feedback level is set?

Here's a YT about how to extend the delay time.

[bolero]

let me test that out & get back to you!

I was also considering it may be distortion from the opamp, but that fellow above never mentioned which opamp he switched to, unfortunately

I had to drop the mix level quite a bit to try & hide it, but obviously then you are losing volune of the effect.

One thing I like about this pedal is it has a wet out. so you could probably use 2 of them in series to get longer echoes

thanks!

[bolero]

hmm I wonder if it's just clock noise...it does continue past the initial note after all, but only during the signal. I thought clock noise/whine happened whether there was signal or not?

also playing hard doesn't seem to affect the noise, it's constant

I recorded an mp3 clip but can't find an attachment option here. maybe I need more posts

try to download this mp3, or maybe it will  play direct: it's only 908 kb

el34.coolpage.biz/clips/vd400.mp3

[bolero]

actually, after reading this I wonder if I need to do the same?

https://www.diystompboxes.com/smfforum/index.php?topic=125234.0

I found the DM2 service manual on archive.org

link:

https://ia801909.us.archive.org/26/items/boss_dm2-sm/boss_dm2-sm_text.pdf

[j_flanders]

hmm I wonder if it's just clock noise...

Yes, your mp3 is a great example of clock noise.
The clock frequency is (set) too low, maybe to get longer delay times, with the disadvantage that the clock freq becomes audible.

Things you can do:
Externally:
-turn the delay knob to a lower setting for a shorter delay time (= higher clock frequency).

Internally:
-If there's a balancing trimpot at the output of the bbd chip, tweaking it towards a more 50/50 setting can somewhat help but I find it has to be really off before you hear the clocknoise.

-If there's a biasing trimpot for the bbd you can tweak that for a better bias, cleaner output of the bbd, which results in less hamonics, less intermodulation with the clock signal. This prevents the harmonics to come down into the audible range and hearing it along with the actual audio signal.

-Put the time cap on the clock circuit back to stock values. Sometimes people mod these to get a slower clock freq (slower clock = longer delay) and they just put up with the clock noise when they set the delay time knob at the highest settings

[Mark Hammer]

flanders' advice is spot on.  Follow it.

[bolero]

thanks, both!!

[bolero]

 hmm it doesn't go away if I adjust the left trim pot inside, lessening the delay time

I managed to get a constant high pitched whine ( what I previously thought was clock noise ) if I adjusted the right trim pot, but could dial it back out again

not sure what the middle trim pot does, it killed the delay completely if I dialed it left

I am sort of inclined to think this is caused by a substandard op-amp distorting? that gets muted gradually as it moves down the brigade?

*edit* signal chain is strat-->VD400--->amp so it shouldn't be getting overloaded

[Fancy Lime]

hmm it doesn't go away if I adjust the left trim pot inside, lessening the delay time

I managed to get a constant high pitched whine ( what I previously thought was clock noise ) if I adjusted the right trim pot, but could dial it back out again

not sure what the middle trim pot does, it killed the delay completely if I dialed it left

I am sort of inclined to think this is caused by a substandard op-amp distorting? that gets muted gradually as it moves down the brigade?

*edit* signal chain is strat-->VD400--->amp so it shouldn't be getting overloaded

Sounds like the right trimmer is the Cancellation control. This balances between the two outputs of the BBD that are offset by one extra stage, thus cancelling the clock frequency when balanced correctly. So yes, the whine is the clock. The middle trimmer is the BBD bias. Have you tried fine adjusting that to see if the problem goes away? To me, what you describe sounds like a BBD bias problem. Biasing a BBD right can be a bit finicky and might take some patience, especially since those trimmers Behringer uses are not exactly the gold standard of precision trimpots.

Cheers,
Andy

[j_flanders]

el34.coolpage.biz/clips/vd400.mp3

I imported the mp3 into Audacity and measured the interval between the dry signal and the repeat.
It measures 404ms.
That's too long for a single V3205 bbd chip.
Usually that's the kind of maximum delay you see in pedals with two 3x05 or four 3x08 chips like in the EHX Memory Toy, Boy, Man and lots of other pedals.
In order to get to that amount of delay you must really slow down the clock a lot which results in severe clock noise at those longer delay times.
You'd need such heavy filtering to eliminate the clock noise that there would be little left of the dry signal as well.

I watched  a youtube video about the VD400 delay time mod.
Apparently (and contrary to my previously suggested fix) they don't change the timing cap in the clock circuit but the resistor. The combination of both set the clock frequency, and thus the delay time.

To give the user control over the delay time the setup of the clock frequency is usually:
cap + fixed resistor + variable resistor (the last one is the delay knob on the outside of the pedal)
In the Behringer they put a trimpot instead of the fixed resistor.
Increasing the resistance of that trimpot increases the maximum delay time, but it also increases the minimum delay time.

Turn that trimpot (at the left) back to its original position or until you reach a maximum delay time where you don't find the clock noise objectionable.

hmm it doesn't go away if I adjust the left trim pot inside, lessening the delay time

It should, unless the bias (trimpot at the right) is off.

[Mark Hammer]

It's actually NOT too long for a single 4096-stage BBD.  However, it IS too long for a 4096-stage BBD whose anti-alias and lowpass filtering is calculated in anticipation of only being asked to delay for somewhat less than 400msec.  You sort of say that in an indirect way.

Analog delay design is always a matter of starting out with what sort of bandwidth you're aiming for, THEN how much delay you want, and THEN figuring out how to achieve that.  If you want 500ms of delay AND you want 6khz bandwidth, then you're gonna probably need at least 3 MN3205s, and figure out some way to pump the clock to all three at once.

Mike Irwin once demonstrated a single MN3005 delay to me, set for something like a full second of delay.  The bandwidth was seriously limited. By the 3rd or 4th repeat, the input signal was virtually unrecognizable.  But it was there, one second later.  More of a "wonder if" experiment than anything useful, but the point was made.