I found a website that actually had info on Accutronics, MOD, and - er - some other brand Reverb Units (I think these are replacement ones like you might put in a Deluxe Reverb, etc.).

It had number of springs and the decay time on them, as well as the overall decay times (and they could be bought in short, medium, and long decay times).

I have a Line 6 M13 that has models of teh 63 stand alone verb unit, which sounds very good to my ears. Though there's also a model of the kind used in a Twin, I find the 63 model actually can be dialled in to be much closer to my TRRI. Furthermore, my amp's internal verb is so "soaky" even at just barely on (2 on the dial) with a pretty long decay time and pretty "present". It also has some weird over-ring that I find if I'm turning the amp up and playing with any kind of gain - like a nice crunchy rhythm, it sounds, well, bad.

But the 63 Model in the Line 6 doesn't have this over-ring so it actually works great in front of the amp.

It has settings for Tone and Decay, as well as Mix and Pre-delay (or early reflections). Tone and Decay are no problem - I set them to taste.

The Mix is a wet/dry so I set it to taste to.

However, what I've noticed is, to get a Pipeline like sound, I need the pre-delay up around 110 ms and the mix pretty high. Nothing wrong with that - not as drippy as the real thing but as close as this device is going to get (and better sounding than anything else I have).

But I was toying today (as I've also done in the past) in getting it to sound like a "light" verb on my Twin.

Mix is way down - but here's the thing I'm curious about - I feel like to get the same sound as the amp, the pre-delay needs to be around 30ms.

So what I'm wondering is, do old spring reverbs even have any kind of pre-delay (early reflections) with their reverb structure, and if so, is it both measurable and consistent with number on the knob.

IOW, it seems like when I turn up the mix, the pre-delay needs to get longer (though I am trying to emulate the Pipeline sound, not my Twin at that higher setting).

I can use an expression pedal to "scroll" between low mix and 30 ms and high mix and 110 ms, and anything in between! So I could actually do a faux Green Onions where there's verb on the guitar, but there's a lot more during the solo. So I can get any range between a subtle "barely there" verb, up through a 50s style verb, to a more soaky surf verb.

What I'm trying to decide is if the pre-delay is being kind of accurate and it should "follow" the mix depth - longer pre-delay times at greater reverb depth. I know I can just use my ears! But it got me curious about actual tanks and how they work when you turn the knob on them.

My models don't really have a "Dwell" control, so I wonder if Dwell has anything to do with pre-delay, or depth - or what -

FWIW,

Decay is like feedback on a delay - how long it hangs around.
Mix is wet/dry mix - how "present" the reverb effect is (or how lost the dry sound becomes in it!).
Pre-delay actually seems to have a very subtle effect, but interactive with the mix.

So when you turn up a single knob verb on a Twin - is it "dwell" "Mix" "decay time", or some fixed combination of all of them.

I know the 63 stand alone they're modelling has Tone and Mixer, which are probably 1:1 with my parameters. But it has "dwell" as well - so is that decay, pre-delay, or some combination thereof?

Bagder wrote:

On a combo amp, the single control is going to determine how much of the signal is siphoned off to the pan, so it's most easily likened to a dwell. The mixer circuit is fixed, ergo, no mix knob (reverb recovery circuit in a combo amp).

Are you sure about this? I always thought it was the other way round: Fixed dwell and variable mix. Hint: When you turn the reverb down on an amp and shake the whole thing you will not hear the springs rattle as you would, when the mix would alsways be open...

That it seems to require a bit more delay with higher settings to get the same perceived drip is totally understandable. At 110ms you're well into slap territory, something which is often used to enhance the perception of drip.

I think you and the OP are talking about different things here. From my understanding a pre-delay is not a delay/echo in front of the reverb but basically a setting that let's you delay the moment in which the reverb starts. Meaning: in natural reverb (as from big rooms) it takes some time for the orginal sound wave to hit the wall and then come back in diffused form as reverb. This time is the pre-delay.

Increasing the pre-delay gives a more "direct" sound even with a higher mix, since there is some time between the plug of the string and the onset of the reverb.

BUT on a spring reverb the pre-delay normaly is very short and not variable: it is the fixed time it takes to transform the electrical signal from the guitar into the mechanical movement of the strings and back to electrical signal.

The Dwell control on a reverb basically controls the volume of the input signal, which affects both the volume of the reverberated signal and the decay time, which both again are in the end affected a second time by the mix control. So Dwell and Mix both have to be considered together.

For surf sounds I would try to keep the pre-delay down to a minimum. For higher mix settings turn down the decay time a bit and vice versa.

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Last edited: Jan 23, 2016 07:10:02

Thanks to both of you - this clears up things a bit for me.

On this particular reverb model, I suppose what I'm calling "pre-delay" is really an "early reflection". The parameter doesn't say anything, and nor does the model gallery (it may be buried elsewhere in literature) aside from having a ms value. Unlike delays, it doesn't have as wide a range - I think it goes from 0-200ms.

So in other words, there is reverberated signal instantaneously, no matter what I do - I can't delay the onset of the first reveberated echo for example. And that's OK.

Listening closely to my TRRI's onboard verb, there is a noticeable "repeat" like a typical echo - it's subtle, and "swamped" in reverb, but there's a throbbing or pulsing, or, well, echo buried in there.

The Line 6 model does the same thing (so pretty accurate!) but moving the ms parameter doesn't change that rate - so like the real one, turning up the "reverb" knob is like turning up the "mix" control on the model.

On the TRRI, high settings are pretty much ridiculous - I mean, the difference between 1.5 and 2.5 is pretty extreme, and above 2.5 is surf to silly only territory. I have played with different tubes by the way and achieved more useful range on the reverb knob, but the overall tone suffered so I just keep it "stock".

And I think the part of the issue is that when you turn up the Reverb knob, you do in fact not only get more Mix but more Decay (or let's say that, the decay seems longer becuase the previously quiet tail is much louder and audible for a longer time).

So the advantage to the model is being able to control the Decay time - you can make the Mix higher but keep the overall Decay time the same if you wanted.

So this one other parameter, like I said, seems like an "early reflection" though at lower values it's pretty much "a part of" the reverberation. It's not until you get up into maybe the 90s+ that you seem to get more noticeable "slapback" (it's not that noticeable, but it does affect the overall "character" of the verb).

What's interesting is that this natural "echo" (throbbing or pulse I was referring to earlier) has got to be a specific time - and it may be the reason that when I set this "pre-delay" or "early reflections" or whatever it is to 110ms, I get a more pronounced "drip" (or something) maybe because those to elements are lining up. Throb at 110 and Early Reflection at 110. I suppose.

I guess I wish I knew what that throb in the stock echo is so I could match the ms setting to it (or half, or double it, etc.).

Just revisiting this thread because I actually just revisited the Amplified Parts site where I found the Accutronics info initially.

Actually, it appears there are 2 or 3 different springs in the reverb unit with times of 33 and 41 or 33, 37, and 41 ms to produce "overlap" to get you reverb as opposed to just straight echo.

But that is in fact listed as the "Delay Time" - which I was calling "early reflections" and "pre-delay" initially.