Demystifying… Analog Dry-Through

Analog Dry-Through

...The new favorite feature of guitar players?

Context

In a previous post we covered True Bypass and its alternatives - The feature that tells us what happens to our signal when a pedal is off.

What about what happens to our signal when the pedal is ON?

Seems like the most important question, but interestingly the less discussed. Probably because you either like what the pedal does or you don't and in that case you don't buy it or use it at all.

Definition

Dry-through is the ability of a pedal to give us the signal unaffected by its effect at the output. This usually comes in the format of a Mix knob, giving us the option of choosing how much of the "effect" signal.

Analog dry-through is the same concept, but being more specific, assuring that your analog signal, just like it is seen on the input of the pedal, is sent without digital converting/processing of any kind to the output, with it's proportion to the processed signal also controlled by a mix knob in most cases.

Applications

On analog pedals, if dry-through is available, it is by definition an analog dry-through.
This can be found in some effects like analog delays, modulations, and even in overdrives (although not so common).

In the realm of digital processing effects pedals, this is when it gets interesting.
Most offer dry-through to allow the mixing of the amount of processed effect into the dry signal. In the digital domain this is easy and cheap, it's just programmed into the DSP.
For a digital effect pedal to offer analog dry-through, the investment is higher in terms of componentes, and this is where you start to get some distinction in quality and price.

Many high end digital products offer analog dry-through, and present themselves as pedals that offer you a perfect natural sound, without any latency, surrounded by the effect you want dial in. (example: Strymon pedals)

That said, this does not mean that all high end product have analog dry-through. Some might just focus everything in the processed sound and have that as their selling point. (example: Eventide pedals) So it depends on the intention, and on how it is used.

And also some low to mid priced pedals can offer this feature. (example: TC Electronic pedals)

So where does this leave us?

Some technical details and why they are important

In digital pedals, the analog dry-through is achieved by the means of using a buffered splitter before anything else and a mixer ate the end, leaving us two distinct paths of analog signal.

One of the paths will be our unaffected analog dry-through, the other one will be interrupted by a set of A/D and D/A converters with the effect processing in the middle.
(A/D being the Analog-to-Digital converter, that samples the signal to make it available to the digital domain, and D/A the Digital-to-Analog converter that brings back the processed signal to analog again)

Why is this important to know?

First, there are better and worse quality components, and this applies to both Buffers and A/D and D/A converters. So, you can have all kinds of quality disparity depending on the components. And this means that an analog dry-through pedal will not guarantee pristine sound quality unless it has good components.

In the two extremes, a "bad" buffer can color your signal undesirably and a "good" A/D-D/A can produce a very good representation of your dry signal. So everything is in play, just beware of the concepts when used for advertising.

Second, and maybe the most important aspect of A/D-D/A conversion, is latency.
I will now dwell into deeper technical details, if you want to skip it and just go to the conclusion and practical impacts, jump to the next chapter.

Things get better and better everyday in the signal conversion and processing domains, but the science behind it always relies in the same principles. Let me try to put it in a way that anyone can understand the ideia, even without engineering knowledge.

We can summarize the digital signal processing flow by identifying the main players:

• An internal clock
• The A/D converter
• The Effect Processing Unit
• The D/A converter

The internal clock commands the whole digital operation. He is the boss, and only when he gives the order, the workers can take action.

• For each clock tick, the A/D samples your sound.
• Only in the next clock tick, the Effect Unit will have the sample available to process and processing itself takes several clock ticks. And the more complex the algorithm is, the more samples it needs to calculates what the effect is doing, resulting in more clock ticks used
• In the end, after the effect unit finishes its thing, another clock tick will trigger the D/A to give back the signal already with the effect.

Just by this lame description, you can see that several clock ticks can be spent between what you do in the guitar and what comes out of the pedal. Clock ticks equal time.

Of course this is describing the whole processing time. To be fair, we are talking in this article about the dry signal, so if it is a digital dry-through, it will at least pass through the A/D and the D/A best case, and the clock ticks spent here represente the latency of the dry signal.

Bla bla Latency, so what?

Well, when things are not obvious, it generates controversy. If a pedal would have a 5 seconds latency, everybody would complain. But since we're talking about milliseconds it's not about what you detect or measure on your ear, it becomes more about what you feel in the sound response when you are playing.

If you always played guitar in the digital domain, with any half decent modeler, chances are you never felt that latency or that disconnection with the sound, because it's what you know and it always felt right.

If you started or became used to play with an analog Amplifier (valve or solid-state), you may feel the difference. And if you notice it, it may just turn you off by making you feel disconnected with the sound. There is a directness in using real amp that makes you play and feel different.

I started playing in the digital domain and got used to it, so I can feel inspired and play with a good modeler. That said, for me nothing beats the feeling of the amp. So I end up using both because I cannot have endless amplifiers and it's nice to get the sound of different things from time to time.

And I know i started talking about effects pedals and ended talking about amp modelers, without any explanation, but it was meant to make the message more obvious by more relatable experiences.

But the latency issue is not just about this. There are other possible impacts to consider.

Parallel effects, wet-dry setups and so on...

When you setup any kind of parallel signal path, either by using a parallel mixer, or a parallel effects loop or a multiple amp setup with only part of the effects going into one the amps, the latency issue is likely to become more obvious. You will have multiple sound sources sending sound to you and if one of them gets delayed by latency, you will notice it or at least feel that it sounds weird.

Under these parallel signal path scenarios, you can still overcome this issue if your fully digital pedal allows you to configure it in "kill-dry", which will not bring out the dry signal up front, just giving you the nice effect layer, and then you will get your dry signal from the other parallel source.

In fact, in the old days of rack effects that were largely used during the 80's and even 90's, these rack units were purely digital, without any analog dry-through and the bands were playing and recording using exactly this technique of mixed parallel dry + effect only (kill dry) sounds.

Conclusion

With the current state of the art, for me it's a great bonus to have analog dry-through. It brings the feeling and the sound to a level of reality and fidelity that rarely fully digital pedal can achieve. Some pedals are meant to just go crazy on the effects, totally replacing the original signal, and this is fine, it's just a different use, or you can get a parallel loop for this. But if your pedal has analog dry-through and also has the abilty to set it kill-dry, or mix the full effect signal to 100% ratio, you will have all the possibilities in your hand.

The technology will get to the point that we can't even feel that latency, since it will become smaller and smaller. But until then...

Final notes

I could not find any specific video that would specifically cover and give practical examples for this topic, but if you check out the TPS videos you will definitely get great examples as they mention these aspects several times in their videos. Have fun!!