Whats the difference between Analog & Digital delay?

[Blues Junior]

I know probably a stupid question to most of you. I've only played through a BOSS DD-3 for a few years now, and it's served me pretty good no complaints. But that's all i know. I asked a guy at my local shop, and he says analog is warmer. That's it. So is that it? Analog is warmer sounding? Got to more to it right? What's this modulation thing?

 

Any of you in the know care to answer? I'm asking because i see this MXR Carbon Copy that's at a good price, and thinking i'd like to try it. And now BOSS has a new DD-7 which is like a swiss army knife delay. Thanks for chiming in.

[Agreed]

Digital delay is crisp and clean, analog delay is warm and somewhat distorted. Digital delays can be quite long and retain signal fidelity, while analog delays can't be very long, and when they are longer than 300-500ms, they get really raunchy really quick.

 

Some digital delays make a good effort of simulating analog delays, and some analog delays are much cleaner than the norm, but that's the general flavor.

[mlabbee]

Analog delays usually refers to a delay that uses a bucket brigade delay (BBD) chip to record the signal and play it back. Those chips use a relatively low frequency clock which happens to land in the audio range (in the high end of the guitar signal). So the designers added in a low pass filter to cut the clock noise - so repeats have the top end shved off and tend to get darker the more repeats - hence, the warmer sound. You can get the same effect in a digital delay by adding in the filter - many simulated analog delays (like the Keely DD-3 hi cut mod) do exactly this.

 

Other forms of analog delay include tape delays or echo units. In these, the repeats (playback of the tape) could suffer tape-realted issues like wow and flutter - also known as modulation. It just so happens these "limitations" of the medium sound good, so people tack those on to delays, as well. Add in tube distortion from older vacuum tube based systems and you've got most of the add ons that make delays sound "warm" or "analog".

[amp_surgeon]

Oooh! Oooh! Teacher, pick me!

 

I've been waiting for this topic to come up!

 

mlabbee is precisely right. Tape units aside, most of the solid state delays which people refer to as "analog" are based on bucket brigade devices. In the strictest sense, these are neither analog nor digital, but a hybrid of the two.

 

A fully digital delay samples and digitizes the incoming sound. The delay effect is accomplished by recording the digital numbers into a memory, and then reading them back out after some period of time and mixing them with the outgoing data stream to form the "wet" mix. The amount of delay you can get is generally limited by the sample rate and the amount of memory.

 

A bucket brigade device is very similar to the fully digital delay in concept. It still samples the incoming sound. However, instead of converting each sample into a digital number, the signal voltage is stored as a charge on a tiny capacitor in the BBD chip. When the next sample clock occurs, the charge is passed to the next capacitor in the chain, and all of the samples ripple down through the chain, the same way that a real bucket brigade passes buckets of water down the chain to put out a fire.

 

A BBD chip is kind of like a game of "telephone". The sample voltage changes a little every time it gets passed from one stage to the next, for all of the same reasons any voltage in an analog circuit can get distorted.

 

BBD chips usually have a number of taps where the voltage samples can be picked out of the chain and mixed back into the outgoing sound. These establish ranges of delay time. To get continously variable delays within these ranges, you have to adjust the sample clock frequency.

 

BBD's quantize the signal into a series of values, each representing a specific point in time, just like a fully digital delay circuit. What makes them significantly different from a fully digital circuit is that these values are stored as analog voltages rather than digital numbers. From an engineering standpoint, BBD's are analog in the amplitude axis, but digital in the time axis. Tape delays, on the other hand, are analog in both axes.

 

Can I have my gold star now?

[Agreed]

This is a real accomplishment in HCF history, a question answered in complete thoroughness in a mere three posts (although honestly, mine shouldn't count, as it was a user-friendly gloss on their excellent, precise explanations).

 

A proud day.

[echodeluxe]

wow.

[Clorox]

I have a somewhat related question. Why is it almost impossible to get an analog delay with more than 600 or 800ms? I know the toneczar and the moog each have about 1 second, but why are they the only ones and why does the longer time warrant $700+ prices? Is it really that much harder to had those few hundred milliseconds?

[amp_surgeon]

 

I have a somewhat related question. Why is it almost impossible to get an analog delay with more than 600 or 800ms? I know the toneczar and the moog each have about 1 second, but why are they the only ones and why does the longer time warrant $700+ prices? Is it really that much harder to had those few hundred milliseconds?

 

 

They discontinued the original MF-104 because they ran out of BBD's, and nobody was making them anymore. The MF-104Z is expensive because it uses NOS Panasonic BBD's, which will eventually run out as well.

 

You can still find NOS BBD's, like the Reticon SAD-1024, but they are expensive, at around $30 a pop. Getting more than a second of delay time would require at least 3 of them. They're a bit cheaper in quantity, but not much because of their scarcity. I can see why it would cost $700 for a pedal if they have to spend $90 just for the BBD's.

[Blues Junior]

Yes, thanks all of you for answering quickly and without any of the usual BS. Amp surgeon great explanation. I'm impressed!

[mike.sartori]

It should be noted that several analog delays (and most multi-function digitals) also have a different type of modulation from tape flutter, on pedals like a DMM, carbon copy, or memory lane, the modulation is like a chorus/vibrato on the repeats.

[Ben Co.]

 

Analog delays usually refers to a delay that uses a bucket brigade delay (BBD) chip to record the signal and play it back. Those chips use a relatively low frequency clock which happens to land in the audio range (in the high end of the guitar signal). So the designers added in a low pass filter to cut the clock noise - so repeats have the top end shved off and tend to get darker the more repeats - hence, the warmer sound. You can get the same effect in a digital delay by adding in the filter - many simulated analog delays (like the Keely DD-3 hi cut mod) do exactly this.

 

The Hi-Cut mods out there don't exactly do the same thing in that they shave a little off the high end of the wet repeats equally and non-progressively. All the repeats following the dry input will have the exact same amount of high end shaved off.

 

With analog or an analog sim, each subsequent repeat gets darker and less defined than the preceding one.

 

So I never thought of the Hi-Cut as being an analog sim... more like a tone control for a digital delay.

[Uma Floresta]

I know probably a stupid question to most of you. I've only played through a BOSS DD-3 for a few years now, and it's served me pretty good no complaints. But that's all i know. I asked a guy at my local shop, and he says analog is warmer. That's it. So is that it? Analog is warmer sounding? Got to more to it right? What's this modulation thing? Any of you in the know care to answer? I'm asking because i see this MXR Carbon Copy that's at a good price, and thinking i'd like to try it. And now BOSS has a new DD-7 which is like a swiss army knife delay. Thanks for chiming in.

 

Sort of, but digital can be every bit as warm - it just depends on how the repeats are filtered. Also, digital emulations of analog and tape delay can be quite good.

[melx]

I love the 'filter' knob on the Hazarai, it's great.

[ambys]

Oooh! Oooh! Teacher, pick me! I've been waiting for this topic to come up! mlabbee is precisely right. Tape units aside, most of the solid state delays which people refer to as "analog" are based on bucket brigade devices. In the strictest sense, these are neither analog nor digital, but a hybrid of the two. A fully digital delay samples and digitizes the incoming sound. The delay effect is accomplished by recording the digital numbers into a memory, and then reading them back out after some period of time and mixing them with the outgoing data stream to form the "wet" mix. The amount of delay you can get is generally limited by the sample rate and the amount of memory. A bucket brigade device is very similar to the fully digital delay in concept. It still samples the incoming sound. However, instead of converting each sample into a digital number, the signal voltage is stored as a charge on a tiny capacitor in the BBD chip. When the next sample clock occurs, the charge is passed to the next capacitor in the chain, and all of the samples ripple down through the chain, the same way that a real bucket brigade passes buckets of water down the chain to put out a fire. A BBD chip is kind of like a game of "telephone". The sample voltage changes a little every time it gets passed from one stage to the next, for all of the same reasons any voltage in an analog circuit can get distorted. BBD chips usually have a number of taps where the voltage samples can be picked out of the chain and mixed back into the outgoing sound. These establish ranges of delay time. To get continously variable delays within these ranges, you have to adjust the sample clock frequency. BBD's quantize the signal into a series of values, each representing a specific point in time, just like a fully digital delay circuit. What makes them significantly different from a fully digital circuit is that these values are stored as analog voltages rather than digital numbers. From an engineering standpoint, BBD's are analog in the amplitude axis, but digital in the time axis. Tape delays, on the other hand, are analog in both axes. Can I have my gold star now?

 

First off, awesome post.

 

I'm curious--so on an analog delay when you adjust the delay time, is that basically just adjusting the sample rate at which the analog values are stored in the capacitors? And is that why they start to sound muddy when you make the delay time too long (because the sample rate is so low)?

[mlabbee]

 

I have a somewhat related question. Why is it almost impossible to get an analog delay with more than 600 or 800ms? I know the toneczar and the moog each have about 1 second, but why are they the only ones and why does the longer time warrant $700+ prices? Is it really that much harder to had those few hundred milliseconds?

 

 

As Amp Surgeon noted (great explanation, BTW - thanks!), BBDs work by passing the information from one stage to the next. So to get longer delay times, you need more stages. I'm guessing the old BBDs were expensive to make and there was a practical limit on the number of stages they could build at the time (also, the game of "telephone" AS described would probably limit the delay time just based in signal fidelity). Remember when RAM was really expensive in the 80's? E.g., the original DD-3 was a straight relabeling of the DD-2 - there was a big drop in DRAM prices that allowed them to make it cheaper, but they didn't want DD-2 owners to feel like they had gotten screwed! Silicon is really cheap today, but at the time analog delays were in their prime, these kinds of chips were hard to make and pricey.

 

I'm guessing they could probably build BBDs much larger and cheaper today, but there's really nomarket for them other than delay units, so probably not enough demand to justify the design costs.

 

As for the high cost of the boutique delays you mentioned, I think you can chain together a couple of BBDs to get longer delays, but the circuitry to make it work right is complex/tricky (I recall reading something about this one) - hence the cost.

[mlabbee]

 

It should be noted that several analog delays (and most multi-function digitals) also have a different type of modulation from tape flutter, on pedals like a DMM, carbon copy, or memory lane, the modulation is like a chorus/vibrato on the repeats.

 

 

Actually, chorus/vibrato are pretty similar to one of the kinds of modulations you get from tape (in fact, flanging, which is just a chorus with a shorter delay, was invented by pressing on the flange of a tape unit to modulate the tape speed . . . ). Chorus and Flange are both very short delays with a little modulation of delay time. Vibrato is a slight modulation in pitch, which can be created by delaying a signal slightly then speeding and slowing it to vary the pitch. A lot of Vibratos are just chorus units with no dry signal mixed in.

 

One of the natural modulation effects of a tape unit it a slight variation in tape speed arising from slippage of rollers, imperfect motors, etc. (one of the reason tape units were so expensive is all the money they threw into motors to get them to work very smoothly) - that variation in tape speed varies the pitch just like a flanger/chorus/vibrato.

[Agreed]

Actually, chorus/vibrato are pretty similar to one of the kinds of modulations you get from tape (in fact, flanging, which is just a chorus with a shorter delay, was invented by pressing on the flange of a tape unit to modulate the tape speed . . . ). Chorus and Flange are both very short delays with a little modulation of delay time. Vibrato is a slight modulation in pitch, which can be created by delaying a signal slightly then speeding and slowing it to vary the pitch. A lot of Vibratos are just chorus units with no dry signal mixed in. One of the natural modulation effects of a tape unit it a slight variation in tape speed arising from slippage of rollers, imperfect motors, etc. (one of the reason tape units were so expensive is all the money they threw into motors to get them to work very smoothly) - that variation in tape speed varies the pitch just like a flanger/chorus/vibrato.

 

I can get a great vibrato with my Danelectro Wasabi Chorus/Trem. It allows a 100% wet mix, and high speed and depth with fully wet =