Hey, I want to build a rackmount multieffect unit, and mount the jacks, footswitches, and pots to the front of a 19" rack chassis. My question is how can I use pedal pcbs in my effect unit? I want to send line level signals to/from a mixer to the effect unit, but I'm not sure if pedal circuits can accept a line level. Could I modify the pedal circuits to run at line level? Do I need to add a reamp box and di box circuits into the effect unit? Any other ideas?
Should have no problems. Pedals are designed for versatility in use: low voltage outputs from vintage pickups, high voltage outputs from custom pickups, being daisy chained sequentially, placed in an amps effects loop, etc.
I have to say I don't get the "why" of your project. Are you talking about gutting the PCB's from commercial pedals? Why go to that bother plus destruction of resale value? Are you talking about buying a bunch of bare clone PCB's? Why not go multi-effects instead?
I have to say I don't get the "why" of your project. Are you talking about gutting the PCB's from commercial pedals? Why go to that bother plus destruction of resale value? Are you talking about buying a bunch of bare clone PCB's? Why not go multi-effects instead?
I meant buying pcbs from sites like pedalpcb.com and populating them with my own components, maybe designing my own effect circuit and using stripboard to put in the effect unit.
Well, to each his own, but doesn't sound like a good idea to me. You are probably going to start with a small number, build it, then what? Suppose you want to add or replace an effect? You've go to go without a functioning rig while you take apart your box, mount a new PCB, drill and mount new pots. What happens when you run out of room for pots? Or you replace a PCB with a new one that has fewer pots?
Hi,
Line level into guitar fx... it kinda work as is but... pro line level ( +4dbu) is 30/40db louder than a 'typical' guitar output.
So if you want a bit of lattitude to introduce distortion or other effects then a 30/40db attenuator will be needed to drive your pedals ( maybe with variable attenuation in 10db steps?).
And of course you'll need a /3040db preamp to bring the signal at the output of your fx rack back to +4dbu.
Input Z is not an issue with pedal gear ( usually) but it can be an issue on the out. The 'preamp' will help in this too ( it need high input impedance).
If it can perform single ended to balanced conversion too it might help too if you use pro gear ( most are balanced).
So to sum it up:
Attenuation of 40db ( pad or pad+buffer if you are concerned about impedance) and 'make up gain stage' ( high z input/ 40db gain).
If you look for 'attitude' fx then implement a variable attenuator on the pad it'll give you opportunity to use modular synth module within your chain.
Line level into guitar fx... it kinda work as is but... pro line level ( +4dbu) is 30/40db louder than a 'typical' guitar output.
So if you want a bit of lattitude to introduce distortion or other effects then a 30/40db attenuator will be needed to drive your pedals ( maybe with variable attenuation in 10db steps?).
And of course you'll need a /3040db preamp to bring the signal at the output of your fx rack back to +4dbu.
Input Z is not an issue with pedal gear ( usually) but it can be an issue on the out. The 'preamp' will help in this too ( it need high input impedance).
If it can perform single ended to balanced conversion too it might help too if you use pro gear ( most are balanced).
So to sum it up:
Attenuation of 40db ( pad or pad+buffer if you are concerned about impedance) and 'make up gain stage' ( high z input/ 40db gain).
If you look for 'attitude' fx then implement a variable attenuator on the pad it'll give you opportunity to use modular synth module within your chain.
Here is a circuit to interface stomp gear with modular synth:
https://sdiy.info/wiki/CGS_stomp_box_adapter
To adapt it to pro line level you'll need a bit more attenuation and gain: modular synth standard is 10v peak/peak so around 12/13dbu ( ~3,5V rms). Pro gear is +21/24dbu around 10 db more so you'll need to adapt to something in this range.
The attenuator part of the circuit is passive, there is no active buffer to gives a low output Z to drive the chain ( it is not really needed with guitar gear however). To implement one is easy: an opamp in voltage follower and voila! ( you tie negative input to opamp output, input by positive terminal).
@488 Studios, which kind of effects do you plan to use?
https://sdiy.info/wiki/CGS_stomp_box_adapter
To adapt it to pro line level you'll need a bit more attenuation and gain: modular synth standard is 10v peak/peak so around 12/13dbu ( ~3,5V rms). Pro gear is +21/24dbu around 10 db more so you'll need to adapt to something in this range.
The attenuator part of the circuit is passive, there is no active buffer to gives a low output Z to drive the chain ( it is not really needed with guitar gear however). To implement one is easy: an opamp in voltage follower and voila! ( you tie negative input to opamp output, input by positive terminal).
@488 Studios, which kind of effects do you plan to use?
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@krivium I'll probably use a bucket brigade delay, distortion, flanger, maybe a tremolo. And I think my tascam 488 mkii is consumer line level, not pro line level. How many dB's between pedal and consumer line level? also, how do i learn to make those circuits you just mentioned(pad, buffer, attenuator, make-up gain stage, voltage follower)?
Hi,
Ok the effects you wanna play with are the kind which are worth the hassle: analog modulation effects ( phaser/flanger/chorus... as well as delay) have a 'special' sound to them compared to their digital equivalent. Disto... nothing like an stompbox in my view too.
The levels: you are right that your Tascam ( https://homerecording.com/tas488specs.html ) is -10dbV referenced ( 'consumer' level).
Pro level is +4dbU referenced ( did you spot the difference between both db unit? U/V means different things about the reference point).
So we will have to translate dbV to dbU to be able to compare things between them.
Here you'll find more info about those differences as well as the expected voltage reading for different levels you could encounter:
https://www.sowter.co.uk/decibels.php
So from there we know that 'dbV is not related to any impedance ( like dbU) but is relative/referenced to 1Volt).
So we will take a look at 1Volt voltage and at which level it translate to dbU: it is in between +2 and +3 dbU, so let's take +2dbu for sake of simplicity.
Iow it means that +2dbu= 0dbV and the reference point is -10db below this level. So in the vicinity of -8dbU (= 0.304 Volt rms).
If you have read the Tascam specification's link it should remain some numbers which were given.
Ok so what next from here? We have 'translated' dbV to dbU so from now it's a matter of finding the difference between both in db and then adapt it to the circuit.
The 'reference' level in pro world is +4dbu, the consumer 'reference' is -8dbu, it makes a 12db difference.
So rather than a 30/40db pad something in the 20/30db pad should be in the ballpark ( -18/-28db if you have OCD).
Got it?
How do you learn to make this circuits?
Well... either you self educate yourself ( i did it so it's managable) or you follow some courses.
You are in the right place for first option, but'll have to do the hardwork, people here will happily help you through your journey but it'won't be without proof you've done your homeworks first. 😉
Do you know how to 'read' a schematic? This is the first step.
Once done you'll know what to do with it... i mean a schematic tells you what and where to connects components between them ( can tell more by the values of the components when you'll be more advanced).
So once you've sorted what to connect with what then it's realisation time.
With simple circuits like this one there is a number of options to make the circuit: if you want to prototype ( i encourage you to do that) then you need a protoboard, the needed components and a psu.
Once done if the circuit behave like what you wanted.... it's time to build it definitely: a profesionally ( or not!) made pcb, perfboard, 'point to point' technique.... are all valid options.
For such simple circuits perfboards are great. And if you go stompbox, you'll probably use them often... as you'll quickly realise pcb are costly and you can translate any schematic to a perfboard by yourself... 😉
You'll need PSU ( power supply unit) to power your circuit. For this i recommend you use a pcb ( there is tons of different psu project availlable... you target a +/-12V or +/-15V , something with lm317/337 as regulators should be ample. While at it if you can implement a +9v output too you'll find it handy when prototyping stompbox circuits...).
While at it if you find you like the process buy two set of psu: one for your rack, another for a dedicated 'lab psu' to feed your next prototype... i've got one with +/-15v, +/-12v and...i latter built a +9v. As those are the 'standard' voltage i use 90% of time...
Ok this is for the practical side of thing.
For the theorical: read the links which are given to you ( and if you have question ask them in your thread).
The link i gave you to modular synth adapter include everything you need to know about this circuit you asked for ( how to adapt pad and 'make up' gain circuit etc,etc,...).
Pad, buffer, voltage follower,... google them, and see what is proposed.
Wikipedia is usually a good start and i recommend ESP site for anything audio related( Elliot Sound Product, Rod Elliot covered almost everything you could imagine in audio electronics and he is a great clear teacher!).
Study it and from there ask what you didn't get i'm sure you'll find people pleased to help you. 😉
Ok the effects you wanna play with are the kind which are worth the hassle: analog modulation effects ( phaser/flanger/chorus... as well as delay) have a 'special' sound to them compared to their digital equivalent. Disto... nothing like an stompbox in my view too.
The levels: you are right that your Tascam ( https://homerecording.com/tas488specs.html ) is -10dbV referenced ( 'consumer' level).
Pro level is +4dbU referenced ( did you spot the difference between both db unit? U/V means different things about the reference point).
So we will have to translate dbV to dbU to be able to compare things between them.
Here you'll find more info about those differences as well as the expected voltage reading for different levels you could encounter:
https://www.sowter.co.uk/decibels.php
So from there we know that 'dbV is not related to any impedance ( like dbU) but is relative/referenced to 1Volt).
So we will take a look at 1Volt voltage and at which level it translate to dbU: it is in between +2 and +3 dbU, so let's take +2dbu for sake of simplicity.
Iow it means that +2dbu= 0dbV and the reference point is -10db below this level. So in the vicinity of -8dbU (= 0.304 Volt rms).
If you have read the Tascam specification's link it should remain some numbers which were given.
Ok so what next from here? We have 'translated' dbV to dbU so from now it's a matter of finding the difference between both in db and then adapt it to the circuit.
The 'reference' level in pro world is +4dbu, the consumer 'reference' is -8dbu, it makes a 12db difference.
So rather than a 30/40db pad something in the 20/30db pad should be in the ballpark ( -18/-28db if you have OCD).
Got it?
How do you learn to make this circuits?
Well... either you self educate yourself ( i did it so it's managable) or you follow some courses.
You are in the right place for first option, but'll have to do the hardwork, people here will happily help you through your journey but it'won't be without proof you've done your homeworks first. 😉
Do you know how to 'read' a schematic? This is the first step.
Once done you'll know what to do with it... i mean a schematic tells you what and where to connects components between them ( can tell more by the values of the components when you'll be more advanced).
So once you've sorted what to connect with what then it's realisation time.
With simple circuits like this one there is a number of options to make the circuit: if you want to prototype ( i encourage you to do that) then you need a protoboard, the needed components and a psu.
Once done if the circuit behave like what you wanted.... it's time to build it definitely: a profesionally ( or not!) made pcb, perfboard, 'point to point' technique.... are all valid options.
For such simple circuits perfboards are great. And if you go stompbox, you'll probably use them often... as you'll quickly realise pcb are costly and you can translate any schematic to a perfboard by yourself... 😉
You'll need PSU ( power supply unit) to power your circuit. For this i recommend you use a pcb ( there is tons of different psu project availlable... you target a +/-12V or +/-15V , something with lm317/337 as regulators should be ample. While at it if you can implement a +9v output too you'll find it handy when prototyping stompbox circuits...).
While at it if you find you like the process buy two set of psu: one for your rack, another for a dedicated 'lab psu' to feed your next prototype... i've got one with +/-15v, +/-12v and...i latter built a +9v. As those are the 'standard' voltage i use 90% of time...
Ok this is for the practical side of thing.
For the theorical: read the links which are given to you ( and if you have question ask them in your thread).
The link i gave you to modular synth adapter include everything you need to know about this circuit you asked for ( how to adapt pad and 'make up' gain circuit etc,etc,...).
Pad, buffer, voltage follower,... google them, and see what is proposed.
Wikipedia is usually a good start and i recommend ESP site for anything audio related( Elliot Sound Product, Rod Elliot covered almost everything you could imagine in audio electronics and he is a great clear teacher!).
Study it and from there ask what you didn't get i'm sure you'll find people pleased to help you. 😉
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I get you started about pad, buffer and voltage follower:
https://effectpedalkits.com/blog/effect-pedal-circuits-the-buffer/
https://en.m.wikipedia.org/wiki/Buffer_amplifier
http://www.uneeda-audio.com/pads/
https://effectpedalkits.com/blog/effect-pedal-circuits-the-buffer/
https://en.m.wikipedia.org/wiki/Buffer_amplifier
http://www.uneeda-audio.com/pads/
And opamp make up gain amplifier:
https://en.m.wikipedia.org/wiki/Operational_amplifier_applications
Try identify the kind of circuit used in Cgs adapter for make up gain ( the TL071: is it configured as a voltage follower, a difference amplifier, an inverting amplifier,...), and then verify if it have a gain of 20 as expected.
With all this links you have enough to taylor the previous circuit to your needs ( and understant what happen in it).
https://en.m.wikipedia.org/wiki/Operational_amplifier_applications
Try identify the kind of circuit used in Cgs adapter for make up gain ( the TL071: is it configured as a voltage follower, a difference amplifier, an inverting amplifier,...), and then verify if it have a gain of 20 as expected.
With all this links you have enough to taylor the previous circuit to your needs ( and understant what happen in it).
I get what you are trying to accomplish useing pedal effects instead of dsp so you could add the effect to a dry signal. However most of the effects are being used to drive a guitar amp front end, and the player is usually using the effect while overdriving the input section of the amp. This combined with the pedal effect, volume Level on the guitar itself, and how hard the player plays the strings all combines to create the effect. A lot of the time the player is riding the cusp of distortion and will transition in and out of it while using the effect. The front end of a mixer just won’t react to the pedal in the same way since it is designed to not distort. When pushed to distort the distortion will not be the same as a guitar amp preamp stage, that is why a lot of players prefer tubes.
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