effect loop send/return and power amp in/preamp out, differences?

Mantras

Member
Messages
82
Hi

I have never understood the differences between send/return and power amp in/preamp out

for example Mesa Boogie Badlander on the back there are a send and return
and Fender Hot Rod Deville have there is a power amp in and preamp out

in (very) simple terms could somebody exaplin it ?
maybe with some examples

thanks
 

Mantras

Member
Messages
82
@Mantras

For a series loop, it's the same thing.

A parallel loop is somewhat different -- do you want to know about that, or is series good enough ?

Do you have any other questions ?
Hi
yes i don't know nothing about parallel loop and series , and how good are?
I have tried Mesa Boogie Badlander , a Marshall head 100W with send return and some fender amps like Fender Hot Rod Deville
thanks
 

davidespinosa

Gold Supporting Member
Messages
5,192
Hi
yes i don't know nothing about parallel loop and series , and how good are?
I have tried Mesa Boogie Badlander , a Marshall head 100W with send return and some fender amps like Fender Hot Rod Deville
thanks

In a series loop, the delay pedal mixes the original signal (called "Dry") and the delayed signal (called "Wet").

In a parallel loop, the wet/dry mixing happens inside the amp, not in the pedal.

In this case, we set the pedal to produce only the delayed sound ("wet").

But I think most people prefer series loops, because they're simpler.
 
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ctreitzell

Member
Messages
4,619
Fender labeling explains it very well IMO.

yeah, it's difficult to give a general, one size fits all answer due to so many different designs and foibles within.

I think folks get it in their heads that the SEND and RETURN need to be connected, and that's just not the case. If you are set up to use the power sections/ cabs of amps with loops, clearly you'll be using the returns. I'll admit I often stare at the sends and returns and it takes a few minutes (hours) for the penny to drop. It's typically pretty easy: Send=Out; Return=In

You know...
many devices have a MONO send and a STEREO return; that's because many FX units are "wired" that way internally. In my rig, I literally use no returns- only sends to split the signal to feed multiple amps and cabs in a Wet/ Dual Mono/ Wet scenario.

As far as SERIAL or PARALLEL, I think some confusion comes from ELECTRICAL terms verses AUDIO SIGNAL routing terms. They are quite related in diagram terms, yet the results are certainly different.
 

Mantras

Member
Messages
82
In a series loop, the delay pedal mixes the original signal (called "Dry") and the delayed signal (called "Wet").

In a parallel loop, the wet/dry mixing happens inside the amp, not in the pedal.

In this case, we set the pedal to produce only the delayed sound ("wet").

But I think most people prefer series loops, because they're simpler.
hi
but are the amps designed to use series loop or parallel loop ?
or is a choice of the user how use the send&return ?
thanks
 

RyanPitch

Silver Supporting Member
Messages
346
It is the amp designer’s choice whether to have a series effects loop or a parallel effects loop. Some (more modern) amps have the ability for you, the user, to switch between parallel and series.

The power section of an amplifier is probably designed independently of whether the loop will be series or parallel. Rather, it is designed to take one type of signal (voltage, impedance, and current) and output a different type of (voltage, impedance, and current) signal.
 

davidespinosa

Gold Supporting Member
Messages
5,192
but are the amps designed to use series loop or parallel loop ?
or is a choice of the user how use the send&return ?

It's part of the amp's design.

Let's review different kinds of loops:
* No loop at all
* Passive series loop
* Passive parallel loop
* Active series loop
* Active parallel loop

No loop at all

This is just for reference. The preamp connects directly to the power amp:

Preamp ---> PowerAmp

Passive series loop

We insert a pair of jacks between the preamp and power amp:

Preamp ---> SendOutputJack ReturnInputJack ---> PowerAmp

Now we can access the preamp output and power amp input, and we can insert effects between them.

But the preamp output isn't good at sending signals -- it doesn't produce very much current.
And the power amp input isn't good at receiving signals -- it requires a lot of voltage to produce full power.

Active series loop

To solve those problems, we put a buffer at the send output, and a gain stage at the return input:

Preamp ---> Buffer ---> SendOutputJack ReturnInputJack ---> GainStage ---> PowerAmp

The buffer can produce lots of current.
The gain stage amplifies the signal from pedal level (around 1 volt) to power amp input level (10+ volts).

Passive parallel loop

It's possible to make a passive parallel loop, but it has too many problems, so nobody does it.

Active parallel loop

We change the return gain stage to a mixing stage, which combines the dry, un-effected signal from the preamp with the wet-only signal from the effects:

Preamp ---> Buffer ---> SendOutputJack ReturnInputJack ---> MixingStage ---> PowerAmp

Because it's hard to draw, I didn't include the dry signal path. It goes from the buffer to the mixing stage:

Buffer ---> MixingStage

If I was drawing on paper, I'd include it.
 

Mantras

Member
Messages
82
It's part of the amp's design.
Hi Davidespinosa
Really great post !
is there a way to find out which amps are Passive series loop,Active series loop,Passive parallel loop,Active series loop,Passive parallel loop,Active parallel loop ?
they don't add anything in the specs

and would be really great understand which amps do eat/accept pedals and which amps are not suitable for pedals/stomboxes (i talking about use some pedals in front , i mean guitar -> pedals->amp imput , i'm not talking about send/return)
thanks Davidespinosa , really appreciate it
 

davidespinosa

Gold Supporting Member
Messages
5,192
is there a way to find out which amps are Passive series loop,Active series loop,Passive parallel loop,Active series loop,Passive parallel loop,Active parallel loop ?
they don't add anything in the specs

You can usually tell:

* Series loops are more common than parallel.
* If the loop is parallel, they usually say so.
* An active loop is also called a "buffered loop".

and would be really great understand which amps do eat/accept pedals and which amps are not suitable for pedals/stomboxes (i talking about use some pedals in front , i mean guitar -> pedals->amp imput , i'm not talking about send/return)

Search for threads with "pedal platform" in the title.
The TGP search function works very well, it's worthwhile to learn it.
 
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