Line and pedal level question (related to dsl401 eff. loop)?

[zvincic]

Hi guys.

I have this great little combo (dsl401 ofcourse) but one thing really annoyes me. The effect loop is designed just for line level effects (IMO stupid with a small combo) and I am a pedal(s) (ab)user

And the loop is parallel too.

As I would like to put a DD6 in the loop (the rest stays in front) I wonder what's the best way to attenuate the signal from send to pedal and to amplify it from pedal to return?
any schematic(s)?

I would like to keep the amp stock.

Thanx.

[niftydog]

inverting op amp with gain less than 1 to bring it down to instrument level, through the effects, inverting op amp with gain greater than 1 to bring it back up to line level.

Fairly standard op amp config, look at this site for details about how to calculate the resistors to set the gain.

[zvincic]

thanx for the info but would it be too much to ask for a schematic?


I'm a total noob

and how do I know what's the gain of an particular op amp....say...pretty standard tl072?

[niftydog]

so, you didn't read that link...

The gain of an op amp is set by the resistors in the feedback path. You can therefore set it to whatever you want (within reason).

Below, a design for a bipolar power supply. Use two of these either side of the effect pedal. First one with negative gain (<1), second one with positive gain (>1). You'd need to experiment with resistor values to get the right gain. Perhaps try using a pot as Rf, adjusting it to get the desired results, then replace with an appropriate resistor for the final circuit.

Code Select Expand


GAIN = Rf/Rin
               Rf
               ___
            o-|___|-o
            |       |
    Rin     |       |
    ___     |  |\   |
IN -|___|-o--o--|-\  |
               |  >-o- OUT
             o-|+/
             | |/
             o
             |
            ===
            GND


BTW, there's loads more info on the datasheet of the particular op amp you choose. I would perhaps consider a TL072 as this is a pretty good dual op amp.

If the words "bipoar power supply" are causing you to stink up your pants, you can alter this circuit to work from a single supply.. but it may be easier to buy an op amp designed to work from a single supply... like the LM358

Another great resource for single supply op amp circuits.

BTW, this is the diystompboxes.com forum, not the somebodydesignmeacircuitplease.com forum. DIY, dude. You'll learn something from doing this yourself and it's pretty simple and straight forward.

[Paul Perry (Frostwave)]

so, you didn't read that link...

BTW, this is the diystompboxes.com forum, not the somebodydesignmeacircuitplease.com forum. DIY, dude. You'll learn something from doing this yourself and it's pretty simple and straight forward.

Hey, give the guy a break, if he is new to electronics that link is not a 'paint by numbers'.
If anyone wants to do a stripboard layoyut for it, feel free!
I can even see a box for that being a product  :wink:

[niftydog]

it's my warped and twisted way of encouraging people... sorry if it upset you, zvincic.  

But it is good to accomplish stuff like this for yourself, you'll comprehend it much better than if someone just gives you the answer. It's really not that hard a task for a noob. And the satisfaction and appreciation you get will also encourage you.

I guess it's the old "In-my-day-I-walked-20-miles-with-no-shoes-and-no-coat-through-a-raging-blizzard-just-to-go-to-the-toilet" syndrome.

[zvincic]

it's my warped and twisted way of encouraging people... sorry if it upset you, zvincic.  

no problem

It is much easier to for me to understand what's going on in the circuit when I actually see it. That's why I asked the schem.

btw. I did try to read that link but it was 4am and I was going like: shit man, I don't understand this. Try to picture me with eyes half closed and my head just waiting to bang on the keyboard  



anyway, I appreciate the help.

one should not be afraid to ask something he is not familiar with

[David]

Hey, Nifty -- actually you hit it right on the head.  Good call!

Zvincic:

Here's your answer.  Go to R.G.'s site (www.geofex.com).  Look up the article on the "Adjusticator".  Half of this circuit could serve as your "volume cut" and the other half as the "volume boost".  R.G.'s already done the heavy lifting.

[zvincic]

Here's your answer.  Go to R.G.'s site (www.geofex.com).  Look up the article on the "Adjusticator".  Half of this circuit could serve as your "volume cut" and the other half as the "volume boost".  R.G.'s already done the heavy lifting.

thank you!