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DIY Stompboxes => Building your own stompbox => Topic started by: O'malley's Alley on January 15, 2004, 11:36:54 PM

Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 15, 2004, 11:36:54 PM
I really dont get how a feedback loop works.  Its such a simple circuit, and can make thing oscillate beyond belife.  Anyone know how it works?  Here is a schematic of one:

(http://acapella.harmony-central.com/forums/attachment.php?s=&postid=6347020)
Title: Technology of a feedback loop?
Post by: bwanasonic on January 16, 2004, 02:38:24 AM
I have been curious to fool around with this type of circuit, but something seems a little screwy in that diagram. I don't know much, but what I know doesn't  jibe with that schematic. Is that all there is? Then let's keep dancing...

Kerry M
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 16, 2004, 04:04:50 AM
the schematic works, cause I tested it out, and you can make some really wierd sounds.  I just dont understand how it works.
Title: Re: Technology of a feedback loop?
Post by: Ansil on January 16, 2004, 05:01:11 AM
Quote from: O'malley's AlleyI really dont get how a feedback loop works.  Its such a simple circuit, and can make thing oscillate beyond belife.  Anyone know how it works?  Here is a schematic of one:

(http://acapella.harmony-central.com/forums/attachment.php?s=&postid=6347020)

it loops the output to the input. of the effect in the loop.  there fore making it a continous feedback,  feedback happens when you catch the audio signal from the output of a speaker or a audio signal, and it gets reamplified again and again and again.  basically making the gain so high it is unstable to wich it oscilates.
Title: Technology of a feedback loop?
Post by: bobbletrox on January 16, 2004, 08:28:47 AM
I don't get how you use it.  So you connect an effect in the loop, and it'll basically make feedback?  I can imagine what it'd sound like with distortion but what would happen if you stuck a flanger or somethin' in the loop?

...and what's the deal with that input jack?  Is the orange wire going to the tip, green to the ring and black to the sleeve?  :shock:
Title: Technology of a feedback loop?
Post by: doug deeper on January 16, 2004, 02:42:22 PM
geocities.com/midfielectronics/tsa
heres a better scheme...
doug
Title: Technology of a feedback loop?
Post by: Marcos - Munky on January 16, 2004, 03:19:55 PM
You don't get feedback with this "effect", but get noise. I tried with my Obsidian and got some cool noises, and the theremin-like sond when you turn the guitar knobs. With a flanger, I think you will get some "spacial" and "ovnis" sounds.
Title: Technology of a feedback loop?
Post by: ExpAnonColin on January 17, 2004, 12:46:12 AM
You can create feedback loops which function almost identically with a stereo pedal and by connecting 1 input to 1 output and then putting whatever you want into it and whatever out of it.  The resistor in the schematic is basically making sure that the audio level is correct for the correct feedback (more like oscillation) to occur.

-Colin
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 17, 2004, 09:30:55 PM
Quote from: doug deepergeocities.com/midfielectronics/tsa
heres a better scheme...
doug

thanks dude, that is a much better schem.  I hate schems drawn like the one I posted above.
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 19, 2004, 05:00:42 AM
by the way, on that schematic, how can I add true bypass to it?
Title: Technology of a feedback loop?
Post by: smoguzbenjamin on January 19, 2004, 10:45:18 AM
Open the switch will bypass the feedback by eliminating the feedback. I might make a momentary feedbacker :D Crazy distortion feedback madness! :D
Title: Technology of a feedback loop?
Post by: Paul Marossy on January 19, 2004, 04:50:19 PM
So, how do you hook this thing up? I've looked at both schematics and I still don't get how you would hook this thing up. Can you just connect the send and return together and switch the pot in or out of the circuit?
Title: Technology of a feedback loop?
Post by: Ansil on January 19, 2004, 05:29:23 PM
Quote from: Paul MarossySo, how do you hook this thing up? I've looked at both schematics and I still don't get how you would hook this thing up. Can you just connect the send and return together and switch the pot in or out of the circuit?



you got mail. i sent you the schematic with truebypassing as well as an active and bypass led indicator.

you can post it if you want too.
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 19, 2004, 05:51:02 PM
Quote from: Ansil
Quote from: Paul MarossySo, how do you hook this thing up? I've looked at both schematics and I still don't get how you would hook this thing up. Can you just connect the send and return together and switch the pot in or out of the circuit?



you got mail. i sent you the schematic with truebypassing as well as an active and bypass led indicator.

you can post it if you want too.

Can you send one to me also?  My email is mancubus22@hotmail.com.  It would be great if you could.  Thanks!

Tyler
Title: Technology of a feedback loop?
Post by: Paul Marossy on January 19, 2004, 05:59:49 PM
Thanks Ansil.
I still don't understand how the signal is routed through this thing, though.
I must be really dense today.  :oops:
Title: Technology of a feedback loop?
Post by: dan on January 19, 2004, 06:45:24 PM
Quote from: smoguzbenjaminOpen the switch will bypass the feedback by eliminating the feedback. I might make a momentary feedbacker  Crazy distortion feedback madness!

DUDE!! great idea! i'm going to steel it is that ok?
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 19, 2004, 07:15:38 PM
Quote from: Ansil
Quote from: Paul MarossySo, how do you hook this thing up? I've looked at both schematics and I still don't get how you would hook this thing up. Can you just connect the send and return together and switch the pot in or out of the circuit?

You put your effects between the send and the return, just like you were hooking up an effects loop.  Then some pedals just go mad.
Title: Technology of a feedback loop?
Post by: Paul Marossy on January 19, 2004, 07:36:53 PM
"You put your effects between the send and the return, just like you were hooking up an effects loop. Then some pedals just go mad."

I figured that must be how it works, but looking at the second schematic posted, it looks like it wouldn't work - there is a switch between the input/send and the pot. When the switch is off, then all signals through the box die since there is no connection between the out/return. I don't see how it's supposed to work. There must be more going on with the switching than what is shown there...
Title: Technology of a feedback loop?
Post by: Peter Snowberg on January 19, 2004, 08:51:06 PM
If you trace the signal... plug your guitar into the "input" and plug your effects input into the "send" jack. Those are connected internally. Now connect the effect's output to the "return" jack, just like an effects loop would be. Inside the box the return jack is then always connected to the "output" jack. The out of course goes to the amp thingy. If you forget about the switch and pot, it's just two pairs of jacks with direct internal connections between jacks in each pair.

Now if you connect the switch, you're adding a path from the effect return to the effect send, thus the feedback. The switch only affects that feedback path.

I hope that helps,
-Peter
Title: Technology of a feedback loop?
Post by: Ansil on January 19, 2004, 08:57:50 PM
hey paul did you look at your email that i sent you with the schematic for mine in it.
Title: Technology of a feedback loop?
Post by: Paul Marossy on January 20, 2004, 12:22:37 AM
Thanks Peter. I think I get it now....  8)
Would this thing work well in a chain of effects, but only on one guitar effect? Also, what affect does increasing or lowering the pot value have?

Ansil - Yes, I did get that schematic. Thanks.
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 03:16:50 AM
can someone post the schematic for true bypass?  If you emailed it to me, it might have gone to my junk mail box, and those get automatically deleted.  Let me know your email first if you email it to me, so I can add you to my safe list.  Thanks!
Title: Technology of a feedback loop?
Post by: Ansil on January 25, 2004, 03:28:15 AM
Quote from: O'malley's Alleycan someone post the schematic for true bypass?  If you emailed it to me, it might have gone to my junk mail box, and those get automatically deleted.  Let me know your email first if you email it to me, so I can add you to my safe list.  Thanks!

give me a minute and  iwll up load it.
Title: uploaded the truebypass schematic
Post by: Ansil on January 25, 2004, 03:30:45 AM
http://www.geocities.com/austenfantanio//sonicclone.htm

here ya go
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 03:34:03 AM
thanks, but what are the yellow and green dots on that schematic?  the ones that say active and bypass?
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 03:42:09 AM
Quote from: O'malley's Alleythanks, but what are the yellow and green dots on that schematic?  the ones that say active and bypass?

I'm guessing they are LED's
Title: Technology of a feedback loop?
Post by: Ansil on January 25, 2004, 03:50:25 AM
yeah
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 04:01:41 AM
Quote from: Ansilyeah

Which one is positive and which one is negative?  Sorry for being a pain, I just need to know this.
Title: Technology of a feedback loop?
Post by: Ansil on January 25, 2004, 04:22:30 AM
Quote from: O'malley's Alley
Quote from: Ansilyeah

Which one is positive and which one is negative?  Sorry for being a pain, I just need to know this.

no problem  the red battery wire goin to the switch goes to the positive sides of the respective leds. the sides connecting in the middle are the negative sides that tie to the same ground points as the jacks.  also you will need to use some sort of limiting on the leds or they will burnout.  you know a standrd 1k on the positive wire from the battery to the switch will work
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 04:32:42 AM
Quote from: Ansil
Quote from: O'malley's Alley
Quote from: Ansilyeah

Which one is positive and which one is negative?  Sorry for being a pain, I just need to know this.

no problem  the red battery wire goin to the switch goes to the positive sides of the respective leds. the sides connecting in the middle are the negative sides that tie to the same ground points as the jacks.  also you will need to use some sort of limiting on the leds or they will burnout.  you know a standrd 1k on the positive wire from the battery to the switch will work

cool, thanks man. You've been tons of help.
Title: Technology of a feedback loop?
Post by: Ansil on January 25, 2004, 04:56:43 AM
no problem glad u got it.. have fun with it.
Title: Technology of a feedback loop?
Post by: smoguzbenjamin on January 25, 2004, 06:12:50 AM
I'm going to have some fun with this :twisted:
Title: Technology of a feedback loop?
Post by: O'malley's Alley on January 25, 2004, 06:50:49 PM
yes, its quite crazy!
Title: Technology of a feedback loop?
Post by: Ansil on January 26, 2004, 04:25:50 AM
http://www.diystompboxes.com/sboxforum/viewtopic.php?t=18135

i did a tutorial of this for all those following this thread  hey omalley this is for ya