Rebote 2.5 delay sounds great , but the distortion is a pity , suggestions ?

[alfafalfa]

Hi, just finished my Rebote 2,5 delay; it fired up the first time , sounds terrific but what I like most are the long delay times and the distortion that comes after the sounds is rather prominent. I'm accustomed to my Rocktron Intellifex and Lexicon 550 which are of course in a different league.
Is there a remedy for the distortion or does it come with the simple  delaychip ?
The design is very quiet I must say and I like the overall sound a lot .

Alf

[alfafalfa]

Just uploaded a picture of it .

http://s113.photobucket.com/albums/n233/alfafalfa/?action=view&current=delay1small.jpg

Must box it.

[oldrocker]

I just built one of these myself and I've not heard of anything that would help the distortion as far as I know.  A PT-80 is supposed to be cleaner with a compander.  What's wierd is that when I first fired up my Rebote it was pretty clean and I'm not sure why.  Then it stopped working right with only one delay no matter where I set the repeat knob.  So I found a cold solder joint and fixed it only to find it has the distortion everyone talks about.  I wish I could figure why it was cleaner before I fixed the solder joint than it is after.  Oh well it still a cool effect and a interesting build.

[markm]

I have to say that's a nice looking build but, I haven't experienced the distortion you mention.
Then again, I use mine for slapback and that could be the difference.

[sfr]

Yeah, with the Rebote, the longer the delay, the more distortion. (I have a switch that doubles the length of the delay, and it's *very* noticable then.)   The annoying part of the distortion seems to be present mostly in the higher frequencies, upping the values of the capacitors a bit in the lowpass filters in the delay line cleaned things up for me.  Socket them and experiment - too much, and the repeats will sound too muddy.   

Although, whenever someone mentions distortion on this circuit, I have to wonder exactly what they're talking about - perhaps they're hearing something entirely different than what I'm thinking of from my builds, and something is wrong with their boards?  Or mine? 

[oldrocker]

Yeah slapback is mostly what I'll use it for.  It's nice for that Rockabilly style sound too.

[blanik]

it sounds more like white noise present during the repeat, between repeats it's dead clean... and like everyone mentionned, the shorter the delay the repeats...

i noticed that when playing live with a band the noise is not really noticeable (specially with a distorted guitar signal) the feel and sound of a tape echo is very similar to the Rebote 2.5 (i had a similar noise/dist on the repeats with my old Roland Space Echo)

and the Rebote being small like it is, it's soooo much more convenient than the SE... 

R.

[sfr]

Ah, yeah.  The white noise type of thing you describe is what I had, and what I was able to minimize by lowering the cutoff in the lowpass filtering. 

I noticed the same thing - that in a band context it's hardly noticable, and if it's present in a recording, it was fairly easy to eliminate with a little notching EQ.  I honestly never noticed it at first, but once I did, it started to bug me.

[alfafalfa]

Hi,

SFR ,

I was able to minimize by lowering the cutoff in the lowpass filtering. 

How exactly did you do this ?
I think now I have listened more carefully that it's not the repeats that cause the distortion ( by building up ) but the white noise.

Alf

[sfr]

I upeed the values of a couple of capacitors - I don't remember which ones exactly (I experimented with a few places) - I'm at work right now, I'll check when I get home and post later today. 

[sfr]

I changed the 560pf cap off of pin 15 on the PT2399 ( in the feedback loop of the first opamp in the PT2399) to a .001uF.  I changed the .001 cap off of pin 13 (in the feedback loop of the second opamp in the PT2399) to .033uF. 

Like I said, this rolls off even more high end, warming the tone of the repeats more - I happen to like this, and don't find it too drastic, but you'll want to experiment and find a happy medium for your usage.   This is what worked best for me.  I actually have two Rebotes, a 2.5 and a 2, and I use both of them quite frequently (different pedal boards for different bands) and don't find the "dirt" on the repeats bothersome at all when I'm playing with a drummer.

I'd actually imagine you could increase the value of any of the caps to ground along the delay chain (the .027uf or the .01uF caps before the two opamps in the PT2399) and possibly the 51pF cap at the feedback loop of IC2A at the output to make this sort of thing work, but I'm uncertain - this is what worked for me.)

Honestly, I'd rather deal with the Rebote's shortcomings than with the tone I've gotten out of some of the commercial delays I've had.

Playing around with a graphic EQ I was able to cut out most of the white-noisy-distortion that accompanys the repeats while effecting the tone less - I wonder about the possibilities of finding the key frequency range and constructing a notch-filter to tack into the circuit.

[alfafalfa]

Thanks SFR your your suggestions. I'm going to experiment with those values and will see what it gives.
Will report back.

Alf

[alfafalfa]

SFR,

I changed the .001 cap off of pin 13 (in the feedback loop of the second opamp in the PT2399) to .03uF.

Surely you must have meant  0.0033uF = 3n3 ??  I put in 33n and the sound was hardly present anymore and very muffled.  But even with 3n3 I lost too much high frequency content and  eventually I chose to put everything back the way it was.
Also on the shorter delaytimes you lose too much in my opinion.
I guess I'll  have to live with it.

Thanks for your help.

Alf

[sfr]

Oops!  Yes, I probably did mean that!  Either a typo or I misread (maybe both!)  Those two caps in the feedback loops are definetly the ones I changed - I thought I had marked down the values, but didn't, so I was trying to squint and read the little numbers on the caps in there, which where unfortunetly oriented so they faced each other, meaning I was trying to read upside down between two components.  Sorry if I steered you wrong.

If I remember correctly I also changed the 33K off the level pot into the mixing opamp to get a little more volume on the repeats.   My Rebote 2 at max volume, the repeats are actually slightly louder than the clean signal, and I liked that, so I was trying to match it.

[rogeryu_ph]

Alfafalfa, Mine I just finished. I don't hear the distortion or any white noise? I read the Princeton datasheet about PT2399 and they has a table provided for distortion factor value for the RA. In this case I opted to use only Trim pot 20k instead of 15k resistor. I set the trim pot while still not on the board into 11.5k you try this. Also, I used a T0-220 type 7805 reg IC not the 78L05 co'z this surely get heat. The T0-220 can handle the heat even without heatsink. This heat maybe the cause of noise or distortion your experiencing. Well I'm not an expert but I could share my experience, better try than never and give me feedback. The only problem I encountered is the pop sound when I switch on the Millinium DPDT bypass that I used. Does your's  also? I don't encounter this pop sound with TS and Big muff with Millinium.

[sfr]

Both rebotes I've built have always popped the first couple of switches after powering them up, and not after that - I have no idea why.  I always turn them on and off several times before I start playing a gig.  It's wierd, I've never had that problem with another pedal.

[alfafalfa]

Thanks for the clue rogeryu_ph,  I will try this .
Must feel the 7805 to check the heat !
Just did : mine doesn't go over 25 (77 F) degrees centigrade  in a room temp of 16 (60.8 F)degrees.
So no problem there !

Alf

[rogeryu_ph]

Now you only have one option, is to replace the 15k resistor with 20ktrimmer. Set the trimmer before soldering it to pcb about 11.5k almost there like mine. If this still not the cure, I guess your PT2399 attributed the noise or inherent. Ofcourse you can check that if you have spare one to compare with. By the way, your PCB is nicely done.
Sfr, It's weird... mine is always popping when switching on..... How about your's Alfafalfa? 

[alfafalfa]

Just put up a sample of the distortion I get with my Rebote.
Got used to it by now , and with distortion it isn't noticeable.

http://www.esnips.com/doc/f6993fb0-8702-4d9d-9b7b-c4e4568e4b49

[markm]

Hey there alfafalfa,
I listened to your clip and I have to say, I don't get that kinda noise out of mine.....I don't know what I did differently than you other than I have no ceramic caps in my build at all and I used regular old poly for the other caps, basic electros and 5% carbon film resistors.
Mine does not make the noise I heard in yours.