timmy with xotic booster 3pdt idea?!

[otomo]

hi guys, following the amazing help by chuck d bones and liani on the chrome dome tone conundrum, thought id see if anyone had any tips about an idea id like to get done,

im trying to put a timmy clone, and a xotic ep booster clone onto one pcb. with a 3pdt switch to change the order. so overdrive into booster, or, booster into overdrive.

i got a prototype done, but its hella noisy! i guess as could be expected! all works "as it should" but im just having a problem with controlling the masout of gain when the order is changed. i think my switching is correct on the 3pdt, but anyone have any ideas to tame this down abit, as past 12 o'clock on the gain control its feeding back and oscillating like crazy.

so far ive tried changing the pot values of gain, volume and boost to try to tame it down, but with no success. surely if these two were seperate store bought pedals they wouldn't be so unusable once controls started to get turned up?!

any ideas would be amazing, as the timmy sounds soooo good! cheers, hope your all well.

 

[HamishR]

I'm no expert with PCB layout so I'll leave that to others... But a few questions - what sort of guitar are you using? SC or HB pickups? and have you tried using this booster into this pedal outside of the same box? I ask these to rule out (a) this particular combo of FX and (b) to rule out that it's just your guitar and lots of gain.

My Strat can get very noisy with some Muffs, for example, while my Les Paul is whisper quiet. I find when using two FX which have substantial gain the noise floor can climb rapidly. It may not be the way you have routed the effects in the box. If you have tried these FX in separate boxes with less noise then it may be a layout issue. It's not uncommon for layout to cause noise, oscillations, shrieks, etc. Keeping inputs away from outputs is a good start, but I'll let others chime in. I know from experience that sometimes keeping the power well filtered can be vital.

 

[otomo]

hi hamish, thanks for your reply!

yea its a strat i've got as well, i know what you mean with big muffs! but i did borrow a friends epiphone with single coils in and was still pretty much the same, its like i need to tame down all the gain stages through the pedal, but just find it strange that if they were two separate pedals they would be fine. so leads me to believe either i have created some sort if feedback path, my switching on the 3pdt is wrong, or there's some sort of input buffer impedance difference i haven't noticed.

 

[phi1]

Here’s a few thoughts / questions. These probably won’t address the noise problems you’re describing. Although it still sounds like you might have a wiring error.

I’m not sure what that schematic is, is it yours or something your referencing? I’m assuming reference because it’s obviously not a Timmy circuit... just not sure why you included it without describing what it is (unless I’m missing something obvious).

the original ep booster circuit (like how it’s drawn there) always had a volume increase even with the knob turned down. The newer version replaced the bass dip switch with a -3db switch so you could access unity volume if desired. If you added a master volume (external or trimmer) to the boost side, it might help you not overload the overdrive as much when the booster is first.

even with the bass dip switch not activated (10uF cap activated, not 100uF), the EP circuit has a bassy sound. Something to do with the phase shift of the jfet reinforcing bass frequencies (I guess, from things I’ve read). Anyway, for me the bassy sound is not ideal when boosting into overdrive, but I really like it at the end of the chain. I would make the switch external, and use 10uF for one side and 1uF for the other (1uF being a bass cut mode for nicer boosting into the OD). Or, hardwire The 1uF, and put the 10uF in series with a ‘bass’ pot. Just some thoughts to experiment with.

 

[otomo]

hi phil, cheers for the input.

sorry, your right, the overdrive is actually taken from madbeans turnabout, which in turn is inspired by jhs andy timmons, or angry charlie.

there's an episode of that pedal show, where they are testing overdrives with boosts, before and after, and right at the end, they test the ep booster with a jhs angry charlie. it sounds amazing! so i kind of want to put both into one enclosure with the ability to switch the order.

ok i didn't know you could get an ep booster that offered unity! that's great news. however, i do take on your comments about the bassyness of the xotic. im thinking about maybe trying to switch it out for say the arrows booster circuit idea from EQD. that way i know i can easily set unity level, so as to not affect the gain so much when i switch effects order.... i think...

but actually, then things will be easy, kinda fancy a challenge! so, ill take your tips of changing up the 10uf/100uf and give that a go, and also stick a master volume trim pot on the end of the ep booster section, see if i can get them to play happly with that!how do you think they were using the dip switch to get a -3db?

 

[otomo]

and thinking about it, couldn't i just add a 5v regulator to the ep booster side, thus cutting the power to it, and reducing the gain!?!?!

 

[phi1]

I wouldn’t recommend this. You may introduce distortion. You also may have to change other components to properly bias the jfet. Of course you could try it and report back what you find out, maybe it’ll work out. But, a simpler method would be to stick a 50k trimmer at the end of the ep circuit, wired like a volume pot. Set it for unity volume (or whatever you want) with the boost pot at minimum.

 

[otomo]

yep, pretty much as soon as i typed that i knew id have somethings to change! ive got the voltage bias from the tl072 to try it out, but im going to stick a little trim pot to ground after the ep section, try that first as its easiest!

hope i can get this guy usable, as just before everything starts to go really crazy, its sounding great!

 

[otomo]

ok, added the trim pot and changed up the values of the bass caps, anyone have any other ideas to try before i order the pcbs?!

 

[phi1]

Is it working better than it was now?

 

[otomo]

yep, much better! thank you phil.