Madbean Glam Chorus Sound Issues

[Pavlos]

I've got got the board built for the Madbean Glam Chorus. I've been over it carefully a number of times now, cheked for correct placement, values and orientation of componets, correct placement of cuts and links, and even swapped chips in and out just to make sure there is nothing wrong there. Pots work fine and everything seems to be as it should, apart from it sounds rather dull/muffled, not so much indistinct, there is still detail there, but almost as though a treble control has been rolled back most of the way........any ideas?

[Neil mcNasty]

Sounds just like mine...
Muffled as a motherf**ker!
Been trying to wrap my head around it as well, with no success...

I'm starting to suspect that this might be what some describe as: "warm" and "lush"

Only way I can get it to sound decent, is when I add a treble boost in front of it.
Then it sounds really nice!

[Pavlos]

haha, straight to the point as always Neil I think warm and lush might be overstaing it just a tad, more like having the bass and mids set at 50% but the treble turned down to about 10% so possibly stiffled and mushed would be a better description......sounds like it could be quite nice otherwise....

[Ciaran Haslett]

100n instead of 100p maybe?  It's definitely brighter than what you're describing.  Get a few good pics up and we'll have a look.

[Pavlos]

err....100p?......check my printed version of the layout (Draft quality) against the one on the site just to be sure I'm not going mad.....and yep, a lesson learned, do not print in draft quality because it makes it difficult to read the values properly, yes I have a 100n where it does clearly say 100p between 3rd and 4th pins down on the right of the PT2399! and there was me thinking I was being so thorough (Weeps with head in hands)
Thanks Ciaran, one day I'll manage to figure out some of the basics of what does what and where in the circuits, but in the meantime all help is very much appreciated

[Ciaran Haslett]

Haha.  Easy done.  You usually see higher valued caps in this position in most PT builds to filter out the crap at longer delay times, but there is usually a dry path so you don't hear it as much.  There is no dry path in this design so a higher value would affect everything just as you described.

[Pavlos]

yep it is an easy mistake to make and I have noticed that it is usually a higher value there so I'll use that in my defence m'lud, and also the fact that I've been building for less than a year, so numpty novice award goes to.......err.....me I'm not doing too bad on debugging so far though, managed to get most stuff working, just look, check and if you can't see anything wrong, take a break, have a read up on the posts about that layout and any similar problems (If there are any symptoms other than dead as a dodo) and come back to it another day and keep on re-checking until you either find the fault and fix it or draw a total blank.....then swallow your pride and ask for help, because sometimes all it takes is someone one step removed to point out the blatantly obvious that you've missed because you're too close in to see itand every fault you fix gives you bit more knowledge, a bit more experiece, and a bit more confidence to get stuck in and give it a go

[Neil mcNasty]

I did the 100nf instead of 100pf mistake when I first built this as well, but I spotted the mistake as soon as I had fired it up the first time and heard how it sounded.
Correcting it helped a lot, but I still find it very muffled unless I filter away most of the bass frequencies.

Edit: Found my issue! After re-biasing the JFet I got the results I was hoping for and it now sounds very sweet!
Note to self: do not just set it to the specified voltage, but use it as the starting point and then tune by ear...

[Pavlos]

well I'll swap the cap to the correct value sometime over the next few days and report back, hopefully with good news.

[Pavlos]

swapped the cap and now sounds much better, warm but not too much low end and the highs sound slightly grainy, so there is brightness but it manages to stop short of being too crystaline, harsh or sterile, as though the focus is more towards the mids/upper mids. I'd describe it as more of a vintage than modern character, and though not life changeing it does sound quite nice and is worth boxing :o)

[Neil mcNasty]

After having a long and good look at the schematic, I see some potential mods that I suspect can increase the high frequencies:

- C9 (10nf at the bottom) seems to roll off highs from the signal coming from the Drain of the JFet before entering the 2399, lowering this cap might increase the highs...
- I also suspect that lowering the 2.2nf (C4) might also have an effect on how it modulates the higher frequencies. I'm not sure if that is desirable, as it probably will have an effect of the whole character of the effect.
- Lowering the 220nf (C3) coming off the Source of the JFet will let less low end trough, and this might help it clear up if you feel that it has too much low end focus.

These adjustments are just plain theory from my side, and I have not tried any of them yet...
I might try this on a breadboard in the future if I get bored, but as of now, it sounds pretty good as long as i use the bridge pickup or a slightly bright pedal up front.

The grainyness you describe is probably due to the quality of the 2399 IC, as these are known to be a bit dirty in the top end, and I also suspect that these adjustments might increase this issue.
This seems to be the drawback of using the 2399, and might be something that is un-avoidable in this type of design.

Socketing the JFet might be a good idea as well if you are not using a SMD JFet, as it will help find a JFet that bias properly. Re-adjusting the bias help me get a bit more clarity, instead of just setting it to the specified voltage.

[Pavlos]

Hi Neil, I'm actually quite happy with the amount of low end I'm getting, there is enough to have weight and body, but not so much that it will mush out with a neck pickup and tone rolled back. I think the high frequencies are about right too, the roll off is high enough not to rob the sound of definition and clarity, but as you mention, any change in the cap values might increase brighness a bit but not neccesarily improve the sound quality, just allow the slight graininess to become more obvious and possibly intrusive. Sound wise it reminds me a little bit of some older digital effects (In a good way) where the overall bandwidth was slightly limited, but the focus was where it mattered most. It's probably not the best sound quality digital chorus out there by any means, but it is a nice musical sounding circuit.

Biasing the JFET wasn't a problem either, swapped a few to see which worked best (Mixture of J201 and 5457's both TO92 and SMD on daughterboards) and all worked ok, I always socket them though so I can swap out for something best suited to the circuit if needs be :o) and as you mention tweaking by ear can help change the tonal balance slightly, sometimes the suggested voltage just doesn't quite do it for you and a little tweak higher or lower can really make a circuit work for you

[Neil mcNasty]

Cool that you got it to work to your liking Pavlos!

Been using this a lot the last days, and I have to admit that I like it more for each day after I tweaked the bias.
Without a doubt the best sounding Chorus with such a low parts count on this site.

Previously I actually never had much fancy for Chorus effects, but that's changing and this one will become a stayer on my board.
I get a lot of cool synthy sounds with some of my octave fuzzes (a modified one-knob version of the Ampeg Scrambler with only the octave pot, a super modified Robot Devil and the Bit Commander)
Seems like my taste in effects changes as I progress as a guitar player, and as I expand my styles of music and setups.

[Pavlos]

yeah know what you mean about chorus, can be good for some things but can be far too obvious as well. I I much prefer phasers, they just seem to be a bit more organic and sit better for me, never got on with flangers though, they just seem to get in the way and overpower everything :o/

I don't to get on with octave fuzz either so far, but as you mention about tatses changing, up until I had a go at some of the fuzz circuits on here I'd never found one that I thought was anything other than godawful sounding rubbish. However, I've now found a few that I really like and fit in nicely with my other dirt/noise pedals