The Boss Mystery Pedal Mod

[MatthewD]

Can anyone help identify this mystery pedal mod?
I was late night shopping on ebay and saw a Boss CE-2B Bass Chorus Pedal for sale. I looked at the photo... looked good and the description said tested and working.
When the pedal arrived I got a bit of a surprise... an extra switch. So I jumped online and realized that the photo I looked at on the auction had been taken from a low angle... hiding the extra switch.
So I am wondering if anyone can tell me exactly what I have got? Whoever did the mod signed the pedal (See the photo link below)
Note the switch on the front connects directly to the exact middle of the circuit board.
Moral of the story... late night shopping is dangerous. Never shop when sleepy.
Can anyone help identify this mystery pedal mod?
https://www.dropbox.com/sh/mz84jhz1elgcbqm/AADSX0t9j-lqodfZneQerhWDa?dl=0

This is my first bass pedal so I am not an expert, in fact I barely qualify as a beginner, however to my ears the mod switch (3 position) seems to switch between chorus and tremolo (I think), to my ears the difference is slight on most settings.

Matt.

[Mark Hammer]

Based on the photo, the pads where the most accumulated flux is located (hence, one assumes some post-production soldering) appears to be in the vicinity of C14.  That cap sets the bass response of the wet signal.  On my own chorus builds, I will often install a "bass-cut" toggle, to swap between full bass and reduced bass.  Trimming back on the bass reduces the obviousness of the pitch wobble in chorus pedals.  So that's my guess.

I will also note that pads 3 and 4 are empty.  You can see that those are for power.  Not sure what's up with that.

[Rob Strand]

Is the switch two or three positions?

Well it's clearly a modded unit.   So I don't think it's a bad thing unless you are collecting units.

There's a bit more info on this page, include the parts overlay so you can match-up which points have been soldered to the schematic.

https://www.hobby-hour.com/electronics/s/boss-ce2b-bass-chorus.php

As for what has been done.    I'm seeing the same as Mark and a possibly a couple more mod points.
However to me, the mods don't look like a Vibrato mod as R21 would normally be lifted and
I cannot see any soldering around R21.   So maybe the switch is switching the value of C14 as Mark indicated.

You could lift the board but be *VERY* careful as the wires to the added switch might be short and get pull off.
You might even need to loosen the switch.   What I 'd be looking for is
- if C14 has been replaced by wires
- if there are two caps mounted on the added switch.
- how many terminals of the switch are used

What I see is:

1) C14 has either been change or the C14 terminals have been used for wires as part of the mod.

     As a side note under IC1 are three resistors I believe these are:
      - Looks unmarked.  R7  going to Vcc/2
     -  R7  which seems to be really R21
     -  R8

   There seems to be no soldering around R21 for a vibrato mod.

2) Wires from solder terminals 3 and 4 removed.

     What I think has been done here is AC adaptor input as been changed from the
     old unregulated ACA adaptor (nominal 9V but really 12V) to the newer regulated PSA adaptor (9V).
     They have probably wired the adaptor and -V terminal directly to the socket.
     That method can promote hum entering the audio- I don't like it.

    Read more on the different Boss adaptors at:
    http://stinkfoot.se/archives/726


3)  C18 possibly replaced.   The tech who modded it might have replaced this to extend the life of the unit
      since electrolytic caps fail over time.


So if C14 is being switched you should hear more bass coming through in one position.  That would be best heard with the Level pot on full.

FWIW, the difference between the CE2B and the CE2 is the addition of the Level pot *and* the fact C14 is reduced to prevent chorusing of the bass fundamentals notes..  So maybe they switch C14 to a larger value to make it more like a CE2.  (This is mentioned at the bottom of the link I posted above.)

[MatthewD]

It is a 3 position switch
There is nothing in the C29 position, it looks like whatever was there has been pulled out?

C14 cap is still there, one wire from the added switch goes to either side.

There are two caps mounted on the added switch, however there is way to much glue for me to see how it is wired.

Cheers,
Matt.

[Rob Strand]

There is nothing in the C29 position, it looks like whatever was there has been pulled out?

Two possible reasons.  The first is to create space for the switch/mods to fit.  To me C29 looks (just) out of the way of the switch, but it could be close.   The second is pulling C29 might help lower the hum issue I brought-up in point (2) of my last post.  It's kind of fixing a problem that is created by the mod, normally you wouldn't want to remove C29!

It is a 3 position switch

C14 cap is still there, one wire from the added switch goes to either side.

There are two caps mounted on the added switch, however there is way to much glue for me to see how it is wired.

OK, so that confirms Mark's bass-cut mod theory.   (The dry signal is not bass cut, only the delayed signal.  The idea is it stops pitch blur on the lower notes.)

The three position switch is just a way of fine tuning the amount of bass-cut.  That's the main purpose of the mod.

The center will have the most bass cut to the delayed signal, then up and down will add a bit more bass.  No way to know if up or down has more bass.  That's entirely up to cap values and would be best worked out by ear.   

If C14 is marked "123K" or "123J" or "123" that would mean the center switch position is the normal CE-2B mode.  If you see a smaller first two digits or a smaller last digit, like 103  or 822, that would mean the center position would cut more bass than the standard CE-2B.

If C14 is not 123K without knowing the other cap values it's not possible to work out which switch setting represents the normal CE-2B mode.

Similarly, with out knowing the cap values it's not possible to know if it does a CE-2 mode or not.

Despite the uncertainties the purpose of the mod is clear and those types of mods are quite useful for bass (even guitar really).

[Mark Hammer]

Sometimes, one wants a very obvious and "thick" chorus sound.  Sometimes you want a bit of swirl but nothing too obvious.  Shorter delay ranges, verging on flanging, will produce the requisite swirly tone, and longer delay times yield the more obvious thick chorus.  Wet level adjustment can dial back the delay to make it less in-your-face and bass cut for wet signal can also keep the swirl and lose/lessen the wobble.  The wobble is still there, but the attenuation of bass moves the region where the wobble occurs (modulation of note fundamentals) a little more to the background so it doesn't capture your attention quite as much.

[MatthewD]

Thanks for all the replies... its nice to know exactly what its doing.

I have had a look at the cap values and C14 is marking WIMA 0.01 100-

On the 3 way switch one cap says WIMA 0.01 100-
The other says WIMA 0.022 63 F4

Thanks again,
Matt.

[Rob Strand]

I have had a look at the cap values and C14 is marking WIMA 0.01 100-

On the 3 way switch one cap says WIMA 0.01 100-
The other says WIMA 0.022 63 F4

So those values look quite reasonable for such a mod.

Switch        Total capacitance
up?             0.01 + 0.01 = 0.02 uF = 20 nF
center       0.01 uF = 10nF
down?       0.01 + 0.022 = 0.032 uF = 32nF

Not sure exactly which is up and down but the 32n (currently shown as down) is the one with the most bass.

In the centre position the behaviour has a high-pass cut-off slightly higher than the original CE-2B.
In the down? position the high-pass cut-off is about the same same as CE-2 (when Level set to full).
In the up? position high-pass filter cut-off is in between.

One small detail about how the filter cut-off works on that unit.  As you back-off the Level the filter cut-off is lowered. When the Level is centered the cut-off is about half that at full Level. The idea behind this in the original pedal is you can get away with letting more lows through when you back-off the level.  The impact of that is when you have the Level set below about 10 to 11 O clock you might find it difficult to tell the difference between the switch settings because the high-pass filter cut off is pretty low in all cases. (FYI:  It is possible to make the filter cut-off independent of Level with a slightly different mod but I won't go into details.) 

[aion]

Yep, the CE-2 mod as Rob mentioned.

They did lower the stock 12n capacitor to 10n, so the CE-2B mode will have slightly less bass than the stock unit but probably not noticeable. That would be the center position of the center-off switch. Then, one position of the switch is CE-2 mode (10n + 22n = 32n, close enough to 33n) and another position is in-between (10n + 10n = 20n).

This is a pretty common mod since the CE-2B is so much cheaper than the CE-2 but they are almost identical under the hood. I did basically the same mod to mine.