Odd mod in a BD-2

[343 Salty Beans]

A guy from my dorm offered me 20 bucks to do a 'TS808' mod to his unmodded BD-2. Apparently, all it is is a replacement of the opamp with a JRC4558  , but I figured that since I have to pay off 800 dollars worth of car in three months, an extra twenty would not go amiss. I'd never heard of a BD-2 'TS808' mod, butI figured: opamp switch, how hard could it be?

I opened the thing up, and it's all a little strange. The thing that LOOKS like the opamp is one of those straight-pinned ones: 8 pins, all in a row. I couldn't get to the little numbers on the back of the thing, even when I shelled the whole board, jacks, pots, and all, out of the chassis. Could anyone tell me from BD-2 modding experience if they've even heard of this mod and which opamp this is in there?

[petemoore]

  I'd look for a schematic, then paint some new numbers on there...lol.
  Almost certainly a dual opamp, straightline, I'd look for a data sheet and find a pinout, V+ might have a little 100ohm or so resistor between it and the OA V+ pin, but by finding ground and V+ pins and comparing to the data sheet, you'll [now, I just assume and assure] be able to determine the correct pinout.
  Replacing a good opamp with a good one is bound to be an improvement, or a catastrophe, but I'd go after something else...20 bux is 20 bux I guess.
  I'd use a DIST+, but since that's not an option here, I'd use solder wick braid and 4558.
  I got an 8 pin out of a boss DS-1 without solder wick, and wrangled in a standard dual 8 pin OA, four per side, I wouldn't recommend it though.

[blanik]

yeah, it's a straight IC, it's a M 5218 AL
you can replace it with a NJM 4558 L (the straight version of the 4558) so you wouldn't need to rebuild the IC socket... not shure though if all pins match... check it out:

http://www.frigidworld.com/rich/M5218AL.pdf
http://www.frigidworld.com/rich/JRC4558D.pdf

the schem:

http://www.frigidworld.com/rich/bossBD2.gif

being an avid BD-2 user (owning TS, FF, FF, DS-1, etc... and always coming back to the BD-2... but it might be the Twin  ), so being an avid BD-2 user, i don't think it's worth the trouble changing the IC, the M5218AL is a fantastic chip (and probably better than the 4558..  ) but playing around with the diodes can get you somewhere else with the BD, i ended up changing most of the clipping diodes in mine to small 3mm LEDs... sounds a lot better now, there's also a cap change in the tone control that works fine...

here are some mods posted on the Keeley page, given to me by MartyMart, i only did the diodes and tone cap (didn't have time to do the whole cap thing but i'll do it for sure) but they really sound great:

C14/C18/C34 100n "metal film" caps
C36 10n "metal film"
C100 - tone cap, change to 33n to 68n choose value, I like 47n metal film

C21/C23 - 47PF silver mica
C27/C30/C32 - 220PF silver mica
C29/C31 - 470PF silver mica
C25/C20 - 100PF silver mica

C10/C28 47n metal film

C1/C6/C7/C12/C13/C15 all electros to 16v 10uf "tantalum" caps, these are all in the signal path
so tant's are way better at this high value.

D7/D8 remove and use a single 1N4001 diode across both sets of "holes"
D10 remove and use a 3mm red LED

R.

[jlullo]

blanik,
for the diode mod, what exactly do you mean by using a single diode across both sets of holes?

jonathan

[Barcode80]

BD-2 is not really anything like a ts-8, well, that is to say, it is about double the parts count. i've never heard of modding a bd-2 to a ts-808, but i agree that the bd-2 with a couple of small mods is a GREAT pedal on its own.

[markm]

BD-2 is not really anything like a ts-8, well, that is to say, it is about double the parts count. i've never heard of modding a bd-2 to a ts-808, but i agree that the bd-2 with a couple of small mods is a GREAT pedal on its own.

Agreed!
I always wanted to clone one but, damn, there's alot going on in there! 

[Barcode80]

i've got the schem and a pnp of the board if you want to clone and just leave out the switching mark!

[jlullo]

barcode, i sent a pm.  do you think i could get the schem and pnp from you?

[MartyMart]

The BD-2 isn't anything like a " TS " it's more of a booster with "some" drive , but
a few tweaks can get it sounding superb. ( Blues driver  )

Don't bother to change the IC, its doing a great job " as is"
Follow through the listed mods to get an even better booster and some quite serious
drive and volume when dimed !!
I like the fact that it's fairly fullrange tone through the pedal out of thr box.

[Barcode80]

so i guess we are basically telling you that your friend is obviously mistaken about any functional similarity to the ts-808. just build him a ts-808 and he should be just as happy. heck, probably happier as a modded bd-2 is SWEET!

[Dirk_Hendrik]

It's more that I'm afraid that within now and a few years replacement of the opamp in any pedal with a 4558 is going to be called "TS808 modded".

Similar to replacing 4 caps in any 4 stage phaser and calling it univibed because the values differ..

[jlullo]

for the diode mod, what exactly do you mean by using a single diode across both sets of holes?

[MartyMart]

for the diode mod, what exactly do you mean by using a single diode across both sets of holes?

There are 2 x diodes above each other mid board, part of the clipping section
take 'em both out and "straddle" across all four holes to connect a single 1N4001
just get the cathode/anode connection correct and you're done !

o-->l --o o-->l --o      = old setup 2x diodes                 o = board holes  --->l --  = diode
o------->l --------o      = new setup 1 x diode

[joelap]

Marty, would using 1 diode across all four connections instead of the two lower the clipping threshold?  IE, instead of clipping at 1.4V (1N4001 clips at 1.4 volts each, right?), it'll clip at .7V?  Will that increase sustain at all?

I spent weeks doing nothing but modding my BD-2 when I got a sound out of it similar to STP's "Core" album.  The only thing was missing was the sustain... it stopped sustaining single notes too early  Could that remedy it?  Or am I way off?

[MartyMart]

Joe, that mod increases volume, cuts down on the heavy compressed crunch of
2 or more 4148's, so would possibly compound your problem !
The unit will "clip" later if 4001/LED's are used for clipping, which will mean that
your "sustain" ( of solo distorted notes ? ) will be less, unless totally dimed on the
gain pot. ( still may be less )
For more of that try just a single symetrical pair of 4148's, but I dont enjoy that
sound so much from these kind of circuits.
Careful selection of diodes/LED's and the gain structure can yield what your after, but up to
the clip point will be greater, so more scope for pure boost or just a "touch" or grit
settings too.

MM.

[markm]

i've got the schem and a pnp of the board if you want to clone and just leave out the switching mark!

Yesssss Indeeeed.
I'd love that BC, can ya e-mail it or PM it to me?
Many, MANY thanks!!