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MoonWatcher
Bronze Member
USA
98 Posts |
 Posted - 06/25/2008 : 05:25:51
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Sorry if this has been covered before and I'm just not using the search feature correctly.
Does anyone have a complete set of tweaks for the BD-2 that they're happy with?
This is a ped that I could go back and forth with until the end of time and still not be satisfied with the results.
My current mod list is:
R29 - 10K
R27 - 10K
R26 - 10K
R9 - 10K
C21 - 470 pF ceramic
C20 - 220 pF ceramic
C8 - 470 pF ceramic
C23 - asymmetric LED clip pair
C25 - asymmetric LED clip pair
C26 - .047 uF MF
C34 - 1 uF tant
C27 - .1 MF
C9 - .047 MF
C100 - .1 MF
C101 - .022 MF
C28 - .1 MF
D7-D10 - 1N400X pair
D3 - 1N400X
C17 - remove
C18 - remove
C16 - remove
plus a whole slew of caps upgraded to MF...
I constantly go back and forth with this pedal - brighter/darker, more gain/less, etc. The circuit doesn't seem to favor any one particular tone - the ped almost takes on an identity crisis when you start swapping stuff!
I know that Keeley replaces all of the 10 uF e's in the bypass chain with NP's, most ceramics get swapped for SM's, and that he loves to play with C100 - first with a .033 and then a switchable .068. He also goes to asymm. clipping somewhere in the circuit, IIRC...
I just can't seem to find a good comprehensive list of tweaks that will push the pedal into one defintive direction.
Does anyone have their own brew or a link to a few? |
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zentropa
Gold Member
USA
837 Posts |
Posted - 06/25/2008 : 05:31:24
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quote:
This is a ped that I could go back and forth with until the end of time and still not be satisfied with the results.
i've never owned a BD-2 for longer than 3 months because i've never found it sounded good through nearly any rig.
the only time i used it for a consistent stint was using it as a slight boost through a twin reverb. |
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Sixbladeknife
Bronze Member
69 Posts |
Posted - 06/26/2008 : 07:47:48
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| I have an Indyguitarist Brent Mason modded BD-2 and I love it. I also had the Keeley modded version which I didn't like at all. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 06/26/2008 : 15:33:04
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| Hmmm... is the "Brent Mason" mod something that can be shared here? |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 06/26/2008 : 20:56:43
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quote:
Originally posted by Laurie
Hmmm... is the "Brent Mason" mod something that can be shared here?
Doubtful - I believe it was the basis for Brian's "Hot Wired" pedal for Brent. |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/04/2008 : 23:13:29
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Well, 2 months later, and still whacking at this thing...
This is the most confounding little box I've ever been tormented by.
I swap some parts, give it a listen, swap some more parts, tweak things, go get coffee, tweak some more, listen more...
...When I think I'm happy and button it up, I come back to it later on to find that it still isn't right. It has fantastic note articulation that isn't in most of my other peds, but it's always at the expense of much needed mids or bottom end. Also - I find that the circuit needs to be driven at least a moderate amount to sound decent. Too little drive and it gets dull (not muddy), too much and the treble spikes start...
The BD-2 is a cursed, cursed design, IMO. |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 09/04/2008 : 23:22:01
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quote:
Originally posted by MoonWatcher
Well, 2 months later, and still whacking at this thing...
This is the most confounding little box I've ever been tormented by.
I swap some parts, give it a listen, swap some more parts, tweak things, go get coffee, tweak some more, listen more...
...When I think I'm happy and button it up, I come back to it later on to find that it still isn't right. It has fantastic note articulation that isn't in most of my other peds, but it's always at the expense of much needed mids or bottom end. Also - I find that the circuit needs to be driven at least a moderate amount to sound decent. Too little drive and it gets dull (not muddy), too much and the treble spikes start...
The BD-2 is a cursed, cursed design, IMO.
Sounds like my experience with the MT-2  |
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DeFrag
Moderator
USA
3409 Posts |
Posted - 09/05/2008 : 02:13:27
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quote:
Originally posted by zentropa
quote:
This is a ped that I could go back and forth with until the end of time and still not be satisfied with the results.
i've never owned a BD-2 for longer than 3 months because i've never found it sounded good through nearly any rig.
the only time i used it for a consistent stint was using it as a slight boost through a twin reverb.
Do/did you ever like the OD-3? |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/05/2008 : 06:10:44
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quote:
Originally posted by Laurie
Hmmm... is the "Brent Mason" mod something that can be shared here?
Actually, it can be now! I found where Brian posted it on another site.
He doesn't do much at all to meet Brent's requirements:
C14 - .1uF
C17 - .01uF
C19 - .01 uF
C101 - .047uF
D3,D9,D10 - LED, D9 & D10 bypassed w/.001uF cap
C22 change from tantalum to film (I guess Brent doesn't care for the tone of tantalum caps, either!)
I also found out some other important info. There is a R/C network that basically forms a Fender BF amp's tone stack. It consists of C26, C34, C35, R37, R38, R50, and R51. Switch the 220 pF cap to 470 pF, the .1 cap to .022, the .047 cap to .022, the 15K resistor to 22K, and the 100K resistor to 33K, and you have the Marshall tone stack!
Apparently, the "big mod" is to replace all or most of the clipping diodes with LEDs.
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/05/2008 : 15:57:56
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Well, did the BM mod - no dice. Still sounds like a paperweight, IMO.
The clipping is way too grainy, even with the LED's in place. |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 09/05/2008 : 16:00:51
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Hi MoonWatcher
What about using back to back MOSFET's?
You seem to have tried almost everything else.
Regards Dr. Bob |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/05/2008 : 21:10:02
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Hey Dr. Bob -
I'm so thoroughly addicted to mosfets that I'm trying to keep an open mind and try other diodes.
I am convinced that part of the high frequency shrapnel that I'm hearing is coming from the Mitsubishi chip at the end of the signal chain, getting slammed by 2 pairs of FET's. I have some SIP8's on the way that I'll try in it's place, or I may end up bypassing it, altogether. I don't like that the op amp comes after the level control in this pedal.
I also have some Schottky diodes on the way that I hope will at least partially distract me from the mosfets... |
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Dr. Bob
Moderator
Australia
6593 Posts |
Posted - 09/06/2008 : 05:04:04
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Hi MoonWatcher
Schottky diodes, can be pretty good as well, some read as low as 0.1V on my Fluke DVM.
Keep in mind, that I have seen a mod on the OD-3B, that uses 3.3V zeners back to back, & according to my translation of the information.
There were a lot of favorable comments about the improvement.
On the subject of op-amps, oI don't know hoe far back you go (in a nice way) - but do you remember when we had to apply frequency compensating caps on all the early op-amps?
I know that they claim, that they have done this internally, from the 741 & on, but who is to say their selection of F.Comp Cap/s was the correct choice for audio applications.
I remember fiddling with the value of the F.Comp cap, & it did have some noticeable difference to the circuit.
The older op-amps had some god awful Slew rates, that have become part of the characteristics & tone, not to mention the reason these old pedals have become so collectible.
It's difficult to reproduce sh!tty slew rate.
We now have op-amps, where the slew rate, is faster than the speed of thought.
I have been postulation, as to what actually happens at the very top of the rise time on these devices.
Do they overshoot?
Do they introduce their own artifacts, on to the signal?
Is this possibly what we might be perceiving as top end harshness.
And is this one of the reason that really high-end desks & channel strips, are still made with discrete components?
There are many people in the recording industry, including Tech savvy muso's, that don't like op-amp designed buffers, pedals & other gear.
Not that we have a lot of choice these days.
Do we ask that they re-introduce the LM301 or LM308 or a similar generation of older op-amps?
Probably not, unless you are keen on building a truck load of old RAT & Dist+ pedals.
Apologies of my rantings got a little heady for some.
Regards Dr. Bob
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/06/2008 : 21:55:49
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Hey Dr. Bob -
Yeah, I'm old enough to recall externally compensating circuits like the LM308.
Someone posited that the modern chips allow for one to hear all of the little nasty artifacts that get smoothed over by the older slew ridden chips. I'd have to agree.
My longstanding favorite is still the TL072 that so many audiophiles love to poke and jab at these days. There's just something magical when the peaks hit the rails with that chip - wooly but still crisp thanks to a decent input impedance.
Yah - zeners are next up, as well.
I made some headway very late yesterday with the BD-2. The trick is getting those 2 pairs of back-to-back FET's under control. The "simulated Fender tone stack" seems to be the key to doing it, since you can increase the insertion loss, and dump some signal to ground. It allows you to kill 2 birds with one stone - you lose some of the top end hash, and fatten up the bottom as well, by carefully bandpassing the amount of push...
Since the BD-2 uses a dual ganged pot that brings up the two pairs of FET's simultaneously, you have to think about how each "end" will affect the output. It's a tough balancing act.
I think that the op amp at the tail end will either have to be run at unity gain, or bypassed altogether. I'm using R26 as a stopper, but can't exceed 100K or it just smothers everything. |
Edited by - MoonWatcher on 09/06/2008 22:07:40 |
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MoonWatcher
Bronze Member
USA
98 Posts |
Posted - 09/07/2008 : 07:41:17
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Some progress, at last!
It seems that the underpinnings of the circuit are mainly two components: R50 and R26.
R50 is too high to allow for fuller bottom end, and allow for some much needed gain cut, as a result.
The same goes for R26, only this time it's too low. By incrementally increasing it, it's both a gain stopper and it increases the effectiveness of the tone control (increases bass). If the bass gets too heavy but the gain drop is good, simply pull C19. You can also finesse it by playing with C101, but that cap is a PITA to get at.
While the simulated Fender tone stack seemed like a good idea, it just doesn't work with the clipping diodes, IMO. I've found that it's best to just pull C26 altogether, and play with the mids and bass parts of the R/C network.
It now is pretty clear that any other tweaks in the circuit can be very slight, at least mine are. Probably the most radical things that I did were to pull C17, C19, and C9. Most other values are pretty close to stock. I did push up some brights, but that's pretty typical for me. I stuck with the LED's, but some Schottkys will probably still go in, next week.
I hope this is helpful to someone! |
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 09/07/2008 : 08:01:22
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I am watching with GREAT interest...
So it has come down to two components:
- R50 in the bandpass network. Have to set up a mathematical analysis of that network to understand what's going on
- R26 in the post Q12 "light roll-off" filter (looks to be only a dB or two per octave roll off without doing the maths...)
To stop the bass roll-off around R26, maybe just pull both C17 and C19? That would send un-rolled-off signal to the tone circuit....
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BD-2 mods?
