Boss Bf-2 Flanger Noisy!!

[SnooP_Wiggles]

I got a boss bf-2 flanger, that is rather old (MIJ with green faceplate on bottom) - $50

Schematic here

Its rather noisy so I need some help with that

I read that opamps and FET/transister get noisy after a long time
I thought ofreplacing the 4558 opamp with a higher spec, less noisy opamp. Any recommendations for an easy to find opamp?  
Would the FETs need replacing? and if so what is a suitable substitute as I couldn't find 2SK30A at local DSE (dick smith electronics) Any other parts to replace that would reduce noise? (excluding bbd chips)

Oh and on another note, does anyone know of an article that explains which generations of various Boss pedals are regarded best (I have read that 1st gen bbd chorus/flangers sound best, and that later model sd-1 sound better than earlier ones that had NEC 4558 chip). I get a feeling that in most cases the "metal screw MIJ" on ebay is as bad marketing as the JRC4558D opamp

[smoguzbenjamin]

What do you mean by noisy? I mean one man's noise is another man's music So if it's doing the jetplane woosh-woosh that's what the pedal just does. Can you give a more accurate desription? My BF-2 is about 15 years old and I don't experience noise at all. Just flanging

[SnooP_Wiggles]

By noise i mean hiss (white noise). With all knobs turned back to none (ie no change in tone), there is a quite noticable increase in noise floor (hiss) between effect on and bypassed.

[smoguzbenjamin]

It's probably in the switching then, if the noise is also there when the effect is disabled. Maybe the FETs do need replacing :? Jeez that's a shitty job...

[SnooP_Wiggles]

No you misunderstood (sorry bad explenation again), by bypassed i mean using the footswitch on the boss bf-2 to turn effect on and off

[smoguzbenjamin]

Yeah that's what I mean, the effect is bypassed, therefore disabled. I never said it was true bypass

[SnooP_Wiggles]

(double post ignore)

[SnooP_Wiggles]

But signal goes through the FET whether effect is on or not. By bypassed i thought you may have regarded that as taking the pedal out of effects chain. Im confused..

[smoguzbenjamin]

When an effect is not on it is generally referred to as bypassed That clears up that matter.

What a boss FET flip-flop does is turn the wet signal on and the dry signal off and vice versa by changing the conductiveness of a FET. If there's hiss and you can't think of any other cause (like power supply hiss), then your FETs in the signal path are likely to be degraded. There's not one FET but two

[SnooP_Wiggles]

Ok, but I can think of other potential causes, than just FETS.
Deteriorating caps, ageing opamps/transisters but I am hoping for some information on what components would add the most noise (due to age and/or quality),  I dont want to replace every component on the pcb. All help apreciated thanks!!!

[smoguzbenjamin]

Well you won't have to replace every component, the whole problem is that there can be a million different causes of noise. Try using the audio probe (I think it's at www.geofex.com) and trace where the noise is originating. Then replace that component.

[SnooP_Wiggles]

Heres some info that might help.. I found that with all knobs to full left (7oclock), there is considerable noise. dial the manual knob to 12 oclock and most of the noise disappears (still a fair bit, but it is an analog effect). Is this meant to happen??

[jplaudio]

I got a boss bf-2 flanger, that is rather old (MIJ with green faceplate on bottom) - $50

Schematic here

Its rather noisy so I need some help with that

I read that opamps and FET/transister get noisy after a long time
I thought ofreplacing the 4558 opamp with a higher spec, less noisy opamp. Any recommendations for an easy to find opamp?  
Would the FETs need replacing? and if so what is a suitable substitute as I couldn't find 2SK30A at local DSE (dick smith electronics) Any other parts to replace that would reduce noise? (excluding bbd chips)

Oh and on another note, does anyone know of an article that explains which generations of various Boss pedals are regarded best (I have read that 1st gen bbd chorus/flangers sound best, and that later model sd-1 sound better than earlier ones that had NEC 4558 chip). I get a feeling that in most cases the "metal screw MIJ" on ebay is as bad marketing as the JRC4558D opamp

Look here for some general improvements you can make to Boss pedals:
http://www.ne.jp/asahi/bdx/info/bdxtech/
The metal screw in and of itself doesn't tell you anything about the internals of the pedal but it CAN indicate the approximate age of the pedal(if it is the original screw). How long before someone on ebay tries selling "metal screw" DD-2's :lol:

[Mark Hammer]

The "first generation" Boss flanger is the BF-1.  I have one and it is still noisy.  On the the other hand, it runs off a 12vdc supply (NOT 9vdc like the chassis says, but 12vdc like the factory manual says) so that there is a little more headroom and tolerance for bigger signals, hence a slightly better S/N ratio.  It uses a different BBD (SAD-1024) with wider sweep capabilities than the one used in the BF-2 (MN3207).  It also has a number of other design differences.  Not exactly an A/DA flanger, but still better than a BF-2 in some ways.  The 12vdc is NOT what makes the difference between a BF-2 and BF-1, but if you own a BF-1 and have always used a 9v adaptor because it said so on the chassis, use a 12v supply and you'll hear a noticeable improvement.

I'm not sure why FETs and op-amps *would* get noisy over time, unless it was due to to the increased risk of some sort of user-induced damage that would accumulate over time.  Time itself does nothing to these components in the same way it might to older style capacitors from the late 50's.  My sense is that your advice comes from folks who either don't understand things or else don't explain it well.

Flangers are inherently noisy pedals, but there are a few things you might do.

1) IC1 (the 4558 closest to the connecting wires side of the board) is *always* on, so it provides the constant hiss background against which flanger/delay-path noise is added on.  If you can get in there and replace this chip without damaging anything do it (and I would suggest adding a bit of solder to each pin on the copper side before you attempt to unsolder it, making sure to wait a bit for it to cool down in between heating each pad for solder removal and doing the next pin).  A commonly available replacement might be an NE5532 or LM833, although there are other higher-priced chips with better noise specs like an OP-275.  None of the other chips will have any impact on noise levels when in bypass mode.

2) There are a number of resistors that are also in the signal path and *always* so, whether in bypass or effect mode.  You could consider swapping these for lower-noise metal film ones if you are desparate for even more hiss reduction.  These would include: R1-through-6, R28, R30-through-32.

3) It is possible there is a lower noise replacement for Q1 (2SC732) but I don't know what it would be.

4) If you are assured that you will never ever feed this pedal with something that has a DC offset, you can remove C1 (.047uf) and replace it with a fixed wire link.  That will also reduce some input noise.

5) If you don't mind some loss of high end, you can also consider upping the value of feedback capacitors C4 and C22 from 100p (which gives a rolloff at 33khz) to 330pf, which will give a rolloff around 10khz.  That will trim some hiss as well.  If that's too much treble to sacrifice, add another 150pf cap in parallel to what's there already.  A combined parallel capacitance of 250pf in each spot gets you a rolloff at around 13.5khz which still retains as much crispness as electric guitars are likely to require.  This will have an impact on both effect and bypass mode.

[SnooP_Wiggles]

Thanks a lot, I'll try some of them and see if it makes much of a difference... btw is there any way to date a Boss pedal??

[smoguzbenjamin]

There is a number printed on the bottom cover, but that could have been switched.

Hang on my EH-2 doesn't have a number on the bottom.... :x The PCB says EH-2 1/2 G292788700... Wonder what that means.... :?

[Mark Hammer]

There is really no point in dating one.  It is either design X or Y or Z, and that is evident from the components and chassis.  It is *possible*, for instance, that some pedals made a transition from an MN3007 BBD to an MN3207 at some point, simply because of changes in chip availability, but as 9v pedals, that would have meant that no differences between the two BBDs would have been exploited, in which case there is no point distinguishing between them for reasons other than repairs.

I have a chart of release dates for most BOSS pedals produced between 1976 and 1997 (not sure where I got it from on-line but you can send me your e-mail address and I'll happily forward it to you).  The BF-2 is shown as produced from mid-1980 right up until 1997 (where the chart ends).  The BF-2B was produced from mid-1987 to mid 1994.  The HF-2 Hi-Band Flanger was produced from mid-1985 to later 1994.  Differences between them were minor.  The HF-2 was in fact *identical* to the BF-2 except for use of a lower-capacity BBD that had the effect of shifting the delay range over without having to change anything about the clock circuitry.

Incidentally, I have a Washburn SC-7 "Stereo Chorus" pedal that I bought cheap.  The chorus sound was...okay I guess...but lacked a certain thickness.  I peeked inside and found it used a 256-stage MN3209 chip.  These are pin-for-pin replaceable with the MN3207 (as are the MN3240 512-stage chips used in the HF-2), which is a 1024-stage chip.  I swapped them and am much happier with the sound.  I also drilled a little hole, stuck in a toggle and did a clock mod to derive 2 ranges/modes like the Zombie chorus.  Sounds much better, and I ended up with a spare chip much better suited to flanging.

[SnooP_Wiggles]

you got pm!

[Chousy]

...

2) There are a number of resistors that are also in the signal path and *always* so, whether in bypass or effect mode.  You could consider swapping these for lower-noise metal film ones if you are desparate for even more hiss reduction.  These would include: R1-through-6, R28, R30-through-32.

...

Which other resistors in the signal path do you consider are critical for changing to metal film for noise reduction?

[ElectricDruid]

+1 agree with everything Mark said.

Ultimately, flangers are noisy. The MN3207 datasheet gives a Signal/Noise figure of 73dB for the BBD. That's about the same as a cassette tape. And then we add feedback/recirculation, and feed that noise back into the input...so it's no wonder it hisses.

The change in the hiss level as you adjust the manual knob with everything else turned right down is interesting. You're getting more hiss when the clock is lower in frequency, and less when it is higher. That's what you'd expect, but it suggests the noise is (at least partly) clock noise from the BBD.

There's no BBD output balance trimmer on the BF-2, but you could try adjusting the Bias trimmer. If someone's mucked about with it and it's a bit off, it might be noisier than it needs to be.

HTH,
Tom