Hello there,
I have a question about my grey MXR M117 Flanger.
I recently bought it second hand and find it a very cool fx, but when Im using it on my Marshall I can hear the internal clock clicking, even in bypass mode. (the clicking goes faster when turning the speed pot higher). Does anyone of you guys had the same problem and do you know how to get off of it? Also, the pedal sucks a lot of my tone away in bypass. Can this pedal be easily turned true bypass?
Thnx in advance.
Is what you hear a whining or a clicking? I used to own one of those flangers years ago (circa 1984) and couldn't sell it fast enough. I found the noise rejection on it very poor, and my chops and need to emulate Eddie Van Halen were both low at that time.
The MXR 117 uses a Reticon SAD-1024 as its delay chip. The SAD-1024 usually incorporates a trimpot on the board which balances out the two complementary outputs of the chips. When set right, it helps reduce clock noise (this assumes there is complementary clock noise in each output and perfectly balancing them produces cancellation). It can be the case that trimpots drift or get jostled over the course of 20 odd years (and odd they were! :lol: ), so your noise problem may be a trimpot tweak away.
Even so, I found the noise/clock filtering to be inadequate on mine years ago. A further description of the noise problem you face might help to suggest where to intervene in the circuit to make it go away.
It´s a clicking sound. If you see the flange effect as a wave with a top and a bottom, I hear a click when its on the top and on the bottom.
So you think it´s the trimpots on the chip. When I open the MXR on the back, where can I find the SAD-1024 and trimpots?
There is an image of the PCB on
http://www.modezero.com/mxr-flanger.htm
It might be useful.....
Eddie (MXR)
Well now that it isd identified as a peak-related LFO click, rather than a clock-related whine, I would say to steer clear of that trimpot.
There are two seemingly common causes of LFO-related clicking. One is imperfect decoupling of a floating ground (Vref) to the LFO, and the other is an imperfect floating ground.
Whenever a half-the-supply Vref is derived from the supply voltage, you need to decouple that derived voltage from the main supply. This is entirely analogous to having two devices plugged into the same wall AC supply regulate their own power so that sudden draws by one appliance don't impinge on the available power for the other.
The LFO for this flanger is the standard 2 op-amp type that produces a square and triangle waveform. Remember that this square waveform draws current as it suddenly swings high or low. That sudden surge is likely what you hear. The usual cure is to identify where the Vref is derived and have a cap to ground at that Vref input to the op-amp for the relevant chips to smooth out their respective "local power supplies" so that sudden draws from one don't affect others.
One of the other things that came up in discussions of the Zombie Chorus was that when the Vref is not appropriately centred (e.g., not 4.5v with a 9v supply), the large swings on one side of the LFO waveform can cause audible ticks/clicks. Providing a Vref that is as close to the midpoint as is easily feasible can remedy this.
I can see the SACD-1024 chip and both the trimpots, but somehow, the trimpots on mine Flanger are soldered. Which one of the two trimpots regulates the clock?
There is an image of the PCB on
http://www.modezero.com/mxr-flanger.htm
It might be useful.....
Eddie (MXR)
@Mark: Do you know how to get a deeper swoosh out of an MXR?Like "Ain`t talking about love"?
Eddie
(shitty nick btw.....)
The only modification Eddie admitted :
GP Interview 1980
" It’s to make a good tone even louder. Some people get a sound like an amplified AM radio. I like it to be like a nice home stereo amplified -- you now, the difference between tone and no tone. I have some other tricky stuff in my amps which I don’t even want to talk about because if someone reads it in the magazine they are going to hit up Jose, an old guy from Argentina who knows a lot of tricks and does stuff for me. He doesn’t want people to know who he is because he’s getting mobbed. He also puts little things inside my MXR stuff, like permanent gain controls that boost when I kick them on. I don’t even know what they’re called. They reduce noise and boost the signals"
PCB Flanger Doubler:
http://www.modezero.com/mxr-flanger-doubler-sbf-325.htm
Referencing the picture at modezero that is linked to, the trimpot to the lower left, just next to the blue and brown wires is for adjusting the DC bias. Best not to play with this unless there is currently aproblem of not getting a decent delay signal. The trimpot to the right of the SAD-1024, wedged between the pair of 0.1uf caps, is likely the one that is used to balance the outputs of the two paths through the BBD for maximum clock cancellation. The plastic one over by the big PS cap is for tweaking the clock. I am assuming, rightly or wrongly, that this is for adjusting the response of the HF clock to the incoming LFO waveform in terms of how it converts low to high-frequency, and does not set the delay range in the same way that the Manual control does.
The red mica cap just above the 4013 in the picture is likely the 62pf cap that sets the overall HF clock range. I am assuming this because in the schematic I have from Stellan Lehrberg's site, it is the only cap associated with the HF clock. That, plus the fact that itis in the right range for a HF clock, make it the prime suspect. Making it bigger will shift the overall delay range up (i.e., longer delay time possible = thicker, more chorus-like tone), and making it smaller will shift the delay time down (i.e., sweep starts "higher up").