Hey all,
I have a very nice Boneyard pedal here that I'm loving so far, but there is this crazy high-pitched squeal going on any time I run medium to high gain (or use hot pickups).
I saw this thread, and my issue seems to be similar, though I haven't tried it with active pickups yet: http://www.madbeanpedals.com/forum/index.php?topic=2290.0
I think I've at least narrowed it to the input jack in some capacity. When it's on the highest gain setting, it squeals like a 12 year old girl at a Justin Bieber concert. If I reach inside the pedal and touch the tip of the input cable, about half the volume of the squeal disappears. If I do that AND touch the part of the 1/4" plug that's outside the enclosure at the same time, it goes away entirely. Literally nothing happens when I do the same to the output jack.
Any ideas, mates?
rofl... :D
Quote from: CK1 on October 14, 2011, 03:45:35 AM
When it's on the highest gain setting, it squeals like 12 year old girl at a Justin Bieber concert.
sig'd!
Quote from: nzCdog on October 14, 2011, 03:50:19 AM
rofl... :D
Quote from: CK1 on October 14, 2011, 03:45:35 AM
When it's on the highest gain setting, it squeals like 12 year old girl at a Justin Bieber concert.
sig'd!
;D
How about grounding the input jack? I know it should be grounding with your case, but maybe hooking up a wire from input sleeve to output sleeve might help? Im thinking the issue is ground related and there's a possibilty that somehow ur input is not being grounded properly...
-Kaleb
You might want to consider using shielded wire. It's an awfully high gain pedal, and shielded wire on the input and output may help reduce or eliminate the whine. Also, using a smaller value of gain pot will reduce unwanted oscillation. What values did you start with?
The pots are the same values as the MB document, so hopefully there's not an issue there.
I attempted to connect the input and output sleeves with alligator clips just to see, and it did nothing.
I'm actually having what appears to be the exact same issue 'audioware' is having as listed in this thread:
http://www.madbeanpedals.com/forum/index.php?topic=2290.0
As per his suggestion, I tried using an active pickup guitar and the squeal disappeared completely (even with all buttons on and every knob all the way up)! He mentioned trying shielded cable and it not helping, so I would guess that I'm in the same boat. So, now I'm really stumped...
Okay, that seems to be an input impedance issue then. Try raising R1 to 2M2 or 3M3 to see if it solves the issue with single coils.
Or--use a socket and try it with no pulldown resistor at all. That could be it.
Check that---hold on. Try this: socket R1 but leave it off. Now, take a 1k resistor and solder a wire to one lead. Clip the other lead short and stick that in the R1 hole (the one above the input). Now, disconnect the input wire from your 3PDT and instead hook the other end of the new wire to it. What you've done is eliminate the pulldown and substituted a 1k series resistor instead.
See if that works. If it does, then I will explain why :)
Sorry for the multiple messages.
Thanks for the reply, MB. I didn't have my soldering iron at my computer (I've been checking the pedal here), but I did have a bag of components handy, so I just started trying things with R1.
After a few attempts, it seems that if I put a 10k resistor in parallel with the 1M resistor that's already in R1, that the whine goes away entirely. I didn't have a free hand to strum my guitar to see if the frequency response changed, but it seems that R1 is the issue.
So now the question is, what's the best course of action? Since a 1M and a 10k in parallel are almost 10k anyway, shall I just swap that resistor? Or should I do your last suggestion instead?
Did you try it with no resistor? IIRC, I added R1 as an option, but looking back at the stock schematic there is a 1k series resistor at the input which I omitted. That 1k forms a low pass filter with the 330pF to ground, which might reduce or eliminate the high pitch whine.
It could be that no pulldown was used in the stock version to instead allow the Vb bias resistor (also 1M) to set the input impedance of the input gain stage. The added pulldown actually reduces the overall input impedance because it is parallel to the biasing resistor (since Vb is virtual ground). That's why I thought raising the overall value of R1 would bring it closer to the stock 1M input impedance.
Somewhere in here lies the solution. My guess is make into the stock unit by eliminating the pulldown and adding the 1k series resistor.
All of this was not a concern when I initially worked up the project, mainly because I had suggested using a 470R resistor off the inverted input of stage one instead of 47R and I suggested lower value pots. However, after releasing it some folks had mentioned that their builds were fizzy sounding at that 47R worked a lot better for them. So, given that the change from 470R to 47R increases the overall gain of that stage GREATLY, it isn't surprising that some other issues like this have come up.
Frankly, I don't understand how the Plexitone does so much gain without more noise and oscillation problems. The gain is so ridiculous I think it would cause a lot of problems with different set-ups. Maybe that's what we are seeing here...or maybe most people use humbuckers with this thing. I really need to get a guitar with humbuckers! It's also possible that the use of the charge pump instead of an actual transformer like the Plexi might be exacerbating the problem. But, the only way to test that is to completely remove the charge pump portion and try the thing with two batteries to create the +/-9v this thing uses to simulate the transformer's role more accurately.
Anyway, sorry for the rambling...I'm kinda jacked up on goofballs for a migraine today, ha ha.
You're a trooper for replying to this while you have a migraine!
I didn't try it with no resistor yet because I don't have that one socketed and I didn't have my iron handy at the time. I'm going to pull it this evening and see what I get (no extra sockets lying around, though, so I guess I'll just have to do a jumper wire).
I'll try that first and see what I get, but I plan to also add the 1k resistor as well. Is the only acceptable way to add it to do what you previously suggested?
Just to clarify, you mean attach the other end of the 1k resistor wire to the 3PDT, right? Since R1 is socketed (at least theoretically in my case), everything is still connected, then. Just making sure I'm understanding.
That's right. The 1k essentially replaces your input wire (for experimentation purposes). R1 is connected between the input and ground.
Removed R1 completely, but still got massive squealing. Then, tried removing the input line to the 3PDT and running a 1k resistor there from the first connecting point of R1, and no dice, still squealing.
Going back to my first attempt, I started changing resistor values for R1 just to see what I'd get. 1K alone worked great, except I lost at least 50% of my input level. I just tried running a 10K and 1M in parallel, and that works as before, with maybe 85-90% of gain level (and some loss of highs).
I'm going to experiment some more and see if I can come up with something, but feel free to chime in if you have any other ideas.
It seems the highest value I can use for R1 is about 14k before it starts squealing again. But I can tell that I'm still losing some highs, otherwise this would have solved it outright. Is there somewhere else in the circuit where I could make up some of the highs?
If you want to get the gain down some and still keep the same tone you can raise R5 to 100 ohms and change C5 to a 1uF cap. You can go even further and try 220 ohms with a 470nF cap. I would put R1 and R2 back to stock first. I also think shielded wire on the input and output is a must with single coils.
I should say that I've tried this with both single coils and humbuckers, and it's actually worse with humbuckers due to the increase in input level (as far as I can tell). If I'm desperate, I may try switching out R5 and C5, so thanks for the reminder about that.
Do you have a Klon type pedal handy? Run it in front and the buffer will help tame the noise quite a bit.
No Klon, but I do have some buffered pedals, so I can try that tomorrow. That may help some of the inherent noise of this type of high-gain pedal, but I don't expect it to do much to the other squealing which seems to be related to input impedance.
I would also use the lowest value gain pots that you can (and still get the gain that you want). I like a pretty low amount of grit on the crunch side and got good results from a 25k. The larger the pot the more gain and bass you will pass and it seems to sound less and less like an amp to me. Anything you do to reduce gain will help with squeal. I have been working with this circuit for months now and will post some findings, mods, and personal preferences soon.
OK, now this is really interesting.
I still have R1 removed, and nothing in it's place at the moment. So, I decided to try shawnee's suggestion of using a buffered circuit in front of the pedal (I have a Keeley-modded DS-1 that fits the bill) and the squeal is gone with no apparent loss of highs! One thing that surprised me is that the distortion level wasn't as high as I expected it to be (with everything all the way up, it was still fairly open-sounding). Going to probably replace R1 with a 1M as per the doc, and then see if it still feels the same. I might actually try to increase the gain with some combination of R5, C5, and the pot itself if I feel like I need more grit.
So, even though I said this a number of times already, just want to reiterate that I have used both single coils and humbuckers to try this, and found that an unbuffered signal will squeal when in medium to high gain settings regardless of my guitar (unless I use active pickups). My pots, clipping diodes, etc., are all the values listed on the Boneyard pdf.
Yeah, the low impedance output of the buffer is essentially taking the place of your jimmy on the pull-down resistor. You don't have a loss of highs because the buffer retains them. When you were using a low value pulldown instead, you kill input volume and lose highs.
So, maybe the key to making this work for most gear set-ups is having an optional buffer in front.
My test rig for this project was an 88 Strat and my trusty VOX AC4. I picked the pot values listed in the project doc because those are what gave me the gain without oscillation. But, obviously it's not a one size fits all solution.
Appreciate the explanation of why this is working, MB. I'm enough of a n00b that even if I think I know what's wrong with something, I often don't know how to fix it.
No justification necessary about the test rig, though. You can't possibly try all the theoretical combinations ahead of time. Plus, we've all got different setups, so I'm just glad that I can ask a question and get some decent answers from the more experienced members here.
Now the question is, what would be a good option for a stand-alone buffer for the beginning of my signal chain? I know there were some options floating around here on the forum (Klon buffer comes to mind), but does anyone have a recommendation/link? Thanks in advance.
I am using a Klon clone in front of my boneyard with great results (still openned up with nothing shielded and wires going everywhere). Maybe this would work for you:
http://www.madbeanpedals.com/forum/index.php?topic=2304.0
Quote from: shawnee on October 15, 2011, 08:07:42 PM
I am using a Klon clone in front of my boneyard with great results (still openned up with nothing shielded and wires going everywhere). Maybe this would work for you:
http://www.madbeanpedals.com/forum/index.php?topic=2304.0
That's the one I remembered seeing but couldn't find earlier today. Thanks for the link!
I've been playing this thing on and off throughout the day, and I just can't get over how open and big it is. Great, great pedal, and surprisingly amp-like (that term is overused, but I think it fits here).
I agree, this pedal is THE best Marshall in a box to date. I have been working on mods like adding treble mid and bass for a while now. It sounds even better and more open at 24v. If you have a TC1044 for your charge pump and not the MAX1044, you can just put 12v in and it will work fine. The MAX chip can't take it. I am also trying to be able to put in the normal 9v and get 24v internally. It can be done with two TC1044's easily but I trying some other layouts that I have seen. This pedal is worth the effort.
I've been having the same issue however, it just started happening out of the blue. I may have changed pedal order without realizing it but, it is after a Boss PS-5 in the chain. I'll have to try different buffers to see if it goes away. Mine also has a slight "slapback" delay after higher gain notes, especially at higher pitches. That may just be short oscillation.
My question is: Does the original CM version have an input buffer? I'm wondering if that's what the difference is. I know most DIY versions of pedals take those out (usually a good thing).
Other question: With a good buffer in front, would it be theoretically possible to use bigger pots to get more gain? I like the openness of the pedal but need just a hair more gain on each channel (using with a clean Fender DRRI).
I am going to try switching out the MAXX for a TC1044 and slipping in the 150pF cap as well, just to see. I will probably redo most or all of my offboard wiring too, since it's not the greatest.
I had already ordered the pots and was ready to take it apart but, it started doing this last week.
J