Longshot, I know, but does anyone know if there is any reasonably easy way to modify the range of the Buttkicker's low-pass filter? It's adjustable from 40-160hz, and I'd be thrilled if I could change that to something like 10-40. Of course, I could always just put a low-pass upstream of it, but I'm assuming that the auto-on detection is upstream of the filter, so putting a filter upstream of that would significantly reduce its sensitivity.

Any ideas?

I not familiar with the unit but I assume the filter range is changed with a rotary pot.If so then changing the pot to one with a higher value(x2) will move the adjustment range lower.
Probably not but do you by chance have a schematic?

No, I'm afraid not. I could always try and contact Guitammer, though I'm not sure how receptive they'd be.

I too have wondered about potential mods for this amp.

The techs there are fairly quick to respond but they might not offer any help in this particular area.

If you can determine the value of the pot it will be written on it (ie.25k ohm).If it were replaced with one of twice the value that would change the adjustment range to 20-80hz.

I may try and see what they say. I'm surprised that they build this specifically for a product that's designed to add tactile feedback down to 5hz, and never considered that people might want to limit tactile feedback to lower than 40hz.

If you can determine the value of the pot it will be written on it (ie.25k ohm).If it were replaced with one of twice the value that would change the adjustment range to 20-80hz.
That's certainly easy enough to try. I've got a meter, so it shouldn't be too hard to figure out the range even if it's not labeled. I hadn't even considered changing the pot itself. :o

And if INCREASING resistance is what I want, then another option would be just adding a fixed resistor in series with the existing pot.

And if INCREASING resistance is what I want, then another option would be just adding a fixed resistor in series with the existing pot.
Yes you could, in fact they may already have a fixed resistor in series with it that you can change to a bigger value. :)

Edit:Alternatively you could increase the size of the capacitors in the filter stage.

Any more info on this idea?

I will probably experiement with this, but it may be a week or two before I have a chance.

I will be anxiously awaiting your findings. And thanks!

I realized that since the control is located on the front panel, that there might be a cable running from it to the rest of the circuitry. A cable would make it easy to insert a resistor in series, especially if the cables had some kind of connector. Since the BK amp is about the only thing in my cabinet that is easy to disconnect and take in/out, I decided to take it apart and see.

No such luck. The pot is directly connected to a small pre-amp board, and the pre-amp board is attached to the front panel. It was a little more than I felt like tackling without knowing for sure I'd reach my desired goals. I'll email Guitammer and see what they say.

I'll email Guitammer and see what they say.
It should be interesting to see how they respond.

Here's one pic i found of the internals in a review.
http://i61.photobucket.com/albums/h69/ecir38/buttkicker.jpg

I took a couple pix of the preamp board and the pot, but the card reader in my pc is being flacky. I'll see if I can get them up.

What is the slope of the lowpass filter 12db or 24db per octave?

It might just be easier to change the capacitors in the filter section instead of changing resistance values.
ofcoarse you would still need access the bottom of the circuit board to unsolder the stock caps and solder in the replacements.From the pic it looks like to get the board out you would have to remove the two control knobs on the pots and remove the locking nuts hidden behind them.

Ok, I finally got the card reader to work. :rolleyes:

I didn't bother resizing, so I'll just link to them instead. First a close-up of the pot:

http://home.comcast.net/~consumes/P1000743.JPG

And the entire pre-amp board:

http://home.comcast.net/~consumes/P1000747.JPG

There's actually two panels that the knob has to go through: the outer panel, and an inner one. It was just more bother than I felt like dealing with tonight.

Not really sure on the slope - I'll have to do some checking.

The pot is a dual ganged 50k unit.From this I would guess that the LP filter has a 12db per octave slope.The green caps one is labeled C 213 the other C219 look like they would be the ones in the filter section.

Sorry Darin for all the questions but what is the value of C213 and C219?
and what are the functions of the two switches?

Sorry Darin for all the questions but what is the value of C213 and the green one besde it?
and what are the functions of the two switches?
No need to apologize... I appreciate the interest and helpl! But I'm afraid I can't answer the question on the the caps. It's been put back together and back in service, and it's about bed-time for bonzo. But it's not a big deal to check it out another day.

As far as the switches: one enables or disables a fixed 25hz hp filter, and the other bypasses this low pass filter.

If one of the caps(C213 C219) is exactly twice the value of the other than they are most likey the ones of interest.

Ok, so anyway, I kind of abandoned this with no update. Sorry for that. I did email guitammer, and was dissapointed to see that they didn't reply. :( But once I got everything a little more dialed in, I decided the juice just wasn't worth the squeeze. Previously, before I got the BKs installed in the floor, and had only the Auras in my furniture, I had EQ'd the signal to the Auras with the spare BFD channel to be pretty flat and rolled off above 25-30hz. At that point in time, I was also powering the Auras with a cheap receiver (there is a point to all this :) ). So, the cheap receiver was powered on via IR as part of a macro in my remote. When I added the BKs, and also upgrade the power for the Auras to the Bash plate amp, I was presented with two new problems: trying to EQ both the Auras and BKs, with very different characteristics and attached to very different structures, with one BFD channel, and also no longer using the BFD as a lo-pass because I needed to pass as much signal to the BK & Bash amps for their auto-on circuitry, since they aren't IR capable.

So anyway, I figured using the built-in adjustable LP filters in each of them would do this for me, needing the BFD only for trimming. The BK having a bottom setting of 40hz, and the Bash of 50hz. I especially wanted the BKs limited because of their audible affect due to being attached to my floor. But as it turned out, the Bash was a bigger problem. The mid 40s peak of the Auras is so high that the 50hz LP on the Bash wasn't enough to tame it to meet my taste (I really don't like tactile much above the 20-30hz range).

I then looked at the modding the bash amp to lower ITS LP filter, but I decided it was just too difficult to get too. The pot is attached right to the board with six connections (since it has stereo inputs, and high pass outputs), and I decided I just wasn't that nimble at soldering to attempt it (and it wasn't immediately obvious which caps were the right ones, and they wouldn't have been much easier). So, in the end, I did a couple of big cuts with the BFD in the mid 40s to tame the Auras, which are wide enough to cause rising response down to 20hz. That also inherently took care of the BKs. I don't have quite the auto-on sensitivity I'd like, due to the cuts. Especially on the BK (the Bash's auto-on seems much more sensitive). But so far, it hasn't been a huge problem. If I'm playing something that I'd really want the floor shaking, the MV is usually high enough to get the amps on. :) The BK amp does, however, tend to turn on and off intermittently during softer viewing, like regular TV, but it's not a huge deal.

Wow complicated set up but thats the way us HT nuts like it.Im interested in adding some tactile transducers at some point in the future and would like your opinion.Which of the two do you think give the greatest effect,the BK's in the floor or the Auras in the furniture?

Always best to find a fix without messing with the electronics, but man that preamp board looks like it was populated by a drunken child!

Wow complicated set up but thats the way us HT nuts like it.Im interested in adding some tactile transducers at some point in the future and would like your opinion.Which of the two do you think give the greatest effect,the BK's in the floor or the Auras in the furniture?
Heh, well, if you think that's wacky, wait till I post the mod to my floor to let it flex better. :D Right now, I'm not getting good flex due to some bracing running right down the middle of my floor - I'm actually getting better effect from the Auras in the furniture. That being said, the BKs are definitely way more powerful - I think my current problem is structure related, not an issue with the BKs. There are two advantages to shaking the furniture directly: it's much easier to shake, and they don't produce much sound. Shaking my floor does produce audible output, because the entire floor essentially becomes a huge IB transducer. The furniture isn't really audible, since it's shaking in free space. The advantage to doing the floor is the ability to affect much greater area (so people on the floor feel it, or in extra chairs that are brought in), and you don't get any disconnect when you realize your butt is shaking, but your feet on the floor aren't. The best of both worlds is probably an isolated riser, but that's not practical for my room.

The Auras are also quieter by nature (besides the mounting differences). The BKs do have a slight rubbing sound as they operate, since they are a piston in a cylinder, while the Auras are built more like a speaker (they have a flexing spider, so no rubbing). And the Auras bottom much quieter - the rubbing sound of the BKs can't be heard over normal program material (only during testing with deep sine waves), but a bottomed BK is very noticeable during normal use.

In the end though, the BKs give you much more force. I would say it would take at LEAST five Auras, probably more, to equal the output of a single Buttkicker. And the Auras need a LOT of EQ to tame their mid 40s peak. Without EQ, they seem very buzzy. The BKs resonance is spec'd at 9hz, as opposed to 42, and it doesn't seem NEARLY as peaky as the Auras.

Always best to find a fix without messing with the electronics
Yes, and the fact that I accidently pulled a spade lug off of the Bash pre-amp board when trying to disconnect it from the shakers when I was considering modding its LP filter, then had a hard time getting it soldered back on properly, also tempered my desires to mess with these things any more. :D

Heh, well, if you think that's wacky, wait till I post the mod to my floor to let it flex better. :D
For gosh sakes man I hope you're not planning to cut out all of your floor joists. :D

Thanks for the reply.Im going to take a closer look at how I can set them up in my room.

Always best to find a fix without messing with the electronics, You Sissy Maries . :p That's part of the fun.

Hey I don't fear electronics, but anything with 120VAC iin the chassis that I don't have a schematic for gets lots of caution.

For gosh sakes man I hope you're not planning to cut out all of your floor joists. :D
No, nothing quite that severe. I didn't realize until I went down to the crawl space to install the BKs that someone, at some point in this house's 100 year history, had added some braces under the center of the floor (and didn't do a great job). It's not original, and none of the other rooms have it. I think a direct vertical floor to earth brace next to the shakers is limiting their effect, particularly in the lower frequencies. My intent is to remove those braces. But someone apparently felt they were necessary, perhaps the floor in this room was sagging for some reason. So I'm going to replace them with some additional support with more compliance. Think: big spring. :eek: If that doesn't help the performance of the BKs, at least my den will be able to double as an indoor trampoline when my little nephews visit. :D