I'm building a pair of sealed subs using these components, actually they're complete except for final wiring. I'm trying to make sense of the TC parametric eq specifications here:

http://www.tcsounds.com/tc1000.htm

and the boost instruction given for the amp here:

http://www.partsexpress.com/pdf/300-752.pdf

Tech support at parts express was no help as they couldn't figure out their own instructions.

I've built the enclosures to the TC recommended dimensions.

Any help figuring out 1) how much boost to try to apply, 2) what resistor values correspond to that boost, and 3) where the heck the resistors are on the board (the numbers are covered by the resistors themselves) would be greatly appreciated!

http://www.avsforum.com/avs-vb/showthread.php?p=8235258&&#post8235258

The Bash amp you have lacks PEQ, of course, so the TC PEQ recommendations are not useful here.

I would use the formula from the link above, and change the highpass (aka bass boost, as Bash calls it) to something like:

Fc = 12Hz
Q = .9

EDIT: See my post below. Accurate.

See the three attached images

1) This image highlights the general area of the R17 and R18 resistors.
http://img235.imageshack.us/img235/5094/image1wh3.th.jpg (http://img235.imageshack.us/my.php?image=image1wh3.jpg)

2) This image shows the location of "LLR." The labeling of R17 and R18 is covered up by the resistors themselves. LLR is easier to find, and helpful in locating the resistors.
http://img168.imageshack.us/img168/1724/image2te6.th.jpg (http://img168.imageshack.us/my.php?image=image2te6.jpg)


3) Once LLR is found, look at the back side of the circuit board to see the relative location of R17 and R18.
http://img293.imageshack.us/img293/6313/image3aq2.th.jpg (http://img293.imageshack.us/my.php?image=image3aq2.jpg)

Once the resistors are found, the trick is getting them out and replaced.

With my limited experience desoldering on a circuit board (and with the very tight area for the operation), I found it easiest to heat the solder from the opposite side (as in the 3rd image).

With needle nose pliers, I took gentle hold of the the R17 near one of its points of entry into the circuit board. With this in place, I used my free hand to heat it up on the opposite side. When the solder became hot, I was able to slide it out with the pliers
(NOTE: It is very important not to get the board too hot. Only use enough heat to loosen the solder to free the resistor). I repeated that for the other side of R17, and again the whole process for R18.

I inserted the new resistors using a similar method. There was enough solder in the board to accept and take hold of the new resistors. Again this was done with pliers and by heating one entry point at a time. Respect the other components on the board.

I hope this is of help.

Ben

Willd,

Thanks for the link. I think I get values for R17 and R18 of 34k and 108k respectively. Look correct?

Willd,

Thanks for the link. I think I get values for R17 and R18 of 34k and 108k respectively. Look correct?

Pretty much. :)

Once the resistors are found, the trick is getting them out and replaced.
Ben, were you able to replace these with the pre-amp board in place, or did you remove the board from the amp? Now that I have mine, these are not nearly as accessible as I would have hoped. With R18 sandwiched between those two caps, it looks like it's going to be a pain to get out. :(

Ben, were you able to replace these with the pre-amp board in place, or did you remove the board from the amp? Now that I have mine, these are not nearly as accessible as I would have hoped. With R18 sandwiched between those two caps, it looks like it's going to be a pain to get out. :(

It was awkward, but I was able to do it with the board still attached. Removing the board seemed more daunting than the original task.

The trick, I found, was heating from the back of the board, as I described above, with a steady hand holding one end of the resistor with needle-nose. Try to position your yourself in a way that one hand can constantly give the resistor a small tug. As soon as the solder, warmed by the iron in your other hand, heats up enough, the joint should give in to your gentle tug, and one end of the resistor will be free. Repeat for the other side.


The Mills 12w MRA resistors I used as replacements were MUCH larger than the original 1/4w's. This was advantageous for the installation. Being so large, I didn't need to have my hands very close to the crowded area to get them in. I think it would have been much more difficult to use 1/4w, or even 1/2w, on the way in.

I have read somewhere that some people install the new resistors on the back of the board. I don't see why this would cause any problems as long as you ensure that nothing gets shorted out -- front side or back side.

I hope it goes smoothly for you.

-Ben

I have read somewhere that some people install the new resistors on the back of the board.
Yeah, I actually thought about doing that. It's too bad I need larger values instead of smaller ones... then I could just wire new resistors in parallel on the back of the board and not worry about taking out the old ones. :)

Ok Ben, I have to commend you for doing that with needle nose pliers. I just got done, and it wasn't easy! I just couldn't get pliers in there good enough to get ahold of the resistors. I ended up taking a very small screw driver, wedging it in between the resistor and the board, and gently pried it away from the board as I heated the leads on the other side (which I also had to bend with said screwdriver so they could go back through the holes). I don't know how you got larger resistors soldered back in from the same size. One of the ones I used was a 1/4 watt, and the other was a half watt, and even with them it was still a challenge for me to get those soldered back in on the BACK of the board.

I think I'm just getting too old. This is actually the first time I've ever had to take out my contacts to gain some near vision to work on something. :o

I don't know how you got larger resistors soldered back in from the same size. One of the ones I used was a 1/4 watt, and the other was a half watt, and even with them it was still a challenge for me to get those soldered back in on the BACK of the board. :o

Nice work Darin.

It could have been that since I was approaching from the inside, needing not to apply the heat and insert the end of the resistor in the same tiny spot, I was able to heat a larger surface area of the pin hole in the board, melting more of the existing solder, allowing for my larger resistor to slide in. It was a pretty tight fit, needless to say.

Glad you had success.

-Ben

If someone buys this amp and doesn't do this swap, what could happen and what are the odds of this happening? Bottoming out of the sub or ?? Thanks for helping me with my n00b question.

Also wondering, because i have everything i need to put my sub together. Except for the resistors i need to change. Just wondering what would happen if i didn't change them. Thanks.

Wow, old thread. If you don't change them, you will have a hump in response around the bass boost frequency (don't remember what it is, maybe around 30hz?), and response will drop off below that. That's fine for a high-tuned ported sub, but it wil prevent you from getting good response down to very low frequencies.