Fatpants at 9v?

[junkemail86]

Would the Fatpants sound ok (or even work) at 9v as is, or would that require some circuit modification?  I only have 1 MAX1044 left, and it's going in the Plexitone!  Might be time to order some more...

Thanks!

[jimmybjj]

I don't know the answer to your question but if you use a socket it wouldn't hurt to try. Report back if you attemp it.

[bigmufffuzzwizz]

The Fatpants build is designed to run at 9v, but it can take up to 12v if you use the TC1044. I'm sure other chips can go up to 12v, but I recommend checking the datasheet first to make sure it can handle that much. Otherwise you'll be frying chips all day! I believe the purpose of increasing the voltage into the circuit is for "headroom" which helps the circuit from clipping/distorting. I still have yet to experiment with this. 
http://en.wikipedia.org/wiki/Headroom_(audio_signal_processing)

[jimmybjj]

I get the impression that he wants to try and run it without the 1044, maybe I'm wrong?

[bigmufffuzzwizz]

Yea I'm kinda confused by his question too. Too run it with no chip? 
I got a few ICL7660SCPA chips instead because the MAX1044 seemed a little pricey. If my understanding is correct, the chip is used as a charge pump. And I remember Jkokura saying it shouldn't have a noticeable audible effect which chip you use.

[stecykmi]

I think he wants to run the audio part of the circuit at 9v. I'll probably work, but it might clip rather easily.

[junkemail86]

Sorry for the confusion, but you guys are right: I'd ideally like to run the circuit without the MAX1044 charge pump, mainly because I think I have all of the other parts on hand.  Probably won't go down that road, but if anybody is interested in something similar, the Xotic EP Booster (9V) should have a similar sound although the circuit is different.  That schematic is available at FSB.

[jkokura]

I believe you can run it, but you would have to modify the pcb some to leave it out. It's not just as simple not including the chip.

Try breadboarding the boost circuit itself if you want to know want it sounds like.

Jacob

[jimmybjj]

I believe you can run it, but you would have to modify the pcb some to leave it out. It's not just as simple not including the chip.

Try breadboarding the boost circuit itself if you want to know want it sounds like.

Jacob

Why not? I'm still just a novice but it looks like to me it would to me, am i missing something?

Edit:
It does work removing the ic. I didn't have time to play with it much but it pass signal (but as we know, just because its passing signal doesn't mean it's working properly.) Signal was clean until the end of the fat pot where the sound became splatty/gated.

[jkokura]

That's precisely what I mean. You can run it, as I said, but it would require some modification to the circuit. Hence the modify the PCB statement, which I now realize may have been confusing - sorry. I simply meant that you might need to adjust some of the part values, or perhaps make some circuit changes. At that point, you've got something slightly different than the 'fatpants.'

Essentially, you're reducing the voltage in by eliminating the charge pump, so the voltage reducing diodes in series (D2-3) now lower your 9V in even more! So you need to compensate for the bias now being different, perhaps around 7.5V, which is what may be resulting in you splatty badness. It may be that if you adjusted the trimpot you may find a good sweet spot that's very useable.

In my opinion, the real value in a booster like this is the headroom, and more power in this circumstance equals more headroom. If the issue for you is a part that's just a few bucks and you should just get another one when you have the opportunity. If you are planning on using the MAX chip for your other project, then save up and get a second one when it comes time for that build, or perhaps think about another charge pump that's cheaper for this build now.

I say that, but I'm also the kind of guy who spends 1-200 bucks a month in parts, and has to lock up my garage for fear that someone will find my switch and pot boxes and walk off with them. For me it's as simple as adding a part into an already being made order. I realize that for others, a 7 or 8 bucks bill may not be worth it, but you can have a charge pump with shipping for that price and perhaps for as little as 4 or 5 bucks. If you think about it, that's really nothing in the world of expensive boutique guitar pedals.

Get a charge pump, it will erase all doubt, and you will have the wonderful goodness that is a Fatpants.

Check out this link also: http://cgi.ebay.com/Maxim-MAX1044-MAX1044CPA-Voltage-Converter-IC-DIP8-NEW-/370476677595?pt=LH_DefaultDomain_0&hash=item56422179db#ht_500wt_922 Max 1044 for 7.50 including shipping in the US. Look a little harder than I did (I spent 1 minute), and you should be able to find a better deal. If not, I'm sure someone here can ship you a TC1044 for 4 or 5 bucks if they have a spare.

Jacob

[jimmybjj]

awww...thanks for the excellent explanation 

[junkemail86]

Thanks a lot for the explanation!  I was planning on just putting it together on perf board without the charge pump portion of the schematic, but it's probably not worth it as you mentioned.  It may sound silly to some people but shipping time, not price, is my biggest obstacle when building pedals.  I can spare the few bucks for the part, but during med school my (rare) free time would come in spurts of a weekend or whatever every few months.  So if I didn't have a part on hand, the need to place an order and wait for the shipment would kill the project for me.  Now that I'm done, things are a bit better and I have a few weeks off before I'm back to the grind of 80+ hour weeks.