Master Volume Celsius Mod

[anevilspar7an]

I'm going to be building a highly modified Celsius + Cepheid combo build. One of those mods is a master volume on the Celsius preamp before going into the chorus, I read that someone just put an A500K at the end of the output buffer after R11. It seems a bit high, A100K sounds more reasonable. I would like to know if this is the correct way to go about it from someone with more experience.

 

[Feral Feline]

Here's where I'd start the monkey-shines on a breadboard...

Replace R14 with an A5k pot. R13 feeds the pot's lug-3, lug-2 is the new OUT, and lug-1 to ground.


Could also try A10k, A25k, A50k, A100k, but I'd start with A5k.



Further monkeying with gain (real gain, not the input-attenuator pot mislabelled as "GAIN"...

GAIN = R10 ... Could stick a B500k pot there wired as a rheostat, replacing R10, but in series with a 47k resistor. You'd get a bit more gain 547k and be able to lower it to almost buffer status.


More monkey-shines...
Replace R9 100k with an A100k pot, just like the R14 swap. Signal from C4 feeding the pot's lug3, output lug2 goes to the HI/LO-switch and lug1 to ground.

Caveat emptor — I've no idea about what I just said to do.

 

[anevilspar7an]

Here's where I'd start the monkey-shines on a breadboard...

Replace R14 with an A5k pot. R13 feeds the pot's lug-3, lug-2 is the new OUT, and lug-1 to ground.


Could also try A10k, A25k, A50k, A100k, but I'd start with A5k.



Further monkeying with gain (real gain, not the input-attenuator pot mislabelled as "GAIN"...

GAIN = R10 ... Could stick a B500k pot there wired as a rheostat, replacing R10, but in series with a 47k resistor. You'd get a bit more gain 547k and be able to lower it to almost buffer status.


More monkey-shines...
Replace R9 100k with an A100k pot, just like the R14 swap. Signal from C4 feeding the pot's lug3, output lug2 goes to the HI/LO-switch and lug1 to ground.

Caveat emptor — I've no idea about what I just said to do.

Sounds like some worthwhile mods. Another one I'm doing is using LT1054 instead of TC1044SCPA since I don't have any. Do I cut the trace between pins 1 and 8, or will the LT1054 be just fine with the frequency boost hooked up in this circuit?

 

[Feral Feline]

Sounds like some worthwhile mods. Another one I'm doing is using LT1054 instead of TC1044SCPA since I don't have any. Do I cut the trace between pins 1 and 8, or will the LT1054 be just fine with the frequency boost hooked up in this circuit?

I've been up for about 20 hours, can't think straight...I should be trying to get some sleep, so I'll endeavour to answer this over the weekend, but meanwhile...

Check out the Madbean RoadRage PDF, it may have the answer for you.

 

[Feral Feline]

Sounds like some worthwhile mods. Another one I'm doing is using LT1054 instead of TC1044SCPA since I don't have any. Do I cut the trace between pins 1 and 8, or will the LT1054 be just fine with the frequency boost hooked up in this circuit?

NOT FINE!

I looked at the RoadRage2019 doc, as well as some older RR docs... I believe you are correct that the connection between pin-1 and pin-8 of the LT1054 must be broken — and you may have solved why I had a melt-down on a pedal I built a year ago for a friend, given to him before I could test it (long-story short I had a flight to catch). I'll know in a few months when I fly back to visit my friend and trouble shoot that build; probably had pins 1 & 8 on the LT1054 connected 'cause that's all I had for a charge pump, though the circuit called for something else.

Back to your build.

So, yes, I suppose the way forward to continue with your Celsius build is to cut the trace if using the LT1054.

However, consider this:

The Celsius is a $12 board. — ($10.50 on sale right now).
The LT1054 is a $6 IC — (approximately, depends where you get it from and which version — $3.50 @ Tayda!)

Is the trace-to-be-cut on the Celsius clearly visible? Are there other traces close by that may get damaged? Ground-plane?
Are you willing to sacrifice the board and potentially some parts as well as the charge pump if drilling/cutting the trace goes awry?

If you've already built the board, killing it would mean even more time and money wasted while you order another board, charge pump and whatever other components couldn't be salvaged from the botched build.


Personally, to play it safe I'd order a TC7660SCPA or ICL7660SCPA; I suppose the TC1044SCPA is fine — but I've heard nothing but bad things about the MAX1044.

I'm not a gambler, but I have drilled through a few PCBs to interupt a trace, and IIRC cut a trace on at least one other PCB that required it.


Also, wouldn't hurt to get a second, third and or fourth opinion — I'm no expert on any of this power-business (hence my friend's pedal's melt-down).

 

[anevilspar7an]

The trace is easy and out of the way, haven't built the board yet. I haven't had any builds that needed the TC1044SCPA, but spent a pretty penny on several LT1054's when they were $2.50 USD.

 

[Nostradoomus]

It is safe to use the 1054 with pins 1 and 8 connected when it’s being used as a voltage doubler as it is in this circuit. No need to mangle traces.