Questions about Frost drive AKA VFE Ice Scream

ErickPulido

Active member
Hi first time posting here, I was wondering about this PCB, but the dual C10k and W1M (edit it is D1M) potentiometers are not easy to get,
has anyone build one and sub the pots?

The description of this pedal makes me wonder how nice will make high gain amps into meltdown.
 
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You may try shooting a message to Peter at VFE to see if he has any stock left, he’s really nice about this kinda stuff.
 
I would make the Dual C10k if Peter doesn't have any. I bought the cheap Tayda pots and picked the wafers I wanted. It is pretty easy requires some pliers and a steady hand.
 
I would make the Dual C10k if Peter doesn't have any. I bought the cheap Tayda pots and picked the wafers I wanted. It is pretty easy requires some pliers and a steady hand.
I am not that good with my hands that would be my last option, already saw how to do it, thanks
 
I just finished a Frost Drive build. I'll post some pix in the Build Reports forum over the weekend.
I corresponded with Peter Rutter. He has some residual stock, but the C10K duals he has are 9mm and won't fit the pad pattern on the Frost PCB.

Here's the thing about the MID pot... rev audio (C taper) is the wrong taper for this circuit because the MID pot is wired backwards. CCW rotation makes the frequency of the mid hump go up; CW rotation makes it go down. As designed, the MID pot does not space the tuning out evenly, the top half of the rotation makes essentially no change in the tuning and the bottom half is too sensitive, especially near zero. See the simulation results below. Actual operation agrees. Two options:
1) Use an A10K dual, they're much easier to find. The rotation will still be backwards, but the tuning will be spread evenly.
2) This is the one I chose. Use a C taper pot and wire it backwards. If you want smooth tuning and normal rotation (CW makes the frequencies go up), that's what you have to do. It's actually pretty easy. Tie pin 1 on each gang of the pot together. No need to connect pin 1 to the board. Tie both pins 2 together and connect them to one of the pin 2 pads on the board, doesn't matter which. Connect each of the pin 3 terminals on the pot to the pin 1 terminals on the board, separately. If you think this sounds crazy, take a look at the schematic and you'll see why it works. We still have the problem of obtaining a C10K dual. I solved it this way: C100K duals with solder lugs are available from Pedal Parts Plus. There is nothing magic about 10K pots. Any reasonable value could be used as long as C3, C4, R4 & R5 are scaled accordingly. I made the pot resistance 10x bigger, so the impedances of the other 4 parts had to scale up by 10x as well. That means R4 & R5 are now 10K, C3 is 4.7nF and C4 is 12nF. Note that the PCB silkscreen and the schematic both have typos for C3. The BOM is correct (47nF). You can find the VFE Ice Scream schematic on MadBean's website. It has the same reverse rotation / wrong taper issue, but it does have the correct value for C3.

I used A1M for the DRIVE pot, it works fine. B1M will make the bottom end of the range too sensitive.

Mid Boost tuning (as designed). Each curve represents setting the MID pot to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.
mid boost - as designed.PNG

Mid Boost tuning, corrected.
mid boost - fixed.PNG

Here's a pic of how I wired the MID pot.
MID pot wiring.jpg
 
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I just finished a Frost Drive build. I'll post some pix in the Build Reports forum over the weekend.
I corresponded with Peter Rutter. He has some residual stock, but the C10K duals he has are 9mm and won't fit the pad pattern on the Frost PCB.

Here's the thing about the MID pot... rev audio (C taper) is the wrong taper for this circuit because the MID pot is wired backwards. CCW rotation makes the frequency of the mid hump go up; CW rotation makes it go down. As designed, the MID pot does not space the tuning out evenly, the top half of the rotation makes essentially no change in the tuning and the bottom half is too sensitive, especially near zero. See the simulation results below. Actual operation agrees. Two options:
1) Use an A10K dual, they're much easier to find. The rotation will still be backwards, but the tuning will be spread evenly.
2) This is the one I chose. Use a C taper pot and wire it backwards. If you want smooth tuning and normal rotation (CW makes the frequencies go up), that's what you have to do. It's actually pretty easy. Tie pin 1 on each gang of the pot together. No need to connect pin 1 to the board. Tie both pins 2 together and connect them to one of the pin 2 pads on the board, doesn't matter which. Connect each of the pin 3 terminals on the pot to the pin 1 terminals on the board, separately. If you think this sounds crazy, take a look at the schematic and you'll see why it works. We still have the problem of obtaining a C10K dual. I solved it this way: C100K duals with solder lugs are available from Pedal Parts Plus. There is nothing magic about 10K pots. Any reasonable value could be used as long as C3, C4, R4 & R5 are scaled accordingly. I made the pot resistance 10x bigger, so the impedances of the other 4 parts had to scale up by 10x as well. That means R4 & R5 are now 10K, C3 is 4.7nF and C4 is 12nF. Note that the PCB silkscreen and the schematic both have typos for C3. The BOM is correct (47nF). You can find the VFE Ice Scream schematic on MadBean's website. It has the same reverse rotation / wrong taper issue, but it does have the correct value for C3.

I used A1M for the DRIVE pot, it works fine. B1M will make the bottom end of the range too sensitive.

Mid Boost tuning (as designed). Each curve represents setting the MID pot to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10.
View attachment 1672

Mid Boost tuning, corrected.
View attachment 1673

Here's a pic of how I wired the MID pot.
View attachment 1678
Don't know how I missed this, Thank you so much Chuck, I'll build one soon with this mod
 
Take a look at my post in the Modifications forum.
Wiring the diode mod is a little tricky. I screwed it up on the first try. If you follow my instructions, it will work. If you have questions, feel free to ask.
 
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Take a look at my post in the Modifications forum.
Wiring the diode mod is a little tricky. I screwed it up on the first try. If you follow my instructions, it will work. If you have questions, feel free to ask.
Thanks I am still waiting for the PCB it takes forever to get to Mexico
 
OK boys and girls, let's get this straight for the "paint by numbers" crowd . . . a simple recipe for getting the thing to work as basically intended 1) sub a dual A10K for the MID control pot, 2) sub an A1M for the DRIVE pot, 3) leave C3, C5, R4, R5 as spec'd in the BOM?? MID control will work "backwards". That do it???

Chuck B, does this also address your comments re: the "corruption" of the MID control as referenced another post or is that yet another matter for consideration?
 
First of all, you should be using the 9-1-19 rev Build Docs. The earlier rev had a typo in the parts list & schematic.

Everything you says is correct, that is the simplest solution and the only downside is the MID pot rotation is backwards. The backwards rotation in combination with the wrong taper is the corruption to which I was referring.

It is critical for the MID pot to have a good ground to the case. My enclosure was thoroughly powder coated inside and that prevented the MID pot from grounding properly. I had all sorts of intermittent problems until I scraped the paint off of the inside of the enclosure around all of the pot and 1/4" jack holes.
 
Everything you says is correct, that is the simplest solution and the only downside is the MID pot rotation is backwards.

There's no need to sub the MID pot anymore, the PCB has been updated so the C10K behaves as it should.

You can tell if your PCB is the new revision by looking on the back just below the "PCB175" text. If it says "Rev2" or newer you have the updated version. Since you just ordered yours (Mike) it will definitely be the updated version.
 
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