# Grover drive question.



## Crispy (Aug 23, 2022)

Ive been wondering,do you think it would be worth my effort to add the missing 4 pots with jumpers in place of the resistors , two foot switches for each circuit and try to make this Grover Drive PCB a love pedal silicon Fuzz master/ Zen Drive  2n1?  i was thinking on the Zendrive side change R11(220k) to a 500k gain pot R12(4k7) to a 10k Voice pot . the Fuzz side change R1(33k) with a 100k blend pot  C2 (100nf) to 4n7 and replace R8R18/R9R19 voltage divider with a 250k volume pot . or should i just build my Grover Drive PCB stock and start another project with my idea?


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## swyse (Aug 23, 2022)

I thought about doing this with an order switch, because the opposite order is supposedly the 200lbs of gold pedal he makes. I haven't seen the 200lbs of gold schematic to verify so I don't know if any other tweaks happened. I think if you have any intention to use them separately it would be worth your effort, you could even mark on the enclosure where the "factory" settings are.


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## Crispy (Aug 23, 2022)

the more i look at it i think it would be kinda easy to pull off. i think the important part would be making sure i have marks on each of the extra pots showing me the stock value to run it in Dover drive mode.  i was not even considering an order toggle . now that you mention it i wonder what it would sound like.it would just be one extra 3pdt toggle switch ive got a bunch of those on hand i might as well add that too. it should fit in a 1590bb i hope. im going to give it my best shot i hope i dont mess it all up LOL.


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## MichaelW (Aug 23, 2022)

I just ordered this with my latest PCB order, um, because I'm a sucker for a "sale item" and it was only $4

What's the difference between the Grover and a Zen?


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## Crispy (Aug 23, 2022)

MichaelW said:


> I just ordered this with my latest PCB order, um, because I'm a sucker for a "sale item" and it was only $4
> 
> What's the difference between the Grover and a Zen?


that has me thinking of getting a couple more just to have on hand ready to build at that price . as far as i can tell other than the fuzz circuit on the input, starting at the first 470nf cap it seems to be the same as a Zen drive with the voice and gain nob set to  around 50%  with a resistor vs the normal pot. the fuzz circuit looks a lot like Lovepedals Fuzz Master, with what looks like the volume nob replaced with a voltage divider to better match the fuzz circuit output to the ZenDrive input.


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## MichaelW (Aug 23, 2022)

Crispy said:


> that has me thinking of getting a couple more just to have on hand ready to build at that price . as far as i can tell other than the fuzz circuit on the input, starting at the first 470nf cap it seems to be the same as a Zen drive with the voice and gain nob set to  around 50%  with a resistor vs the normal pot. the fuzz circuit looks a lot like Lovepedals Fuzz Master, with what looks like the volume nob replaced with a voltage divider to better match the fuzz circuit output to the ZenDrive input.


I just went and watched some demo's of this pedal. What was a passing curiosity in a marked down board is turning into a serious interest now hahah. I'm thinking about putting the Bias trimmer on a pot and exposing it. That way I can dial between a more Zen like overdrive or more fuzzy drive on the fly.


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## Crispy (Aug 26, 2022)

I may add another toggle for C2 so i can change between 4n7 like the Fuzz Master and the 100nf the Dover driver uses . so far ive split the two circuits Fuzz Master / ZenDrive added the missing pots inplace of the resistors the DD uses ,made them both true bypass and added a order toggle so i can see what it sounds like to run a Zen Drive into a Fuzz Master


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## MichaelW (Aug 26, 2022)

HAH, I'm working on mine right now too. Not nearly as complex as yours though


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## Crispy (Aug 26, 2022)

MichaelW said:


> HAH, I'm working on mine right now too. Not nearly as complex as yours though


Nice, good luck i hope it turns out sounding awesome . ill post some more pics here when i get it wired up maybe a short sound demo if im happy with it.


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## Robert (Aug 26, 2022)

swyse said:


> I thought about doing this with an order switch, because the opposite order is supposedly the 200lbs of gold pedal he makes.



I'm not sure how the confusion happened but they're basically the same circuit aside from the 100nF cap on the input.   The order is the same, although it will be interesting to hear them with the order swapped.

Some folks have mentioned oscillation at higher gain settings with the Grover, removing the 100nF seemed to remedy that.


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## swyse (Aug 26, 2022)

Robert said:


> I'm not sure how the confusion happened but they're basically the same circuit aside from the 100nF cap on the input.   The order is the same, although it will be interesting to hear them with the order swapped.
> 
> Some folks have mentioned oscillation at higher gain settings with the Grover, removing the 100nF seemed to remedy that.





swyse said:


> so like an opposite order dover drive?





Robert said:


> Ahhh you know, you're right.   I didn't even catch that.
> 
> There's a couple components different but that's basically what it is.



Someone said it was zen>ff and then when you said you're right I thought it was in response to one of us so I thought it was an opposite order dover confirmed, just a misunderstanding it seems.


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## MichaelW (Aug 26, 2022)

Crispy said:


> Nice, good luck i hope it turns out sounding awesome . ill post some more pics here when i get it wired up maybe a short sound demo if im happy with it.


Finished mine, wow! Really like this pedal. Build Report here...


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## MichaelW (Aug 26, 2022)

Robert said:


> Some folks have mentioned oscillation at higher gain settings with the Grover, removing the 100nF seemed to remedy that.


Yup, mine definitely does that at the extreme end of the gain range, but I'm talking 3-4 o'clock. 
Won't bother me since I'll never run the gain that high.


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## Chuck D. Bones (Aug 27, 2022)

Robert said:


> Some folks have mentioned oscillation at higher gain settings with the Grover, removing the 100nF seemed to remedy that.



I can see how that would happen, depending on what you're using to drive the Grover.  C2 is only appropriate when driving with a high-impedance source, like a guitar.  Driving the Grover with another pedal, especially one with a low output impedance, will drive the Grover bat-shit.  I'd ditch C2.


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## MichaelW (Aug 31, 2022)

I removed C2, wow big difference. I thought it was just a noisy pedal but with the headphones on the "noise" was actually oscillation that increased when you dial the gain up. Taking out the 100nf input cap as @PedalPCB and @Chuck D. Bones suggested makes it whisper quiet all the way through the gain range. @Crispy highly recommend you leave it out.


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## Crispy (Sep 1, 2022)




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## Chuck D. Bones (Sep 1, 2022)

Very clean build.  Wire routing is impeccable.

Three questions: 
1. How is the board supported?
2. Are those transistor bodies touching?
3. You changed Q1 & Q2 from Si to Ge.  This will alter the biasing.  How to you plan to deal with that?


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## HamishR (Sep 1, 2022)

That's an interesting question. I just had a look at the Grover schematic and don't quite understand it - no surprise there! I didn't know you could use PNP transistors like that. To my ignorant eye it would seem that the bias is controlled by the trim pot, the gain pot and R2. R4 plays a role obviously but as it's connected to the trimpot I would have thought that was negligible. Do I have this wrong?  And sorry for jumping into someone else's thread! I'm interested in how this works.


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## Chuck D. Bones (Sep 1, 2022)

Yes, you can build a FF "upside-down." That way you don't need a -9V rail to power a PNP circuit. You guys in Oz live in an upside-down world, so it should seem natural to you .  
Kidding aside, the first stage is a FF with the GAIN control implemented in a slightly different fashion.
Yes, the GAIN control & Bias trimpot can adjust the bias, but it's unclear whether they have sufficient range to accommodate the switch from Si to Ge.  Crispy will find out.  Turning the bias trim changes the bias on Q2 *and *the signal level going to IC1.1.  Crispy might need to adjust R2.


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## music6000 (Sep 1, 2022)

HamishR said:


> That's an interesting question. I just had a look at the Grover schematic and don't quite understand it - no surprise there! I didn't know you could use PNP transistors like that. To my ignorant eye it would seem that the bias is controlled by the trim pot, the gain pot and R2. R4 plays a role obviously but as it's connected to the trimpot I would have thought that was negligible. Do I have this wrong?  And sorry for jumping into someone else's thread! I'm interested in how this works.


I removed the 100nf Input cap from the Grover but there is still another 100nF cap amiss in that circuit I believe! 
Check out the 5lb Bag Fuzz, it's basically the same circuit, just 180 degrees!
I've built both and prefer the 5lb Bag any day!








						5lb Bag Fuzz - PedalPCB.com
					

Compare to Lovepedal 200lbs of Gold (Fuzz Side)




					www.pedalpcb.com


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## Chuck D. Bones (Sep 1, 2022)

When there is a Build Doc with a schematic, then we can talk intelligently about the 5lb Bag circuit design.

Tell us more about this 100nF cap that's allegedly amiss in the Grover.  I can't find it.


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## HamishR (Sep 1, 2022)

Maybe he's referring to the big blue cap bottom right which should be 100nF but appears to be bigger?


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## Chuck D. Bones (Sep 1, 2022)

If someone knows what C4, R8, R9, R18 & R19 are supposed to do, then please explain it to me.


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## Crispy (Sep 1, 2022)

Chuck D. Bones said:


> Very clean build.  Wire routing is impeccable.
> 
> Three questions:
> 1. How is the board supported?
> ...


the pcb is attached to the Fuzz pot and the volume of the Zen drive + about a dozen other spots with my jumpers bent at right angles.                     for the transistors i was planning on getting some clear heat shrink tube and put it around the body of each transistor to keep them from touching.   using germanium transistors forced me to adjust the Q1 biasing resistor R2 i had to drop it down 15k for my Q1 to hit around .7-.8v i didnt have to change anything for Q2 i was able to hit 4.5-5v with the trimmer , Q1Hfe is 84 Q2 Hfe is 140.                                                                                                 i have played a bit on it and it sounds really nice  but i need to go over the clipping section on the Zen Drive once more its not sounding like it did on my breadboard, i think i put my Bat 46 in the place i wanted a Bat 41 also im wanting to adjust a couple other values i thought i was happy with on the breadboard but not so much now .


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## Crispy (Sep 1, 2022)

Chuck D. Bones said:


> If someone knows what C4, R8, R9, R18 & R19 are supposed to do, then please explain it to me.


C4 is kinda odd, ive seen a few schematics show C4 going to ground as a low-pass filter not as is a high pass filter as PedalPCB has it . that change seemed to make the circuit more stable on my breadboard . but because i wanted to sepperate the two circuits i needed to keep C4 as a decoupling cap/highpass then added that 100nf low pass in parallel with R4 on the bottom of the pcb .i wanted to blend from FF tone to range master tone so i changed the C2 100nf input cap to a 4.7 and use the blend pot i added to go between the FF/range master tones   the R8R18/R9R19 is just a voltage divider. i think of it as a fixed volume pot. its to make the output of the fuzz match the input of the the Zen better so it doesnt go crazy and make a bunch of noise.


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## Chuck D. Bones (Sep 2, 2022)

I know they are a voltage divider, but it's unnecessary because you can get the same effect by lowering R4.  Or just jumper R18 & C5, delete R9 & R19, reduce R10 to 82K and you have the exact same transfer function with fewer parts.

Since you are splitting the Grover in half, now I see why you're doing what you're doing.  Consider making Q1 Si, it will make the bias much more stable.  Q2 dominates the tone because that's where the distortion is made.  Use a medium-low HFE transistor for Q1 or increase R3 to dial-in the bias.

I like the idea of 100nF in parallel with R4, it rolls-off the higher harmonics above 3.4KHz.  If that's too dark, then try 47nF.

Because of the feedback thru R3, a FF behaves differently than a Rangemaster.  Varying the GAIN will change the high-pass freq because the gain of Q1 & Q2 makes R3 proportionately smaller from an AC point of view.


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## Crispy (Sep 2, 2022)

HamishR said:


> Maybe he's referring to the big blue cap bottom right which should be 100nF but appears to be bigger?


that big blue cap sounded so good on my Breadboard i swear LOL , when i put the fuzz into range master mode it kept a bit more low end . now it seems its way way to much low end so im going to slim that 1u down to the recommended 100nf .


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## Robert (Sep 2, 2022)

Chuck D. Bones said:


> When there is a Build Doc with a schematic, then we can talk intelligently about the 5lb Bag circuit design.


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## Robert (Sep 2, 2022)

I think maybe @music6000 was referring to C3, which isn't on the Grover / Dover Drive schematics.

I can't comment on that, since the Grover was based on the Dover Drive schematic that has been passed around for years.

The 5lb Bag, however, is based on my personal trace of the 200lbs of Gold.


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## Chuck D. Bones (Sep 2, 2022)

Crispy said:


> that big blue cap sounded so good on my Breadboard i swear LOL , when i put the fuzz into range master mode it kept a bit more low end . now it seems its way way to much low end so im going to slim that 1u down to the recommended 100nf .


C4 & R9 make a corner freq at 13Hz.  If you can hear the difference between that and 1.3Hz, then your hearing is better than mine.



Robert said:


> ...the Grover was based on the Dover Drive schematic that has been passed around for years.


In that case I don't trust the Dover Drive schematic. 



Robert said:


> The 5lb Bag, however, is based on my personal trace of the 200lbs of Gold.


THAT schematic I trust.


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## Crispy (Sep 2, 2022)

i think the old Schematic on line that is drawn out with blue ink pen on graph paper was changed , the guy that wrote it up later came back and said he made a mistake when he traced it the first time that one cap C4 went to ground other than that it was exactly the same .its an easy fix tho.


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## Chuck D. Bones (Sep 2, 2022)

Once one error is found, the schematic loses credibility.  The schematics passed around on the various forums have little or no traceability back to the guy that traced it and the unit he traced it from.  Having traced dozens, if not hundreds, of boards over the years myself, I know how easy it is to get it wrong.  Manufacturers will update designs and not tell anyone, so the unit that was traced and the one we hear on youtube may not be the same design.


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## Chuck D. Bones (Sep 2, 2022)

So where does the BOOST switch go?  There are YouTube demos of a 4-knob version with a BOOST switch.


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## music6000 (Sep 2, 2022)

Chuck D. Bones said:


> So where does the BOOST switch go?  There are YouTube demos of a 4-knob version with a BOOST switch.


If you are referring to the 200lbs of Gold, Its a separate Boost Circuit.


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## Robert (Sep 2, 2022)

The 5lb Bag is only the fuzz portion.   The Boost is a separate circuit.


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## Robert (Sep 2, 2022)

The Boost circuit is just a simple opamp boost that comes after the fuzz.


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## Chuck D. Bones (Sep 2, 2022)

The Booster drives IC1.1?


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## Robert (Sep 2, 2022)

Chuck D. Bones said:


> The Booster drives IC1.1?



No, this comes after the entire 5lb Bag circuit.    It's just an independent clean boost on the output.


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## Robert (Sep 2, 2022)

I'll see if I can get my hands on an original Dover Drive so we can stop all this speculating.


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## Crispy (Sep 2, 2022)

Robert said:


> The Boost circuit is just a simple opamp boost that comes after the fuzz.
> 
> View attachment 31606


this whole time i thought it was an electra type in the front end. i almost tried to add an electra boost to the front of my Dover with a third foot switch , lol im glad i didnt do that. thats way different from what i was thinking. ill have to breadboard this to hear how it sounds in the DD. TY for the schematic , im surprised at how close the Dover drive is to the 200lbs of gold.


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## Robert (Sep 2, 2022)

Crispy said:


> im surprised at how close the Dover drive is to the 200lbs of gold.



I have this feeling that we're going to find that the Dover is _exactly_ the 5lb Gold circuit.... but that's just a wild guess.


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## music6000 (Sep 2, 2022)

Crispy said:


> this whole time i thought it was an electra type in the front end. i almost tried to add an electra boost to the front of my Dover with a third foot switch , lol im glad i didnt do that. thats way different from what i was thinking. ill have to breadboard this to hear how it sounds in the DD. TY for the schematic , im surprised at how close the Dover drive is to the 200lbs of gold.


No Surprises, Lovepedal has been building Hermida products for at least 10 years with Alf doing the circuit designs!


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## Crispy (Sep 2, 2022)

music6000 said:


> No Surprises, Lovepedal has been building Hermida products for at least 10 years with Alf doing the circuit designs!


i sure do love his circuits tho, i understand the criticism with his marketing but as a new person to electronics i think his simple circuits are some of the best sounding circuits ive made and really fun to adjust to change the sound.


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## Crispy (Sep 2, 2022)

update on my pedal , for some reason at the last moment when i was soldering everything i changed the 2n7000 for BS170 not remembering while they are pin compatible i had to flip it around . once i got that sorted the zen came to life with the most beautiful clipping . im really happy with this build. so much im going to do another as a gift for a friend .


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## swyse (Sep 2, 2022)

Robert said:


> I have this feeling that we're going to find that the Dover is _exactly_ the 5lb Gold circuit.... but that's just a wild guess.


Given that this is essentially just two circuits reused I wouldn't be surprised at all, throwing on a third circuit and renaming the product is very much on brand.


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## Feral Feline (Sep 3, 2022)

Really diggin' your build Crispy, it's the sort of mad-scientist stuff that gets my own cerebral juices going. 
Like when I saw a Blueberry OD with a Boost tacked on the end, I immediately wanted to have separate control of the boost and the ability to put it in front of the Blueberry. 

Wish I could wire as cleanly as you.

@MichaelW is responsible for me picking up one of these boards, and what lead me to this thread. Looking forward to building this thing.

Lots of other inspiring contributions to this thread/my future build. Many thanks to all.


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## MichaelW (Sep 3, 2022)

I tend to be responsible for the delinquency of many.....or so my wife keeps telling me.....


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