Lemondrop?

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Lemondrop?

Postby drewl » 14 May 2013, 18:39

Did a search but didn't find any info on it here.

Anyone ever see one, open it up?
Supposedly it's similiar to the Jellyroll but uses a silicon transistor to drive a FET?
just looking for something different to build.

thanks.
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Lumpy's Tone shop Lemondrop?

Postby Nocentelli » 14 May 2013, 19:10

drewl wrote:Did a search but didn't find any info on it here.

Anyone ever see one, open it up?
Supposedly it's similiar to the Jellyroll but uses a silicon transistor to drive a FET?
just looking for something different to build.

thanks.


Weird :scratch:

I remember this well, I could have sworn there was a thread - Maybe it was a request that was never fulfilled so got deleted.
Anyway, I really liked the demo and was interested in building a workalike, but never got very far. However, I saved a description of the circuit from Lumpy himself:

Lumpy wrote:The Lemon Drop uses a similar idea as the Peppermill to push a JFET into overdrive,
but it does it differently and I didn't get the idea from the Peppermill either.
If the idea of overdriving a JFET is unique to ROG, then I guess I'm guilty.
The input stage on the Lemon Drop is a BJT, not a MOSFET.

It's practically the same as the 7 Series input stage simply biased for 9V.
Transistor is a BC108B rather than BC107s used in the amp.
As simple as that sounds, it's what makes the pedal sound the way it does.
The JFET is a 2N5457, similar stage setup as the Peppermill,
but that is so basic anyone could come up with that...
The tone control is set up like a range control on a Rangemaster copy.

There were 2 custom versions that were built with the 7 series tone stack.
The original prototype was a little more complex utilizing more features
of the 7 series preamp but it never quite got the sounds of the amp.


I've attached some relevant schems that I used as a starting point.
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Re: Lemondrop?

Postby Nocentelli » 14 May 2013, 19:12

[edit]removed ROG peppermill schem - you can get that from ROG website easily[/edit]
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Re: Lemondrop?

Postby Nocentelli » 14 May 2013, 19:37

Aha, the thread is over at DIYSB, that's why I can't find it here:

http://www.diystompboxes.com/smfforum/i ... 249.0;wap2
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Re: Lemondrop?

Postby Nocentelli » 14 May 2013, 20:58

mmolteratx wrote:absolutely zero commercial use allowed. If I find anyone selling these, I'll fly to your house and kick you in the nads. And you may or may not find yourself in trouble.
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Re: Lemondrop?

Postby drewl » 15 May 2013, 20:52

Thanks.

If I ever get the time I want to build a 7 series preamp to go with some tube power amps I have that are similiar to the 7 series output section.
Someday, before I die :D


I've run Thomas Vox preamps into the power amps and they sound pretty good.

Thanks again.
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Re: Lemondrop?

Postby Nocentelli » 15 May 2013, 23:42

No problem: I think the upshot is that the Lemon drop is just a single BC108c stage taken from the 7 series input and adapted for 9v bias, driving a single 2N5457. I couldn't get anything but farty fuzz, but I know nothing about biasing transitors. I'd love it if someone could suggest a suitable bias arrangement for the first BJT stage.
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Re: Lemondrop?

Postby sciencefriction » 01 Apr 2016, 15:20

Necro Bump. With Lumpy awol, has anyone thought about giving this circuit another look? Would be fun to build and tweak.
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Re: Lemondrop?

Postby Nocentelli » 01 Apr 2016, 15:36

sciencefriction wrote:....has anyone thought about giving this circuit another look?


If anyone could post gutshots, that would be great.
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Re: Lemondrop?

Postby sciencefriction » 01 Apr 2016, 16:00

Nocentelli wrote:
sciencefriction wrote:....has anyone thought about giving this circuit another look?


If anyone could post gutshots, that would be great.


I don't own one anymore, but here are some images I found online. Looks to be some variations between them.

http://imgur.com/a/BefGl

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Re: Lemondrop?

Postby MoonWatcher » 01 Apr 2016, 20:19

sciencefriction wrote:Necro Bump. With Lumpy awol, has anyone thought about giving this circuit another look? Would be fun to build and tweak.

How about starting with a Peppermill, substituting a bjt for q1, and changing component values as needed?

You could always get into the particulars with the tone circuit and biasing a 2n5457 instead of j201 as the tweaking progresses.

While I'm probably wrong, I don't think that q1 plays as big of a sonic role as q2 does. That said, a mosfet will have different gains, and a different input impedance, than a bjt will, so I think those will probably be the most significant differences.

So - depending on how much overdrive comes from the jbt/q1 itself, you could probably just start with any semi-standard configuration. Maybe something like a LPB-1 for the first round of tweaks? Or maybe the booster stage from a Big Muff? Or a silicon Rangemaster variation?

Even though it differs from the Peppermill, it seems like the same basic idea is the same - q1 is driving q2. Most of the "magic" should be happening at q2, I'd think.

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Re: Lemondrop?

Postby Nocentelli » 01 Apr 2016, 22:11

Thanks for the pictures!

It makes sense if we assume it's vero, but I can't figure how the gain pot works:

Image

That assumes the filter is between the two stages, and is a cap blend between the orange cap straight from the collector (under the drawn-on brown wire, presumably > 100n) and the ceramic cap below the BJT (small, 4n7 or something, direct from the large orange cap to the FET gate). That would imply the gain pot involves the far-left electrolytic. That works ok, but I can't then understand why the gain pot would use two separate wires on lugs 2 and 3 AND a "stopper resistor" from lug 1 to ground. I also don't see a resistor from FET gate to ground (would normally be 1M or so, no sign of one).

Schematic in the works
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Re: Lemondrop?

Postby sciencefriction » 01 Apr 2016, 23:15

If they hadn't recently become so hard to get, I would get another. I want to build one and see if I can get it to sound a little looser. There were a couple with a pre-gain knob added, but I've never seen guts for that version. It's a cool build, but yeah, I'm not sure what's going on there either. If one turns up for a good price I'll grab it again.
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Re: Lemondrop?

Postby randalp3000 » 01 Jun 2016, 17:50

New guy here, been lurking/learning for awhile. I've built 20+ tube amps and a dozen or more pedals.
Picked up a ZII last week to try and help this thread along.
Here are a couple picks to help get this moving. I did trace it to the best of my abilities. Could only read one of the electrolytics but measured the rest in circuit with a cap meter. Ceramics are marked 471 and 10J, blue cap is WIMA 3300 100-U, orange cap 4700k, red caps .022uF.
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Re: Lemondrop?

Postby randalp3000 » 01 Jun 2016, 17:53

Schematic I came up with. Feel free to double check resistor color codes
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Re: Lemondrop?

Postby Nocentelli » 01 Jun 2016, 18:29

randalp3000 wrote:Schematic I came up with. Feel free to double check resistor color codes


Excellent work, many thanks! Could you measure the voltage on the drain of the JFET?
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Re: Lemondrop?

Postby randalp3000 » 01 Jun 2016, 18:51

Q1
1 4.58vdc
2 .79
3 .2

Q2 JFET
1 4.84
2 .61
3

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Re: Lemondrop?

Postby drewl » 04 Nov 2017, 01:03

Very nice, I'll have try it.
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