Friday, 29 September 2017

Lumpy's Tone Shop Lemon Drop/ZII/Series 7

Originally sold as the Lemon Drop, then the ZII, and now the Series 7.

Description of the Series 7 from the source:

Designed to mimic the unique overdriven tones of the rare Vox 4&7 series amplifiers in a small and easy to use stompbox.  An unknown amp to most, the 4&7 series amps were most famously used by the Beatles during the Revolver era and Jimmy Page on numerous tracks from the second Zep album.  Think Paperback Writer style of tones and, yes, Whole Lotta Love.

The 7 Series Overdrive captures the aggressive qualities of the solid state preamp found in the 4&7 series amps by using a pseudo hybrid setup consisting of a specifically selected silicon transistor for the first stage which adds a distinct bite and growl.  That pushes an FET stage into clipping adding some warmth, sustain and amp like dynamics to the tone and feel.  The end result is a highly effective emulation of the amp and a unique sonic blend that could be characterized as a "fuzzy overdrive."






As it's been pointed out there are some pictures with the 2.2uF coming off the emitter to ground as 4.7uF. I've seen pictures with 2.2uF as well, so I'm under the assumption that there's multiple versions as the pedal has changed names over the years. I changed the value of the cap so now there's 2 different layouts. With the 4.7uF cap the pedal should fatten up more compared to the 2.2uF. 


30 comments:

  1. Nice addition! Lumpy's makes great pedals.

    Q1 is BC108B

    You can replace the 6K8 resistor by a trimmer for biasing Q2.

    Voltages:

    Q1
    1 4.58vdc
    2 .79
    3 .2

    Q2 JFET
    1 4.84
    2 .61
    3

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    1. Ok call this verified! You must have been reading my mind Zach as i've been searching for a layout/scheme for this all week. Was working great then I saw zosotone's post and decided to check voltages which were spot on apart from the drain for the JFET (was initially measuring ~3.80v). Tweaked it with a trimmer to get 4.80v and it sounds great, really tight but hairy overdrive. Wouldn't say it sounds vastly superior to the voltage with stock 6.8k drain resistor but it's nice to have (i'm assuming) Lumpy's original voltages. Noisy as hell at the moment but should be fine when boxed. Thank you Zach and zosotone.

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  2. its works very well !! Used also BC108B hfe 280. Thanks

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  3. Thanks Zach! I tried tracing this one from pictures earlier this year. I don't know how I missed that schematic @ the usual place...

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  4. Replies
    1. yea. i forgot the one under the 22nF cap. my bad

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    2. +Zach, Just a quick word of THANKS for this site and all that contribute. I will only build a handfull of the pedals here, but I am amazed at the work and effort that goes into all the layouts here. Thanks for doing this!

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    3. Cheers man. Enjoy the builds.

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  5. Well I built this, managed to get the 2N5457 biased to 4.8V with a 6K2 resistor and it doesn't sound very good at all! It doesn't distort and just sounds clean and very bassy. I checked my BC108 and it's a BC108C - will that be the difference?

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    1. Typically BC108C, and any BC series transistor with a C suffix, is a high gain version. The letters denote gain ranges when sorting, A being lower, B middle, C high, while thrills with no suffix are inspected. I suspect, based on the one that verified the layout that you want a lower gain silicon transistor. Also, see if your voltages match what's been posted, and check for any errors.

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    2. Check the Collector voltage of the BJT too. You want it at about 4.5V as well. Also, try other Jfets - even though yours biased right, it could be a dud 2N5457.

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  6. I am in the process of breadboarding this before I decide to build it and would like a schematic. Anyone know where I can find one? Also, the 2 BC108s I have measure 691 and 782 hfe. Based on Zach's post above, a lower gain silicon transistor would work better. Any suggestions on other NPN silicon trannies?

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    Replies
    1. Schematic is in the usual place (FreeStompBoxes). Other NPN's: 2N2222, BC109B, 2N3984.

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  7. I had to socket the 6.8k resistor spot and use a 12k to get Q2 to bias to ~4.5 on my build but it sounds great now. Thanks for the layout and build advice everyone!

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  8. Got it working on my breadboard. I measured 5.7V on Q2 with the 6.8k resistor. Tried a 8.6k (5.0V) and a 10k (4.2V). I am reading 3.9V on the collector of Q1 with no change when I swapped out the 6.8k with the 8.6k and 10k. I have several other NPN transistors with lower hfe that I am going to experiment with. I also have a couple germanium NPN (2N388) with lower hfe's (65 to 195 hfe)that I am going to try also. Anyone tried a germanium transistor in this pedal?

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  9. Built this and there is a curious issue. I got between nothing and very poor fuzz when I used the 6.8k resistor - tried a few different BC108s, and realised they were too high gain. So,

    I replaced the 6.8k with a 10k trimmer and biased the Q2 drain to 4.8V and it sounds great!! well the fuzz sounds great but over the top there is a loud ticking - is this because its not boxed? I cut one leg off the trimmer to make it fit the two holes of the resistor - has this caused a grounding issue perhaps?

    Thanks

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    1. Hmm, about the trimmer, not really. The ticking (which I also believe is a grounding issue) must lie somewhere else, unless you missed some cut or there's a solder bridge somewhere nearby the trimmer.

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  10. Built it. Paired with my p90 lespaul this thing just barks! (instant vintage tone).
    6k2 resistor for the fet drain and a 410hfe ME 4003 for the silicon transistor. Lower gain transistors gaves above 5.30v collector readings; now is spot on the original.

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  11. This comment has been removed by the author.

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  12. Member Music6000 posted something interesting to try at the forum:

    "I have studied half a dozen different vero's of the original online & he definitely uses a 4U7 Electro from 2N5457 Source to Ground instead of 2u2. It also appears that he might use an 4u7 Electro instead of 2u2 from BC108B Emitter to Ground.
    I made both these changes & it just sounds wayyy better.
    2N5457 bias to 4.84v
    BC108B bias to 4.54v

    My 2 Cents!

    Cheers music6000"

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  13. I noticed that even with the gain at the lowest setting it still had quite a bit gain. Would it be possible to lower the gain?
    Maybe lowering the 10k resistor to ground after gain 1...?

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    Replies
    1. Probably by switching back to 2.2uf capacitors ;)

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    2. Hey, thanks.
      I noticed this stock as well.
      I´ve made the changes today; Just put a 4.7uf in there, (FET I think), and now it has more body without losing its middy character.
      Didn´t try plaing with the 10k resistor. Will do it tomorrow.

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  14. Would love to build one of these. How does it sound with humbuckers vs. single coils?

    http://topguitarpedals.com

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  15. There was a 4 knob version, with a pre gain control (pre gain maxed is the stock 3 knob sound), giving lower gain sounds. Would like to have a schematic for that version.

    I have the regular 3 knob version, and it sounds better (to me) without a buffered pedal in front. Not so harsh, and a bit fatter.

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  16. Just finished the board and hooked everything up and am not getting any sound. I will recheck for solder bridges etc. Have a question on "Filter 1 to Input". Do I run another wire between the board input (or center terminal of the 3PDT switch) and Filter1? This is a little confusing since the input is already connected to the 3PDT switch.

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  17. You could run 2 wires from the switch, or connect filter 1 to the same board input hole connection.

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    1. Thanks Gilberto. Ran two wires from the switch and re-soldered the socket for the transistor and it is working now. Getting 4.5V on Q2 using a BC183 with 290hfe. Will try out various NPN transistors to see which one sounds the best. Can't get any sound out of a 2N388 Germanium with 195hfe. Will have to recheck the pinout.

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  18. I have revisited this one because I really wanted it to work! Now I have a 2N5457 biased at around 4.7VDC and a BC-something-or-other with an hfe of 295 with 4.5VDC on the collector. It took a 27K resistor on the drain of the Jfet to get it to bias.

    It sounds great. I left the 470pF cap out altogether because people were saying it was extremely bright and my pedal sounds like I imagined it should. If I turn gain past halfway I get some squeally oscillation but that's ok because I never need that much dirt. With P90s it sounds pretty darn good from gain on zero to 1/4. The Filter knob works well.

    Thanks for all the info guys!

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  19. I ended up using a BC183 with 280hfe and the pedal sounds fantastic. I have been using this as my main overdrive/fuzz on my pedal board and I can get a mild crunch/overdrive all the way up to a decent fuzz tone sound. If anyone is going to use the BC183, be aware that the pinout is different than the BC108 as shown on the layout.

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