Lotus Pedals Snowjob (underdrive)

geiristudio · Post by **geiristudio** » 18 Jan 2014, 14:36

So I got this pedal recently and I'm wondering about the circuit. Lotus Pedals says it's an under drive as opposed to an overdrive.
I've drawn up the PCB as it is laid out and it's single layer. There are a few things I'm not sure about so I need your help with this.

Here's what I drew up:

Here's a photo from Lotus Pedals on Instagram of the PCB:

The transistor is a 2N5088.
I've noticed that the + of the 47uF goes to the lower connection of that 390 ohm resistor but I can't see it going anywhere else than to ground so it doesn't matter.
The collector goes to the 47nF cap as well as the 1N4148 on the top side, not the bottom.
I'm not sure about that other lug of the SPDT switch that's connected to the board. Does it go to ground? I don't see a trace going anywhere.

I'd love to have a schem of this soon

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 14:42

Electra - Again.

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 14:46

Lotus pedals website wrote:An underdrive is similar in function to an overdrive, except instead of driving the amp it drives from the guitar, adding harmonic content to fill the space between the notes.

The SNOWJOB is a dual mode underdrive, with the toggle to the left (white snow mode) the pedal is extremely transparent, almost acting like a boost, but full and rich with headroom to spare.

Disconnects diodes from ground (no clipping). Why "almost like a boost"?

With the toggle to the right (yellow snow mode) the pedal is a bit more aggressive, adding musical harmonic clipping to the spaces between the notes, like a tube amp on the brink of destruction, right in that sweet spot.

Connects diodes to ground (clipping).

IvIark · Post by **IvIark** » 18 Jan 2014, 14:56

Yes, just an Electra with switchable shunt diodes. Could be the latest COT50.
The flowery marketing will no doubt have TGP overexcited though.

geiristudio · Post by **geiristudio** » 18 Jan 2014, 15:02

I just spotted that the clippers are wired to the output, not before the output cap.

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 15:07

They have to be, or the diodes-to-ground would screw with the bias of the collector when connected.

IvIark · Post by **IvIark** » 18 Jan 2014, 15:12

I may as well do a layout as it's a 2 minute job, are both pots linear?

geiristudio · Post by **geiristudio** » 18 Jan 2014, 15:13

Yeah it's just hard to see the traces on a white PCB, especially when it's underneath the components.

IvIark · Post by **IvIark** » 18 Jan 2014, 15:26

geiristudio · Post by **geiristudio** » 18 Jan 2014, 15:43

Woah that's quick! Both pots are linear yes. Thanks!

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 15:46

Wot no tropical fish caps?

IvIark · Post by **IvIark** » 18 Jan 2014, 15:47

The library component was too complicated so I gave up

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 16:11

I assume the input pull-down resistor (1M) is completely unneccessary due to the 100k input pot resistance?

IvIark · Post by **IvIark** » 18 Jan 2014, 16:15

I certainly don't think it will pop without it, but the pulldown resistor could affect the input impedance I suppose

Nocentelli · Post by **Nocentelli** » 18 Jan 2014, 16:28

IvIark wrote:I certainly don't think it will pop without it, but the pulldown resistor could affect the input impedance I suppose

But if 1M is a great deal bigger and is in parallel, it would surely only make the impedance lower? and it would only alter it from 5k1 to 5.074k (at minimum drive) and 105.1k to 95k at max. I just thought you could make it one column shorter with no change to the sound or operation of it.

IvIark · Post by **IvIark** » 18 Jan 2014, 17:55

It certainly isn't going to be a night and day difference but I think I'd still prefer to keep it as per the original. No need to save space when it will easily fit in a 1590A anyway, and there's a cut between the two outer resistors which means I'd have to shift things about to try to lose that column anyway. I've also got about 4000 1M resistors

indyguitarist · Post by **indyguitarist** » 20 Jan 2014, 03:23

Nocentelli wrote:Electra - Again.

I know everyone refers to a npn transistor gain circuit with diodes as an "electra", but isn't it basically just a common sense thing? I mean, a transistor as a gain stage with diodes to ground to clip the circuit may have been done historically as an electra years ago, but realistically nearly all overdrive and distortion circuits are common sense approaches. Personally, I don't see it as a "electra" circuit, I just see it as a npn transistor that's clipping via diodes.

Maybe I just don't understand the desire to call everything a clone.

FiveseveN · Post by **FiveseveN** » 20 Jan 2014, 04:17

I's just a shorthand. I think everyone here hopes to see something new when a pedal pops up. Which is clearly not the case here, and people might find it particularly disappointing considering the "flowery marketing".

Nocentelli · Post by **Nocentelli** » 20 Jan 2014, 22:19

+1, Electra is just shorthand, like "big muff clipping stage" rather than describing the circuit in detail.

If one wanted to, one could say it's a lovepedal woodrow clone with a two caps, one resistor and an added pot different.