Skreddy Lunar Module

Nocentelli · Post by **Nocentelli** » 24 Nov 2011, 22:31

I've made several of these now, a couple with the pre gain and tone as trimmers and one five knob deluxe: I've got a vero layout that can be used for a 2, 3, 4 or five knob pedal (i.e. the pot connections are all on adjacent strips so a trimmer can just be dropped in if you don't need that pot as an external control) that I'l post when I get home.
I really like having two gain knobs, as it effectively doubles the range of the filth available - I've found that with a pre-gain trimmer, either the minimum gain is not clean enough, or the max gain is not dirty enough. However, I'm considering trying out a single gain knob with a dual-ganged pot controlling BOTH Q1 and Q3 gain, the obvious problem being that one pot needs to be 1k and the other 2k. I assume they don't make dual-ganger with two different values, so my idea is to either use a 2k and sling a 2k resistor across one set of lugs, but this will mess with the taper. The other option is to crack open the pot and replace one wafer with the appropriate value wafer robbed from another pot (as described in rg's Secret Life of Pots) - Has anyone actually done this successfully?

Skreddy · Post by **Skreddy** » 25 Nov 2011, 23:57

Nocentelli wrote:I've made several of these now, a couple with the pre gain and tone as trimmers and one five knob deluxe: I've got a vero layout that can be used for a 2, 3, 4 or five knob pedal (i.e. the pot connections are all on adjacent strips so a trimmer can just be dropped in if you don't need that pot as an external control) that I'l post when I get home.
I really like having two gain knobs, as it effectively doubles the range of the filth available - I've found that with a pre-gain trimmer, either the minimum gain is not clean enough, or the max gain is not dirty enough. However, I'm considering trying out a single gain knob with a dual-ganged pot controlling BOTH Q1 and Q3 gain, the obvious problem being that one pot needs to be 1k and the other 2k. I assume they don't make dual-ganger with two different values, so my idea is to either use a 2k and sling a 2k resistor across one set of lugs, but this will mess with the taper. The other option is to crack open the pot and replace one wafer with the appropriate value wafer robbed from another pot (as described in rg's Secret Life of Pots) - Has anyone actually done this successfully?

Do the external-resistor taper thing. The 1K pot is supposed to be a reverse-audio taper anyway, so using an external resistor (as per RG Keen's "reverse log" method) to taper it that way is perfect.

Unoriginal · Post by **Unoriginal** » 01 Dec 2011, 21:15

Nocentelli wrote:I've made several of these now, a couple with the pre gain and tone as trimmers and one five knob deluxe: I've got a vero layout that can be used for a 2, 3, 4 or five knob pedal (i.e. the pot connections are all on adjacent strips so a trimmer can just be dropped in if you don't need that pot as an external control) that I'l post when I get home.
I really like having two gain knobs, as it effectively doubles the range of the filth available - I've found that with a pre-gain trimmer, either the minimum gain is not clean enough, or the max gain is not dirty enough. However, I'm considering trying out a single gain knob with a dual-ganged pot controlling BOTH Q1 and Q3 gain, the obvious problem being that one pot needs to be 1k and the other 2k. I assume they don't make dual-ganger with two different values, so my idea is to either use a 2k and sling a 2k resistor across one set of lugs, but this will mess with the taper. The other option is to crack open the pot and replace one wafer with the appropriate value wafer robbed from another pot (as described in rg's Secret Life of Pots) - Has anyone actually done this successfully?

I would LOVE to see this vero please post it soon!!

Nocentelli · Post by **Nocentelli** » 01 Dec 2011, 21:54

sodapep2 · Post by **sodapep2** » 17 Feb 2012, 07:38

Awesome work! What hFe values have you all been using for this pedal? Seems like they are higher gain?

Nocentelli · Post by **Nocentelli** » 17 Feb 2012, 14:11

I've never measured the hFe in any of my builds.. I've used BC109c in all the lunar fuzzes I've built, and they are fairly high gain. Each of my builds has had a slightly different body control (usually altering the big cap from 220n up as high as 470n) and this seems to make a much bigger difference to the fuzzyness/"gain" than different transistors from the same batch.

mojah63 · Post by **mojah63** » 24 Feb 2012, 10:25

I used 109c around 425 hfe . I tried higher at 650 but thought it was buzzy compressed sounding. Those were nos phillips 109c. I also tried some 109b's. Nos Ti around 300 hfe . It didn't have a clear high end for me and the gain was a little low but usable. I don't think the circuit is picky.

spfautz · Post by **spfautz** » 15 May 2012, 01:01

If this is the wrong place to post this, I'm sorry.

I am new to building, and the LM is my most complex circuit so far. I'm having difficulty troubleshooting. I'm checking with the audio probe, and am getting a loss of signal at my 100r resistor in the center of the schematic. I'm measuring that the resistor is functioning properly, and the joints are good, which leads me to think, maybe I'm reading the schematic incorrectly. Here is what I think the audio path is. Is this correct?

I'm using the layout from http://tagboardeffects.blogspot.com/201 ... -fuzz.html
which is different from the layout in this thread.

Any help would be appreciated.

IvIark · Post by **IvIark** » 15 May 2012, 01:37

The layout is verified so we know that is ok, so post a front and back pic of your build and I'll see if anything seems amiss.

spfautz · Post by **spfautz** » 16 May 2012, 01:44

Here are some pictures. There may be some extra wires in the picture that aren't with this circuit. I'm making a 2 in 1 fuzz w/ LMD on one side and Hyperion on the other.

My thought is that if the signal is stopping at the 100r resistor, then it is finding another place to travel that has least resistance, but I can't find any bleeding of bridges.

Also the signal coming out of the "body" pot is very soft, and then it stops at the 100r resistor.

Thanks

Stefan

sodapep2 · Post by **sodapep2** » 13 Jun 2012, 20:22

Does anyone get mad oscillations when the pregain pot is up above like.. 5 oclock? With the fuzz even at noon, it starts squealing pretty bad. Is there a remedy for this? Perhaps the gain of the transistors is too high?

Nocentelli · Post by **Nocentelli** » 13 Jun 2012, 21:14

sodapep2 wrote:Does anyone get mad oscillations when the pregain pot is up above like.. 5 oclock? With the fuzz even at noon, it starts squealing pretty bad. Is there a remedy for this? Perhaps the gain of the transistors is too high?

First of all, which layout are you using? As noted a few pages back, several builders noted oscillation with gilmour pugliese's vero for the deluxe.

Secondly, a couple of my builds (my vero layout) produce a bit of hum/noise/oscillation when both pre-gain and fuzz controls are at maximum: Pull the pregain (2k) pot back a hair and it disappears. I think i remedied it by adding a small resistor (100r?) between the pregain cap and ground. I wouldn't describe it as mad oscillations, though: It's only really audible if you stop playing.

sodapep2 · Post by **sodapep2** » 14 Jun 2012, 01:29

Ah, sorry! I used Mike's layout, but used pots instead of trimmers for the sharpness and pregain. I can't max either the fuzz or the pregain.

TheLemon · Post by **TheLemon** » 16 Jun 2012, 01:27

Check the left side under the board..

sodapep2 · Post by **sodapep2** » 16 Jun 2012, 23:47

TheLemon wrote:Check the left side under the board..

A bit cryptic, but I had a look and didn't see anything amiss. I measured the transistor voltages and took some pics. Thanks for any assistance.

Q1
C - 4.5
B - 1.37
E - 0.87

Q2
C - 0.97
B - 0.57
E - 0

Q3
C - 4.17
B - 0.97
E - 0.37

... Q2 seems a little odd? Anyway, some pics.

fretzburner · Post by **fretzburner** » 18 Jun 2012, 05:12

Build this using the schematic provided by the generous designer Skreddy and works on first try.I'm using BC109 trannies because it's the only one i have.I have here BC550,BC108B,BC549 don't know what's best to use.I noticed the sharpness control using log pot is effective only at extreme settings(3/4 to full rotation).Maybe linear pot is more suitable for this.And the pre-gain pot is 5k(don't have 2k),Is this okay or have to shunt 3.3k-3.9k resistor?

Nocentelli · Post by **Nocentelli** » 18 Jun 2012, 05:25

A linear pot works best for the sharpness, though I've used a reverse audio and that also has a decent range. As for the pregain control, you'll need that parallel scaling resistor or Q1 won't be properly biased.

fretzburner · Post by **fretzburner** » 18 Jun 2012, 05:40

Thanks Nocentelli
I'll try to shunt a resistor to my pre-gain pot.Will also try a reverse log pot on sharpness control.

sodapep2 · Post by **sodapep2** » 18 Jun 2012, 23:14

Alright, all the components are correct, cuts are clean and solder joints good... did anyone else use Mike's layout and use external pots for the trimmers? I'm close to just scrapping it and making Nocentelli's layout.

Deny · Post by **Deny** » 19 Jul 2012, 06:18

Just built mine using Nocentrelli's vero layout (thanks!), what a great sounding pedal. Skreddy deserves all the praise this pedal gets at TGP, I'm *really* loving this thing. I also get the oscilation mentioned in this thread earlier (sounds like a shorted power transformer) but I managed to make it go away by adjusting the pregain and body trimmers, and the pedal still sounds stellar, either by itself or combined with amp dirt or other pedals.

Skreddy Lunar Module [traced]