One knob boost circuits, EP, LPB, DOD 250

[Killthepopular]

My next build will be a one knob clean boost hopefully, not necessarily for gain, just an EP style, always on, tone enhancer thing. Here's My EP layout:
https://4.bp.blogspot.com/-_ltumfwhRb4/U5JdWEcP34I/AAAAAAAAHsc/WJJ0ZTbv_Ks/s1600/Echoplex+EP3+Preamp+-+Early+Version+II.png

Here's an LPB1:
http://2.bp.blogspot.com/_y7gcfRKQFgA/S6VnFIga11I/AAAAAAAAAIY/beERCO9AO_A/s1600/EHX+LPB1.png

Here's a DOD 250:
https://4.bp.blogspot.com/-OGV5td7Xiao/Uepb8pu3nhI/AAAAAAAACeo/YhOzP3rNtL4/s1600/DOD-250-Reissue.png
And an EZ DOD which cuts the number of on board components from 19 down to 15:
http://www.bouron.org.uk/marc/EZ250.GIF

I want to breadboard all three and build whichever I like most.

2 questions:
1. Is the EP layout a valid pedal build or is it missing some stuff, like input stuff to stop the switch making a pop sound or whatever? Or an input capacitor (whatever that is)? It's a basic circuit that was possibly meant to be added to other circuits rather than used on its own. I'm aware that it will probably just get me to unity at full blast, but that's ok for what I want.

2. Does anyone know of a layout/schematic for a one knob clean boost based on a 250? I just want volume or tone shaping with no clipping so the circuit should be pretty small and simple, i would think... I'm probably too much of a noob to figure out how to turn a dod schematic into a clean boost layout but maybe someone could give me some pointers...

Here's a schematic for a DOD: http://beavisaudio.com/schematics/DOD-250-Overdrive-Schematic.htm
What would I omit to turn it into a simplified clean boost? The diodes obviously. Anything else?

Hm, i've not breadboarded anything before. I guess I should be working from schematics, not layouts?

Thanks.

[bluebunny]

I guess I should be working from schematics, not layouts?

Yes.

BTW, the EZ 250 (my layout, as it happens) is nothing to do with the DOD 250.

[slacker]

2. Does anyone know of a layout/schematic for a one knob clean boost based on a 250?

If you try and make the OD250 into a clean boost you basically end up with the MXR MicroAmp https://www.electrosmash.com/mxr-microamp

[patrick398]

I'd recommend trying out an AMZ mosfet boost and a zvex SHO while you're breadboarding. Much more interesting than the LPB-1 in my opinion

http://www.muzique.com/schem/mosfet.htm

http://effectslayouts.blogspot.com/2015/01/zvex-sho-crackle-okay.html

[Mark Hammer]

How much boost do you want/need? Is it simply to get optimum S/N and some buffering for retaining top end, or do you also want the capability to "punish" the front end of an amp?

The MOSFet boosts like the AMZ unit and ZVex SHO will certainly brighten up your sound.  You can always try a Stratoblaster as well.  Indeed, there are a ton of single-FET boosters around.

My one caveat is that if included in your objectives is being able to "punish" the front end of an amp and push it over the edge, you will want some means for dialing back the treble.  That could be a panel-mounted treble-cut control, a trimmer inside, or a fixed treble-cut.

[Killthepopular]

BTW, the EZ 250 (my layout, as it happens) is nothing to do with the DOD 250.

Oh.

If you try and make the OD250 into a clean boost you basically end up with the MXR MicroAmp https://www.electrosmash.com/mxr-microamp

Ah. That's useful to know. I don't like the sound of the Micro amp (on video demos). I just thought I might like a 250-based boost as I tend to like 250s. I'll probably skip it then.

I'd recommend trying out an AMZ mosfet boost and a zvex SHO while you're breadboarding. Much more interesting than the LPB-1 in my opinion

Not heard of the AMZ... I sort of liked the clips of the SHO, seemed kinda gritty in a good way. Maybe I'll try that one too.

How much boost do you want/need? Is it simply to get optimum S/N and some buffering for retaining top end, or do you also want the capability to "punish" the front end of an amp?

My one caveat is that if included in your objectives is being able to "punish" the front end of an amp and push it over the edge, you will want some means for dialing back the treble.  That could be a panel-mounted treble-cut control, a trimmer inside, or a fixed treble-cut.

Nah this isn't really my objective. I like the idea of the EP preamp, just a simple little circuit that makes your tone subtly better in some way. I was just going to make an EP pre at first (i dig the smoothness) but then I realised that I maybe slightly preferred the slightly grubby, warm tones of the LPB1. So I'll make those two, and I'll have a look at some schematics. I'll have another look at the SHO too because it seemed kinda cool. I guess I should try that Tillman one too...

[roseblood11]

MXR CAE MC-401

[patrick398]

Not heard of the AMZ...

AMZ website is definitely one worth bookmarking, there's a butt-load of great info and schematics there to explore. The mosfet boost is a great clean boost for giving your tone a bit of sparkle and clarity (in my opinion and with my setup) but as with all these booster circuits, it depends what guitar and amp your using. Breadboarding is the best way to go 

[Mark Hammer]

Not heard of the AMZ... I sort of liked the clips of the SHO, seemed kinda gritty in a good way. Maybe I'll try that one too.

Jack Orman (the fellow who IS AMZ) has probably been at this sort of thing longer than many of us.   Trust him.

[Killthepopular]

Had a quick look at AMZ. Looks like a great resource. Will definitely start skimming through it.

[bluebunny]

BTW, the EZ 250 (my layout, as it happens) is nothing to do with the DOD 250.

Oh.

FYI, this is Joe Davisson's EZ-250 overdrive:



And rather good it is too.

[allesz]

Skip the two 1n914s and you probably will get a cleaner boost: it's a lpb1 with a buffer in front. A very smart mod.
You can also remove the clipping diodes from a real dod 250.
I suspect that both solutions would not be completely clean, but maybe they will work for you.

[Mark Hammer]

The DOD 250, MXR Distortion+, and similar, use op-amps that will not swing wider than within a volt of each rail, or +/-3.5V.  Amplifying a +/-100mv signal more than 35x runs out of headroom, such that what hits the diodes is already clipped, once you've exceeded that amount of gain (and both units have max gains >200x.

I have no idea how wide discrete circuits like this can swing, and what their behaviour is once headroom is exceeded.  Suffice to say that lifting those diodes WILL get you clean sound, provided the gain is kept modest.

[Killthepopular]

Hm. One guy says a DOD 250 is the same as a Micro Amp with some extra stuff. Another guy says it's like an LPB1 with some extra stuff.
I'm gonna do the LPB1 because the demos sound cool. I was gonna skip the micro amp because the demos made it sound a bit harsh to my ears. Originally I wanted to make a clean version of the 250 because I liked the 250 and thought it might give me some unique, 250-esque sound. But if it's just gonna end up like a boost I don't want to make (micro amp) or a boost I'm going to make anyway (LPB1) it seems like there isn't much point in me going down the 250 route.

So I'll try out the LPB1, an EP and I'll have a look at the SHO, the Tillman and some AMZ stuff.

[garyg]

If it helps at all, the VFE Distortion3 is effectively a micro amp, 250 and distortion+ in one box. The circuits of the three are very similar with just a few component changes. By making these components switchable you get all three near enough.

Schem: http://vfepedals.com/schematics/distortion3.pdf

[roseblood11]

The MXR CAE MC-401 is totally clean, and doesn't color the sound at all. My veroboard layout has an additional voltage doubler for mor headroom, a switch for booster or buffer mode (can be omitted for booster mode only), and RG Keens Millenium bypass to use a 2pdt switch instead of a 3pdt:

[Killthepopular]

↑↑↑ Looks fancy. Nice and clear layout too. But I already checked out the MC401 and whilst I thought it sounded better than the micro amp, I also lumped it in with those other boosts that seem to make things subtly brighter or clearer on top, and I really like the idea of a boost that fattens/mellows slightly, so I think I'll stick with the EP3 and LBP1 circuits. I also checked out some of the other circuits mentioned above (SHO, Tillman, AMZ mosfet) and again found that they made things a bit crisper and clearer which doesn't appeal to me all that much. There was another boost that sounded good to me, the Pigtronix class A boost, but I couldn't see a schematic for that anywhere so I guess I'll skip it.

I got the extra parts I needed for the EP and LBP so I'll get started on them today or tomorrow. My progress will probably be quite sluggish because I'm trying to keep writing lots of songs rather than dedicating large stretches of time to circuit fiddling.

[Gus]

have you looked at version 2 of the beginner project?

https://www.diystompboxes.com/smfforum/index.php?topic=97041.0

[roseblood11]

You seem to make decisions based on hearsay or YouTube videos...
The MC-401 has the most linear frequency response from all the circuits that are mentioned above.
Every booster "brightens" your signal, because it effectively shortens the part of the cable that your pickups "see" - the resulting resonance frequency becomes higher, because only the capacitance of the cable between guitar and booster is part of that equation as long as the booster is active.

Two solutions:
- a capacitor to ground at the input of the booster circuit to simulate the cable capacitance, maybe 100 to 150 pico farads per meter.

- a capacitor to ground safter the opamp, as in the DOD250. Add a pot to turn it into a simple tone control.

[antonis]

An easy to breadboard alternative proposal..
(greetings to Sam..  )

Gain all down to unity (verified) with as clean as reasonable sound..



P.S.
C3 value can be reduced to 1μF without tone issues for following impedance down to 10k..