Crawls Backward (When Alarmed)

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First Act MX-510 Distortion Pedal (DS-1 Clone) Modifications

Today I delve into the world of the famous Boss DS-1 distortion pedal and the seemingly endless modifications for it.

Except I'm not doing the mods on a DS-1.

What you see on the left is a First Act MX-510 Distortion pedal.  If you're not familiar with First Act, they make very inexpensive guitars, amps and other instruments aimed at children.  They also make a higher-end line of guitars that have a decent reputation.

The best First Act story involves Paul Westerberg.  He was on tour, stopped into a big-box store to get some shaving cream, and saw a First Act guitar.  He bought it on a whim, and it soon was being used on the tour.  Subsequently, First Act did a run of Paul Westerberg model guitars, which sold for under $150.

Back to the MX-510.  This little pedal is a clone of the Boss DS-1.  It went out of production a few months ago, and Toys-R-Us was selling them for (get this) $5 US!  I bought two of them.  And today I'm going to do some DS-1 mods to it.

You can easily find the DS-1 schematic and layout online, but the MX-510 has a different circuit board.  However, thanks to one of the great folks at freestompboxes.org, I found a diagram of the board tracing.  Armed with that, and a DS-1 schematic, I found all the components I wanted to mess with.

There are 2 boards - the main board, and a second one for the controls.  They're connected by two ribbon cables.

All of the mods I did are DS-1 mods.  They go after the usual DS-1 issues: too much distortion, tone control ineffective, too much treble with distortion, too much compression, etc.

The first thing I did, and certainly the easiest and arguably most effective is to lift the two clipping diodes, D4 & D5.  Don't short them - the pedal won't work if you do.  I just unsoldered one end of each and left them in place in case I wanted to do more with them in the future.

The picture shows their location on the board.  This mod takes care of the compression in one shot.  It also moves the pedal out of the super fuzzy territory back into distortion mode.  I really liked the pedal after this.  If you do only one mod, this may be it.

Next I did the well-known mod developed by the justly famous Jack Orman.  This is the "fat mod."

This mod reduces the gain of the input transistor, Q2, and noticeably fattens up the tone.  Two resistors are changed - R6 is changed to 150K, and R9 is changed to 1K.

I wanted to include a picture of how I desolder components.  Use solder wick.  You can get it in different widths - I have thin for PC boards and thicker for amps and radios.  I've tried solder suckers and they don't work for me.

This will leave you with a perfectly clean pad or tab to work with.  This stuff is cheap - get it online at Mouser.

At this point, the pedal was much improved for my taste.  It now had a lot less gain, and it sounded much bigger, open and transparent.  I'm personally not a high-gain player, and I found a number of usable tones and settings at this point.  But even cranked, there was plenty of distortion for an AC/DC-type of tone.

What still bugged me was the 'fizz' that the DS-1 (and MX-510...) are known for.  This is especially noticeable on pick attack and during note or chord decay.

So I did a couple of things to reduce the treble and cut down the fizz.  One was to change C7, on the control board up to 470pf.  This cut the fizz and treble a fair amount.  Interesting to note that a stock DS-1 has a 10pf cap here, while the MX-510 has a 100pf - which tells you that the folks at First Act are aware the fizz is an issue.

The last few changes went after the tone stack in order to flatten out the midrange dip that's prevalent in the stock pedal.

I changed R16 to 39K and R17 to 33K.  Both are 6K8 stock.  I also changed the tone caps C11 and C12.  C11 is now a .068 and C12 is now a .047.  I also changed out C10, the cap across the diodes, to an .022 in an effort to ground some treble out.

This set of mods evened out the tone and cut down the fizz a bit more.  The fizz is still there, but it's not quite as annoying.

I made up a picture with all of the board components identified, which may be helpful if you decide to mod an MX-510.

This little pedal is a lot of fun to use now - it's much more dynamic and gets a nice overdrive tone.  You can get these pedals very cheaply, and with a couple bucks worth of parts, you can have a 'boutique' version!



 
 
 
 

Post a Comment 1 comments:

  • texasfuzz said...
    December 23, 2013 at 7:37 AM
    Nice write up, very clear. I have two of these which I just modded based on your write up. I credited you in my blog and linked your post as well - in case someone wants to find the original details. Thanks again. I am looking forward to reading the rest of your posts.

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