MXR Phase 45 DIY volume drop problem.

[Rethfing]

Where did you get that awesome board? :O Tomorrow I may not be able to test it because I left my amp in rehearsal room and Im little busy overall, but as soon as I will be able to I will post results.

[R O Tiree]

My own design and made by mine own fair hand

2" x 2", switch, pot and LED PCB mounted... the only wires to the board are Input, Output, +9V and GND.  That will make for a very clean layout inside a 1590B, I think.

[Rethfing]

I dream of having such skills like yours :O

[PRR]

With MXR's values:
10K||10K= 5K output
driving normal 500K amp input: 500K/505K= 0.99 gain or 0.1dB loss
driving 20K line input: 20K/25K= 0.8 gain or 2dB loss

With 1.5K||1.5K= 0.75K output
driving normal 500K amp input: 500K/500.75K= 0.998 gain or 0.01dB loss
driving 20K line input: 20K/20.75K= 0.99 gain or 0.3dB loss

The only significant loss is the 2dB. You can not tell the difference 0.01dB, 0.1dB, or 0.3dB.



> amazed how a company like MXR could let this slip by

ONLY when driving a low impedance input.

_I_ would glare at Peavey. With all the chips in there, there was no need to let input be 20K.

[R O Tiree]

> _I_ would glare at Peavey. With all the chips in there, there was no need to let input be 20K.

I just tried it out on my Behringer (don't be mad at me - it's the amp I use when testing FX) and there was a volume drop... dug the manual out and the FX Return input impedance is only 10k!!  I've dropped the resistors to 470R and there's still a little bit of a drop.  You reckon there's enough "grunt" left in there to drop to 220R each, Paul?

[PRR]

> enough "grunt" left

Try it. It may distort, but it won't hurt the chip.

[R O Tiree]

Thanks.

[Rethfing]

Mike, could you post quick guide how to draw a board? I would like to create my own boards with 3PDT on-board. I know how those connections work so I think Ill handle it.

[deadastronaut]

@reth:

try diy layout creator.  nice and easy pcb/vero prog..

http://code.google.com/p/diy-layout-creator/


thread

http://www.diystompboxes.com/smfforum/index.php?topic=44838.new;topicseen#new

[Rethfing]

Thanks!

[R O Tiree]

I use ExpressPCB/ExpressSCH at the moment.  It's available as a free download from www.expresspcb.com.  This is actually a fabrication house - they expect you to design your board and then send it to them for manufacture.  It does, however, allow you to print your designs out.

So, I print to acetate on my laser printer and then expose the photo-sensitive copper-clad board to UV light in a fairly cheap unit I got a few years ago.  Have a look on the interwebs for DIY projects that people have done with UV LEDs, etc, if you don't want to go to the expense of a commercially-sourced light-box.  Having exposed the board it needs to be developed - usually a Sodium Hydroxide or Potassium Carbonate based developer is used depending on the photo-resist. Then etch.  You can leave the resist on the board to protect the traces from corrosion for as long as you like.  You can even solder through it as it makes a half-decent flux!

However, my boards go through a several more processes to tin the traces and then apply, expose, develop and cure the solder-mask before drilling.

As to board design... start simple.  Something like an Orange Squeezer or a fuzz of some kind.  Low parts count, small board, for your first few goes until you get the hang of it.  The first step is to copy the schematic exactly from whatever picture you got off the 'net into ExpressSCH.  Once that's done, save the file.  Open up ExpressPCB and "Link File to Schematic" (in the "File" menu).  Now place resistors, caps, ect, outside the work area, number them (make sure you have enough of each component) and then start wiring them up joining them with traces.  You'll find that as soon as you click on a pin on a component all the pins on other components that should connect to it will light up in bright blue.  This is very handy - as long as your schematic in ExpressSCH is correct then your PCB will also be correct.  It's worth doing a few "thought experiments" with lots of circuits to get the hang of it.

Here's how I designed the 3PDT switch layout - Get a 0.130" pad and place it on a blank design.  Place 8 more and arrange them in 3 columns 5.3mm apart and 3 rows 4.6mm apart.  Switch to silk-screen layer and draw a 19mm x 18mm box around them.  Click and drag through the whole assembly (which will highlight them in grey) and then select "Group to make PCB Component" from the "Component" menu.  Double click this new component and type "SW" in the part name box and click OK.  Go back to the "Component" menu and select "Save Custom Component" and call it "3PDT Switch".  You can now use it in all your designs.  I use a miniature XYZ Proxxon milling machine with a 1mm routing bit to cut the 2.2mm slots for the tags on the 3PDT switches.  Round holes will not be easy to solder at all - they have to be slots.

Hope this helps.

[Rethfing]

Finally found some time to resolder those 2 resistors and capacitor. I used 1k resistors. Didnt notice any volume drop using my DIY Ruby amp, but if there's drop while using fx loop Im going to check on wednesday

[Rethfing]

No volume drop hoooraaaaaay

[deadastronaut]

whoohooo....

[R O Tiree]

No volume drop hoooraaaaaay

Excellent news

[Rethfing]

I've been messing around with my P45, it sound good, but I think the sound should have more treble in it. Its full of bass right now, is there any part I could replace to either decrease bass and/or increase treble and mid?

Oh and btw, happy new year!

Can it happen because I used 2n5952s with lower voltage than suggested (2.5V-2.6V)?

[Rethfing]

Anyone? This is really getting on my nerves, I want to use it in my pedalboard but I cant..

[PRR]

> Anyone?

Link to circuit:
http://www.tonepad.com/project.asp?id=13
http://www.tonepad.com/getFile.asp?id=70


> should have more treble in it. Its full of bass

Shouldn't be. The circuit is flat and we fixed the interface impedance issues.

So we suspect a build problem. But there isn't really any place to lose treble.

_I_ would throw it on the signal generator and measure frequency response, but I know such test-gear is not common.

[Rethfing]

Maybe there's some part that is broken causing treble loss, some capacitor maybe? Dont know what to think of that..