DIY Stompboxes > Building your own stompbox

Voltage Multipliers (for our tube projects...)

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Hi Renegadrian,

When I come home this evening I'll send you some pictures.  Don't expect too much though, I built the Real McTube on a (real) piece of breadboard.

It's really cool that I can dial in the voltage as given in the schematic.  Yeah that SMPS is really flexible.  The SMPS doesn't get hot, not even warm after 2 hours.

I did some listening at low levels : through my Laney VC30 and (in my workplace) a Vox plugg-in.  Fuzzy distortion with a tube-depth.  Again at low level. 

I tried it with 2 valves an old China ECC83 and a Sovtek ECC83 WA. The difference was noticable, so further testing and listening ahead !

I made a vero for the MAX1771 Charge Pump, i've spaced it out a bit more as I think it might be a bit more sensitive to stray capacitance than others on vero... (or is the opposite right and I shoulda made it smaller... will probably make a smaller one later anyway) only one way to find out though! Unverified as of yet.

(All thanks go to Rick Holt & Nick The Designer)

Here's (as promised) a picture of my preliminary build Real McTube.  Fully functional, waiting for a box.

With the MAX1771 smps you may want to use high amperage rated inductors such as these from Rapid:

Also worth uprating the reservoir caps voltage capability if you plan to tweak the smps in anyway - I was getting 500v out of mine at one point. Banzai sell some quite small 350v 4.7uF caps:

You can tweak up the maximum available voltage by screwing around with the trimmer and it's two resistors, I ended up using 180k/1k trimmer/1k instead of 1M/5k trimmer/10k.

Good luck with building onto veroboard - that's a lot of copper strips to act as aeriels. In the MAX1771 thread Nick Desmith posted:

--- Quote from: nickds1 on April 12, 2010, 09:59:37 AM ---You are actually quite lucky it worked on a proto board - MAX1771s are pretty sensitive to stray capacitance and you may have a few unexpected high frequency artifacts in there

--- End quote ---

I found the 1771 smps to work on breadboard but was highly unstable. On perf it works very well IMO. Better still would be a PCB with large ground plane. Nick Desmith on his PCB layout:

--- Quote ---You can see the shadow of the ground plane on the underside and note that several vias in parallel have been used to connect Rsense to the ground plane - each via can typically handle a few 100 mA, and as up to 2A can flow through Rsense we need to provide a good low impedance path to ground.
--- End quote ---

translated from HERE

A power supply to feed nixie tubes and PIC. It goes at 12V and it will charge up to 180V.
max current is 11mA. this schem uses the MAX771.
resistors must be 1/4W 1%. The mosfet doesn't get hot so heatsink is not needed.
220uH must be max 100mA.

(obviously the PIC part is not needed for our circuits, so it can be deleted)


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