Valvecaster on 18v

[Dinosaur_Sr]

Hi guys, I've built a valvecaster but I don't have a 12v supply to run it from, all I have is an 11.5v wart, a 9v onespot and an Mxr brick with 9v and 18v. I tried the 9v and I get nothing, the 11.5 just seems to make the pedal whine but no other sound. Can I run this on 18v without it getting damaged? I don't have the right voltage regulator around I don't think, just a 544, 725D, 742MA, and a 17805.

[psychedelicfish]

Your results with other power supplies seem to suggest that your valvecaster doesn't work, I don't think 18V will help

[mountianjustice]

Im running mine @ straight 18vdc 2.23A and its working great. Not sure how long it will last but its working. It gives me as much gain on my clean as i used to have on OD2. And turned my OD2 into a brutal sounding monster. By the way im using a ruby 12AX7AC5 HG K tube. I tried running it on 13vac but all i got was a loud buzz or tone and no output not sure why went back to the 18vdc and no noise. My goal is to run the heater @ 12.5 with a wall wart and run the plate a little hotter maybe 24-40vdc, put it in a rack unit and mount it with my EQ. It would have a simple 3 knob gain, tone, and volume control with a footswitch for on/bypass.

[anchovie]

Im running mine @ straight 18vdc 2.23A and its working great. Not sure how long it will last but its working. It gives me as much gain on my clean as i used to have on OD2. And turned my OD2 into a brutal sounding monster. By the way im using a ruby 12AX7AC5 HG K tube. I tried running it on 13vac but all i got was a loud buzz or tone and no output not sure why went back to the 18vdc and no noise. My goal is to run the heater @ 12.5 with a wall wart and run the plate a little hotter maybe 24-40vdc, put it in a rack unit and mount it with my EQ. It would have a simple 3 knob gain, tone, and volume control with a footswitch for on/bypass.

18V will do a great job of reducing the life of your tube filament. The 13VAC made a buzz because it's AC rather than DC, and tube plates need the smoothest DC you can get.

[vigilante397]

Your results with other power supplies seem to suggest that your valvecaster doesn't work, I don't think 18V will help

+1

I've built a handful of valvecasters. They were originally designed to run at 9v, so if you aren't getting any sound at 9v, you're not likely to get anything at 18v.

[boppy100]

12ax7's have been problematic in the valvecaster.  Try a 12au7 which is what the circuit was designed for.

[GibsonGM]

Look over your circuit. Make it function at 9V.  Then, if your caps in the DC path are rated over 18V, you can go up to 18V.  Make sure you deal with keeping your heaters at the proper voltage, as others have said!  9v on heaters is *ok* but I'd use 11.5...whine is different than buzz....AC will make it BUZZZZ...whine indicates switching power supply without enough filtering, maybe.   

All that increasing the voltage will do it offer more clean headroom, and perhaps slightly better overdrive characteristics.  But those tubes are really meant to be used at higher voltages, so don't expect the world from them.  Nice to get in the game with, tho!    Go find the wiring mistake

It will work with a 12AX7, just sounds a little nicer with 12AU7.  If that's all you have, use it to troubleshoot why it's not working...

[stallik]

I've built a number of Valvecasters and while I agreed that current store bought 12AX7's don't alway sound as good, older tubes from Philips, Brimar and Mullard sound about the same as a 12AU7. Just saying.

[mountianjustice]

  Thanks for the feed back the 13vac i was using was being run through a full wave bridge rectifier made of 6a2 diodes so it should have been dc current. Now a question is there a way to reduce the 18vdc down to between 10-13 vdc with a resistor? Other than the voltage concern on the heaters my valvecaster is dead quiet i also installed the big muff pi tone circuit, a power filter cap and a bypass footswitch. Its unbelievable how much gain this thing produces and it colors my sound perfectly

[GibsonGM]

You COULD use a resistive voltage divider, if you don't violate their power rating (which would be easy to do), but it would be easier to either use an LM317 made adjustable over that range, or just use a LM7812 to get 12 V. It will be much more stable, worth it in my book....

Are you filtering after your rectifier?  No noise?  Must be ripple-free enough, then...



** modified because I made an embarrassing math error re. the 13VAC....which should rectify to a little less than what the heater wants but is ok **