Capacitor value substitute on Valvecaster build

[toejammer]

Been gathering all the goodies needed for the Valvecaster http://beavisaudio.com/projects/ValveCaster/ and I'm stuck on these two caps:

C1 47nF
C4 10nF

I can't find any of these locally, and don't really want to wait for a parts order. I've got dozens of alternate values, but wanted to check and see if anything else will work. Mind you I'm also using 12AD7's in place of the 12AU7's listed. Everything else will be per schematic. Thanks !

[Kesh]

47nf can be bigger without any ill effects (just increases effects ability to accept bass). Can possibly be a little smaller too.

C4 is more important as it will affect the nature of the tone control.

You can combine caps to make the values you want. If in parallel just add values. If in series use formula cd/(c+d) where c and d are the two caps' values.

12AD7 is a very bad choice here, it's basically a 12ax7 with more heater current.

[toejammer]

Can I substitute 0.047 uF for the 47nF ? And possibly a 0.01mF for the 10nF ? My problem is that i can't find anything local with the (nF) designation.

The 12AD7's are what I have on hand, and was told in another post they would work well in the Valvecaster.  Is it just the heater issue, or will they require more juice than 9v ?

[Mustachio]

You should use that 12BH7 with your valvecaster build. And use a 12v 1 amp power supply and you will be doing good. Not sure where your at with working on electronics but If you feel comfortable with a little higher voltage Building a voltage multiplier for it will give the circuit more headroom, people seem to like it. The tubes work best at 12v and the current is the amp rating and they usually need a good 500ma or more if I recall. So a 12v 1amp walwart will get you where you need to be.

It looks like the 12AD7 uses about 450ma for the heater current. the 12BH7 around 300ma. You could Do a twin valve caster and run the heater voltages at 6.3v but that will call for more current about double from the datasheet.

http://www.shinjo.info/frank/sheets/137/1/12AD7.pdf

http://tubedata.milbert.com/sheets/127/1/12BH7.pdf

For a nice smooth light overdrive/boost I'd build the standard valvecaster at 12v 1amp with a charge pump to take you up to 50 or more volts. Just be careful working with higher voltages if you do. You can always built it at 12v and see how you like it and then add a voltage multiplier later.

The main thread dealing with the Valvecaster has every bit of info you could possibly need and its a huge thread! If you read through most of this you will be set! http://www.diystompboxes.com/smfforum/index.php?topic=63479.0

It is a cool fun project and it can really add some tube depth to your sound. Its not a melt your face overdrive/distortion its more of a boost with a lil grit, works real nice as a clean boost too. Use it with another overdrive and it will really open up!

[toejammer]

Thanks Mustachio ! I did start reading that thread, but started to lose focus at about 50 pages or so. The 12BH7A would be nice, if I had a pair of em. But I've only seen the Valvecaster schematic w/ duel tubes. My experience with higher voltages was about 10rys in the high end car audio market as an installer. Built alot of high pass / low pass filters, and modified alot of amps to push past factory secs. (this was in the 80's tho, and most of those mods are obsolete now)   

I'm a drummer by nature, but have always been the "guitar tech" in bands I played in back in the day. This however is my first adventure with tubes.

I'll go read up the other 100 pages of that post, see what i can learn !

[Kesh]

Can I substitute 0.047 uF for the 47nF ? And possibly a 0.01mF for the 10nF ?

They are exactly the same thing.

[toejammer]

Can I substitute 0.047 uF for the 47nF ? And possibly a 0.01mF for the 10nF ?

They are exactly the same thing.

Bingo ! Thats what I needed to know, thanks !