valve preamp.

[roflol]

now with my new fetish for submini valves i've found some that run with a plate voltage of around 15V and have a low enough current draw to not eat there way through batterys like theirs no tommorow.

now i have a few questions i want to ask before i go into designing this, what kind EQ do people want with their basses? Would you want to be able to control the gain on the bass and get a tubey grind coming straight out of the jack and at the flick of a switch / turn of a knob go back to a clean sound? Are you opposed to using two batterys(would make them last longer due to not needed voltage doublers)?

thanks for any input into this! its something i've been thinking about for a bit and may be offering for sale as a DIY kit or as complete in a box / put into your bass for you.

 

[lposavad]

"Put in your bass" may be too ambitious. There's a lot of mechanical shock and vibration in an instrument, much more than a stomp box would experience in a typical session/gig.

 

[vin*tone]

Are you talking about space charge tubes?

http://www.duntemann.com/12vtubes/12vtubesindex.htm.

I think putting valves in a bass would be more trouble than its worth. They need ventilation.
Why not build it into a stomp box?

 

[roflol]

"Put in your bass" may be too ambitious. There's a lot of mechanical shock and vibration in an instrument, much more than a stomp box would experience in a typical session/gig.

there fine with adaquate padding etc.
i'd be using submini valves there very small, This project is very doable.

 

[i_got_a_mohawk]

I looked into it a while back but never did it, even drew up primitive plans for a gain only preamp which could be powered by battery (well, passive tone). But would have loved to have one powered by phantom power, that would have been cool

 

[T-Bird]

Hi.

Why go all the trouble of using battery power?

Any TRS or XLR can be used for injection if modulation seems to be too expensive/difficult. SWR injectors OTOH have been around for ages AFAIK for RF.

There's a few 12AX7 based onboard pres IIRC.

Regards
Sam

 

[MultiScaleMale]

I've seen these on acoustic guitars. Never tried one though.

 

[Angus]

You'll have to use a phantom power or similar setup. They draw way too much current for batteries to ever be a logical choice.

Have fun keeping the finish on that thing. Hope you tuck the wires away well!

(<----- also thinks stompbox is a better idea)

 

[bongomania]

I remember seeing pics of a German boutique bass brand with a 12AX7 pre onboard. It had a chrome grill plate over the tube, both for ventilation and so onlookers can ooh and aah at seeing a tube there.

Even though I'm sure it would be possible to create a low voltage submicro tube circuit, it seems to me the current draw would just eat the batteries in no time flat. So here's another vote for a remote-powered design.

Brainstorm: How about if you build it onto a Jazz plate, with an XLR jack. The power supply could be in a "pedal" on the floor. You wouldn't have room in the cavity for a complicated EQ circuit, but maybe it would work to just have a stacked gain/blend pot and a passive tone pot. The J plate would make it an easy low-hassle drop-in project for buyers.

 

[MultiScaleMale]

Here's the acoustic guitar version that I saw previously:

http://www.takamine.com/?fa=elec_cooltube

They're claiming 24 hours from 4 AA batteries.

 

[roflol]

[Invalid or Expired Link Removed]

the valve on the left is a bit smaller than a normal ax7 but you get the idea of the size there about 3cm long and a cm across, they only draw about 20ma whereas a 12au7 will draw around 300ma, I think the battery life will be acceptable and should last alot more than 24hours! the plates wont be being starved aswell so it should give some good clean tones.

i like the idea of fitting it to jazz plates! also the beauty of valves is how simple they are so it'd be very easy to fit a 2 or 3 band eq in maybe even an active eq, although that might end up making the signal far to hot.

 

[ZombiCrow]

I would like a pre that was filter or shelving-based, for for uniqueness, and since there's a tube in there why not a way to overdrive it? Also mount it behind a clear and perforated piece of acrylic so the glow can be seen and it can be ventilated? Minitubes are awesome, and I think more pedals should employ them.

 

[roflol]

I would like a pre that was filter or shelving-based, for for uniqueness, and since there's a tube in there why not a way to overdrive it? Also mount it behind a clear and perforated piece of acrylic so the glow can be seen and it can be ventilated? Minitubes are awesome, and I think more pedals should employ them.

they unfortunatly don't glow and get hot! i was thinking about having a gain knob or something to control gain! shelving would be a bit complicated to put into a bass i think