sorta OT. practice amp thingie.

[thomas2]

hello all.. i was just wondering if it's possible to build an all tube practice amp (about 1w) that could work with 12V adapter.. i'm really not that much into plugging any selfmade device to the wall and getting a 230V shock, so i prefer things with adapters..
anyway.. if someone knows such amp. please let me know!

[Peter Snowberg]

If you want a micro power tube amp, search here for the "Sopht" amp or visit Stephane's site at http://www.sopht.ca/ Just keep in mind that they won't sound like big tubes at high wattage. They have their own unique tone.

Another option to consider is building one of the Run-Off Groove JFET amp sims and put that in front of a 386 or other small solid state amp. That may be more of the tone you're looking for at low volume.

Best approach.... build them all and compare how they work with your guitar and speaker(s).

[thomas2]

thank you so much! i've already done a few 386 based amps, but i don't like their distortion that much  :lol:

[thomas2]

what about a 12ax7 preamp.. anyone have a schematic?

[Nasse]

Muusikoiden netissä oli juttua Riffi-lehden EF86 kytkiksestä

[thomas2]

kiitti, mutta olis mukava saada joku etuvahvistin joka toimis 12ax7:lla.. ef86:set oli myyty loppuun sen riffin artikkelin takia viimeksi ku asian tiimoilta soittelin ympäriinsä mm. radio duolle  :wink:

[thomas2]

i have a huge pile of old 12AX7 tubes.. can someone tell me where i could get a schematic for simple tube preamp?  

[lightningfingers]

you might like something like the real mctube, if you use a 12AU7 you will get lots of nice clean tones when the gain is at minimum.

[thomas2]

thanks but i'm looking for a tube preamp that works with an adapter.. i still don't wanna fry myself messing around with 230V voltages :wink:
in case you guys haven't noticed yet.. i don't know anything about tubes!
that's why i'm asking if it's even possible to make one..

[petemoore]

here's my take, use what you can...
 I found that running dual 386's like in the Ruby Amp with jfet input, and using something with cool internal [pre-amp] distortion works well.
 Here's what I did...built 1/2 of a Shaka Tube...not too tuff...I 'cheated' and used two wall warts instead of the power supply section...
 Run a distortion or booster or OD into the tube, tube into the amp...makes for some really cool distortion sounds, and the little amp pretty much set for clean...
 I think the tube really adds alot of tone here...nice 'cleans' and heavy/smooth 'distorts' also...
 I used a 30vdc adapter [printer adapters work] for the tubes signal circuit, and a 9VDC for the heaters [measures 11.6vdc with the heater drawing current]....messy wires/ez build.

[Peter Snow]

Try this  http://www.paia.com/tubehsch.pdf  
It's a stereo tube preamp running off a low voltage generated by an unusual configuration of a 4049 (generating +48v).

Also take a look at PAiA's Stack-in-a-box (same web site). It's specifically for guitar using a mixture of SS and tube technology.

Opinions are mixed on the sound produced by tubes running at low voltages, but if your concern is not getting fried, then this could be the place to start.

Good luck.

[thomas2]

thanks man.. those look a little too complicated for me at this point. i'd like a very basic 12AX7 preamp with no other controls than volume pot.
so.. one tube and one volume + a wall wart

[smashinator]

The Ruby Tuby on the Sopht site looks pretty simple, at least compared to most tube builds.

[slajeune]

The Ruby Tuby could probably made a bit simpler.  From my understanding, the last Sopth 12k5 showed me that the distortion comes from the preamp tube.  Therefore, simply replace the 'preamp' part of the Ruby Tuby (the OPAMP and the 12AX7) and replace it with the 12U7 section of the Sopht 12K5.  Therefore, you get real tube distortion (preamp) and it is simply amplified 'cleanly' by the LM386.

Cheers,
Steph.

[thomas2]

ok then.. let's forget the amp thing..  :shock:  i'd like to make a 12ax7 preamp. it's not just for guitar, so i don't need distortion. nor other extra features. just simply a one tube mono preamp with just one pot for volume. i really want the simplest possible circuit so i could learn more about how tubes work.  :wink:  

but hey.. if someone knows how i could add a effects loop to my little gem amp, let me know  :lol: