hybrid mini 12au7 practice amp?

[dan6896]

One day i was looking around the internet for little practice amps with tube preamps. I saw the ruby tubey (but that has too many parts) and i also saw the tube cricket but i could not find a schematic. then i remembered seeing something about a tube boost that runs on 9v called the valve caster.(in case you dont know you can find that here: http://www.diystompboxes.com/smfforum/index.php?topic=63479.0

anyway that gave me an idea for a little practice amp like a ruby or noisy cricket. replace the fet input thing (not sure of the propper name) with a valve caster circuit running into the input of an lm386 power amp. Ill post a schem later

my question to you is do you thing this will work.

in advance thanks for the help.
 

[J M Fahey]

Ill post a schem later

my question to you is do you thing this will work.

Who knows? 
Post the schematic !! 

[joecool85]

Sounds do-able to me.

[dan6896]

schematic attatched

[rowdy_riemer]

I don't know if there is anything to it or not, but I've heard that 12AU7's don't sound too well with anything less than a 48V supply. I haven't tried to find out, though. I've got a 12au7, but I might save that for a firefly amp. The real magic with the ruby type amps is the way the LM386's sound when overdriven. Probably might as well stick with fets or op-amps. Of course, there is one way to find out for sure. 

[dan6896]

im ordering the parts tommorow ill post again when its done. but i only have a 12ax7 and the 12au7 has to come from england so that might take a while.

[J M Fahey]

the 12au7 has to come from england

Well, that doesn't mean too much because we don't know where *you* live.
You might be as close as Jersey and Guernsey or as far as Marambio Base in Antarctica or the middle of Gobi Desert !!!

[rowdy_riemer]

His user profile says New Zealand.

[J M Fahey]

It's a small crazy world indeed !!! 

[Zipslack]

Looks like you're re-creating the Tube Cricket.  Here's a link to a discussion forum with the schematic.  I have a Valvecaster running at 12.6V that I really like...I have not tried bridging it to a 386 yet.

http://www.diystompboxes.com/smfforum/index.php?topic=66623.0

[dan6896]

thanks for the info, Ive almost finished my prototype just gotta build a power supply and then it should be done. i didn't use an 386 because none of the ones i can find work properly, so i used some car amplifier chip amp kit its about 11.5 watts amp sounds pretty good with just the guitar plugged straight in to it.

[darwindeathcat]

Hey, did you ever get this wired up and working? I've had it in my head to do the same sort of thing for a while now... I've got all the parts sitting around, but wanted to see if someone else had made this work (and what it sounds like!) before i give it a go...

[dan6896]

when i tried it with a 12ax7 it didn't really sound very good, so i built a fetzer valve instead and it sounds much better. You could try it with a 12au7 and see what it sounds like. 

[darwindeathcat]

Thanks for the response. Yeah, the fetzer valve is a neat circuit. Easy to slap together and sounds so good! Interesting that it sounds better than a space-charged 12ax7... I do have some 12au7's sitting around, so I might give that a try one day, but I'd have to order some tube sockets, and I'm lazy!

[joecool85]

...but I'd have to order some tube sockets, and I'm lazy!

Heck, at least you're honest!