stupid circuit.

[oiseau]

hi,
i just built this thing out of a board with several mu-amps on it which i had lying around (set it on fire lately) http://photobucket.com/albums/a129/eu_anarchy/?action=view&current=tumbbeutelei.gif

to my astonishment it works- has anybody tried that type of thing?! i really have no idea what to think of it.
i would be thankful for any comment.

[petemoore]

  Stage 1 looks like an Fet Mu Amp
  Stages 2 & 3 looks like Mu amps but
  The 'top halves' [Fet] are being used as bias set for the 'bottom halves' [tube], and the top power rail says 30v, ...broken printers is where I get 30vdc from.
  Cool !! on fire you say...lol...how's this sound?
  Looks like it would distort real nice.

[oiseau]

hey,
it's quite precisely as you said (including the power supply- lexmark), how it sounds is a different question; that's why i posted in the first place. i've been fumbling around since yesterday evening and my ears are getting tired ( plus my girlfriend's parrot is going insane- doesn't seem  to like the sound it) so, shortly my ability to concentrate and to judge the quality of the sound has suffered a bit. and yes, it distorts like hell, even with the 12AU7 that's in there. what i'm now trying is to find some saner component values since the current ones are those
that accidentally survived the little fire.

[Connoisseur of Distortion]

wow, that's a weird schematic. had to look at it a couple of times before it registered. 

very cool though. if you can, give us some soundclips. i have a big bin of 12A*7's not in use, i'll try anything.

[oiseau]

hi,
glad about the interest ; soundclips may take some time since the new semester starts today. nbut of course you're happily invited to build your own, it's a rather quick build. i can tell you some tihngs that i'm now certain about though

-as i seem to be too stupid to voice it correctly, mine still has a bit of a nasty sounding high mid-range content, therefore it would be great if
somebody with an understanding had a look at the cap-values
-if you've seen the hand-drawn schem, forget about it, i f***d it up badly; the cathode resistors ought to be something <1k, at least
  with my particular 12AU7, 600 OHMs work best.
-the jfet-driver stage in the front is probably not necessary

altogether i like the way it distorts quite well, i ran a boster 25 ( mu-amp overkill) into it at very low gain and that was rather pleasing; i attribute this to the mid the filter of the booster (see above ). dynamically, i'm already pretty happy with the way it reacts. it always sounds rather dirty and you can control the amount of distortion with picking strength or the guitar volume very well.

got to leave now, do have a good time all of you.

[Steben]

I don't know,

I guess SRPP (push-pull) tube preamp is good enough AND full-tube.
Mu-amps are very good with fet's.

[oiseau]

hi,
the idea was to keep the good tube for producing the sound while replacing the "top half" which doesn't contribute anything to the tone with a jfet which is known ot do the job quite well and even gets the opportunity to run within the parameters it's made for ( ok, admittedly no textbook scientific trail of thought).

[Doug_H]

Look up Aron's "Booster 2.5" or Ed Guidry's "BSIAB" for ideas on how to voice it.

Doug

[amz-fx]

to my astonishment it works- has anybody tried that type of thing?! i really have no idea what to think of it.
i would be thankful for any comment.

There is a tube mu-amp schematic in my Mini-Booster newletter.

http://www.muzique.com/amproj.htm

I built it and got decent results but not sufficiently different for guitar work to dedicate a triode section to it.

regards, Jack