amp tonestack

[El Heisenberg]

Hey ive tried using two fetzer stages with various tonestacks from ROG circuits like thundercheif, uno, umble and english channel.
I jist get too muh signal into the amp coz its just whirs and hums wjen the volume pot is up. I can get a good clean tone with the pot down. But i cant use any of the controls.

I cant seem to get anything but a single passive tone control and a fetzer before the tda2003.

[BAARON]

http://amps.zugster.net/articles/tone-stacks Have you seen this?

[El Heisenberg]

Yea i built a couple of those in a splitter i made to play to fuitars into one amp. I chose two different tone stacks driven by one jfet. That was a while ago.

I dunno why i cant get this to work for me. 

[El Heisenberg]

http://www.generalguitargadgets.com/richardo/practiceamp/craig.gif


Could it be that R2 and R3 need tweaking? Ive messed alot with R2 but not R3. Its always been 22 ohms.

[Brymus]

Hey, why use an lm386 before another power amp IC?

How much power does that tda chip youre using put out?

Im only working with these tda2003s and 2002s cos the other designs i see use bipolar power, which ive never done before and dont have the transforners for.  

I use the 386 because I like the clipping it can generate and it can boost the signal clean too.
The TDA1519b is rated at 12 watts and uses a single sided supply,which is also why I chose it (besides they were .79 each at APEXJr)
I tested it with AA batteries at 12-18V
For your circuit you can ignore all the clipping diodes and just use the clean channel(setting)
Ignore the bass boost switch and just use a 330n cap
Or you can just use the tone stack and HGFV,
If you look at the other schematics I linked to I originally had the tone stack between two HGFVs
HERE is something you might like there is a schematic shortly into the video so check it out.
A 12AX7 pre-amp with a TDA2003 very cool.
http://www.youtube.com/watch?v=8LZRRJvh5A4

[El Heisenberg]

Thats cool. Theres all sortsa cool stuff i see on you tube like that but im ghetto. This amp is housed in an old Wooden drawer from my moms old vanity table. I built the power supply today. Its a 12v transformr rectified then fitered with the lm317. I dont get as much power from it as my other "12v" which put out 16v. The amp really sounds better at higher voltages. Cleaner and brighter.

I finally got the tonestacks to work after one fetzer stage. I can put abother stage after the tonetack without getting overdrive. I just want clean. Ive been messing with the fetzer stages all this time too. Ive tried deluxe and regular fetzers. Also variations that ie seen in their amp sim circuits. Even if i use an mpf102 and the 2nd stage is 1db gain the amp starts to go crazy and buzz and bump.

I might just build it as is. It one low gain fetzer stage with a fender type tone stack minus the mid control followed by a 1M volume pot.

[El Heisenberg]

here's a schem of what I got right now. Any suggestions?

I really wanna get another stage after the tonestack to get as close to a real fender as I can.\\




http://i633.photobucket.com/albums/uu56/el_heisenberg/amp4.jpg

[El Heisenberg]

Ok nevermind the last schewmatic.

here is the full schematic. Please any suggestions, because Im going to sleep now, and when i wake up I will be building this.

http://i633.photobucket.com/albums/uu56/el_heisenberg/amp5.jpg




anything unnecissary, like the source follower after Q1? Anything I should add, like a volume control at the end?? Anything I should tweak? Like the tone section? Anything?

[El Heisenberg]

Eh the dc filter section has errors.

[BAARON]

- No, I don't think Q2 is necessary as a source follower.  Just run your tonestack straight off Q1, where Q2 is attached right now.
- Once you find good values for those trim pots on the Fetzers, I'd replace them with metal film resistors to keep noise down.
- You don't need the 1M, 33k, and 220pF parts following your 1M volume control.
- I wouldn't use the Dumble's mid control for this particular application.  I would stick with the standard Fender tonestack, either with (Twin-style) or without (Deluxe-style) a mid control.  The Dumble mid control behaves rather differently from a Fender or Marshall mid control, and may not react the way you want it to.
- If you want the classic Fender tonestack, use a 250pF cap for the treble cap, and a 250k pot for the bass instead of 500k.  For no mid control (Deluxe style), remove the current mid pot, and attach the bottom leg of that 47nF cap to the junction between the bass pot and the 10k resistor.  If you want a mid control (Super/Twin style), replace that 10k resistor with a pot.

[El Heisenberg]

Ive beeb having trouble biasing the second fetzer stage. It distorts in a bad way after 1.4v on the drain. Im running it at 11.6v It didnt do this when breadboarding it. Ive had it built for a loong timw now, and have rebuit the second stage several times and get the same result. The amp works but, i wonder if it ciuld be louder. Is it just that the 2nd stage will distort with a loud signal??

I also put the input cap to the TDA2003 amp with the positive lead going into the positive input. Opposite the schematic i posted. Is this backwards???

[El Heisenberg]

Or would a limiting resistor like that 33k or a 68k help? I left it out, like baaron suggested. I kep the umble tonestack, and liked it, but decided to see how the fender one was, and its pretty cool. The mid pot as a level is kinda extreme tho.

[El Heisenberg]

Here is a schem of what I actually have built, after all the scrapping and rebuiling I did, thinking it was the amp section or the tone stack that was messed up, when it was the second FET stage, which is circled in red.

I also circled a part of the amp circuit that controls gain or something. the schem calles for 220 - 4k7. Since I couldn't get the second fetzer stage to work without it being pretty quiet, I used a 4k7 to bring the volume up.

I don't know what the 22 ohm R3 resistor is.

[El Heisenberg]

Lo?