amp tonestack

[El Heisenberg]

heres an amp I built a little while ago. I want to build another one, some desgin, this time with an active tone stack. COuld anyone point something out to me? I tried just sticking the tonemender from runoffgroove before the amp circuit, but couldn't get the right sound on the breadboard, so I just put the fetzer valve there again. Here's the schem for the first amp:

<a href="http://s633.photobucket.com/albums/uu56/el_heisenberg/?action=view&current=amp-2.jpg" target="_blank"><img src="http://i633.photobucket.com/albums/uu56/el_heisenberg/amp-2.jpg" border="0" alt="amp schematic"></a>


And this is what I have on the breadboard:

<a href="http://s633.photobucket.com/albums/uu56/el_heisenberg/?action=view&current=amp2.jpg" target="_blank"><img src="http://i633.photobucket.com/albums/uu56/el_heisenberg/amp2.jpg" border="0" alt="amp2"></a>


Please take a look and any suggestions for tonestacks would be helpful appreiciated. I dunno wether to put it before or after the fezter valve. It's sposed to be an emulation of the fender tube input stage. So I figure it should go after eh?

I have the seymore duncan tone stack calc, but dunno how to impliment it. I tried to measure the input imedance of the fetzer valve, but not sure i was doing it right. 

[BAARON]

If you're trying to emulate a Fender input section and you like Fetzers, you'll probably want a Fetzer, then the tonestack+volume/gain control, then another Fetzer between the TS and the output chip.  It may be helpful to look at some Fender amp schematics to see what you're trying to copy.

http://www.schematicheaven.com/fender.htm has a lot of Fender schematics.  It may help.

[El Heisenberg]

so I don't need anything else but fetzer stages to drive the tone controls?

[Brymus]

I would use an op-amp to drive your tonestack,but even your guitar should drive one to some extent.

[liquids]

Check out the duncan tone stack calculator as a reference....

Tone stacks are influenced by what is driving them....the difference in Marshall and Fenders typical tone stack tone are not just the values, not just what gain stage they follow in the amp, but ALSO how they are driven....the TSC takes this into consideration, and if you click on 'Zsrc' you can adjust it...you'll see that since the fender tone stack is fed off the plate of the tube before it (amongst other factors, I believe) it estimates 38k, compared to the Marshall tone stack, which is fed by a tube cathode follower (a.k.a. buffer) so it estimated 1.3k.

So for one, keep that in mind...

[BAARON]

so I don't need anything else but fetzer stages to drive the tone controls?

You CAN use Fetzer stages to drive your tonestack.  I only suggested it because you mentioned using a Fetzer in your first post.  Or you could use almost any other gain stage you like.

[El Heisenberg]

I have the tone stack calculator i just dunno how to figure out the input impedance and how that works into the sound and response.

[Brymus]

I have been tweaking my chip amp(using tda1519),similiar to yours.
And I tried the Fender tonestack- sounds good.
I tried many,tonestacks from many amps and pedals,actually and I like the Marshall one best so far.
My advice is to just breadboard each one and listen,the best way to decide.
I didnt like driving the tonestack using Fetzer stages before and after,but that was my ears not yours.
The HGFV from the big daddy pedal sounds much better IMO,try that one before and after your tonestack too.

[El Heisenberg]

Id like to keep the fetzer input stage and i guess use a fender or marshall one stack. All id need to drive the tone stack is a fetzer in front, right??

I have the tone calculator and should i just use the default schem thats on the calculator? How do i measure the input and output z of my stages and amp input to enter into the calc. Id like bass mid and treble, gain and vol.

[El Heisenberg]

Im open to anything thatll give me decent bass, mid, and treb. As long as the fetzer is the input stage. Ill do an opamp in there before the tone stack or after it, or another fetzer or sometjing else. Whatever you guys say.I just dunno where to look for what i need. Ive foun plenty of stuff but im not sure its applicable to my project. Im going to regulate the dc after its rectified and ill polly have 14v.

Im working on the deluxe fetzer valve so its perfect.

[El Heisenberg]

Would the fetzer valve be an inapproriate choice if i wanted to use a marshal tone stack?

[BAARON]

It will work. 
Look at the ROG Umble.  http://www.runoffgroove.com/umble.html  It has an early Fetzer followed by a tweaked Fender-style tonestack, followed by another Fetzer, and then two more Fetzers to provide the overdrive.  (The first two stages are the Clean channel on a Dumble, and the last two stages are added in for the overdrive channel.)  You need a gain stage of some sort after your tonestack to bring the gain back up (and maybe provide a tiny bit of grit when your volume/gain control is maxed) because you lose a fair bit of signal going through the tonestack.

[El Heisenberg]

Hmmm i was planning on jist having it clean and using pedals for the dirt. I figured it wouldnt sound good.

[BAARON]

You still probably want a gain stage after the tonestack to recover the lost volume, and provide a hot enough signal to the power amp to make use of its full signal swing instead of wasting its potential and limiting your available output power.

I wasn't suggesting that you add the 3rd and 4th gain stages from the Umble, only that you look at its first two stages as an example of a Fetzer preamp including tonestack.  It's pretty hard to get the first two stages to distort unless you feed them a pretty hot signal.  Almost all the distortion is being generated in the later stages.

[Brymus]

The HGFV I refered to is "The high gain Fetzer Valve" I liked the sound of it better than the original.
I use an op-amp to drive the Marshall tonestack and then a HGFV into a 386 chip to drive my TDA chip amp.
The Marshall tonestack is close to the Fender except it uses a 33K resistor and 500p cap on the treble and then two .022 caps the pots are the same 1M,250K,and 25K.
Easy enough to try if you have the Fender one breadboarded,this gave me better bass than the other TMBs I tried so far.
If you want I will draw my pre-amp up for you to use or mod.I have changed it since I posted it earlier.

[El Heisenberg]

Brymus, that'd be awesome if you could do that.

Im using the TDA2003s that I have. I just want a clean amp, with a tone and stack and use my pedals for all the distortion and stuff.

I got on the computer tonite to draw up a schem of what I was trying to get to work, but now I think i'll try some more things, and draw one up tomorrow. It was a deluxe fetzer valve, then a fender tone stack, then another deluxe fetzer.  I couldn't get it to work for some reason.

[El Heisenberg]

i see in the run off groove circuits that there are jfets right after fetzers valves to boost signal before the tonestack i guess.  Maybe that's why mine didn't work? Not enough signal? the first fetzter stage boosted fine, I tried bypassing the tonestack and the second fetzer. The second fetzer worked fine also. But with the tonestack between them there was no sound at all on any of the control settings.

see:

http://www.runoffgroove.com/tc-tone.png

[BAARON]

That circuit has several gain stages because it's copying a Marshall head, and they have several triodes before the tone stack.  It's a deliberate attempt to get overdrive out of some of those triodes.  The third JFET is acting as a cathode follower to lower signal impedance just before the tonestack to reduce gain loss.

If you look at a Fender design, the clean sound is a triode, then a tonestack, then another triode, and from there it goes straight into the power amp.  You shouldn't need a bunch of extra stages.

If both fetzers worked fine but you lost all your signal when the tonestack was wired up, I'm guessing something was wrong with the tonestack.  You shouldn't lose ALL your signal with a properly wired tonestack.

[Brymus]

Here is the way it sits on my breadboard right now.
I have been using it as a pedal it sounds really good to me through all my amps tube or SS.
I dont use the bass boost switch anymore since adding the 1n34As on the switch adding those in clips the bass pretty good,
It also sounds good on the clean setting.
You can get clipping from the FBL of the opamp,the 2x1N34As to ground (which also sound good after the tonestack)
and also by overdriving the 386 or by upping the gain of the 386 or by any combination of these.
With the TMB tonestack added (which I tried after the 386 as well but sounds better after the opamp)
I can get so many sounds I have been playing it more than tweaking it the last few days 
Anyway I am open to any suggestions-Baaron, anyone else - As I am sure some of the caps and pots could be changed
for different values,
The previous versions might help you as well.basically I changed out the 386 chip for a low power one and changed the MV a little
feel free to change those to your taste.
http://i419.photobucket.com/albums/pp276/Bry928/SolidState%20Amps/12Watt-TDA1519B%20build/386PreAmp_2.jpg
http://i419.photobucket.com/albums/pp276/Bry928/SolidState%20Amps/12Watt-TDA1519B%20build/12WattTDA1519B_schematic.jpg

[El Heisenberg]

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.