TDA1519B practice amp

[Brymus]

Thanks Joe I am glad you like it  :tu:
Here is a much better revised version of the pre amp. http://i419.photobucket.com/albums/pp276/Bry928/SolidState%20Amps/12Watt-TDA1519B%20build/386PreAmp_2.jpg
The key to a full yet clean tone lies in the cap on the bass boost switch,
Alternately a two way switch could be used for 3 different settings adding to the 120n
Which sets the knee pretty high around 700-800 hz (with 100n) if I remember right.
Using two 120n caps works well to clean up the flabby bottom end,only requiring a little
more on the volume knob to get the same "breakup" from the 386.
While a 220-330n requires backing off the guitars volume and/or easing up on pick attack to keep from getting flabby sounding.

I also recommend adding the standby switch as in the TDA1519B data sheet.

Also a 2 pole 6 position switch could be added to the OD channels feedback loop for 6 different diode clipping combinations- add some hard clipping diodes to the output on a switch and you have 14 different diode clipping sounds as well as the infinite EQ and gain options.
Another thing is the tone control a full Treble Middle Bass tone stack would allow even more tonal control.
I am very pleased so far- now to finish the power supply and figure out how to make a charging circuit.

[Brymus]

Oh yeah Joe its going through the 386 in all of those clips.
I need to re-record the clean clips to show the difference lowering the 330n in the op-amps feedback loop makes.
I like 120n+167n added in on the clean channel (287n total)
At this point I would say breadboard this for yourself and try it,
I think I have nailed "tube breakup" really well.

I also need to recalculate the filters to provide some real numbers.
But it does sound really good now.

[joecool85]

Oh yeah Joe its going through the 386 in all of those clips.
I need to re-record the clean clips to show the difference lowering the 330n in the op-amps feedback loop makes.
I like 120n+167n added in on the clean channel (287n total)
At this point I would say breadboard this for yourself and try it,
I think I have nailed "tube breakup" really well.

I also need to recalculate the filters to provide some real numbers.
But it does sound really good now.

Thats great work you've done there.  So it goes into an opamp for the tone stack, then into the lm386 preamp circuit, then on to the 1519 poweramp - right?

The LM386 has enough gain that I'm considering doing a passive tone stack in front of it.

[Brymus]

Hey I thought I would give you an update on this.
I tried numerous tonestacks both before and after the 386.
SO this is after many trials.I am very happy and have played it alot it makes a great clean boost EQ,and can get clipping in a variaty of ways.
I have been using it like a pedal in front of my other amps and even my wife commented on how good it sounded(she likes heavy music)It sounds insane overdriving my Valve Jr or 18 watt with it.
It is much more versatile than before and so many shades of rock and metal are available.
The only downside now is the knob count I have run out of room for more,as I used a 25k for the 2 diodes to ground and added a 100K in series to the 1m on the OD channel so that its easy to set the 100K for classic rock then dial up the 1M pot for heavy sounds,And also I have a 47uf on pin 7 of 386 that isnt shown.
Here is the latest schematic - pre-amp only- note low power 386 this time and other subtle changes.http://i419.photobucket.com/albums/pp276/Bry928/SolidState%20Amps/12Watt-TDA1519B%20build/PreAmpAsPedal.jpg
Also I asked a member at DIYstompboxes to draw a PCB layout, it isnt verified yet but it is here http://www.diystompboxes.com/smfforum/index.php?topic=79693.0
Thanx to Sean K for that layout.
I have been using 9V battery and with the master volume it works fantastic, swapping in the lower power 386 helped too.
I really would like to expand it to two actual channels each with its own TMB tonestack.
But then I'm thinking a bipolar V supply would be better too along with mosfet switching so
I will make that another preamp altogether and call this one good.
Except I do plan on adding a rotary switch with a couple of different diode options including a mosfet diode clipper.
I hope someone finds this useful I have spent months working on it finding what sounds best to me.And am very pleased with it.

[joecool85]

Any sound clips of the little beast available?  I love the grind of a LM386 overdrive, it sounds great!