Battery Operated Guitar Amplifier 8-9 Watts

This audio amplifier schematic and guitar/harp amplifier project is a class AB audio power amplifier using a TDA2003 module power amplifier.

Output is 8-9 watts

It includes two JFET preamplifier stages and a bass boost tone control.

This Guitar/Harp amplifier uses a Cabela's Rechargeable 12-Volt Battery.

And the amp is totally portable requiring no extrenal plug and 8 hours of continous play time on a single charge.

Silvertone 1481 Harp modifications

The Silvertone amp is very easily modified because it uses point-to point wiring. Please be VERY careful when working with tube amps the voltages can KILL you. First thing to do is identify ALL capacitors and short them to ground for a few seconds making sure they are fully discharged.

Here is a list of the modifications that I use on my Silvertone 1481:

1) Add a 22 uf by-pass capacitor electrolyte on the first 2.2K cathode resistor ( this adds more bass. Be sure that the negative side of the cap is to ground)
2) Replace the second 2.2K resistor with an 1.5K resistor (This adds more gain - don’t do this to the first tube stage or you will get too much feedback)
3) Move the volume control from the first preamp tube stage to be last thing just before the output stage, just after the tone control (this allows creamy preamp tube distortion at any volume level)
4) Replace all .01 uf coupling capacitors with .02 uf capacitors (this allows more bass and midrange to pass from stage to stage)
5) Replace the 270 ohm resistor with a 240 ohm resistor rated at 10 watts. (this runs the output stage a little hotter, but is still in spec for a 6V6 output tube
6) Replace the original 7 inch alnico speaker with a 10 inch alnico speaker

With these changes the amp will be as good as any harp amp out there. It works great for guitar too unless you’re looking for a guitar amp that does not add distortion.

Good luck

“Tone Slave Master”
The tube amp external lineout box

Do you have that vintage four watt single-ended “class A” amplifier with the perfect tone, but it is not loud enough for gigs?

Do you record music in a noisy environment where miking your favorite amp picks up the “el train” passing by?

Do you want to connect two amps together to mix that perfect tone during live performance, in effect, using your favorite tube amp like an effects pedal?

The “Tone Slave Master” is an external box that attaches to the speaker output jack (or directly to the speaker) of your favorite tube amplifier and attenuates the signal to provide a lineout that connects to another amplifier, mixer or PA system; all without any modification to that precious Vintage Amplifier. The “Tone Slave Master” provides two controls to “dial in” the signal for that perfect tone.

This is not a DIRECT BOX or DI box! It is designed specifically for tube amplifiers!

The kit includes:
A cable for connection via the speaker jack
A cable for connection via the speaker if no speaker jack is available
The “Tone Slave Master” interface box 4" X 2"
And installation instructions

I developed this product because I play harmonica in a band and wanted a device to create the “perfect” harp tone.

My setup is as follows: Shure Green Bullet Controlled Reluctance or Controlled Magnetic microphoneà Silvertone 1481 amplifieràTone Slave Masterà Fender Blues Junior or Fender Bassman amplifier.

And WOW I got the MONSTER tone that I was looking for. The Silvertone 1481 amp has that OVERDRIVEN “Class A” tone and the Fender amp provides the power, bass and reverb needed to accentuate that unbelievable tone.

This works great for harp, guitar or any instrument connected to a tube amp! My guitarist uses one and loves it.

I use it at live gigs, recording sessions - everywhere I play!

I developed this product because I could not buy one! The “Tone Slave Master” interfaces are custom built by me and ONLY me with an aluminum chassis the finest components, hand wired (no printed circuit boards) and tested thoroughly so they sound great and they are VERY rugged – so they can survive the local blues/rock bar.

The “Tone Slave Master” can work with ANY tube amplifier and provides two controls to “dial in” the signal for that perfect tone. Most lineout signals on amplifiers are fixed and are not flexible and therefore sound terrible in most situations, but not the “Tone Slave Master”.

Control one is used to set the “level” of the output signal.

Control two taps off the right amount of wattage to “attenuate” the output signal to match the input device.

This results in awesome quality of tone and sound. To hear the results click on http://www.myspace.com/thebananastreetband and listen to the first two tracks “Inner Life” and “Spinning the Machinery” where it is used on both the guitar and harmonica parts.

Look at the photos to get a feel on how this is used. For further info contact me and I will send you installation instructions or answer questions.