About the top of my new guitar amplifier design

This project stopped for years, but the wood case of my new guitar amplifier is ready. The rason of long time delay while I did nothing is that I used my old amplifiers. One is my previous DIY guitar amp have been disasembled, and I have a Carlsbro GLX100 amplifier with Eminence ReadCoat speaker, whats are very good solutions. This is the reason why I don't hurry with my new idea, but now I take apart my old DIY amplifier and the power supply have been moved to the new wood-case.

My old rack mounted amplifier was stereo for guitar, because I  using multieffect. I have Boss GT8, where not only the effects have stereo outputs, this is dual guitar effect, where I can use different amplifiers for left and right channels. This is the reason, why I have combo design but with two speakers for stereo solution:

After the wood case, I have metal cases for electronic circuits:

This is the back of the wood case:

....now without the middle slat because I need space to fix the speakers.

 The power supply built to the bottom of wood-case. I know that all other industrial solution have same case with other circuits on the top, but now I have more space on the top for amplifiers and equalizers. I think the larger distance between transformer and circuits have benefits:

The design of wood case was realy good, I made model of paper, and got to the professional carpenter, who manufactured and assembled:

The bottom of this amplifier is done, this is the power supply. From the power supply the required voltages wired to the top of amplifier case:

Here I have +/- 40V for poweramps, +/-18V for preamps, +24V for LED-s relays, and coolers.

But the most important question is what I have on the top

Because the power supply built to the bottom, I have more space on the top. The power of toroid transformer is 1200VA. I want to place guitar preamplifiers and amplifier (stereo for multieffect), and one more stereo poweramp for additional cabinets for vocal or keyboards. I need parametric equalizer, if I have enough space on the top-case, separated for left and right channels. I need audio mixer with mic preamps for vocal or another audio sources with headphone and line outputs.


But the most important question is, what will be the power amplifier on the top case. On this time, I want to build some digital class-D poweramp maybe for vocal only not for guitar. I have PWM power bridges, what is 1x315W, and I have 2x210W TAS chips:

1x350W with TAS5261 is would be enough for guitar, but this power available for 4 Ohm only. The guitar speakers are 8 or 16 Ohms. On 8 Ohm this chip have 125W output power. Now I think, for guitar (where the speaker is 8 Ohm) I will use bridged TDA7293 chips, where I got 200-220W for 8 Ohm speakers. This chip is very popular on guitar amplifier market, Marshall, Carlsbro using this solution. And for example the Crate Powerblock is PWM poweramp.


Because the vocal or additional guitar speakers have less than 8 Ohm impedance, the PWM chip is good solution. The benefit of PWM chip is the very high efficiency. But the disadvantage is the very small size of chip, TAS5261 have digital PWM inputs only, so I need PWM modulator like TAS5028 for example. TAS5028 is more small than TAS5261, so more harder to build the PCB. Finally the PWM modulators have digital inputs, so I need A/D converter for analog input devices.

I'm not sure that I can build complex design with these very small chips. The another detriment is that the PWM modulator and the A/D converter need 3.3V only, what is used for DVD players orfor computer soundcards. I don't think that the vocal or guitar amplifier design is same as like the home theater systems. The power stage of this idea need only non-symmetrical power voltage, +50V. I have +/-40V for TDA bridged solution, what is much better. I can bridged the TDA chips, but I can't bridge TAS power chips, because this is already internally bridged. At he moment I think the bridged TDA circuits are better and easier to build for guitar and vocal.

I take apart my old amplifier, old circuits for sale

I "disassembled" my good old power amplifier. This version was very good but the part of this device needed to my new idea. I used this old version for 10 years, without problem. This amplifier contains two stereo devices, one for guitar, and one for microphones/keyboards. I built this double-stereo amp to 2 rack mounted cases: one for power supply, and one for the amplifiers.

The old power supply:

It was the old power supply on the rack case #1. The toroid transformer is  1200VA, the Greatz on the heatshink is 10A, softstart, stabilized power supply for preamplifiers and EQ, simple power supply for amplifiers. By the speakon connectors the output voltage can be changed from +/-10v to +/- 70V for poweramps only. One speakon is the output for poweramps, and one 5 pin connector is for preamplifiers and mixers. The toroid transformer have 4x10W and 4X15V output AC voltages for poweramps, and 2x15V for preamps, and 1x18V for LED, relays, and coolers.

This power supply is good solution for my new guitar amp project, but without speakons, because the different output voltages are not required for the new design. Now I have only one speakon for poweramps, and one 5 pin connector for all others:

This is the box of new power supply, assembled from the parts of old one. This case placed to the bottom of new combo. The required power voltages will be wired to the top of amplifier. The content of upper case not ready, and I want to design something new.

The old amplifier:

The poweramp, 6 input mixer,10 channel equalizer built to another rack mounted case. This is old photo with one poweramp on heatshink, but this part of amplifier has been duplicated. One of then used for guitar, the another one is for keyboard and vocal. This is all-in-one sulution, but for small or larger clubs was good solution:

There are the list of very good circuits what I don't  need for new amplifier design, so there are for sale:

4x200W poweramps with TDA7293 assembled to heatshink with cooler:

The poweramps are two stereo circuits with bridged TDA7293/7294 circuits. Very reliable circuits. All stereo boards have speaker protection with UPC1237 chip.

The equalizer:

10 bands stereo RANE copy equalizer. This is active filter circuit design, the "Q" of EQ is permanent for all bands, what is very interesting solution. See more... With small PCB relays the have true bypass, and the circuit can be switch between +/-6 and +/-12 dB modes.

6 input audio mixer:

Very simple audio mixer with 6 stereo inputs. All inputs have gain and volume pots. Two of them have jFET preamplifiers for guitars with 4x gain, 4 of them have op-amp preamplifiers for all others with 100x gain.

Here are the gallery of my "disasembled" but error-free circuits and prototypes. Write me if you need something:

The power supply moved to new amp

The power supply of my stereo guitar amp is moved to the new place and ready. The old circuits can be fixed to the new "box", what is smaller but higher. The toroid transformer is 1200VA, with 4x15V, 4x10V AC for high power circuits, 2x15V AC for small power circuits, 1x18V AC for relay and LED. The DC and 24V AC voltages wired to the top of combo with 5 point cable, the +/-41V DC power for amplifier wired with speakon connector to the top of amplifier case:

New power supply with 48V phantom power and 24V for relays

I have simple power supply for my preamplifiers (and all other) projects, but the 48V phantom power is missing from this device. This required for micrphone premplifier only, if the source is condenser microphone instead of dynamic microphone. Condenser mic source is useful on studios, for live singing, home amplification the simplest and cheaper dynamic microphones more useful. I searched some good solution, but the circuit which convert 48V from 30V AC is not simple enough. IT is true, one transformer not required with this circuit, but I think small PCB transformer with 48V (or 2x24V) is good and cheap solution. This is the reason why 2 transformers inserted to my design. The another thing with this new power supply, that I like relays to switch something if required, therefore I made one more output for 24V for relays (for example switching audio input, or switching speaker protection).

In current design the AC input is for 230V, because the PCB transformers soldered to the board. I like LM317/337 pair of adjustable regulator, the result is much better for me like 78xx/79xx circuits. The output voltage depend on the zener diode connected to the adjust of regulators. All regulators placed to the edge of board, if heatsink required.

The simple schematic:


The PCB:


If 24V for relays not required:


The original PCB for +/- 15V only without transformers:

PCB sales of this project Module name Size (mm) Area (cm2) PDF SCH PCB image Tested Price (US$) Des. Sim.1 Full2 Sim.1 Full2 Man3 Power supply for preamplifiers 168x89 150 No Yes Yes - - No 22 32 Ask How to order? Please read the rules carefully!