[AMP] 9V Mixed amplifier

[Hollycez]

I was just wondering if what I was thinking has some kind of sense or if it is just bullsh*t.

I am thinking of building a 9 volts (with power supply, not battery) amplifier made up of 3 different parts:

- Bulbamp (by Tiago Charters de Azevedo) as Power Amp



Question: 1)is it possible to cascade 2 or 3 bulbamp to increase Power to 2-3 Watts?

2) Where should I put a pot for master volume?

- MXR Micro Amp clone as a Pre Amp (I was thinking also other pedals, OCD, klon like...)







- Some kind of Tone Stack (Fender, Marshall or Vox)







Question: Where should I put Tone Stack? I think it should work between Pre Amp output and Power Amp input isn't it?

It would be my first project of an amp so please be kind if it is not possible or if I made errors! 

[antonis]

You may take a look at a "basic architecture" from Elliot Soud Products:
http://sound.westhost.com/p-list.htm


and it's revised version:



Both of them use bipolar PS but you can easily modify them to +9V (by connecting all non-inverting, Tonestack & Volume grounds to a 4.5V from a voltage divider - you can also keep tonestack GND by seperating MID and Volume pots..)
You can omit the respective items for Hi-Low Inputs, Bright switch, Clipping diodes & Output buffer..

[Hollycez]

Thanks a lot for the advice! Is it possible for something like this to work?

[PRR]

Welcome.

> cascade 2 or 3 bulbamp to increase Power to 2-3 Watts?

1) The MAXimum efficiency of that topology is about 6%. So 3 Watts output is about 50 Watts of heat to dissipate.

1a) The maximum efficiency of that stage is not with Drain biased to 50% (4.5V), but rather less, around 30% (2.7V).

1b) The nearly 4V at 8 Ohms suggests a peak current like 0.5A, but the 12V 3W lamp is clearly a 0.25A device, and less at the lower voltage. This really is a 0.1W-0.2W amplifier, small bedroom.

2) On a 9V supply, the "ideal" maximum output is about 3V rms. (9V/2.828= 3.18V) (The BulbAmp won't do so well.) 3Vrms is about 1 Watt in 8 Ohms or 2 Watts in 4 ohms.

You probably want to be looking at "bridge tied" audio amplifiers. Many of the car-radio chips will work on 9V, at around half their claimed output on 12V. This puts you at 2 Watts in 8 ohms or 4 Watts in 4 Ohms which meets your spec.