Monday, April 5, 2010

Super hard on Pedal.

This was a pretty simple build. I got all of the parts except the stomp switch from digikey. I etch a custom pcb using the toner transfer method. The toner transfered perfectly from some glossy magazine print. pics coming soon.

Lm386 distortion problem.

I finally figured out where the distortion problem was coming from. I simply failed to take into account the bias on the output of the chip.

Saturday, February 20, 2010

Mike R's mini amp

Well after several failed attempts at adding distortion to a simple lm386 amplifier I finally succeeded. Simply adding a switch that changes the first stage of the amp from a gain of 20 to 200 did the trick. I would of thought that adding distortion to an opamp based unit would have been easy. ironic

The unit works great. In fact I want one for myself.

Pics and  a schematic of the completed unit are coming soon.

Thursday, February 18, 2010

Phono preamp

Ive been looking into making a preamp for my dads jukebox. The current amp setup is very tinny at higher volumes. As it turns there is a special filter for phonographs that is called an riaa filter. Record companies use this filter to help vinyl records last longer and increase fidelity.

This leads me to conclude that it may simly be a matter of capitors in the filter section of the jukebox.

Wednesday, February 17, 2010

Completed my first cmoy amp.

Construction of the amp went well although I do have some complaints about the general performance of the amp. First off the amp needs two 9 volt batteries. second the amp distorts at higher volmunms. I understant these problems are related to the tl072 opamp that I had used. In the future I may try a transistor half bridge on the output of each channel to get better performance well maintaining the low cost. this opamp costs $.77 compared to 4-7 dollars for one of the recommended chips.

The sound quality is serperb at general listening volumns. bass is very responsive and tight and the highs are clear but not overpowering. Adding a voltage divider to the input really helped with the noise problems I had with the headbanger amp.  Overall a very good sound that is a little better that the headbanger amp.

Saturday, February 13, 2010

Here are the pics of the first one

Here are some pictures of the first model.

The Circuit is based on on the Headbanger amp project. Newer models will be based on the standard Cmoy style amp. Cmoy should be Superior in sound quality to the headbanger amp and has fewer parts. The reason I started with the headbanger amp was the availability of parts locally (read radio shack).

The exception to the switch in circuit design will be Mikes mini practice amp. This amp needs enough current to drive a speaker as well as headphones making the lm386 chip used in the head banger project a better choice due to its high current capability. The first part will be a preamp/distortion stage based on a lm741 op-amp chip. There will be two types of distortion, tube screamer and overdrive. this will lead into the final stage, a mono block head banger amp. Hopefully I can get all of it to fit in one altoids tin.


Wednesday, February 10, 2010

Headphone amplifiers for sale

I am making several cmoy style headphone amplifiers. Including a special one for mike Robinson that will work as a guitar to headphone practice amp with internal distortion. more to come later including schems and pictures

I got a shinny new Blog

So I dont have to pay for hosting :)