Some nice little project articles of interest

[Mark Hammer]

The Everyday Practical Electronics website has some project/cookbook articles from nack issues here: http://www.epemag3.com/index.php?option=com_docman&task=cat_view&gid=56&Itemid=38

Among them are a slightly improved version of the SSM2166-based Q&D Compressor from Jack Orman's site, a TDA2030-based guitar practice amp complete with op-amp front end and pads for PC-mount jacks, etc., and an article with a compendium of low-power chip amp circuits (with PCB layout/mask) for those interested in the TBA820, LM386, LM380, and TDA2003.

Definitely worth a look.

[GREEN FUZ]

Thanks Mark, a very timely post. I`m looking into building a small practice amp and I have some of those chips you mentioned.

[B Tremblay]

In my experience, all of those chip amp circuits benefit greatly from an input buffer.

[Mark Hammer]

Cogent point.  Indeed, all of them likely assume that the signal source will be low-ish impedance, which one's guitar certainly is not.

So yeah, if you're going to adapt one of the power-amp chip circuits for your dorm room or summer cottage amp, make sure to stick some sort of input stage in there too.

[jrod]

Curious! What is the importance of a buffer in these chip amp circuit. Are they overloaded without one? I have a thread regarding impedence bookmarked, but have not have not read it yet. Any brief comment would be appreciated.

And, thanks for the interesting links, Mark!

jrod

[GREEN FUZ]

I was thinking of building the TDA2030 based practice amp using a valvecaster as the front end, which I believe can be adapted as a buffer. Question is, would I even need to adapt it or could I just slap it on and be done with it? I guess I need to answer my own question by trying it.

[Mark Hammer]

Curious! What is the importance of a buffer in these chip amp circuit. Are they overloaded without one?

No, they're not overloaded.  They just won't sound as much like your guitar as you'd like them to.

Note that, if you have a clean booster pedal of some kind, or even a compressor or an EQ pedal for that matter, you should have no qualms about plugging into one or more fo them and then into any of these power-amp circuits.  They accompl;ish what needs to get done.  What ROG-master BTremblay and I were simply trying to avoid was people thinking they could make a little power-amp circuit, plug their guitar directly into one, and sound decent.

I might point out that the "guitar practice amp" ( http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=184&Itemid=38 ) does have a TL081-based input stage.  It is the simple power-amp circuits here which do not: http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=197&Itemid=38

[jrod]

Curious! What is the importance of a buffer in these chip amp circuit. Are they overloaded without one?

No, they're not overloaded.  They just won't sound as much like your guitar as you'd like them to.

Note that, if you have a clean booster pedal of some kind, or even a compressor or an EQ pedal for that matter, you should have no qualms about plugging into one or more fo them and then into any of these power-amp circuits.  They accompl;ish what needs to get done.  What ROG-master BTremblay and I were simply trying to avoid was people thinking they could make a little power-amp circuit, plug their guitar directly into one, and sound decent.

I might point out that the "guitar practice amp" ( http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=184&Itemid=38 ) does have a TL081-based input stage.  It is the simple power-amp circuits here which do not: http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=197&Itemid=38

Thank you, Mr. Hammer! I see, so the above mentioned pedals act as a buffer. Otherwise, a simple buffer could be added to the beginning of the circuit and it should sound like a decent guitar practice amp. Interesting stuff, man. Thanks again!

jrod

[Mark Hammer]

Correct.  And welcome.

[Ben N]

Neat little tuner project--could use a tighter  layout, but that's for us to do. The StyloPic strikes me as a novelty (can't make much in the way of music with a stylus on a flat "keyboard," I reckon), but it also looks like maybe the foundation for a top-octave-generator substitute project--bass pedals, anyone?

Thanks for the very neat tip, Mark.

[GREEN FUZ]

I might point out that the "guitar practice amp" ( http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=184&Itemid=38 ) does have a TL081-based input stage.  It is the simple power-amp circuits here which do not: http://www.epemag3.com/index.php?option=com_docman&task=doc_download&gid=197&Itemid=38

I had in mind to replace the TL081 with a valvecaster but I`m going to have a look at those other circuits also.

[Taylor]

Neat little tuner project--could use a tighter  layout, but that's for us to do. The StyloPic strikes me as a novelty (can't make much in the way of music with a stylus on a flat "keyboard," I reckon), but it also looks like maybe the foundation for a top-octave-generator substitute project--bass pedals, anyone?

I guess you're not familiar with the Dubreq Stylophone, which that project's designed to emulate. Rahsaan Roland Kirk even used one in between playing two saxophones and nose flute all simultaneously. It was probably many people's first synthesizer.

Music from Outer Space also has a DIY synth controller that works the same way:

http://www.musicfromouterspace.com/analogsynth/MFOSMINICONTROLLER/MFOSMINICONTROLLER.php

All that said, it is kind of a novelty. But those can be fun.

[Ben N]

Yeah, my point of reference was the old Paia Gnome, the difference here being the discreet tuned keys. I'm sure there are virtuosos at pretty much anything, but the need to move around with a stylus, as opposed to using one's fingers to play non-adjacent notes, strikes me as a pretty serious limitation.