lm3886 guitar amp?

[nobody special]

Very cool... I love the wood cabinet!

 

[gideon]

Very nice!

quite a big heat sink

 

[blindsjc]

Impedance Mods for Guitar

Hi friends,
I was searching info about a LM3886
guitar amp and found this great topic.

I made a LM3886 amp based on this:
http://sound.westhost.com/project19.htm

So, I wonder how to apply the output impedance
mods to make it more correct to a guitar according
to KSTR info: http://sound.westhost.com/project56.htm

Can I make this mod with this amplifier?
Can someone help me to implement it
in the correct way.

Thanks a lot for any info and sorry about
the newbie question and poor english...

Blindsjc

 

[Moen]

Hi,
Is it possible for you repost the schematic?

 

[neila]

From 11 years ago? That's a bit optimistic!

 

[Gnobuddy]

Hi,
Is it possible for you repost the schematic?

Electronics technology has changed considerably during the eleven years between 2007 and 2018. Today you can buy inexpensive class-D audio power amplifier modules that - for use as a guitar amplifier - have enormous advantages over the old LM3886.

Those advantages include: much smaller size, much lower cost, much lighter weight, and improved reliability.

Rod Elliott himself - the source of the LM3886 amp being discussed here - points out that class AB "chip amps" such as the LM3886 are poor choices for guitar amplification. Instrument amplifiers are worked much harder than Hi-Fi amps, and there simply isn't a way to get the heat out of the chip fast enough to build a reliable guitar amplifier around one. (That hasn't stopped some famous brandnames from making unreliable guitar amps using class AB chip amps.)

As to the question of modifying the amplifier for high output impedance, one of the simplest ways of achieving almost the same result is to wire two guitar speakers in series, and then wire the combination to the class-D amplifier board.

Why not start a new thread of your own, so you can get up-to-date suggestions from other diyAudio members?


-Gnobuddy

 

[Tubelab_com]

the LM3886 are poor choices for guitar amplification......technology has changed considerably during the eleven years between 2007 and 2018.

Back in about 2000 I was a cell phone designer, and Tubelab was still in the "concept" stage........My home stereo was made by Carver, and my guitar amps were a mix of solid state and tube. We were buying IC chips by the MILLIONS for cell phones, and most of the linear stuff came from National Semi, and Motorola, two chip companies that no longer exist today. At this run rate, the semiconductor company's sales engineers were willing to give us parts for ANYTHING, including home projects.

Free silicon was the motivation for most my audio, microprocessor and RF projects for the 41 years I worked at Motorola. Free tubes from discarded electronics were the devices of choice from the 60's until I got the job at Motorola, but the late 1990's and early 2000's was when I got back into tubes.

The LM3886 was the hottest audio chip available around the turn of the century, so I got a stick of free chips from the National guy, and built amps, mostly guitar amps. National also made some stereo preamp chips intended for HiFi applications that had SPI programmable tone controls, no pots needed. I used them too. WHY? Because the tone settings could be stored in memory and recalled at the stomp of a foot switch. One of the stereo channels was used for "clean" and the other was used for "nasty". Like my "Turbo Champ" tube amps, no two were the same. A couple even had some germanium transistors wired in a Fuzz Face circuit in the nasty channel. Judging from the half empty stick of chips I still have, I built 8 to 10 amps.

I used a PIC chip for control, some left over power transformers from a TV satellite receiver job, some even used cheap car audio speakers from a failed K-Mart store. I didn't push the 3886's anywhere near their limits, I think my amps made 35 to 40 watts, and maybe that's why they never blew up. The amps were well received, but that was in 1999 through about 2002. I fed mine with a Zoom 505 And a Maestro Wah - Wah pedal (remember those) and a cheap Squier Strat. Most went to metal and hard rock players, who played them in a similar manner.

Would I use a 3886 chip today......well I haven't since the early 2000's, and I still have 10 of them. Sadly the SPI controllable preamp chips vanished from the market years ago. I think that was what made the amp unique, not the LM3886.

Like Gnobuddy said, the solid state amp world has changed a bunch since all of this happened. There are Class D amps with serious power available for cheap. There are plenty of cheap power amp boards on Ebay, Parts Express, and others. You will still need some sort of DIY guitar preamp with volume and tone controls.

Check out this thread to see if TI is still selling these boards cheap. I got the 600 watt version, plugged my ADA MP1 into it and proceeded to rattle the speakers loose in their cabinets......With 600 watts, you can get seriously loud without getting anywhere near the point where the amp gets into the digital nasty zone.

TI Class D EVM Board 50% Promotion

Zoom 505 demo (remember this was the 90's)

YouTube