DIY Stripboard "SPARKY" Amplifier

[PStevenson]

finished this tonight - plugged it in, it works great and loudly so I hope some of you guys will enjoy it! SPARKY Amplifier and for the hell of it - me singing a Placebo song

[dexxyy]

Nice one Paul, goes near the top of my todo list, haven't got an lm384 in my stash so might try and blah a couple from TI

[dexxyy]

Blag, blag, blag, fkin iPad

[PStevenson]

well as it happens the LM384 are in their sample program so you should be able to get 3 of them

[Freppo]

Cool!

Now I know what to do with the broken old radio I found in the attic.
Been looking for something that is louder/cleaner than the LM386 based amps.
I've already removed all the old electronics and put in a 8" guitarspeaker.

Thanks!

[IvIark]

Sounds great mate, and you've got an excellent voice too, nice one

[IvIark]

It's occurred to me, I've got some LM380N and LM380N8's that I think are equivalents to the LM384 but at 2.5W so I could probably use those.  If I supplied it at around 18V with a charge pump, the extra headroom may make up for some of the losses of using a 2.5W IC.

I'll have to give this one a go.

[PStevenson]

I wouldn't bother with the charge pump, I don't think it can supply the current needed to get the best out of it, the more you drive it with the preamp the more current it uses and I think it'll be over the 100mA that the regular charge pump dc-dc converters can supply.

but I think those 2 amps are pin compatible so if you try it let me know - it will be an interesting experiment to say the least, I know the TDA 2030 and 2050 are pin compatible in that tonesucker amp I made ages ago  http://www.paulinthelab.com/2012/05/tda2030-based-amplifier-veroboard.html

[Jon Rep]

Paul & Mark. I couldn't resist. I had a couple of LM380N IC's so I decided to build the Sparky Amp.
I only had 25 V 470uf so I used that.  I ran it on 9V and it worked fine. It sounds very nice & rich at low volumes and distorts quickly as the Volume is increased.  Maybe increasing the 10K Pot value to higher may help?  Congratulations Paul on the Sparky Amp.  I am glad I had a go building it with a LM380N. Thanks for the Post and Info.  Great Stuff.

[IvIark]

Good stuff Jon, thanks for confirming the LM380 is ok.

[Jon Rep]

No  problems.  I am thinking of using the Sparky Amp as a Bedroom Practice Amp because of the Richness  of its Sound.  I have been playing through it this morning and am impressed.  

[PStevenson]

that has to be the quickest anyone has ever built one of my designs !
the 25v cap should be fine unless you run it at higher voltages than 12v
with the LM384 it distorts but only when you're very near full volume and I think it's because I went with the 741 instead of the TL071 (try swapping?). but by all means
try different pot values and post a comment on the article of any cool findings and mods

[Jon Rep]

Paul, I tested a TL071 but prefer by a long measure the LM741 which to me has a more natural tone.  I am now wondering whether other pedals I have with TL071's may sound like with LM741's.  My build with the LM380N unlike yours does distort quite early but before that I am getting a Big Rich Tone  that is very pleasant to listen to and at a level perfect for the bedroom practice.  

[Jon Rep]

The TL071 also did not improve the level at which the distortion commenced on my pedal.  Testing different pot values might be the go next.

[IvIark]

The TL071 has a JFET input section, the LM741 is bipolar, so the TL071 has a very high impedance input in comparison and so some audible differences like that are expected.   The LM1458 is essentially a 2 channel LM741, so you can try the same thing with any dual opamp builds you've got to see if you notice similar differences.

[PStevenson]

that's cool - I put a TL061 in mine and got different results too.
I know what you mean by the rich sound - when I was deciding on using that IC or another one I thought it was just going to be a twangy piece of crap but it really isn't - I don't know what guitar you use but I used one of these Guitar and you should hear how divine it sounds on the neck pickup

[Jon Rep]

Paul,  I think your build with the LM384 may be  ideal.  Increasing pot values as I should have known seems to only brighten the tone. I prefer your 10K Pot choice.

With my LM380N Build I removed the 1N4148 Diodes and was still getting the distortion coming in early. I figure the LM380N IC being only 2.5 Watt with typical current 7mA rather than 8.5 mA for the 5.0 Watt LM384 may not handle the increase in current in the  same way as as the Volume Pot is increased.  To get my LM380N Build to perform across the Volume Pot Sweep like yours with the LM384  I replaced the 1N4148 diodes with a 1 K Resistor ,  this to my understanding allows more current to escape to earth rather than entering LM380N  IC.    And allows me more control across the pot sweep.

I dont know whether removing the diodes and replacing with a resistor changes the sound quality. To my ears it still sounds Great.

[PStevenson]

the diodes are there purely to protect the IC from voltages going above a certain amount - they probably aren't necessary in this application but I hadn't spent long testing it before I published it so I thought it was better to be safe than sorry.

what I suggest you do is sign up to Texas Instruments and order a few LM384s as free samples and see how you like that because where as I'm sure you're getting the same type of distortion that you get when you push it all the way up - it will mean that you can have it louder before it does distort.

this amp passed my expectations alot though I am already working on the "SPARKY Advanced" which will have a basic EQ and I will spend a lot more time getting rid of undesirables like the distortion

[Jon Rep]

OK Thanks Paul. I will look foreward to the "Sparky Advanced".  It's all Good Stuff.

[PStevenson]

here's a quick sound clip of the SPARKY