Are there any low-power class D amplifiers that are not crap for guitar amplification

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> Faital Pro 4FE35 4" Full-Range

Reference Efficiency 0.19%

A "real" guitar speaker is 1% to 4%. (JBL E-130 peaked near 7% but was a little big for a backpack.)

The small size is forcing ten times the amplifier power. The small size won't really move a lot of air.

(That's not even considering losses due to lack of box.)

> I test first without a box.

So do it your way.
 

Blue777

Member
2020-11-01 4:49 pm
Done. Thanks all:
 

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john65b

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Paid Member
2005-01-09 2:32 am
Chicago
I made PCBs of my favorite amp - a Roland JC120 (just preamp side). The ultimate undisputed "Clean" guitar amp. Does everything from Jazz to Metal.

I coupled one PCB to an ICEPower 200ASC amp module and it sounds excellent. Also made another coupled to a Gainclone (LM3886). Only one channel, so doesn't do that gorgeous chorus, but can add another channel with a Boss Chorus pedal and achieve that sound....

So good that am now selling my real JC-120.
 

john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
Google my friend....I cloned the original JC-120 schematic with the 2SK117, not the later versions with opamps...

I had a fellow here do the artwork, and I ordered the fab from China. It sounded OK, and it sat in my closet for a while, then I realized the four 2SK117 I used were fake. I replaced them with known real 2SK170 and it sound better than the real one (with opamps).

Dotneck - you wanna PCB to try yourself for free (I had to make 20 pcbs)?
 

john65b

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Paid Member
2005-01-09 2:32 am
Chicago
Ha, I found it on my laptop...

Also attaching what I built...I removed the third 2SK117 - the one right after tonestack - plenty of gain.
 

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dotneck335

Member
2012-12-11 10:10 pm
@john65b: THANKS for the free PCB offer! But no, I was just nosing around trying to find a schematic for my Roland Micro Cube. Which has NOT been successful! I do see that the Roland JC-120 and 40 others are listed but NOT the Micro Cube--for some unknown reason. Glad that you are enjoying your homemade Tele. My Gibson ES-335 is an oldie but goodie, made in April of 1961, and has the super-thin neck made only that year of manufacture; I absolutely love it!! It's the best electric guitar I have ever played, and that includes a '59 burst.
 

NickKUK

Member
2019-12-28 9:16 pm
Hi Guys,
I have tested PAM8403, PAM8610, OEP20W cheap modules (class D) with a basic op amp stage preamp. All they sound like crap or too low. The same preamp sounds just very good with TDA2030A but TDAs are very inefficient in terms of power dissipation. I like Class D because they are cheap, small, and require very small heat dissipater, but why they sound like crap? Are there any practical module for this use? ideally with a power supply between 9v and 19v.

Notice: I am specifically interested in using this thing as guitar Amplifier. I am not interested in hifi.

Sounding like crap is more targeted todo with the sound (harmonics), gain/overdrive and speaker distortions scaling with volume level.

The reason they probably sound like crap probably one of three things:
a) there is nothing to give the classic/desired sound so Class D is all you get
b) the surrounding power supply and filtering is done on the cheap
c) the speaker they're hooked up to is also done on the cheap

It depends on what you want out of a guitar amplifier.

I'd probably go with a small tube preamp front end, it would allow you to shape/distort then let the D class then simply provide the current and final output amplification.

I used to have an old Marshall 5W practice amp.. but it disappeared (I think it got thrown out) but looking back on it now it would have been perfect to modify.
 
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Printer2

Member
2010-04-02 6:34 pm
Google my friend....I cloned the original JC-120 schematic with the 2SK117, not the later versions with opamps...

I had a fellow here do the artwork, and I ordered the fab from China. It sounded OK, and it sat in my closet for a while, then I realized the four 2SK117 I used were fake. I replaced them with known real 2SK170 and it sound better than the real one (with opamps).

Dotneck - you wanna PCB to try yourself for free (I had to make 20 pcbs)?


I bought some 2SK117's (green) and I am not sure if they are fakes or not. Any way to tell? I was planning to do a simple preamp also.
 

john65b

Member
Paid Member
2005-01-09 2:32 am
Chicago
Look at the top of the transistor - you should see a small rectangle on the seam joining the two parts - flat side and "d" side.

That little rectangle should be right smack in middle - centered on seam. Fakes are offset to one side on the 2SK170 and 2SK117.

Also, the Drain-Source resistance should be around 50 ohms for the 2SK170, unfortunately I cannot remember what it was on the 2SK117...

This may or may not be factual (I found all this out here on DIYAudio), but have no reason to not believe....made huge difference in my guitar preamp and a pacific phono stage that sounded ok/crappy for longest time due to "fake" 2SK170.