Amp discovery!

[Sensei Tim]

Success!

Isolated the grounds and power for the preamps from the amp and retouched the grounds on the amp and I’ve eliminated the hum on the dirty channel and almost got rid of it on the clean channel.  I suspect that my rats nest of wiring has something to do with it lol. I’ll spend some time cleaning the wiring up and maybe using shielded cables

[Kinski]

Man that is AWESOME! How does it sound?

I really gotta do another amp build with these boards. Mine is just built in a small box with a small speaker for easy/lazy practicing.

[Sensei Tim]

the JC-120 sounds fricking amazing!  i can totally see why this amp has the reputation it has!    i want to try it out with some chorus and see what happens!

the dr boogie sounds huge but for some reason it doesn't sound as tight as it does when playing thru a tube amp. i don't know if this is because the tube amp colours the sound a bit or what.  I'm thinking a mesa-style 5-band EQ would make a huge difference here.

Also a casual observation:  i was running through an 8ohm cab and while it was loud (took the dr. boogie to 50% volume) it didn't sound 60 watts loud... the 10 watt mode on my mesa is *WAY* louder than this at 1 on the volume.

also another observation.  these hammond enclosures are very light and flimsy that the weight of my speaker cable is enough to almost drag it off the top of my amp and bring it onto the floor.  Plus for some reason i couldn't get clean drill holes on it... there was always a rough burr on the holes.

[rocket88]

The issue with the lower output is due to the ohm rating of the speakers. There power amps put out their max output running at 24V and 4ohm speakers. At 8ohm instead of 60watt I think it's closer to 20watts. Plus when comparing tube watts to solid state watts you really need to double the tube amps rating to make it a fair comparison. So a 10watt tube amp puts out roughly the same output as a 20watt solid state amp. Case in point my 22watt Bugera tube amp puts out significantly more then my old 20watt solid state Fended bass amp. I can gig with the Bugera, couldn't use Fender in a practice setting.

[Chris mudd]

So I'm getting very close to finishing this one up, I am putting together the tonemender with black face preamp and the amp in a box. Looks like it's going to be pretty cool, I'm having a blast putting it all together!
 I do have one remaining question. I would like an LED wired in with the switch to tell me I have power. I'm doing this at 24 volts and just got an Electro Harmonix adapter to power the whole thing. How do I step down the power to the LED to make sure I don't blow it up like a firecracker. I have been using a resistor with a regular 9 volt power supply. But I'm a little uncertain about what to use to get from 24 volts down to the LED.

 Any suggestions would help!.

Thanks !

[rocket88]

what i did was i have the 24V go to a separate board that spits the 24V coming in into 3 different outputs. 1 that goes to the power amp, 1 that goes to the preamp, and 3rd goes to the regulator that brings the voltage down to the indicator. i used a standard jewel indicator, so i brought the voltage down to 6.4V i believe. you want an LM350 regulator, and just follow the schematic online for it, and use a calculator to see what resistors values you need.

side note, mine is finally done.



so it's time to make another mini amp.

[Sensei Tim]

that looks awesome!


on a somewhat unrelated note i was sitting in traffic last night and had a thought:  these little amp boards are efficient (little heat generation) and run off 24V DC so it got me thinking... any reason why i can't get 2 (or 4!) of these 60watt ones, put em in an appropriate enclosure and use them as power amps for my car speakers?  1 amp per speaker (.. crossover and then woofer/tweeter) and run a power line from the battery and use the remote switch from the head unit to run a relay on to power the amps when the head unit it on.  the only thing i'd be concerned about is heat in the summer cooking one of them..

edit: just had a brain fart and realized that car batteries are 12v, not 24v.

[Kinski]

If you can get the power worked out, I dont see why not.

I first found out about these little boards from a home audio forum where guys were using them to make home stereo systems using two of them with great results.

[rocket88]

Actually some of these are designed for that very purpose. You can do it, just search online and I'm sure you'll find it. I've had the same thought, mostly to be a separate power for the subwoofer in my car, came stock. But have not had time to search for tall the details.

Also glad tou dig it Tim. I'm happy with how it turned out. Have some NOS orange amp tolex I got cheap to cover a mini OR120, that may be the next one. And no joke, before you put up the Laney preamp I was thinking of doing a mini laney supergroup. Idk, maybe I'll do that next. Too many choices. Lol

[Sensei Tim]

Let me know if you build that laney.  I think I have everything correct in the schematic but need another set of eyes. I still need to get the presence control sorted.

Would the 100 watt module work? Not sure if that has enough power to drive a sub.  When i built the stereo in my precious car I had an art 600.2 (I think) amp driving the component speakers which was putting out 150 Watts per channel if I recall and a JBL amp driving a 12” JL audio sub in a sale  enclosure that I made into a false floor. I think that JBL was bridged to several hundred watts.

how do you think these would sound when supplied with only 12v?

I’m still sad that someone broke into my car and stole all that stuff... it was probably 100lbs worth of mdf plus the amps and speakers.  Wish I had photos of it.

[Chris mudd]

This falls under the Duh category.....

What if I just look for a 24 volt indicator light. I can't imagine an LED burning up that many amps. That way the preamp, the amp and the light all run off 24v.

Am I thinking straight?

[Sensei Tim]

I made a voltage divider for mine.

On Thu, Feb 1, 2018 at 7:43 PM Chris mudd [via Guitar FX Layouts] <[hidden email]> wrote:

This falls under the Duh category.....

What if I just look for a 24 volt indicator light. I can't imagine an LED burning up that many amps. That way the preamp, the amp and the light all run off 24v.

Am I thinking straight?

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[rocket88]

If you put a large enough CLR you can drop the voltage down and not burn out the LED. Honestly iI would do what I did. Makes the power wiring simple and neat, plus you don't have to worry about burning out the bulb. If you look for a 24V bulb you might not find one the right size and will definitely cost more then an LED or pilot light bulb like what's in an amp that I used.

[Kinski]

Rocket88, did you make that mini head from scratch? If so! How did you do it? Looks great! 

On Feb 1, 2018, at 9:59 PM, rocket88 [via Guitar FX Layouts] <[hidden email]> wrote:

If you put a large enough CLR you can drop the voltage down and not burn out the LED. Honestly iI would do what I did. Makes the power wiring simple and neat, plus you don't have to worry about burning out the bulb. If you look for a 24V bulb you might not find one the right size and will definitely cost more then an LED or pilot light bulb like what's in an amp that I used.

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[rocket88]

yep. do you mean how did i make the cabinet itself or put all the circuitry together to make the amp?

[zoof]

Can I do it like this?!

(just imagine the preamp grounded :)

[jaredcohen]

Hey Tim, dumb question here. I see the amp, the JC120, and the Boogie... But what's the order of your signal path through those 3? Thanks!

[Sensei Tim]

Input into a 3PDT switch which sends the signal to either the clean or dirty circuit and controls the led. Then from the switch into effects loop (use sometime hung like a split and blend for a parallel loop or a switched jack for a serial loop) and then to the amp and out to speaker.

[jaredcohen]

Awesome, thanks!

[spacefuzz74]

For these mini amps utilizing the TPA3116 Amplifier, is there any reason why I couldn't/shouldn't use the NE555 voltage doubler to achieve 24V?  See attached image for the wiring setup I'm imagining (excuse my playskool-esque drawing)...

Also - Rocket88, regarding your Mini Model T amp (which is super inspiring, by the way):

I know the TPA3116 Amp is 100W, but this is what I gather from previous posts...since the power supplied is 24V and because the amp is solid state w/ 2 ohm output, the actual watts achieved with an 8 ohm speaker is more like 50W.   Is my comprehension correct with this?

Thanks everyone!