Combo amp Project - Noisy Cricket or Tiny Giant

[PRR]

12V bridge (Tiny Giant) with 16 Ohm load is around 4 Watts.

That's not quite a vintage Fender Champ. Which works very well in studio or small venues. Despite a lame 6" or 8" speaker.

It's often more about the speaker than the Watts. That Thang is a Twelve (big air slapper) and highly efficient, also zingy. At 4 Watts, in a small room it sure won't sound like poop; you may poop your pants. Out on the patio it can annoy all your neighbors with ease. (You have to get way sub-Watt to completely avoid pitchfork scratches on your door...)

[vigilante397]

I agree 100% with Paul. 4 watts through a 12" speaker will be plenty for casual at-home practicing. Fully cranked 4 watts will definitely bother the neighbors. I think the Swamp Thang will be a good fit because it gives a nice full low end. Jamming with a full band you will have a bassist to take care of that, but playing by yourself it's nice to have a rich low end without needing a bassist.

[Jebull]

Ohhh man that sounds like exactly what I'm looking for! Thanks guys!! So ready to get this started. I'll be sure and post some progress pics!

[Jebull]

Hey guys!!! I've ordered all my parts (mostly) and began assembling. Now before I put all these boards together and start wiring them up, is this close to correct?




I'm still a bit confused about grounding: do I take all my grounds and run them to the input where it will be all grounded to the chassis? Would this cause unwanted noise? etc.

Also I have no idea about the power switch, I was sort of guessing. I tried to find some info, but thats the best I could come up with.

Last but not least I'm not so sure on the "bypass" for the reverb either. Look okay?

Any comments or suggestions?


edit:
err I think more like this?

[vigilante397]

Second one is probably more what you're looking for, otherwise your preamp and reverb will be on all the time and you're just switching your power amp on and off.

do I take all my grounds and run them to the input where it will be all grounded to the chassis?

Yes. Pulling all the grounds together to a single chassis ground point is called star grounding, and is generally regarded as a good idea.

The bypass for the reverb will work. If you wanted to do true bypass you could do something like this:



This grounds the input of the effect when it's not on, reducing any chance of noise.

Quick question though: Any particular reason you want a voltage doubler in front of the preamp? J201's can handle 24V, just wondering why you decided that's what you wanted.

[Jebull]

Excellent!! Yeah I threw that first one together and posted it, then I was looking at it and realized I had the switch in the wrong place haha.

On the Voltage doubler.. I saw where some people said it sounded more "right" with it (etc). I plan on trying it out before I totally commit. I may not use it at all, but it was small and easy enough to build so I figured I'd try it out. I even went ahead and made sure all my components could handle the 24v.

Opoh yeah I'll change that switch around for the reverb, thanks!

Oh and is that how I would wire up the speaker Jack? I just kinda tacked that on as a placeholder. Is that actually how it would go?

Thanks!! 

[vigilante397]

Oh and is that how I would wire up the speaker Jack?

Yup. The Tiny Giant layout gives speaker + and -, though if I remember right it doesn't specify polarity, so it will be up to you to decide how you want to wire it.

[Jebull]

Okay, cool! Thanks Man!!!

Another ignorant question: what is the most reliable way to tie multiple wires together? Just twist and solder them all to the spot like normal? Twist them all to 1 single wire and run it? I don't want crappy connections for my ground or power lol

OH and do I need a plastic jack for the speaker? Or is that only relevant if the jack is in the metal box itself? I'm assuming since mine will be mounted in the wooden speaker box, I'm free to use a standard metal one?

[vigilante397]

Just twist and solder them all to the spot like normal?

That's how I usually do it.

OH and do I need a plastic jack for the speaker?

The purpose of the plastic jack is to isolate the negative terminal of the speaker from chassis ground. If the speaker jack will not be mounted to the metal chassis then you can get away with a metal speaker jack.

[Jebull]

Cool, just what I thought! Thanks!!

Haha you've been a life saver on this project

[vigilante397]

Haha you've been a life saver on this project

Glad to hear it Good luck and keep us posted!

[Jebull]

Obligatory progress pic:



It's awesome to finally be making this happen!!   

[vigilante397]

Looks great

[Jebull]

Okay. After figuring out a workaround for a pretty serious design flaw, here's what it looks like test fitting everything:

[vigilante397]

Hot damn. That looks killer! How are the guts looking?

[Jebull]

Haha sadly that would be where I have the least done, but hopefully that'll change the rest of this week or weekend!

The tiny boards look a little lonely in that huge chassis lol:

[Jebull]

Well so far I've gotten the preamp and reverb working fine, but I MAY have fried both the amp chips i had while testing out the amp circuit.. (that or I happened to get 2 duds) but I think I may just try to use the tiny giant PCB just to be safe and more stable. I ordered that and a handful of amp chips. If I still leave off the Voltage reg and preamp from the pcb, will I need to run any jumpers or just leave em off, I'm assuming my new input would be where the one leg of that lower 1u goes?

[stringsthings]

Your combo is coming along nicely!  I've built the TG on the PCB and paired it with a Jensen Mod-8 in a simple box.
It works really well.  It's my test amp on the bench and it's plenty loud.  I've thought about doing what you're doing
and pairing a TG with a preamp circuit.  I think you'll be very happy with the results of your build.

[Jebull]

 Thanks!! I'm happy with it so far! I may do something similar to that for my next one haha. I have a couple old combo amps I'm thinking of gutting and repurposing I had actually looked into those Jensen mod speakers when I first started this, they seem pretty cool! Especially for the price!

Anyway, anyone know if I'll need to do any jumpers on the Tiny Giant PCB if I leave off the Voltage regulator and preamp? I'm assuming ill still need one on the standby pads, but other than that I'm not really sure :/

[Jebull]

Okay, looks like I need some help. I got my new parts in and assembled the tiny giant PCB then attached my sunn preamp (which I tested separately first - works fine), fired it up.. and nothing. Granted I haven't had a chance to mess with it much but anyone know anything obvious I missed?

I left off all the components on the pcb for the Voltage regulator and the built in preamp / buffer. So I only have the base components for the amp chip on the board. Am I making some obvious stupid mistake? Do I need some jumpers somewhere since I left components off?

I get literally nothing. At least my first one (vero layout) got fairly warm
- still no sound but at least I know it was doing SOMETHING.

I can post pics later if I need, I'm at work now.


Man this project has slowed down, mostly thanks to a massive hailstorm totalling out both my vehicles and I've also been packing and preparing to move, but I'm slowly getting there!! Hopefully after next week when I get moved in I can knock this thing out!!