Combo amp Project - Noisy Cricket or Tiny Giant

[Jebull]

Ohh yeah that makes sense, since the preamp literally replaced the other one. That's fine by me, one less pot to worry with!

Heh that sounds almost TOO easy! Hmm. Well it is actually an amp meter replacement for old tractors. Looks like it's 30 amps if that matters. The part # is A0NN10670A. I have no idea if that's a standard number or just ours though :/

I actually ended up asking one of the guys that does that with pedals, so let's see if he has any tips.

[Jebull]

I guess I could check the meters resistance with a multimeter couldn't I?

[vigilante397]

You definitely could measure the resistance, but I would be a little worried with that particular meter as you'll be hard-pressed to find a small smplifier that puts out anywhere close to 30 amps!

So maybe it would work, but I wouldn't anticipate it moving much with guitar signal.

[Jebull]

That's exactly what I was thinking haha. 4A power supply. Oh well haha. I can look for another one maybe. Or just stick it in there anyway just for looks!

[vigilante397]

That's exactly what I was thinking haha. 4A power supply. Oh well haha. I can look for another one maybe. Or just stick it in there anyway just for looks!

If it has a backlight that can run off a 12V DC power supply it would make a cool indicator light

[Jebull]

Oooh. Yeah that would be pretty awesome!!! So. many. Ideas.

Soon I'm gonna have to start building a ton of different things just to try em all out haha

[Jebull]

OKAY.

What exactly is the difference between this:
http://tagboardeffects.blogspot.com/2016/09/sunn-model-t-1st-gen-preamp.html

and this:
http://www.guitarpcb.com/Sunn%20T.pdf

Unless of course I'm an idiot / blind and they are the same. I sadly don't understand schematics well enough yet to distinguish the differences. I just noticed that the PCB calls for several parts the vero doesn't have. Just curious, as I have no idea which would be better. I feel like the PCB would just save a good bit of time, plus it comes bundled with the switch and J201s.

[vigilante397]

I will always prefer PCB over vero, but it's a preference thing. I like that PCBs are (usually) harder to mess up as they usually have less offboard wiring. They also tend to look a bit nicer, but obviously you pay more for them.

Aesthetics aside, there are only a few differences:

The PCB uses 150K for R6 and R7, whereas the vero layout calls for 470K in those places.

The PCB uses 47K for R10, whereas the vero layout calls for 100K.

The PCB has power filtering (C13), polarity protection (D2), and a status LED (D1).

There will be a slight difference tonally, but overall they are the same circuit.

[Jebull]

AH okay! I think it was mostly the polarity protection that was throwing me so bad.

I can always sub out the values if I like the other better.

Exactly why I was asking about the PCB. I feel like it'd be better all around! Easier, safer, etc. Thanks!

[Jebull]

Now a question about a reverb.

I'm considering the Madbean Moodring.

It seems as though it utilizes a BMP tonestack. I'm curious how this will affect he overall tone of my amp. Would it impart its mid scoop to the overall tone? I'm not so sure if a tone control on a reverb works the same as a normal one. Sorry if this sounds silly.

I'm assuming if it does, and I don't want that, I could modify it using the tonestack calculator. Or use the AMZ mods.. etc etc. I've been investigating the BMP tonestack quite a bit.

(For the record I'm not asking how to mod the tonestack, I think I can figure that out on my own, just if it will impart its qualities on the overall tone)

If it DOES work like normal tone control though, would it be a problem to just leave it out completely? I don't really want TWO different tone controls on my amp.

Yes, I see the irony in leaving out the namesake control (mood). Haha


All of this aside, I'm not sure how I feel about a reverb with so many knobs anyway. 10 total controls on a little combo amp? Ugh. 

[vigilante397]

So the Moodring does indeed use a BMP tonestack, but only on the reverb itself. Your "dry" signal will not be affected by that tone control, it's just a reverb filter.

As you may be realizing, the Moodring is A LOT more than just a reverb pedal. It's a very cool effect, but if you're just looking to get reverb into your amp it wouldn't be my first pick. The most common reverb I build is the GGG D-Verb. It's a very simple build, especially on the PCB, it uses fairly common components, it only has one knob, and it behaves very much like a spring reverb unit built into an amp. Granted some people like more options than that on their reverb, but I like the amplifier approach to reverb: "do you want more reverb or less reverb? Here's your knob."

Anyway, just my 2 cents' worth.

[Jebull]

AH okay!! Exactly why I asked. I suspected it may not work like I expected!

The more I've thought about it the less I wanted to use that one. Exactly like you said, it seems awesome, but not for what I want. I'll probably still build it sometime, just as a pedal.

I was actually kinda thinking about the D-verb when I was looking at them all. I'll definitely take a look, because that sounds like exactly what I want! Thanks!!!

[PRR]

> meter replacement for old tractors. Looks like it's 30 amps if that matters. The part # is A0NN10670A.

So looks like this and fits Ford 2N (most pre-1959) tractor?



Hah! No, old tractor meters won't work around small audio. That one (that IS a universal number, actually a Ford number) is for charging 70 pounds of lead battery. Unless you have a 2,000 Watt power amp JUST for the meter, it won't twitch. A Voltmeter would be better, less current, but even a 6V meter would need fancy circuit to interface.

BTW-- don't put ohm-meters on sensitive meters, they may burn-up. THIS one you can ohmmeter all day and it won't notice. And it will read "zero". It is actually about 0.003 Ohms. You "could" determine this, with a very dead battery and a revved-up tractor, by reading the volts across the meter (about 0.1V) at high Amps of charge.

[Jebull]

Haha!! That makes perfect sense. I have no idea what I was thinking.. 
Maybe I'll just build my amp directly into an old Ford. It would be so portable! 

I've also seen some neat things about VU meters and stumbled across this:
http://www.jlmaudio.com/AT51%20DIY%20VU.pdf
via this:
https://www.jlmaudio.com/shop/vu-buffer-kit.html

Correct me if I'm wrong but, wouldn't this work fairly well and end up being (very slightly) more useful?

Not that I honestly care about usefulness.. It's entirely for looks, but it'd be neat if I could glance at it and get a 'rough' estimate of how loud I am.

I still may ditch the "gauge" idea entirely due to laziness and the fact that it would be more room for error in my novice hands. But it's still neat to learn about this if I do, or for future reference.

[Rob Strand]

Hah! No, old tractor meters won't work around small audio. That one (that IS a universal number, actually a Ford number) is for charging 70 pounds of lead battery. Unless you have a 2,000 Watt power amp JUST for the meter, it won't twitch. A Voltmeter would be better, less current, but even a 6V meter would need fancy circuit to interface.

I once disassembled a car dash assembly.  The gauges didn't use coils and magnets.  They had heating elements wrapped around bimetal strips.   I can't remember clearly but I have a feeling they didn't even have a pivot, the needle just hung off the bimetal strip cantilever.  Extraordinarily cheap.

Another odd one was from a car battery charger.  I'm a bit unclear of the details but I think it had no magnets, the meter was very light.  IIRC the charger current passed through a coil to form an electromagnet.

You see some crazy and clever designs in consumer products but they usually design for cheapness rather than goodness.

[PRR]

There is a no-lugs charge ammeter. Inside is a magnet on a spring with a needle. On back is a clip. You just run the battery wire through the clip (no breaking or stripping). The magnetic field around the wire torques the magnet and the needle moves. Fairly insensitive to exact cable location. Not built for accuracy.

Gas gauges were generally thermal. Heater and bimetal coil. 1) easy way to get lots of lag so it didn't jitter on a bumpy road  2) allowed several forms of self-compensation for varying battery voltage 3) the bimetal was an adequate and robust substitute for an actual pivot
Later gas-gauges had a regulator instead of a compensating heater. The regulator was another heater-bimetal which "blinked" so the average voltage was about 5V (and about the same even as 6V cars moved to 12V). It is possible (in 12V work) to replace a busted one with a LM7805, and there was a day when this was easier than getting the right part.

Temperature gauges, since the 5V regulator got common, and especially since a standard Thermistor was mass produced for automotive uses, were again thermal. Way-cold is over 100K, boiling is like 1K. It is not linear, which is why you only get C and H marks, and wonder what the in between means.

Voltmeters actually could be thermal (which would not be easy interface to small audio). None of my rides ever had a voltmeter (unless I hacked one in). If not thermal, likely a hunky 10mA movement with nails for pivots, not a 50uA job which breaks on a hard knock.

[Rob Strand]

There is a no-lugs charge ammeter. Inside is a magnet on a spring with a needle.

That's pretty cool.  Kind of a budget clamp meter. 

1) easy way to get lots of lag so it didn't jitter on a bumpy road  2) allowed several forms of self-compensation for varying battery voltage 3) the bimetal was an adequate and robust substitute for an actual pivot

Yes, I realized at the time it was a tough design and immune to much of abuses present in cars.  Didn't realize it had that compensation scheme. 

Thermistor was mass produced for automotive uses, were again thermal. Way-cold is over 100K, boiling is like 1K. It is not linear, which is why you only get C and H marks, and wonder what the in between means.

I've got a thermistor here from the 70's that tracks my PT100 RTD to say 0.2C (maybe better).  I didn't calibrate it. It was supplied with a resistance to temperature lookup which I fitted a curve to in a spreadsheet.   So the non-linearity can be undone via a scale.  Another one I did by measurement was only good to +/- 1.0C; that one seems to have repeatabilty issues.

Voltmeters actually could be thermal (which would not be easy interface to small audio). None of my rides ever had a voltmeter (unless I hacked one in). If not thermal, likely a hunky 10mA movement with nails for pivots, not a 50uA job which breaks on a hard knock.

It's so long since I've pulled one apart I can't remember.  The volt meters are usually those "compressed scale" [Edit "expanded scale"] types which might work with a bimetal strip.  The needle ones are likely to have internal zeners which are going to cause havoc for other uses  (well unless you open the meter and rip that stuff out.)

All the tacho's I've pulled apart were moving coil needle types.   (taco's on the other hand are more thermal.)

[SpencerPedals]

I picked up a Guitar PCB PCB of the Model T preamp recently and have been tweaking some 9V amp circuits; the same idea crossed my mind, to splice the Model T front to a LM-386 (or TDA 7052A) amp.  It was cool to stumble upon this thread.  I've build a Noisy Cricket before and it's great, but the "grit" switch is a bit anemic.  It's gritty, but not in a really great or musical way.  I think a Model T spliced to the front to go full-bore, or a Trotsky/Electra on a switch for moderate grit, would be much better suited.  Obviously this costs battery life, but a second 9V for the optional feature is the best bet, IMO.

[Jebull]

Hah, I just ordered one as well! As you can see I decided to go with the Tiny Giant, but I'm also still going to make a Noisy Cricket. I'll probably get enough parts to make a couple of each (stand alone, not combo amps haha) just to mess around with and try out different tone stacks and preamps and such! I'm glad you found this thread!  Hope you might find some of my questions helpful to you too.

[Jebull]

So. How well will my TG with 12v power supply work with a 16ohm Eminence Swamp Thang?

I've been reading about ohms/power/etc and it's making my head hurt and made me more confused than when I started. lol.

I understand this will lower the wattage, and therefore volume, which is no problem at all. Actually it is preferred. I don't want my neighbors beating down my door with pitchforks! Plus I would prefer the 16 ohm in case I ever decide to wire it up with other speakers.. etc.

Is this feasible? Or will it just sound like poop? I would still like a decent full sound. I can always go with the 8ohm version.