In reply to Keith Tanner :
Oh, ok. Need to get some LED's that look like tubes from the outside?
But lets pretend you did learn- how would you have set it up using a modern tube amp? What mistake did you make?
In reply to Keith Tanner :
Oh, ok. Need to get some LED's that look like tubes from the outside?
But lets pretend you did learn- how would you have set it up using a modern tube amp? What mistake did you make?
I learned all sorts of stuff about embedded computing because the amp failure got me to take a second look. I don't regret that at all. The only thing I learned about tube amps is that you can't always just pull a tube and run a single channel on a stereo amp :) The tube thing was a dumb idea, it was mostly a result of "this used to be a tube radio and that little amp is cheap so let's make a nod to its past". You can't see the tubes at all when it's operating. It was pointless.
A great example of adding a feature because you can even though it has no value-add, and it almost ends up killing the whole project. There's a lot to learn right there!
But if I decided it really needed to be a tube amp, I'd either run it in stereo with two speakers or I'd specify a mono amp.
I found a amp kit on Amazon. Lets assume its not complete trash. It has volume, base and treble Knobs.
They are grouped way to close. Can i unsolder them from the board, and solder in extension leads to put the knobs where I want? Same question for the AUX input. Aside from the gauge, what wire would be appropriate?
Keith, you said you once used cheap car speakers. Anything I should pay attention to so everything plays nice?
You can certainly unsolder the pots and inputs on the board. That can be a bit of a PITA but I did do that on my short-lived tube amp attempt. They don't carry a lot of power, especially the knobs. Think of how thin a typical 1/8" patch cord is for the aux. Quality of signal is more important, so you'll want to make sure you don't accidentally turn them into antennae.
You could also look for a "soldering kit", which is basically a pile of electronic components and a circuit board you populate. More work to build but some people (hi!) really enjoy it. Then you just don't solder in the pots and aux input jack.
About all you have to watch for with the speaker is matching the impedance - that one you found suits 4-8 ohm, which is pretty much anything these days. I had no way to judge what was good and bad at Best Buy so I went with the "it can't be worse than this crazy field coil speaker from the 30's with really high input levels" thought process and bought something cheap that's the right size.
I'd go with the Sparkfun unit over the Amazon one, mostly because I trust the Sparkfun guys more than random Amazon sellers and it's half the price, but it doesn't have the tone controls. Check the Amazon reviews about that, though...
Appleseed said:Keith, you said you once used cheap car speakers. Anything I should pay attention to so everything plays nice?
I agree with Keith. Cheap car speakers are a good way of doing it. Pyle, Dayton, Skar... as long as you're not looking for wonderful sound, you basically need any good speaker.
Pay attention to resistance in Ohms. Amplifiers (like any other conductor) are built to take a certain amperage. Lower-ohm speakers increases that amperage in the amplifier. One of the specs on the amp should be "stable to X ohms" or "X-ohm stable." As long as you give it enough resistance to prevent frying the amplifier you should be good. The one you pictured above is a 2-channel, so it's pretty simple. If it says 4 ohm stable, that means choose speakers that are at least 4 ohms each or better. Most car speakers are 6-8 ohm so you should be good.
You could go much higher, like some old-school home theater drivers are 16 ohms, but you quickly reach a point of diminishing return. The rated wattage of the amplifier is rated at certain parameters. If you drop the speaker resistance and increase the amperage through the amp, you increase the amp's wattage. If you go with too much resistance in the drivers, you're "choking" the amperage and therefore the wattage. It's usually not really noticeable to the ear. A higher resistance driver typically does more with the signal it gets than a lower resistance driver, so the difference (in your application) is mostly mathematical.
You can also get creative. Let's say that amp is good down to 8 ohm loads, but you find four speakers that are 4 ohms. Just put two speakers wired in series on each channel. Opposite can be done with four 16 ohm speakers; wire two in parallel on each channel.
Keith Tanner said:You could also look for a "soldering kit", which is basically a pile of electronic components and a circuit board you populate. More work to build but some people (hi!) really enjoy it. Then you just don't solder in the pots and aux input jack.
A few years ago I bought some C-note speakers from parts express and made my own crossovers. I'm totally hooked on the DIY audio thing now. It's almost as addictive as autocrossing.
For clarification, a lot of newer car speakers are 3 or 2 ohm, since a lot of newer car factory systems use odd impedances to get more volume out of lower power amps. Most are still 4 ohm. Most home bookshelf and tower speakers are 8 ohm.
From reading many reviews of the various amp boards, many use the same amplifier chip ( TPA 3116), and produce the best power when fed with the upper end of their stated voltage range, 20 to 24V.
The downside to buying an all in one bluetooth amp board is you are stuck with whatever setup the provider slapped together, and that affects everything from ease of bluetooth pairing, to all the inbuilt notifications. Might suck to have a board that sounds great while playing, but you have no control over the volume of how loudly it announces "bluetooth paired".
These amp boards are just the same as any amplifier, they generate heat. The more current you put through it, the hotter it's going to get. In the capacious insides of an old RCA Victor speaker cabinet, there should be plenty of room to radiate said heat. A lot of people are looking to build loud and small, and there you will find yourself bumping up against the thermal ceiling of a tiny enclosure quickly.
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