Input caps are required for most single rail amplifiers.
Therefore, don't short/bypass/circumvent the input caps.
Thanks daniel and Destroyer.
There is no output up to about half of volume rotation then all hell breaks loose.
Sounds like full volume at half of volume rotation.
Same on both amps and original and stepped volume controls.
Does sound good but to loud to leave for longer than a few seconds.
Thanks Richard
There is no output up to about half of volume rotation then all hell breaks loose.
Sounds like full volume at half of volume rotation.
Same on both amps and original and stepped volume controls.
Does sound good but to loud to leave for longer than a few seconds.
Thanks Richard
With so many of these available from so many ebay sellers, it's really hard to choose which one to try. Some of them are literally under $3USD.
Is there any consensus on which ones are the best value?
Is there any consensus on which ones are the best value?
If built correctly, then, in that case, the only noisegate/squelch features included inside the chip are the mute and standby functions.
Looking at the datasheet: TDA7297 Datasheet pdf - 15+15W DUAL BRIDGE AMPLIFIER - SGS Thomson Microelectronics
So, the mute circuit works within a range of 4v~9v, but the "preferred" range is 6v~8.25v.
Therefore, check your mute pin, measure between mute and ground to see if the voltage is in the range of 6v~8.25v.
Figure 3, stand-alone low cost application has a 47k/47k divider across the rails with the voltage rise slightly slowed by 10u from midpoint to groundside. This divider has half the rail voltage at midpoint, which connects to both mute and standby pin. If voltage is incorrect, it may be useful to change the groundside resistor to something lighter, such as 100k (or that may go wrong if the amp is reliant on that divider for reference voltage). I wouldn't tamper with that on a well working amp, but if it didn't un-mute right, I think I'd tamper with that divider a bit.
or
A build error that may be near invisible is a cold solder joint; so, it may be useful to paint all of the solder joints with gel flux (Rosin flux + petroleum jelly = gel flux) and then re-heat all of the connections so that they're as clean and shiny as a chrome Buick bumper. The gel flux can be cleaned off with alcohol, somewhat.
Hellllloooooooo ooooo, start with the Classic of course ... [with 3 cools how can you go wrong?!?11?1!!]
😉
OP=
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Well, maybe signal isn't getting through until voltage from it is high enough to cross a gap from, like Daniel says, some cold solder joints.
Also consider adding a tiny touch of solder to chip pins and reheating them if they look poor.
Pics may help us figure it out for you.
Also consider adding a tiny touch of solder to chip pins and reheating them if they look poor.
Pics may help us figure it out for you.
Perfect, one to mod and one to keep stock ... at least for now.
Let the w a i t begin ...
Ah well. It wouldn't be as much fun otherwise. I've got a junk box full of old components. Must be a dozen or so pots in there. Good ones. 😀
Well, I need some help!
I narrowed down the optimal decoupling capacitance to pairs of caps, per each power pin, in the range of 560u~680u, and Panasonic makes a lot of those. Does anyone know which 560u or 680u caps are excellent performers for small signal coupling and/or power decoupling duties?
I'll probably order both values to try them. What I really need to know is favorable models of caps for this, preferably available at digikey. Halp?
I narrowed down the optimal decoupling capacitance to pairs of caps, per each power pin, in the range of 560u~680u, and Panasonic makes a lot of those. Does anyone know which 560u or 680u caps are excellent performers for small signal coupling and/or power decoupling duties?
I'll probably order both values to try them. What I really need to know is favorable models of caps for this, preferably available at digikey. Halp?
Once, there were special audio grade caps out there but this now proves to be an outdated sales strategy for fairly standard grade caps. There are a few boutique parts manufacturers who specialize in expensive, low volume manufacturing techniques and charge accordingly for their audiophile products but when the caps begin to total 90%+ of the build cost for chip amp projects, you might wonder 'what the heck' you are doing.
Low ESR type caps are heavily favoured by DIYs for decoupling and coupling in audio amps but most of the grades we see on offer are more for dimensional, service life, sealing, terminations, electrolyte features and a fine-tuned bulk pricing to get a sales edge as much as a performance one.
Some are also tweaked for specific power supply duties that don't apply to audio use but that doesn't mean most them won't work to some advantage over "standard" capacitor grades in audio applications. I find little audio difference between today's low ESR types, which wasn't true around 10-20 years ago.
For Panasonic types, that usually means FM or FC grades but if you want the lowest in low ESR, the new FR grade is the type to try. I say "try" because I haven't used them yet and I can't see the need but there are always guys who must have the most extreme examples of everything in their projects . Perhaps this would be an interesting way to find out if it's actually worth it.
I prefer Nichicon KZ or FG to Panasonic FC or FM.
But I'm running OSCON's, Panasonic SEPF. They only go up to 330uf (I've got a bunch of them). However I have a capacitor multiplier feeding them. The reduction of AC across them may be highly valuable to the sound. Either way, it's a very high degree better than just capacitors (of which no less than 10kuf or so is advisable for loud volume or speakers that aren't very efficient).
Sure. 97dB efficiency. Impedance is pretty high, though. Not sure if that will cause any issues. Probably not.
I read that 15ohm drivers are easier to drive than 8.. maybe Trileru will give/sell me a tda7297 as we are from the same city.🙂
Although more money, this is a surprisingly good sounding amp for what it cost. I recently hooked it up along with a sub-woofer in my shop with a couple of baby Advents and it sounds great. They're also offered with Bluetooth now.
-Rick
