[devinkato]

Battery power is a no brainer when properly done.

My ears pricked up - can you provide a bit more detail about your thoughts re: battery power and applying it here?  I'm researching different power strategies for these little guys and would love to hear any input you have.

Thanks!

[dBe]

My ears pricked up - can you provide a bit more detail about your thoughts re: battery power and applying it here?  I'm researching different power strategies for these little guys and would love to hear any input you have.

Thanks!

Batteries are easy... or hard, depending on your POV.

Batteries are weird animals.  Oddly enough there are good and bad sounding batteries.  It has to do with the purity of the plates and their internal connections.

Never use a battery (lead type) that is not an AGM.    As far as I am concerend the care and feeding of lithium derivatives are just too much of a PITA to use.  They sound good, but are like that cute sister-in-law that is a _itch (pick your letter).

I use and recommend Power Sonic batteries.  They are consistent and they SOUND GOOD.  I use and recommend Ctek chargers.  I have 3 different versions.  The 3300 will be just fine for this application, if you turn it off when listening.  The 7002 is pretty much silent when used with a big battery.  I have a 26AH, 55AH and a 100AH.  The 100 has the best sonics, but is very pricey.  Thanks to Trung for hooking me up a few years ago.  That ship has sailed, but I got on JIT    I recommend the 55 for most applications.

Batteries have high output impedances.  In my BatteryBUSS there is 34,000+ufd of very low impedance capacitors to reduce that impedance.  Other things, too, but I will not divuldge that info.  I am a capitalist after all. Mouths to feed and all of that.

DO NOT use one of those 1 farad car audio caps.  Again: the output impedance is too high.  They may be fine to use in conjunction with smaller, very low impedance caps as mentioned here in this thread.

Once you hear battery audio you will never go back.  That is why my preamp and power amp are DODD Audio designs.  Gary believes, as I do, that the simplest circuit topology, properly implemented sounds the best.  My DAC is DC powered.  My Mac Mini is DC powered.  The only AC powered components in my system are the GR Research subs that startle every one that hears them.

To me, the secret to audio (if there is one) is low noise, VERY high current power supplies with extremely low output impedance.  I have taken crappy gear and made it sing with power supply mods.  The power supplies in gear are the most expensive parts.  Bean counters cut the $$$ there, first.

Remember: voltage is horsepower and current is torque.

The thoughts of a totally unbiased (Bwaha!) audiophool.

PM me if you want more info.

Dave 

[Folsom]

Dave, have you played with LiFePO4? They're a safe alternative to LiPO (fire bombs).

I'm going to agree with you, it's all in the power! But as far as impedance, well it's all a matter of perspective not only between us, but the gear too. DC is great for having relatively no noise going into a system, but not very good for getting it out.

[S Clark]

My pictures show he little yellow cap because I thought it was an bypass to ground from a different point within the chip. You can do that easily on a 3875 and other chip amps, but on this one it's just bypass cap that causes ringing (you'll hear it not ringing when you pull it, no joke, ...

ARGGGHH!!! I pulled those by mistake when taking out the rectifier, and then put them back!!! If you don't like the Chinese boards, who do you recommend? Don't just tell Danny in a PM, we all want to know!
And you're right about imaging.  If the stereo can get better then it's going to top my Moscode 401HR with just under a thousand $ worth of mods... Hard to believe I just typed that.

[Folsom]

  Sorry.

I happened to realize that after, and amended my build guide, but without pictures during process.

The boards are not ideal, but I'll point out the big problem, there aren't any other ones!

I DO NOT like 3875 chips by comparison. They're ok, but not a show stopper. I'm just saying it's easier to unload some RF with them.

The question now is, would people like boards/kits instead? The price changes significantly, if you can imagine it. But kit's will have more closely matched capacitors, etc.

You can do what Danny was talking about pretty easily. Get an extra board, and only install one channel input capacitor. Then connect right and left channel after the capacitor. Then also do the same thing with the speaker outs. Then report back for the rest of us that haven't actually done it! Could also try just running one channel on each board.

*Don't connect one channel to both input caps, only connect channels post capacitors.

[dBe]

Dave, have you played with LiFePO4? They're a safe alternative to LiPO (fire bombs).

I'm going to agree with you, it's all in the power! But as far as impedance, well it's all a matter of perspective not only between us, but the gear too. DC is great for having relatively no noise going into a system, but not very good for getting it out.

Yep, I have played with every battery known and some that are not available to general consumption.  Cool living where I live, knowing the people that I know.

Anyway,  The AGM battery is the best compromise for most people IMO.  They are cheap, have NO isue when they are properly implemented and sound great.  One of the things that EVERY battery needs is a stout capacitive buffer.  Even the LiFePo4 batteries.  If there is not a buffer, the sound of the battery is prevalent.  Of course, some people may prefer the SOUND of things, but that is purely a YMMV situation.  Me, I like a 64 year old grey headed woman that I have 47 years invested in.  Know what I mean?

Anyway, all of this is great fun and I may have an entirely different take when I get the amps I ordered today.  After all, the proof is in the pudding.

Dave

[Danny Richie]

I'm not even going to use the coupling caps with mine. I have output coupling caps on my pre-amp that should do the job.

[SamA]

I liked it and said I didn't think I'd mod it, but I did. Finished the E-A-S-Y mods as indicated and now have 20 or so hours on it. Will wait a bit more before rendering an opinion. BUT ... it does sound nice.

Curious, though. The mods, as suggested, are essentially better quality replacement components, right? Or, is there something else going on with the recommended replacements?

Any insight would be appreciated.

SamA

[Folsom]

I liked it and said I didn't think I'd mod it, but I did. Finished the E-A-S-Y mods as indicated and now have 20 or so hours on it. Will wait a bit more before rendering an opinion. BUT ... it does sound nice.

Curious, though. The mods, as suggested, are essentially better quality replacement components, right? Or, is there something else going on with the recommended replacements?

Any insight would be appreciated.

SamA

There isn't anything to change really. Most of everything is built into the chip, and basically every part I recommended replacing it has to have under almost every circumstance. The ones I recommended pulling can all be pulled.

Inside the chip there's a bunch of stuff, all of which you'd have in a regular discrete amplifier, but it's TINY.

If you want somewhere to do some changes, I'd recommend the power supply. You can do all sorts of things, switchers, linear, regulators, filtration, etc. You can even get two of them, or four of them if you run two boards with inputs and outputs paralleled. You'd have to cut some traces in order to separate the power, and attach a wire in a VERY careful manner, but there's options.

[mboxler]

One of the things I like about the TDA7297 amp is how it combines The Lab, The Starting Block, and The Cheap & Cheerful HiFi
circles into one place.

For $6, you can buy one and leave it alone....or
 
You follow the traces to and from the IC...learn how to use a multi-meter.

You buy a soldering iron and a better capacitor, replace the stock one, and smile ear to ear when it still works!

You learn about AC, DC, coupling caps, resistors, diodes, LED's.

Batteries vs Power Supplies.

"I wonder What does this part does?"

Google some more.  Volume controls, RCA's, binding posts.

Call over your husband or wife..."listen to this!".  "Nice dear"...eyes rolling.

Ask questions, make mistakes, correct mistakes.  Next thing you know, you are helping someone else
with things you yourself knew nothing about before you started.

You can even buy these unassembled (5 for $22).  Again, a rewarding experience.

I hope others are learning as much as I have.

Mike 

[wushuliu]

There isn't anything to change really. Most of everything is built into the chip, and basically every part I recommended replacing it has to have under almost every circumstance. The ones I recommended pulling can all be pulled.

Inside the chip there's a bunch of stuff, all of which you'd have in a regular discrete amplifier, but it's TINY.

If you want somewhere to do some changes, I'd recommend the power supply. You can do all sorts of things, switchers, linear, regulators, filtration, etc. You can even get two of them, or four of them if you run two boards with inputs and outputs paralleled. You'd have to cut some traces in order to separate the power, and attach a wire in a VERY careful manner, but there's options.

Are you still a believer in using several diodes at the dc to clean up noise?

[Folsom]

No, one can reduce ripple. More has too much leakage, ultimately hurting the output. I probably jumped the gun a bit too much. 

[Danny Richie]

I posted some pics and info on my amp build in my circle: http://www.audiocircle.com/index.php?topic=124981.msg1317309#msg1317309

[rhing]

Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.

[Danny Richie]

Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.

I'll have to try them with a full range speaker to see. I have been using them on some Super-7's with in-line filters to roll off the lower ranges.

[Folsom]

Very nice builds Danny. Being a professional speaker designer/builder, have you found the TDA7297 to roll off the bass? In my experience, the bass is nice down to 50-60Hz, but no deeper. I'm not a really big bass hound, but I find this one area to be a shortcoming. It was enough to drive me toward the TI TPA3110D2 and TPA3116D2 Class D amps, which go lower.

Ya but you use the wrong sized capacitors to reach lower anyway. .22uf isn't big enough to reach 20hz even if the amp is capable. You can calculate the corner frequency, and basically at .47uf or larger you're able to hit 20hz. .47uf is a common size anyhow.

[rhing]

Ya but you use the wrong sized capacitors to reach lower anyway. .22uf isn't big enough to reach 20hz even if the amp is capable. You can calculate the corner frequency, and basically at .47uf or larger you're able to hit 20hz. .47uf is a common size anyhow.

If you look at the STM TDA7297 datasheet, the frequency response graph shows a roll-off above 20Hz. This has nothing to do with capacitors outside of the amplifier IC.

[Folsom]

Data sheet is -3db at 20hz for the chip. The roll off for a given build with improperly sized capacitors for hifi instead of TV or portable boxes is of no real concern to me.

It's physics, .22uf is incorrect for low bass. It's not an arguement, it's simple math to describe a physical relationship.

[elb]

I recently bought a TPA3116 (YJ blue board)

Applied all the the tricks(Wurth coils,silmic caps etc.)

My personal opinion,The Sallis modded TDA7297 kills it.YMMV

Best regards.

[wushuliu]

I recently bought a TPA3116 (YJ blue board)

Applied all the the tricks(Wurth coils,silmic caps etc.)

My personal opinion,The Sallis modded TDA7297 kills it.YMMV

Best regards.

Your review aside, I'm surprised that the TDA7297 doesn't blow the TPA away in general given how few parts it uses. Unfortunately it looks only suitable for 8 ohms so it would not be suitable for my speakers to test.