chip amps: Almost everything you ever wanted to know

[mboxler]

Hi

I ordered a pair of these TDA7297 amps, just for fun. I also have a TA2020 amp that I run from a 18AH 12 volt battery. I did notice an increase in bass response over the SMPS. I'll use the battery on the TDA7297 amps when they arrive.

Do the TDA7297 amps have on/off thumps?

I'll probably try these on my bi-amped Khorns, replacing the SET amps.

Thanks, Mike

[rhing]

Hi

I ordered a pair of these TDA7297 amps, just for fun. I also have a TA2020 amp that I run from a 18AH 12 volt battery. I did notice an increase in bass response over the SMPS. I'll use the battery on the TDA7297 amps when they arrive.

Do the TDA7297 amps have on/off thumps?

I'll probably try these on my bi-amped Khorns, replacing the SET amps.

Thanks, Mike

Hi Mike,

The battery should work fine. Here's a simple calculation you can use for the battery charge life:

Power [watt] = Voltage [Volt] x Current [Amp], or

P = V x I

=> Current [Amp] = Power [watt] / Voltage [Volt],

=> Current [Amp] = 15W / 12V = 1.25A

and

=> Time[h] = Capacity[Ah] / Current[Amp]

=> Time[h] = 18Ah / 1.25A = 18h

This is an approximation at best assuming no losses occur and that the amp is driven at 15W, which we know is not the case.

As for the turn-on/turn-off thump, I haven't put a power switch in place between the amp and SMPS. When I plug in the amp, there is no thump. When I unplug the amp, I hear a small thump, but nothing that is objectionably loud or cause for damage. I actually leave the amp on for several days, and I haven't had any problems yet.

Please share your listening impressions.

[DizRotus]

Hi

I ordered a pair of these TDA7297 amps, just for fun. I also have a TA2020 amp that I run from a 18AH 12 volt battery. I did notice an increase in bass response over the SMPS. I'll use the battery on the TDA7297 amps when they arrive.

Do the TDA7297 amps have on/off thumps?

I'll probably try these on my bi-amped Khorns, replacing the SET amps.

Thanks, Mike

When the TDA7297 is powered by the battery booster, it can be switched on/off from the booster. There is a very slight thump that is barely noticeable. The SMSL SA-50 and SA-S1, as well as the Lepai TA2020, all have far more noticeable thumps.

Edited November 19, 2013 by DizRotus

[billybob]

Will be picking up a used Lepai LP TA2020a along with PS tomorrow for $15.

After contacted seller went to Amazon to look. Guess I could have gotten it new for a little more but hay, I still like a bargain.

Just want to see what the doo da deal is with these...

[rhing]

While I was out of town on business this past week, my 50k, log tapered SMD resistor-type stepped attenuator came in from auction seller tube_buyer. I had an L-bracket in my stash from a volume control extension kit that I used to mount the stepped attenuator. I directly wired the RCA input jacks, the two Mundorf input capacitors and the ground connections to the stepped attenuator. The other ends of the Mundorf caps were connected to the amp PCB where the old caps were mounted. So now this amp is 50% point-to-point wired.

The sound is clearer with the stepped attenuator and balanced from silence to high volumes. It actually plays slightly louder since most of the signal path uses high quality wire instead of thin Copper traces on a PCB. I am very pleased with this amp driving my Klipsch Forte IIs. It doesn't have the full bloom and tonality of my Audio Research LS7 line stage and Dynakit Stereo 35 tube amp combination, but it does present big sound with a wide and deep soundstage, and at a significantly lower cost. At this point, I am going to install this amplifier in a permanent, compact Aluminum enclosure available from auction seller, fan_computer, for $18. Adding up the costs of all the parts I've pieced together including the enclosure, my total comes to $130. For a low power integrated amplifier, this amp can run with some serious gear and free up cash to buy great-sounding, efficient speakers like Klipsch Heritage speakers.

Now to add more to the chip amp fun, I've been egged on by diyAudio.com forum members to explore Texas Instruments' TPA3116D2 Class D amp.

http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp.html

A Chinese manufacturer, Yuan Jing, makes an amp module using this Class D chip. This is a higher power amplifier (50W) that even tube amp builders are falling for. This newer Class D amp is supposed to easily eclipse the older Tripath amps. The saga continues ...

[DizRotus]

I ordered 4 of the Wima coupling caps from Mouser and 4 of the Panasonic ECQP caps from Jim McShane. That should give me plenty of ammunition to hot-rod the TDA7297s for now.

I'm still curious about whether the 12.65 volt/high amp battery booster is an inherently superior power supply for the TDA7297, as compared to power supplies with >12volts at >2 amps. I've got several to try, but I don't expect an improvement over the 12.65 volt battery. As an experiment, I'm, going to let the booster's voltage drop below 12 volts (I'll monitor it with a DVM) to see if I can perceive any degradation in performance.

I'd like to know if you can hear the difference between the Wima and Panasonic caps with this amp. The Panasonics are no longer manufactured, so if the Wima's work fine, that would be great for others who want to try the amp.

According to a description of your car starter battery unit, it is capable of providing "900 peak amps and 225 cranking amps of jump starting power." Is the amp chip smoking or getting warm when you have it connected to the amp? I am curious what sound quality differences you hear when you use this battery.

That could very well be a very good power supply for this amp, especially for those of us who are on a dirty utility grid. I'm not sure what speakers you use in your home, but please share what kind of bass response you get from the TDA7297 amp, especially when you are possibly feeding 225-900A through the amp.

Rich,

I overlooked your questions about my use of a Car Start CS1000. The amp doesn't smoke or get warm when powered by the CS1000. The amp is currently driving four DIY single driver BR enclosures similar to discontinued Tekton 3.1 (see: https://community.klipsch.com/index.php?/topic/56494-single-driver-experiments/) used with a Dynaco QD-1, thank's to Dave Mallette's thread. (see https://community.klipsch.com/index.php?/topic/145727-quadapter-back-yay/). Due to attachment limitations in the new forum, attachments have been deleted from older threads. A photo of one of the speakers is attached.

As expected, the bass is not prodigious from these small BR enclosures. Nonetheless, the quality of the available bass is clearly improved with the CS1000 over several 12v bricks from 2A - 6A. I plan to try these with some DIY KEF B139 transmission line subs I use to augment LS3/5as for the TV, just out of curiosity, not as a serious permanent solution.

Until my newly purchased (and much traveled) phono preamp finally arrives from billybob, my only source for the chip amps is Pandora or mp3s via Bluetooth. Serious experimentation and comparisons will be made after a turntable can be added to the mix.

It's probably buried deeper in this thread, but I'd appreciate more info regarding the source of the stepped attenuator you're using.

This TDA7297 is starting to be "Stone Soup."

Edited November 24, 2013 by DizRotus

[mboxler]

Rhing...

How go you remove enough solder to remove the jacks that come with the board? I've tried a wick, but couldn't get enough off to free the jacks.

Mike

[rhing]

Rhing...

How go you remove enough solder to remove the jacks that come with the board? I've tried a wick, but couldn't get enough off to free the jacks.

Mike

Hi Mike,

I use a solder sucker tool from Radio Shack. It looks like a large syringe that has a spring loaded device to instantly suck solder once it reflows. A couple of hits on each contact, and the volume pot and 1/8" mini-stereo jack both fell off the board easily. For working on printed circuit boards from China, I've found they typically use a cheap solder that does not flow well, so using a wick is almost impossible to use to clean up solder. On top of that, the traces and eyelets on the boards aren't very sturdy and have a tendency to peel off the board after prolonged heating from solder iron contact.

Rich,

I overlooked your questions about my use of a Car Start CS1000. The amp doesn't smoke or get warm when powered by the CS1000. The amp is currently driving four DIY single driver BR enclosures similar to discontinued Tekton 3.1 (see: https://community.klipsch.com/index.php?/topic/56494-single-driver-experiments/) used with a Dynaco QD-1, thank's to Dave Mallette's thread. (see https://community.klipsch.com/index.php?/topic/145727-quadapter-back-yay/). Due to attachment limitations in the new forum, attachments have been deleted from older threads. A photo of one of the speakers is attached.

As expected, the bass is not prodigious from these small BR enclosures. Nonetheless, the quality of the available bass is clearly improved with the CS1000 over several 12v bricks from 2A - 6A. I plan to try these with some DIY KEF B139 transmission line subs I use to augment LS3/5as for the TV, just out of curiosity, not as a serious permanent solution.

Until my newly purchased (and much traveled) phono preamp finally arrives from billybob, my only source for the chip amps is Pandora or mp3s via Bluetooth. Serious experimentation and comparisons will be made after a turntable can be added to the mix.

It's probably buried deeper in this thread, but I'd appreciate more info regarding the source of the stepped attenuator you're using.

This TDA7297 is starting to be "Stone Soup."

If you search for "smt stepped attenuator" or "stepped attenuator" on eBay, you'll find a bunch of stepped attenuators from sellers "lasercollection" and "tube_buyer." These are identical products, and lasercollection's description is very thorough on explaining the value and design of the product. I would recommend the 50k SMT stepped attenuator with the logarithmic taper for this amp. You could go to a 25k stepped attenuator, but you'd probably have to use higher capacitance input coupling caps (i.e., 0.47uF) to maintain the same tonality. If you want to reduce output (i.e., too loud), you can use a 100k stepped attenuator.

[Marvel]

I've added solder back onto those crummy solder jobs, and then the solder comes back up a bit easier.

I used to use a motorized vacuum pump at one of my previous jobs. It had a soldering iron tip that was hollow, connected to the vacuum line. Place it over the lead on the board and hit a button and it was very clean.

Bruce

[billybob]

Got the Lepai LP TA 2020a+ now already burned in some. It is 2013 version being a plus. Plus could mean PS included...lol. Seller replacing it with this interesting(maybe) Lepai:

http://www.amazon.com/Lepai-LP-168HA-40-Watt-Amplifier-Output/dp/B0070Z87YO

He is powering some small bose and a Bose Acoustimass subwoofer. Dropping off a set of nice condition Technics, albeit inefficient 3 ways taking up space here. He will let me know his impressions later. Will have to wait until Monday or so to listen to my Lepai.

[rhing]

billybob,

Be prepared to do some modding to get that amp sounding its best. There are numerous forum threads about modifying them. Once modded, these amps can sound really good.

Rich

[onlysleeping]

I hooked up my TDA7297 using the Dayton DTA-1 power supply. I hooked the amp up to my Khorns and my ipod. It sounded pretty good, more full sounding than the DTA-1.

I then hooked up my preamp, which is a McIntosh MX1113. Ipod to Pre, pre to TDA 7297 to Khorns. Whoa! Bass city! Sounded fantastic. I can't wait to hook up my SACD player and my turntable.

Question for everyone - how and what are you using to mount the TDA7297? I was thinking of finding a small wood box of some kind. I'm not sure how to orient the amp,. Also, the speaker connection is quite small . I bought some wire and I'm thinking of hooking it to banana plug inputs.

[billybob]

Following a previous pic, I will gut a receiver to use the body and the rca outputs. Clearance should not be a problem as amp circuit board is small and should mostly clear the metal or other (plastic is a good nonconductor) material bottom of the repurposed unit, although the end is the same only, this amazing(?) D class amp. Suppose could reuse the volume or other controls. The thinking in some one's thinking here is that in the minimalist cree that less being more., sometime. Will need to get a solder sucker at the least myself. I sometime have burned myself. Not up though.

[DizRotus]

The second TDA amp arrived, so it's time to plug in the soldering iron and get to modifying. Actually, I'll burn in the new one for some time and then compare the stock amps to each other before modifying one of them.

[DizRotus]

My second TDA7297 arrived today, just 9 days after I bought it off eBay. It's playing as I type.

My immediate reaction is that it sounds great, but with a bit more high frequency emphasis than the 1st one. I can't decide if I like it better than #1, but it does seem to be different.

It's not shrill or strident as the Lepai TA2020 seemed to be right out of the box, but the highs seem stronger than #1.

I'll let it burn in before I do any modifications to either. I continue to be amazed by the sound of these stock TDA7297 amps. Perhaps these geriatric ears are no longer a good judge, but they sound fantastic to me. I cannot recommend too strongly to buy a pair of these if you have any curiosity and are at all DIY inclined. For $11.96, you can't go wrong. Thank you Rich, aka rhing, for recommending this amp.

Eventually I'll decide which sounds better and then perform surgery on the other to see if I can make it sound better than the control amp.

The aborted quote immediately below is answered in post #164 below.

Edited May 14, 2016 by DizRotus

[DizRotus]

I hooked up my TDA7297 using the Dayton DTA-1 power supply. I hooked the amp up to my Khorns and my ipod. It sounded pretty good, more full sounding than the DTA-1.

I then hooked up my preamp, which is a McIntosh MX1113. Ipod to Pre, pre to TDA 7297 to Khorns. Whoa! Bass city! Sounded fantastic. I can't wait to hook up my SACD player and my turntable.

Question for everyone - how and what are you using to mount the TDA7297? I was thinking of finding a small wood box of some kind. I'm not sure how to orient the amp,. Also, the speaker connection is quite small . I bought some wire and I'm thinking of hooking it to banana plug inputs.

Rich, aka rhing, posted several pics of his amp at #1058, #113, #130 & #153.

I posted a pic at #139. As you can see, we both used small gauge wire from the amps' tiny outputs to beefier terminals, Rich to binding post and me to a barrier strip. You definitely don't want to be disturbing those tiny screw terminals on a regular basis.

I plan to implant one inside the "iPod" dock on steroids (see posts #14, #15, & #131). I'd reattach the original attachments, but I don't want to squander the parsimonious attachment allotment under the new regime (only kidding Chad . . . . sort of). Prior to putting it inside the dock, I'll bypass the volume pot. The volume will always be controlled by the Bluetooth device feeding the music.

As to the other, I'll probably just keep it out in the open to amaze my audio challenged friends and family. How can anyone appreciate it's tiny size and big performance if they can't see it. Also, it's all the easier to tinker with that way.

Edited November 26, 2013 by DizRotus

[rhing]

Glad to hear that people are happy with their TDA7297 amps. I had also purchased a second TDA7297 amp module to keep in stock form for a little while. I will need to draw on my memory to determine if there is any variation in the units. Keep in mind that the manufacturer, whoever it may be in China, is using cheap solder and the volume pots aren't the greatest quality either, so it would almost be surprising if the amps are consistent from unit-to-unit. I'll end up upgrading the second unit with better parts, but keep the costs down in the spirit of less-is-more audio.

These amps are so small you can get creative with an enclosure. One guy even boxed it in a neat little black cardboard box. Some people have used wood cigar boxes. It basically comes down to your DIY skills. Maybe someone should use Lego blocks. My plan is to put my upgraded-version into a black-anodized Aluminum enclosure.

Here's my friend's temporary setup. He used the Mundorf Supreme caps as well. Hi spower supply is the Mean Well RS-100-12 100 watt SMPS.

Edited November 26, 2013 by rhing

[billybob]

Just hooked up the Lepai 2020a+ with it's power supply. Connected to Klipsch T-3000 pair and listening now to Satrad Sirius straight to amp. The Jazz channel I am on is sounding pretty good I must say.

This is very impressive and I may have to do some nearer field listening to become critical of this T-Amp. This is not as easy a chore to be critical at first as I had thought. This will take some time.

[billybob]

OOPs, continuing to listen I now can see how the modding comes into play. Not that it takes much to impress me. Sounds good enough on classical. Still though will have to listen more. Thinking about the SMSL 50 amp also. Wait, I can go and find a beefier PS.

[DizRotus]

The TC 760LC phono preamp I purchased from billybob finally arrived. It looks like new and sounds great. I couldn't be more pleased.

So far, I've used it only with the newest TDA7297. Vinyl sounds better than Pandora (which sounds very good) though this chip amp.

Eventually, I'll use it to play vinyl through the SMSL SA-S1 and SMSL SA-50 amps.

Soon I'll modify the TDA7297 with the poorer sound and compare the modified version to the stock unit. I'd rather make critical comparisons using vinyl as the source. This phono preamp will permit that.

Neil