chip amps: Almost everything you ever wanted to know

[mboxler]

I accidentally hooked up my Lepai 2020a+ to my battery basackwards and fried it.

Saw this modded one and bought it (the wood also matches my zigmahornets). A little pricey, perhaps, but really sounds good.

http://nsmt-loudspeakers.com/Modified-Lepai-T-Amp

Mike

[rhing]

Here is my second TDA7297 chip amp that I mounted on a makeshift chassis using scrap wood pieces I still haven't hooked up the RCA jacks directly to the amp circuit board, because I just wanted to hear how it sounds in complete stock form. Surprisingly, it sounds very good. My first unit, which I upgraded with Mundorf Supreme film caps had a high-mid/treble glare with the stock orange Polyester film caps. This unit sounds more tonally balanced. I can only reason that:

1. The quality of the stock components is not consistent, or
2. The RCA-to-mini-stereo jack cable is attenuating the glare and creating tonal balance.

I'll keep this around as a loaner so some of my other local audio friends can audition this unit on their own.

One thing is certain in that this little chip amp, even in stock form, outperforms my SMSL SA-S1 Tripath TA2020 T-amp. I still really like SMSL amp, but this TDA7297 creates a larger, deeper soundstage, has a noticeably cleaner midrange and treble, greater headroom and a more focused image.

[ClaudeJ1]

If you look at my Avatar, you can see I use a Peavey FH-1 (cheaper and more ruggedly built than old LaScala cabs). Inside, I have EVM-15L woofers with brand new recones using OEM parts.

I'm driving this bass horn with a strock $22 Lepai from Parts Express being bandpasse filterered by a Behringer DCX-2496 because I hate inductors. DizRotus heard it when I was still in Michigan........FYI

[rhing]

If you look at my Avatar, you can see I use a Peavey FH-1 (cheaper and more ruggedly built than old LaScala cabs). Inside, I have EVM-15L woofers with brand new recones using OEM parts.

I'm driving this bass horn with a strock $22 Lepai from Parts Express being bandpasse filterered by a Behringer DCX-2496 because I hate inductors. DizRotus heard it when I was still in Michigan........FYI

Claude,

I would love to listen to your speaker setup. I am a Michigan native too, and I now live in California, and my home isn't large enough to accommodate an array like yours. I love big, efficient horn-based speakers like Klipsch and Altec Lansing speakers. My dream set is a pair of Altec Lansing Model 19s or Klipschorns, but your speakers might trounce them.

Anyway, I would encourage you to try this TDA7297 chip amp to drive your bass horns. You can use the same power supply that you use with the Lepai and you'll get lower distortion and greater headroom assuming your bass horns are a nominal 8 ohm load. Unlike Class D amps like the Lepai TA2020, there is no high frequency switching noise to filter out with an output filter consisting of inductors and multiple capacitors. The output is straight from the transistors in the chip itself. The input just has the two capacitors.

I think the TA2020 Tripath is the cream of the Tripath crop of T-amps, and that's why I bought an SMSL SA-S1. I've tried other T-amps like the Sonic Impact 5065 Gen 2 (TA2024, which I modded), and the Virtue Audio 2 (TK2050), but the SMSL SA-S1 amp beat those hands-down. I think a modded Lepai TA2020 would be comparable to the SMSL amp, but this TDA7297 in stock form is better yet, especially in the lower frequencies. With additional low-budget mods like what I recommended to DizRotus, this amp goes to another level of performance.

These amps haven't hit these shores yet, but now a Chinese manufacturer is coupling a tube input buffer with the TDA7297 chip amp:

http://www.ibuyla.com/Product/10665163064/12AT7_vacuum_tube_push_new_DC_12V_power_supply_TDA7297_bile_stone_after_power_amplifier_(for_cars)/

I have no idea how they came up with this odd name, but it's probably a decent sounding amp with that tube providing some warmth.

Happy Thanksgiving!

[mike stehr]

TDA-7297 gall stones after amplifier?

[DizRotus]

to Claude, " . . . my home isn't large enough to accommodate an array like yours."

Rich,

I heard Claude's system 3 times. The first two were in a small basement of a small condo. It sounded fantastic both times. The third time was in a larger loft condo in an old commercial building in downtown Pontiac, MI that had been built as a new car showroom in the 30s. Claude's loft was in the upper floor created out of what had been a single floor showroom with a 30' ceiling. While the larger space gave Claude's wall of sound more room to breathe, it's excellent qualities were not wasted in that condo basement. "Large enough" is in the ear of the beholder.

Bear in mind the Lepai only handles the mid-bass from the LaScala-like Peavys, The room shaking bass is provided by a tapped horn powered by Claude's Lab 112 B&W amp.

I'm liking the 2nd TDA7297 better than the first, and both better than my Lepai TA2020, SMSL SA-S1 or SMSL SA-50. It's hard to imagine room for a whole lot of improvement, but I'm eager to try.. Soon I'll start switching parts. I'll try to be scientific and change a single variable at a time to properly evaluate the changes, if any.

Edited November 30, 2013 by DizRotus

[ClaudeJ1]

to Claude, " . . . my home isn't large enough to accommodate an array like yours."

Rich,

I heard Claude's system 3 times. The first two were in a small basement of a small condo. It sounded fantastic both times. The third time was in a larger loft condo in an old commercial building in downtown Pontiac, MI that had been built as a new car showstopper in the 30s. Claude's loft was in the upper floor created out of what had been a single floor showroom with a 30' ceiling. While the larger space gave Claude's wall of sound more room to breathe, it's excellent qualities were not wasted in that condo basement. "Large enough" is in the ear of the beholder.

Bear in mind the Lepai only handles the mid-bass from the LaScala-like Peavys, The room shaking bass is provided by a tapped horn powered by Claude's Lab 112 B&W amp.

I'm liking the 2nd TDA7297 better than the first, and both better than my Lepai TA2020, SMSL SA-S1 or SMSL SA-50. It's hard to imagine room for a whole lot of improvement, but I'm eager to try.. Soon I'll start switching parts. I'll try to be scientific and change a single variable at a time to properly evaluate the changes, if any.

My system is now in a house with a 13.5x19 foot living room. Same "stack" and surrounds, BUT I now have twin (front and rear wall centers) Danley DTS-10 subs and I'm is bass heaven. I have one of my MWMs-like bass horns designed and built, and will soon finish the other. Hoping I will not need the PEQ on the woofer section once I go from a 2.8 foot horn to a 5 footer (55 Hz. cutoff, then down to the Danley TH subs) with the same EVM 15 L drivers. I just got a B&K 12 channel amp with discrete volume controls for each and hope to run the whole thing with tri-amps passively. I will also experiment with active for the whole stack, but will try passive first. That little 2020 is still amazing in stock form, though. I probably will not use chip amps much longer, but you never know.

[snailtrax]

Alright rhing, you have started something here. I want to mod one of these TDA7297 amps similar to what you have done in post 170. I want the best recommendation you can give for capacitors and whatever else needs replacing. I want to get rid of the volume pot and replace all that I can with point to point wires. I am now going to ask a large favor. Can you draw up a schematic that a layman can understand. I would like to retain the original pc board for the visual effect. I am going to use two boards to mount everything like you did in post 170. I already have two of the amps that just arrived Wednesday. Thanks, Bill

[rhing]

Hi Bill,

PM me and I can go over the details of what you need.

Rich

[ClaudeJ1]

I heard Claude's system 3 times. The first two were in a small basement of a small condo. It sounded fantastic both times. The third time was in a larger loft condo in an old commercial building in downtown Pontiac, MI that had been built as a new car showstopper in the 30s. Claude's loft was in the upper floor created out of what had been a single floor showroom with a 30' ceiling. While the larger space gave Claude's wall of sound more room to breathe, it's excellent qualities were not wasted in that condo basement. "Large enough" is in the ear of the beholder.

A huge part of what made my all horn electo-acoustic transducers sound good in ANY room is the Audyssey Multi EQ of my receiver. Seriously. The 7 series gives your 7 channels of preamp outs, so you can use outboard signal processing and xovers, if you wish, and still get the benefit of Audyssey room correction. But if you have great horns to start with, so much the better.

Edited November 30, 2013 by ClaudeJ1

[DizRotus]

Now that the USPS finally delivered my TC-760LC phono preamp posted by @billybob weeks ago, I'm in a position to listen to vinyl being played through my chip amps. As an aside, I couldn't be more pleased with the TC-760LC.

The attached photo shows my test bench (my late mother would be mortified, if she weren't already mortified, to see the family piano used as a test bench). On the right is the stock TDA7297 (the 2nd one received, which sounded better than #1). On the left is the modified TDA7297. Each amp has spikes from the barrier strip to which alligator clips can be used for quick change connections to speakers. The modded amp has alligator clips to permit quickly switching between coupling caps.

The modifications, in the order performed, as suggested by Rick, aka rhing, to date are:

• Replacing the stock Chang 2,200 uf 25v power supply cap with larger Panasonic version;
• Removing the volume pot;
• Removing stock coupling caps; and
• Inserting either WIMA; or
• Panasonic coupling caps.

After limited listening, I'm ready to state the following:

• The modified amp now sounds markedly better than the stock amp;
• The most significant improvement followed the the upgraded power supply cap;
• the other modifications produced real, but more subtle improvements;
• My 65 y.o. ears cannot discern a significant difference between the WIMA or Panasonic coupling caps; and
• the cumulative results of all mods (using either WIMA or Panasonic coupling caps) seem greater than the sum of the parts.

Subjectively, the bass is tighter and the sound seems more 3D with the modified amp. A strength of the TDA7297 is the ability to reproduce the sound of horns, whether sax or brass. That quality is enhanced by the mods.

If interested, the photo also shows the Dynaco QD-1 (which Dave Mallete tempted me to get) and the TC-760LC. The TDA7292s and QD-1 are sitting on a Dynaco FM-5. The barrier strips behind the QD-1 enable easier and more secure connections to the QD-1. The spacing of 12 thumb-screw terminals on the rear of the QD-1 makes connections difficult and unstable. The thumb-screws were replaced by slotted screws that can be more easily and securely tightened. Short leads from the QD-1 to the barrier strips allow for adding or subtracting components easily without disturbing the antique terminals on the QD-1. Dave Mallete knows what I mean.

I accidentally ordered 4 of the Panasonic power supply caps. Also there will be four "upgrade" coupling caps available, when the smoke clears. If anyone is interested, they're your's for the cost to ship.

As part of my new vinyl addiction, I ordered a Denon DL-110 MC cartridge. It'll be my first experience with MC. I was seduced by the price ($139 from Amazon) and favorable reviews, especially the one attached. I was especially intrigued by the predicted suitability for enjoying used records, how I feed my addiction.

Kobesky_review.pdf

[rhing]

Can you draw up a schematic that a layman can understand. I would like to retain the original pc board for the visual effect. I am going to use two boards to mount everything like you did in post 170. I already have two of the amps that just arrived Wednesday. Thanks, Bill

I have assembled a diagram for the TDA7297 amplifier connections. This corresponds to the TDA7297 amp I purchased from eBay seller homemart.usa. Other amp modules may differ in their layouts and connections. I have also assembled a Bill of Materials (i.e., BOM or parts list) for anyone who is interested in upgrading the parts of their TDA7297 amp. I upgraded my second amp with 1uF / 50V Black Gate N caps. These are near-unobtainium, but Sonic Craft still has some in stock. To my ears, these are comparable to the Mundorf Supreme caps I installed in my first unit. The Elna Silmic IIs, the Wima MKP2 and the Black Gate N caps will all fit on the board. Notice, the cost of the $6 amp does increase considerably, and some people may think my BOMs are overkill, but I'm enjoying these upgrades and this amp is still performing at an astounding performance-to-price ratio.

Now that the USPS finally delivered my TC-760LC phono preamp posted by billybob weeks ago, I'm in a position to listen to vinyl being played through my chip amps. As an aside, I couldn't be more pleased with the TC-760LC.

The attached photo shows my test bench (my late mother would be mortified, if she weren't already mortified, to see the family piano used as a test bench). On the right is the stock TDA7297 (the 2nd one received, which sounded better than #1). On the left is the modified TDA7297. Each amp has spikes from the barrier strip to which alligator clips can be sued for quick change connections to speakers. The modded amp has alligator clips to permit quickly switching between coupling caps.

The modifications, in the order performed, as suggested by Rick, aka rhing, to date are:

• Replacing the stock Chang 2,200 uf 25v power supply cap with larger Panasonic version;
• Removing the volume pot;
• Removing stock coupling caps; and
• Inserting either WIMA; or
• Panasonic coupling caps.

After limited listening, I'm ready to state the following:

• The modified amp now sounds markedly better than the stock amp;
• The most significant improvement followed the the upgraded power supply cap;
• the other modifications produced real, but more subtle improvements;
• My 65 y.o. ears cannot discern a significant difference between the WIMA or Panasonic coupling caps; and
• the cumulative results of all mods (using either WIMA or Panasonic coupling caps) seem greater than the sum of the parts.

Subjectively, the bass is tighter and the sound seems more 3D with the modified amp. A strength of the TDA7297 is the ability to reproduce the sound of horns, whether sax or brass. That quality is enhanced by the mods.

If interested, the photo also shows the Dynaco QD-1 (which Dave Mallete tempted me to get) and the TC-760LC. The TDA7292s and QD-1 are sitting on a Dynaco FM-5. The barrier strips behind the QD-1 enable easier and more secure connections to the QD-1. The spacing of 12 thumb-screw terminals on the rear of the QD-1 makes connections difficult and unstable. The thumb-screws were replaced by slotted screws that can be more easily and securely tightened. Short leads from the QD-1 to the barrier strips allow for adding or subtracting components easily without disturbing the antique terminals on the QD-1. Dave Mallete knows what I mean.

I accidentally ordered 4 of the Panasonic power supply caps. Also there will be four "upgrade" coupling caps available, when the smoke clears. If anyone is interested, they're your's for the cost to ship.

As part of my new vinyl addiction, I ordered a Denon DL-110 MC cartridge. It'll be my first experience with MC. I was seduced by the price ($139 from Amazon) and favorable reviews, especially the one attached. I was especially intrigued by the predicted suitability for enjoying used records, how I feed my addiction.

Nice test rig. I really like that experimental test bench look. Actually, I am glad to hear that the Wima MKP2 caps are comparable to the Panasonic ECQP caps. They are less expensive and these should fit right onto the board to keep things neat and clean.

Your listening impressions follow mine. The 2,200uF / 25V Panasonic FM electrolytic cap in the power supply path makes a profound difference in dynamic response, bass definition and the size of the soundstage. Better input caps do reveal more detail and a slight improvement in tonality.

Thanks for sharing about the Denon MC cartridge. I may have to get one of these for my restored Kenwood PC-400U belt/idler wheel drive turntable. I have a Talisman Alchemist 2B high output MC cartridge that is a bit long in the tooth, and probably needs to be re-tipped and/or replaced.

TDA7297 Bill of Materials, Elna Silmic II Caps.pdf

TDA7297 Bill of Materials, Wima MKP Caps.pdf

TDA7297 Bill of Materials, Black Gate N Caps.pdf

Edited December 2, 2013 by rhing

[DizRotus]

Rich-

Thanks for the detailed info.

I wish I'd had the schematic, etc. in your post above before I dissected the TDA. These 65 y.o. eyes had a heck of a time seeing those tiny circuits on that tiny board. I find I have to take the bi-focals off at real close range, but put them on at slightly greater distances. The eye doc says my prescription is actually getting better as I grow older. If I live to be 200 I'll be able to throw away the glasses.

At least I'll be able to rock out the nursing home.

Edited December 2, 2013 by DizRotus

[rhing]

Just enjoy the music. I wear safety goggles when I solder, but I can still see well without my glasses.

I forgot to list wire in my parts lists.

For the connections from the board to the speaker binding posts, I use 19AWG Kimber TCSS Teflon-insulated stranded Copper wire.

For the connections between the RCA connectors, I use Mil-Spec 20AWG Teflon-insulated Silver-plated Copper solid core wire. Sometimes, I use 0.5mm Mundorf Teflon-wrapped Silver/Gold solid core wire for signal connections.

For the DC power connection, I use Mil-Spec 20AWG Teflon-insulated Silver-plated Copper stranded wire.

I always use Cardas 2% Silver quad-eutectic solder. To me, this is the best solder for audio projects. Enid Lumley of The Absolute Sound magazine conducted a test years ago comparing solder compounds by making speaker wire purely out of solder. In her final analysis, the Cardas QES won out as being the most transparent-sounding solder.

[DizRotus]

The Denon DL-110 MC arrived and, so far, it sounds great with the modified TDA7297 (Wima caps). I'm listening to Kind of Blue as I type. Miles and John have never sounded better--in my basement. I'm certain they sounded better performing live.

Part of the motivation to try a MC cartridge was getting a fantastic deal on the TC-760LC convertible MM/MC phono preamp I got from billybob to play vinyl through chip amps. Turns out the Denon DL-110 is a high output MC cartridge. Using the MM input provides plenty of gain.

As one of the many favorable reviews of this cartridge promised, this cartridge makes used records quieter than ever. According to the reviewer, the stylus tracks portions of the grooves not touched by typical MM cartridges. I can't vouch for the theory, but the results are very good.

Edited December 6, 2013 by DizRotus

[rhing]

That's really cool. I was listening to some vinyl as well with my PH5 phono stage connected to my second TDA7297 amp with the Black Gate N caps. My Talisman Alchemist IIB is a high output MC cartridge as well. With this amp's largish soundstage, vinyl playback creates a life-size image in my man cave. The sound extends well beyond the space between my speakers. I'm planning an audio get together at my home in a week, and I'm going to have my audio buddies compare the TDA7297 amp to my SMSL SA-S1 TA2020 T-amp and the combination of the ARC LS7 line stage and Dynakit Stereo 35. The guys will be blindfolded, so their listening impressions will be unbiased.

I'm glad the Wima MKP2 caps are working out for you. I used these in a Dynaco SCA-35 restoration, and I was really impressed with Wima MKP caps in the phono stage and driver stage in the Dynaco amp. If you haven't already, try the Dave Brubeck Quartet's "Time Out" or Sonny Rollins' "Saxaphone Colossus" through your set up. Piano sounds great through this amp as well. You can put anything by Bill Evans on.

[rhing]

I took my first prototype TDA7297 chip amp with the Mundorf Supreme coupling caps and installed it in a nice black anodized, brushed Aluminum enclosure that I picked up at a Fry's Electronics store. Fry's is a chain of electronic superstores out in the West Coast. Each store is about the size of a Walmart and they carry everything electronic under the sun. Anyway, the Context Engineering extruded Aluminum case cost me $25 including tax. I spent most of the morning drilling all the holes for the connectors, ventilation and Alps Blue Velvet volume pot. Eventually, I will design a thick Silver brushed Aluminum faceplate that will match my ARC gear and order it from Front Panel Express. I also installed a mini toggle SPST on/off switch that I picked up from Radio Shack. The knob is from a Chinese eBay seller. It's no longer a $6 bargain chip amp, but for about $125, I have a nice sounding little black box.

Edited December 9, 2013 by rhing

[billybob]

Glad you are both getting good results. Looking and sounding good I get it!

[rhing]

This TDA7297 is sounding really nice with my vinyl playback system, but I'm now getting that itch to explore the Texas Instruments TPA-31xx Class D amps. There's a rather lengthy thread on the diyAudio Class D forum about the TPA3118D2 amp boards from Yuan Jing, a Chinese manufacturer of low cost hi if electronics. Like the TDA7297 chip amp, these newer generation Class D amps are claimed to sound better than Tripath T-amps. For $10, it's a cheap experiment, and I can use my wood test rig to wire up the TPA3110 board and connect it to my Forte II amps.

A friend also donated a Magnavox console amp that is a single ended pentode 6BQ5/EL84 stereo amplifier. It looks like I'll have some experimentation this holiday season comparing low powered SS and tube amps.

Edited December 13, 2013 by rhing

[DizRotus]

The amp Rich refers to above can be found on eBay at:

http://www.ebay.com/itm/2-X-8Watt-Class-D-Audio-Amplifier-Board-TPA3110-2W-Stereo-Power-Mini-Amp-/110932802369

I just pulled the trigger on the amp above and the amp at:

http://www.ebay.com/itm/2-X-15-watt-4-ohm-Class-D-Audio-Amplifier-Board-TA2024-15W-Stereo-Mini-T-Amp/110932147227?_trksid=p2047675.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D18844%26meid%3D3360668026244488401%26pid%3D100005%26prg%3D8532%26rk%3D1%26rkt%3D5%26sd%3D110932802369%26

If this keeps up, I'll need to go to meetings.

Edited December 15, 2013 by DizRotus