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Old 28th April 2013, 06:31 PM   #111
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Quote:
Originally Posted by xrk971 View Post
In general, do you guys really notice an improvement in imaging with change from basic ceramic input caps to polyester film caps or boutique $$$ caps? Can it be improved or is this like the whole upgrade with big expensive speaker cables vs lamp cord or cat5 cable? Maybe a little OT....
If viewed as "compensation" all such things make sense, albeit some may be quite indirect and/or misleading. Let's please postpone "tweaks" until after the amplifier is running from clean linear regulator power.

Earlier, on Activexp's amp, I saw an AudioWind Regulator or ElectronicsSalon regulator, and that looked a reasonable and perhaps important first step. At those stores, I'm fairly sure that Juli and crew have checked the quality and that chip regulator is authentic and measures within specs. That board has an AC input for a transformer; but, as an alternative, it also has a DC input which could be powered by a CRC linear supply, an SMPS, or a capacitive multiplier. So, you do have multiple options.

After installing reasonable linear regulated power, the linear audio amp will be more directly informative about which tweaks are actually useful. When it comes to flea power hi-fi: Regs first. Tweak later.

Meanwhile, back to tweaking:
At small signal input, Ceramic Disc caps (like came with my board) have, perhaps the most beautiful level crisp tone ever. But they can fail at imaging depth. Running a close second on tone, but with greater depth, is the old faithful polyester dip cap, popular for use in tone controls. Larger polyester and electrolytics alike have treble droop. SO, a smaller value ceramic may be teamed with a polyester in a conglomerate effort. Or, tiny plus bigger polyester caps can be teamed together. For box caps of 220 nanofareds 224 I have no idea. But, the 330n red Wima is okay for a box cap. I don't know if it will outperform the existing caps though.

The caps on the SMD board might not need replaced. And, there's a chance that the ceramic disc caps on the through-hole board might not need replaced. But, the only way to find out is to try it.

However, I would not bother replacing the factory caps if the amplifier is running from a cheap SMPS. That's because I don't want to close the barn door after the horse escaped.
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Last edited by danielwritesbac; 28th April 2013 at 06:37 PM.
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Old 6th May 2013, 09:19 PM   #112
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I'm still very much enjoying my $6 amp.
Found this, it might be of interest? Compact High-Performance 12V 20W Stereo Amplifier Circuit Diagram
Terry
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Old 29th May 2013, 03:20 PM   #113
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Quote:
Originally Posted by redjr View Post
I have one, but it's nothing more than a 2013 version of the transistor radio. . Good enough to throw in the picnic basket, with a pair of small speakers, but beyond that nothing stellar. It's very cheaply made and looks it too! I bought it because of all the noise about the Lepai brand. I gave it to my son to play with.
Sorry for late response, been too engrossed with the remarkable 7297!

Thanks for the insight re the LP-V9, was thinking of getting one to tinker with but don't think I'll bother now. I rather fancy a headphone amp kit instead

Do any of the gurus on here know if the 7297 chips can be paralleled (I think that's the technical term for increasing the power by using more chips)?
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Old 29th May 2013, 05:12 PM   #114
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Sorry for late response, been too engrossed with the remarkable 7297!

Thanks for the insight re the LP-V9, was thinking of getting one to tinker with but don't think I'll bother now. I rather fancy a headphone amp kit instead

Do any of the gurus on here know if the 7297 chips can be paralleled (I think that's the technical term for increasing the power by using more chips)?
Try this
Amplifier PCB board TDA7294 Amplifier board(1+1) Dual channel 2*85W-in Printer Parts from Office & School Supplies on Aliexpress.com
I purchased and received a pair last week, how could I not for the price?
I have been comparing them to the 7297 which I love but I cannot detect any audible difference between them. I guess it depends on how much power you require.
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Old 29th May 2013, 07:39 PM   #115
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Default Still liking the less than lunch amp

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Originally Posted by MeTarzan View Post
I am liking this $6 amp too. It is in a $2 enclosure with $2 worth of speakers. I hope it sounds as good on the $4 PSU I am waiting for as it does on bench power. Counting a jack or two I have yet to install the whole project will come in well under $20.

Me too, MeTarzan!

.......I'm still liking mine. Can't seem to take it out of the system it's so darned good!

I've played it many weeks now. Bass is great, mids and highs accurate and non-fatiguing on my Klipsch La Scalas. And, ZERO background noise. Can't beat that.

I see they've changed the inputs from mine which is two RCA jacks (L & R). Now these come with a single jack, which I am guessing is similar to a headphone jack.

Still $6 delivered though. What are you guys waiting for?

Mark
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Old 30th May 2013, 09:46 AM   #116
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Quote:
Originally Posted by radiosmuck View Post
Try this
Amplifier PCB board TDA7294 Amplifier board(1+1) Dual channel 2*85W-in Printer Parts from Office & School Supplies on Aliexpress.com
I purchased and received a pair last week, how could I not for the price?
I have been comparing them to the 7297 which I love but I cannot detect any audible difference between them. I guess it depends on how much power you require.
Ah yes, I know the 7294 very well and have a couple of amps based on that chip. The sound quality is first class but to my ears the 7297 is slightly different in a very pleasing way and continues to impress for something so basic. Remarkable for a chip that was designed for TV's and portable radios!
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Old 30th May 2013, 01:47 PM   #117
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Originally Posted by activexp View Post
Ah yes, I know the 7294 very well and have a couple of amps based on that chip. The sound quality is first class but to my ears the 7297 is slightly different in a very pleasing way and continues to impress for something so basic. Remarkable for a chip that was designed for TV's and portable radios!
I've switched back to the 7297. I have not Guilded the Lilly by building a box for it yet, I might just screw it to the back of my equipment cabinet, out of sight, with the pot just visible. I leave it on all the time.
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Old 30th May 2013, 10:18 PM   #118
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Yes, the TDA7297 easily outperforms the generic datasheet schematic for TDA7294.

TDA7294
However, it may be fascinating to notice that the more powerful chip amplifiers, like TDA7294 and many more models, all share almost exactly the same generic schematics in their datasheets, despite the many different chip designs; and, that means that there's a lot of kits and even quite a few productions amplifiers suffering nonspecific support, aka junk. Those generic schematics show you where the parts go, but not how to optimize the audio quality. Non-specific support causes hot running, odd tone/coloration and sometimes frailty. That's the usual condition of most kits, and some are worse. The chip is fine, but the schematic is junk, so I made a different schematic for it.

TDA7297
One really unusually good thing about the TDA7297 is that it runs very nicely on the simple datasheet schematic and the only quirk that I could find is that it needs a rather high value potentiometer, such as 50k~100k range, which conveniently comes with most of the ready-to-use kits on ebay. This particular chip's input circuit promotes nice level sounding audio without having to add a buffer. It isn't that the TDA7297 has great specs. It sure doesn't. However, the good sound is mostly coming from the fact that it runs near optimal on the datasheet schematic, and that is rare. A linear regulator is a good upgrade for it, and with that sort of help, it does some passable hi-fi. So, the main deal is that the TDA7297 is almost effortless to use for obtaining good results expediently.
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Last edited by danielwritesbac; 30th May 2013 at 10:23 PM.
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Old 19th June 2013, 04:01 PM   #119
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Still very happy with my lunch money amp. It's now housed with a USB/MP3 player with FM tuner and it all works very nicely. This module was hopeless with a class D amp as the high speed switching caused interference on FM drowning out all but the strongest stations.

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Old 19th June 2013, 05:07 PM   #120
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Still very happy with my lunch money amp. It's now housed with a USB/MP3 player with FM tuner and it all works very nicely. This module was hopeless with a class D amp as the high speed switching caused interference on FM drowning out all but the strongest stations.

Click the image to open in full size.
NICE!
All I've done with my board is to place it on a piece of non slip mat, dabbed a black felt tip on the led and hid it behind some CDs. I leave it on all the time.
I had the same problem with FM on both a Lepai and an SMSL 2020 amp, not so the tda7297.
I still cannot get over how good this amp sounds, and it must sound good, none of the modders have made recommendations.
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