The cut-off is about 72Hz, it uses a Sallen Key filter with 2 x 22k resistors and 2 x 100n capacitors.
I am in the process of drawing up a schematic for the standard version of the amplifier. There is no high-pass filter in the L & R channels as their input is taken straight from the volume control. The sub channel is derived from the output the volume control via a summing amplifier.
The improved one looks to be basically he same circuit layout apart from the toroidal output inductors and larger decoupling capacitors. The input sockets have been mounted on the board together with a switch.
Does the stereo channel include HPF? or only the mono channel have LPF.
What about the slope?
Can it be modify?
Thanks in advanced
Thanks,
the 100Hz crossover figure was taken from one of the sellers page.
I have just finished auditioning my new 2.1 amp and found it really problematic with FM, it must be the toroidal inductors? As for the sub, my big old Tannoys need no help and I found the treble needed to be turned right up.
You are right there is no filter on L & R.
I switched back to my $17, 2 channel, YJ board and FM was good and clear. I'm sticking with this little board, to my ears, it's perfect.
Just when I was I thinking deluxe would stand for an improved version...
Any luck bypassing these tone controls?
Any luck bypassing these tone controls?
radiosmuck,
The standard 2.1 board with the ferrite SMD inductors does not cause any problems at all on FM even with the receiver on the same bench and a whip antenna. Even MW was usable with the ferrite rod antenna in the radio. I'd be surprised if the toroids were any worse.
I am wondering if the mistake that I found on my board is duplicated in the de-luxe version. See my post #303 for details. This could well cause all manner of spurious emissions as the two chips are not synchronised.
I'll have a poke around with a spectrum analyser when I get the chance to see if it does radiate but first impressions tell me it is clean compared with a PC.
By the way the treble control is only top cut so the response is flat when it is turned up to max. There is no treble boost.
The standard 2.1 board with the ferrite SMD inductors does not cause any problems at all on FM even with the receiver on the same bench and a whip antenna. Even MW was usable with the ferrite rod antenna in the radio. I'd be surprised if the toroids were any worse.
I am wondering if the mistake that I found on my board is duplicated in the de-luxe version. See my post #303 for details. This could well cause all manner of spurious emissions as the two chips are not synchronised.
I'll have a poke around with a spectrum analyser when I get the chance to see if it does radiate but first impressions tell me it is clean compared with a PC.
By the way the treble control is only top cut so the response is flat when it is turned up to max. There is no treble boost.
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Looks like a design flaw.
But if it can be tweak as baffle step compensation by lower the frequency range , then it will be great
I have just finished swopping between the boards and amps that I have purchased over the last year or so and I have decided my cheapest of the cheap, $6, TDA7297F comes out on top.
Is this the one in the "hey it's cheaper than lunch" thread? That amp is class AB and I don't think can drive 40 watts. Are you comparing sound quality at moderate SPL's? It may be that you have super efficient speakers and are using such low power that the TDA is actually operating in class A mode. In any event, that is a good finding for you. But bad in that you spent all this money on more expensive amps to find out the cheapest sounds best to you.
I have a TDA7297 and compared against a Sure TPA3110, and found the latter better. The TDA did have a stronger bass (higher power), but the 3110 sounded more refined, although both can make the owner happy.
I've been reading this thread, wondering if the YJ 3116 would best the Sure 3110 in sound quality, not only power. I've had some YJ pieces in the past, build quality seems to be very low, speacially the connectors.
I've been reading this thread, wondering if the YJ 3116 would best the Sure 3110 in sound quality, not only power. I've had some YJ pieces in the past, build quality seems to be very low, speacially the connectors.
The $10 Sure 3110 I have is outstanding and power differences aside just as good as the 3116 to my ears. The 3116 board is more moddable and the higher power is handy.
Interesting. I have a couple of the TDA7297 boards from China and for me they don't really measure up to the TPA3116 or TA2020. It sure is a good deal though. I bought a couple and they get used.
One ended up in a "chassis" from a broken stamps.com scale.
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KJA,
You have good hands! You turned all the "nick-nack" boxes into nice looking chasis for all these small amp boards
i wish I can do that.Regards,
KJA,
You have good hands! You turned all the "nick-nack" boxes into nice looking chasis for all these small amp boards
Regards,
Thanks!
My wife laughs at how many "things" get transformed into audio equipment.
Yesterday, I made a case for this little MP3 player to use in the workshop.
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My main speakers are very efficient, only req. .085W RMS/ch for serious listening. Even replacing the TA2020 amp used on my desktop with a 7297 and driving a pair of Minimus 7's sounds better.
There is none of the FM interference which I found to be troublesome to a greater or lesser degree on all the D amps I have purchased. Bear in mind, they have all been very inexpensive on line purchases and I do not tweak. I'm guessing all you guys are tweaking away because you are not that happy with the sound either?😉 Is it possible to tweak these little 7297 boards?
I can remember way back in the UK, rocking with just a pair of Leak TL12's, so big watts came later as a feature we all needed.
Just installed the Bourns and they do sound very good compared to the stock and the Wurths I replaced them with.
That is good to hear. I've had a few different T/D/AB chiamps, and the 3110 sounded best to me. I am building a bi-amplified 2-way tower, so the extra power will be useful.
The 3110 and 3116 boards in question are similar regardings mods, but the 3110 is easy to screw up. 🙄
Too bad Oscons's SEPC caps goes up only to 16V, it's a good match to the 3110 chip power section.
Jail aside, I got curious about running filterless. Bourns inductors are well regarded, but expensive.
I just got my $10 3110 board from Sure today. It sounds very good and like a miniature version of the 3116 but with less power. For applications like a MP3 player or desktop radio with 6watt or less requirement, the value is unbelievable. Very happy with it.
I also got the $18 BT-1 Bluetooth module from PE and connected that to the 3110. The sound quality through BT is very surprisingly good. For those of you who have not tried this - it is very liberating to not be tethered by a cable between your source and he speaker. Similar to the reaction you got the first time you used WiFi compared to 10baseT hard line for Internet to your laptop. For background and casual listening around the house I think this is he way to go as I can control the music remotely from my tablet or iPhone. Give it a try!
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I almost got a set of the Wurths to try. I am really liking the Bourns too. Much better dynamics than the ICE parts.