Cross Channel Problems
I'm actually having cross channel issues with my eBay TDA7297. Especially on certain piano notes it's loud - it sounds like buzzing.
I attached a picture of balance settings. PC is a source, I tried two different sound cars, same issue. When L channel is at zero and R channel say 33 in balance volume settings I can hear in the left channel the distorted version of what I'm assuming is the right channel.
Same thing the other way - I can hear sounds from the R channel when it's at 0, while L is on high level - however, audible buzzing on the right channel is not as loud as in the opposite situation.
I can't hear this cross-talk/distortion through the headphones in the same PC output at all.
I have following slight modifications on my eBay board:
- removed the pot, plus I added 47k input load resistors (in to ground)
- bypassed diode with solid copper wire
- replaced the stock power cap with an array of 5x470uF+1x2200uF (generic caps..)
+ I kept the input jack connector
Can you help me troubleshoot this? Where am I getting the cross talk from?
Thank you!
I'm actually having cross channel issues with my eBay TDA7297. Especially on certain piano notes it's loud - it sounds like buzzing.
I attached a picture of balance settings. PC is a source, I tried two different sound cars, same issue. When L channel is at zero and R channel say 33 in balance volume settings I can hear in the left channel the distorted version of what I'm assuming is the right channel.
Same thing the other way - I can hear sounds from the R channel when it's at 0, while L is on high level - however, audible buzzing on the right channel is not as loud as in the opposite situation.
I can't hear this cross-talk/distortion through the headphones in the same PC output at all.
I have following slight modifications on my eBay board:
- removed the pot, plus I added 47k input load resistors (in to ground)
- bypassed diode with solid copper wire
- replaced the stock power cap with an array of 5x470uF+1x2200uF (generic caps..)
+ I kept the input jack connector
Can you help me troubleshoot this? Where am I getting the cross talk from?
Thank you!
Attachments
Salis, would it make sense to turn entire left section with the input caps 90 degrees clockwise? That way the inputs could be closer to the chip and traces a bit shorter? And possibly it would give you more space for longer input caps, without making the pcb bigger.
While I wait for my Digikey order to complete my DUG TPA3116 PBTL amps, I pulled my TDA7297 chip out of storage to play around with it.
This little amp rocks. I will have to do some head-to-head comparisons to my heavily modified Yuan Jing TPA3116 blue amp with CineMag input transformers. This is the best I've heard this little chip amp sound, and it might give my Class D amp some competition. I'm using this amp with the same modified Astron RS-12A regulated linear power supply I've been using with my TPA311x amps.
- Replaced stock volume pot with 50k log taper, 21-position SMD resistor stepped attenuator
- Replaced stock .22uF metallized Polyester film caps with 1uF/25V Black Gate N non-polar electrolytic capacitors
- Replaced large stock power supply electrolytic cap with 2,200uF/25V Panasonic FM cap
- Replaced DC polarity protection diode with a small jumper wire (Kimber Kable TCSS, 19AWG)
- Removed 3.2mm mini stereo plug and directly wired inputs to RCA connectors
- Removed 100nF ceramic cap bypassing the Panasonic power supply cap
- Wired signal inputs with Kimber Kable TCSS, 19AWG Teflon-insulated Copper hook-up wire
- Wired DC power input with 16AWG Teflon-insulated Silver-plated Copper Mil Spec wire
- Replaced stock 2P terminal blocks with Weidmuller 2P terminal blocks
This little amp rocks. I will have to do some head-to-head comparisons to my heavily modified Yuan Jing TPA3116 blue amp with CineMag input transformers. This is the best I've heard this little chip amp sound, and it might give my Class D amp some competition. I'm using this amp with the same modified Astron RS-12A regulated linear power supply I've been using with my TPA311x amps.
You have to have hf ps bypassing. Solder a X7R, 100n, 100V with as short leads as possible on the chip pins as close as possible to the package.
Nothing large or far away can bypass at high frequencies because the package inductance and the trace inductance (respectively) become so large they take the hf bypass cap 'out of the circuit.'
Cheers,
Jeff
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Not really, but I've considered making the board fit 4x Orange Drop capacitors since they sound so good with it. Having the inputs away from the outputs reduces RF, and the inputs run against a copper pour below them. But also the board is designed for shielded outputs. It's good given proximity etc to shield a bit until the binding posts.
While the demo was delayed, due to enclosure theft, I'm about to test a way to make it appear as though there's more capacitance on the chip side. It needs more for inefficient speakers (87db for example), but the room is costly and parts add up so I'm going to do something else briefly before one more board change. It might add a few dollars for bigger PSU caps, however.
2nd harmonics are bad for the sound of this amp. Dale based stepped attenuators and signal resistors should be avoided. Input R close to it is sorta risky for response. I found the cheap DACT ripoff Chinese stepped attenuators to work well, like a change in amplifier difference from Dale resistors.
I thought that might be interesting to someone.
I thought that might be interesting to someone.
I brought my TDA7297 amp to a friend's home to audition against his modified YJ TPA3116 amp and a slightly modified Sure TPA3110 with Panasonic OSCON caps.
With all the amps, we used the same modified Astron RS-12A regulated linear power supply. We also used a Music Reference tube preamp using a single RAM Labs 12A7 dual triode. My friend has a pair of Klipsch Forte IIs with the Bob Crites crossover cap upgrade kit and Titanium tweeter diaphragm upgrades.
We were both surprised at how well the TDA7297 held up to the TPA3116. It had a smoother treble and the bass was comparable, although the TPA3116 dug a little deeper. The soundstage with the TDA7297 was deeper and the amp's sound had greater presence. The TPA3116 had better definition of notes in terms of strike and decay. Another interesting thing was that the TDA7297 sounded better as a standalone integrated amp. The tube amp made the TDA7297 too polite. We both marveled at how incredibly quiet the TDA7297 amp was between tracks and during quiet passages, and it has no power on/power off thumps like the TPA3116 amp.
We also compared the TDA7297 to the Sure TPA3110 amp. I had removed the Ferrite beads, so the Sure amp had no filter at the output. The bass had a roll-off around 45-50 Hz, but the midrange and treble tone was comparable. My friend actually preferred the Sure TPA3110 over the TDA7297. To my ears, they were similar aside from the bass.
This was a fun listening session, and we played everything ranging from rock to jazz to country to large orchestral music. With really high efficiency speakers like the Klipsch Forte IIs, the TDA7297 has to be one of the greatest bargains available, even with mods and an upgraded Astron power supply. We didn't have time, but my friend will compare the amp to his DRD 300B SET mono blocks (he prefers his modified TPA3116 to them).
It will be interesting once better amp boards like Destroyer OS's TDA7297 comes out. For now, the $5 amps from eBay are respectable with some modifications.
In my own listening, I still prefer my modified YJ TPA3116 with input transformers, but this setup costs a lot more than my simple TDA7297. I had purchased the 1uF Black Gate N caps a while ago when they were affordable. I would think some compact film caps like Wima MKP2 would do quite well in this amp.
With all the amps, we used the same modified Astron RS-12A regulated linear power supply. We also used a Music Reference tube preamp using a single RAM Labs 12A7 dual triode. My friend has a pair of Klipsch Forte IIs with the Bob Crites crossover cap upgrade kit and Titanium tweeter diaphragm upgrades.
We were both surprised at how well the TDA7297 held up to the TPA3116. It had a smoother treble and the bass was comparable, although the TPA3116 dug a little deeper. The soundstage with the TDA7297 was deeper and the amp's sound had greater presence. The TPA3116 had better definition of notes in terms of strike and decay. Another interesting thing was that the TDA7297 sounded better as a standalone integrated amp. The tube amp made the TDA7297 too polite. We both marveled at how incredibly quiet the TDA7297 amp was between tracks and during quiet passages, and it has no power on/power off thumps like the TPA3116 amp.
We also compared the TDA7297 to the Sure TPA3110 amp. I had removed the Ferrite beads, so the Sure amp had no filter at the output. The bass had a roll-off around 45-50 Hz, but the midrange and treble tone was comparable. My friend actually preferred the Sure TPA3110 over the TDA7297. To my ears, they were similar aside from the bass.
This was a fun listening session, and we played everything ranging from rock to jazz to country to large orchestral music. With really high efficiency speakers like the Klipsch Forte IIs, the TDA7297 has to be one of the greatest bargains available, even with mods and an upgraded Astron power supply. We didn't have time, but my friend will compare the amp to his DRD 300B SET mono blocks (he prefers his modified TPA3116 to them).
It will be interesting once better amp boards like Destroyer OS's TDA7297 comes out. For now, the $5 amps from eBay are respectable with some modifications.
In my own listening, I still prefer my modified YJ TPA3116 with input transformers, but this setup costs a lot more than my simple TDA7297. I had purchased the 1uF Black Gate N caps a while ago when they were affordable. I would think some compact film caps like Wima MKP2 would do quite well in this amp.
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I don't think the 7297 would work well with transformers. Maybe, it works bad with straight wire out of a simple low DC CD player. Most amps would be fine, inconsequential to the almost no DC, but the 7297 doesn't appear to be.
The Orange Drop spraques (multiple) were good, but my kits will feature the PHE450, as it's easily the best yet; and available in 1uf.
How much capacitance do you have at the chip? 10-12kuf would be prefered for bass, on not-super efficient speakers. But a capacitor multiplier works better. The higher voltage is nice too; it provides a lot of headroom too.
I'm going to compare some good speaker wire to balanced cables as speaker wire soon. This will tell us how the balanced output plays with cables. Lastly, a little bit of shielding on the output wires next to the chip is good. Mine use 1st rate chips though, so I can't vouch for all the sound from amp to amp from China at $6.
The Orange Drop spraques (multiple) were good, but my kits will feature the PHE450, as it's easily the best yet; and available in 1uf.
How much capacitance do you have at the chip? 10-12kuf would be prefered for bass, on not-super efficient speakers. But a capacitor multiplier works better. The higher voltage is nice too; it provides a lot of headroom too.
I'm going to compare some good speaker wire to balanced cables as speaker wire soon. This will tell us how the balanced output plays with cables. Lastly, a little bit of shielding on the output wires next to the chip is good. Mine use 1st rate chips though, so I can't vouch for all the sound from amp to amp from China at $6.
I wouldn't think of using input transformers on the TDA7297 even though my ARC LS7 has 2uF output caps to block DC going to the chip amp. I want to keep this amp "as is" to use as an integrated in warm weather--same as my Sure TPA3110 Class D amp. As for additional bass, my Klipsch speakers have plenty of slam and deep bass. On the close of "Saturn" in Holst's "The Planets," the bass section surges through the speakers and floor to give the illusion of sitting in the concert hall (Decca 475 8225). I only have the single Panasonic FM 2,200uF cap on the amp board. Besides that, I have the Astron RS-12A regulated linear power supply modified with a 22,000uF Rifa PEH-200 electrolytic and another 2,200uF Panasonic FM electrolytic performing filtering duties.
I have left my my unmodified TDA7297 amp on permanently for the last 18 months, it is so quiet, I see no reason to turn it off.
The stock $5 amp sound great to me, then again I'm not a fanatic chasing the fantastic.
How many times have I read on forums, " I have purchased an xyz piece of audio equipment, what does it sound like?". Since the internet, folk seem to have lost the ability to form their own opinion.
An author of a loudspeaker and enclosure design book suggests that sound is "Personalized" by different anatomical features such as bone structure, hearing sensitivity and slight differences within the inner ear from listener to listener."What does it sound like?" is a bad question without a reference point.
I think it's more appropriate to ask "What does it sound like compared to the ebay stock unit?"
If the author is correct, which I find believable, then components swapping for a better sound would need to be on an individual basis rather than a one mod fits all?
Yes and no. Assuming that we perceive things differently, there's a coherence of perception between each person. If i perceive something longer than another person, and that thing gets halved, we will both perceive it shorter than before, granted we will perceive it differently as size, but for both of us it is very clear that it is shorter.
Hi to all of you. This is a good thread.Maybee someone could shed some light on this.
I bought two of these amps from the bay. They mostly have smd components and small disc type volume pot.
Neither of would work up to half volume then they went flat out both were the same.
Then tried with a dact stepped pot both still the same as before (very odd) .
Thanks for any imput Richard.
I bought two of these amps from the bay. They mostly have smd components and small disc type volume pot.
Neither of would work up to half volume then they went flat out both were the same.
Then tried with a dact stepped pot both still the same as before (very odd) .
Thanks for any imput Richard.
Does this mean that you don't get anything, until you get full blast?
If using a source that has its own volume control and using the amp with a simple resistive load at input (just like volume pot all the way up), then, in that case, here's the question: Does the noisegate/squelch circuit behavior happen when varying the source's built in volume control?