I built an amplifier with a Chinese circuit board (CRM-Tech, TDA7293, OP NE5534, and OP07 Servo). The sound was okay, but then I swapped the NE5534 for a Burson Audio V7 Vivid pro Single.
The sound is now significantly better.
The sound is now significantly better.
Have you looked at the NJM4556? It is designed to drive 400 ohm loads, is available in a 2 channel DIP. Getting old but good performance and about 70 cents each in quantities of 10.
Don't be fooled - a quasi symmetric output is a 100% symmetric TRANSMISSION, but it is not a symmetric SIGNAL!
When impedance is symmetric you get the benefits of a symmetric transmission - you "chancel" interference at the input of your receiver.
You need to look at the whole picture, when your source signal is not symmetric you need an inverter - this adds noise. And you also invert the source noise, so it's correlated at the output and you don't gain 3dB S/N - you actually loose S/N.
A good solution is an output transformer - symmetric and galvanic disconnected with (nearly) no noise added. But in terms of S/N no win over a quasi symmetric setup.
It's done a lot in microphones and works very well btw. ;-)
I can't post the circuit but it's an OPA1611 + LME49610 as output buffer with some of the current limiting output R in the feedback loop to keep impedance low. And it's only a buffer with gain 1 - you get VERY low noise this way.
Gain happens at the symmetrical input stage and your volume control ist after that - this way you reduce the input and source noise when you dial the volume down and you end up with fantastic S/N at normal listening levels. Don't know if there is a matching product out there.
Gain staging is key for these super low noise circuits! There is a lot dynamic range wasted in normal HiFi circuits with their silly amplifications.
@IamJF I've built and tried various line driver output circuits with varying results. The separate inverted driver style circuit (very popular with lower grade pro audio equipment ie. Behringer, Alexis, Samson) has symmetry problems with input offset and hurts CMRR.
The closed loop matched driver circuit (pictured here below) performs very well with proper layout, carefully matched, low temp coefficient resistors and good PS decoupling. I've seen this circuit in Accuphase gear and other Japanese equipment. Its likely the best sounding circuit design I've heard, with and without an output transformer.
I believe the best sounding design for balanced output is using a lower impedance transformer without coupling caps and with a DC servo LPed at 5 hz. A resistor balanced ground tap across the primary sets the CMRR to max potential, referencing the floating winding to a physical ground. The key to getting the most performance out of the driver in front of the output trans primary is absolute symmetry from the op amp halves. I always recommend using the same dual op amp IC for the pos and neg driver elements to insure the same temp coefficient.
With transformers that have a single primary and secondary winding (not center tapped), the signal becomes single ended, but enjoys the same performance level of a balanced signal just by driving a transformer with another adjustable resistor referenced winding ground. This was my intention using the transformers I have, going into the amplifiers with separate floating grounds at each input.
The closed loop matched driver circuit (pictured here below) performs very well with proper layout, carefully matched, low temp coefficient resistors and good PS decoupling. I've seen this circuit in Accuphase gear and other Japanese equipment. Its likely the best sounding circuit design I've heard, with and without an output transformer.
I believe the best sounding design for balanced output is using a lower impedance transformer without coupling caps and with a DC servo LPed at 5 hz. A resistor balanced ground tap across the primary sets the CMRR to max potential, referencing the floating winding to a physical ground. The key to getting the most performance out of the driver in front of the output trans primary is absolute symmetry from the op amp halves. I always recommend using the same dual op amp IC for the pos and neg driver elements to insure the same temp coefficient.
With transformers that have a single primary and secondary winding (not center tapped), the signal becomes single ended, but enjoys the same performance level of a balanced signal just by driving a transformer with another adjustable resistor referenced winding ground. This was my intention using the transformers I have, going into the amplifiers with separate floating grounds at each input.
Can you quantify that or could it be comfirmation bias? Or that the original opamps were fakes?
I used the board from CRM-Tech. The components aren't fake. I've tried other op-amps, including the original NE5534N from Phillips and also op-amps from Texas Instruments, and they all sounded the same. The Sparkos SS3601 was good, but the Burson Audio V7 Vivid Pro Single made it a completely different amp! There are no measurements, but my ears aren't deceiving me.
https://www.ebay.de/itm/40323871287...IkhxjHJTLq&var=&widget_ver=artemis&media=COPY
https://www.ebay.de/itm/40323871287...IkhxjHJTLq&var=&widget_ver=artemis&media=COPY
Except that ears are very deceiving when judging stuff. Should be a combination really.
Very often the stuff with most THD or that is totally not neutral is preferred when using only ears. That is why most of the recent opamps (that meanwhile have matured to very high performance) sound more or less the same today and the audiophile discrete stuff sounds significantly different. Different & audiophile tattooed & user naivety & high priced = business. Not long ago I witnessed someone adding discrete regulators by one of those brands and judging them by ear only. Of course only "Oh" and "Ah", lifted veils and blacker than black but it was not 100% right. They turned out to be oscillating when measuring them. So far for judging by ears 🙂
Very often the stuff with most THD or that is totally not neutral is preferred when using only ears. That is why most of the recent opamps (that meanwhile have matured to very high performance) sound more or less the same today and the audiophile discrete stuff sounds significantly different. Different & audiophile tattooed & user naivety & high priced = business. Not long ago I witnessed someone adding discrete regulators by one of those brands and judging them by ear only. Of course only "Oh" and "Ah", lifted veils and blacker than black but it was not 100% right. They turned out to be oscillating when measuring them. So far for judging by ears 🙂
OPA2156 is a good one.
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I'm 55 years old and built my first speakers (Visaton VIB) 41 years ago, and my first amplifier with the TDA7293 about 33 years ago. I've been to trade shows, have expensive equipment, and know what a good amplifier sounds like. I've been listening to this amplifier for over a month, and I don't hear any increased distortion! However, I do hear the poorly resolved highs, the tighter, more opaque room, and the soft bass reproduction of the Naim. The Naim may be a bit more controlled at very high volumes, but overall, it completely fades and is more inharmonic than the TDA7293 amplifier with the Burson V7.
I use an Eversolo DMP-A6 Master Edition with an LHY linear power supply as my source device, and Elac Vela BS 404.2 speakers, Monacor full-range drivers, Visaton Solo, and Sonoro Orchestra Slim as my speakers.
The result was the same even with a different DAC (Fosi ZD3)!
I use an Eversolo DMP-A6 Master Edition with an LHY linear power supply as my source device, and Elac Vela BS 404.2 speakers, Monacor full-range drivers, Visaton Solo, and Sonoro Orchestra Slim as my speakers.
The result was the same even with a different DAC (Fosi ZD3)!
Did you measure to verify? Otherwise it is assumption and not knowing. Audio voodoo so to speak.
An example:
An example:
I bought a Vivid V6 single opamp with my own money - definitely not a paid shill like many other Burson reviews I see!
I've measured its distortion performance using the QA403 audio analyzer and here are the graphs, first distortion v. level for both inverting (gain=-1) and non-inverting (gain=+1) topologies:
Clearly this opamp has decent (but not world class) distortion performance. Powered at +/-15V. 600 ohms load seems to be handled in its stride.
Alas the power consumption is a massive 13mA with no signal (the only pitiable specimen of a datasheet I could find claimed...
I've measured its distortion performance using the QA403 audio analyzer and here are the graphs, first distortion v. level for both inverting (gain=-1) and non-inverting (gain=+1) topologies:
Clearly this opamp has decent (but not world class) distortion performance. Powered at +/-15V. 600 ohms load seems to be handled in its stride.
Alas the power consumption is a massive 13mA with no signal (the only pitiable specimen of a datasheet I could find claimed...
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No, what for... Everything's working perfectly.
I don't even have the circuitry for this board!
This board cost me €41. It was a coincidence that I put the Burson Audio OPs on it! But now they're staying put.
It is the V7 vivid pro single not a V6
I don't even have the circuitry for this board!
This board cost me €41. It was a coincidence that I put the Burson Audio OPs on it! But now they're staying put.
It is the V7 vivid pro single not a V6
It was not you that plugged in the contraptions?
Well forget it, it is thread pollution. Sorry folks.
Well forget it, it is thread pollution. Sorry folks.
Damit es keine Verwirrung gibt, einmal auf Deutsch für dich!
Ich habe verschiedenes Equipment, mehrere Paare Lautsprecher, mehrere Verstärker, DAC's und Netzwerkplayer! Ich habe sehr viel gegen gehört, der TDA7293 mit dem Burson V7 klingt m besten! Ich war selbst erstaunt, dass mein Naim da nicht mithalten kann.
Ich habe in meinem Leben so gut wie jedes OP- Amp gehört, aber noch keins, wie den Burson V7
Ich habe verschiedenes Equipment, mehrere Paare Lautsprecher, mehrere Verstärker, DAC's und Netzwerkplayer! Ich habe sehr viel gegen gehört, der TDA7293 mit dem Burson V7 klingt m besten! Ich war selbst erstaunt, dass mein Naim da nicht mithalten kann.
Ich habe in meinem Leben so gut wie jedes OP- Amp gehört, aber noch keins, wie den Burson V7
OP wants "Best OpAmp for driving 600 Ohm load". OPA1678 are CMOS and tolerate 600 Ohm but feel better with 2 kOhm. They are good but not as good as JFET input OPA1642.
OPA1678 seems to be the new standard opamp in Chinese audio as I see them a lot. Possibly a consequence from them being 72 Eurocent a piece which is even cheaper than audio workhorse NE5532.
OPA1678 seems to be the new standard opamp in Chinese audio as I see them a lot. Possibly a consequence from them being 72 Eurocent a piece which is even cheaper than audio workhorse NE5532.
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The first graph on the OPA1677 data sheet seems odd; it shows higher distortion for gain = -1 than +1, when you'd expect the reverse to be true.
@EC8010
Gain = -1 means noise gain = 2, so 2x the distortion vs gain = +1 with all other things equal. Generally, noise gain for inverting is always 1 higher than signal gain.
Its only for an increased CM distortion that non-inverting gain can come out worse than the same signal gain in inverting mode.
Gain = -1 means noise gain = 2, so 2x the distortion vs gain = +1 with all other things equal. Generally, noise gain for inverting is always 1 higher than signal gain.
Its only for an increased CM distortion that non-inverting gain can come out worse than the same signal gain in inverting mode.
It is easy to parallel them to get higher current out. But driving a transformer even a single will be much better the the trafo.
I thought cheap was important.
I use mostly OPA1656 but it is not good in driving unlinear load. I am going to compare it with a voltage follover output OP and see if the old OP:s can drive output transistors better. I dont know but maybe an unloaded transformer can be a problem for the rail to rail output OP:s being an inductive load.
I thought cheap was important.
I use mostly OPA1656 but it is not good in driving unlinear load. I am going to compare it with a voltage follover output OP and see if the old OP:s can drive output transistors better. I dont know but maybe an unloaded transformer can be a problem for the rail to rail output OP:s being an inductive load.