Hooo hoo.
10x apmification and 10 dB aplification is totally different.
If I'm right from google 10x amplification is 20dB.
Manual says 10x amplification, not dB.
10dB amplification is somewhere 5x amp.
What I found in google is that V amplification in dB is 20*log(Vout/Vin). Someone clarify this plz. So the dB increase is lot slower than the actual amplification you get from 1+Rf/R3.
When I managed to fry few caps I tested the chip with direct feedback meaning 1x amplification. It oscillated like hell. No cap could solve it. Inserted the R3, giving 10x amplification and oscillation gone. So too low amp will drive these chips to oscillation. Maybe it is still good with 5x or 7x. Manual says 10x is advised, but may be stable at lower also.
I seem to recall that this "stability" is for driving a resistive load.
If you are driving a reactive load then the stability margins are much reduced and poor sound is the likely outcome.
26dB to 30dB of chipamp amp gain results in much higher stability margins and from reports seems to be around the sweet spot for good sound quality.
10 times is +20dB
3 times is ~+10dB
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Thanks for chiming in AndrewT. Judging from the other threads on chip amps, you seem to know a good deal.
That higher gain stability is exactly what I'm afraid of when trying to combine a preamp with a chip. The idea seems to be supported by the measurements here. Daniel supplied a link to this website earlier in the thread and it's a very interesting read.
It seems that if I'm going to go with a GC, I'll need a buffer for the best SQ (of course the most suitable Aikido tube buffer for my application is on backorder). If I want to go with another Aikido preamp circuit, I'll need to find a more suitable power amp section (which will likely then prevent me from doing this 'all-in-one').
So I'm open to other buffer suggestions (tube preferred) or other power amp suggestions (low gain and either very small or cool-running so that it can be hidden in a cabinet). Anyone got ideas?
I have read that they aren't necessary in lots of places, but I've also read that there is some SQ benefit from a good buffer. Do you have any experience with a chip amp and buffer?
I'm not worried about whether my sources can drive it, I just want to squeeze the maximum performance out of the chip. Of course, chip amps do seem to follow the 'less is more' mantra.
That's what I was afraid of. The second/large enclosure requirement defeats the basic purpose of my build, which is a small, high performance, low cost, aesthetically pleasing integrated. So basically, this is a unicorn hunt.
Practically speaking (or maybe just picturesque). . .
Low gain unicorn: LM675 Check the datasheet example applications.
Or, there's two versions of TDA2030, but the datasheet for one of them is very full of active application examples, some of which show a lower gain.
Gain--it isn't for loud or quiet:
Gain is the primary means of stability compensation for chip amplifiers. It is impossible to adjust the gain without simultaneously adjusting the overall quality. That could be either good or bad. And there is the point. Rather than choosing louder or quieter, I think you should adjust for highest quality regardless of whether it may be too loud or too quiet. Yes, there will be an inconvenience.
Options for using the amp you have:
Non-inverting mode is for highest gain*
Inverting mode can do lower gain
T-Network Inverting mode can do lowest gain**
*Really bad idea to set non-inverting chip amp kit to very low gain, since that would also set the quality to minimum and the heat to maximum, plus a rather impractical tone.
**Anything that changes stability can make the gain requirement higher or lower.
Promoting stability by other means can reduce reliance on gain for comp:
A change to power supply voltage can alter how much gain there will be when the amplifier is dialed in to the sweet spot of just right compensation (much lower voltage can allow somewhat lower gain). Likewise, if layout and clean power are done to promote stability there is slightly less reliance on gain for promoting stability, thus a good design has the gain sweet spot a little bit lower. We don't arbitrarily set a gain figure--it is the amplifier that decides, so what we're really doing when dialing in the gain is discovering what the amplifier wants. And, like Murphey's law, when you get the gain set really precisely for best tone, best clarity, low heat, best impact and overall best performance, it is probable that the gain factor which results in best sound will also be very inconvenient and require either a voltage divider because it is too loud or a preamplifier because it is too quiet. This is the major difference between chip versus discrete--we could readjust supplementary compensation inside the discrete amp until the gain sweet spot is also a convenient figure, but we cannot adjust inside the chip amp which is sealed shut.
Adjusting the gain to find the sweet spot:
Personally I use a multi-turn cerment trimmer as a variable resistor for the Feedback-Shunt Resistor (not feedback resistor--don't put a dial there). If you set the gain too low the result is hot running with a baleful tone. If you set the gain too high the result is poor bass impact, a sort of gritty low resolution and very boring flat imaging. These two groups of problems are opposites--Setting the gain at the midpoint, sweet spot of just-right gain, will cancel both problems. The more precisely you can set this, the better.
Layout affects stability, so that changes in layout and cabling slightly alter the location of the gain/compensation sweet spot, and that is a moving target until the enclosure lid is bolted closed. See why I use the dial?
Here's a working method of finding out what the optimal gain setting will be before an amp is built: Build an identical amp beforehand.
Low gain unicorn: LM675 Check the datasheet example applications.
Or, there's two versions of TDA2030, but the datasheet for one of them is very full of active application examples, some of which show a lower gain.
Gain--it isn't for loud or quiet:
Gain is the primary means of stability compensation for chip amplifiers. It is impossible to adjust the gain without simultaneously adjusting the overall quality. That could be either good or bad. And there is the point. Rather than choosing louder or quieter, I think you should adjust for highest quality regardless of whether it may be too loud or too quiet. Yes, there will be an inconvenience.
Options for using the amp you have:
Non-inverting mode is for highest gain*
Inverting mode can do lower gain
T-Network Inverting mode can do lowest gain**
*Really bad idea to set non-inverting chip amp kit to very low gain, since that would also set the quality to minimum and the heat to maximum, plus a rather impractical tone.
**Anything that changes stability can make the gain requirement higher or lower.
Promoting stability by other means can reduce reliance on gain for comp:
A change to power supply voltage can alter how much gain there will be when the amplifier is dialed in to the sweet spot of just right compensation (much lower voltage can allow somewhat lower gain). Likewise, if layout and clean power are done to promote stability there is slightly less reliance on gain for promoting stability, thus a good design has the gain sweet spot a little bit lower. We don't arbitrarily set a gain figure--it is the amplifier that decides, so what we're really doing when dialing in the gain is discovering what the amplifier wants. And, like Murphey's law, when you get the gain set really precisely for best tone, best clarity, low heat, best impact and overall best performance, it is probable that the gain factor which results in best sound will also be very inconvenient and require either a voltage divider because it is too loud or a preamplifier because it is too quiet. This is the major difference between chip versus discrete--we could readjust supplementary compensation inside the discrete amp until the gain sweet spot is also a convenient figure, but we cannot adjust inside the chip amp which is sealed shut.
Adjusting the gain to find the sweet spot:
Personally I use a multi-turn cerment trimmer as a variable resistor for the Feedback-Shunt Resistor (not feedback resistor--don't put a dial there). If you set the gain too low the result is hot running with a baleful tone. If you set the gain too high the result is poor bass impact, a sort of gritty low resolution and very boring flat imaging. These two groups of problems are opposites--Setting the gain at the midpoint, sweet spot of just-right gain, will cancel both problems. The more precisely you can set this, the better.
Layout affects stability, so that changes in layout and cabling slightly alter the location of the gain/compensation sweet spot, and that is a moving target until the enclosure lid is bolted closed. See why I use the dial?
Here's a working method of finding out what the optimal gain setting will be before an amp is built: Build an identical amp beforehand.
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