Class G with LM1875?

[danielwritesbac]

You're going to create a lot of higher oder harmonics though. The might have the correct even/oddness, but they will be much higher order. As long as you can't hear up to 50KHz, like some people, it should be okay.

Do you suppose that we could install some small capacitive loads to decrease that problem?

 

[banana]

Although the TDA7294 is able for high fidelity, its not the nearly-automatic experience of LM1875.

I'm proposing utilizing the LM1875 as a "$2 hifi effects box," much like the "effects" of a vacuum tube pre. Yes, I'm proposing a cheat/shortcut, in hopes of a lot less "sound tweaking" of the finished product.

The LM1875 starts off with a good high fidelity baseline, which is measurable--not a confusing botique deal.

Do you know what I'm saying?
Its that the LM1875 is one of the rare cases where science and hifi have met. That's an awesome thing to make louder.

I'm not trying to diverge from your beloved LM1875
Just bring up an example of class H circuit.

 

[danielwritesbac]

I'm not trying to diverge from your beloved LM1875
Just bring up an example of class H circuit.

Which do you think would be more suitable? Class H or Class G?

For reference, 21vdc and nearby voltages are fidelity trouble for LM1875. So, something like 11 to 16vdc is good. . . or. . . 25 to 30vdc is good.

 

[tiltedhalo]

Class G

The supply range for the lm1875 is 16VDC to 60VDC, I think your best bet is a "down tracking converter" most switch modes can handle up to a 40% variance, just tack into the feed back loop for the voltage tracking modulating it with a voltage reference derived from the audio input. This could net you a 16 to 24VDC output swing from SMPS this should be fast enough, depending on the voltage divider circuit to track the audio.

 

[danielwritesbac]

Re: Class G

The supply range for the lm1875 is 16VDC to 60VDC, I think your best bet is a "down tracking converter" most switch modes can handle up to a 40% variance, just tack into the feed back loop for the voltage tracking modulating it with a voltage reference derived from the audio input. This could net you a 16 to 24VDC output swing from SMPS this should be fast enough, depending on the voltage divider circuit to track the audio.

Problem. 16 to 24vdc is the area to avoid.

Problem. I understand the supply range to be 8vdc to 32vdc.

 

[danielwritesbac]

Class G midrange variance?

Problem. 16 to 24vdc is the area to avoid.

Solved! Add these into the bypass (power smoothing) system:
Nichicon ES 22uF (or 33uF) 50v (treat the long pin as +)
*In addition to the power supply circuit's smoothing.

Its probably an unnecessary concern with most SMPS; however, if it becomes necessary, the cost of the workaround is 48 cents, so the errata need not halt the project. This errata would behave as a "loudness contour" if it is present in Class G. The problem exists in many op amps--more or less "midrange" depending on power voltage. Fortunately, LM1875 does less midrange when its given less voltage--fortunate because its not backwards to common usage.

The LM1875 maximum voltage handling depends on the load, and I'd like to know if someone wants me to do extended length testing at a particular voltage vs load combination. I'd gladly do that.

One thing is for sure. The project won't be boring. Its a gamble on whether it would be great or poor; but, I think the results would be strongly apparent either way.