Unity-gain "amp" for high-efficiency speakers

[U230421]

I believe the calculator assumes that Vmin would be negative 5.7v, i.e., Vmax is half of Vpp.

Wrong assumption by the calculator. There is no negative 5.7V. Calculators are not to believe in.

See attached.

The output is approx 6Vtt -> 3Vt -> 2Vrms.

 

[mudihan]

Thanks all. I built an amp with OPA548 at unity (i.e., connecting output to inverting input), and although the sound was good, it was not loud enough for classical solo music (i.e., no loudness war there). My room is about 18' by 26' and 10', and the speakers a bout 15' away from me. I think I may need 2x to 5x voltage gain.

 

[U230421]

Try a bridge (#8) first, twice the voltage swing, four times the power (if current reservoir is sufficient).

 

[indra1]

Or configure the OPA548 to give desired gain using appropriate feedback.

 

[Rodeodave]

The First Watt F4 is just that, a power buffer. Check out the manual for a full schematic:
FIRST WATT

PCBs and Mosfets are available from the diyaudiostore.

 

[marconi118]

Try a bridge (#8) first, twice the voltage swing, four times the power (if current reservoir is sufficient).

To do a bridge you need an inverted phase with an additional inverter buffer

If your DAC has symmetric balanced outputs 2x 2vrms you are good to go.

 

[mudihan]

To do a bridge you need an inverted phase with an additional inverter buffer

If your DAC has symmetric balanced outputs 2x 2vrms you are good to go.

Unfortunately it's just plain singled-ended 2vrms.

 

[xrk971]

Thanks all. I built an amp with OPA548 at unity (i.e., connecting output to inverting input), and although the sound was good, it was not loud enough for classical solo music (i.e., no loudness war there). My room is about 18' by 26' and 10', and the speakers a bout 15' away from me. I think I may need 2x to 5x voltage gain.

Since you are looking for some gain, and given all the Class A suggestions by other folks, you should look at Diegomj’a DLH amp. Really a superb sounding amp. I actually built it based on his schematic before he even tested it. It has about 12w and a superb harmonic distortion profile that’s adjustable for relative H2/H3.

Really simple and few parts too.

There are Gerbers and iron on transfer PDFs available.

Here was my home etched version using a Sharpie for acid resist:

The Sharpie etch worked so well I had to do a proper iron on transfer etch:

But look at the measurement at 2.83v: