Re: Keeping your OPampTIONS open.......
wouldn't that depend on how you define those classes? To me, a class B is a circuitry that conducts 180 degrees, and class C <180 degrees. Class AB to me is one that is originally class A for small signals but gets pushed into class B under load.
So from that perspective, pretty much all op amps have a class B stage.
Fred Dieckmann said:
wouldn't that depend on how you define those classes? To me, a class B is a circuitry that conducts 180 degrees, and class C <180 degrees. Class AB to me is one that is originally class A for small signals but gets pushed into class B under load.
So from that perspective, pretty much all op amps have a class B stage.
traderbam said:
Well, the whole "Chip amps" section is full of it...
I use OPA548, most people use LM3886. The LM3886 was used in the $$$ 47Labs "Gaincard" amp and I hear that this one is also used in some high class SS (either Krell or Levinson) equipment.
Power wise the chips go up to 50 Watts (3886, a bit less for 548) into 8 Ohms, performance wise many people rave about them though many implementation philosophies exist - and are being fought over
. Very low DC offset. Proper bypassing and excellent PSU are very important of course, when done properly stability seems to be very good although I had my issues with PSU wiring. Never drive them into clipping 
. Sound better with higher Z loads (e.g. driving woofers in series rather than parallel for 16 Ohms rather than 4). Distortion figures from datasheets are around 0.01% at 1 kHz at 20W output. Open loop gains around 40 dB at 20 kHz. Slew rate around 10 v/us. Overshoot starting at 2 nF load capacitance.Of course these are all wicked data sheet data
Since the power is somehow limited they make most sense in biamped systems. I use them in biamped dipoles after the EQ section. To me they are great and beat my previous Rotel. But I can't make any fair comparisons because the system is so customized and partly hard wired that I can't easily throw in a standard amp for comparison.
Anecdotally - I used one OPA548 to drive gheadphones in Mono . This was just a test to see if it's working. PSU was the main 375VA (unregulated) supply with 22,000 uF caps. Oh so sweet the sound! Much sweeter than my OPA2134/BUF134 "regular" headphone amp.
Next day I repeat the experiment using the 12V regulated bench supply. Still OK but sounded somehow strained, and less dynamics.
Now what do I conlude - does one need a 375VA supply to drive the couple mW of my 250 Ohm headphones "properly"?? Do I need a 5 kW PSU to drive the speaker chips????
Hi ALW,
Interesting news about the 405. Do you happen to have any details about it? Perhaps we should discuss the design in a separate thread and get to the bottom of why it won a royal award for cleverness. Feedforward correction is a cunning idea...perhaps we can improve upon Quad's implementation as you imply.
BAM
Interesting news about the 405. Do you happen to have any details about it? Perhaps we should discuss the design in a separate thread and get to the bottom of why it won a royal award for cleverness. Feedforward correction is a cunning idea...perhaps we can improve upon Quad's implementation as you imply.
BAM
The Quad patent GB1499980 ceased a while back
CURRENT REGISTER DETAILS FOR GB1499980
Application No GB1499980
**** END OF CURRENT DETAILS ****
________________________________________________________________________________
RENEWALS DATA
Date Filed 14.01.1975
Date Not in Force 14.01.1990
Date of Last Renewal 04.01.1989
Year of Last Renewal 15
Date Next Renewal Due 14.01.1990
Status CEASED
CURRENT REGISTER DETAILS FOR GB1499980
Application No GB1499980
**** END OF CURRENT DETAILS ****
________________________________________________________________________________
RENEWALS DATA
Date Filed 14.01.1975
Date Not in Force 14.01.1990
Date of Last Renewal 04.01.1989
Year of Last Renewal 15
Date Next Renewal Due 14.01.1990
Status CEASED
It was annoying me too..
the trick came when I found a US patent for a feedforward design that referred to an earlier UK patent. That UK patent was the Quad one... Filed under "acoustical mfg ltd"
.
What I'd really like to see the patent search engine add is a "show me all the patents that cite this patent as prior art". That would be an interesting reearch tool!
the trick came when I found a US patent for a feedforward design that referred to an earlier UK patent. That UK patent was the Quad one... Filed under "acoustical mfg ltd"
.What I'd really like to see the patent search engine add is a "show me all the patents that cite this patent as prior art". That would be an interesting reearch tool!
People often come a cropper when using several caps in parallel, these three links show how it can go badly wrong and why:
http://www.ultracad.com/mentor/esr and bypass caps.pdf
www.electrical-integrity.com/Paper_download_files/xc_sun49.pdf
www.kennethkuhn.com/electronics/capacitor_z.xls
The last one really needs to be extended to 8 or more for a wideband low impedance source.
http://www.ultracad.com/mentor/esr and bypass caps.pdf
www.electrical-integrity.com/Paper_download_files/xc_sun49.pdf
www.kennethkuhn.com/electronics/capacitor_z.xls
The last one really needs to be extended to 8 or more for a wideband low impedance source.
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