This the one with OPA547 outputs? Care to comment on the 547? I have a couple, curious how well they perform. I was originally gonna use them as inverting buffers following subminiature triodes as current buffers, but can't find any documantation as to them being unity-gain stable or not.
Yes, the HD-5 has the OPA547 as the output stage. It’s good for 5w into 32ohms. They sound very nice - basically clean and transparent as you would expect from top of the line power opamps from Burr Brown / TI. But I wonder how many people really need a 5w headphone amp? Seems only the certain low sensitivity (82dB per mW) HiFiman planars has a valid use case. The TPA6120 is superb for all other applications up to 2w.
I have built up a USB PC dual channel 18 mega samples scope.
The scope end uses a PIC32mx230 and software was fairly straight forward.
The PC end was the more difficult end with numerous options to program in.
As well analogue display it has a spectrum analyser display which uses Fast Fourier Transform to convert from time domain to frequency domain.
It took a while to find an FFT that worked well. Even then I had convert output data for my use.
Powered by USB bus and powered inverted to get minus 5 volts for op amps.
Uses an AD9201 10 bit a2d converter.
The scope end uses a PIC32mx230 and software was fairly straight forward.
The PC end was the more difficult end with numerous options to program in.
As well analogue display it has a spectrum analyser display which uses Fast Fourier Transform to convert from time domain to frequency domain.
It took a while to find an FFT that worked well. Even then I had convert output data for my use.
Powered by USB bus and powered inverted to get minus 5 volts for op amps.
Uses an AD9201 10 bit a2d converter.
As practice prior to my BTSB marathon, I decided to build up the headphone protect boards that have 0603 parts, etc…used hot air only for the smallest resistors, caps and SOT stuff (Q1-Q5). Doesn’t look too bad.
Best,
Anand.
Best,
Anand.
Nice looking boards! Have you tested them for operation yet?
Simple continuity meter check for signal in to out and apply power. They should have a delay then conduct close to 0ohms.
Simple continuity meter check for signal in to out and apply power. They should have a delay then conduct close to 0ohms.
X,
Thanks. No not yet. I am in BTSB mode now. It’s likely I’ll test the BTSB before I even check these!
Best,
Anand.
Thanks. No not yet. I am in BTSB mode now. It’s likely I’ll test the BTSB before I even check these!
Best,
Anand.
On the bench tonight is a new SE Class A JFET input MOSFET source follower preamp module for a new product under development for Vera-Fi Audio. The topology is similar to the DCA but uses an LSK389 for stereo and has a dual linear voltage regulator for each rail. DPAK output MOSFETs. I’m going to test it out as a basic headphone amp for high impedance headphones to check the sound.
Back when I used Grados I liked them, but I haven’t needed anything more than earbuds daily for years so got out of the headphone game.
I wonder if the 547 would do well for speakers at low power/nearfield?
Yes, they can work as speaker amps for higher impedance 16ohm speakers at low power. You could drive 8ohms probably at very modest powers.
One of the reviewers of the HD-2 headphone amp connected speakers to them. It worked so the TPA6120 can drive small speaker loads even.
I have a parallel 8x OPA6122 headphone amp that can drive 8ohm loads to 10w. Thread in headphones forum.
One of the reviewers of the HD-2 headphone amp connected speakers to them. It worked so the TPA6120 can drive small speaker loads even.
I have a parallel 8x OPA6122 headphone amp that can drive 8ohm loads to 10w. Thread in headphones forum.
do you perchance have a link - search is not being fruitful but i am intrigued by such a best 🙂
Sorry for the dyslexic typo. It’s opa1622.
https://www.diyaudio.com/community/...pa1688-low-thd-muscle-amp.324931/post-5817024
https://www.diyaudio.com/community/...pa1688-low-thd-muscle-amp.324931/post-5817024
It is unity gain stable. The data sheet page 7 shows the square wave response with G = 1.
Just biased the 12GT5 version of my mofular amp down to 35mA. It was set to 65mA but the pot was flaky and it would run at 93mA instead. I wondered why it smelled hot lol
Just built a two in two out speaker switch for the bench so I can switch between the house amp and the amp being tested, and speakers or dummy loads.
I am finally listening to this preamp board as a headphone amp. I forgot how wonderful the PCA/DCA circuit sounds - fantastic. Something so pure about music from a 2 transistor SE Class A circuit. The dual JFET has perfect channel balance as setpoints are spot on left and right. The two voltage regulators isolate the common power supply for a stiff rail giving excellent channel separation for great soundstage.
I am listening with Beyer DT-880 (250ohms), which with 22uF caps gives a -3dB corner of 30Hz - so the bass is surprisinlgy good. Replace the 22uF cap with a 1000uF cap and this would be a great headphone amp all by itself for 32ohm cans.
The ability to connect a basic 24v Meanwell wall-wart for a PSU is very convenient.
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