JoaMat

Here is an attempt to make a “smd raal uberamp driver”. I followed Kevin’s schematic. The big resistor is for feedback/gain, I guess 1.5 – 2 W is required and a few components on “solder” side. The real challenge will be the power sections. 3A x * +/-24V * 8 * balanced - might be a bit extreme for headphone amplifier…

Lately the left channel humming has increased to become even more bloody annoying. But… today I cured it (pure luck - trial and error approach). I have two umbilicals between psu and amplifier. Both carrying 580V bias and then joining at the stax connector. So, I removed left 580V bias wire in amplifier and the hum disappeared. To my ears the amplifier is now dead silent.

Aerial picture of opamp driver and psu. I had some disturbing noise from the Mean Wells. After putting them their own enclosure the noise reduced considerable but there still is audible noise. With AMB’s Sigma22 supply +/-29V the amplifier was noise free. I only tried sigma22 for a few minutes since it hasn’t the current capability as the Mean Well, but it sounded OK. As for sound I find it enjoyable to listen to but I also think it has some sonically drawbacks (maybe) due to the switching mode power supplies. Bottom line is that I agree with the designer

Milled a second board today and after some struggling I eventually have a stereo opamp driver. Now I listen to this and this… Grüner Veltliner for my father-in-law... he was born in Austria.

I might. Give me a ping.

Here is a (my) version of Kevin’s opamp RAAL driver. Board is kitchen made. Some parts are smd but schematic is same as original. Only one channel working and it’s powered by lab power supply max 3A. Occasional when playing, not very load , leds indicating max current hit are flickering. But I've two 340W Mean Well supplies at hand. Mouser don't sell them supplies to ordinary consumers in Europe so my wife bought them for me. Lucky me.

Did this tonight

LES SIÈCLES, FRANÇOIS-XAVIER ROTH Sur instruments d’époque / On period instruments

Anyone out there have built the raal opamp driver besides justin? I’m interesting and I guess other people are as well in the outcome and thoughts about the driver.

look - terminal blocks...

B - (((R8+R9+R10)/R7)-1)*Vref

To me it sounds that you built yourself a nice amplifier. Enjoy.