Tag: 01a preamp gen2

01a Preamp Gen2 finished!

01a preamp gen2 finishedFirst build of 2015, just after the New Year. I’m pleased to listen to the 01a preamp gen2 finished. It’s a beauty, only the warm sound of the 01a thoriated tungsten filaments can provide. A perfect match to the Starlight CD player that was lacking of a bit of gain.

It’s dead quiet, the frequency response is superb and the dynamics are there. Very good bass that improves what I was getting out of the discrete DAC. I love listening to this preamp. A great pleasure. Thumbs up to the return of the 01a. My best Sylvania globe valves are now in use, yay!

Will soon write a proper blog entry for this ultimate preamp.

 

01a Preamp: Build (Part 5)

Finished the preamp build yesterday, still have one power supply to build though. That is the benefit of the Christmas holidays as you have some proper time to work on your projects.

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Magically this time all worked fine from start. The preamp measures really well using the noisy bench power supply:

01a Preamp test 2 FR

As expected the HF response is really good thanks to the design of this stage. The -3dB pole is above 100kHz. LF response is actually better than the shown above as the soundcard LF pole is playing as well.

From a distortion point of view the preamp is performing well at maximum level which the Starlight discrete DAC will be playing at (i.e. 400mV):

01a Preamp test 4 THD vs FR

01a Preamp Test 4

The nice decay of harmonics is characteristic of this fantastic DHT.

 

 

01a Preamp Gen2: Build (Part 3)

The preamp build is progressing, albeit slowly.  I tried a new breadboard construction approach. A nice Ikea chopping board was used to build the front and back wooden panels. A pair of aluminium squared section rails are used to provide support and hold a pair of top plates for the power and audio connectors. As a bonus given the low power consumption of the filaments, I will use these rails as the heat sink for the Rod Coleman filament regulators as well 🙂

All in a very compact design as I literally ran out of space for further equipment in my living room!

01a Preamp Gen2: Build (Part 2)

Spent this afternoon building a compact modular base for the UX-4 sockets, a custom tag strip and the filament bias resistor array. Given the very low power dissipation on the filament resistors they can be placed below the valve socket board to minimise space. The actual size of resistors is a killer, but I have a stock of these lovely wire-wound ones:

Also the gyrator boards were mounted on top of the output teflon capacitors, again to minimise space. The trimpots to set the anode voltage are located at the top for handy adjustment if necessary: