It is a classic designing of final amplifier 35 W, with two EL34 in push-pull, from the Siemens and Halske.
http://users.otenet.gr/~athsam/Power_amplifier_EL34.htm
Bruce project, is a EL84/6BQ5 Push-Pull Tube Amplifier. The driver stage is an SRPP with ECC802S tubes, while ultra linear operation is used for the output stage with Sovtek EL84 tubes. LM317 Regulators are used for constant current sources CCS of the output stages. 12VDC is used for the tube heaters.
http://diyaudioprojects.com/Tubes/EL84-Push-Pull/
The tube for the input section is the double triode ECC88 or 6DJ8. Better versions are the E88CC, CCa or 6922 or even with less noise the E188CC or 7308. There are many brands NOS and from current productions available. I have good experience with Philips ECC88 NOS and JAN-Philips 6922.
http://headwize.com/projects/showfile.php?file=ahammer2_prj.htm
The topology of the amp is a simple grounded cathode gain stage coupled through a capacitor to an opamp wired in unity gain mode. The standard SOHA uses LND150 depletion mode MOSFETs for the CCS for reasons discussed below. The amplifier circuit is, thus, very simple.
http://headwize.com/projects/cavalli2_prj.php
JT-11P-1 Balanced Tube Line Input Stage.
http://www.jensen-transformers.com/as/as088.pdf
The point of star grounding is to keep signal circuits with NO common mode noise rejection (that is, all the normally used tube gain stages) from picking up current-induced noise from other currents running through a shared ground. Obviously, the most critical stage is an input stage, and the closer you go to the output stage, the bigger the signal level and the less the milli- and micro-volt signals in the shared ground will be.
http://www.geofex.com/Article_Folders/stargnd/stargnd.htm
The single tube configuration is the longing of any audio designer, and here we could have only one tube per channel. If we have only one tube on the signal the distortion spectrum will be a perfect decay on all harmonics, so it sounds very natural.
http://headwize.com/projects/showfile.php?file=ciuff4_prj.htm
The tube or the power transistor is loaded directly by the speaker (often thru a transformer, fro impedance matching!), and is biaised at the current necessary for full modulation (that means a maximum power dissipation for no input signal).
http://www.recherche.enac.fr/~puechmor/e_aclass.html
The need for a high-gain stereo preamp has diminished, because the CD has replaced the LP record in most audiophile homes.
http://headwize.com/projects/showfile.php?file=barbour_prj.htm
Preamp with Relay-Based Input and Power Switching
http://headwize.com/projects/showfile.php?file=ahammer1_prj.htm