• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

4P1L push pull amp with Lundahl zero global feedback

Hi all,
I am happy to present my latest incarnation of a push-pull amplifier with the amazingly linear Russian pentode 4P1L. It uses Rod Coleman's regulators for the filaments of 4P1L. The final stage is pushpull parallel 4P1L driven through a LL1660/10mA Alt"V" by the 6H30P-EB. The amplifier measures a THD of 0.2% at 6.7W. Total gain is 17dB (X7.3). The sound is amazing, somewhere between SE and PP.
Best,
Radu
 

Attachments

  • IMG_0736.jpg
    IMG_0736.jpg
    427.5 KB · Views: 1,167
  • DSC00411.jpg
    DSC00411.jpg
    979.5 KB · Views: 1,080
HI Pano,
Here are the schematics. Nothing unusual. Also, top plate is anodized aluminum 3mm gold CNCed by ProtoPanel.com. Cabinet is mahogany all sides and birch ply 1/2" bottom with more than 300 holes for heat management. More info at simplepleasuretubeamp.com. Thank you for your words of appreciation.
 

Attachments

  • Sch_1.jpg
    Sch_1.jpg
    338.2 KB · Views: 1,140
  • Sch_2.jpg
    Sch_2.jpg
    362.2 KB · Views: 1,084
I guess I could if you imply using them in UL connection class AB. Actualy when I bought the OTs I was thinking of building a classic pushpull with 6P3s and I tried it but in the end I liked better the sound of triode strapped 4P1L. I guess it is just a matter of taste. I know that there is a lot of power wasted this way, but I couldnt help it. This is my first amp, and I aimed for simple, 2 stages, transparent sound.