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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.


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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.


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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.