If you're "tube curious," how do you make sense of the options? Should you get a single-ended or push-pull tube amp? This video features two tube amplifiers: the DG-SE1, a single-ended amp built on the Magnavox 8600-series chassis, and the BV-6V6, a push-pull amp built on the Magnavox AMP 175 chassis. I briefly discuss the songs I use to test these amps for sound quality: "Baby I'ma Want You" by Bread, "Chuck E's in Love" by Rickie Lee Jones, "Enter Sandman" by Metallica, the final movement of Tchaikovsky's Symphony No. 4 in F minor, "Peel the Paint" by Gentle Giant, "Little Fury Things" by Dinosaur Jr., and "Pinball Wizard" by The Who.
Note: At 37:00, I slightly misspoke when describing the modification to the Bevois Valley circuit for use with 6V6GT output tubes. The original design uses EL84/6BQ5 tubes for the output stage, and the EL84 has more gain than the 6V6. To get a large enough signal from the input stage (E88CC) to drive the 6V6 to full power at less than 2 Vrms input level, I had to reduce the amount of global negative feedback, and that reduction had a measurable effect on the level at which the lowest bass frequencies distort. It's partly a 6V6 problem; I've noticed these tubes tend to distort more than EL84's at low frequencies. It's partly an output transformer problem; at low frequencies, these Harman Kardon transformers saturate and distort at levels short of full power. The same is true for the output transformers on the single-ended amp, and this is a common problem with tube amps that don't have "big iron" on the outputs. (It's "the bass problem.")
00:00 Lancaster Hi-Fi Intro
01:56 The Amps and Test Tracks
07:52 Listening Tests
24:44 One More Test
29:36 Discussion of Test Results and Amps
37:52 Roll Credits!
