{"id":1786,"date":"2013-08-11T17:38:05","date_gmt":"2013-08-11T16:38:05","guid":{"rendered":"http:\/\/www.bartola.co.uk\/valves\/?p=1786"},"modified":"2013-08-11T18:25:10","modified_gmt":"2013-08-11T17:25:10","slug":"4-65a-se-amp-testing-it-finally","status":"publish","type":"post","link":"https:\/\/www.bartola.co.uk\/valves\/2013\/08\/11\/4-65a-se-amp-testing-it-finally\/","title":{"rendered":"4-65a SE Amp: testing it finally!"},"content":{"rendered":"

The much-awaited moment finally arrived. After yesterday’s driver tests, I did a lot of work this morning to assemble cables and test the output stage. What I clearly know now is that I won’t be needing any heating this winter! What on earth was on my mind when I decided to build this amp? God only knows…<\/p>\n

Here are some pictures of the first tests in the workshop and then when I hooked it up to my system downstairs in the sitting room:<\/p>\n

\"26 <\/a>
26 preamp and 4-65a SE Amp just before testing <\/div> <\/div> <\/div> <\/div>
\"Burning <\/a>
Burning in the 4-65a! <\/div> <\/div> <\/div>
\"Setting <\/a>
Setting output bias <\/div> <\/div> <\/div>
\"Measuring <\/a>
Measuring output <\/div> <\/div> <\/div> <\/div> <\/div>\n

I did a quick measurement of the output THD without burning in the 4-65a or the amp. The operating point is not optimised but clearly shows a nice picture. First of all, the amp is absolutely quiet. The Rod Coleman regulators plus the extensive filtering on all supplies (LCLC and CLCLC) make this the quietest amp I’ve ever made! The distortion is higher than predicted. With the valves at 100mA\/540V and with a non-inductive resistor load of 10\u03a9, the THD is about 2.7% for nearly 6W of pure class A power. Only 4% of the harmonic content is H3 and with a nice H2 component. The footprint of an SE amp is clearly on this amp.<\/p>\n

\"4-65a<\/a><\/p>\n

Hooked it downstairs and after a lot of wiring I finally got to play some good records on this amp. I used my 26 DHT preamp. First record to be played was “a love supreme” (John Coltrane). Here are my impressions so far:<\/p>\n