New build for 2019
- Thread starter Tleung
- Start date
Waiting anxiously to hear your report Tony. Magnificent looking build!
Well the amp had been singing for the whole evening. I had to say I am impress with the sound. With out burn in the bass is deep but a bit loose and the high can be a bit more extend. Over all I like it a lot. It is not the same type of sound that coming from DHT like 300B and 2A3, DHT more airy and like looking at a picture. EL84 amp is more meaty with blood and sweat I felt like I am in the music. I selected few of
the components to give me faster responds and it pay off. @billfort you need to test it with your setup.
This amp actual post some challenge to my building skill. I learn that if the NFB is in phase with your first stage you will get a loud surprise. When I first measure the amp everything seem within range. I did not even bother hooking it up to the scope. when I connect it to the speak and turn it on I got loud oscillation. I do not use NFB much so I try to trouble shoot the amp and put it up on the scope and found that I end up with a PFB instead. I am not sure what cause it but I just reverse the B+ and plate wire on the Primary on the OPT and everything is fine.
I also adjust the B+ by adding a little bit more resistance at the first dropping resistor. I also added 2 x 100R resistor at the Filament terminal and created a center tap and ground it to reduce the hum. All and all I am very happy the result. Next mod will be adding a toggle switch to select between UL and Pentode. I am using a pairof JJ EL84 and a pair of Svetlana 12AX7. Well burn in had began.
I will report back after 50 hours
the components to give me faster responds and it pay off. @billfort you need to test it with your setup.
This amp actual post some challenge to my building skill. I learn that if the NFB is in phase with your first stage you will get a loud surprise. When I first measure the amp everything seem within range. I did not even bother hooking it up to the scope. when I connect it to the speak and turn it on I got loud oscillation. I do not use NFB much so I try to trouble shoot the amp and put it up on the scope and found that I end up with a PFB instead. I am not sure what cause it but I just reverse the B+ and plate wire on the Primary on the OPT and everything is fine.
I also adjust the B+ by adding a little bit more resistance at the first dropping resistor. I also added 2 x 100R resistor at the Filament terminal and created a center tap and ground it to reduce the hum. All and all I am very happy the result. Next mod will be adding a toggle switch to select between UL and Pentode. I am using a pairof JJ EL84 and a pair of Svetlana 12AX7. Well burn in had began.
I will report back after 50 hours
Nice looking amp ! IIRC, IMO, FWIW, when I was messing with EL84s the JJ had a bit of a soft top end compared with other choices. It wasn't bad by any means, just had its own character.
Thanks everyone for the kind word. Thank you @airdronian for the info of JJ El84. I am going to order a pair of Gold Lion once the amp settle down.
The post of your amp is inspiring me to haul out "The Silvertone" (EL84 SEP) today, it hasn't been run in a long time.
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