Something else only half related...I was looking at the datasheet for the UBT-1. I've never seen a more comprehensive datasheet for an output transformer.
UBT-1 Datasheet
UBT-1 Datasheet
Two things. Since I have an active subwoofer to augment the open baffles and they are supplied by the preamp. When you add a bypass cap the gain of the amplifier goes up....and the subwoofer is lagging way behind because the amp is so much louder...leaving one essentially with squaking midrange...I did compensate a little more vigourously this time as I realised it while thinking about the problem last night. And it just sounds great now! A little less tubey....(which is something aparently that I like) but more even handed for sure. I'll have to do some more listening...and will try the feedback again. I also feel that the 2000uF cap contributed somehow to the warmer sound (even without my subwoofer issue).
So in the end reason and logic wins. Now I'll get a single cap instead of my three paralled jobbies of sufficient value and rating. So Kay happy. Bas happy.
So in the end reason and logic wins. Now I'll get a single cap instead of my three paralled jobbies of sufficient value and rating. So Kay happy. Bas happy.
Yesterday I put my latest RH84 in service...I think anyone listening would prefer the RH84. So I'm sorry Francois. I'm going to try something else with the driver. Hope you haven't started beause of me. It's not a bad amp. It just got its *** whipped by 'David'
Hello
Here is my EAR 859. Sound fantastic.
https://rpaudio.estranky.sk/fotoalbum/ear-859-tube-amp-se/?photo=1
Here is my EAR 859. Sound fantastic.
https://rpaudio.estranky.sk/fotoalbum/ear-859-tube-amp-se/?photo=1
Thanks, Bas. 😁 Are gou starting a new thread about your adventures with ‘David’? I’ll wait for the dust to settle while I’m building my Fisher SA-100 clone. (https://audiokarma.org/forums/index.php?threads/teaser-pics-fisher-sa-100-clone-in-progress.466229/)
@platon.rado, that is a great-looking build of an EAR 859! Congratulations! How about a picture of the underbelly of the beast?
You know...I keep telling myself don't go posting every 5 minutes about the sound. Live with something for a couple of weeks or even months. Then come out out with a little snippet of what one thinks. This is still valid. Let me listen and compare some more. I'm sorry for being such a little bitch.
Hi
May some strange to post it here:
I have built bob danielacs version of enhanced EL509 amp
Firts i have a terrible humm on both channels.
furthermore its getting awfully hot: bias through driverstage is around 25mA, and EL509 around 100mA.
Adjusting the DC coupled amp doesnt alter the current in both stages, and the 200W stereo spply transformer gets hot too.
Any idea how to lower the (auto) bias current in AL509 output stage? Maybe it would be better to add preset bias schematic.
May some strange to post it here:
I have built bob danielacs version of enhanced EL509 amp
Firts i have a terrible humm on both channels.
furthermore its getting awfully hot: bias through driverstage is around 25mA, and EL509 around 100mA.
Adjusting the DC coupled amp doesnt alter the current in both stages, and the 200W stereo spply transformer gets hot too.
Any idea how to lower the (auto) bias current in AL509 output stage? Maybe it would be better to add preset bias schematic.
The currents you measured sound about right for the voltages and cathode resistors. SE amps are not very efficient.
Totally agreed! I also built one, with slight modifications, mainly in order to have the bias adjustment decoupled from the impact of gain. To be honest, this amplifier is of very poor efficiency, even in terms of SE designs. Didn't use it for a very long time.
Best regards!
Best regards!
As OldHector said. Those currents check out. But my power transformer stays cool. The humm could be many things I suppose. Do you have pictures?
