Have you ever had a tube where the socket was low so the tube poked thru the lid of the amp with the metal top plate about a third of the way up the glass of the tube? Did it cause you grief? I believe it is ruining the day of a D3a on my 300B SET amp. I grew tired of looking at the mickey moused wiring and other "features" of my beloved amp so I made a new circuit board but the D3a sockets were not as tall as the previous board and I think it is causing some weird noise. Anyone else ever have this happen?
Jeff
Jeff
I am getting a SHHHHHHH sound in one channel. My old board didn't have anything that the new board doesn't have. The grounds are different is all. Old board was a 2 layer with a pour on each side tied to ground. The new board is a 4 layer with 2 solid ground planes in the middle. I am thinking it must be the way the grounds are connected. This amp was the quietest 300B set amp I have EVER seen. With La scala speakers at 106spl you could not tell it was turned on until the music started. I am going to unhook the connection to the ground planes and run individual wires from each ground point. There isnt that many. And see what happens. I have tried to put different board layouts in this amp 3 times and every time I ran into problems and went back to the original. Which is far from ideal but somehow dead silent. I just dont get it... what could I add on real quick to squash any d3a oscillations?
Also I design circuit boards for a living. Not saying that makes me immune to errors ( god knows that isnt true) but I avoid the big ones.. this has me frustrated beyond words..
Also I design circuit boards for a living. Not saying that makes me immune to errors ( god knows that isnt true) but I avoid the big ones.. this has me frustrated beyond words..
Can you post some pictures of the boards? Maybe you were just lucky with the first one? Here is a post with a quite complex dealing with the D3a (last post in that thread, by Shane.)
https://www.audioasylum.com/cgi/vt.mpl?f=tubediy&m=242822
https://www.audioasylum.com/cgi/vt.mpl?f=tubediy&m=242822
Here is the board that worked and the one that doesn't. The heaters on the D3a are ac and the 300B has a pair of tent labs filament boards on the heaters. The amp was dead silent with the good board. I have a batch of the good board on its way to me and I also have some of the pic marked future boards. I got rid of the ground planes and changed the grounding to the scheme shown. No idea if it will fix it but i at least have the good boards on the way as well so I can always put it back to the way it was if I have to. The problem board has 2 inner ground planes and the connection is made to the power supply by the 2 connectors at the top of the board straddling the center screw.
Attachments
Here is some information about grid stopper, grid leak etc. They write about values over 15k, I think that is.for guitar amplifiers (bandwidth limit??), for Hifi and the D3a something between 100R and 1k will do. Try 1k, if it helped, you can go lower. https://www.emprizeamps.com/post_resistors.html
I thought I would circle back and tell how everything turned out.
To recap I built my amp about 5 years ago. A SET 300B amp with all Lundahl iron, Duelund cast copper caps, Tantalum resistors an autoformer volume control, All film cap power supply. It was dead silent and sounds amazing. ( I fear I am emotionally involved with it.) Well A few things in the build were never meant to be permanent and thus were a bit hokey to be kind. So I had some new pcbs made to hold the heat sinks and generally take care of the crap. Make it look more like it sounds.
So I get the boards and put one in and I had this weird oscillation in one channel. ( I now believe had I resoldered all the connections and dialed in a few things I could have fixed it). I fought with it for a few days and wrote on here to try and figure it out. So finally I say screw it and ordered more of the original board since the previous one was worse for wear. The board comes. I find a cool way to support the heat sinks and wire everything up satisfactorily.
I flip the switch and only have heat in one 300B.
Tear it back out of my system ( all 45 pounds of it.) I look around and can't see anything obvious. I remove the tubes and fire it up and the voltages are identical both channels and everything apprears to be working. Re-assemble..
Flip switch... tube still dead, no heat. switch tubes... no change...
Tear it back out of my system. ( still 45 pounds).
I swap heater boards thinking this will tell me for sure one way or the other whats wrong. Fire it up and the opposite heater is dead. I feel really smart and go order a heater board.
An hour later I remembered I have 2 of those boards SOMEWHERE in all my stuff. fast forward 7 hours later going thru boxes. I give up on it and then an hour later my friend who kept looking found them..
So I grab a socket and my power supply and test the boards as I remember one of them possibly being bad. first one started right up and I was able to dial in 5 volts. Second board I could not get to adjust below 7. Not sure why. I grab the one that I set to 5 and install it. Hook my amp back up and flip the switch.....
The other tubes heater won't light........................................
Ok enough of this crap. I remove the screw terminal blocks on the heater boards and solder the wires directly into the board. Remelt all the solder joints.
re-assemble and install it..
flip the switch and my gloriously awesome 300B set amp is back in business!!........
Be a cold day in hell before I mess with it again... ;-)
Jeff
ps. But I really love this thing. With 106db spl speakers you can't tell it's turned on until music plays. Its got this punchy transparent sound with beautiful tone that just makes me smile even though I have had it for 5 years. Biggest single improvement was the volume controls. Intact Autoformers. It was like 2 bed sheets vanished from over my speakers.
DIY 300B set amp, VPI Ares XL TT,Tube SE Phono amp, Dnyavector cartridge. Directstream DAC, La Scala Speakers.
To recap I built my amp about 5 years ago. A SET 300B amp with all Lundahl iron, Duelund cast copper caps, Tantalum resistors an autoformer volume control, All film cap power supply. It was dead silent and sounds amazing. ( I fear I am emotionally involved with it.) Well A few things in the build were never meant to be permanent and thus were a bit hokey to be kind. So I had some new pcbs made to hold the heat sinks and generally take care of the crap. Make it look more like it sounds.
So I get the boards and put one in and I had this weird oscillation in one channel. ( I now believe had I resoldered all the connections and dialed in a few things I could have fixed it). I fought with it for a few days and wrote on here to try and figure it out. So finally I say screw it and ordered more of the original board since the previous one was worse for wear. The board comes. I find a cool way to support the heat sinks and wire everything up satisfactorily.
I flip the switch and only have heat in one 300B.
Tear it back out of my system ( all 45 pounds of it.) I look around and can't see anything obvious. I remove the tubes and fire it up and the voltages are identical both channels and everything apprears to be working. Re-assemble..
Flip switch... tube still dead, no heat. switch tubes... no change...
Tear it back out of my system. ( still 45 pounds).
I swap heater boards thinking this will tell me for sure one way or the other whats wrong. Fire it up and the opposite heater is dead. I feel really smart and go order a heater board.
An hour later I remembered I have 2 of those boards SOMEWHERE in all my stuff. fast forward 7 hours later going thru boxes. I give up on it and then an hour later my friend who kept looking found them..
So I grab a socket and my power supply and test the boards as I remember one of them possibly being bad. first one started right up and I was able to dial in 5 volts. Second board I could not get to adjust below 7. Not sure why. I grab the one that I set to 5 and install it. Hook my amp back up and flip the switch.....
The other tubes heater won't light........................................
Ok enough of this crap. I remove the screw terminal blocks on the heater boards and solder the wires directly into the board. Remelt all the solder joints.
re-assemble and install it..
flip the switch and my gloriously awesome 300B set amp is back in business!!........
Be a cold day in hell before I mess with it again... ;-)
Jeff
ps. But I really love this thing. With 106db spl speakers you can't tell it's turned on until music plays. Its got this punchy transparent sound with beautiful tone that just makes me smile even though I have had it for 5 years. Biggest single improvement was the volume controls. Intact Autoformers. It was like 2 bed sheets vanished from over my speakers.
DIY 300B set amp, VPI Ares XL TT,Tube SE Phono amp, Dnyavector cartridge. Directstream DAC, La Scala Speakers.
