300B Hum

[BOONDI]

Originally Posted by NickG

I may be missing someting in that diag, AFAIKS the only thing that the balanced operation will give is the ability to have a phase change switch.

The input is single ended, and uses a LTP to produce the antiphase signal (the fuse in the grid circuit looks odd). I don't know if there is any result of the shared cathodes where the other half of the signal is eventually unused.

Hi Nick, Ian...all.

Nick, have to agree about balanced operation, and it seems to me that the switch is already on the drawing. I think this will give phase reversal depending on switch position.
Also, dont see the point of the fuse because a short inside the valve will (both triodes inside same valve) basically still be able to find earth thru the power supply line or heater anyway. if the grid goes down will the triode now behave like a diode? Or a straight short over the triode with the fuse in may well blow the fuse but still leave the current to flow thru the shorted section....

Seems over blown to me to have twin phase splitter with push pull output for a phono stage, well that's what it looks like to me.....Doesn't help that I have to hold my head at 90 degrees as my new version of Acrobat reader can't rotate the page.....

Ian, I owned a KEL34 that was basically the first one that shipped when WAD introduced the upgraded EI core Tx's and kit of parts. When it shipped it came with the wrong pcb and errors in the instructions. As dissapointed as I was when I fired it up and caps started to pop and etc. I have to say that after a telephone call to WAD the problems were rectified with me being talked through the rebuild and testing over the phone. After the initial problems, I have to say that my KEL gave me sterling service for 5 years and had no problems whatsoever. I think you may have been unlucky and have bought some of the less well built versions of WAD kit. I.E. not built by people that have vast knowledge of kit building/negligible soldering or mechanical skills etc. The kits themselves were quite good, well thought out and excellent value for money IMHO. The new W-D kt 88 looks well tasty and Peter should be congratulated for his recent acheivments. I remember a conversation on the old forum where some of the members were talking about buying the WAD stock on the cheap as part of a members buy-out. However, Peter went out on a limb and salvaged the kits that remained and was brave enough to re-market them under the W-D brand. If they were truely **** then the WAD kits would have disappeared without trace and we would be homeless.

P.S Ian don't worry, I agree with you about amature builders and idiot upgraders, but for me, the worst are the phantom dabblers.....They are the people who know nothing and tamper inside tv's and etc. often turning a simple fault hunt into a mammoth job. Eventually when you figure this out and question them on what they did to the circuit, whey still deny it and refuse to admit they turned this pot up or screwed that tunning slug down etc.etc.etc

Regards....

Hello to everyone: interesting how one question can generate so much passion and knowledge. If I could, momentarily, drag it back to my problem, I'm pleased to say that it seems to be fixed. I re-soldered some of the signal wires and it's now a tad quieter than before!
For the record, I am one of those complete amateurs who knows nothing of electronics and who, on balance, perhaps should not have attempted to build these amps as a first project. I did so because the 300B PSE was the only amp I auditioned (that I could just abut afford) that provided the sound for which I had long sought. I mention this only as some kind of explanation as to why some of us did this despite natural misgivings. Once they were working well I just sat back and smiled. I doubt I hear them at their best using my old Audiolab 8000A as a pre-amp, but they still sound fine.
Thanks to everyone who helped.

[LGarfirth]

Hear hear Jeff. I love mine too !! and I didn't have a clue either. What I really like is when friends come round and comment - I just sit back and say.

I made those, good arn't they ??