Kel84 - omg!

[kt66se]

Ordered me one of these a couple of months back and after a few email exchanges with Matthew I had a large box on my door step and on opening found within a beautiful KEL84 ready to be built.

I took my time as I also had house refurbishment to get on with as well but the whole process was a joy and the instruction manual a breeze to follow.

The quality of the kit, the components, instruction manual, packaging, materials, volume knob! are very high quality and everything fits and looks perfect.

I had a couple of problems, otherwise the amp would have worked first time, one of the Sonic caps was short cct and another when tapped produced a hissing sound plus the very odd voltages around the ECF80 tube but a reassuring email reply back from Matthew plus a pointer to this sites FAQ on the subject got me back on the right track. I did away with the Sonic caps and replaced them all with Jensens. I borrowed a friends sig gen and oscilloscope but after 10 mins of okay square and sine wave tests, I lost patients so tidied her up and connected a pair of newly purchased Monitor Audio Bronze speakers and wow - what a beautiful sounding amp, that's it for me, project complete, kick back listen and stare at the valve glow on my bookshelf (It's a big book shelf) - thanks WD for still producing this stuff and this forum of in-depth knowledge and hints which I've ploughed through (but missed the bit about the odd ECF80 voltages) - thought I was going mad on a stormy sat night bent over a hot iron and stares of dis-belief at my DVM

Adam

[John Caswell]

Hi Adam,
There was a lot of grief about the ECF80 in the KEL84 voltages as they seemed to vary wildly yet the amplifier performed exactly to spec.
I did a lot of work/tests on a great deal of ECF80/E80CF from various manufacturers and came to the conclusion that if the cathode voltages were within the ±10% range all was well with the amplifier.
The biggest problem nowadays with DMMs is that if the schematic says say 150V volts on the anode and 149V is measured, something is drastically wrong, which of course is not the case as you and many others have found out.
I am surprised that a SAX capacitor was s/c but that is life I suppose.
I would monitor the Jensen caps carefully (if they are PIO) as we have had a few instances of them going leaky when hot.

John

[kt66se]

Hi John,
Thanks - yes I saw you had done quite a bit of work on the ECF80 conundrum.

Don't mind the voltage spec being out, just wanted to make sure it would not stress the valve

Sorry, the caps I used were Jantzen Superior Z-Cap, don't know if any good or not but what I had lying around. (bunch of .47 caps)

C5 was the short cct cap, Peak Cap meter showed it as a 68 Ohm resister, the other cap, C4 hissed when knocked, only found that problem when sticking meter probes on the valve and knocking the cap.

Adam

[Phil Y]

Well done Adam,

Yes, they are a great sounding amp. I used mine happily for 10 years before finally moving onto one of the bigger amps as it suited my speakers and musical taste a little better.
I'm sure you have hundreds of hours of happy listening ahead of you.

Regards, Phil.

[Ali Tait]

Yes indeed, great sounding amp, I’ve had three lol. Enjoy.

[John Caswell]

Ah,
Jantzen caps are a different kettle of fish entirely so you should be fine with them.

John

[Greg.]

Yes, a fantastic economically available valve amp. I had one for a while and it sounded really good.

I expect the Jantzen caps are really good. Not tried them but I have used their inductors to feed the crossover in my highly modified KLS3 speakers and the outcome is excellent.

[kt66se]

That's good about the Jantzen caps, I've ordered some more, I have a KT88 that I purchased from vinylspinner a while back and that's up in the attic just now so will mod that ready for when the house renovations are completed

Cheers
Adam

[Greylag]

Slightly off topic, but I'm wondering John if you found you had any preference amongst the different ECF80's you tried?

[Richard]

I checked quite a few at the time, in amps and on the AVO 160, and Mullard were the best on test and sound to my ears. That said, others had wild voltages but still sounded good so I'd widen the usual voltage tolerances a bit in this application and enjoy whichever sounds good to you