KEL84 Complete

[Phil Y]

I've finished my KEL 84 with no major problems. It only has about 4 hours use on the clock so far but the sound quality certainly shows promise. Compared to my stereo 20 & home made pre-amp i would say the frequency extremes are better and so is low level detail, but the mid range lacks some air and warmth. I think this is a good start as from previous experience, i am expecting things to improve a lot over the few weeks as everything "burns in".
If people are interested i can give a run down of my experiences building it, but not tonight as i am a little busy.

Cheers, Phil.

[Allen]

Well Done!

[Primalsea]

I'm interested in what you said about the air and warmth on the mid range of the Stereo 20. I find that the ST20 sounds more like a transistor amp. It seems to have the failings of a valve amp with none of the benifits. The bass is a bit unclean and fluffy and the midrange has a forward balance just like a transistor amp. So what you seem to get is something that sounds solid state but without the tight control of the bass frequencies.

What I like about valve amps is the way they can handle the midrange. Voices just seem to come out of a deep inky black silence. This is a worthwhile trade for loosing some bass control unless you have some kind of Audio Research monster that has 12 KT88's in it that is.

I was hoping that the Kel84 would have that midrange quality I'm looking for and also have decent bass grip as well.

[Phil Y]

Don't panic! After only a few more hours listening the midrange has opened out a lot. It is early days yet. No offence, but was the st 20 you heard working well? I agree about the soft bass but i think the mid is pretty good on mine.

[Swithers]

Hi All, Have to say my st20 dont sound like that , The mid is excellent,Bass is not woolly at all, In fact its very clean & tight, But i guess it all depends on what els is running with it, I have spent alot of time with leads from pre amp to power amp,This seems to make alot of difference to how my amp sounds.
I also found an active pre was just to much for the st20 so have made a passive pre which works great with the st20. Thanks Steve...

[KennyK]

I too can confirm that the KEL84 does need some time to burn in. Mine now sounds much more detailed and the bass has gone from when I first powered it up to if you know what I mean. the KEL didn't suffer from that 'sugarysaccharine' sound that the PRE had when it was burning in, and the Gamma Aeons I (briefly) had running when they were cold.

I'm hearing much more detail and music than I ever did. and 15wpc is more than enough for my ART Expression V6s, though I did manage to get the bass to break up on the peaks of 'Shpongle Falls' from 'Are You Shpongled?' at louder than normal listening levels (11 o'clock on the WAD PreII, with the KEL volume control the way up - using it as a power amp) though that could be down to the vibration upsetting the CD player.

[Phil Y]

I shall make a start on my build description. This may come in installments as i am only a 2 finger typist and quickly get cheesed off!
To any one thinking of building the amp, i should say i could have built the kit exactly as supplied, but i have made a few small changes for my own satisfaction. Isn't that the point of DIY, doing things your own way?
The chassis went together fine except that the spigot hole for the switch had to be opened out a little as it was in the wrong place and there was quite a lot of burring around the phono socket holes which took a little while to file off. Although pretty obvious there seemed to be no mention of fitting the PCB pillars.
I fitted shake proof washers under mine. I also fitted shake proof washers under the earth post, to the transformer bolts and the choke. I replaced the output transformer bolts with M4X40 as these fitted much better than the M5s supplied. The heads on the supplied ones did not sit flat on the transformer caps as they were too wide. This was also the case with to a lesser extent with the ones on the mains transformer. With these i filed a small bevel on the under side of the heads so they fitted the curve on the transformer cap. Also with mine the caps on the OP TXs did not sit quite straight but i found carefully triming back the unused connection lugs on the top of the TXs aloud these to sit straight. I don't think the instructions mention mounting the choke but like the PCB pillars this is fairly obvious.
I didn't fit the front pannel and knobs until my amp was finished and bench tested to stop any chance of marking them during assembly.
Thats it for now as i've had enough of typing.To be continued......

[Primalsea]

I have just repaired all of the electrical side of the ST20 and as far as I know it's in fine working order. I would'nt say it's a bad amp as such, just not what I was expecting and not as good as some of my solid state amps. It has a very solid state sound and just seems to lack the qualities that good valve amps have.

But as said before it all depends on what it's with and what valves are being used. Mine isn't running anything special valve wise which could explain as few things. Also I have the older design in "exciting grey" which again may be a world apart from the later design that came in "more exciting gold"

Anyway, Grand job on the Kel84 and keep the info coming. I hope to get one soon but have decided to finish my speaker project 1st.

[space hopper]

well done the kel84 is a good amp. i must say i don't remember my st20 sounding solid state but it has been away for some time now

[Phil Y]

Here goes a bit more.
The last thing to mention about the chassis was that when i turned the selector switch, it made a bit of a clanging so i lined most of it with Dedshete to dampen it.
The PCB went together with no problems. The instructions said to top side solder it but mine is plated through so this was not necessary. The only bit that needed top soldering was on a couple of the HT rectifiers where the holes were drilled out so the through plating was gone. I presume this was because the supplied diodes(UF5408 ultra fast soft recovery) have thicker legs than the original type. The only error was that my kit came with chassis mount valve bases instead of PCB types but i recieved replacments in 2 days so top marks for customer service! When i fitted the PCB i put M3 nylon washers under the screws. Now for a larger deviation from the plans. Apart from the feedback connection which runs close to the mains transformer and choke, i used no screened lead in my amp although it was supplied for all the signal wiring. The reason for this is that the pre-amp i built for use with my Leak has no screened lead in it and has had no hum problems so i reckon it is not needed at line level . Also, although i can't do a comparison, i would be willing to bet the wire i used (7X0.2 silver plated with PTFE insulation) will sound better than the screened lead supplied. It is also easier to wire up and is heat proof. If i was to build it again i think i would attach all the wires to the selector switch before fitting it to the chassis and then cut the wires to length and solder them to the phono sockets. I think there would be more room to work this way. It is quite tight to work round the switch once it is in the chassis.
More tomorrow.
Cheers, Phil.