bottle size on valves

[electo]

hi
i wonder if anyone knows if there is any diffrence in bottle size on the el34 valve

and what valves would you recomend at the moment i am useing
Electro-Harmonix EL34 Valves
but was thinking about the kt77

hope someone can help
mick

[Paul Barker]

I think there was always the fatbottle version of the 6ca7. Then I might just be thinking of Nick Wilshire.

[alnewall]

Yes the 6ca7 i have is a fat bottle. American version apparently. They have more space over there.
There does seem to be a variation between different brands of EL34.
Your EHs are probably one of the smaller ones. The Shuguangs are slightly fatter and taller. The other two brands i have are somewhere in between.

[andrew ivimey]

There are nearly one million variants of the EL34 - as to which is the best and what shape ... well... what looks most elegant, wins.

or pay through the nose and get Mullard.

[Phil Y]

Hello Mick, in my (very limited) experiments with KT77 v EL34 i found the beam tetrodes to have a brighter, coarser sound than pentodes but this could well be down to the particular amp being used, others will probably disagree.

Regards, Phil.

[Ianm2]

I tried a few el34s.

the EH are excellent, posh sovteks I think

didn't like the fat bottle ones

shuguang and valve art, too, a slightly more forward aggressive sound, great value for money and very acceptable, the same 'colouration' I have noted with chinese iron, funny that, must be the materials/processing, up there with the EH, thinner glass, but perfectly reliable.

jj tesla ok, not my fave, but perfectly ok, thick glass

not tried the new reissue mullards, but they are russian, made by reflektor, along with sovteks, and some others iirc, perhaps made better, perhaps a muchness

I didn't find an awful lot in it tho', you have some of the best, I would just enjoy them, and buy spares, or some chinese ones, small valves may help somewhat, what's your amp?

youo may be able to stick 6550s or kt88s in there, kt77 are quite rare, never tried them

kt66 worth doing, tried some chinese shuguang/VA, ok, but preferred el34

[electo]

hi

thanks for all your help

the amp i have is a YAQIN - MC-10L

i just have another question

can i use kt88 in it without rewiring it would the bias voltage need changing

i am into electronic but dont know alot about valves

hope to here from you soon

mick

[Ianm2]

poss. the bias would need altering, but yes apart from that, straight drop in, takes a bit more milliamps for the heaters, 0.1 each? which makes half an amp, that shouldn't kill the mains tx winding under any circumstances unless it is seriously kak.

Al reminded me, I forgot about the svets., yes they are my faves, buy you have to have the winged C ones, there are 2, those and some others, reflektor again I think, and they aren't as good reputedly, but not tried those, def. the winged C's were the best of the lot, markedly, but, subtely if you get my meaning.

kt88s are nice, much more clinical and transistory sounding, clean, el34s are more valvey, bit of a culture shock, I wouldn't say better, just different. you either love or hate them, 6550 worth a try, sounded lovely in wads amp, airey, again similarly clean, but diff to kt88, poss even more colourless.

one thing you may do is find the way the output valves are connected, there are 3 ways, wire them as a false triode, ultraliear, yours I suspect, gives near pentode power, but triodey sound, and full pentode, its worth altering and see which you prefer, but you may need advice, its only a few wires. if you are clever, you can even do it with a switch.

is yours adjustable bias with a pot? should be easy to change tubes, but you have to search to find the bias, I have seen anything from around 50% anode dissipation to 80% in push pull, most reckon for good sound and valve life to be about 70%.

you find this method

1/ find power rating of tube from manual or online, el34 is 26 watts, kt88 is 36?? 42??
2/ make 70-75% ( multiply answer to 1 by 3 and divide by 4, or divide by 10 and times by 7), is the desired power
3/ go inside amp, with multimeter and measure volts at anode if adjustable bias, extreme care, risk of death whenever you go in amp, poss. 400 volts or more.
4/ this 70% desired power = volts measured x current desired
5/ current desired = power desired/volts measured

current is now 'fixed' so,

6/ look at cathode resistor value
7/ times this by the current desired
8, which gives volts across cathode resistor, as V=I x R, measured by your meter across the cathode resistor, whilst twiddling bias pot, then twiddle rest of the valves the same.

hey presto how to bias your amp. hope that's clear as mud

note, this power is not the same as power out of the amp, this is the DC power due to the DC volts measured, times the DC current thro your valve.

AC power is your music, and its different.

if each tube is using 20 watts of DC power, that's 80 watts.(4 tubes)

And if it puts out, say 20 watts per channel, you are putting in 80 watts, getting out 40, so you are getting 50% effiency. its not as straightforward as that tho'

[hal55]

You have a YAQIN - MC-10L, can I just ask how you find it? I might be in the market for a small valve amp after I build my 25Ts.

Thanks

Hal55

[electo]

hi

thanks for all your help ian will get some kt88 and give it a try

the YAQIN - MC-10L is a great amp lows mods and highs sound good to me

had a couple of problems with it

one of the el34 had an internal short on it the anode plate started glowing red

the other is the mains tx get a bit warm but sorted that with a auto tx
the voltages were a bit high to heaters were running at 6.7volts

i have changed all the chinsse valves to
russan 6n1p
Electro-Harmonix EL34

will try the chinsse one when my replacments come

hope thats some help

and thanks again
mick