[regenfreak]

ECC85 have a nasty reputation for not lasting long and their gain falling. Usually the first thing to go is the ability of oscillators to start.

In my case, the ECC85 is oscillating happily in my test rig but its output voltage vs frequency response is non-uniform. The components layout of FM tuner is very critical and an art form itself. i had a number of theories why is not oscillating in my first tuner but all of them have been proven wrong. The ECC85 would only oscillate if I connect a crocodile clip with a lead to the anode which is very puzzling for me.

On the other hand, the number of double triodes suited for cascode use because of heater-cathode insulation for the running voltages of the upper triode, and also the need to keep cathode-heater capacitance down to prevent horrible coupling problems, is rather limited.

Thats why i will opt for EC88CC in cascode in my next adventure. It has higher transconductance than ECC85. Unlike ECC88, the miltary spec ECC88CC version has high voltage spec Vh-k for both triodes. The only disadvantage is that the EC88CC or ECC88 are highly sought after by the audiophiles who push up the prices to insane level.

I stopped using valves for any new work a long time ago. The only valves being made revolve around hifi people and guitarists with fat wallets. Radio-type valves aren't being made and I see them as a dwindling resource, so I choose not to use any of them up and leave the remaining ones for servicing period equipment.

Sometimes transistors are the right answer.

I have been building transistor/IC AM and FM receivers for a year. In my heart, I prefer building valve receivers as i started off playing with valves before i learnt solid state electronics. I do not really care much about valve amplifiers and audiophile stuff etc. It s a pity the fat-walleted audiophiles drive up the prices of RF valves. I always look out for cheaper eastern europe/russian alternatives. A Mullard ECC88CC can fetch £40-50 while a Esatern european alternative would cost about £15.

a Revox B261, the manual is available on-line. This takes very different approaches. LC filtering and no ceramic filters. separate stages of limiting in the IF. An analogue pulse-count discriminator, and stereo decoding using several general-purpose ICs, not the usual one-chip wonders.

Sounds very interesting. I will look for the schematic.