6L6 allround Single ended stereo integrated amp

SE integrated EL34 / KT66 / KT88 / 6550
This too is one of my early 1990 designs that I just exchanged from a customer who wanted an upgrade
He now has a 2A3 PP amp with the tubes integrated inside the chassis (he got married you see and his wife
was not very enchanted by his SE Chernobyl amp : get this nuclear power station out of my living room! )
Yes, with one circuit you can use all these different tubes and listen to their differences in perfect conditions .The only thing that is different is the respective bias requirements .Here I have opted for cathode bias and a variable 3 watt power resistor in order to adjust the different levels of bias for every tube .Newly added is a mA meter with a switch so you can choose between which tubes to measure.
The actual circuit is very plain .It's capacitor coupled and has a very warm tube-like sound due to its auto bias everywhere .
The first stage uses a paralleled 2C51 .I like this tube so much I had to parallel it so I could use a 2nd tube for the other channel The driver has super imaging qualities and words like air and space can be used to describe the sound here. It really pulls the best out of the output tubes ,so it is fun switching on. It runs on conservative voltages so it is versatile, but you could get more power by raising voltages .
Quick description :
Bias for the first tube is set by the cathode resistor.
The load is the plate resistor // grid resistor of the output tube .
The gain is sufficient for direct input , no pre amp needed
This amp has no feedback at all and is very stable. It uses tube rectification for it still has a slight advantage over
Solid state ,despite the progress made until now. (With my new hybrid rectification I think that things have now changed ). A choke filters the mains supply.
The output tubes are in pseudo triode connected mode .
Tweaking ideas :
Blackgates & Elnas and maybe copper foils
Kit : future versions will run on
Lundahl outputs ( a small step forward ) and toroid power supply and hybrid rectification ( tube & diode so a single winding is used)
The chassis will look the same and the circuit stays the same
Specs : 6 watts on average , a KT88 can get up to 12 watts max but for that the voltage HT needs to be raised
Basic Kit :
2 EL34 + 2 2C51 + tube sockets
2 power pots
2 LL1664 SE/60 mA
1 power transformer
1 274B rectifier tube + socket
1 chassis complete , all holes punched
all resistors Dale and capacitors some MKP,some electrolytic with bypass
mains cable and fuses
RCA & speaker terminals
1 6 channel stereo selector
2 choke 20H/80mA
kit price : 699 euro
option cover for output transformers : 100 euro