PreII/Phono II/ 6550 Russian Valves

[Dave999]

Hello
I haven't dropped in for a long time

I did a thing

Might have been a silly thing but i'm really quite happy with the sound and the lack of smoke

I purchased some 6N21B pencil tubes from a Ukranian, better for me to have them than the russioan military, and mounted them onto chinese valve base prototyping boards. i insulated pin 2 and bent the wire up as a flying lead for use later if necessary..(it was necessary)

6N21B
Pin1 C1
Pin2 Screen
Pin3 G1
Pin4 A1
Pin5 H-
Pin6 C2
Pin7 Is cut off at the factory but appears to be other end of screen
Pin8 G2
Pin9 A2
Pin10 H+

ECC83/12ax7

Pin1 A1
Pin2 G1
Pin3 C1
Pin4 H+
Pin5 H+
Pin6 A2
Pin7 G2
Pin8 C2
Pin9 H-


you can work out pins via missing pin and continuity of heater

Nice little things big long plates in a tiny glass enevlope with a pleat in both sides for strength
They glow like small hot dogs but not excessivly bright just a dull red

anyway they are not exactly ECC83 at all, but my random plodge through the spec on the areas i understood indicated it might not end in tears.
Please note:- I'm no expert

Obvioulsy you have to cater for the heater in some circumstances, just becasue my amp doesn't seem to mind you may not be so lucky.....!

these are 6 volt heater valves not 12 volt so wire them from 0 to +6V or 0 to-6V not -6 to +6

plugged them in
massive HUMMMMM
so i tied the screen of all of them together and then to earth.
hum back to normal i.e a bit if you stick your head next to the speakers

switch on- results in some strange noises as they warm on first use
no magic smoke escaped.
been in there for 6 months which included the tunes for one 51st birthady (all afternoon and night) and one teenage "gathering".
Both of which give the HIFI a battering it wouldn't normally see. On and in use at volume for 6-10 hours .

All i can say is the pre II power supply seems to handle it all no probs
and the sound
Nice bass, sweet trebble loads of space.

Possibly the best outcome from messing about plugging in valves that should not be in there that i have had.
They make a nice, nearly an ECC83- a-like at a fraction of the cost .

Getting harder to find becasue ECC83 based guitar peddle circuits are said to have "Great Tone" when these are used, so the guitar folk snap them up

in other areas

In the PreII I have a 6N1P EV military spec and i like it

In the 6550 I have 6F12P as ECF 80s which sound better than the modern style logo, early 80s, white shield mullards that were there before

These too have served me well now for a couple years

obviously there will be some bias to my appraisal, i did the work, so i want it to be a success, but normally I get fed up with a change, and change back. I haven't felt the urge so far

pictures to illustrate my bendy-wire bodge. seemingly pencil valves are too small to care about orientation.. supposedly used in missiles and planes

Dave

[bob orbell]

Very interesting Dave, I use two 6112 tubes in a buffer stage and they work well, I have the buffer before my Stax ear speakers, and the buffer also makes strange shrieking sounds as they warm up, once warmed up there is silence. Bob