Kegger
R.I.P. 1/12/1966 - 6/1/2017
TED (The Electrocution Device) as it was so happily named. 
Got a new driver tube, one that it ever so richly deserved as well,
(OK OK I like this piece of crap amp, it just sounds good dammit)
This was built over a year ago as a "test" for the 6GB5/EL500 outputs.
(Newman really liked the build back then) :yes:
Well ever since it was built I was pretty enamored with those outputs
as they have a really beefy feel an construction to them plus a sound
that is even better then they look, full top to bottom, clean and clear
I tried several different feedback schemes, but kept coming back with
none being by far the best sound on the tubes. (so none it was/is)
(I'm using some Edcor 16ohm to 5k trannies with 8ohm load for 2.5K)
I just used the amp from time to time but really wanted to do another
driver as when I first built it I misjudged how much gain was needed to
drive the outputs, originally 6SL7 direct coupled to 6SN7 follower on out
was waay more then enough, 6SN7 to 6SN7 was almost there, used the
adapters I have for 9-pin tubes and a 30mu tube was pretty much right.
(not much info on the EL500 in Triode let alone UL)
So I new a say 30ish mu tube with even just decent transconductance
would do a fine job, a 6DJ8 or the like worked nice in the adapter, but I
never did end up "wiring" anything in.
(thanks again Dave)
About 2 weeks ago myself and Squid are over Newmans picking up some
stuff including tubes when a box kinda stands out and I see another like
it, I pull the tube and say wow that thing looks way cool, figuring though
being a tube starting with 8 plus the interesting construction probably is
not going to be something with good heater specs let alone operating.
(8608)
As I'm pawing through more tubes Dave brought the PDF up on the laptop
O see wow 6.3v heater at 600ma, then we see 45,000 transconductance!
An see triode data of 30mu, holy smokes those are some really nice specs.
(that says driver tube all over it to me) :thmbsp: (beefy to, 10w dissipation)
OK get home do some research on this guy and find out it is basically E55L
but with cap top, humm good things about the tube, I like the specs, with
a plate resistance of 1k or less I get to thinking this just might fit into Ted
with it's power supply and driver needs/wants. (gotta find more)
Alright talked myself into trying them as I found some more, (not plentiful)
but hey I got enough to use them in 1 amp if they work out, with the 300v
supply on this amp then 8.2k plate load and 4v bias I can get 20ma working
with it looks like 125-130v on the plate, just crawling out of the knee in the
curves but It looks like it should be doable. (installed pretty much spot on)
(2 2v red Led's for bias will do the trick as well)
Gotta say, that 8608 I feel is uber cool plus excellent match in both specs
and cosmetics to the EL500, looks like a little brother to it, same socket an
same cap top let alone same bottle shape.
On to the sound, luckily it is also an upgrade in that department, deeper an
better bass, mids about the same as others but better up top clarity to boot.
(not night an day but defiantly an upgrade) Very Very glad it worked so well.
Anyway figured a few may enjoy the story behind the amp or someday build 1.
(maybe sometime he will get a pretty face) :tears: ..Sorry about the rambling..
For reference (if I even need it sometime) attached is the schematic, an pic's.
(300v supply, well filtered)
Got a new driver tube, one that it ever so richly deserved as well,
(OK OK I like this piece of crap amp, it just sounds good dammit)
This was built over a year ago as a "test" for the 6GB5/EL500 outputs.
(Newman really liked the build back then) :yes:
Well ever since it was built I was pretty enamored with those outputs
as they have a really beefy feel an construction to them plus a sound
that is even better then they look, full top to bottom, clean and clear
I tried several different feedback schemes, but kept coming back with
none being by far the best sound on the tubes. (so none it was/is)
(I'm using some Edcor 16ohm to 5k trannies with 8ohm load for 2.5K)
I just used the amp from time to time but really wanted to do another
driver as when I first built it I misjudged how much gain was needed to
drive the outputs, originally 6SL7 direct coupled to 6SN7 follower on out
was waay more then enough, 6SN7 to 6SN7 was almost there, used the
adapters I have for 9-pin tubes and a 30mu tube was pretty much right.
(not much info on the EL500 in Triode let alone UL)
So I new a say 30ish mu tube with even just decent transconductance
would do a fine job, a 6DJ8 or the like worked nice in the adapter, but I
never did end up "wiring" anything in.
(thanks again Dave)
About 2 weeks ago myself and Squid are over Newmans picking up some
stuff including tubes when a box kinda stands out and I see another like
it, I pull the tube and say wow that thing looks way cool, figuring though
being a tube starting with 8 plus the interesting construction probably is
not going to be something with good heater specs let alone operating.
(8608)
As I'm pawing through more tubes Dave brought the PDF up on the laptop
O see wow 6.3v heater at 600ma, then we see 45,000 transconductance!
An see triode data of 30mu, holy smokes those are some really nice specs.
(that says driver tube all over it to me) :thmbsp: (beefy to, 10w dissipation)
OK get home do some research on this guy and find out it is basically E55L
but with cap top, humm good things about the tube, I like the specs, with
a plate resistance of 1k or less I get to thinking this just might fit into Ted
with it's power supply and driver needs/wants. (gotta find more)
Alright talked myself into trying them as I found some more, (not plentiful)
but hey I got enough to use them in 1 amp if they work out, with the 300v
supply on this amp then 8.2k plate load and 4v bias I can get 20ma working
with it looks like 125-130v on the plate, just crawling out of the knee in the
curves but It looks like it should be doable. (installed pretty much spot on)
(2 2v red Led's for bias will do the trick as well)
Gotta say, that 8608 I feel is uber cool plus excellent match in both specs
and cosmetics to the EL500, looks like a little brother to it, same socket an
same cap top let alone same bottle shape.
On to the sound, luckily it is also an upgrade in that department, deeper an
better bass, mids about the same as others but better up top clarity to boot.
(not night an day but defiantly an upgrade) Very Very glad it worked so well.
Anyway figured a few may enjoy the story behind the amp or someday build 1.
(maybe sometime he will get a pretty face) :tears: ..Sorry about the rambling..
For reference (if I even need it sometime) attached is the schematic, an pic's.
(300v supply, well filtered)
