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I will be the first...
Ahemm........
I'm driving my stereo 845 amplifier( 1020 volts measured at the plate) with one 5691 running at 2.5 ma. for each section. Yes....my stereo amplifier has 3 tubes.
Follow Ups:
I followed Jeffs questionable advice of reterminating all of the leadouts on a nice big beefy Heyboer transformer.
Later the secondary shorted against the chassis as the holes were too small for all of the wire and I didn't use grommits.
I then proceeded to give Jeff hell for some time before I figured out a 2 amp fuse was more appropriately sized than a 1 amp. (this after fixing the leadouts).
Power transformer and amp have been fine ever sense. I'd still never cut up leadouts on nice transformers again. :)
I'm getting....lazy....in my....er....Golden Years.
I'm use inexpensive adjustable DC power supplies for heater voltages now.
Very good idea to have some adjustable bench supplies for low voltages. I have a bunch of 30v, 2A adjustable supplies. I only use filament bias with 4P1L tubes - nothing else anywhere. So it's an easy step to just dial in the voltage. For two tubes in parallel for the output of my PSE amp it's 28v at 1.2 amps. Simple.
the first time I tried replacing the panels on a Quad ESL I hooked up the diaphragm to the HV- shredded the panel(s) when I plugged it in.
Experimenting with a LTP circuit on the bench, full bipolar supply of +/-350V...hooked up with a 6754 rectifier on B+ and two 1N4007 on the negative. The LTP conducted first, pulled main B+ caps well and thoroughly negative and then spread their guts all over the bench.
One wee diode from cathode-to-ground would have never allowed that to happen...LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Kept in a drawer for 14 years audio note kit 4 6V6 stuffed board counting that someday a pair of used OPTS pop out and they did a couple of months ago in Hungary . (I was too cheap to order from Peter ) Spent a couple of days assembling the whole shebang in par metal enclosure. Fck it always looks so simple and easy than it stretches to hrs and hrs ...Din't check beforehand if the board works because I remembered it worked 14 years ago when I put all those new panasonic and cerafine caps and checked it out. After assembly
one channel was distorting badly so I disassembled it (not easy with this ed it type of amp and checked it out , all was Ok and static operation points and voltages were spot on Wtfc?? I fire up osciloscope (first time in 3 years;( and started poking around almost frying that damn thing but apparently that offending channel was distorting on the OPT . Uhh,... ficking Hungarians sold me a bad trans me thought (although the trans was a year old , quite pretty with copper shrouds and big for 6V6 amp, clearly a winner AN (UK) quality) devastated I put it on the shelf for two days than returned to it to discover that I hooked up the the CT of primary to one of the plates ...I happily put the cover on to discover that I really should have payed $15 more and order a fully perforated one.. I loved the sound from the first note . Must be the best cheapo amp I heard although it's circuit is seemingly more complicated that it really should be.
I like it so much that it deserves full choke input with Lundahl Power and choke iron which it will get ones I cure my nerves a little . There is more to the story , much more but I don't want to look like a complete moron hehe...
Edits: 05/01/15 05/01/15 05/01/15
Hopefully ,I will find the willpower to do it . I already acquired perforated chassis cover and Lundahl Iron . The irony in all this is that I bought and sold two of factory kits 4 during that time for around $500-600 mark just because I had that board and I was determined "to make it cheaper"
Well the truth is the amp will cost me actually quite a bit more in time and money so no savings whatsoever but whoever is DIY-ing knows already that "saving illusion" trap ...The only thing is for whatever reason I like this one more than the other two counted together ..Must be my refined construction /execution skill hahaha...
You should start to work on that better power supply, I'll bet you can get it done in less than 10 years! :-)
But I'm one to talk, I have a friend's PP KT88 monoblock on my bench since last fall so I could fix it for him. I'm pretty sure it is now 100% okay, but I've been too busy to fire it up and test it.
I use only TV tubes, I'm too cheap to buy any real "audio" tubes
JH
and kept tweaking them- they were built on Wurlitzer organ amplifier chassis.
The last tweak was to go from SET to push-pull since the chassis had the hole for the socket already (the original Wurlitzer chassis used push-pull 6V6s).
The push-pull version was so much better I never looked back. More bass, more speed, smoother sound, more detail. The extra power didn't hurt either.
My first scratch built project - 2nd electronics project ever - a simple SE 45 amp, I hooked up the heater on a 12AX7 as 12.6v instead of 6.3
"Gee, I know 45's are low power, but I can barely hear it"
I have all these nice Underarmor and Nike dry fit shirts with a hole the size of a quarter around my navel! Seems late at night the soldering iron has a way of getting out of place. At least it gives my kids something to laugh about.
On a more serious note, I built an amp once with the positive speaker terminal from the OT grounded to chassis. I chased no sound for a day or so before I found it.
Jim
I prefer source/emitter followers to cathode followers, pentodes to triodes, and mosfet based "pentodes" to tube based pentodes. I still like tube topologies, I just like them made from sand.
.
My amp and preamp have been dissassembled
and in the process of upgrading for a year.
At first because of analysis paralysis,
then my computer died with all schematics,
so had to redesign with some new parts ordered
but now just procrastination.
DanL
Two different times I've let a 300B roll off the workbench and .... well, you know the rest.
A few weeks ago I broke a NOS, EIMAC 75TL. I just about cried.
Cal
I only use 4P1L tubes - input and outputs. They were so cheap when I bought them, and I have nearly 200, that I could throw a bunch at the wall and not care! Hmmmmm.... peace of mind....nice!
Oh gravity, thou art a heartless bitch!!!
- Sheldon Cooper
Yup , not a tube (I simply refuse to think how many I broke ....)
but after a listening session with a friend and few bottles of a red one I fired up the turntable and started DJ-ing .... Finally I put Brubeck's "take five" and dropped the needle on the record and broke the boron cantilever of my cherished Dynavector XX-1 cart.....
Now I only drink when I work on tube amps.. With vinyl I usually "take five"
Mine is the fact I haven't built one yet, not DIY not even a kit. I have a nice CJ SS passive bi-amp but come on tubes are it. For me it is a combo of laziness and money.
E
T
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