5876 is a high mu triode, price is reasonable, 20-30 $ around,NOS amplification factor 56, plate dissipation 6W so it can be one stage in gain and drive, even the power tube is in positive bias, I built one in 10 years ago, very simple circuit . it can deliver 8W (8ohm) with 1.5V in-put, if you want more sensitivity you can replace the 100K resistor with a 600 ohm 1 to 2 step up in-put transformer, than you will have 1V in-put to 8W out. this amp costs much cheaper than a 300B SE, but sound better to me
Tony KY Ma
Tony KY Ma
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809 is a radio transmitting tube, it's power is bigger than a 300B, in audio use you can let it works in negative bias with high voltage (1000v) and small current (3ma), but do not sound good, in other way, positive bias, voltage can be much lower and have a high current(similar to 300B SE) then sound wonderful. the only condition is need a power tube or semi power tube to drive, also need a interstage transformer to match the impedance .
no socket for 5876, I use a big fuse holder for it, quite hot at plate, make holder's metal change color, but use for 10 years problem free,
sound quality, it can challenge any other 8 watt class SE amp in negative bias, no matter how expensive they are
Tony KY Ma
no socket for 5876, I use a big fuse holder for it, quite hot at plate, make holder's metal change color, but use for 10 years problem free,
sound quality, it can challenge any other 8 watt class SE amp in negative bias, no matter how expensive they are
Tony KY Ma
It's my understanding that most of those pencil, lighthouse, planar and etc. triodes had ugly curves (imagine 12AT7, flattened and mushed a lot worse). Nothing that matters when you've in class C anyway, and it's a nice way to generate gigahertz gain. As mentioned, the grid was ground, while the plate and cathode connections were made inside resonant cavities. You should probably consider bypassing the electrodes as close to the tube as possible (100pF plate to grid, let's say) to ensure it's not oscillating at UHF+ (and this is an oscillation that you well and truely will *not* see on the oscilloscope!).
Tim
Tim
After 10 years and a change of colour, they're probably no longer capable of UHF...
The stuff that's capable of UHF in them is held in a vacuum - the perfect preservative
Cheers!
The stuff that's capable of UHF in them is held in a vacuum - the perfect preservative
Cheers!
Which is why valves last for ever
Just play it
, as ever Stuart..Did Mark post my message?
Hi All
I have no knowledge in UHF, that I can not join the discussion with you guys. but I don't think the interstage transformer will pass the UHF signal. to me ,data from handbook can only tell me how the tube works but not how it sound, I always judge by listening and compare, distortion rate to me mean nothing, for example 60HZ sound with 0 distortion still a noise of hum. no one will say which hum sound better
regard Tony KY Ma
I have no knowledge in UHF, that I can not join the discussion with you guys. but I don't think the interstage transformer will pass the UHF signal. to me ,data from handbook can only tell me how the tube works but not how it sound, I always judge by listening and compare, distortion rate to me mean nothing, for example 60HZ sound with 0 distortion still a noise of hum. no one will say which hum sound better
regard Tony KY Ma
Hi Shoog
for 5876 is negative bias, I use a ni-cad instead a resistor, save a by pass cap. 809 is in positive bias, about 12 ma, I use a LM 317 for voltage supply, just make sure the two currents (at the interstage transformer's pri and sec.) is in opposite direction, magnetism will cancel each other, I like triode better than others I only judge by listen and compare,curves, as long as it can work
regard Tony KY Ma
for 5876 is negative bias, I use a ni-cad instead a resistor, save a by pass cap. 809 is in positive bias, about 12 ma, I use a LM 317 for voltage supply, just make sure the two currents (at the interstage transformer's pri and sec.) is in opposite direction, magnetism will cancel each other, I like triode better than others I only judge by listen and compare,curves, as long as it can work
regard Tony KY Ma
Which is why valves last for ever
Well, tubes do last forever sitting unused on the shelf or in equipment that sat unused.
Well, tubes do last forever sitting unused on the shelf or in equipment that sat unused.
Mr. Koichi Shisido who passed away in 1997, people call him father of single end. He dug out a lot transmission tubes like 800 808 826 838 830 805 etc. converted them to be use in SE amp for audio. He wrote a book about the conversion, He did compared those tubes working in negative bias (high voltage over 1KV and less current only 30ma), sound not OK, but changed to a positive bias, every thing changed (low voltage 250-800v high current over 100ma) sound wonderful. WAVAC is making some of them in the market Happy New Year Tony KY Ma
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