Im currently looking at building a very similar spec class AB1 amplifier to this. How did you get by with using an 83 rectifier? Doesnt a pair of these tubes draw 140mA? A pair would require 300mA plus whatever the driver tubes require?
It depends how you design output stage and the operating mode, type 83 can do 250mA max as data sheet says, 140mA per pair is for max signal at full power (triode connection).. take a look at AB1 UL and tetrode connection, max signal is 100mA
@@ARASHMAFI1 OK didn't realize UL was so much less. I should easily get away with that then. Have been looking at rectifier choices and was considering an 83 as I believe they don't need to wait for the tube to heat up before switching on the HT. I was also looking at 3B22 xenon rectifiers.
@@ARASHMAFI1 yeah I know what you mean. I'm pretty sure it's not as critical with the design of the 83 compared to other tubes. My tube tester uses one inside it and has no standby switch.
@@nzoomed melted one like that on that amp, that’s why I added a standby switch in CT to let 83 warm up, in addition the power transformer secondary dcr has to be sufficient for 83 or you must add series resistance to it manually
@@nzoomed yes the screen grid can handle it for sure, it was proven decades ago in Williamson designs that triode strapped would be able to handle 400-420v without g2 melting
This looks great. Any chance of a link to the schematic? I've just got hold of some NOS 807's, myself.
Great sound! Enjoy!
warpspeed thanks 🙏
807 transmission tube makes a good sound
ODS yes it’s an excellent tube!
Im currently looking at building a very similar spec class AB1 amplifier to this. How did you get by with using an 83 rectifier? Doesnt a pair of these tubes draw 140mA? A pair would require 300mA plus whatever the driver tubes require?
It depends how you design output stage and the operating mode, type 83 can do 250mA max as data sheet says, 140mA per pair is for max signal at full power (triode connection).. take a look at AB1 UL and tetrode connection, max signal is 100mA
@@ARASHMAFI1 OK didn't realize UL was so much less. I should easily get away with that then. Have been looking at rectifier choices and was considering an 83 as I believe they don't need to wait for the tube to heat up before switching on the HT. I was also looking at 3B22 xenon rectifiers.
@@nzoomed definitely need to warm up on all Mercury vapor rectifiers, otherwise they could possibly arc over and self destruct
@@ARASHMAFI1 yeah I know what you mean. I'm pretty sure it's not as critical with the design of the 83 compared to other tubes. My tube tester uses one inside it and has no standby switch.
@@nzoomed melted one like that on that amp, that’s why I added a standby switch in CT to let 83 warm up, in addition the power transformer secondary dcr has to be sufficient for 83 or you must add series resistance to it manually
how much did the amp cost you to build?
400Vdc is way to high for g2 (screen grid)
smutra 400vdc plate voltage, not g2
@@ARASHMAFI1 how much you got on g2 ?
smutra it’s an ultra linear design, so there are 40% UL screen taps on the output transformers, I have to check, it’s been a minute. But def safe zone
@@ARASHMAFI1 Yes in UL it doesnt matter. Anyway, ive built a guitar amp with them running at 400V screen supply and they are fine.
@@nzoomed yes the screen grid can handle it for sure, it was proven decades ago in Williamson designs that triode strapped would be able to handle 400-420v without g2 melting
Just be very carefull with those long plate leads. You cab set up a RF oscilation
@@Steven-pv1xr noted ✅