TMB with ecl82's

[melodymaker]

Mega long time lurker and learner here! Thanks to all! Any advice on a starting point for using ecl 82's. I scammed a sweet reel-to-reel cheap with all bugleboys and mullard pre's. All I need is an OT (S2 or Greydons' should work... Yes/No?) and any differences in screen, grid r & c. I've read post re: cathode r's. Any other thoughts? I plan on using JA's TMB schematic. Thanks!

Bob

[zaphod_phil]

That should work fine. You just need to make things a little easier on the ECL86 power pentodes. So wire the power supply and screen grid resistors according to Jason's mods - which you can see in the Lite IIa and IIb schematics. Measure your B+ voltage with the tubes installed. If it's around 300V, then a 180 ohm cathode resistor should be about right for the power section. If the B+ voltage is around or above 320V, then you try a 220 ohm value. You will be amazed at how loud a 13W gets.

[twangmaster]

Hey Zaphod, Isn't ECL82's more like 9 or 10watts?

[zaphod_phil]

ECL82s? Where did they come in? Doh!!! I see the original question was about ECL82s and not ECL86s. Shows what tiredness does. OK, yes, ECL82s should be good for close to somewhere around 10W. The cathode resistor value will probably need to be 220 ohms to start with then. Everything else I said will still apply. Due to being a little lower in gain than ECL86s or a 12AX7/EL84 combination, the amp will probably tend to have a bit more clean range on the dial. Should sound sweet with those Mullards in there.

[melodymaker]

Thanks guys! I'll start with the 220 ohm cathode and the Jason mods. How about the OT! I haven't looked up the impedence these little buggers yet. Thanks!!!

[zaphod_phil]

IIRC the ECL82/PCL82 tube specs recommend a slightly higher load impedance than for EL84s. But I think it's OK to ignore that and run them with an 18W OT. As these tubes are lower in gain, I wouldn't recommend the full Jason mods - just the power supply and screen part. Like I said, the Lite IIa and IIb schematics already have these incorporated.

[melodymaker]

I'll only copy the output section from the Lite II schematics. How about the original OT's from the Roberts reel to reel. I figured I'd use one to make a smokin little SE amp and maybe a Fender stand alone reverb with the other. Hoffman uses a Champ OT for his version. Close enough?!?!

[zaphod_phil]

Sure why not. Sounds liek a great idea. And make sure to use the Lite IIa or IIb schematics, not the original Lite II "screen burner" one....