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In Reply to: Re: This is bunk posted by arend-jan on May 8, 2007 at 04:27:21:
Both types were "intended" for service in radio transmitters. However, the 845 served as a modulator. That makes it both a RF and an audio type.Some FINE sounding amps have been made with both 211s and 845s.
BTW, the only construction difference between the 2 types is in the grid. Everything else is the same.
Eli D.
Follow Ups:
I'm thinking about more power for my power-hungry electrostats and I'm still in doubt about which way to go. I'm thinking about either replacing my 300Bs with the maxed up variants like 320B etc or perhaps a 300B like I have now driving a 211 or 845 (push-pull). That should give enough power for sure.But as I said, I'm much in doubt and I fear that with the increase in power I might lose the subtle details/finesse that I have now. But I have no arguments to support that it's just a feeling.
The most involving sound I ever heard was a 45SE on some very peculiar looking horns, but I like the naturalness of my electrostats too much to say goodbye to them yet. Can't have it all :-)
driving ESL/line array combos. Much better than all of the PP amps I've tried. With SE you can maintain that involvement you speak about with a truly holographic soundstage, and the 845s have plenty of power. I know what you mean about ESLs, for all of their faults I wouldn't trade mine.Rgds,
Naz
Hi Naz,sounds interesting. How are you driving those parallel 845s? Or even beter, do you have a circuit diagram?
In an interesting but slightly complicated way. Driver is basically a White CF using a 6H30P DR running off both positive and negative supplies. It’s DC coupled to the 845 to get rid of the coupling cap and to drive into A2 on peaks. I get about 75W from the two tubes with very low distortion right up to max power ... very efficient, rivalling PP but sounding way better!The WCF is in turn driven by a Russian 1578 (6H8 / 6SN7 equiv but better), which is also DC coupled and runs from the same supplies. It is basically a mu follower but with an added choke which provides greater linearity for the high voltage swing needed to drive the 845. Bias for the 845 is set by a pot on this stage. The only cap is between this and the first stage, a Siemens Cca (6922 equiv but better). I've tried IT coupling here but was unimpressed. I aim to revisit this one day with a much better tranny but I'm in no hurry because these (monos) sound better than any commercial amps I've ever tried or DIY I’ve built.
The circuit is my own but I can email you a schematic if you are seriously interested.
Thanks Naz, sounds like an interesting circuit. But as you say it's slightly complicated indeed. Four stages, two power rails and DC coupled does not seem like an easy project. But I like it and if I seriously start planning something like it then I know who to turn to. I'll probably have a dozen questions for you then :-)
> BTW, the only construction difference between the 2 types is in the grid. Everything else is the same.I'm not saying that you're incorrect, but the reference I noted in the previous post quotes different maximum anode currents. It specifies maximum anode current for the 211 at 175 mA, and the 845 at 120 mA. Unfortunately, there's no way to tell from the listing whether these numbers might be tied to different operating conditions.
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