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I got to thinking that before I go to all the trouble of refitting the 845 with the new power system I really ought to compare it to the 300B I built last year and see which one I like best. So I listened to some jazz, blues, classical and big band music on the 845 and then listened to the same songs on the 300B. Everything was identical except the amps. No contest, the 300B was the hands down winner in each case. It has a warmer, smoother sound that appeals to me. I shouldn't be surprised I guess as the same thing happened when I finished the 300B and tried it against the then 750vdc B+ 845. I thought I should at least try it at the higher voltage before deciding as I had heard it made a difference (it does, just not enought to displace the 300B). Sooooooooo ..... after all I have gone through getting the 845 up t0 1000vdc B+, it looks like I will be dismantling it and using the parts for future projects.
I certainly don't look on it as time wasted, I learned a lot and had a lot of fun too. And it did convince me I need to take another stab at learning some theory if I want to advance to the next level in this hobby. That reminds me, I better get back to the "homework" assignment Dave gave me.
Thanks again for the help you all gave, I really do appreciate it!
Follow Ups:
Since there is some similarity between your posts I will try to answer all questions with one post.
From my experience bread boarding a whole bunch of amps with different output tubes and different drivers I know that each output tube has it's own unique sound. You can tweak it and change it a bit, but a 45 will still sound like a 45 and a 845 will still sound more like an 845 than a 45. What I am really saying is that I prefer the basic sound of the 300B to the basic sound of an 845, that's all. All the other things you say are true, but I would rather spend my time trying to improve the sound of an amp that has an output tube I like the sound of. So far for me it's been the 45, the 300B and the 71A. I have bread boarded at least 3 or 4 different 2A3 amps and I never did find one (SE of course) that I liked better than the 45 or 71A for sound.
I haven't tried the 211 yet, and I would like to if I can find a pair that won't put me in the poor house. I may save the two chasis from the 845 with most the parts attached until I can.
I am afraid I don't have a copy of the schem for the 845 I can post. I tried finding it in the archives but the link said it had a lock on it and I don't have the key. It is GroverG's design if any of you are familiar with it. I can tell you it has 10k output trannys and the tubes are 6n7 to el34 to 845. I used russkie teflon coupling caps and some russkie oilers as well. Bias was -145 vdc. B+ was right at 1k.
I guess the bottom line for me is I like the sound of the 300B. Doesn't mean I won't keep trying other amps though. Know anywhere to get a good price on 211's?
Thanks for all the help!
Vince
Hi Vinney,you are now a very mature contributor with loads of experiencial learning behind you. I really liked your summing up.
I have been browsing your 211 questions above.
I don't go in for the 6c45 or any other high transconductance single driver solutions.
You do need to explore the 211, but if you can manage with the lower power output of the 300b try not to follow the high voltage schematics.
As you say every valve has a predominant sonic which forces itself on the design. This is as true of the rest of the valves in the circuit as of the output valve. For my money experiment with low voltage low bias but don't get all hung up on having to use super low impedance driver or special tecniques. There is a magic sound from the 211 low power at the turning point into a2, when combined with superb sounding other valves sheds the thin midrange (compared to 300b) and light bass characteristic of the 211 found in the convensional designs which seem duty bound to produce maximum available power from whichever output valve the design is for.
You can obtain a much better sound from the 211 used by thinking outside the box than any 300b builder will ever achieve.
It's a close held secret that all the circuits which maximise power from a particular output valve can be bettered in sound at the listening level by building an amp that has no hope of maximising power. Build for that level of listening you require.
If you remember I never did like it. Have not tried all of the latest offerings but still can't find as good a result as comes sratght away easy with the nos 211.The gevt4c is a great bread and butter valve.
The oxide coated WE 211D is out of this world. I only have one sadly.
Two completely different sounds, but both worth every penny. Money well spent.
You can tune your ears to enjoy the vt4c and soon forget how much better the we211d sounds. You have to or you would go mad.
Of course if money were no object I would crave every oxide 211 I could lay my hands on.
the NOS 211s would have to much better than the VT4 because these don't sound near as good as the cheapest 845s IME.
Vinnie, from the sketchy info (sorry if you've provided info I haven't seen) I can only deduce that you are comparing apples with oranges. No doubt the circuits are completely different. The power supply, the driver and the output trannies, not to mention the other parts and tubes, are all critical. The only way you can really compare is to build an amp that can easily cater for both tubes and even then it won't be a perfect comparison. Alternatively you need to build ideal amps (as much as possible) using very similar circuits and parts. Actually you'd be surprised just how similar amps sound when you just change the OP tubes and nothing else. Obviously you need to change the OP TX tapping and you'd be tying the 845's hands behind its back power wise.Don't give up on 845s so easily, I've built everything from 45s up and I still prefer my SE 845s. Granted I need the power on my main speakers (ESL/line array combo) but I've tried many others apart from horns. Take TKs advice and post some more info, particularly a schematic of both amps if possible before you dismantle the 845s, maybe it’s something obvious.
Vinny
Are these SET amps or PP? Im assuming SET but I want to ask you,have you tried driving the 845 with a 300b? Thats a nice combo as I,ve heard the cary 805 amps. I was thinking of building a parallel 300b amp to have the extra oomph..Also TK brought up a good point..If your transformer isnt optimized for a certain tube it can sound dry and lifeless.Im still debating which set amp to build for my logan panels but the 211 is starting to apea to me being I have a pair of nos ge vt4c.I run my aes cary 811 with an sv572 at times but it doesnt excite me like the citation 2 or the macs for that matter.
Maybe it would be worthwhile to analyze the design in more detail. For instance, which OPT did you use? Have you posted a current schematic of the amplifier (maybe I missed it)? Also, you might consider a 211. Unlike the 845, the 211 was originally designed for audio service. There's a distinct difference in the sound. Assuming the OPT is in the ballpark (~10K), you might only need to reduce bias voltage to drop in a 211. With 1KV on the anode and -52 on the grid, the tube will idle at roughly 70mA. Just food for thought...
"Unlike the 845, the 211 was originally designed for audio service."Um... no. the 845 is more suited to audio output than the 211. By history and design it's that way. Both will work - the 845 will work easier IMNSHO. FWIW Neither were exclusively designed for a single particular purpose (same thing could be said for most tubes)
I was sure I'd read that in several places, so I went to one of my few remaining older references following your post. The 11th edition (1947) of the Editors and Engineers' Radio Handbook shows the 211 specified for Class C telegraphy, Class C telephony and Class B audio. A GE 211 datasheet from '42 additionally specifies the 211 for Class B RF and Class A audio. I don't have an original datasheet for the 845, but the Handbook noted above specifies it only for use in Class A audio. Do you have an early 845 datasheet that specifies operating condition for RF?
The 845 is more suited to audio output than the 211. By history and design it's that way.
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.
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.
nt
Actually the power on the 300B amp is fine as is. I have a pair of really efficient JBL S8R's and I can't get past half throttle even directly off the walkman before it's to loud for comfortable listening. With my preamp it's got all the power I will ever need.
What I may end up doing though is trying to come up with the very best power supply I can because the quality of the power supply is a major factor in the overall sound of an amp.
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