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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: 211 SE power amp
PostPosted: 20 Sep 2013, 19:17 
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I'm a little ahead here with this thread. I do have a couple of projects to complete before starting a 211 amp. But I was wondering if there are others who have built one and who have some schematics to share. I have some large (25W) Edcor OPTs, 2.5K if memory serves me, for the project. I had a toroid wound to 1200V for the HT and have ceramic sockets and tubes to go.

The original amp I was to built used a interstage tranni and 6SN7 driver. But I'm not sure this is the best way to go as the amp peaked at 15K due to the I interstage. Most of my latest power amp go from about 32K to 52KHz (Silver Dragon). Arabella, my latest 6EM7 amp went to 39K from 10Hz.

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 Post subject: Re: 211 SE power amp
PostPosted: 20 Sep 2013, 22:08 
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Mark;

I've been investigating the 211 and think I can do far better on the response (well above 20kHz for sure). I'm currently thinking about a 6SL7 driver (the bias point is -72v so it needs some swing) but this is based on class A1 operation. I have been looking at class A2 but the transitions to grid conduction could get hairy. I'm not sure that it's worth it for the extra power. It looks like a lot on paper but it's less than 3dB at the speakers.

I should be able to post something in a few days.

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 08:45 
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Matt: I'm excited. Funny I thought 6SL7 as a driver tube when I started this thread. I'm looking forward to what you come up with. I'd like to say take your time. But don't. I already have some build ideas.

Matt let's go for sonic purity here I'm not concerned for max power. Let's build the best sounding 211 we can muster. 100% pure class A. I know you will do your design bit well and I will make it me goal to do the best build possible. Let's kill'm on this one like the Silver Dragon. Can you make it run on 1200V. I just like the thought of that. Just a little Frankenstein.

Good name for the amp?

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 09:03 
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I have built SE and PP 211 amps. For SE you need am OPT with 5K primary not 2.5K. For PP 10K. I used 2 6sn7's for my PP. With a plate voltage of 900 volts and 50 Watts out. For SE I used 6SL7's and got 25 Watts out. I used Hammond transformers as this was several years ago and Edcor were not avible. I used GE 211's that I had on hand that were from a TV Station that I worked at.


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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 09:19 
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wolfdog428 wrote:
I have built SE and PP 211 amps. For SE you need am OPT with 5K primary not 2.5K. For PP 10K. I used 2 6sn7's for my PP. With a plate voltage of 900 volts and 50 Watts out. For SE I used 6SL7's and got 25 Watts out. I used Hammond transformers as this was several years ago and Edcor were not avible. I used GE 211's that I had on hand that were from a TV Station that I worked at.

Thanks for the reply. I must have a look at my 211 OPTs maybe I have it all wrong. I will be going for a SE Class A amp.

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 09:55 
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mwhouston wrote:
Good name for the amp?
Well, with a tip to Mark's interest in opera, how about "Brunhilde", female second lead from the Nibelungenlied (The Song of the Nibelungs). I never liked the "Kriemhild" character very much and "Siegfried" just seems too predictable. Brunhilde, as the strong and beautiful warrior princess, seems just about the right mix for a big sweet sounding amp with a 1300V B+.

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 10:03 
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Hi Mark, sounds like fun. I really like the 6SL7 as a driver in A1. It is probably my most favorite triode voltage amplifier. I don't know why they are overlooked as much as they are. Probably because there are few new manufacturers of them. Most are NOS. All my commercial large power amps now use them. With a proper selection of operational point they can easily deliver the voltage drive you need. I would not use them for A2 as they have zilch current capability. My experience with them indicates that the lowest distortion occurs in the 0.5 to 0.7 ma current range. Used as an SRPP with 350 volts on the upper anode I can easily get a clean output swing of +/-70 V. They actually will go to nearly +/-100 if you tweak the values for max swing. I have seen (somewhere) designs using them as SRPP drivers to 300Bs and similar tubes. Such designs could easily be adjusted for the 211. Now if you used the 211 as a driver to run a 4CX1000... :D

Good listening
Bruce

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 13:05 
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The 211 also makes a good driver for the 304TL in class A. The only prolbem with the 304TL is the 2000V HV and the 25 amps for flill curent. Great sounding tube though


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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 19:18 
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wolfdog428 wrote:
The only prolbem with the 304TL is the 2000V HV and the 25 amps for flill curent.


And if you're an old ham operator, you'll just shrug at those numbers and think, "Meh, par for the course...." and go shopping :smoking:

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 Post subject: Re: 211 SE power amp
PostPosted: 21 Sep 2013, 22:24 
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You know you have enough power output when the lights dim on peak bass notes.

'Enuf nonsense now. It looks like it might be a great project. SE things are not my bag, but something monstrous or at the very least cool looking might find a way to my bench.

Good listening
Bruce

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