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Could anyone e-mail me or show me other websites of good 211 schematics. I've been looking to build one for quite some time and only managed to find the following 211 schematic at:http://tinpan.fortunecity.com/saints/668/primer/
Unfortunately, the B+ voltage on JC's schematic is 900V to the 211 and have been told that for the 211 to really shine, you really need much higher voltage (ie. 1.3KV).
I've done a search in this forum and found only dead links to possible 211 schematics (404 HTML Error). If anyone could help me find such a schematic - I will give my 1000 thanks!
BQ
Follow Ups:
Given your 104dB/1W/SPL speakers, I see no reason why you need to get
into the proposed kiloVolt range of operation with a 211. I run an 845 at
450V into 91dB efficient speakers and get a very satisfying listening
experience, you could do the same with the 211.Lower voltage operation all around lowers the cost of building this amplifier
because lower voltage parts are more easy to find.I might be wrong making this statement but here goes: I'd conjecture the
reason why you see higher-voltage, higher-powered 845/211 commercial
amps is so that they can be mated easily to far less efficient but more
popular high end speakers such as the B&W Nautilii, the 801s, Martin Logans
et cetera et cetera. So unless you have such savage drive needs, maybe you
should shy away from the high-voltage design point that these products run at...The design I've roughed up sounds pretty darn good... You can certainly
upgrade the output transformer, and you can use different drivers - the
6C45, 5842WA are all options. It's going to be harder to get more than
4-5W out of my design because getting more power means swinging the grid
of the 845 over 100V. Tough to do with two stage amp *and* 2V sensitivity.
Pretty much have to go to three stages to get more - and you add more circuit
complexity...-- Jim
Thanks for your input Jim, is that 845 schematic much different than for a 211?
To be quite honest, I'd forget about the 211 and just go with the 845.
I'm not saying anything is wrong with the 211, its just for your application
you're in the money for this tube and so many people just have such good
things to say about the 845 at this operating point, as well as people saying
great things about the cheap $40 current production Chinese tubes.You have massively efficient speakers. ;) 4W is gonna be just fine and you
will be able to build this safely and cheaply. A guy here built a similar amp using
SRPP and 845's on LaScala's and just says great things about the music.
Check out the link below with Magnequests comment on this operating point.At 104dB, you're biggest concern is going to be hum. You will probably have to
go to DC filaments. groverg has done this with his 845 and can recommend a
topology that includes common mode chokes. I havent heard DC filaments, but
I like AC because its so simple.I'd say the only reason you might want to go for a 211 is:
- Need for serious crazy SET power (i.e. 20W and more)
- You have a stash of NOS RCA or Marconi 211 valves already. Serious Money.Another reason to choose the 845, its easier to get 5K transformers than the
10K you will need for the 811... Far easier. If you dont want to go the
Hammond route as I did, you could get the affordable but very good One Electron
UBT-2, or the Lundahl 1620/60mA or you might get an Electra-Print.I can assure you, for 4W, it's really magical. Most people that come over my
house immediately comment on the sound... And these are the kinds of people
that would say that they cant hear any different between "receivers" or speakers
when they listen at Tweeter or other such places... ;)I pulled out the stops on my design.... No capacitors in the signal path, just
glowing glass envelopes and magnetics... Ultrapath capacitor now. CLCLC
power supply - all oil caps everywhere - mercury rectifiers. Cheap to do -
at 500V. The coolest thing about my amp is the utterly massive powersupply.
It's totally over-engineered. It's heavy. It needs it own chassis. I think the
psycho power-supply is alot to do with why it sounds so good.You'll get what you want... Which is warm, transparent, charming sound... And
a big tall 1930's tube with bright filaments aglow. The look is definitely cool
too. Sure beats a 300B or 2A3 with their barely orange filaments.-- Jim
Hi Jim,Actually, i'm think of the 845 as next year's project. There will be many years for me to build. In my lifetime - could mean dozens of amps to fill a living room full.
I also plan to build speakers which I know will never be as efficient as the Klipschorns. Realistically, 90db/1w/1m speakers is probably all i'm gonna get so in times - I will need some tubes amps to drive them.
Also i'm use to listening to my Klipsch Chorus with a 400 watt SS amp - just enough to get me to rock concert level SPL. I would be short changing myself if I couldn't at least feel the music with some decents amount of watts.
Don't believe everything you read about high B+ and transmitting triodes. Many folks have been using 845's at low B+ with good results.I played around with 211's and finally settled on a B+ of 825v, 60ma as an operating point. It gave me all of the power I needed and sounded wonderful. It also allowed me to use some "reasonable sized" 15uf/1000v oil caps instead of a few much larger parts I had.
I was more impressed at the sonic differences made by altering the current than the B+. Also the power supply made a substantial difference - liberal use of swinging/smoothing chokes and smallish oil caps sounded way better than larger banks of electrolytics. I'm not sure the 866jr's made any sonic difference, but they sure looked better!
My circuit is very similar to PAE's (see link below)
The single stage driver is sweet and works well.
Mikey's FS-100's are fantastic.
The power supply for your 211 looks incredibly complicated. Making a PCB for that cathode supply module will be a task on it's own. Actually, where would I find such a module? It would seem that to build a 1.3KV power supply with simple C-L-C would be much easier.Another point I should bring up is i've seen most are running DC on the 211 filament heaters. This is a big concern for such a DHT. or is it not in the case of the 211?? - how long will the tube last? And does running 10V AC cause that much noise that one would only think to use DC and live with replacing 211 tubes more often?
BQ
Acutally my power supply is very different than the one on PAE's site. I use individual AC transformers for each 211 filament, the 866jr and the 6C45 filament. The large Acro TP-550 provides 825-290-0-100-290-825 as well as additional 5 and 6.3v filament taps.At turn-on the individual filament transformers for the 211, 6C45 and 866jr's are started. There is a 2 minute delay to allow the 866jr's to come to full temperature before the TP-550 is started. This is done with a digital delay board.
When the TP-550 comes on it feeds the 825-0-825 to a pair of 866jr's, which go thru a damper diode for slow turn-on. This is choke loaded with a swinging choke --> 15uf/1000v oil ---> smoothing choke ---> 30uf/1000v oil with a small bleeder resistor for the B+
The power supply for the 6C45 is a 6106 (bendix indirect 5Y3GT with a very slow turn-on) into 12H, then 100uf for the driver stage.
The 100V tap provides bias voltage thru a 1N4007 and simple filter/divider network.
All said, it's pretty simple. First pre-heat 866jr's and filaments on 6C45/211's and bring up the bias. 2 minutes later start B+ which has a slow turn on because of the damper diode. Lastly the B+ for the driver stage comes up.
Even with AC on the 211's I get very reasonable hum levels. The power supply actually has a bridge rectifier and cap to filter the 10V supplies installed, but I never wired them up. AC was plenty quiet - even on Altec speakers.
What about the late John Camille's SE211 that was in Sound Practices.For $30 you can get all the back issues on a disc, including the 4 articles on this amp. JC has a wealth of detail in these articles, and would be worth buying for any tube amp builder even if you don't build this design.
I think I would be quite interested in getting the CD archive. Is this magazine catored to the DIYer? Do they still run publications?The only other publication i've read in vacuum tube gear is "Glass Audio". However, in the past i've never been a real fan of hifi magazines (all the biased opinions that really didn't mean a thing when it came to listening the gear in your own living room).
I think I would be quite interested in getting the CD archive. Is this magazine catored to the DIYer? Do they still run publications?SP was a hardcore DIYer mag, with a ton of interesting articles and data, on amps, tubes, HE speakers and TTs. Unfortunately, it's not published anymore, but the disc of all articles is very much worth the money. Take a look at some of the sample articles at the link below. The pieces on the Camille 211 are very well described in theory and practice by a skilled engineer and have a lot of excellent detail implemention ideas. If you find anything written by John 'Buddha' Camille, read it, as it will surely contain a lot of nuggets of wisdom.
The only other publication i've read in vacuum tube gear is "Glass Audio". However, in the past i've never been a real fan of hifi magazines (all the biased opinions that really didn't mean a thing when it came to listening the gear in your own living room).
I read the articles on the Sphile website, and most of the others like PF, but it's only entertainment (like looking at Penthouse rather than having a shag) because having heard some of the gear and the way it's decribed, I find myself scratching my head in amazement that they can think a lot of it sounds good. aX is too expensive to subscribe to overseas for what I get out of it now.
Your secure online ordering doesn't seem to work.Could I make the transaction by e-mail? Do you accept Paypal?
Brendon
It's not my site, it belongs to Joe Roberts the owner/publisher of Sound Practices. I'd suggest emailling him at info@southernelectricaudio.com and asking directly. Nice guy. I ordered mine through the site ages ago with no problems; perhaps it's glitching.
Paul helped me get mine going as well - go to the link and take a quick look, and do a search on my handle here and some of the links will have schematic links to my circuits as well as links to the original schematics that inspired this insanity.
Or, you can go here - http://www.lunarnetbbs.org/audio/myprojects/myprojects.htm
It's my web page that is still under construction, but it too has some schems.
Thanks for your link to your website. I see on your website that you have 2 versions (Cathode Bias & Parafeed). Which particular circuit did you use? I've already purchases a pair of 10Kohm OPT, 10H 500ma chokes and would like to make use of these parts.BQ
I used the "final amp" schematic with fixed bias. I did try cathode bias briefly while I was building the bias supply, but it just didn't have the punch I needed. Paul's comments on parafeed are legit even more so since you have decent output iron; I may play with parafeed since my output iron is both budget and 5k, and I have some nice PP vintage iron.
Also based on your query above, yes the original solid state power supply that I based this amp on is a PITA; look at mine (similar to Gary Kaufman's, who also helped me finish this beast). Mine is loosely based on an Altec design, and much simpler. The only change not reflected in the web site version is that I went with 3@ in series of a higher rated diode since I managed to nail my 2 (x2) diode set up twice over the last couple months.
Also, as someone mentioned to me - during the design/testing/early break in period, use fuses on the plate to output transformer connection. You do not want to toast your iron which is possible even using a variac. The +1000v range is a whole different level of design and saftey issue, please be careful!
Good start on parts collection.Just read you other responses and would like to just encourage you. Though the modern Chinease 845 is a good beast plenty of us really like the nos 211 (which is mostly available as vt4c). I wouldn't say it was time to change direction entirely and start again with the 845. Enjoy the 211 project it's a good idea. I see plenty of ideas I wouldn't carry out, this isn't one of them.
Parafeed may be impractical because of the problem finding a suitable cap. Secondly if your OT's are wound for SE they won't do parafeed justice. The parafeed boys maximise inductance of the OPT for best effect.
The 6c45pi circuits are certainly an option, there may be a better way for you. The thing is to start with the curves and determine an operating point for the 211. It is a very valid point someone made about the cost/availability of high voltage caps. Your parameters are min. 10 watts from 2 volts, 10k load, only A1, preference for high voltage.
I'll go and doodle on the 211 curves and come back.
IN brief the circuits available some mentioned here are a 6c45pi to 211 in various forms, the FI Primer style (which includes Ongaku) multiple stage then direct coupled cf driver, which I think we want to try and avoid as it isn't necessary for us. The Sukuma like 211 IT 211 style fo which there is a truly indulgant version in Sound Practices. The Camille version in Sound Practices, this is very complexed and the shunt regulation which is so integral to the design is complexed (requiring a second article). However I rather fancy that to use the valve topology of that design without the shunt regulation may become an option. That is to say a single voltage amp/driver made of parallel 6SN7 (either in srpp or Kimmel MU) maybe direct coupled to your 211. It all depends what power we can achieve from 2v after it's been through the 6sn7 stage. Do you mean 2v peak or rms? Peak would yield about 28v peak drive to the 211. I think that would be enough for at least 10 watts, but I'll have to go away and look at the curves. I'm rusty on them because I'm working with the 212 these days instead so none of this is part of my current mind set.
Paul,I really appreciate your help. At the moment i'm trying to order the CD archive 'Sound Practices' to educate me more on DIY hifi.
Preamp drives 2v RMS. Actually, it is Nelson Pass's SS "Balanced Line Stage" pre-amp i've built 2 years ago. My friend uses the same preamp to drive his 300B amp and we couldn't believe the improvement over a regular passive pot. But to go back, I made this preamp mainly because it was fully balanced to match my power amp (with XLR inputs). However, this particular pre-amp also serves as a converter from XLR to RCA or vice-versa. This is another area I wouldn't mine looking at - why... almost all tube circuits i've seen are not balanced? The response I get is "fewer parts in a tube amp... the better the sound". But what if the tube amp could benefit from reduced noise by CMRR in balanced circuits?
If you can spare some time for me in getting a schematic for me - I would be greatly in debt to you. I'm still not experienced enough to make from scratch, a la my-own-design.
Brendon
Balanced? Main benefit is in low level stages, once you've amplified signal to 2vrms maybe the benefits do nopt outweight the added complexity. That said Steve Bench has an 845 circuit which is push pull up to the 845 and then single ended. This could be adapted to retain your balanced topology right up to the 211, but it would be a lot easier to stay single ended.2vrms is quite good, 2.828v peak.
I was wrong about power out. It takes greater voltage swing than I thought. That's working with the 212 for you, it's clouded my judgement. Take the standard high voltage operating point of 1250v 60 mA into your 10k load. You can develop 13 watts from a grid drive of 60v peak (theoretical maximum just under 20 watts from 75v peak drive)
To develop 60 volts from 2.828v requires a voltage gain of 21. It's no use saying good the 6sn7 idea will get us there, because you will necver develop a voltage gain equal to the mu of the valve, and not many 6sn7's you test will actually have a mu of 20. I think you must select a valve that has a little more gain in the first place.
It's now becoming clear why the 6c45pe is populare for this application but it's not the only option, and it isn't pressed into service without some care in application (parasitic oscilation around the 6c45pe can make the resultant amp sound quite solid state like).
That said the circuits already exist and hand it to you on a plate. Buiuld it on a bread board and see how you like the sound, then try something else, to see if it can be improved upon.
The fi and Kondo schematics both rely on class A2 operation, and so also rely on cathode follower drive. This is how to get power out of a 211 at low voltages (yes sub 1kv is low voltage when discussing transmitting bottles).That said the 211 is made for a little class A2 operation.
If you prefer to stay in A1 you could adapt many schematics.
Determine how much power you want, and we'll see if that's possible in A1 and at which operating point, into which load.
When we know the quiescent bias voltage we will know the required drive voltage, and can work backwards form there. It now depends upon how much power you require at the output and how much input volatge (sensitivity) your system can provide, as to whether you will need one stage or two before the 211.
Give more info.
Hi Paul!!Power isn't really a concern for me. I will be using very efficient speakers which you can see at my website
http://www.geocities.com/super_bq/HiFi.html
I prefer to stay in A1 (full Class A operation). With 104db/1w/1m efficient Klipschorns, a few watts can go pretty loud.
Part of the reason why I was looking at the Fi is because of the 211 says "Ongaku style". That caught my attention as these amps generally sell for $50,000 and up. I dunno why (perhaps silver OPT and all that boot).
BQ
"It now depends upon how much power you require at the output and how much input volatge (sensitivity) your system can provide, as to whether you will need one stage or two before the 211."I forgot to mention that the pre-amp I plan to use is an active type. It has quite the output gain (at least 2v output).
Powerwise, i'm happy with around 10 watts but then again, i've never seen 211/VT4-C wired for that low wattage output. I guess it wouldn't do justice running such a tube under 1KV so wattage would normally be a lot higher.
Actually the power output at higher voltages in the case of the 211 is usually lower because to get power out of a 211 you must use A2. Just answering on the fly I'd expect to see perhaps as little as 15 watts, very unlikely 20 watts, but 10 watts is sufficient for your needs. This is good because it possibly allows a "better" valve choices elsewhere. There is nothing worse than having to use valves because of their parameters rather than their sound.
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