The GM70 is another choice to consider, widely available and pretty inexpensive. I'm currently working on an IT coupled GM70 design after abandoning a design based on the 211 which at the time was getting hard to find new.. One set of vintage VT4C in my possession did not give me sufficient confidence.. They're a bit easier to get now, but cost a lot more than they used to.
Hello Bas & kevinkr
Well I havn´t got the actual tubes yet but I was thinking of going for transmitter like tubes. I have a set amp based on GM70 already so Im happy in that matter. Yes, 211 are somewhat scarse so maybe 845´s are a better choice. I could go PP but I hear this wears the tubes more than SE so I think I will settle for SE. Mercury vapor rectifiers would be great in the PS.
So if you know of a schematic I would be grateful
Cheers
Well I havn´t got the actual tubes yet but I was thinking of going for transmitter like tubes. I have a set amp based on GM70 already so Im happy in that matter. Yes, 211 are somewhat scarse so maybe 845´s are a better choice. I could go PP but I hear this wears the tubes more than SE so I think I will settle for SE. Mercury vapor rectifiers would be great in the PS.
So if you know of a schematic I would be grateful
Cheers
PP operation does not in any sense negatively impact tube life, SE operation actually is harder on a given output tube because you generally run class A at very high currents in order to get reasonable linearity. PP amps can be run at much lower quiescent currents and can produce > 4 X the power of a single SE output tube operating at similar voltages and currents.
I personally prefer SE amplifier designs sonically speaking, however to say that PP configuration is harder on a tube than SE is just not true.
Not a big fan of MV rectifiers, see this thread for why: http://www.diyaudio.com/forums/tube...g-866a-powersupply-schematic.html#post2231466
Ok, this is good news about PP and tube life....read something somewhere about this puting stress on the tubes. MV rectifiers are a bit dodgy but I like them, this is not a must have. I found a schematic, se link, -what do you think of it?How Hashimoto Sounds
Cheers
Cheers
Another amp to look at is the Tim Mellow 25wpc 6C33C OTL. I tried to attache the write up but it is too big. Email me at djnagle@comcast.net if you want a copy. Cheers.
I have 211's and 845's in both vintage American and new production Chinese. My amp can use either tube. I have also tried triode wired 813's and 833A's in it. I have not used the GM70.
IIRC the 813 has a 750 volt screen rating. That didn't stop me from running some old RCA's at 1050 volts in my amp. They don't sound bad either.
211's are a nice sounding tube and they will make about 35 watts in A2. The Chinese tubes sound pretty decent and are still available for abouy $50 each. The 211 needs more drive voltage than a triode wired 813.
The 845 is the bad boy of the bunch. I get just over 40 WPC out of my amp in A2 with 1050 volts on the plate. These tubes have the best sound but require a big bunch of drive voltage, well over 200 volts P-P. I have old RCA and GE's but I won't push them past 70 mA of bias current. They sound really good on the typical music played on SE amps. Want to rock, or even play some techno....Plug in the Chinese tubes and crank the bias up....way up. The bass gets real tight and well defined at about 110 mA. Over the line? Yes, but nothing bad happens, just good fat sound. I think that the 845's have more left in them but my power supply doesn't. It uses 5AR4's in a voltage doubler configuration with a 480 volt industrial transformer.
Remember amps like this use KILLER voltage levels, and OPT's don't come cheap. I got real lucky with the OPT's. I got a pair from the Ebay seller that ripped off most people. They work pretty good and haven't blown up yet. I also bought a few Chinese tubes when they were $26 each.
The 833A, forget it unless you have a lot of cash, and a big house with plenty of AC. You will need a custom OPT too. I gave up when I realized that I fell short on all 3 counts. The test amp made about 200 watts though.
IIRC the 813 has a 750 volt screen rating. That didn't stop me from running some old RCA's at 1050 volts in my amp. They don't sound bad either.
211's are a nice sounding tube and they will make about 35 watts in A2. The Chinese tubes sound pretty decent and are still available for abouy $50 each. The 211 needs more drive voltage than a triode wired 813.
The 845 is the bad boy of the bunch. I get just over 40 WPC out of my amp in A2 with 1050 volts on the plate. These tubes have the best sound but require a big bunch of drive voltage, well over 200 volts P-P. I have old RCA and GE's but I won't push them past 70 mA of bias current. They sound really good on the typical music played on SE amps. Want to rock, or even play some techno....Plug in the Chinese tubes and crank the bias up....way up. The bass gets real tight and well defined at about 110 mA. Over the line? Yes, but nothing bad happens, just good fat sound. I think that the 845's have more left in them but my power supply doesn't. It uses 5AR4's in a voltage doubler configuration with a 480 volt industrial transformer.
Remember amps like this use KILLER voltage levels, and OPT's don't come cheap. I got real lucky with the OPT's. I got a pair from the Ebay seller that ripped off most people. They work pretty good and haven't blown up yet. I also bought a few Chinese tubes when they were $26 each.
The 833A, forget it unless you have a lot of cash, and a big house with plenty of AC. You will need a custom OPT too. I gave up when I realized that I fell short on all 3 counts. The test amp made about 200 watts though.
Hi h00hbt,
I built Andrea Ciuffoli's 845 in stereo configuration.
New 845 amp.
If you are interested you can have a look at my amp here -
http://www.diyaudio.com/forums/tubes-valves/141471-845-progress-so-far.html
Andrea is often seen around here. He is well respected and quite innovative. His 845 amplifier sounds great and in my opinion is well designed. It is by far my favourite amplifier.
Great fun to build as well.
Cheers,
Rob
I built Andrea Ciuffoli's 845 in stereo configuration.
New 845 amp.
If you are interested you can have a look at my amp here -
http://www.diyaudio.com/forums/tubes-valves/141471-845-progress-so-far.html
Andrea is often seen around here. He is well respected and quite innovative. His 845 amplifier sounds great and in my opinion is well designed. It is by far my favourite amplifier.
Great fun to build as well.
Cheers,
Rob
Unless you are in a real love affair with your chiropractor, I'd strongly advise against a stereo 211/845 amp. Such a monster would need a forklift to shift any distance, and even moving it around on the bench would be more than I want to do, not being into body building.
Monoblock is a far more intelligent way to go, IMO. Each half the weight and half the heat concentration.
Regards, Allen
Monoblock is a far more intelligent way to go, IMO. Each half the weight and half the heat concentration.
Regards, Allen
It's Ok if you get a clean lift, and your back's OK, but when you have to twist and lift, and juggle it into a rack or a corner - Nein Danke!
I build a 150 watt 4 x KT88 monoblck, can carry one in each hand...but with Lundalh iron, not EI boat anchours.
Regards, Allen
Of course in Australia, we don't really worry too much about weight. We are quite used to lifting things - sheep, cows and other small animals. Having said that, I do concede that the women (especially in the last trimester of pregnancy) usually leave anything heavier than an engine block for the guys. However, if weight is an issue you should plan on 30-40kg for a stereo 845 amplifier.
Rob
20w SE amp can handle most speakers, depend on amp's sensitive,normal listening 5w is good enough for a big room.211/845 in SE out put can be only 10 to 20w and price are high compare to it's quality. try 838 805 810 in positive bias drive, they can easily to have 35 to 50w, but they need interstage to couple and out put transformer will be a very big one too, separate power supply can help to move them more easy.866A is the best sounding rectifier but you need two for full wave and 2.5v 10A transformer for it's filament that makes more heavy
tony ma
tony ma
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