I will be constructing a two channel tube audio amplifier. With a bit of a search and because of how famous this tube is, i will be using the el34.
As far as i understand, there is no single schematic that someone can say is the best. It always depends on the availability of parts but mostly on what SUBJECTIVELY people that have already constructed amplifiers like.
My basic question is, are there any schematics that there is consensus among you, which are the top 3 in terms of availability of parts, sound quality and easy of constructing? If money is not a problem, which one should i choose that it wont need me to spend 2 years on it (it wont be super complicated), that i will listen to it and be happy about the sound and that you guys pretty much agree that it is a nice starter amplifier to have constructed.
After a few hours of researching, i see too many schematics but what is not clear is what advantage and what disadvantage one has over the other. What are my options?
For example, there is the choice between SE and PP. As far as i understand i should be looking into an SE for tweeters and medium because it has better quality but transformer is more difficult to find. PP is better for woofer though. But now i am already a bit lost. Should i go for a PP, since it is easier, and i will still be happy with the outcome or SE are really that better and i should not care about the woofer that much. Or maybe the best i could do is double up, do both, and use them separately for woofers and medium/tweezers.
Any other choices like that? What options are there about the preamp? Something else you would like to add?
Edit1: What about the term ultralinear?
Thank you very much for your time!
P.S. Which is that one book i should read before i start?
As far as i understand, there is no single schematic that someone can say is the best. It always depends on the availability of parts but mostly on what SUBJECTIVELY people that have already constructed amplifiers like.
My basic question is, are there any schematics that there is consensus among you, which are the top 3 in terms of availability of parts, sound quality and easy of constructing? If money is not a problem, which one should i choose that it wont need me to spend 2 years on it (it wont be super complicated), that i will listen to it and be happy about the sound and that you guys pretty much agree that it is a nice starter amplifier to have constructed.
After a few hours of researching, i see too many schematics but what is not clear is what advantage and what disadvantage one has over the other. What are my options?
For example, there is the choice between SE and PP. As far as i understand i should be looking into an SE for tweeters and medium because it has better quality but transformer is more difficult to find. PP is better for woofer though. But now i am already a bit lost. Should i go for a PP, since it is easier, and i will still be happy with the outcome or SE are really that better and i should not care about the woofer that much. Or maybe the best i could do is double up, do both, and use them separately for woofers and medium/tweezers.
Any other choices like that? What options are there about the preamp? Something else you would like to add?
Edit1: What about the term ultralinear?
Thank you very much for your time!
P.S. Which is that one book i should read before i start?
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PP has better quality than SE, if by 'better' you mean the output signal is more like the input signal. If by 'better' you mean 'I prefer it' then you need to listen and discover what you like.
Most modern systems do not need a preamp, just a volume control.
Ultralinear is a type of output stage, which is said to combine some of the advantages of triode and pentode operation.
A good EL34 PP amp is the Mullard 5-20, although that is an old design. There is a modern version of it by Claus Byrith.
Most modern systems do not need a preamp, just a volume control.
Ultralinear is a type of output stage, which is said to combine some of the advantages of triode and pentode operation.
A good EL34 PP amp is the Mullard 5-20, although that is an old design. There is a modern version of it by Claus Byrith.
DF96 thank you very much for your reply. By better i mean "the output signal is more like the input signal" so there is that. I narrow my searches towards PP!
When you say they dont need a preamp but just a volume control, is for example a vinyl pickup enough to drive such an amplifier?
But do you consider ultranlinear a good or bad choice or again it depends on the taste of who builds and listens to the amp?
When you say they dont need a preamp but just a volume control, is for example a vinyl pickup enough to drive such an amplifier?
But do you consider ultranlinear a good or bad choice or again it depends on the taste of who builds and listens to the amp?
Mullard style circuitry is both "classic" and "idiot resistant". 
However, the small signal types found in the 5-20 reflect sales objectives more than they reflect technical excellence. 
Both the EF86 and 12AX7/ECC83 are high RP/low gm and that's not good in a circuit with a GNFB loop. The H/K Citation V is a superior implementation of Mullard style circuitry, where attention was paid to technical excellence in the small signal complement. It certainly is possible to use H/K's small signal setup in combination with UL mode EL34 "finals".
The 12BY7 shown is getting scarce. I've provided a 6922 (in production) cascode that will substitute for the video pentode.
However, the small signal types found in the 5-20 reflect sales objectives more than they reflect technical excellence. Both the EF86 and 12AX7/ECC83 are high RP/low gm and that's not good in a circuit with a GNFB loop. The H/K Citation V is a superior implementation of Mullard style circuitry, where attention was paid to technical excellence in the small signal complement. It certainly is possible to use H/K's small signal setup in combination with UL mode EL34 "finals".The 12BY7 shown is getting scarce. I've provided a 6922 (in production) cascode that will substitute for the video pentode.
Attachments
Global feedback is quite compatible with high impedance valves such as ECC83. Indeed, it could be that the limited frequency response of the basic valve circuit reduces the need for extra compensation. However, let us not clutter this thread with that argument.
A system with a turntable will need a phono preamp.
Personally I like the UL design, but not everybody does.
A system with a turntable will need a phono preamp.
Personally I like the UL design, but not everybody does.
Low gm leaves the small signal setup vulnerable to HF error correction signal induced slew limiting. The high RP 'X7 triode is a poor candidate for driving UL mode O/P tubes. If the O/P tubes are full pentode, the 'X7 triode can be OK. In any event, the 6CG7/6FQ7 is a better driver of O/P tubes.
You mentioned a book to read, this is a "classic" I believe? http://mirror.thelifeofkenneth.com/...gn_G.E._Valve-Electronics_Dept._1957_text.pdf
I borrowed this from the library, more up to date and comprehensive Used Valve Amplifiers on OnBuy
I borrowed this from the library, more up to date and comprehensive Used Valve Amplifiers on OnBuy
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As a self-declared 'newbie', perhaps you might consider a kit? Taking a look at a kit may, at least, help clarify your thoughts. There's an affordable PP-EL34 kit available from this Helsinki company:
https://en.uraltone.com/kits/hi-fi-kits/uraltone-stereo-hifi-pp-el34-v2-0-tube-amp-kit.html
Uraltone PP EL34 | Inner Magazines
https://en.uraltone.com/kits/hi-fi-kits/uraltone-stereo-hifi-pp-el34-v2-0-tube-amp-kit.html
Uraltone PP EL34 | Inner Magazines
Good one. Basic electronics volumes 1-6 by Van Valkenburgh are a classic too, albeit a basic primer rather than audio specific. Nonetheless very useful, and even has fun pictures. Tubes and Circuits (and the rest of Bruce’s books) is good as well. As a total newbie I’d recommend a kit from a reputable vendor over attempting a full DIY effort. It can get hairy. For example:
Transcendent Sound Products
Or, Bottlehead, Oddwatt, Elekit et al. Or what I think would be the best ( least expensive / most versatile / most forum supported ) option: the Baby Huey EL34, inquire with member Prasi re group buy boards. It supports a variety of configurations, tubes, including UL output.
You can decide for yourself and experiment.
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The question that should be asked is what speakers you plan to use this with. If they're horn-loaded with 100 dB efficiency, you have a lot more to choose from than if you have 87 dB 4 ohm speakers that dip down to 3 ohms around 40hz.
I know I'm going to get a lot of flak for suggesting an ST70, but Dynakitparts does carry new ST70 and ST35 kits. While few of us would argue that it's the "best" design ever, the iron is excellent and there's a lot of resources online if you run into trouble. Lots of people love they way they sound too.
If you do choose to go with a Mullard topology EL34 design, the A470 transformers from Dynakitparts are a pretty nice option for a 4.3K primary impedance.
H713
I know I'm going to get a lot of flak for suggesting an ST70, but Dynakitparts does carry new ST70 and ST35 kits. While few of us would argue that it's the "best" design ever, the iron is excellent and there's a lot of resources online if you run into trouble. Lots of people love they way they sound too.
If you do choose to go with a Mullard topology EL34 design, the A470 transformers from Dynakitparts are a pretty nice option for a 4.3K primary impedance.
H713
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