I'm been playing with doing a tube headphones amplifier, haven't really been able to find anything I really like....
The design parameters are:
1) Single Ended / Balanced inputs, preferable balanced all the way....
2) Push Pull transformer coupled with no DC (Parafeed).
3) As few capacitors as possible, preferable with no large currents though them.
4) Great tubes, but low cost and easily available.
5) Able to drive any headphones, with plenty of power.
6) Fully Class A with no feedback.
7) Design tolerant of tube manufacturing variations.
8) Volume control is optional as it's supposed to be driven by Soekris DAC.
This is the principles I've come up with so far, see attached schematics:
Differential input amplifier using low mu ECC82 low noise tube driving differential output amplifier using ECC99 driver tube, with constant current load. Output transformer can then be smaller and cheaper as there is no DC current in it, although it cost a little in added power consumption. Current sources are all precise and balanced, with ECC99 load resistors to set DC operating point. Transformer output can be set to drive low or high output impedance. Tried first to keep it single stage, but just couldn't get enough gain....
Although I'm a pretty experienced analog and digital designer I don't have any experience all all with tubes.... So I would like some feedback, to avoid any grave mistakes
But it do look good in ltspice....
Biggest question for far is the output transformer, Lundahls seems great but are expensive, so in I'm looking around, even considering toroids for output transformer, probably need to be custom design....
Tubes are another major consideration (off course), but after much research I think my current choice is good, with plenty of options for alternatives.
Once I move forward with the rest of the design, I plan to do a compact low profile design, with a nice alu case, fully documented and offered as DIY kit at reasonable cost, if there are interest....
The design parameters are:
1) Single Ended / Balanced inputs, preferable balanced all the way....
2) Push Pull transformer coupled with no DC (Parafeed).
3) As few capacitors as possible, preferable with no large currents though them.
4) Great tubes, but low cost and easily available.
5) Able to drive any headphones, with plenty of power.
6) Fully Class A with no feedback.
7) Design tolerant of tube manufacturing variations.
8) Volume control is optional as it's supposed to be driven by Soekris DAC.
This is the principles I've come up with so far, see attached schematics:
Differential input amplifier using low mu ECC82 low noise tube driving differential output amplifier using ECC99 driver tube, with constant current load. Output transformer can then be smaller and cheaper as there is no DC current in it, although it cost a little in added power consumption. Current sources are all precise and balanced, with ECC99 load resistors to set DC operating point. Transformer output can be set to drive low or high output impedance. Tried first to keep it single stage, but just couldn't get enough gain....
Although I'm a pretty experienced analog and digital designer I don't have any experience all all with tubes.... So I would like some feedback, to avoid any grave mistakes
But it do look good in ltspice....Biggest question for far is the output transformer, Lundahls seems great but are expensive, so in I'm looking around, even considering toroids for output transformer, probably need to be custom design....
Tubes are another major consideration (off course), but after much research I think my current choice is good, with plenty of options for alternatives.
Once I move forward with the rest of the design, I plan to do a compact low profile design, with a nice alu case, fully documented and offered as DIY kit at reasonable cost, if there are interest....
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Hi Soren,
I have built a number of tube headphone amplifiers but am far from being an expert.
I had a go at a PushPull headphone amp myself a few years back, though not parafeed --> see attachment.
It used inexpensive russian tubes that were easily available (6N6P is similar to ECC99) and generic toroids as output transformers...
amp was working on a breadboard but I eventually abandonned the idea.
There are a few custom winders around Europe... for instance AE Europe in the Netherlands who used to do good transformers of all kinds.
AE transformatoren specialist in transformatoren voor de elektrotechnische industrie
Maybe they can set you up with what you need.
I have built a number of tube headphone amplifiers but am far from being an expert.
I had a go at a PushPull headphone amp myself a few years back, though not parafeed --> see attachment.
It used inexpensive russian tubes that were easily available (6N6P is similar to ECC99) and generic toroids as output transformers...
amp was working on a breadboard but I eventually abandonned the idea.
There are a few custom winders around Europe... for instance AE Europe in the Netherlands who used to do good transformers of all kinds.
AE transformatoren specialist in transformatoren voor de elektrotechnische industrie
Maybe they can set you up with what you need.
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Could be a possibility, some of their their PCB mounted parts fits, will probably to do PCB with multiple footprints....
Most of their parts say "built to order", so I should be able to get exactly what I want, and shipping is no problem with a little qtys....
Your design is not that far from mine... I'm using the european types, just because I'm european, but new ones are available.... Comparable russian type should fit, I'm also looking at the 6H30P, but haven't been able to find a working model for ltspice....
The dutch transformer manufacturer looks interesting, unfortunately most of their limited info website is in dutch, and although danes are often confused with dutch, I don't understand dutch. But I will contact them for more info.
Wonder what result you got from a generic toriod, especially sound wise, I have been thinking about trying one, those small telema PCB mounted are cute....
I know, but most transformer companies don't have that large qty requirement for custom parts....
6H30P is very expensive, they used to run from 25€ up, a piece.
I would never confuse the Danes with Dutch
, but AE used to have an english page. But I haven't been on their site for years.I got most of the info about using toroids from DIYA member 'Shoog'... but then I didn't have my amp playing long enough to have
a real verdict about the sound.
I'm aware of the "perfect" simulations.... I will check tolerances later on, please note that I can make very precise and matched constant current generators. But if needed I will add active balancing, and maybe make space for a capacitor between the two primaries....
Hello Soekris ,
i have build 6n6p headphone amps in several variations, ended up with a 300b SE setup. With sounded the best for years. 5 years ago i build a "wire" variation with sounded overall as good as the 300b SE amp but with more bass controll. So for me no tubes in my headphone amp. I use akg 7xx special edition. The wire design i made has all the things you may expect from a tubestage but with better bass controll.
http://www.diyaudio.com/forums/headphone-systems/246914-just-fun.html
Building tube amps is still my passion, hope you will try my experience with the wire amp.
Ronny
i have build 6n6p headphone amps in several variations, ended up with a 300b SE setup. With sounded the best for years. 5 years ago i build a "wire" variation with sounded overall as good as the 300b SE amp but with more bass controll. So for me no tubes in my headphone amp. I use akg 7xx special edition. The wire design i made has all the things you may expect from a tubestage but with better bass controll.
http://www.diyaudio.com/forums/headphone-systems/246914-just-fun.html
Building tube amps is still my passion, hope you will try my experience with the wire amp.
Ronny
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PP headamp? I see no benefit, rather more problems.
For example cross-over distortion, which does not exist in SE.
Since you´re taking mW´s, most likely end stage will always stay in this grey area.
Even small SE https://frank.pocnet.net/sheets/021/7/71A.pdf can blow headphones off
http://www.lundahl.se/wp-content/uploads/datasheets/1689.pdf is multipurpose, 18 : (4)(2)(1) will cover any headphones impedance.
For example cross-over distortion, which does not exist in SE.
Since you´re taking mW´s, most likely end stage will always stay in this grey area.
Even small SE https://frank.pocnet.net/sheets/021/7/71A.pdf can blow headphones off
http://www.lundahl.se/wp-content/uploads/datasheets/1689.pdf is multipurpose, 18 : (4)(2)(1) will cover any headphones impedance.
I have semiconductor ones in the works too that will beat anything, but tubes are just for fun and maybe to see how far you can get with those tubes with a little more modern design....
It say fully class A, so no crossover distortion.... Fully balanced give more power with cheap tubes and eliminate or reduce a lot of noise problems.
I do not understand, are you making a speaker amp??
What "more power" you´re talking about ?
Just to get it straight:
This design I'm working on is a fully balanced push-pull fully class A tube headphone amplifier that can drive any headphones.
I'm not interested in discussing if it should be single ended, class AB, transistors, mosfets, IC's, without transformer or other technologies....
I'm posting in the tube section to get qualified feedback as this is my first tube design and I want it to be as good as possible without resorting to very expensive or rare parts.
If it ends up as a finished design all details will be published and I will probably offer PCB's will all SMT mounted and a kit.
This design I'm working on is a fully balanced push-pull fully class A tube headphone amplifier that can drive any headphones.
I'm not interested in discussing if it should be single ended, class AB, transistors, mosfets, IC's, without transformer or other technologies....
I'm posting in the tube section to get qualified feedback as this is my first tube design and I want it to be as good as possible without resorting to very expensive or rare parts.
If it ends up as a finished design all details will be published and I will probably offer PCB's will all SMT mounted and a kit.
I believe that's the primary weakness of this design, because this type of transformer is extremely sensitive to DC bias, and once the core is magnetized, it will generate excessive distortion until it's completely degaussed. Note that no tolerance is given for primary DC bias current on Lundahl's datasheet. Unfortunately, fixing the design with trimmers may not be successful long-term.
Have you seen the torpedo headphone amp? It is a well thought parafeed design, check here the latest design:
TORPEDO III Assembled, Beezar Audio
TORPEDO III Assembled, Beezar Audio
Since this is just for headphone, you can do with just one stage. Are you fixated in parafeed? If you can relax that requirement a bit, here's a good simple design with not a cap in sight, except for the usual PS cap.
DIY 6DJ8 (ECC88) Tube Hi-Fi Headphone Amplifier Project
If worried about DC standing current, put a trimpot above the CCS.. or use separate CCS for each cathode (as per your output stage design) and AC couple them together, like so:
http://www.diyaudio.com/forums/tube...mple-el84-rise-anti-triode-2.html#post1908133
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