For what it's worth, I've walked this exact path and I ended up designing a Williamson topology amplifier with 12AX7, 12AU7 and 2 X KT88 per channel. Using Fixed Bias on the output and B+ of 560V I measure 80 watts per ch in class AB, ultralinear. I used the Hammond 1650R OPT.
I used also negative feedback, using filtering in the NFB to eliminate high-frequency ringing.
Happy to share thoughts, lessons, ideas etc
I used also negative feedback, using filtering in the NFB to eliminate high-frequency ringing.
Happy to share thoughts, lessons, ideas etc
Hi DutchyMX,
I think there are 2 important questions to ask yourself at this point. 1) how much you time do you want the build to take?
2) how much time are you willing to invest in tuning and troubleshooting to get the right result.
I would say there are basically 3 paths: Scratch build Semi kit Full kit
Scratch build will potentially give the best result in the long run but will certainly take the most time. It also has the possibility of never getting the right result if you technical skills, knowhow or tools are lacking in some way.
Semi kit combines the best of both worlds; lower cost than a full kit, a bit more flexibility but also a lot more certainty in the final result.
Tubelab | Dedicated to advancing the state of the art in affordable high end audio. would be a good example and possibly the best option down this path. I have not yet built any of these ( I intend to) but the pcbs should make construction straight forward, the designs are bullet proof and the documentation is extensive, as is the forum support. I fully intend to invest down this path in the coming years.
Full kit is the low risk option. A bit more expensive as you are paying not just for the Intellectual property as in the semi kit option but also the time and margin for the kit pieces, presumably instructions as well. This option does however "guarantee" a good result as everything should work perfectly if you follow the instructions properly. A good example here is these guys: tubes4hifi amplifier KITs page
I have personally built a pair of the big M125 monoblocks which are bloody awesome (horrendous to ship across the pacific but you won't suffer that) and an SP14 preamp Vacuum Tube Audio preamp kits which is equally impressive. These kits aren't cheap but the designs are great, parts quality excellent and support equally good. I can personally recommend these.
I would also recommend buying parts/kits from a western source if possible. Some of the Chinese stuff is fantastic but some of it is not. Its inherently a risky business getting stuff off ebay as things like documentation are typically non-existant. I have bought things from ebay with success but only non critical bits and I am expecting to throw away supplied parts.
PS: welcome to tube audio, where the good sound is found.
Also the other question is are you willing to go into a component setup with a separate preamp or does it all have to go into one box?
Separate preamp gives a heck of a lot more flexibilty but at the cost of more space.
I think there are 2 important questions to ask yourself at this point. 1) how much you time do you want the build to take?
2) how much time are you willing to invest in tuning and troubleshooting to get the right result.
I would say there are basically 3 paths: Scratch build Semi kit Full kit
Scratch build will potentially give the best result in the long run but will certainly take the most time. It also has the possibility of never getting the right result if you technical skills, knowhow or tools are lacking in some way.
Semi kit combines the best of both worlds; lower cost than a full kit, a bit more flexibility but also a lot more certainty in the final result.
Tubelab | Dedicated to advancing the state of the art in affordable high end audio. would be a good example and possibly the best option down this path. I have not yet built any of these ( I intend to) but the pcbs should make construction straight forward, the designs are bullet proof and the documentation is extensive, as is the forum support. I fully intend to invest down this path in the coming years.
Full kit is the low risk option. A bit more expensive as you are paying not just for the Intellectual property as in the semi kit option but also the time and margin for the kit pieces, presumably instructions as well. This option does however "guarantee" a good result as everything should work perfectly if you follow the instructions properly. A good example here is these guys: tubes4hifi amplifier KITs page
I have personally built a pair of the big M125 monoblocks which are bloody awesome (horrendous to ship across the pacific but you won't suffer that) and an SP14 preamp Vacuum Tube Audio preamp kits which is equally impressive. These kits aren't cheap but the designs are great, parts quality excellent and support equally good. I can personally recommend these.
I would also recommend buying parts/kits from a western source if possible. Some of the Chinese stuff is fantastic but some of it is not. Its inherently a risky business getting stuff off ebay as things like documentation are typically non-existant. I have bought things from ebay with success but only non critical bits and I am expecting to throw away supplied parts.
PS: welcome to tube audio, where the good sound is found.
Also the other question is are you willing to go into a component setup with a separate preamp or does it all have to go into one box?
Separate preamp gives a heck of a lot more flexibilty but at the cost of more space.
Chris, I appreciate your feedback, and yes, I could have been killed alright. But then again, I was 15 yo for the love of god. If I knew then what I know now it would be totally different. And that teacher should have been fired, except that I never said anything. And thats totally on me.
Anyway, also to you, all the best for the new year!
Robin
Lets see. One time at 360V, 4 times at 240V and 3 times at 110V. That is 8 life. To get 50W, you will need around 560V DC. Take care of your remaining one
Oehh.....I´ll keep that in mind
I have to second the tubes4hifi.com ST-120. I don't think you can do better DIY sourcing your own parts. Plus it is a proven design with lots of builders and support. Good iron, and the ability to run Triode or Pentode. The auto-bias board looks interesting too. My concern is that a single 5AR4 may have a short life.
Good luck with your intentions to build only 1 amp - I said the same thing 6 amps ago
I just finished a push-pull stereo amp using 7581-A power tubes. These are very similar to 6L6GCs except the plate dissipation rating is a bit higher. It is outputting just north of 57 watts on the inputs of the OPTs (48 watts on the OPT outputs into a 8 ohm load) so this design might work for you.The design is straight forward, I am using a 12AY7 for the pre-amp stage and a 12AV7 for the driver/phase inverter stage. The 3 dB down points are 8 Hz and 25 kHz. My focus with this amp was the power supply and i spent a lot of time understanding how the PS impacts the music. Again nothing sophisticated but i got the best reservoir/smoothing electrolytics I could find at Mouser (but nothing exotic) and modeled the circuit using PSU Designer II which is a download from Duncan Amps. The power transformer is a Hammond and the OPTs are from Edcor - very happy with both. The rectifier is a pair of Schottky diodes (CREE) used in a full wave configuration. The screen grid is regulated using a Maida circuit - Pete Millett has a great PCB for this (you still need to figure out the values and buy the parts). I also tried biasing the 12AY7 in the pre-amp with a low power LED instead of a resistor on the cathode, this is working very nicely and provides a bias point of 1.87 V. The Driver/phase inverter stage is a Long Tailed Pair configuration and can easily provide the 75 V needed to drive the 7581-As to full power. The 7581-As are fixed biased at ~-37 V, to get the quiescent current to 42 mA for each tube. Nothing in this amp is exotic or boutique, all parts were sourced from either Mouser or Digi-key except for the tubes, OPTs and the high voltage regulator PCB from Pete Millett.
One thing I would echo from previous posts is safety - I would have to agree, you have been shocked too many times. The voltages in tube equipment are lethal and you don't get a re-do. TubeLab has a great section on the Tubelab website on safety, take the time to go over it. My workshop is a 8 ft by 12 ft shed on it's own GFI breaker. The floor is 3/4 inch foam sandwiched between 2 layers of plywood (more to keep warm in the Upstate NY winters than anything else), but it is never ever wet and there is no concrete or metal. The GFI is not a guarantee either, the electrons move faster than that breaker can open, it comes down to being very careful.
As for books, I have many but the three that have been most useful are "Designing Valve Amplifiers" by Morgan Jones and the two books that Merlin Blencowe has published "Designing Tube Preamps for Guitar and Bass" and "Designing High-Fidelity Tube Preamps".
Finally, I agree a kit might be a good place to start if only to educate yourself. I started with a cheap kit (K-8LS) - it did not sound very good but I learned a lot. In parallel you should spend the time to really understand the building blocks of a tube amp then do your from scratch build - you will end up with a great amp that is optimized for you.
I just finished a push-pull stereo amp using 7581-A power tubes. These are very similar to 6L6GCs except the plate dissipation rating is a bit higher. It is outputting just north of 57 watts on the inputs of the OPTs (48 watts on the OPT outputs into a 8 ohm load) so this design might work for you.The design is straight forward, I am using a 12AY7 for the pre-amp stage and a 12AV7 for the driver/phase inverter stage. The 3 dB down points are 8 Hz and 25 kHz. My focus with this amp was the power supply and i spent a lot of time understanding how the PS impacts the music. Again nothing sophisticated but i got the best reservoir/smoothing electrolytics I could find at Mouser (but nothing exotic) and modeled the circuit using PSU Designer II which is a download from Duncan Amps. The power transformer is a Hammond and the OPTs are from Edcor - very happy with both. The rectifier is a pair of Schottky diodes (CREE) used in a full wave configuration. The screen grid is regulated using a Maida circuit - Pete Millett has a great PCB for this (you still need to figure out the values and buy the parts). I also tried biasing the 12AY7 in the pre-amp with a low power LED instead of a resistor on the cathode, this is working very nicely and provides a bias point of 1.87 V. The Driver/phase inverter stage is a Long Tailed Pair configuration and can easily provide the 75 V needed to drive the 7581-As to full power. The 7581-As are fixed biased at ~-37 V, to get the quiescent current to 42 mA for each tube. Nothing in this amp is exotic or boutique, all parts were sourced from either Mouser or Digi-key except for the tubes, OPTs and the high voltage regulator PCB from Pete Millett.
One thing I would echo from previous posts is safety - I would have to agree, you have been shocked too many times. The voltages in tube equipment are lethal and you don't get a re-do. TubeLab has a great section on the Tubelab website on safety, take the time to go over it. My workshop is a 8 ft by 12 ft shed on it's own GFI breaker. The floor is 3/4 inch foam sandwiched between 2 layers of plywood (more to keep warm in the Upstate NY winters than anything else), but it is never ever wet and there is no concrete or metal. The GFI is not a guarantee either, the electrons move faster than that breaker can open, it comes down to being very careful.
As for books, I have many but the three that have been most useful are "Designing Valve Amplifiers" by Morgan Jones and the two books that Merlin Blencowe has published "Designing Tube Preamps for Guitar and Bass" and "Designing High-Fidelity Tube Preamps".
Finally, I agree a kit might be a good place to start if only to educate yourself. I started with a cheap kit (K-8LS) - it did not sound very good but I learned a lot. In parallel you should spend the time to really understand the building blocks of a tube amp then do your from scratch build - you will end up with a great amp that is optimized for you.
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