It is pretty exciting, as Andy points out, that you may be creating a next performance step in this design for people to upgrade their amps. And from the sound of this thread even inspiring some to try other ideas with it.
I'm thinking there will be more home built 300B amps with this series out there.
Whenever I see someone ask about a schematic, the responses for the same design tend to vary from "It is great" to "that design is terrible"; so it is incredibly helpful to see a design picked, examined, built, tested and then refined like this. It adds a lot more confidence when duplicating the final build and even if someone doesn't copy this build they will take away tips for future builds.
Your method of taking us along the entire journey makes these videos some of the most useful out there.
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Designing the perfect 300b SE amp is like climbing the North Face of the Eiger. It's a notorious summit where many challenges stand in your way. It's been done well by several designers, but using cheap and widely available tubes and parts is one of the challenges. You can solve some of the issues by throwing money at them - better tubes, boutique iron etc. You can also throw a lot of ingenious solid state at it. But a good amplifier can be built within budget with the right design. It takes some thought, though, and the "usual suspects" for driver tubes may not be ideal. Using the familiar commercial tubes cuts out some interesting rarer tubes like all the Russian ones.
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Actually my next build is a pair of Untralinear PP 6BQ5 monoblocks loosely based off the Dyna ST35. I have the iron and most of the parts. I plan to start on that soon. Again, these are supposed to sound great, but I'm going into this with eyes wide open, critically examine it and am ready to change course if needed to get something I believe sounds great.
The other build I want to do in detail is my own design 6SQ7-EL34 SE UL amp. It can be build on a real budget, uses less than $100 worth of tubes, some 15W Edcor iron, and honestly is my reference amplifier for "what sounds good". Everyone who has heard it is absolutely blown away and it's using some old AM radio tubes as the driver and some JJ EL34 for the output. There is nothing exotic at all, it just delivers.
My personal goal with this build was to build something to use this pile of 6SN7 tubes I have. I'm excited that with a couple of resistors and moving a few wires around, it transformed what I started with, delivering 3X the power before clipping. Maybe someone else can figure out how to "fix" that direct coupled mess, but this change I made removes a cathode resistor/bypass cap, removes one inversion of the signal so it acts like a 2 stage amp now, and it sounds better. That's a win in my book!
thanks for confirming, it was PRR who said the el84 is a mighty fine pentode, but a lame triode....
I wouldn't say that. I have an EL84 PP amplifier with the output tubes run in triode mode. Initially, I had tried running them in ultra-linear mode with some feedback, but the sound was lifeless, dark and muddy. After that, I run them in petnode mode, again with feedback, but again I didn't like it. Only after I connected them in triode mode without feedback the amp became alive.
Perhaps, you are referring to triode connected when used as a driver, but I never tried that.
I did a shootout with various pentodes in triode as drivers and this was my rank order of best to worst:
1. EL33/PL33 - warm. lush, liquid, detailed, good bass, good voices, 3D
2. EL11 - neutral/warm, detailed, good bass, good voices, 3D
3. KT81/KT61 - pleasant, involving, good voices, slightly less detail
4. EL41 - very like KT61, voices slightly harder, focussed, less involving
5. E80L - focussed, neutral, clean, smooth, detailed but cold/flat, less involving
6. EL84 - clear, clean, not as good as the above
7. 6V6 - as EL84
EL33 and EL11 were very close and very satisfying. The most holographic of the valves. There was a perceptible drop to KT61 and a bit more to EL41, though these were both good. E80L was good, had very nice treble and detail but was rather cold and uninvolving, particularly on voices where the other valves excelled. EL84/6V6 were OK but not as interesting as those above them.
The EL3n was not tried, but is a predecessor and close equivalent of the EL33
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1. EL33/PL33 - warm. lush, liquid, detailed, good bass, good voices, 3D
2. EL11 - neutral/warm, detailed, good bass, good voices, 3D
3. KT81/KT61 - pleasant, involving, good voices, slightly less detail
4. EL41 - very like KT61, voices slightly harder, focussed, less involving
5. E80L - focussed, neutral, clean, smooth, detailed but cold/flat, less involving
6. EL84 - clear, clean, not as good as the above
7. 6V6 - as EL84
EL33 and EL11 were very close and very satisfying. The most holographic of the valves. There was a perceptible drop to KT61 and a bit more to EL41, though these were both good. E80L was good, had very nice treble and detail but was rather cold and uninvolving, particularly on voices where the other valves excelled. EL84/6V6 were OK but not as interesting as those above them.
The EL3n was not tried, but is a predecessor and close equivalent of the EL33
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Comparing Eight Tubes For Low Power Amplifiers Article Submitted By Mike Zivkovic Of Teresonic
The above was another shootout of pentodes in triode. Rank order was
1. EL3n (predecessor of EL33)
2. E80L
3. 6973
Other tubes tried were as follows:
"The tubes fell into three categories: "yawn", "very nice", and "great". In the "yawn" category is the 807 tube. I can't recommend this tube in triode mode at all. The RCA manual doesn't recommend it either, and now I know why. It doesn't even work for background listening.
In the "very nice" category are all the 6V6 style beam power tubes. It was hard to find a distinct difference between the 6AQ5, 6V6, and 6L6. This is not surprising since they all have very similar construction. The 6AQ5 is a lower power 6V6 in a 7 pin package used originally in car radios, and the 6L6 is an upgraded 6V6 with higher voltage and higher current. You could make a choice based on cost or availability and loose nothing to quality in this group. All of these tubes are actually beam power tetrodes, not true pentodes.
I would also put the 6BQ6B / 6CU6 in the "very nice" category, but it takes a lot more drive voltage so an extra gain stage may be required. The 6BQ6 is a TV sweep tube and can be had for almost free. It is a great tube for guitar amps. I actually found that I preferred the 6BQ6 to the 6L6; the detail and articulation seemed slightly better. If you build a 6BQ6 amp, consider adding a switch to toggle between triode and pentode mode. Also, make sure to put a cage on the amp — you don't want a high voltage accident from a child sticking their finger on the plate cap.
The "great" category included EL3n, E80L, 6973. Note that all of the tubes in this category are true pentodes, not beam power tubes. RCA claimed that beam power technology sounded just as good as true pentodes, but I beg to differ."
The person carrying out the shootout is a violinist. I'm a bass/keyboard player and pro musician. Music used in my case, where I liked EL33/EL11 best was opera excerpts by Janacek and Wagner, jazz small groups, piano and vocals, and some Steely Dan tracks. I was looking for the most lifelike timbre on voices and acoustic instruments, together with overall transparency, detail and an "involving" sound which draws you in and makes you listen attentively.
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The above was another shootout of pentodes in triode. Rank order was
1. EL3n (predecessor of EL33)
2. E80L
3. 6973
Other tubes tried were as follows:
"The tubes fell into three categories: "yawn", "very nice", and "great". In the "yawn" category is the 807 tube. I can't recommend this tube in triode mode at all. The RCA manual doesn't recommend it either, and now I know why. It doesn't even work for background listening.
In the "very nice" category are all the 6V6 style beam power tubes. It was hard to find a distinct difference between the 6AQ5, 6V6, and 6L6. This is not surprising since they all have very similar construction. The 6AQ5 is a lower power 6V6 in a 7 pin package used originally in car radios, and the 6L6 is an upgraded 6V6 with higher voltage and higher current. You could make a choice based on cost or availability and loose nothing to quality in this group. All of these tubes are actually beam power tetrodes, not true pentodes.
I would also put the 6BQ6B / 6CU6 in the "very nice" category, but it takes a lot more drive voltage so an extra gain stage may be required. The 6BQ6 is a TV sweep tube and can be had for almost free. It is a great tube for guitar amps. I actually found that I preferred the 6BQ6 to the 6L6; the detail and articulation seemed slightly better. If you build a 6BQ6 amp, consider adding a switch to toggle between triode and pentode mode. Also, make sure to put a cage on the amp — you don't want a high voltage accident from a child sticking their finger on the plate cap.
The "great" category included EL3n, E80L, 6973. Note that all of the tubes in this category are true pentodes, not beam power tubes. RCA claimed that beam power technology sounded just as good as true pentodes, but I beg to differ."
The person carrying out the shootout is a violinist. I'm a bass/keyboard player and pro musician. Music used in my case, where I liked EL33/EL11 best was opera excerpts by Janacek and Wagner, jazz small groups, piano and vocals, and some Steely Dan tracks. I was looking for the most lifelike timbre on voices and acoustic instruments, together with overall transparency, detail and an "involving" sound which draws you in and makes you listen attentively.
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there is always a context to any opinions, and i am not so much bothered by anecdotes, they make me smile....🙂
Another option might be to use a beefier dual triode tube with a bit less mu like the 6BL7 since you don't need all the gain or the 6EM7 would be a good option as well and has been done before.
I don't really follow what you are referring to as "anecdotes" here......
Shootouts are all about "what does it sound like" aren't they? What else are they about?
I thought we were all into what our systems and components sound like.
Shootouts are all about "what does it sound like" aren't they? What else are they about?
I thought we were all into what our systems and components sound like.
Another option used here ( Problem using Hammond 126C IST ) is a 6J5 (or 7A4 Loctal) which is half of a 6SN7 with an IXYS constant current source.