Caution: Detour Ahead
I've been on a similar journey with the 26 and then the 01a. The gyrator boards and RC regulators make it so easy to dial in the operating both for different DHTs. We live in good times (audio-wise at least).
My findings are similar to the ones reported above. The 01a has lower distortion and is more linear than the 26. The 26 is no slouch, of course, but the 01a sounds more cleaner, realistic, and can maintain composure at high levels. I am planning to build the 801a preamp along similar ideas, probably with a CCS load instead of a gyrator.
Here is the detour: I just finished a Burning Amp 3 Pre and it sounds as good, if not outright better, than the 01a. 😱
I had the boards and all the parts and a spare aluminium base so I went for the BA-3. The power supply is similar to the bride of zen, good old cap multiplier with zener reference. You can build this amp for peanuts, especially compared to the 01a with it's multiple transformers, chokes, tubes, and what nots.
I am a big Pass fan and of course I was expecting it to be good. But the 01a was so far ahead of what I'd heard before (and the 26 was in turn so far ahead of my existing setup, RME ADI-2 Pro) that I didn't think it could be beaten without similar efforts. Boy, am I wrong!
The BA-3 does everything the 01a does and better. The soundstage is even more deeper and more realistic (you are there). It has got me switching absolute polarity on songs. Where I had never heard the difference from a polarity switch before, it made a small change on the 01a, but the BA-3, a switch in polarity can result in night and day difference on some songs. On some others, it doesn't matter.
Anyway, I'm absolutely chuffed that you can get this level of performance with a simple, cheap, reliable, no unobtanium 100-year tube-based design. Thanks again to Papa!
These are all my children and I love them equally. I'm just happy at the number of options. Next on the list is the 801a-based pre and also a Luminaria-like pre. Let the madness continue.
I've been on a similar journey with the 26 and then the 01a. The gyrator boards and RC regulators make it so easy to dial in the operating both for different DHTs. We live in good times (audio-wise at least).
My findings are similar to the ones reported above. The 01a has lower distortion and is more linear than the 26. The 26 is no slouch, of course, but the 01a sounds more cleaner, realistic, and can maintain composure at high levels. I am planning to build the 801a preamp along similar ideas, probably with a CCS load instead of a gyrator.
Here is the detour: I just finished a Burning Amp 3 Pre and it sounds as good, if not outright better, than the 01a. 😱
I had the boards and all the parts and a spare aluminium base so I went for the BA-3. The power supply is similar to the bride of zen, good old cap multiplier with zener reference. You can build this amp for peanuts, especially compared to the 01a with it's multiple transformers, chokes, tubes, and what nots.
I am a big Pass fan and of course I was expecting it to be good. But the 01a was so far ahead of what I'd heard before (and the 26 was in turn so far ahead of my existing setup, RME ADI-2 Pro) that I didn't think it could be beaten without similar efforts. Boy, am I wrong!
The BA-3 does everything the 01a does and better. The soundstage is even more deeper and more realistic (you are there). It has got me switching absolute polarity on songs. Where I had never heard the difference from a polarity switch before, it made a small change on the 01a, but the BA-3, a switch in polarity can result in night and day difference on some songs. On some others, it doesn't matter.
Anyway, I'm absolutely chuffed that you can get this level of performance with a simple, cheap, reliable, no unobtanium 100-year tube-based design. Thanks again to Papa!
These are all my children and I love them equally. I'm just happy at the number of options. Next on the list is the 801a-based pre and also a Luminaria-like pre. Let the madness continue.
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This is interesting. Can you give me some more information. I don't care for soundstage - what I listen for is the timbre of acoustic instruments, voices, woodwind, pianos etc. The 01A is superb here. So does the BA-3 really match that degree of realism? And is it just as transparent, that see-through clarity of the best DHTs?
Timbre and tone of instruments is as good as the 01a, if not better. Decca recording of Ravel's Bolero is an excellent example of this. When it starts, there is a lot of woodwinds and horns, and it sounds more real and more live with the BA-3. It does this in a matter of fact kind of a way, rather than a dwelling on the beauty of the tone. What draws you in is the depth and realism of the soundstage, and the tone of the instruments as if you are hearing them on stage. Because it resolves and separates the instruments better, I find the tone to be better and less corrupted, particularly on loud passages.
Bear in mind that this is in combination with the F4 as the power amp. At a level of 2.8 V out from the BA-3, there are only second and third harmonics present, with the second adjusted to be slightly higher than the third. I could get the 2nd lower if I wanted using P3. The 01a has been adjusted to a similar mix of 2nd and third. I am using a source follower with the 01a to boost the current drive capability. Gyrator load, RC regs, separate heater trafo, AZ1 rectifier and two chokes in the B+ supply.
Bear in mind that this is in combination with the F4 as the power amp. At a level of 2.8 V out from the BA-3, there are only second and third harmonics present, with the second adjusted to be slightly higher than the third. I could get the 2nd lower if I wanted using P3. The 01a has been adjusted to a similar mix of 2nd and third. I am using a source follower with the 01a to boost the current drive capability. Gyrator load, RC regs, separate heater trafo, AZ1 rectifier and two chokes in the B+ supply.
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Hi Magz, hope you don't mind this little diversion. If you want me and Andy to buzz off, let us know and we'll continue this discussion somewhere else.
Andy, On the 01a, I set the operating point using the voltage pot on the gyrator board and the grid bias using SiC diodes. I'm at about -6V and 120V. Turning the pot allows you to find the optimum point. It is mostly just 2nd and third unless you start going too high and then the higher order harmonics show up. Mind you, this is at about 2.8 V out. I've seen that at higher output, you do get higher order harmonics (both with the 01a and the 26).
The BA-3 is a push-pull circuit, which means if you match devices and currents precisely, you can perfectly null out the 2nd harmonic, leaving only the 3rd harmonic. The pot, P3, allows you to unbalance it just a little bit and reintroduce the 2nd harmonic. Depending upon the harmonics of your main amp, you might prefer the sound of different proportions of 2nd and 3rd. The beauty of the design is that you can make that choice and alter the sound to your liking. I didn't match devices at all in my build because I just wanted to build it as fast as I could, and the design doesn't need matching (P1-P3 can cover for mismatches). I might do that now after hearing how good it is.
I had procured a largish batch of the Toshiba JFETs from other members here about 10 years ago. You can get replacements from Linear Systems, lsk170 and lsj74, from the diyaudio store. You can also get the BA-3 PCB and PS regulators from the store.
BA-3 Schematic:
Andy, On the 01a, I set the operating point using the voltage pot on the gyrator board and the grid bias using SiC diodes. I'm at about -6V and 120V. Turning the pot allows you to find the optimum point. It is mostly just 2nd and third unless you start going too high and then the higher order harmonics show up. Mind you, this is at about 2.8 V out. I've seen that at higher output, you do get higher order harmonics (both with the 01a and the 26).
The BA-3 is a push-pull circuit, which means if you match devices and currents precisely, you can perfectly null out the 2nd harmonic, leaving only the 3rd harmonic. The pot, P3, allows you to unbalance it just a little bit and reintroduce the 2nd harmonic. Depending upon the harmonics of your main amp, you might prefer the sound of different proportions of 2nd and 3rd. The beauty of the design is that you can make that choice and alter the sound to your liking. I didn't match devices at all in my build because I just wanted to build it as fast as I could, and the design doesn't need matching (P1-P3 can cover for mismatches). I might do that now after hearing how good it is.
I had procured a largish batch of the Toshiba JFETs from other members here about 10 years ago. You can get replacements from Linear Systems, lsk170 and lsj74, from the diyaudio store. You can also get the BA-3 PCB and PS regulators from the store.
BA-3 Schematic:
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One last question - what's the gain of the BA-3 circuit you posted? Will it drive a 300b SE output stage as it is? Or does it need an extra stage?
Excuse the OT, but this is very interesting and a direct comparison with the 01A, so quite relevant!
Excuse the OT, but this is very interesting and a direct comparison with the 01A, so quite relevant!
It might be possible. How much swing do you need for a 300B output stage? 70 Vpp?
Rail to rail is about 48 V. You can go with higher rails and cascode the JFETs, which are good to about 30 V. Nelson does talk about higher bias and voltage possibilities with the circuit. This is essentially a smaller scale F5.
You should ask in the giant BA-3 thread and you might get better answers from more knowledgeable people. I haven't built a 300B amp yet. Here is the thread:
The BA-3 as preamp build guide
Nelson's article:
https://www.firstwatt.com/pdf/art_ba_3.pdf
It is so easy to build, you could do it in an afternoon if you have all the parts. Certainly worth hearing how others with #26 and 01a preamps like this circuit.
Edit: Forgot to mention that the gain of the circuit is around 20 db. I haven't measured it exactly. But I know the 01a measures 18 db gain and the BA-3 is a little more than that. Probably between 2-4 db more.
Rail to rail is about 48 V. You can go with higher rails and cascode the JFETs, which are good to about 30 V. Nelson does talk about higher bias and voltage possibilities with the circuit. This is essentially a smaller scale F5.
You should ask in the giant BA-3 thread and you might get better answers from more knowledgeable people. I haven't built a 300B amp yet. Here is the thread:
The BA-3 as preamp build guide
Nelson's article:
https://www.firstwatt.com/pdf/art_ba_3.pdf
It is so easy to build, you could do it in an afternoon if you have all the parts. Certainly worth hearing how others with #26 and 01a preamps like this circuit.
Edit: Forgot to mention that the gain of the circuit is around 20 db. I haven't measured it exactly. But I know the 01a measures 18 db gain and the BA-3 is a little more than that. Probably between 2-4 db more.
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