Audiophile babble unless we understand what you mean by "night and day"; "lower resolution"; "upgrades"; "extreme upgrade"; "micro detail".
Also, what relevance the price of the speaker? How does that help define its performance characteristics?
Here's a strong suggestion. You are in the wrong place. There is a very good evidence bias in this forum - its what makes the forum valuable. There is a low tolerance for handwaving and golden ears.
You will find the confirmation you seek in other fora.
Alternatively, consider the possiblity that your findings from you single user tube rolling are good examples of expectation bias and that you may be misled by your brain's very strong preference for telling you what you expect to hear.
and you believe them? me i do not.....
to me it is not the getters nor the tube, but how you use the tube in a circuit that makes all the difference...
why not just tweak your circuit to the operating point that gives you the best results to your ears? i do it a lot in my amps....
did i said that you believed? i asked you if you believe....
brother, i assure you there are more things to learn about tubes and more exciting too than the shape of the getters...
my experience in a lot of other forums that i joined in is that people who talk about getters and brands and years are those who did not have actual experience in designing and building their own tube amps....
most ot the time they will be those who are end users who for lack of knowledge of tube circuits resort to swapping tubes with different getter shapes and brands and then proclaim their findings as if gospel truth...
i learned a lot about tubes since joining here in 2003, i am proud to say i learned a lot of good stuff....
brother, i assure you there are more things to learn about tubes and more exciting too than the shape of the getters...
my experience in a lot of other forums that i joined in is that people who talk about getters and brands and years are those who did not have actual experience in designing and building their own tube amps....
most ot the time they will be those who are end users who for lack of knowledge of tube circuits resort to swapping tubes with different getter shapes and brands and then proclaim their findings as if gospel truth...
i learned a lot about tubes since joining here in 2003, i am proud to say i learned a lot of good stuff....
EF86 circuit build and measurements comments. Has anyone built and measured EF86 circuit posted at tube-town dot net, taken from Svetlana Ap Note? I ask as the circuit in figure 3, EF86 connected as triode, claims a THD of better than 0.05% without feedback. My results did not line up. It may be possible the circuit is drawn incorrectly or has an incorrect value. Thought I'd see what others have successfully done and their results.
This thread looks pretty close to what I'm interested in, so thought I'd post here and provide additional details. Forgive me if there is a better thread, but I looked at a dozen and thought this most closest since I'm not interested in building a Mullard type amplifier where negative feedback from the output transformer is fed back to the EF86 pentode input stage to reduce THD. (Moderator, if you know of a better place, please post there - thanks)
Details:
First, I built the reference EF86 circuits published in the datasheets. I used both Pentode and Triode connections as outlined in Telefunken's 6267 EF806 datasheet, also illustrated in the EF86 datasheet figures/circuits contained in Philips, La Radiotechnique, and Mazda Belvu. Best as I can tell these circuits are all the same. I obtained datasheets from frank dot pocknet's tube database website.
The circuits were built using pentode setup of 100K Ra, 470K or 390K for Rg2, 1.5 K and 1K for Rk, with grid follower resistor of next stage - shunted by Keithley 2016 DMM/THD. Measurements taken at supply voltages of 100, 200 and 250 were in close agreement across 3 separate EF86 pentodes. The quoted THD of 5% with ~ 24.5 to 46 volts out, measured slightly better in my case: 4.2% (100V), 4.8% and 4.7% (200V and 250V respectively).
I performed tests in triode mode for Ra 47K, Rk 1.2K, and following grid stage resistor of 150K - shunted by Keithley 2016. These measurements too were a tad better at 3.0, 3.6% respectively for 200V and 250V.
In scanning various circuits, I noted use of the EF86 in several of the lower power Mullard Amps, along with use by Heathkit, and then, intriguingly, on tube-town dot nets site. I built the circuit exactly, with the exception of the 1000 uF Ck, which was set at 470 uF. The output was loaded at both 100K and at 750K - shunted with the Keithley 2016. My measurements were not anywhere near these. They were above 3% for operating voltages between 100V and 250V. Best THD was at the higher voltage, where THD measured 3.1%. Output voltage did not reach the levels noted. I did not notice any difference in using a 10uF, 100uF or 470uF electrolytic capacitor around Rk.
In comparing the Triode operation circuit as drawn by Svetlana Ap Note and that as illustrated in Telefunken, Philips, La Radiotechnique and Masda Belvu, it appears Svetlana are tying pin 1 ( Grid 2 -screen) pin 8 (Grid 3 - suppressor) and pin 6 (plate-anode) together. This is different than that by Telefunken et al, where pin 1 (Grid 2) is tied to pin 6 (Plate-anode) and pin 8 (Grid 3 - suppressor) is tied to pin 3 (cathode). Please let me know if you've had success with this circuit and modifications required to achieve a 40Vrms output while operating at 250V. I'm curious. Even at more modest output levels of 5 or 10Vrms, distortion was above 5%. Operating frequency of 1 KHz sinewave from DDS generator with THD measured by Keithley at < 0.035%.
Thanks!
This thread looks pretty close to what I'm interested in, so thought I'd post here and provide additional details. Forgive me if there is a better thread, but I looked at a dozen and thought this most closest since I'm not interested in building a Mullard type amplifier where negative feedback from the output transformer is fed back to the EF86 pentode input stage to reduce THD. (Moderator, if you know of a better place, please post there - thanks)
Details:
First, I built the reference EF86 circuits published in the datasheets. I used both Pentode and Triode connections as outlined in Telefunken's 6267 EF806 datasheet, also illustrated in the EF86 datasheet figures/circuits contained in Philips, La Radiotechnique, and Mazda Belvu. Best as I can tell these circuits are all the same. I obtained datasheets from frank dot pocknet's tube database website.
The circuits were built using pentode setup of 100K Ra, 470K or 390K for Rg2, 1.5 K and 1K for Rk, with grid follower resistor of next stage - shunted by Keithley 2016 DMM/THD. Measurements taken at supply voltages of 100, 200 and 250 were in close agreement across 3 separate EF86 pentodes. The quoted THD of 5% with ~ 24.5 to 46 volts out, measured slightly better in my case: 4.2% (100V), 4.8% and 4.7% (200V and 250V respectively).
I performed tests in triode mode for Ra 47K, Rk 1.2K, and following grid stage resistor of 150K - shunted by Keithley 2016. These measurements too were a tad better at 3.0, 3.6% respectively for 200V and 250V.
In scanning various circuits, I noted use of the EF86 in several of the lower power Mullard Amps, along with use by Heathkit, and then, intriguingly, on tube-town dot nets site. I built the circuit exactly, with the exception of the 1000 uF Ck, which was set at 470 uF. The output was loaded at both 100K and at 750K - shunted with the Keithley 2016. My measurements were not anywhere near these. They were above 3% for operating voltages between 100V and 250V. Best THD was at the higher voltage, where THD measured 3.1%. Output voltage did not reach the levels noted. I did not notice any difference in using a 10uF, 100uF or 470uF electrolytic capacitor around Rk.
In comparing the Triode operation circuit as drawn by Svetlana Ap Note and that as illustrated in Telefunken, Philips, La Radiotechnique and Masda Belvu, it appears Svetlana are tying pin 1 ( Grid 2 -screen) pin 8 (Grid 3 - suppressor) and pin 6 (plate-anode) together. This is different than that by Telefunken et al, where pin 1 (Grid 2) is tied to pin 6 (Plate-anode) and pin 8 (Grid 3 - suppressor) is tied to pin 3 (cathode). Please let me know if you've had success with this circuit and modifications required to achieve a 40Vrms output while operating at 250V. I'm curious. Even at more modest output levels of 5 or 10Vrms, distortion was above 5%. Operating frequency of 1 KHz sinewave from DDS generator with THD measured by Keithley at < 0.035%.
Thanks!
I never measured the distortion of a triode connected EF86 myself but Philips did (for Ra = 47K, Ra = 100K and Ra = 220K; see page 3):
EF86 Philips
Since the distortion is roughly proportional with output voltage, I deduce/estimate that according to Philips the distortion of the Svetlana circuit at Vb = 250 V and at 10 Vrms output would be about 1 %, which is way off (by a factor of 20) the 0.05 % claimed by Svetlana/Eric Barbour.
Philips measured with the suppressor grid tied to the cathode while the Svetlana circuit has the suppressor grid tied to the plate. But that certainly doesn't explain the big gap between the Philips and the Svetlana numbers.
So I never bought the Svetlana/Eric Barbour claim.
This is the Svetlana circuit and accompanying text:
Figure 3 shows the EF86 in triode connection. When this is done, the resulting triode is among the lowest-distortion electronic amplifying devices ever made. Typical second-harmonic distortion with 10v RMS output is on the order of 0.05%. This result is achieved without any negative feedback, so this circuit is an excellent choice for high-end audio design. The voltage gain will be about 25 in this connection, making it suitable for line stages.
EF86 Philips
Since the distortion is roughly proportional with output voltage, I deduce/estimate that according to Philips the distortion of the Svetlana circuit at Vb = 250 V and at 10 Vrms output would be about 1 %, which is way off (by a factor of 20) the 0.05 % claimed by Svetlana/Eric Barbour.
Philips measured with the suppressor grid tied to the cathode while the Svetlana circuit has the suppressor grid tied to the plate. But that certainly doesn't explain the big gap between the Philips and the Svetlana numbers.
So I never bought the Svetlana/Eric Barbour claim.
This is the Svetlana circuit and accompanying text:
Figure 3 shows the EF86 in triode connection. When this is done, the resulting triode is among the lowest-distortion electronic amplifying devices ever made. Typical second-harmonic distortion with 10v RMS output is on the order of 0.05%. This result is achieved without any negative feedback, so this circuit is an excellent choice for high-end audio design. The voltage gain will be about 25 in this connection, making it suitable for line stages.
Thank you. I've ordered a larger cap to perform the tests. In looking at the test circuits in the datasheets, what you say makes sense. I'm also looking at another groupdiy site that has information on noise measurements, but haven't heard back on THD. I appreciate your followup and will post my results once I get a chance to measure the Svetlana figure 3 circuit. Hopefully, the cap will arrive by this weekend.
Received the capacitors and built Svetlana circuit. The distortion, best measured across three EF86 was 0.87% with max at 1.05% (give or take on the last digit of the Keithley 2015 THD DMM). Indeed as PFL200 surmised, distortion levels increased with input voltage. Amplification worked out to 25.3 to 25.7 Vout/Vin across the three EF86 tubes between an input voltage signal sinewave at 1KHz of 100 mVrms up to an input level of 500 mVrms. I did not check higher input signal levels.