Hey, Andy! If you fancy a tour of the earliest of indirectly-heated triodes to compare with the 27, here's some idle suggestions (no meshies I'm afraid):
the Marconi KL1 was one of the very first (1927) -
Link: KL1 advert OSRAM
Or, maybe even better - the first truly reliable indirectly heated. This one uses E. Yeoman Robinson's slip-coated heater assembly for higher gm.
It also appeared in year 1927.- the Met-Vick - COSMOS AC/R, with 4mA/V:
Link: COSMOS AC/R
There are little or no data sheets for COSMOS valves on the web, but I can begin fixing that with uploads from a Septmber 1928 data book I happily acquired for a price of a half-pint.
The refererence to "Short Path" is an indication of how close the grid approached the cathode sleeve, which was apperently only 1mm diameter.
The 4mA/V that resulted was notable for the tim, and a while afterward.
the Marconi KL1 was one of the very first (1927) -
Link: KL1 advert OSRAM
Or, maybe even better - the first truly reliable indirectly heated. This one uses E. Yeoman Robinson's slip-coated heater assembly for higher gm.
It also appeared in year 1927.- the Met-Vick - COSMOS AC/R, with 4mA/V:
Link: COSMOS AC/R
There are little or no data sheets for COSMOS valves on the web, but I can begin fixing that with uploads from a Septmber 1928 data book I happily acquired for a price of a half-pint.
The refererence to "Short Path" is an indication of how close the grid approached the cathode sleeve, which was apperently only 1mm diameter.
The 4mA/V that resulted was notable for the tim, and a while afterward.
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Hi Andy,
I am not moderating this thread.
I really don't want to lose the excellent content so far. We can play nice.
I find the history of tube development fascinating. Well worth sharing, I hope we can stay on that path.
I am not moderating this thread.
I really don't want to lose the excellent content so far. We can play nice.
I find the history of tube development fascinating. Well worth sharing, I hope we can stay on that path.
I ran into this putting a small stack of books on top of a bookshelf speaker, it did sound better. I opened the speaker up and installed butyl rubber dampening sheets, which in turn added a lot of weight to the speaker and heard this same improvement. This has me wondering it it was simply the weight doing this? Which then relates to this same dampening happening in a mesh vs solid plate tube.
@stephe Gilbert Briggs found out the same when he designed his Wharfedale Sand Filled Baffle 3 speakers.
http://www.troelsgravesen.dk/download/SFB-review.pdf
http://www.troelsgravesen.dk/download/SFB-review.pdf
Hopefully the elements in a tube are not moving. Not in a significant way.
For speaker boxes, you are probably both stiffening and damping those panels (bottom and top).
For speaker boxes, you are probably both stiffening and damping those panels (bottom and top).
A tube amplifier ends its circuit with a reactive device, the OPT, driven by a modulated high voltage, that gets stepped down to concentrated current to drive the speaker. A SS amplifier ends its circuit with a non-reactive transistor, modulating high current to drive the speaker directly. Most amplifier testers put an 8 ohm dummy load on the OPT and think they've characterized/measured that amp. How can that be? By castrating the interaction between the OPT secondary and a complex voice coil, crossover, ported box which is all over the place impedance wise, back EMF, all reacting with the OPT secondary, which is then reflected to the primary, to react further with the tube and PSU. This is the main difference between SS and tubes, the highly reactive and unpredictable and complex OPT secondary reacting with a speaker. Add to that there are thousands of speakers, all different. How do you measure that and tie those numbers back to how it sounds? Using dummy load I can make a .17 cent LM386 show a flat response, just as well as a $5,000 tube amp with a dummy load. Whats the point of the freq. response test then? Tube amp testing needs to be done electrically at the binding posts with speaker attached, as well as acoustically with a microphone.
''.....Tube amp testing needs to be done electrically at the binding posts with speaker attached, as well as acoustically with a microphone....''
Not necessary. Not realistic. Not practical. That would leave you to modify an amp with a flat FR to accomodate the speaker to get a flat FR. Are you going to do that for all your speakers you may collect? Fantasy. Just get decent speakers and perhaps an EQ if your ears are so inclined.
Not necessary. Not realistic. Not practical. That would leave you to modify an amp with a flat FR to accomodate the speaker to get a flat FR. Are you going to do that for all your speakers you may collect? Fantasy. Just get decent speakers and perhaps an EQ if your ears are so inclined.
Bringing speaker boxes into the conversation makes the SET vs PP vs SS much less of an issue (by the way, I use all 3)…then there is the room. So much for the “straight wire with gain” complete system.
Agreed RPMac, bringing speakers into it has no bearing. But, as stephe was drawing a parallel to tube elements I merely offered an idea on the speaker angle.
Hi Windcrest77,
Please read the thread. A complete explanation as to why we measure things the way we do has been detailed. this is an industry and does follow scientific method for experiments in general. 20to20 has it exactly right.
Hi Windcrest77,
Please read the thread. A complete explanation as to why we measure things the way we do has been detailed. this is an industry and does follow scientific method for experiments in general. 20to20 has it exactly right.
Both mass and dampening effect of butyl rubber.
A mesh has more dampening of a resonance compared to a flat surface. For some reason, I find that the tweaking with materials added to speakers works the same way as towards amplifiers and sources, pretty much everything in the chain. From pure logic, material tweaking cannot have an electric influence on the audio signals, so it should be purely acoustical. Although sser2 mentioned microphonics in some components, from such point of view, materials would have an influence on the electronic signals.